JPS6231865B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmitting/receiving device that performs wireless communication using a press-talk method.

A communication method in which the same frequency is used for transmission and reception, the communication device is always in the receiving state, and the communication device is switched to the transmitting state only when transmitting is called a press-talk method.

Conventionally, in a press-talk type transmitting/receiving device, a frequency source for transmission or a local oscillation frequency source for reception has been obtained using a crystal oscillation multiplication method or a phase control method.

FIG. 1 shows a transmitting/receiving circuit in the crystal oscillation multiplication method which is mainly used. This circuit has two independent circuit parts,
A voltage-controlled crystal oscillator 1 for transmission or a crystal oscillator 2 for reception is used as a reference oscillator. The reference oscillators 1 and 2 include first multiplier amplifiers 3 and 4 that multiply and amplify the oscillation frequency, first wave generators 5 and 6 that remove spurious components from signals output from the multiplier amplifiers 3 and 4, and a first second multiplier amplifiers 7, 8 for further multiplying and amplifying the signals output from the second multipliers 5, 6; and a second multiplier 9, for removing spurious components from the signals output from the second multipliers 7, 8. A series circuit consisting of 10 is connected. And the output terminal 1 of the second wave transmitter 9, 10
1 and 12, a transmitting frequency source or a receiving local oscillation frequency source in the 150 MHz band, for example, is obtained.

As described above, in the crystal oscillation multiplication method, it is essential to provide a multiplication stage of at least 4 to 9 times in order to obtain the required degree of modulation. For this reason, two stages of multipliers are required for each of the transmitting and receiving circuit sections, and a frequency converter is required for each. Furthermore, since the multiplier requires a large number of tuning circuits, the entire circuit becomes complex and the number of adjustment points increases. Furthermore, since the circuit part is entirely composed of high-frequency analog circuits, IC
Therefore, it is difficult to miniaturize the circuit device. In addition, it is necessary to use a waver with high selectivity in order to guarantee the spurious characteristics of the circuit, which has the disadvantage that the device is expensive.

On the other hand, in transmitter/receiver circuits using the phase control method, there are types that have independent phase control loops for transmission and reception, and ones that use the output of one phase control loop to generate frequencies using separate frequency sources. There was also a type that shifted and obtained other frequency sources.

FIG. 2 shows the former circuit. A phase-locked loop that obtains a frequency source for transmission from the output terminal 13 is composed of a reference oscillator 14 , a phase comparator 15 , a loop filter 16 , a voltage-controlled oscillator 17 , and a frequency divider 18 . In this circuit part, the oscillation frequency of the voltage controlled oscillator 17 is divided by the frequency divider 1.
A phase comparator 15 compares the output frequency-divided by 8 and the output of a reference oscillator 14 that oscillates a reference frequency, and based on the comparison result, a voltage-controlled oscillator 17
control the oscillation frequency. loop filter 16
is provided for loop stabilization. The phase-locked loop that obtains the local oscillation frequency source for reception from the output terminal 19 also includes a reference oscillator 20 and a phase comparator 2.
1, a loop filter 22, a voltage controlled oscillator 23, and a frequency divider 24, and the circuit operation is the same as that of the transmitting circuit.

This circuit system is often used in CB transceivers, for example, but since it has two phase-locked loops,
The drawback was that there were a large number of parts and the price was high. Furthermore, there is a problem of operating limits of the variable frequency divider, making it difficult to directly oscillate the required frequency using the voltage controlled oscillator. Therefore, in practice, a method has been adopted in which a voltage controlled oscillator is used to oscillate once at a low frequency, and then this is multiplied to obtain the desired frequency. In this case, the same drawback as the crystal oscillation multiplication method described above occurred.

Furthermore, in the method of obtaining another frequency source by frequency-shifting the output of one phase-locked loop, a new problem has arisen in dealing with spurious signals that occur during frequency shifting.

Note that in the phase control method, it is theoretically possible to provide a circuit with only one set of a reference oscillator and a voltage-controlled oscillator, and to use this for both transmission and reception. However, if we try to design such a circuit using the press-to-talk communication method where the transmitting and receiving frequencies are the same, the oscillation frequency of the voltage controlled oscillator must differ by the intermediate frequency between transmitting and receiving, which places restrictions on the loop characteristics. cannot accomplish much.
As mentioned above, in the conventional example, a circuit configuration including L and C such as a final stage filter, a transmitter, etc. is essential, and the disadvantage is that the configuration of the device becomes larger and more complicated. On the other hand, even if the conventional examples are combined, when trying to simplify the configuration by sharing the configuration for reception and transmission, due to the restriction of loop characteristics,
This cannot result in an appropriate configuration.

The present invention was made in order to solve the above-mentioned problems that existed in press-talk type transmitting and receiving devices, and provides a transmitting and receiving device that can eliminate the multiplier and the final stage waver and also simplify the circuit. The purpose is to provide.

The present invention achieves this objective by adopting a direct frequency division phase control loop method and by using a frequency divider and a phase comparator for both transmission and reception.

The present invention will be explained in detail with reference to Examples below.

Figure 3 shows an example of a circuit for a 150 MHz band vehicle-mounted mobile radio. When the transmitting/receiving device is switched to the transmitting state as shown in the figure by the interlocking changeover switches 31 and 32, a modulation input is supplied to the transmitting reference oscillator 33. Reference oscillator 3
3 consists of a voltage-controlled crystal oscillator with a center frequency of about 38 MHz, and performs frequency modulation according to the modulation input.

The FM modulated signal thus obtained is supplied to the phase comparator 34 through the changeover switch 31.
The phase comparator 34 is a voltage controlled oscillator 35 for transmission.
A part of the signal output from the FM modulation signal is input to the frequency divider 36, and the phase of the signal obtained as a result of frequency division by 4 is compared with the FM modulation signal. The error voltage obtained as a result is then supplied to the voltage controlled oscillator 35 via the loop filter 37 and the changeover switch 32 to perform phase synchronization. As a result, a transmission signal in the 150 MHz band is obtained from the output terminal 38 of the voltage controlled oscillator 35. This transmission signal is amplified by a power amplifier (not shown) and then radiated into space from a transmission antenna (also not shown).

Next, when the transmitting/receiving device is in the receiving state, that is, at all times, the contacts of the changeover switches 31 and 32 are switched to the opposite side as shown. A part of the signal output from the output terminal 40 of the voltage controlled oscillator 39 for reception to a reception mixer circuit (not shown) is supplied to the frequency divider 36, where the frequency is similarly divided by four. The resulting output signal is sent to the phase comparator 34.
A phase comparison is performed between the received signal and the signal supplied from the receiving reference oscillator 41 to the phase comparator 34 via the changeover switch 31.

As a result, if the reference oscillator 41 oscillates at a frequency of 37.50+5.35MHz, the error voltage output from the phase comparator 34 is supplied to the voltage controlled oscillator 39 via the loop filter 37 and the changeover switch 32, and the voltage controlled oscillator 39 Phase synchronized to the frequency of 150+21.4MHz.

In this way, according to the present invention, the ultimately required frequency is directly oscillated using a voltage controlled oscillator, and the reference oscillator and voltage controlled oscillator are provided independently for transmission and reception, so that the transmitting/receiving device The number of parts and circuit blocks can be reduced without deteriorating the performance of the device, and the device can be constructed at low cost. Therefore, the present invention is particularly effective for press-talk type mobile radio equipment.

Further, as shown in the embodiment, if a voltage controlled crystal oscillator is used as the transmission reference oscillator, the transmission reference oscillator can be used as a signal source for frequency modulation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a transmitting and receiving circuit in a conventionally used crystal oscillation multiplication method, FIG. 2 is a block diagram of a transmitting and receiving circuit in a conventionally used phase control method, and FIG. 3 is a transmitting and receiving circuit in an embodiment of the present invention. FIG. 2 is a block diagram of the device. 31, 32...Switch switch, 33, 41...
Reference oscillator, 34... Phase comparator, 35, 39...
...Voltage controlled oscillator, 36... Frequency divider, 37... Loop filter, 38, 40... Output terminal.

Claims (1)

[Claims] 1. A first reference oscillator consisting of a voltage-controlled crystal oscillator capable of frequency modulation and obtaining a first reference frequency corresponding to the required channel for transmission, and a local oscillation frequency corresponding to the required channel for reception. a second reference oscillator that obtains a second reference frequency different from the first reference frequency for the input control signal; a first voltage-controlled oscillator that outputs a transmission frequency according to the input control signal; a second voltage controlled oscillator that outputs a corresponding local oscillation frequency for reception; a frequency divider that divides the frequencies output by the first and second voltage controlled oscillators;
a first signal selection means for selecting the output of the first reference oscillator when in the transmission state and the output of the second reference oscillator when in the reception state; and a signal supplied from the first signal selection means. a phase comparator that performs a phase comparison between the signal supplied from the frequency divider and the signal supplied from the frequency divider; a second signal selection means for supplying the output as a control signal for a second voltage controlled oscillator while in a receiving state, for supplying the output as a control signal for a second voltage controlled oscillator.