JPH012421A - receiving device - 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 FIELD OF INDUSTRIAL APPLICATION The present invention relates to a receiving device that can be used in satellite broadcast receivers, satellite broadcasting receivers, 1III transmitters, and the like.

BACKGROUND OF THE INVENTION Conventionally, signals used for satellite broadcasting and satellite communications have been FM signals. For this reason, receivers for satellite broadcasting and satellite communications have used phase-locked demodulators to receive incoming weak signals with high sensitivity. However, for a signal close to the saturation level such as a color par signal, the threshold level may be lower due to the modulation specifications of the FM signal! An improvement of only ~2 dB can be expected.

In this regard, new technology was required. Regarding this, for example [Ageo et al. l! Current status of 7-legged broadcasting home receivers, Journal of the Society of Television Studies: v o 13B
No, 10 Jr. states. In addition, a variable frequency filter (tracking filter) and a frequency converter were connected in front of the phase-locked demodulator to improve the carrier-to-noise ratio of the human signal and increase sensitivity. Regarding this, see ``J. Klapper, et al.; Phase-Locked and Frequent Sea-Feedback System;
l:Phase-Looked and Frequency
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CPRESS, 1972) J. The conventional receiver 13 device described above will be described below with reference to the drawings. FIG. 2 is a circuit block diagram of a conventional receiving device, and shows terminals! The FM signal input from i11! is narrower than the occupied frequency bandwidth determined by its frequency deviation. After passing through a tracking band pass filter (hereinafter abbreviated as tracking BPF) having an overbandwidth, the signal enters a gain controller 3 to have an optimum signal strength for demodulation, and then enters a phase comparator 4. A part of the signal from the output of the gain controller 21127r3 is input to the detector 8 and converted into a DC component according to the No. 13 intensity, and then manually inputted to the gain control drive port rB9 to output the signal from the gain controller 3. Negative feedback is applied to keep the signal strength constant. The H signal from the oscillator 70 is input to the phase comparator 4, and the phase is compared with the FM signal. The output signal corresponding to the phase difference is input to a DC amplifier 5, and after amplification, it is input to a loop filter (hereinafter referred to as LPF) 6, and its output is input to the oscillator 7, which converts the phase of the oscillation signal of the oscillator 7 into the phase of the FM signal. Synchronize with. The output from the LPF 6 passes through a de-emphasis 12 and is output from a terminal 13. Further, a part of the output of the LPF 6 is supplied via 13PFl 1 to a drive circuit IO that varies the center frequency of the tracking BPF 2. This center frequency is synchronized with the instantaneous frequency of the FM signal input to terminal l, and the frequency deviation remains unchanged, only the noise power is reduced, improving the threshold characteristic of the FM signal.

Problems to be Solved by the Invention However, in the above configuration, the gain control detector operates to detect DC components, so the gain control does not follow at high speed. As the input signal strength of the phase comparator changes, the loop gain of the phase-locked demodulator (hereinafter referred to as PLL demodulator) changes, resulting in an increase in out-of-phase and a deterioration of the threshold level.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a receiving device with an improved threshold level by combining a synchronization range extension type PLL demodulator that expands the synchronization range and a tracking BPF.

Means for Solving the Problems In order to solve the above problems, the receiving device of the present invention detects the synchronization state of a synchronization range extension type PLL demodulator that is provided with two phase comparators and expands the synchronization range. A part of the output of the phase comparator for the PLL demodulator is used as a drive signal for the gain controller to perform high-speed and accurate gain control to keep the FM signal strength entering the phase comparator constant. The threshold level is improved by changing the frequencies of the poles and zeros of the LPF so that the loop gain becomes the optimum gain.

Operation The present invention uses the above-described configuration to keep the strength of the human input signal to the PLL demodulator constant, and to change the pole and zero frequencies of the LPF, thereby stabilizing synchronization and improving the threshold level in order to suppress changes in the loop gain. becomes possible.

Embodiment Hereinafter, a receiving apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a circuit block diagram of a receiving device in an embodiment of the present invention. The FM signal input from the terminal 1 passes through the tracking BPF 2 to reduce the noise power without changing the frequency deviation and improve the ratio of carrier wave to noise power. Furthermore, the input signal that has passed through the tracking BPF 2 enters a gain controller 3 that corrects the attenuation caused by the tracking BPF 2 and makes the intensity of the input signal to the phase comparator 4.17 constant.

It then enters phase comparators 4 and 17. On the other hand, an oscillation signal is input from the oscillator 7 to the phase comparator 4, and the phase difference between the two signals becomes an output signal and is input to the DC amplifier 5. In addition, a part of the oscillation signal of the oscillator 7 is input to the phase comparator 17 via the π/2 phase shifter 15, and when phase synchronization is achieved in the loop by the phase comparator 4, the input FM
The signal and the oscillation signal are synchronized and synchronous detection is performed.The output signal is amplified to a predetermined size by the DC amplifier 16, and then enters the divider 14 where it is divided between the output signal δ output from the DC amplifier 5 and the DC amplifier 16. Calculate the ratio and write the result as L
It is supplied to PF6. The phase comparator 4 and the phase comparator 17 are orthogonal to each other, and as a result of the calculation performed by the divider 14, the characteristic of the phase comparator becomes a tangent leap number. Further L
P F 6 supplies the oscillator 7 with a limited bandwidth required to stabilize the loop. This improves the threshold level. On the other hand, LP
A part of the output signal from F6 is outputted as a demodulated signal from terminal 13 via de-emphasis 12. Also, L
A part of the output signal from the PF 6 is sent to the drive circuit 10 via the BPF II to change the center frequency of the large re-tracking BPF 2 in synchronization with the frequency deviation of the input FM signal, thereby reducing noise power. Further, a part of the output signal of the phase comparator 17 is inputted to the gain control drive circuit 9 to obtain a DC voltage or DC current according to the input signal strength of the phase comparator 17 and supply it to the gain controller 3. Then, the input signal is supplied to the phase comparator 4.17 with constant power to keep the loop gain constant and stabilize the phase synchronization. Also, the phase comparator! When the output of No. 7 is supplied to the LPF drive circuit 18 and the output increases, that is, when the FM (No. 3) entering the phase comparator increases, the bandwidth of the LPFG is narrowed to keep the synchronization state constant, Improving the level.

Effects of the Invention As is clear from the above explanation, the present invention utilizes the output signal of one phase comparator of the synchronization range extended PLL demodulator as a signal for changing the bandwidth of the gain control ring and loop filter. By doing so, while detecting the phase synchronization state, the attenuation caused by the tracking BPF 2 is corrected, the input signal strength to the phase comparator is kept constant, and the phase synchronization is stabilized.
It is possible to provide a receiving device that improves the threshold level by optimizing the bandwidth by changing the poles and zeros of the LPF.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a receiving device according to the present invention, and FIG. 2 is a circuit block diagram of a conventional receiving device. 2...Tracking BPF, 3...Gain controller, 4...Phase comparator, 5...
DC amplifier, 6... LPF, 7... Oscillator, 9... Gain control drive circuit/IO...
...Drive circuit, 11...BPF, 12...
...De Emphasis, 14...lit X
device, 15...π/2 phase shifter, 16...
DC amplifier, 17... Phase comparator, 18...
...LPF drive circuit.

Claims (1)

[Claims] The FM signal is input through a variable frequency narrowband filter and a gain controller to a phase-locked demodulator consisting of first and second phase comparators, a DC amplifier, a loop filter, a divider, and an oscillator for demodulation. In order to vary the center frequency of the variable frequency narrowband filter using a part of the demodulated signal, to operate to follow the frequency change of the input signal, and to detect the synchronization state of the phase synchronized demodulator. The second one performs synchronous detection operation.
A part of the output of the phase comparator is used as a drive signal for a gain controller that changes the input signal strength to the first and second phase comparators, and a part of the output of the second phase comparator is A receiving device characterized in that the receiving device is configured such that is used as a drive signal for changing the pole and zero point frequencies of the loop filter.