JPS61182317A - Automatic frequency controller - Google Patents

Abstract

PURPOSE:To attain high accuracy and high frequency stability by comparing the result of frequency measurement of a regenerative carrier of the synchronous detection system phase modulation/demodulation means for the same frequency as the intermediate frequency with an intermediate frequency reference data and controlling a local oscillating means so as to bring the difference between the both to be within a prescribed value. CONSTITUTION:A synchronous detection system phase modulation signal demodulating means 12 demodulates a signal wave amplified by an intermediate frequency amplifier means 4 and outputs a generative carrier to a frequency measuring means 13. A microprocessor 14 consists of a storage section storing a frequency measured data measured by the frequency measuring means 13, the intermediate frequency reference data and a frequency dividing ratio N of a variable frequency divider 9 deciding the local oscillating frequency, and an arithmetic processing section comparing and deciding the relation of quantity between the frequency measured data and the intermediate frequency reference data and since the result of frequency measurement of the regenerative carrier of the synchronous detection system modulation/demodulation means 12 having the same frequency as the intermediate frequency and the intermediate frequency reference data are compared and the local oscillating means 12 is controlled so that the difference between the both is made constant, the intermediate frequency is controlled with high accuracy and high stability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic frequency control device in a carrier phase modulation signal receiver.

BACKGROUND OF THE INVENTION Satellite broadcasting receivers, which have been attracting attention in recent years, generally require frequency conversion means, and automatic frequency control is important because the frequency stability of the receiver is poor.

FIG. 3 shows the configuration of a conventional automatic frequency control device. 1 is a high frequency amplification means, 2 is a local oscillation means, and 3 is a frequency conversion means, which converts the output signal of the high frequency amplification means 1 into an intermediate frequency using the oscillation output of the local oscillation means 2. 4 is an intermediate frequency amplifying means, and 5 is a frequency demodulating means, which converts the frequency deviation of the intermediate frequency signal into a voltage deviation. 6 is an integrating means which integrates the output voltage of the frequency demodulating means 5 to obtain the center potential of the voltage deviation. The output of the integrating means 6 corresponds to a carrier wave or a local oscillation frequency, and the output of the integrating means 6 is fed to the local oscillation means 2 to control the local oscillation frequency.

The operation of the conventional automatic frequency control device configured as described above will be explained below.

First, it is assumed that the intermediate frequency fluctuates by Δf due to fluctuations in the reception frequency and fluctuations in the local oscillation frequency. This Δf
The varied intermediate frequency is supplied to frequency demodulation means 5, which converts the frequency deviation into a voltage deviation. The output of the frequency demodulating means 5 is also supplied to the integrating means 6, which extracts the carrier component with the baseband component suppressed to obtain the voltage ΔV corresponding to the above-mentioned Δf.

The local oscillation frequency is controlled by this voltage ΔV so that the intermediate frequency is kept constant.

Problems to be Solved by the Invention However, in the conventional automatic frequency control device, the performance of the device is greatly affected by the characteristics of the frequency demodulating means 5, and the frequency stability is affected by the temperature characteristics of the frequency demodulating means 5, aging, etc. It also had problems in that it required adjustment and the 'lTi1 wave number stability was also poor.

The present invention provides an automatic frequency control device that can perform highly stable and highly accurate frequency control in response to environmental changes in a carrier phase modulation signal receiver.

In order to solve the above problem, the carrier wave phase of the present invention, ′(
The automatic frequency control device in the modulated signal receiver has a frequency measuring means that measures the frequency of the carrier wave reproduced by the synchronous detection phase modulation demodulating means, and compares and determines the measurement data of this frequency measuring means with the reference data of the intermediate frequency. and a local oscillation means that controls a frequency division ratio using the output signal of the comparison and determination means so that the difference between the measurement data and the reference data of the intermediate frequency is within a certain value.

According to the above-described configuration, the present invention controls the frequency division ratio so that the difference between the measurement data of the frequency measurement means and the reference data of the intermediate frequency is within a certain value, and controls the frequency of the local oscillation means. The intermediate frequency can be controlled stably with high precision.

Embodiment Hereinafter, an automatic frequency control device used in a carrier phase modulation signal receiver according to an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, 1 is a high frequency amplification means, 2 is a local oscillation means, and 3 is a frequency conversion means, which converts the output signal of the high frequency amplification means 1 into an intermediate frequency using the oscillation output of the local oscillation means 2. The local oscillation means 2 is constituted by a PLL circuit, and a voltage controlled oscillator 8 is controlled by a loop filter 7. The output of the voltage controlled oscillator 8 is outputted to the frequency conversion means 3 and a variable branching unit 9 controlled by the microprocessor 14. The output frequency-divided by the variable divider 9 is supplied to a phase comparator 1o, which outputs a signal corresponding to the phase difference and frequency difference between the signals of the output of the variable divider 9 and the reference circle e number generator 11. Ru. Loop filter 7 is phase comparator 1
A signal for controlling the oscillator of the voltage controlled oscillator 8 is output from the output signal of 0.

Reference numeral 4 denotes intermediate frequency amplification means for amplifying the intermediate frequency converted by the frequency conversion means 3. Reference numeral 12 denotes a phase modulated signal demodulating means using a synchronous detection method, which demodulates the intermediate frequency phase modulated signal wave amplified by the intermediate frequency amplifying means 4 and outputs a reproduced carrier wave to the frequency measuring means 13. Frequency dividing means 1
3 measures the frequency of the reproduced carrier wave output by the synchronous detection type phase modulation demodulation means under the control of the microprocessor 14, and outputs the measurement data to the microprocessor 14. The microprocessor 14 includes a storage unit that stores frequency measurement data measured by the frequency measurement means 13, intermediate frequency reference data, and a value N of the frequency division ratio of the variable divider 9 that determines the local oscillation frequency; It is composed of an arithmetic processing unit that compares and determines the magnitude relationship between data and intermediate frequency reference data, and determines the start and end timing of frequency measurement by the frequency measuring means 13, and the value N of the variable frequency division ratio.
control. FIG. 2 shows the main part of a flowchart under the control of the microprocessor 14.

The operation of the automatic frequency control device in the carrier phase modulation signal receiver configured as described above will be explained below with reference to FIGS. 1 and 2. First, the desired reception frequency f
. When is selected, this frequency &f. The microprocessor 14 sends out the frequency division ratio N for the variable frequency divider 9, sets the frequency division ratio of the variable frequency divider 9 to N, and determines the oscillation frequency f1 of the voltage controlled oscillator 8 (step 21). And the local oscillation frequency f
1. Wait until the temperature becomes stable (Step 22)
). Here, the local oscillation frequency f1 or the desired receiving frequency f.

When there is a variation of Δf, the phase-modulated intermediate frequency signal f2 also includes a variation of Δf. The phase modulated intermediate frequency signal f2 is demodulated by the synchronous detection type phase modulation demodulation means 12, and the synchronous detection type phase modulation demodulation means 12 outputs the intermediate frequency signal f2.
A carrier wave 12' having the same frequency as that of the carrier wave 12' is reproduced. The frequency of this reproduced carrier wave f2' is measured by the frequency measuring means 13 (step 23), and the frequency measurement result thus obtained is sent to the storage section of the microprocessor 11, and the intermediate frequency reference τ set in advance is sent to the storage section of the microprocessor 11. is subtracted by the arithmetic processing unit to obtain data for the frequency difference between both signals.

It is determined whether this frequency data is within a certain value (step 24), and if the frequency difference data is greater than the certain value,
The magnitude relationship between the frequency measurement result and the intermediate frequency reference data is compared (step 25). Here, assuming that the local oscillation frequency is set to IJIU above the reception frequency, if the frequency measurement result is higher than the intermediate frequency reference data, the frequency division ratio is increased (step 26) (N-1-1). Then, the process returns to step 21. Also, if the frequency measurement result is lower than the intermediate frequency reference data, reduce the frequency division ratio (
Step 27) Return to step 21 as [N-1].

Steps 21 to 24 operate constantly, and Step 2
When the frequency difference data exceeds a certain value in step 4 and automatic frequency control becomes necessary, the process returns to step 21 via steps 21 to 26 or 27. In this way, the local oscillation means is set so that the frequency measurement result of the regenerated carrier wave of the synchronous detection type phase modulation demodulation means, which has the same frequency as the intermediate frequency, and the intermediate frequency reference data are compared and the difference between the two is constant. control, the intermediate frequency can be controlled with high precision and stability.

Effects of the Invention As described above, the automatic frequency control device in the carrier phase modulation signal receiver of the present invention can combine the frequency measurement result of the regenerated carrier wave of the synchronous detection type phase modulation demodulation means, which has the same frequency as the intermediate frequency, with the intermediate frequency reference data. In order to control the local oscillation means so that the difference between the two is within a certain value by comparing the
The frequency stability is not influenced by the temperature characteristics or changes over time of the frequency demodulating means, as in the conventional case, and high precision and excellent high frequency stability can be achieved without the need for adjustment as in the conventional case.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an automatic frequency control device according to an embodiment of the present invention, FIG. 2 is a flowchart of main parts of microprocessor control in FIG. 1, and FIG. 3 is a block diagram of a conventional automatic frequency control device. . 1... High frequency amplification means, 2... Local oscillation means, 3... Frequency conversion means, 4...
- Intermediate frequency amplification means, 5... Frequency demodulation means, 6... Integrating means, 7... Loop filter, 8... Voltage controlled oscillator, 9.・・・・・・
Variable frequency divider, 1o... Phase comparator, 11...
. . . Reference frequency generator, 12 . . . Synchronous detection phase modulation demodulation means, 13 . . . Frequency control means, 14 . . . Microprocessor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3

Claims (1)

[Claims] A frequency measuring means for measuring the frequency of a carrier wave reproduced by the synchronous detection type phase modulation demodulating means, and a comparing and determining means for comparing and determining the measurement data of the frequency measuring means and reference data of the intermediate frequency are provided. An automatic frequency control device characterized in that the frequency division ratio of the local oscillation means is controlled by the output signal so that the difference between the measurement data and the intermediate frequency reference data is within a certain value.