JPH08293748A - Automatic gain control device, mobile terminal, and automatic gain control method - Google Patents

Abstract

(57) [Summary] [Object] An automatic gain control device, a mobile terminal, and an automatic gain control method, which improve response characteristics of gain control and improve accuracy. A gain control amplifier 1 for amplifying a received signal, a feedforward gain control circuit (FF) 2 for outputting a control value based on a received signal level detection signal by a received signal level detection unit (RSSI) 4, and a gain control A feedback gain control circuit (FB) 3 that detects the amplified output signal of the amplifier 1 or the output signal of the demodulator 6 in the subsequent stage and outputs a control value is provided. A gain control value for controlling the gain of the gain control amplifier 1 is obtained by correcting with the control value by the control circuit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic gain control device applicable to a digital mobile communication system such as an automobile telephone or a mobile phone, a mobile terminal using the automatic gain control device and an automatic gain control method. In a digital mobile communication system, when a mobile terminal moves at high speed, Rayleigh fading occurs and the received signal level fluctuates significantly by about 50-60 dB. This causes problems such as demodulation error and increase in quantization error due to AD conversion. Therefore, there is a need for an automatic gain control device that compensates for changes in the received signal level.

[0002]

2. Description of the Related Art The conventional automatic gain control apparatus has the largest number of feedback gain control methods and also has an RSSI (Receive).
A feedforward gain control method using a d Signal Strength Indicator) is also known. 17A and 17B show a conventional example of a feedback gain control system, and FIG. 17C shows a conventional example of a feedforward gain control system. Further, the case where the received signal is an intermediate frequency signal, and after being amplified by the gain control amplifier, it is demodulated by the demodulator is shown.

FIG. 17A shows a gain control amplifier (GCA; Gain Controlled Amplifier) 101 for converting a received signal.
In addition to the above, the case where the signal is amplified and demodulated by the demodulator 102 is shown. The power of the output signal of the gain control amplifier 101 is detected by the power detection unit 103, and the difference from the desired power Pd is obtained by the adder 105. The difference is used as the control voltage of the gain control amplifier 101 via the low pass filter (LPF) 104, and the gain control amplifier 101 is controlled so that the difference between the power of the output signal and the desired power Pd becomes zero.

In FIG. 17B, the power of the demodulated signal demodulated by the demodulator 102 is detected by the power detection unit 103, the difference from the desired power Pd is calculated by the adder 105, and the difference is calculated. The gain control amplifier 101 is controlled via the low pass filter (LPF) 104 so that the difference between the power of the demodulated signal and the desired power Pd becomes zero as the control voltage of the gain control amplifier (GCA) 101.

In FIG. 17C, the received signal level detection section (RSSI) 106 detects the received signal level, and the received signal level detection signal is passed through a low pass filter (LPF) 107 to a gain control amplifier ( GCA) 1
The control voltage is set to 01, and the gain control amplifier 101 is controlled so that the gain is reduced when the received signal level is high, and conversely, the gain is increased when the received signal level is low. The signal is added to a circuit in the subsequent stage (not shown).

[0006]

In the conventional receiving section, one of the feedback gain control system and the feedforward gain control system is adopted to control the gain control amplifier 101. The former feedback gain control method has the advantage of high accuracy because it controls so that the deviation becomes zero. However, there is a problem that the response speed is slow because the control operation is not started unless the deviation occurs. Therefore, in the high speed Rayleigh fading channel, it is impossible to follow the fluctuation of the received signal level. Further, in the burst reception, there is a problem that it takes time for the initial pull-in.

In the latter feedforward gain control system, the received signal level detection signal (RSSI) is used, so that the fluctuation of the received signal can be immediately detected and the gain control can be performed. is there. However, in many cases, the received signal level detection signal (RSSI) characteristic and the automatic gain control (AGC) characteristic do not match each other, and there is a problem that it is difficult to perform highly accurate control.

18 and 19 show the carrier frequency 70.
The signal point of the quadrature detection output signal when the automatic modulation control (AGC) is performed by subjecting the unmodulated signal of 002625 MHz to fading at a frequency of 40 Hz, quadrature detection at a local frequency of 70 MHz, sampling with a 21 kHz clock signal, 17A and 17B show a feedback gain control system shown in FIGS. 17A and 17B and a feedforward gain control system shown in FIG. 17C.

That is, in the feedback gain control system, the response speed is slow, so that the signal points are dispersed in a wide range as shown in FIG. Further, since the feedforward gain control method has a high response speed, the dispersion of signal points is in a narrow range as compared with the feedback gain control method, as shown in FIG. In addition, ideally,
Although it is a point indicating the position of a predetermined signal point, since the level and phase of the demodulated output signal fluctuate due to the fact that gain control cannot be performed accurately by following the received signal level, in the case of quadrature detection. , The signal points are widely dispersed in a donut shape as shown in FIG. 18 or FIG.

Further, in the feedforward gain control method, since the received signal level detection characteristic and the control characteristic of the gain control amplifier 101 are not the same, it is difficult to control the gain with high accuracy. For example, FIG. 20 is an explanatory diagram of an RSSI (received signal level detection signal) characteristic and a GCA (gain control amplifier) characteristic. The curve a is an example of the GCA characteristic and the curve b is R.
An example of SSI characteristics is shown.

That is, the left vertical axis represents the received power Pr, the right vertical axis represents the GCA gain, and the horizontal axis represents the RSSI and AGC control values. For example, the GCA gain is represented by the curve a with respect to the AGC control value. Even if there is a linear relationship, the received power Pr and the RSSI have a non-linear relationship as shown by the curve b, so that there is a deviation between the RSSI characteristic and the GCA characteristic, and it is difficult to control the gain with high accuracy. Therefore, the control characteristic has a spread of signal points as shown in FIG. It is an object of the present invention to improve the response characteristics and enable highly accurate gain control by combining a feedforward gain control system and a feedback gain control system.

[0012]

The automatic gain control apparatus of the present invention will be described with reference to the first principle explanatory diagram of the present invention shown in FIG. 1. (1) A gain control amplifier 1 for amplifying a received signal
A feedforward gain control circuit (FF) 2 for controlling the gain of the gain control amplifier 1 according to the received signal level detection signal by the received signal level detection unit (RSSI) 4.
A feedback gain control circuit (FB) 3 for controlling the gain of the gain control amplifier 1 by detecting the amplified output signal of the gain control amplifier 1 or the output signal of the demodulator 6 in the subsequent stage and the like. The control value is corrected by the control value by the feedback gain control circuit 3 to control the gain of the gain control amplifier 1. Reference numeral 5 is an adder.

(2) A control value table for reading the gain control value of the gain control amplifier 1 based on the control values from the feedforward gain control circuit 2 and the feedback gain control circuit 3 can be provided.

Further, referring to a second principle explanatory diagram of the present invention of FIG. 2, (3) the feedforward gain control circuit (FF) 2 includes a reception signal level detecting section (RSSI) 4
The time constant of the moving average of the received signal level detection signal by
It is possible to provide a configuration that changes according to the moving speed information from the moving speed detection unit 7 and the like. Further, 1 is a gain control amplifier, 3 is a feedback gain control circuit (FB), 5 is an adder, and 6 is a demodulator.

The mobile terminal according to the present invention is (4) a mobile terminal having a transmitter and a receiver including a gain control amplifier for amplifying a received signal, the gain control according to a level detection signal of the received signal. A feedforward gain control circuit for controlling the gain of the amplifier; and a feedback gain control circuit for detecting the amplified output signal of the gain control amplifier or the output signal of the subsequent stage to control the gain of the gain control amplifier. The control unit is configured to correct the control value of the feedforward gain control circuit with the control value of the feedback gain control circuit and output the gain control value of the gain control amplifier.

The automatic gain control method of the present invention will be described with reference to the third principle explanatory diagram of the present invention of FIG.
Feedforward gain control using a reception signal level detection signal by a reception signal level detection unit (RSSI) 4 having a transmission unit 8 and a reception unit including a gain control amplifier 1 for amplifying a reception signal, a demodulator 6 and the like. In the automatic gain control method for controlling the gain control amplifier 1 by the gain control value obtained by correcting the control value by the circuit 2 by the control value by the feedback gain control circuit, a test signal in which the power is gradually changed from the transmitting unit 8 Is generated and the test signal is input to the receiving section, and a correction formula for correcting the control value by the feedforward gain control circuit 2 with the control value by the feedback gain control circuit is used. And the output power of the gain control amplifier 1 or the demodulation output power of the demodulator 6 by the power detection unit 9, and the output power and the desired power by the adder 11. Adjustment based on the error of the d processing section 1
0, etc., and the gain control amplifier 1 is controlled by correcting the control value during normal reception based on this correction formula.

(6) The reception signal level detection of the test signal in the receiving section is divided into a plurality of blocks according to the level of the signal, the correction formula is obtained for each block, and the reception signal level is detected during normal reception. The gain control value for controlling the gain control amplifier 1 can be corrected by using the block-based correction equation corresponding to the signal level.

(7) A control value that stores a gain control value obtained by correcting the control value by the feedforward gain control circuit 2 according to the power change of the test signal input to the receiving section with the control value by the feedback gain control circuit. A table can be formed and the gain control value of the gain control amplifier 1 at the time of normal reception can be read from the control value table.

(8) A control value that stores a gain control value obtained by correcting the control value by the feedforward gain control circuit 2 according to the power change of the test signal input to the receiving unit by the control value by the feedback gain control circuit. The gain control value can be updated by forming a table and minimizing the difference between the output power and the desired power Pd in the feedback gain control circuit.

(9) A gain control value obtained by inputting the test signal from the transmitting section to the receiving section and correcting the control value by the feedforward gain control circuit 2 according to this test signal by the control value by the feedback gain control circuit. Is stored in the control value table, and the gain control value stored in the control value table is updated so that the error between the output power and the desired power Pd in the feedback gain control circuit is minimized. When it becomes less than a predetermined threshold,
The control value table can be created by repeatedly changing the power of the test signal from the transmitter by one step.

[0021]

[Action]

(1) The gain of the gain control amplifier 1 is controlled by the control value by the feedforward gain control circuit 2 using the received signal level detection signal, and the feedback gain control circuit 3
The difference between the detection characteristic of the received signal level and the control characteristic of the gain control amplifier 1 is corrected by the control value according to. Therefore, the gain of the gain control amplifier 1 can be controlled by following the change in the received signal level at high speed, and can be controlled with high accuracy so as to obtain a desired output power.

(2) The gain control value of the gain control amplifier 1 stored in the control value table is controlled by the feedforward gain control circuit 2 and the feedback gain control circuit 3
The control value by the feed-forward gain control circuit 2 is read as an address, and the gain control value corresponding to the correction value by the control value by the feedback gain control circuit 3 can be read from the control value table. it can.

(3) Further, the feedforward gain control circuit 2 obtains a moving average for averaging the received signal level detection signals by a smoother or the like, and the movement of a mobile terminal or the like equipped with an automatic gain control device is performed. The time constant for obtaining the moving average is changed based on the speed information. For example, if the moving speed is low, increase the time constant to eliminate the influence of noise components on the control value. If the moving speed is high, decrease the time constant to follow the change in the received signal level. To obtain the control value.

(4) In a mobile terminal such as a car phone or a mobile phone having a transmitter and a receiver, the gain control amplifier 1 of the receiver is replaced with the feedforward gain control circuit 2.
And a feedback gain control circuit 3 are provided for control, and the control value by the feedforward gain control circuit 2 is
It is corrected by the control value by the feedback gain control circuit 3, so that even when fading occurs when the mobile terminal moves at high speed, the automatic gain control can be performed at high speed.

(5) Further, in the automatic gain control method for controlling the gain of the gain control amplifier 1, the transmitter 8 tests at the time of turning on the power to start the operation of each part including the gain control amplifier 1. A feedforward gain control circuit 2 using the received signal level detection signal is generated by generating a signal and inputting it to the receiving section, and changing the test signal power.
A correction equation for correcting the control value of 1 by the control value of the feedback gain control circuit is obtained. After obtaining this correction formula, the generation of the test signal from the transmitter 8 is stopped, and the signal from the transmitter 8 is switched so as not to be input to the receiver. Then, in a normal reception state, the gain control value of the gain control amplifier 1 is corrected and controlled according to the correction formula.

(6) When the reception signal level detection characteristic has non-linearity, or when the control characteristic of the gain control amplifier 1 has non-linearity, the reception signal level is divided into a plurality of blocks. , And the linearity characteristic, and obtain the above-mentioned correction formula for each block. And
In a normal reception state, highly accurate gain control can be performed by using the correction formula of the block corresponding to the level of the reception signal level detection signal.

(7) In addition, a test signal is generated from the transmission unit and input to the reception unit, the power of the test signal is changed, and the control value by the feedforward gain control circuit 2 is changed to the feedback gain control corresponding to the power. The gain control value corrected by the control value by the circuit is stored in the control value table. Then, during normal reception, the control value table is accessed by the control value by the feedforward gain control circuit 2 or including the gain value by the feedback gain control circuit to read and control the gain control value of the gain control amplifier 1.

(8) When forming the control value table,
The gain control value is updated so that the error between the output power of the gain control amplifier 1 or the output power of the demodulator or the like in the subsequent stage and the desired power Pd is minimized.

(9) When forming the control value table,
When the error between the output power and the desired power Pd in the feedback gain control circuit becomes less than or equal to a predetermined threshold value,
The gain control value at that time is stored, and the power of the test signal from the transmitter is changed by one step. Therefore, the gain control value of the gain control amplifier 1 can be stored in the control value table corresponding to the power for each step of the test signal.

[0030]

FIG. 4 is an explanatory diagram of a first embodiment of the present invention, showing an embodiment corresponding to the first principle explanatory diagram of the present invention of FIG. A corresponding gain control amplifier (GCA), 12 is a smoother corresponding to the feedforward gain control circuit 2, 13 is a feedback gain control circuit corresponding to the feedback gain control circuit 3, and 14 is a reception signal corresponding to the reception signal level detection unit 4. Level detection unit (RSSI), 15 is a control unit, 16 is a band pass filter (BPF), 17 and 19 are AD converters (A / D), 18 is a DA converter (D / A), and 20 is a quadrature detector. , 21, 23, 28 are multipliers, 22, 25, 2
7, 29 are adders, 24, 30 are delay circuits (T), 26
Is a power detector.

The received signal is input through the bandpass filter 16 and added to the gain control amplifier 11 and the received signal level detecting section 14. The detection signal of the reception signal level detected by the reception signal level detector 14 is converted into a digital signal by the AD converter 17 and added to the smoother 12 of the controller 15. The smoother 12 corresponding to the feedforward gain control circuit sets the time constant for obtaining the moving average to N, sets the received signal level detection signal to 1 / N in the multiplier 21, and delays one sampling time T by the delay circuit 24. The output value of the added adder 22 is added to [1- (1 /
N)] is added and added in the adder 22 to obtain an average value within the period of N, which is added to the adder 25 as a control value of the feedforward gain control circuit. In this case, if the value of N is increased, the noise removing effect is enhanced, and if the value of N is reduced, the control value can be output following the received signal level at high speed.

The gain control amplifier 11 amplifies the received signal, and in the case of a quadrature modulation signal such as QPSK, the quadrature detector 20 performs quadrature detection and the AD converter 19 converts it into a digital signal. The digital signal is applied to the power detection unit 26 of the feedback gain control circuit 13 of the control unit 15. The power detection unit 26 uses the quadrature components r _{I and} r _Q of the I phase and the Q phase obtained by the quadrature detection to calculate r _I
^The power is calculated by ² + r _Q ² , the difference from the desired power Pd is calculated by the adder 27, the step size μ is multiplied by the multiplier 28, and the integrator (low-pass filter) including the adder 29 and the delay circuit 30 is used. It is added to the adder 25 as a control value of the feedback gain control circuit 13 via the.

The adder 25 adds the control value by the smoother 12 (feedforward gain control circuit) so as to be corrected by the control value by the feedback gain control circuit 13 to obtain a gain control value. The gain control value is converted into an analog signal by the DA converter 18, and the gain of the gain control amplifier 11 is controlled as the control voltage of the gain control amplifier 11. Therefore, the gain control amplifier 11 is controlled by the control value of the feedforward gain control circuit to obtain a high-speed response characteristic, and the control value of the feedback gain control circuit 13 corrects the error from the desired power Pd to zero. Therefore, even in high-speed Rayleigh fading, it is possible to perform stable gain control with high-speed response, and there is an advantage that communication quality can be improved.

FIG. 5 is an explanatory view of the second embodiment of the present invention, showing an embodiment corresponding to the above-mentioned third principle explanatory drawing of the present invention of FIG. 3, in which a test signal from the transmitter is input. Then, the case where the correction formula of the gain control value of the gain control amplifier 11 is obtained is shown, and the same reference numerals as those in FIG. 4 indicate the same parts, 31 is a vectorization unit, 32 is a correction processing unit, 33 is an update processing unit, 34 Is an error converter, and 35 and 36 are multipliers.

The power detection unit 26 of the control unit 15 obtains the power of the quadrature detection output signal from the quadrature detector 20 by r _I ² + r _Q ² as described above, and calculates the desired power Pd at the adder 27. Of the gain control value is converted by the error conversion unit 34. This control error is multiplied by the vector obtained by the vectorization unit 31 in the multiplier 36, multiplied by the step size μ in the multiplier 35, and the update processing unit 33 calculates the coefficient of the correction formula in the correction processing unit 32. Update.

In the received signal level detector (RSSI) 14,
The received signal level detection signal by _(k)And the correction formula is y_(k)= C_{1 (k)}p_(k)+ C_{0 (k)} (1) and the error obtained by the adder 27 is the power error e
_{p (k)}Then, this power error e_{p (k)}Is e_{p (k)}= Α_(k)β_(k)−α_(k)β_{opt (k)} … (2) Note that α_(k)Is the attenuation value due to fading, β
_(k)Is the value amplified by the gain control amplifier, β_{opt (k)}Is the amplification value
Shows the optimum value of.

If γ is the amplification characteristic of the gain control amplifier 11 with respect to the gain control value, then ep _(k) = α _(k) γ [y _(k) ]-Pd (3) When this equation (3) is further modified, e _{p (k)} = β ^-1 _{opt (k)} Pdγ [y _(k) ]-Pd = γ ^-1 [y _{opt (k)} ] Pdγ [y _(k) ] −Pd (4) When both sides of this equation (4) are divided by Pd and transposed, γ ⁻¹ [y _{opt (k)} ] γ [y _(k) ] −1 = e _{p (k)} / Pd (5)

Since the amplification characteristic γ of the gain control amplifier 11 with respect to the gain control value is a power of 10 function, γ [y _(k) -y _{opt (k)} ] -1 = e _{p (k)} / Pd γ [Y _(k) -yopt _(k) ] = 1 + ep _(k) / Pd y _(k) -yopt _(k) = γ- ¹ [1 + ep _(k) / Pd] (6) You can

Γ ^{-1 in the} equation (6) is a logarithmic function,
The right side of (6) can be obtained by series expansion.
Therefore, the control error _{ey (k)} is _{ey (k)} = y _(k) -yopt _(k) (7). Further, the vectors C _(k) and X _(k) are _represented by C _(k) = [c _{0 (k)} , c _{1 (k)} ] ^t ... (8) X _(k) = [1, p _(k) ] ^t ... If (9), the coefficient of the correction equation can be sequentially obtained as C _(k) = C _(k-1) + μey _(k) X _(k) (10).

FIG. 6 is an explanatory diagram of the RSSI characteristic and the GCA characteristic. The gain characteristic of the gain control amplifier (GCA) is shown by a solid line a, and the received signal level detection (RSSI) characteristic is shown by a dotted line b, respectively. In the case where it can be expressed by an equation, a control error corresponding to the difference in the slope of the characteristic occurs, but the correction equation is the above equation (1) and the coefficient is (1
By obtaining by the equation (0), it is possible to correct the gain control value of the gain control amplifier 11 according to the correction equation at the time of normal reception, and to perform gain control with high speed response and high accuracy.

FIG. 7 is an explanatory view of the third embodiment of the present invention. The same reference numerals as those in FIG. 5 denote the same parts, 40 is a level identification section, 41a, 41b and 41c are vectorization sections, and 42 is a vectorization section.
a, 42b, 42c are correction processing units, 43a, 43b, 4
Reference numeral 3c indicates a selection unit controlled by the level identification unit 40. The vectorization units 41a, 41b, 41c correspond to the vectorization unit 31 in FIG. 5, and the correction processing units 42a, 42
b and 42c are the correction processing unit 32 and the update processing unit 33 of FIG.
And the multipliers 35 and 36.

As shown in the explanatory view of the RSSI characteristic and the GCA characteristic of FIG. 8, the GCA characteristic of the solid line a and the RS of the dotted line b are shown.
The SI characteristic is that the received power Pr is -30 dBm to -70 d.
1 in the range of Bm and in the range other than that
When the relationship of the following equation is satisfied, the received power Pr can be divided into 3 blocks to correct the gain control value.

That is, the level identifying section 40 identifies the magnitude of the received signal level detection signal, and the selecting sections 43a, 43
b and 43c are controlled, and the received signal level detection signal is ranged from 0 to 1.7 by the level identification section 40 (A).
And the range (B) of 1.7 to 4.3 and the range (C) of 4.3 to 6 are identified, and in the range (A), the vectorization unit is identified. 41a and correction processing unit 4
2a is selected to obtain the correction formula, and in the range (B),
The vectorization unit 41b and the correction processing unit 42b are selected to obtain the correction formula. In the range (C), the vectorization unit 41b is selected.
The correction equation is obtained by selecting c and the correction processing unit 42c.

Although it is possible to use a correction equation based on a quadratic equation, the use of a correction equation based on a linear equation simplifies the processing and speeds up the processing. Therefore,
As described above, when the characteristic cannot be expressed by the linear expression, the range expressed by the linear expression can be divided into blocks and divided. Further, as described above, after the correction formula corresponding to the block is obtained, the level identification unit 40 identifies the level of the received signal level detection signal even in the normal reception state, and the correction formula of the block corresponding to the level is identified. Thus, the gain control value of the gain control amplifier 11 can be corrected.

FIG. 9 is an explanatory view of the fourth embodiment of the present invention. The same reference numerals as those in FIG. 4 denote the same parts, 45 is a control value table, 46 is an adder, 13a is a feedback gain control circuit (FB). ) Is shown. In FIG. 4, the power detector 2
6 and the adder 27 are shown as the feedback gain control circuit 13. The feedforward gain control circuit 12 can be composed of a smoother.

The control value table 45 is the gain control amplifier 1
1 for storing a gain control value of 1, and a feedforward gain control circuit (FF) using a reception signal level detection signal by the reception signal level detection unit (RSSI) 14.
12 control values and feedback gain control circuit (FB)
The control value from 13a is added by the adder 46 to form the address of the control value table 45, and the gain control value is read out. Therefore, the control value by the feedforward gain control circuit 12 is set to the feedback gain control circuit 13
Since the gain control value corrected by the control value according to a is read out and the gain control value can be obtained at a higher speed than in the case where the correction processing is performed by the correction formula, high-speed response can be easily realized.

FIG. 10 is an explanatory view of the fifth embodiment of the present invention. The same reference numerals as those in FIG. 4 denote the same parts, 45 is a control value table, and 47 is a delay circuit (T). This embodiment shows an example of a method of creating the control value table 45, in which a test signal for gradually changing the power is input from a transmission unit (not shown), and a reception signal level detection unit (RS
SI) 14, the received signal level detection signal detected by
The digital signal is converted by the D converter (A / D) 17 and input to the control unit 15. Further, the test signal at that time is input to the gain control amplifier (GCA) 11 and amplified, and is quadrature detected by the quadrature detector 20 to be an AD converter (A / D).
It is converted into a digital signal by 19 and input to the control unit 15.

In the control unit 15, the power of the quadrature detection output signal is obtained by the power detection unit 26, the difference from the desired power Pd is obtained by the adder 27, the step size μ is multiplied by the multiplier 28, and the adder is added. It is output as a control value by the feedback gain control circuit through an integrator (low-pass filter) composed of 29 and a delay circuit (T) 30, and in addition to the control value table 45 and the DA converter (D / A) 18, D
The gain is controlled by using the analog signal converted by the A converter 18 as a control voltage of the gain control amplifier 11, and the adder 2
The feedback control is performed so that the output of No. 7, that is, the error power becomes zero.

The received signal level detection signal is used as the address of the control value table 45 via the delay circuit (T) 47, and the control value by the feedback gain control circuit one sampling time before is written. In this case, the control value table 4
By fixing the level of the test signal until the write operation to 5 is completed, the control value table 4 can be obtained without passing through the smoother as the feedforward gain control circuit.
It can be an address of 5. Control value table 45
By changing the power of the test signal every time after the writing operation to the control signal is finished, the control value by the feedback gain control circuit can be written in the address corresponding to the test signal power in the control value table 45.

The control value table 45 formed by the above-described method accesses the control value by the feedforward gain control circuit including the smoother or the like as an address at the time of normal reception, so that the feedback gain control circuit corresponding to the received signal level is obtained. It is possible to read out the control value by the control value read out from the control value table 45 and correct the control value by the feedforward gain control circuit.

FIG. 11 is an explanatory view of the sixth embodiment of the present invention, in which the same reference numerals as those in FIG.
Is a delay circuit (T), and 49 is an adder. In this embodiment, a gain control value corresponding to a received signal level detection signal is stored in advance in the control value table 45, a test signal is generated from a transmitter (not shown), and the test signal is input to the receiver to obtain an intermediate frequency signal. It is input to the gain control amplifier (GCA) 11 and the reception signal level detection unit (RSSI) 14 via the band pass filter (BPF) 16, and the amplified output signal of the gain control amplifier 11 is quadrature detected by the quadrature detector 20, An AD converter (A / D) 19 converts the signal into a digital signal.

The received signal level detector 14 detects the level of the test signal, the AD converter (A / D) 17 converts it into a digital signal, and the gain control value is read by adding it as an address signal of the control value table 45. , DA converter (D / A) 18 converts the signal into an analog signal and controls the gain as a control voltage for the gain control amplifier 11.

Further, the quadrature detection output signal is converted into a digital signal by the AD converter 19, the power is detected by the power detection unit 26 of the control unit 15, the difference from the desired power Pd is calculated by the adder 27, and the multiplier 28 is used. At step size μ
1 is added to the gain control amplifier 11 and the control value by the feedback gain control circuit by the adder 49.
The gain control value before the sampling time is added to obtain a corrected control value, and the address signal which is converted into a digital signal by the AD converter 17 and delayed by one sampling time by the delay circuit (T) 50 is a control value table. In addition to 45, a modified control value is written.

That is, the gain control value first written in the control value table 45 for the received signal level detection signal is sequentially corrected every time the level of the test signal is changed.
For example, if the error component is zero at a certain received signal level, the gain control value at that time is directly used as the control value table 45.
If the error is a negative value, the gain control value stored in advance is corrected in the control value table 45 by subtracting the control value corresponding to the error. It will be. Then, by changing the level of the test signal manually or automatically within a predetermined range, finally,
A control value table 45 storing desired gain control values can be formed.

FIG. 12 is an explanatory view of the seventh embodiment of the present invention, in which the same reference numerals as those in FIG. 11 designate the same parts, 51 is a correction processing section, 52 is an error power calculation section, 53 is a judgment section, and 54 is a section. Is an adder, 55 is a transmitter, and 56 is a test signal generator. The test signal generator 56 of the transmitter 55 is activated when the power is turned on, generates a test signal of a frequency that can be processed by the receiver, and inputs the test signal to the receiver. The receiver can be folded back at the radio frequency signal stage or folded back at the intermediate frequency signal stage.

The test signal generator 5 in this embodiment is also used.
6 has a configuration for changing the test signal level according to the control signal from the determination unit 53, and forms the control value table 45 by using the transmission function of the transmission unit 55 when performing a normal transmission operation. Only at times is it possible to have a circuit configuration that switches to a configuration for generating a test signal. Further, the control value table 45 and the correction processing unit 51 are similar to those in FIG.
This corresponds to the configuration including the control value table 45, the delay circuits 48 and 50, the adder 49, and the multiplier 28 in 1.

As described above, when the test signal generator 56 of the transmitter 55 is activated by turning on the power or the like, the test signal is input from the transmitter 55 to the receiver as shown in the schematic configuration, and the received signal is received. The received signal level is detected by the level detection unit 14, converted into a digital signal by the AD converter 17, and becomes an address signal of the control value table 45. Then, the correction processing unit 51 corrects the gain control value stored in the control value table 45 by repeating the procedure described for the embodiment of FIG.

Further, the difference between the power obtained by the power detector 26 by the adder 27 and the desired power Pd is calculated by the correction processor 51.
In addition to the error power calculation unit 52, the error power calculation unit 52 calculates the error power, and the adder 54 calculates the difference from the threshold Pt. It is determined whether or not, and when it is below, a control signal for changing the level of the test signal by one step is added to the test signal generator 56 of the transmitter 55.
Thereby, the test signal generator 56 changes the test signal level by one step, and the above-described operation is repeated to perform the correction process of the control value table 45.

In this embodiment, the error power is the threshold P.
Since the gain control value stored in the control value table 45 is modified and the test signal level is changed so as to be t or less,
The control value table 45 stores the gain control value with which the error becomes extremely small. Therefore, the gain control of the gain control amplifier 11 in the normal reception state can be performed at high speed and with high accuracy.

FIG. 13 is an explanatory view of an eighth embodiment of the present invention, showing an embodiment corresponding to the second principle explanatory view of the present invention of FIG. 2, and the same reference numerals as those in FIG. 4 indicate the same parts. . In the figure, reference numeral 60 is a time constant setting unit for setting the time constant N of the smoother 12. The configuration and operation of controlling the gain control amplifier 11 from the control unit 15 including the smoother (feedforward gain control circuit) 12 and the feedback gain control circuit 13 are the same as those shown in FIG. 4, and the duplicate description will be omitted. . Further, the time constant setting unit 60 sets the time constant N of the smoother 12 corresponding to the moving speed information v, and the multiplier 21
To the multiplier 23 and [1- (1 / N)] to the multiplier 23, respectively. Further, it has a function of decreasing the time constant N when the moving speed is high, and conversely setting the time constant N large when the moving speed is low.

That is, when the moving speed is high, the fading cycle becomes short, so that high-speed response is required. Therefore, the time constant N is made small, and the control value by the feedforward gain control circuit is made to follow the received signal level. If the moving speed is low, the fading cycle becomes long. Therefore, the time constant N is made large so that the noise component can be removed rather than making a fast response to the received signal level. Therefore, there is an advantage that the optimum values of the followability to fading and the noise removal can be obtained.

As the moving speed information v, the vehicle speed detection information can be used when applied to an automobile telephone. Alternatively, various moving speed detection configurations such as Doppler frequency detection and zone switching cycle detection can be applied.
Further, a control value table storing the gain control value of the gain control amplifier 11 is provided in the control unit 15, and the gain control value is read from the control value table by the address signal based on the received signal level detection signal and the moving speed information v. It is also possible to adopt a configuration of issuing.

FIG. 14 is a diagram for explaining the control characteristic according to the embodiment of the present invention, in which the feedback gain control system and the feedforward gain control system are combined so that the control value by the feedforward gain control circuit 12 is changed to the feedback gain control circuit 13. 19 shows the distribution of the signal points of the quadrature detection output signal in the first embodiment of the present invention, which is corrected by the control value according to FIG. It is obtained under the same conditions as the control characteristics by the method, and as is clear from comparing those characteristics with the characteristics of the embodiment of the present invention, according to the embodiment of the present invention, the distribution of signal points is narrow. Therefore, it can be seen that the fast response of gain control by the fast fading is improved.

FIG. 15 is an explanatory view of the control characteristics of the embodiment of the present invention, in which the signal points of the quadrature detection output signal in the case of using the control value table 45 of the fourth to seventh embodiments of the present invention. The distribution is shown and is obtained under the same conditions as in the control characteristic explanatory diagrams of FIGS. 18 and 19, and the control value table 45
It can be seen that by using, the responsiveness of gain control due to fast fading can be improved more than in the case shown in FIG.

FIG. 16 is an explanatory view of the ninth embodiment of the present invention, showing a main part of a mobile terminal. In the figure, 71 is a transmitting unit, 72 is a receiving unit, 73 is a transmission / reception control unit, 74 is a shared device, 75 is an antenna, 76 is a baseband unit, 77 is a transmitter, 78 is a receiver, and 79 is a liquid crystal. A display such as a panel, 80 is a dial key including various function keys, 81 is a gain control amplifier, 82 is a feedforward gain control circuit, 83 is a feedback gain control circuit,
Reference numeral 84 is a control unit.

The receiving section 72 includes a configuration for controlling the gain control amplifier 81 by a gain control value obtained by correcting the control value by the feedforward gain control circuit 82 with the control value by the feedback gain control circuit 83, and abruptly due to fading. The gain of the gain control amplifier 81 can be controlled in accordance with the varying received signal level. Therefore, even when high speed fading occurs when the mobile terminal moves at high speed, it can be processed as a stable received signal by the high speed response of the gain control.
In this case, the gain control amplifier 81 and the control section 84 can be applied to each of the above-described embodiments.

The path for generating the test signal from the transmitting unit 71 and inputting it to the receiving unit 72 may be switched so that the test signal is input from the transmitting unit 71 to the receiving unit 72 by controlling the duplexer 74, for example. Alternatively, the test signal may be switched from the intermediate frequency signal stage of the transmitter 71 to the intermediate frequency signal stage of the receiver 72 by the control of the transmission controller 73 or the like.

The present invention is not limited to the above-mentioned embodiment, but various additions and modifications can be made. The gain control amplifier 11 shows a case of amplifying an intermediate frequency signal. The present invention can be applied to the case of amplifying signals at other frequency stages, and the modulation method is not limited to quadrature modulation, and it is needless to say that various modulation methods can be applied. Further, the calculation function and the judgment function can be easily realized by utilizing the calculation processing function of the microprocessor. That is, the functions of the arithmetic processing part of the feedforward gain control circuit 12 and the feedback gain control circuit 13 can be realized by the microprocessor.

[0069]

As described above, according to the present invention, the gain control amplifier 1 corrects the control value by the feedforward gain control circuit 2 using the received signal level detection signal by the control value by the feedback gain control circuit 3. The gain control value is controlled by the feedforward gain control circuit 2, the gain is controlled by the control value of the feedforward gain control circuit 2 to follow the high-speed Rayleigh fading, and the gain is corrected by the control value of the feedback gain control circuit 3. There is an advantage that high-precision gain control is possible and stable reception processing is possible.

By providing a control value table storing gain control values, there is an advantage that the followability of gain control can be further improved. Further, the time constant for obtaining the moving average of the received signal level detection signal in the feedforward gain control circuit 2 is changed in accordance with the moving speed information, and it is possible to control to the optimum values of the followability to fading and the noise removal characteristic. There is. Further, it is applied to mobile terminals such as car telephones and mobile telephones, and there is an advantage that stable reception can be performed even against high speed Rayleigh fading when moving at high speed.

Further, by using the test signal from the transmitter, a correction formula for correcting the control value by the feedforward gain control circuit 2 is obtained, so that the deviation between the received signal level detection characteristic and the characteristic of the gain control amplifier 1 is corrected. Thus, the gain of the gain control amplifier 1 can be controlled. When using the control value table, the gain control value that minimizes the error power based on the test signal is stored in the control value table corresponding to the level of the test signal, and in the normal receiving state,
By controlling the gain of the gain control amplifier 1 using the control value table, high-speed response is obtained, and
There is an advantage that a highly accurate gain control can be performed.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the first principle of the present invention.

FIG. 2 is a diagram illustrating a second principle of the present invention.

FIG. 3 is a diagram illustrating a third principle of the present invention.

FIG. 4 is an explanatory diagram of the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of RSSI characteristics and GCA characteristics.

FIG. 7 is an explanatory diagram of a third embodiment of the present invention.

FIG. 8 is an explanatory diagram of RSSI characteristics and GCA characteristics.

FIG. 9 is an explanatory diagram of the fourth embodiment of the present invention.

FIG. 10 is an explanatory diagram of the fifth embodiment of the present invention.

FIG. 11 is an explanatory diagram of the sixth embodiment of the present invention.

FIG. 12 is an explanatory diagram of a seventh embodiment of the present invention.

FIG. 13 is an explanatory diagram of an eighth embodiment of the present invention.

FIG. 14 is a control characteristic explanatory diagram according to an embodiment of the present invention.

FIG. 15 is an explanatory diagram of control characteristics according to an embodiment of the present invention.

FIG. 16 is an explanatory diagram of the ninth embodiment of the present invention.

FIG. 17 is an explanatory diagram of a conventional example.

FIG. 18 is an explanatory diagram of control characteristics according to a conventional feedback gain control method.

FIG. 19 is an explanatory diagram of control characteristics according to a conventional feedforward gain control method.

FIG. 20 is an explanatory diagram of RSSI characteristics and GCA characteristics.

[Explanation of symbols]

 1 Gain Control Amplifier 2 Feed Forward Gain Control Circuit (FF) 3 Feedback Gain Control Circuit (FB) 4 Received Signal Level Detector (RSSI) 5 Adder 6 Demodulator

Claims (9)

[Claims] 1. A gain control amplifier for amplifying a received signal, a feedforward gain control circuit for controlling the gain of the gain control amplifier according to a received signal level detection signal, an amplified output signal of the gain control amplifier or an output signal of a subsequent stage. And a feedback gain control circuit for controlling the gain of the gain control amplifier, and a control value by the feedforward gain control circuit,
An automatic gain control device characterized in that the gain of the gain control amplifier is controlled by making a correction by a control value by the feedback gain control circuit. 2. A control value table for reading a gain control value of the gain control amplifier based on control values from the feedforward gain control circuit and the feedback gain control circuit is provided. The automatic gain control device described. 3. The automatic gain control according to claim 1, wherein the feedforward gain control circuit is configured to change a time average of a moving average of the received signal level detection signal according to moving speed information. apparatus. 4. A mobile terminal having a transmitter and a receiver including a gain control amplifier for amplifying a received signal, wherein a feedforward for controlling a gain of the gain control amplifier according to a level detection signal of the received signal. The control unit includes a gain control circuit and a feedback gain control circuit that controls the gain of the gain control amplifier by detecting an amplified output signal of the gain control amplifier or an output signal of a subsequent stage. A mobile terminal configured to correct a control value of a forward gain control circuit by a control value of the feedback gain control circuit and output a gain control value of the gain control amplifier. 5. A feedback gain control circuit for controlling a control value by a feedforward gain control circuit using a reception signal level detection signal, comprising a transmission unit and a reception unit including a gain control amplifier for amplifying a reception signal. In an automatic gain control method for controlling the gain control amplifier with a gain control value corrected by a value, a test signal whose power is gradually changed is generated from the transmission unit, and the test signal is input to the reception unit. A correction formula for correcting the control value by the feedforward gain control circuit with the control value by the feedback gain control circuit, the input power of the test signal to the receiving unit, and the output power of the gain control amplifier. , The difference between the output power and the desired power is obtained, and the control value at the time of normal reception is corrected based on the correction formula. Automatic gain control method and controlling the serial gain control amplifier. 6. The correction formula is obtained for each block by dividing into a plurality of blocks according to the level of a received signal level detection signal of the test signal in the receiving section, and the received signal is received at the time of normal reception. 6. The automatic gain control method according to claim 5, wherein the gain control value for controlling the gain control amplifier is corrected by using a correction formula corresponding to a block corresponding to the level of the level detection signal. 7. A control in which a gain control value stored by correcting a control value by the feedforward gain control circuit according to a power change of the test signal input to the receiving unit by a control value by the feedback gain control circuit is stored. A value table is formed, and the gain of the gain control amplifier is controlled by the gain control value read from the control value table based on the control value by the feedforward gain control circuit during normal reception. Item 6. The automatic gain control method according to item 5. 8. A control in which a gain control value obtained by correcting the control value by the feedforward gain control circuit according to the power change of the test signal input to the receiving unit by the control value by the feedback gain control circuit is stored. A value table is formed, and the gain control value stored in the control value table is updated so that the error between the output power and the desired power in the feedback gain control circuit is minimized. The automatic gain control method according to claim 7. 9. A gain control value obtained by inputting a test signal from the transmitter to the receiver and correcting a control value by the feedforward gain control circuit according to the test signal with a control value by the feedback gain control circuit. Is stored in the control value table, and the gain control value is updated so that the error component between the output power and the desired power in the feedback gain control circuit is minimized, and the error component is set to a preset threshold value. 9. The automatic gain control method according to claim 7, wherein the control value table is created by repeatedly changing the power of the test signal from the transmission unit by one step when the following occurs. .