JPS61200723A - Forming circuit for angular modulation transmission wave in simultaneous transmission and reception communication equipment - Google Patents

Abstract

PURPOSE:To quicken the response speed of a PLL by bringing the cut-off frequency of an LPF at a transmission side PLL circuit to a value being >=4 times of the highest modulation frequency and applying modulation just after a high stable oscillator. CONSTITUTION:The highly stable oscillator 1 is a reference frequency generator using a crystal oscillation circuit and is used in common for transmission and reception and a PLL circuit to obtain a local oscillation frequency output 12 and a transmission output 13 of a receiver is provided separately. A modular 10 at the sending side applies angular modulation to a reference frequency output from the oscillator 1 and an angular modulation signal wave output 11 and the output of the modulator 10 is used to compare the phase of it with that of an output frequency fS/M being the frequency division of a transmission frequency fS of a VCO 8 at a 1/M frequency divider 9 by means of a phase comparator PC 6. An output proportional to the phase difference of the output of the PC 6 is generated, fed to an LPF 7, whose output controls the VCO 8. The reference speed of the transmission PLL circuit comprising the PC 6 - the frequency divider 9 depends on the LPF 7 and the frequency divider 9, but the response is quickened by setting the cut-off frequency of the LPF 7 to a value being >=4 times of the highest frequency of the modulation signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a communication device (
: A highly stable oscillator, which serves as a reference for the transmission frequency, is commonly used for transmission and reception, and a PLL that outputs a modulated wave for transmission is used.
This paper relates to the improvement of circuits obtained by using .

(Prior Art) FIG. 2 is a side view of the configuration of a modulator for angle modulation used in a conventional simultaneous transmitter/receiver, and also includes a local oscillator for reception. 1 in the figure is a highly stable oscillator, 2 and 6 are phase comparators (p
c), 3 and 7 are low pass filters (LPF), 4 and 8 are voltage controlled oscillators (VCO), 5 and 9 are frequency dividers, and 10 is a mixer (
11 is a modulated signal input, 12 is a receiving local oscillation frequency output, and 13 is a modulated transmission wave output. This circuit uses two phase-locked loops (PLLs) as shown in the figure, one of which uses the receiving local oscillation frequency f0.
The other PLL is used as a modulation loop for transmission, and the obtained modulated wave is output to the local frequency output 14 for transmission in the mixer 10. The signals are mixed to provide a transmission wave output 13. In this circuit, if the modulation signal is angle modulated, the voltage controlled oscillator (VCO) 8 is directly frequency modulated (FM), so P
The frequency response of the LL must be much slower than the modulating signal frequency. This has the following drawbacks.

l) Since the modulation loop has a slow frequency response, it takes a long time to rise from when the power is turned on until the system operates stably.

2) Since the transmitted wave uses a mixer, there is a large amount of unnecessary radiated waves (
In order to prevent this, a band pass filter or shielding is required, which makes the structure complicated and it is difficult to miniaturize and reduce costs.

(Specific purpose of the invention) Increase the response speed of phase locked loop (PLL).

Therefore, by choosing the cutoff frequency of the LPF to be much higher than the maximum frequency of the modulation signal, and by performing modulation immediately after the high stability oscillator and not using a mixer, the drawbacks of the conventional circuit can be eliminated. The purpose is

(Structure and operation of the invention) FIG. 1 shows an angle modulated transmission wave generator of a transmitter/receiver of the invention,
This is an example of the circuit configuration of a receiving local oscillator. The meaning of the symbol is 82.
As in the figure, 10 is a modulator. As shown in the figure, the highly stable oscillator 1 is a reference frequency generator using a crystal oscillation circuit, and is used for both transmission and reception, but separate PLL circuits are provided to obtain the local oscillation frequency output 12 of the receiver and the transmission output 13. There is.

Receiver side (to explain there are two, phase comparator (PC) 2
(Two reference frequencies fr and the output frequency f of VCO4.

The frequency division wave f0/N (N is a positive integer) is input, and the LPF31- output is proportional to the phase difference between these two frequencies.
(Thus, by setting it as the control voltage of VCO4,
It is well known that the stability (deviation rate) of the output frequency of the VCO 4 can be the same as the stability of the reference frequency fr. Note that fr=fo/N.

On the transmitting side C, the output of the reference frequency from the highly stable oscillator 1 and the angle modulated signal wave output 11 are sent to the modulator 10 (the two are angularly modulated by the phase comparator PC6).
The output frequency f of the frequency divider 9 of 17M (M is a positive integer) of the transmission frequency fs from s! 3/M, generate an output proportional to the phase difference (2), and add it to LPF7.6
The response speed of the transmitting PLL circuit according to ~9 is LPF'7
is determined by the constant of and the frequency divider 9.
If the cutoff frequency of F7 is increased, the response time and rise time will become faster. In such a state, the PLL circuit operates in accordance with the deviation of the reference frequency fr, so that if the reference frequency fr is shifted, the modulation signal 11 can be obtained as an angle-modulated transmission wave of 8. Therefore, the transmitting side circuit in Fig. 1 can be said to connect the angle modulator 1o to the output of the highly stable oscillator l, and apply the output as a shifted reference frequency to the transmitting PLL circuit, and this PLL circuit outputs Then, the frequency division number (M) times the deviation of the reference frequency is output as the frequency deviation. Setting fr=f and 7M means receiving P'
LL is the same as L.

Note that if the cutoff frequency of LPF7 is increased, there is a limit as it will pass unnecessary frequency components including noise, but in the circuit of the present invention, the cutoff frequency is much higher than the maximum modulation frequency (approximately 4 times or more). It has been confirmed that there are no practical problems.

(Effects of the Invention) 1) Since the transmission frequency is the same as the output frequency f8 of VCOS, there is no need to use a mixer as in the conventional case, and unnecessary radiation waves are not generated.

2) Since the rise time of the transmission system is fast, it is only necessary to turn off the power to the transmission PLL circuit when transmission is stopped, and leakage of transmission waves can be prevented.

3) The response time of the transmission system is fast, making it resistant to external disturbances.

4) Since the reference frequency is modulated, it is also possible to perform modulation at a modulation frequency from very low frequency.

[Brief explanation of drawings]

Fig. 1 is an example of the circuit configuration of a modulated transmission wave generator and a receiving local oscillator of a transceiver embodying the present invention, and Fig. 2 is a diagram of a modulated transmission wave generator and a receiving local oscillator of a conventional simultaneous transceiver. FIG. 2 is an example diagram of a circuit configuration. 1... Highly stable oscillator, 2,6... Phase comparator, 3.7... Low pass filter, 4.8... Voltage controlled oscillator, 5.9... Frequency divider, 10...Angle modulator, 11...Modulation signal input, 12...Receiver local oscillation frequency output, 13...
Transmission modulation wave output.

Claims (1)

[Claims] An angle modulation circuit to which the output from one high-stability generator for both transmission and reception and a modulation signal is applied, a phase comparator to which the output is applied, a low-pass filter, a voltage-controlled oscillator, and its feedback circuit are connected. It consists of a phase-locked circuit consisting of a frequency divider, and the cut-off frequency of the low-pass filter is selected to be approximately 4 times or more than the maximum modulation frequency, and a modulated transmission wave is obtained from the voltage-controlled oscillator of the phase-locked circuit. What is claimed is: 1. A circuit for generating an angle modulated transmission wave in a simultaneous transmission/reception communication device.