JPS59198054A - Automatic frequency control system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to FSI ((FrequencyShift T
(eying) related to communication systems, especially automatic frequency control systems in the FSK communication system n0)
Prior art and problems In the FSK communication system, automatic frequency control (abbreviated as AFC) is not performed directly using the received F'SK modulated wave, but is generally performed using a pilot signal. doing this.

Figures 1 and 2 show the conventional FSX communication system user-F.
FIG. 2 is a block diagram and a signal arrangement diagram of the C method.

As shown in Fig. 2, the signal is composed of a digital signal component DS and a pilot signal component PS, and the carrier wave FSX modulated with such a signal is shown in Fig. 1.
i” S K received by the receiver and added to the received input signal to the input terminal IN of the frequency converter CON 6i1.
It is mixed with the output signal from the voltage controlled oscillator vCO, frequency-converted to an intermediate frequency (for example, 10.7 MHz), and taken out from the output terminal OUT, but a portion is not added to the band R wave generator BPF-1. A pilot signal component PS is taken out at \. This signal component PS is applied to a frequency discriminator DIS, and a frequency error component of the pilot frequency is taken out and added to the voltage controlled oscillator VCO through a low-pass P-wave generator LPF. The oscillation frequency of this voltage controlled oscillator vCO is set to 1 so that the output of the frequency discriminator DIR becomes O.
As a result, the pilot signal component PS added to the output signal of the frequency converter CON has an added frequency, and the frequency interval between the pilot signal component and the digital signal component also has a predetermined frequency interval. ○ However, this method requires a frequency band and power to send the pilot signal, so in systems where both frequency band and power are limited, such as satellite communication, the frequency band and power will increase. There was a problem in that the reliability of the system decreased due to the increase in the number of component parts.

(c) Purpose of the Invention The invention was made in view of the problems of the prior art described above, and it is possible to generate a pilot signal by using mark signals or space signals that are continuous for a certain period or more and are included in a completely random digital signal. The purpose is to provide a complete AFC system that does not require any signals.

(d) Structure of the Invention The object of the invention is to frequency-convert the received FSKig wave using a frequency converter in the FSK communication system that communicates using FSK waves modulated with random digital signals. For example, a continuous mark signal component (frequency ft is normal) is extracted from a part of the frequency-converted signal using a full-band P-wave generator, and this output signal is regenerated into a digital waveform by a detector and a voltage comparator, which is then used as an integrator. The frequency-converted signal is applied to a frequency discriminator, so that the frequency of the continuous mark signal component becomes fl
If the integrator is different, the DC output voltage corresponding to this frequency difference is changed and the integrator is charged while the integrator is in operation. This photoelectric voltage is controlled by voltage control.

As a result, the frequency of the continuous mark signal component can always be maintained at the following level, so the continuous mark signal or continuous space signal has the same function as the conventional nokuiro and nodo signals. Figure 3 is a block diagram and operation explanatory diagram showing an embodiment of the invention, in which CON is a frequency converter, CO is a voltage control excavator, and DIS is a frequency discriminator. ,
INT-1 is a sample-and-hold integrator, BPF-2 is a band f-wave generator for extracting mark signal components or SFOUS signal components,
DET represents a detector, and COM represents a voltage comparator.

Embodiments of the invention will now be described in detail with reference to the drawings. FIG. 3(a) is a block diagram of an embodiment of the invention, in which the frequency converter C
The first input terminal of ON is connected to the terminal IN, the second input terminal is connected to the output terminal of the voltage controlled oscillator VCO, and the output terminal is connected to the terminal O.
Each is connected to a UT.

The input terminals of the frequency discriminator DIS and the band P-wave filter BPF-2 are connected to the terminal OUT, respectively, and the output terminal of the frequency discriminator DIS is connected to the first input terminal of the integrator INT-1. 1 output terminals are respectively connected to input terminals of a voltage controlled oscillator vCO.

On the other hand, the output terminal of the band f wave filter BPF-2 is connected to the input terminal of the wave detector ET, the output terminal of this wave detector ET is connected to the input terminal of the voltage comparator COM, and the output terminal of the voltage comparator 〇M is connected to the input terminal of the voltage comparator COM. Explain the operation of the circuit shown in this block diagram, which is connected to the second input terminal of the integrator INT-1. For example, a mark signal is generated with a certain probability, and a mark signal or a space signal is randomly generated between this mark signal and the next consecutive mark signal. A carrier wave FSK modulated with such a digital signal is applied to a frequency converter CON of the receiver. Here, it is mixed with the output from the voltage controlled oscillator vCO, converted into an intermediate frequency signal (eg, intermediate frequency 10.7 MHz), and most of the signal components are taken out from the terminal out. Is the remaining part a band for extracting mark signal components or space signal components?
It is added to the I-' waveform generator BPF-2. With this band f wave filter, only the mark signal component is extracted in the form shown in FIG. 3(e). The rise and fall of this waveform are delayed correspondingly during the band of this band f wave generator. The waveform shown in Fig. 3(e) is applied to the wave detector DET, where the envelope is detected and the intermediate frequency component is removed, resulting in the waveform shown in Fig. 3(d).This waveform is applied to the voltage comparator COM. Threshold voltage A-A
When the voltage is higher than this voltage and 1 is low, it becomes O, and a pulse waveform corresponding to the detected waveform as shown in FIG. 3(e) is obtained. This waveform is applied to the sandal-hold type integrator INT-1, which converts this integrator into 0N-O
FF'.

Meanwhile, another part of the remaining part of the intermediate frequency signal is applied to the frequency discriminator DIS. This discriminator outputs a voltage of 0 when a frequency component corresponding to the mark signal component is added, and an output voltage of 0 or - corresponding to the frequency error at other frequencies; The components vary depending on the waveform sequence, but since they are random, the output voltage is almost O and these voltages are 0N-OFF.
is added to the sample-and-hold integrator INT-1. Here, the time point when the frequency error voltage of the mark signal component is applied to this integrator INT-1 and this integrator is turned on.
The point in time when the state is reached is synchronized, but the point in time when the other discriminator output voltages are applied to the integrator is not synchronized with the ON state of the integrator itself, so this output voltage is not integrated. S/ of the input signal of the integrator without affecting the operation of the integrator.
N will improve. This sample-hold type integral! The error' voltage applied to INT-1 charges the capacitor of this integrator component, but the integrator's operating OF
When F, the input/output impedance for one lag becomes very high, so this charged voltage is held until the next error voltage is applied to this integrator.

This voltage is then applied to a voltage controlled oscillator vCO having a high input impedance, and the oscillation frequency of the voltage controlled oscillator is changed so that the error voltage becomes zero.

FIG. 4 is a block diagram showing an embodiment of another invention.
T-2 is a peak value holding type integrator, and the same symbols as in FIG. One input terminal is connected to the terminal IN, the other input terminal is connected to the output terminal of the voltage controlled oscillator, and the output terminal is connected to the terminal OUT. Then, the input side of the wave filter BPF-2 is connected to the terminal OUT, the output side is connected to the input side of the frequency discriminator, and the output side of the frequency discriminator is connected to the input side of the peak value holding type integrator INT-2. The output sides of the integrator-2 are respectively connected to the input terminals of the voltage controlled oscillator.

The operation of the circuit shown in this block diagram is as follows. That is, the mark signal component extracted by the band f wave filter BPF-2 as described above is used to obtain the frequency error voltage of the mark signal component by the frequency discriminator DIS. This error voltage is collected by the peak value holding type integrator INT-2 and applied to the voltage controlled oscillator VCO having a high input impedance, causing the entire oscillation frequency of this voltage controlled oscillator to change as described above.

In order to ensure the AFC operation, instead of using continuous mark signals or continuous space signals generated from random digital signals, there is also a method of intentionally inserting continuous mark signals of a certain length into the digital signal at a certain period. be.

(f) As explained in detail, according to the invention, it is possible to apply AFC' to the FSX modulated wave without using a pilot signal. E No. 49

Claims (1)

[Claims] 1. In the FSX communication system that communicates using FSK waves modulated with random digital signals, the received F
The frequency of the SK modulated wave is converted by a frequency converter using the output signal of the voltage controlled oscillator, and the frequency-converted signal is discriminated by a frequency discriminator. Alternatively, the frequency of the output signal of the voltage controlled oscillator is determined by using an integrator whose operation is interrupted by the signal extracted by means for selectively extracting only continuous space signal components, and using the output of the integrator as a frequency error signal. Automatic frequency control system that keeps the frequency constant. 2 In the FSK communication method, which uses FSK waves modulated with random digital signals, the received FS
The frequency of the K modulated wave is converted by a frequency converter using the output signal of the voltage controlled oscillator, and only continuous mark signal components or continuous space signal components are selectively extracted from the frequency-converted signal, and the extracted signal is Component is added to the frequency discriminator to detect the frequency error/signal, and the detected signal? An automatic frequency control system characterized in that, in addition to a constant value holding type integrator, the frequency of the output signal of the cough frequency converter is kept constant in addition to the output signal of the integral == voltage controlled oscillator.