JPS6216031Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal synthesizer for input signals for transmission modulation.

Conventionally, mobile radio has a noise squelch method and a tone squelch method, and an example of the configuration of a tone squelch transmitter is shown in FIG. In the same figure, 1
is an original oscillator using a stable frequency oscillation source such as a crystal oscillator or a frequency synthesizer, and its oscillation frequency (o) is a (1/multiply) of the transmission frequency (i). 2 is a phase modulator, 3 and 4 are frequency multipliers with multipliers of m and n, respectively, 5 is a power amplifier, 6 is an antenna, 7 is a signal combiner, and 8 is an IDC.
(instantaneous deviation adjustment circuit), 9 is a microphone, 10 is a tone squelch oscillator, and 11 is a start switch thereof.

70 is a power input terminal, 71 is an audio frequency input terminal from the IDC, 81 is an input terminal for a tone squelch signal, R ₁ to _{R 4} are resistors, and C ₁ to C ₂ are capacitors.

In the above configuration, the audio of the microphone 9,
The output of the tone squelch oscillator 10 is sent to the signal synthesizer 7
After synthesizing it, it is modulated by the output phase modulator 2 of the original oscillator 1, and then m×n
The signal is multiplied twice and transmitted by the antenna 6 after power amplification. In this way, the tone squelch method shown in Figure 1 simultaneously sends out a voice signal and a signal unique to the communication system, and when the receiving side receives this signal, it connects the communication circuit to the speaker. . There are two different series of frequencies for tone scales, but 67Hz to 250.3Hz are commonly used.

On the other hand, the telephone voice band ranges from 300 to 3000Hz, so in order to separate this using a filter, the upper limit of the signal frequency and the lower limit of the voice band are close to each other, and since the frequency is low, the volume of the filter used for this is large. Therefore, it is not appropriate to incorporate it into mobile communication equipment, etc. Therefore, in the combiner 7 shown in FIG.
The IDC output is connected to the R ₁ and C ₁ arms, and the tone signal output is connected to the R ₂ and C ₂ arms, but the IDC output changes due to fluctuations in the load impedance of the R ₂ and C ₂ arms. Frequency deviation is strictly regulated under the Radio Law, and the level is set at an inner level so as not to exceed a predetermined level, resulting in a loss in terms of S/N.

Also, when making adjustments, the radio part and the signal part are assembled separately, but at this time, for convenience, a dummy resistor similar to the signal part is loaded, and after adjusting the level,
Although we are trying to combine the two, in radio equipment that meets strict standards, not only is it inevitable to set the modulation level, but strictly speaking, the impedance of the signal system has a negative effect on the frequency characteristics of the modulated signal. There was a problem in giving .

The present invention eliminates these drawbacks and makes it possible to set the level of the IDC-added audio signal and tone squelch signal without being affected by the impedance of the input signal source, making equipment adjustment easier and more reliable. It is an object of the present invention to provide a signal synthesizer that is easy to perform and that does not change the modulation characteristics of voice communication.

This will be explained below along with examples. FIG. 2 shows an embodiment of a signal synthesis circuit for tone scale signals according to the present invention.

In Fig. 2, symbols 1 to 6, 8 to 11, 7
0, 71, and 81 correspond to the same reference numerals in FIG. 1, respectively. 21 and 22 are voltage dividers for bias voltage that determine the modulator operating point, 72 is a coupling capacitor, 73 is an input regulator, 74 and 75 are voltage dividing resistors, 76 is a feedback resistor, 78 is a series resistor, 79 is a coupling capacitor, 82 is a coupling capacitor, 83
is an input regulator, 84, 85 are voltage dividing resistors, 86, 8
7 is a feedback resistor and capacitor, 88 is a series resistor, 89 is a coupling capacitor, and 90 and 91 are operational amplifiers.

Next, the operation of this embodiment will be explained. The audio input from the audio frequency input terminal 71 is amplified by a feedback amplifier 90, which is connected to a series resistor 78 and a coupling capacitor 79.
is applied to modulator 2 via. Since the modulator 2 gives a phase change to the input level, △F=nmm for a signal at a constant level.
The modulation frequency (m) gives phase modulation with a frequency characteristic of 6 dB/Oct. The modulation level is set using the variable resistor 73 in the connection state shown in FIG. Since the impedance of the operational amplifiers 90 and 91 when viewed from their respective output terminals a and b is approximately 0, the series resistor 78 is used as the resistor 21, 22, 88.
The voltage divided by the parallel resistance impeders becomes the input to the modulator 2.

The tone squelch signal is amplified by the operational amplifier 91, but the resistor 86 and capacitor 87 form an integrating circuit, and the modulation inputs 67 to 250 are -
Outputs with a level gradient of 6dB/octave. In this case, as in the case of the operational amplifier 90 described above, the signal is divided by the series resistor 88 and the parallel resistors 78, 21, and 22 and is applied to the modulator 2. giving the equivalent
FM modulation.

If the series resistors 78, 88 are selected to be sufficiently small compared to the resistors 21, 22 and the coupling capacitors 79, 89 are selected to have a sufficiently large capacitance, the series resistor 88 for the operational amplifier 90 and the resistor 78 for the operational amplifier 91 operate stably as a load impedance.

Further, since the tone squelch signal level is generally selected to be low compared to the voice, in this case, the series resistor 88 may be made larger than the resistor 78 to change the division ratio.

Note that this signal synthesis can be applied to a wide range of fields because multiple signals in the same frequency band can be synthesized without interference.

As explained above, according to the present invention, the impedance seen from the output side of the two amplifiers is almost 0.
Therefore, there are two signals: the audio signal and the tone squelch signal.
It is possible to combine two signals without using a filter or the like and without interference, and the level adjustment can be done independently for each signal, so the level can be set under a load condition assuming each other's impedance as in the conventional method. Since this is not necessary, adjustments can be made for each block and the desired characteristics can be obtained by simply connecting them. This allows the process to be divided into parts and performed independently when adjusting mass-produced equipment, thereby improving industrial efficiency. Great value.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram of a conventional radio signal synthesizer.
FIG. 2 is a wiring diagram of a signal synthesizer according to an embodiment of the present invention. 90, 91... operational amplifier, 78, 88... series resistor, 76, 86... resistor, 87... capacitor, 2... modulator.

Claims (1)

[Scope of utility model registration request] A first operational amplifier that is subjected to negative feedback and amplifies the tone squelch signal, a second operational amplifier that is subjected to negative feedback and amplifies the call voice signal, and a resistor, and synthesizes the outputs of the first and second operational amplifiers. and a phase modulator to which the synthesized output is added, and the amplifying section that amplifies the tone squelch signal has an integral characteristic, and has a constant frequency deviation with respect to the frequency of the tone squelch signal. A signal synthesizer characterized by providing equivalent FM modulation characteristics.