JPH07297784A - High-speed automatic gain control method for receiver circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a high-speed automatic gain control method for a receiving circuit that operates stably at high speed even with respect to interference waves. [Structure] An attenuator 2 connected in parallel with an RF amplifier 1 for amplifying a high-frequency signal is provided, and the attenuator 2 has a structure in which a plurality of attenuation elements are switched by switches 2-4 and 2-5. An RF level detector 14 for detecting the RF signal level is provided at the output of the attenuator 2 by switching between the amplifier 1 and each attenuation element, and the output signals of the RF level detector 14 and the IF level detector 12 are sent by the CPU 13. After processing, an appropriate switching position of the attenuator 2 is calculated and switching of the attenuator 2 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a PHP (personal
The present invention relates to a high-speed automatic gain control system for a receiving circuit such as a handy phone.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a configuration example of a conventional automatic gain control system for a receiving circuit. As shown in the figure, the conventional receiving circuit includes an RF amplifier 20, an RF filter 3, a mixer 4, a first local oscillator 5, an IF amplifier 6, an IF filter 7, a mixer 8, a second local oscillator 9, an IF amplifier 10, and I.
It is composed of an F filter 11 and an IF level detector 12. The RF amplifier 20 is a variable gain amplifier whose gain is controlled by a control signal. IF level detector 12
Is a diode 12-1 for rectifying the output signal and a resistor 1
2-2 and a capacitor 12-3.

The input signal amplified by the RF amplifier 20 is R
After passing through the F filter 3, the mixer 4 frequency-converts the output frequency of the first local oscillator 5 into a first intermediate frequency. Further, after being amplified by the IF amplifier 6, the signal is passed through the IF filter 7 and the second frequency by the output frequency of the second local oscillator 9 by the mixer 4.
After being frequency-converted to an intermediate frequency and amplified by the IF amplifier 10, it is output as an output signal via the IF filter 11.

In the above conventional automatic gain control method for a receiving circuit, an IF level detector 12 for detecting distortion is connected to the output of the second intermediate frequency signal, and the output signal is detected and rectified and converted into a DC voltage. Is fed back to the RF amplifier 20 and the amplification factor is controlled to an appropriate value in an analog manner, and the signal is received with high sensitivity and used in a range in which distortion does not occur.

[0005]

However, the conventional automatic gain control method has a problem that the output signal is rectified into a DC voltage and used for control, so that the time constant becomes long and high-speed operation cannot be performed. Furthermore, the dynamic range (automatic adjustment range) of the automatic gain control method may be narrow and stable reception may not be possible. The RF amplifier 20 amplifies including the interfering radio wave signal, and outputs the signal to the IF section (IF amplifier 6, I
The F filter 7, the mixer 8, the IF amplifier 10, the IF filter 11) amplifies a signal of a desired frequency, so
Conventional IF that detects the distortion level based on the output signal level
The level detector 12 alone has a problem that the automatic gain control (AGC) may not operate with respect to jamming radio waves. Further, there is a problem that stable automatic gain control (AGC) is difficult due to noise or the like because the analog control is performed.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a high-speed automatic gain control system for a receiving circuit which eliminates the above-mentioned problems and operates stably at a high speed even against an interfering radio wave. To aim.

[0007]

To solve the above problems, the present invention provides an R having an RF amplifier for amplifying a high frequency signal.
The F section, the IF section for frequency-converting and amplifying the output signal of the RF section into an intermediate frequency signal, and the IF level detector for detecting the level of the output signal of the IF section are provided. In the high-speed automatic gain control system of the receiving circuit for controlling the amplification factor of the RF amplifier and controlling the output signal of the IF unit so as not to be distorted, as shown in FIG.
The amplification factor of is fixed and an attenuator 2 is provided in parallel with the RF amplifier 1. The attenuator 2 is composed of a plurality of attenuation elements 2-
1, 2-2, 2-3 are configured to be switched by a switch that operates by a control signal, and the RF unit (RF amplifier 1, attenuator
2) RF level detector 14 for detecting the level of the RF signal, the output signal of the RF level detector 14 and the output signal of the IF level detector 12 are processed, and the output signals of the RF part and the IF part are Attenuator 2 of attenuator 2
A feature is that -1, 2, 2 and 2-3 are switched.

The amplification factor of the RF amplifier 1 and the attenuation element 2 of the attenuator 2 which is switched by the switches 2-4 and 2-5.
The difference between the attenuation values of -1, 2-2 and 2-3 is set to be equal to the difference between the operation levels of the IF level detector 12 and the RF level detector 14.

[0009]

The present invention is provided with the RF level detector 14 for detecting the output signal level of the RF unit from the RF unit and the IF level detector 12 for detecting the output signal level of the IF unit from the IF unit, and the detection signals of both of them are provided. Is processed to switch the attenuation elements 2-1, 2-2, 2-3 of the attenuator 2 to appropriate values. Therefore, the RF level detector 14 can detect the distortion due to the desired wave and the interfering radio wave, and the IF level detector 12 can detect the distortion of the desired wave to perform appropriate processing.

An RF level detector 14 is provided and the
Since the switching step value of switch 2 is set equal to the operating level difference between both detectors, an appropriate attenuator value can be instantly determined for the desired wave, and it also operates properly for jamming radio waves. Has a wide dynamic range (automatic adjustment range), and stable reception is always possible. Also, C
By using the PU 13, it is possible to reduce the time constants of both detectors and operate at high speed. Since the attenuator 2 operates stepwise in a logic manner, malfunction due to the influence of noise or the like is almost eliminated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a high-speed automatic gain control system of a receiving circuit of the present invention. As shown in the figure, the high-speed automatic gain control system of the present invention uses the conventional RF amplifier 1, attenuator 2, RF filter 3, mixer 4, and first
An IF for detecting the level at which the IF signal is distorted at the output side of the IF filter 11 in the receiving circuit including the local oscillator 5, the IF amplifier 6, the IF filter 7, the mixer 8, the second local oscillator 9, the IF amplifier 10 and the IF filter 11. Level detector 1
RF which connects 2 and detects the level at which the RF signal is distorted at the output side of the RF amplifier 1 which amplifies the RF signal (high frequency signal)
Connect the level detector 14 and output the output signal of each detector to CP.
This is a system in which processing is performed by a U (central processing unit) 13 and the attenuation amount of the attenuator 2 is switched to an appropriate value. The operation of FIG. 1 will be described below.

The RF level detector 14 is a diode 14-
1. The signal level (envelope) in which distortion occurs in the RF section (RF amplifier 1, attenuator 2, RF filter 3, mixer 4) is detected at high speed by the capacitor 14-3 and the IF level detector 12 is also a diode. 12-1, capacitor 12-3
In the IF section (IF amplifier 6, IF filter 7, mixer 8,
A signal level (envelope) in which distortion occurs in the IF amplifier 10 and the IF filter 11) is detected at high speed. RF like this
Both the level detector 14 and the IF level detector 12 do not have a time constant so that the signal level can be detected at high speed without using a resistor. Further, the RF level detector 14
Amplifies the detected signal level with the operational amplifier 14-4,
This is converted into a logic signal by the comparator 14-5, and the CPU
Input to 13. Similarly, the IF level detector 12 also converts the detected signal level into a logic signal by the comparator 12-5 via the operational amplifier 12-4, and inputs it to the CPU 13. The signal level increases as it goes to the latter stage, so IF
The section begins to distort earlier, and the IF level detector 12 operates at a lower input signal level than the RF level detector 14 as seen from the input of the RF section.

The attenuator 2 for adjusting the input signal has a step switching structure in which a plurality of attenuation elements are switched by the switch 2-4 and the switch 2-5, and the step value thereof is the IF value.
The detection level difference between the level detector 12 and the RF level detector 14 is made equal. The RF level detector 14 operates at -30 dB input signal level and the IF level detector 12 operates at -40
Considering the case of operating at the dB input signal level, the attenuator 2 is stepped up by 10 dB. CPU13
Switches the attenuator 2 according to the output signals of the IF level detector 12 and the RF level detector 14 so that the attenuation value becomes appropriate (described later).

As an example, an actual example in a PHP (Personal Handyphone) system will be described. FIG. 2 shows an example of a wireless frame format received by the receiving circuit (PHP) of the present invention. In the figure, SS and PR are preambles, which indicate synchronization bits, and a uni-word (UW), data, and error-check word (CR) which indicate IDs thereof.
Continue with C). In order to accurately receive the input signal, it is necessary to eliminate distortion in the RF section and the IF section by the time the uni-quad (UW) is received.
2. It is necessary to finish setting the attenuator 2 to an appropriate value within 20.8 μs of the preamble including the delay time of the RF level detector 14 and each filter circuit.

Since the RF level detector 14 detects distortion in the RF section, it detects the levels of the desired wave and the interfering radio wave, and the IF level detector 12 detects distortion in the IF section, so the level of the desired wave. Mainly detect. The RF level detector 14 responds in real time to the input signal because there is almost no delay in the filter circuit and the like, but the IF level detector 12 delays in responding by the delay of the IF filter 7, the IF filter 11, etc. . Time charts of automatic gain control (AGC) considering these are shown in FIGS.

FIG. 3 is a time chart showing an example of RF level and IF level detection and an attenuator switching operation when the input signal level is higher than the operation level (-40 dB) of the IF level detector 12 by 0 to 10 dB. In the initial state, the switches 2-4 and 2-5 of the attenuator 2 are located at the input / output ends of the RF amplifier 1. The input signal is input to the RF amplifier 1 at time t1 and amplified to the RF level a1.
In the IF section, the signal is delayed by the IF filter 7, the IF filter 11 and the like and becomes the IF level b1 at the time t2 and is output.

In this case, the RF level detector 14 does not operate because the signal level is low, and the IF level detector 12 does not operate.
Level b1 is detected, detector operating time (1.5 μs)
After that, it operates at time t3 and outputs the IF level detector output d1. The CPU 13 issues a command to the attenuator 2, and the attenuator 2 completes the switching operation at time t4 after an operating time of 4.2 μs, and the RF level a1 becomes 10 dB at the RF level a2.
Go down. Then, in the IF section, the signal level is lowered by 10 dB from the IF level b1 to the IF level b2 at time t5 after a delay due to the IF filter 7 and the IF filter 11.

FIG. 4 is a time chart showing an example of RF level and IF level detection and an attenuator switching operation when the input signal level is in the range of 10 dB or more and 20 dB or less higher than the operation level (-40 dB) of the IF level detector 12. It is In the initial state, the switches 2-4 and 2-5 of the attenuator 2 are in the position of the RF amplifier 1. The input signal is input to the RF amplifier 1 at time t1 and amplified to the RF level a1. IF filter 7 and IF filter 1 in the IF section
After a delay of 1 or the like, the IF level b1 is output at time t4 and the signal is output.

In this case, the RF level detector 14 outputs the signal c1 at time t2 after the delay time of 2.5 μs between the circuit and the detector.
Is output, the CPU 13 issues a command to the attenuator 2,
The attenuator 2 switches the switch 2-4 and the switch 2-5 at time t3, and the RF level a1 changes to the RF level a2 by 10
dB down. Since the input level is lowered, the IF level b1 is also delayed by 10 dB to the IF level b2.

The IF level detector 12 detects the IF level b1, and after the operating time (1.5 μs) of the detector, the time t5.
And outputs the IF level detector output d1. CPU
13 issues a command to the attenuator 2, and the attenuator 2 completes the switching operation at time t6 after an operating time of 4.2 μs,
The RF level a2 is 10 dB lower than the RF level a3. Then, in the IF section, after a delay time of the IF filter 7, the IF filter 11, etc., the level drops from the IF level b2 to the IF level b3 by 10 dB at time t7.

FIG. 5 is a time chart showing an example of RF level and IF level detection and attenuator switching operation when the input signal level is higher than the operation level (-40 dB) of the IF level detector 12 by more than 20 dB and lower than 30 dB. is there. In the initial state, the switches 2-4 and 2-5 of the attenuator 2 are in the position of the RF amplifier 1. The input signal is input to the RF amplifier 1 at time t1 and amplified to the RF level a1. In the IF section, IF filter 7 and IF filter 11
After that, the IF level b1 is output at time t5 after a delay.

In this case, the RF level detector 14 outputs the output c1 at time t2 after a delay time of 2.5 μs between the circuit and the detector.
Is output, the CPU 13 issues a command to the attenuator 2,
At time t3, the attenuator 2 operates and the RF level a1 drops by 10 dB to the RF level a2. Since the input level is lowered, the IF level b1 is delayed and the IF level b2 is increased by 10 dB.
Go down.

Further, the RF level a2 is a level detected by the RF level detector 14, and after the delay time of the circuit and the detector, the RF level detector 14 outputs the output c2 at time t4, and the CPU 13 attenuates. A command is issued to the controller 2, the attenuator 2 operates at time t6, and the RF level a2 becomes R.
It drops to F level a3 by 10 dB. Since the input level is lowered, the IF level b2 is also delayed by 10 dB to the IF level b3.

The IF level detector 12 detects the IF level b1, and after the operating time (1.5 μs) of the detector, the time t7.
And outputs the IF level detector output d1. CPU
13 issues a command to the attenuator 2, and the attenuator 2 completes the switching operation at time t8 after an operating time of 4.2 μs,
The RF level a3 is 10 dB lower than the RF level a4. Subsequently, in the IF section, after a delay time of the IF filter 7, the IF filter 11, etc., the level drops from the IF level b3 to the IF level b4 by 10 dB at time t9. In each of the above examples, the attenuator 2 completes its operation within 10.7 μs from the start of reception, and the switching is completed within the preamble time of the wireless frame format (FIG. 2).

3 to 5 describe the case where the input level of the desired wave is high, the case where the interference wave is large and the desired wave is small (the RF level detector 14 operates and the IF level detector 12 operates). No)) is processed similarly. This is performed in order to prevent the occurrence of data error due to distortion or the like because the input signal is phase-modulated (π / 4DQPSK). Further, in this case, the data error caused by the distortion due to the jamming radio wave is compared with the data error caused by the automatic gain control, and the CPU 13 selects the attenuation value to the one having less error.

As described above, in a receiver (radio receiver or the like) whose input signal level cannot be predicted, when a strong signal which causes signal distortion is received by the receiver, necessary data is received. Prior to this, appropriate automatic gain control is performed at high speed so that the receiving circuit operates without distortion, and data can be stably received. RF level detector 14 with CPU 13
Since the output of the IF level detector 12 and the output of the IF level detector 12 are processed, it is possible to reduce the time constant of both detectors and operate at high speed.

[0027]

As described in detail above, according to the present invention, the following excellent effects are expected. (1) This system is provided with an RF level detector that detects the level of the output signal of the RF unit from the RF unit and an IF level detector that detects the output signal level of the IF unit and the IF unit, and processes both detection signals. , The attenuation element of the attenuator is switched to an appropriate value, so that the RF detector can detect the distortion caused by the desired wave and the interfering radio wave and the IF level detector can detect the distortion of the desired wave and can perform an appropriate gain control.

(2) Since the RF level detector is provided and the attenuation value of the attenuation element switched by the switch of the attenuator is made equal to the operation level difference between the RF level detector and the IF level detector, an appropriate gain is obtained at high speed. Control is possible, the dynamic range (automatic adjustment range) of the automatic gain control method is wide, and stable reception is always possible.

(3) Since the attenuator operates in a stepwise logic manner, malfunction due to the influence of noise or the like is almost eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a high-speed automatic gain control system of a receiving circuit of the present invention.

FIG. 2 is a diagram showing an example of a wireless frame format received by the receiving circuit of the present invention.

FIG. 3 is a time chart showing an example of RF level and IF level detection and attenuator switching operation of this system.

FIG. 4 is a time chart showing an example of RF level and IF level detection and attenuator switching operation of this system.

FIG. 5 is a time chart showing an example of RF level and IF level detection and attenuator switching operation of this system.

FIG. 6 is a block diagram showing a configuration example of an automatic gain control system of a conventional receiving circuit.

[Explanation of symbols]

 1 RF Amplifier 2 Attenuator 2-4 Switch 2-5 Switch 3 RF Filter 4 Mixer 5 1st Local Oscillator 6 IF Amplifier 7 IF Filter 8 Mixer 9 2nd Local Oscillator 10 IF Amplifier 11 IF Filter 12 IF Level Detector 13 CPU (Central Processing Unit) 14 RF level detector

Claims (2)

[Claims] 1. An RF unit having an RF amplifier for amplifying a high frequency signal, an IF unit for frequency-converting and amplifying an output signal of the RF unit into an intermediate frequency signal, and an IF level detection for detecting a level of an output signal of the IF unit. And controlling the amplification factor of the RF amplifier by the output of the IF level detector,
In a high-speed automatic gain control system of a receiving circuit for controlling the output signal of the unit so as not to be distorted, the amplification factor of the RF amplifier is fixed, an attenuator is provided in parallel with the RF amplifier, and the attenuator is a plurality of An attenuator is configured to be switched by a switch that operates with a control signal, an RF level detector that detects the level of an RF signal from the RF unit, an output signal of the RF level detector, and an output of the IF level detector. A high-speed automatic gain control system for a receiving circuit, which processes a signal and switches an attenuator of an attenuator so that the output signals of the RF unit and the IF unit are not denied. 2. The difference between the amplification factor of the RF amplifier and the attenuation value of the attenuation element of the attenuator switched by the switch is the IF.
2. The high-speed automatic gain control system for a receiving circuit according to claim 1, wherein the level difference is set to be equal to the operation level difference between the level detector and the RF level detector.