JPH09116456A - Modulation / demodulation level switching method, variable band radio - Google Patents

Abstract

(57) Abstract: In a variable band FM radio, the influence of noise is reduced. SOLUTION: A modulation signal 12 from a control unit 100 is amplified by a modulation signal amplifier 16, and a VCO 7 as an FM modulator.
To the controller 10, after amplifying the output signal from the FM demodulator 9 by the demodulation signal amplifier 17,
Send to 0. The amplification factor of each amplifier 16 and 17 is the control signal 14
Thus, the signals 12 and 13 are controlled so as to always have the level at the time of wideband modulation data, and are not affected by noise here.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulation / demodulation level switching method for an FM type variable band wireless device and a variable band wireless device for switching the modulation / demodulation level by the method.

[0002]

2. Description of the Related Art One method of making more radio channels available in the same radio frequency band for effective use of radio frequencies is to reduce the use band of one channel. The attempt has been made with a wireless device or the like. In this case, if there is a system that can use both the conventional band and a narrower channel band, or a system that has a different available channel band for each region, there are two channel bands for a radio device. It is desirable to be able to use either.

FIG. 2 is a block diagram showing an example of the configuration of an FM radio device that can be used in either of these two channel bands, and is composed of a control unit 200 and a radio unit 201. The control unit 200 includes an ASP (Audio Signal Processor) 1 including an electronic volume 2, a control microcomputer 3, a memory 4 storing wideband modulation data 5 and narrowband modulation data 6, and the like, and a wireless unit. Reference numeral 201 includes a VCO 7 having a built-in modulation circuit 8, an FM demodulator 9 for a received wave converted to an intermediate frequency, a switching circuit 15 for switching an IF filter according to a wide band / narrow band signal, and the like.

In this radio, for example, wideband / channel is ± 5 kHz, narrowband channel is half ± 2.5 kHz.
Given the system deviation of z, the input voltage of the VCO 7 needs to be twice the voltage of the narrow band in the wide band. Therefore, even with the same modulation data in this radio,
The wide band modulation data 5 and the narrow band modulation data 6 having different amplitudes are prepared in the memory 4, and these are selected and read by the control microcomputer, and the electronic volume of the ASP 1 outputs to the VCO 7 as a signal level of a predetermined ratio. It was input 12 of. For demodulation, the FM demodulator 9
The amplitude of output 13 of FM is the system deviation of FM,
That is, depending on whether it is a wide band channel or a narrow band channel,
In the present case, in the wide band, the voltage amplitude becomes twice as wide as in the narrow band. Therefore, the electronic volume 2 is adjusted so that a signal having the same amplitude is output when using either channel.

Incidentally, in FIG. 2, the level adjustment at the time of transmission is prepared by previously preparing wide band and narrow band modulation data in a memory,
Although this has been dealt with by switching and using this, for example, only the wide band for the modulation data is stored in the memory, and the output amplitude from the electronic volume 2 may be changed according to the wide band or the narrow band. , A radio with a similar function is obtained.

[0006]

In the above-mentioned prior art, the input signal 12 to the VCO 7 and the FM demodulator output 13 are provided.
Will change for wideband and narrowband channels. For example, in the above FM example, the amplitude of the VCO7 input and the FM demodulator output when the system deviation is ± 2.5 MHz is half that when the system deviation is ± 5 MHz. When the signal level is lowered in this way, there is a problem in that the influence of pulsating noise from surrounding digital circuits increases, and S / N deterioration of the signal easily occurs. Further, it takes extra processing time to set the wideband and narrowband modulated data in the memory.

An object of the present invention is to provide a modulation / demodulation level switching method in which even if the channel bandwidth changes, the levels of the VCO modulation signal and the demodulator output signal do not change, and therefore S / N deterioration does not occur. It is to provide a variable band radio device that performs modulation / demodulation level switching by that method.

[0008]

According to the present invention, the level of a transmission modulation signal output from a control unit is switched to modulate a radio frequency with an FM modulator, and the signal level demodulated with an FM demodulator is switched. In the method of switching the modulation / demodulation level, the system deviation of the FM transmission / reception system is switched by outputting data to the control unit by
The input signal of the M modulator is amplified by the first amplifying means with variable amplification factor, and the output signal of the FM demodulator is amplified by the second amplifying means with variable amplification factor, and the first and second Disclosed is a method of switching modulation / demodulation levels, characterized in that the amplification factor of an amplification means is switched in accordance with the system deviation.

Further, the present invention is a variable band radio used in an FM transmission / reception system having a variable system deviation, wherein a modulated signal having a predetermined level and a control signal designating the system deviation are output, and a predetermined signal is output. Control unit having a function of receiving a demodulated signal of the level, first amplification means for amplifying the modulation signal whose amplification factor is controlled by the control signal, and an output signal of the first amplification means. According to the radio, an FM modulator for FM-modulating and transmitting a carrier, an FM demodulator for demodulating a received radio frequency signal, an amplifier for amplifying an output signal of the FM demodulator, and sending a demodulated signal to the controller. Second amplification means whose amplification factor is controlled by the control signal,
Disclosed is a radio device for variable bandwidth, which comprises:

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below by showing its embodiments. FIG. 1 is a block diagram showing an example of the configuration of a variable band wireless device according to the present invention, which is composed of a control unit 100 and a wireless unit 101. The configuration of the control unit 100 is shown in FIG.
The wireless unit 200 is similar to the wireless unit 200 shown in FIG.
Only the narrow band modulation data is stored. The radio unit 101 has a configuration in which a modulation signal amplifier 16 and a demodulation signal amplifier 17 are added to the configuration of the radio unit 201 in FIG. 2, and the amplification factors of these amplifiers 16 and 17 are both variable by the control signal 14 from the microcomputer 3. Controlled.

FIG. 3 shows a circuit configuration example of the modulation signal amplifier 16. The control signal 14 is a signal for switching the receiver IF filter according to the bandwidth of the channel to be used, which is a signal used conventionally,
It is assumed that a wide band channel is selected when the control signal 14 is "L" (low level) and a narrow band channel is selected when the control signal 14 is "H" (high level). Therefore, in the modulation signal amplifier 16 of FIG. 3, when the control signal 14 is “L”, the analog switch 22 is turned off, and the resistor 28 (resistance value R4) does not contribute to the feedback loop of the amplifier 21. Therefore, the gain G (L) of the modulation signal amplifier 16 at this time is

## EQU1 ## G (L) = 20 log (R3 / R1) [dB] The frequency characteristic of the amplifier 16 is

## EQU2 ## This is a high-pass filter characteristic in which the cutoff frequency is f _c = 1 / (2πR2C1). However, R1, R2, and R3 are resistors 25, 23, and 26, respectively.
C1 is the capacitance of the capacitor 24. The cutoff frequency f _c is set to a value smaller than the lowest frequency component of the modulated signal 12.

Next, when the control signal 14 is "H", the analog switch 22 is turned on, and the resistor 28 enters the feedback loop of the amplifier 21 in parallel with the resistor 26.
Therefore, the gain G (H) of the modulation signal amplifier 16 at this time
Is

## EQU3 ## G (H) = 20 {log (R3 / R1) + lo
g (R4 / (R4 + R3))}. Since the second term in this right side {} is a negative value,
The gain at this time is lower than G (L) in (Equation 1).
Therefore, the resistance values R1, R3 of the resistors 25, 26, 28,
By appropriately selecting R4, even if the signal level from the ASP1 is constant, it is possible to provide the modulation signal amplifier 16 with an amplification factor such that the system deviation at the time of using the wide band channel and the narrow band channel becomes an appropriate value. it can. For example, the system deviation is ± 5 kHz on the wideband channel and ± 2.5 kHz on the narrowband channel as described above.
In case of kHz, R1 = 10 kΩ, R3 = R4 = 33 kΩ
Then, from (Equation 1) (Equation 3)

## EQU4 ## G (L) = 10.4 [dB], G (H) = 4.
It becomes 4 [dB], and the gain G (L) in the wide band is 6 dB larger than that in the narrow band, and the modulation signal of double the amplitude is given to the VCO.

FIG. 4 shows an example of the circuit configuration of the demodulation signal amplifier 17, except that the resistor 23 and the capacitor 24 which give high-pass characteristics are removed and an inverter 31 is provided at the input portion of the control signal 14. The configuration is similar to that of FIG.
This circuit also operates in the same manner as in FIG. 3, and its gain is given by the same equations as in (Equation 1) and (Equation 3). However, in the demodulation signal amplifier 17, since the output level of the FM demodulator 9 in the wideband channel is higher than that in the narrowband channel, the gain in the narrowband channel is set to be larger than that in the wideband channel. Then, the output level of the demodulation signal amplifier 17 is made constant. Therefore, when the control signal 14 is inverted by the inverter 31 and the control signal 14 is "L" in the wide band channel, the control signal obtained by inverting the control signal 14 turns on the analog switch 32 and corresponds to (Equation 3). When a narrow band channel is provided, that is, when the control signal is "H", a low gain is applied, and the analog switch 32 is turned off by a control signal obtained by inverting this to give a higher gain corresponding to (Equation 1). . Each resistor 36, 3
The values of 7 and 38 may be determined in the same manner as in the case of the modulation signal amplifier of FIG. 3 according to the system deviation of wide band and narrow band channels.

As described above, according to the above-described embodiment, the control unit 100 and the radio unit 1 are used regardless of whether they are used as a wide band channel or a narrow band channel.
The delivery levels of the modulated signal 12 and the demodulated signal 13 between 01 and 01 can be constant. Therefore, this level
If you keep the same level as the conventional wideband signal,
High S always due to switching between wideband / narrowband channels
/ N can be held. Further, since only the wideband modulation data needs to be stored in the memory 4, the data setting processing time can be shortened.

[0015]

According to the present invention, the interface level of the modulation signal and the demodulation signal between the control unit and the radio unit can be kept constant, and the control unit and the radio unit can be switched when the system is switched as in the conventional case. It is possible to make it less likely to be affected by the outside due to the difference in the signal level of, and prevent the deterioration of S / N. Also, since the interface level of the modulation signal is constant, it is only necessary to have modulation data in one band, so there is no need to have data for both bands as in the past,
The memory capacity is half. At the same time, you can cut the time to set that data in half. Since this data setting increases as the number of channels increases, the effect also increases.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a variable band wireless device according to the present invention.

FIG. 2 is a block diagram showing an example of a conventional variable band radio device.

FIG. 3 is a block diagram showing an example of a variable band radio device having a modulation signal amplifier.

FIG. 4 is a block diagram showing an example of a variable band radio device having a demodulation signal amplifier.

[Explanation of symbols]

 3 Microcomputer 7 VCO 9 Demodulator 14 Control signal 16 Modulation signal amplifier 17 Demodulation signal amplifier 22, 35 Analog switch

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[Procedure amendment]

[Submission date] December 6, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

In this radio, for example, a wide band channel is ± 5 kHz, and a narrow band channel is half that of ± 2.5 kHz.
In case of system deviation, the input voltage of the VCO 7 needs to be twice the voltage of the narrow band in the wide band. Therefore, even with the same modulation data in this radio,
The wide band modulation data 5 and the narrow band modulation data 6 having different amplitudes are prepared in the memory 4, and these are selected and read by the control microcomputer, and the electronic volume of the ASP 1 outputs to the VCO 7 as a signal level of a predetermined ratio. It was input 12 of. For demodulation, the FM demodulator 9
The amplitude of output 13 of FM is the system deviation of FM,
That is, depending on whether it is a wide band channel or a narrow band channel,
In the present case, in the wide band, the voltage amplitude becomes twice as wide as in the narrow band. Therefore, the electronic volume 2 is adjusted so that a signal having the same amplitude is output when using either channel.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

In the above-mentioned prior art, the input signal 12 to the VCO 7 and the FM demodulator output 13 are provided.
Will change for wideband and narrowband channels. For example, in the above FM example, the amplitude of the VCO7 input and the FM demodulator output when the system deviation is ± 2.5 kHz is half that when the system deviation is ± 5 kHz. When the signal level is lowered in this way, there is a problem in that the influence of pulsating noise from surrounding digital circuits increases, and S / N deterioration of the signal easily occurs. Further, it takes extra processing time to set the wideband and narrowband modulated data in the memory.

Claims (3)

[Claims] 1. A level of a modulation signal for transmission output from a control unit is switched to modulate a radio frequency carrier with an FM modulator, and a level of a signal demodulated with an FM demodulator is switched to transfer data to the control unit. In a modulation / demodulation level switching method for switching the system deviation of an FM transmission / reception system so as to output, an input signal of the FM modulator is amplified by a first amplification means having a variable amplification factor, and the FM demodulation is performed. The output signal of the amplifier is amplified by the second amplification means having a variable amplification rate, and the amplification rates of the first and second amplification means are switched according to the system deviation. Switching method. 2. An F having a variable system deviation.
A variable band radio used in a transmission / reception system, comprising: a controller having a function of outputting a modulation signal having a predetermined level and a control signal designating the system deviation, and receiving a demodulation signal of a predetermined level; A first amplifying means for amplifying the modulated signal whose amplification factor is controlled by the control signal; and an FM modulating means for FM-modulating and transmitting a radio frequency carrier by an output signal of the first amplifying means. An FM demodulation means for demodulating the received radio frequency signal; and an amplification factor controlled by the control signal for amplifying an output signal of the FM demodulation means and sending the demodulation signal to the control section. A variable-band-division wireless device, comprising: 3. The variable band radio device according to claim 2, wherein the amplification factors of the first and second amplification means are variably controlled by analog switches which are turned on and off by the control means.