JPH012422A - 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 communication devices, and the like.

BACKGROUND OF THE INVENTION Conventionally, signals used for satellite broadcasting and satellite communications have been FM signals. For this reason, satellite broadcasting and satellite communication receivers 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, it is only possible to expect an improvement in the threshold level of 1 to 2 dB due to the modulation specifications of the FM signal.

In this regard, new technology was required. Regarding this, for example, [Ageo et al., Current status of satellite broadcasting home receivers, Journal of the Society of Television Engineers: VO13GI NI IOJ]
It is stated in In addition, a variable frequency filter (tracking filter) or a frequency converter was connected in front of the phase-locked demodulator to improve the carrier-to-noise ratio of the input signal and increase sensitivity. Regarding this, for example, "Jay Clapper et al.: Phase-locked and frequency-feedback systems; Academic Press +1972 (J, KIapper, eLal: Pha
se-Looked and Frequency-Fe
edback Systems; AC^ Kano old CI'1l
ESS, 19T2) stated in J. Hereinafter, the above-mentioned conventional receiving device will be explained with reference to the drawings. FIG. 2 is a circuit block diagram of a conventional receiving device,
FM (No. 3 is a tracking bandpass filter (hereinafter referred to as tracking B) which has a passband width narrower than the occupied frequency bandwidth determined by its frequency deviation.
After passing through PF (abbreviated as PF) 2, the signal enters a gain controller 3 to obtain the optimum signal strength for two rounds, and then enters a phase comparator 4. A part of the signal from the output of the gain controller 3 is input to the detector 8 and converted into a DC component according to the intensity of the δ signal. ft3mA is applied so that the output signal strength is constant. The oscillation signal of the oscillator 7 is input to the phase comparator 4, and its phase with the FM signal is compared.6 The output signal corresponding to the phase difference is input to the DC amplifier 5, and after amplification, is passed through a loop filter (hereinafter referred to as LPF). 6, and its output enters the oscillator 7 to synchronize the phase of the oscillation signal of the oscillator 7 with the phase of the FM signal. The output from the LPF 6 passes through a de-emphasis 12 and is output from a terminal 13. Also, the L
A part of the output of the PF6 is supplied via the 13PF11 to the drive circuit 10 that varies the center frequency of the tracking BPF2. This center frequency is synchronized with the instantaneous frequency of the FM signal inputted to terminal 1, 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. The human input signal strength of the phase comparator changes, and 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-mentioned problems, and aims to provide reception 'AE with improved threshold level by combining a synchronization range extended type PCI that expands the synchronization range, a demodulator, and a tracking BPF. There is.

Means for Solving the Problems In order to solve the above problems, the receiving device of the present invention includes two phase comparators for detecting the synchronization state of a synchronization range expansion type PLL1tA unit that expands the synchronization range. A part of the output of the phase comparator 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, and also to control the PLL demodulator. By controlling the bandwidth of the tracking BPF connected to the input, as the phase difference of the PLL increases, the tracking B
This configuration has a configuration in which the bandwidth of the PF is narrowed to increase the carrier-to-noise ratio and improve the threshold level.

Effect: With the above-described configuration, the present invention makes it possible to improve the threshold level by keeping the input signal strength to the LL demodulator constant and varying the bandwidth of the tracking 13PF connected to the input. Become.

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 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 BPF2 is tracked BPF2)
It enters a gain controller 3 to correct the attenuation due to F 2 and to make the human input signal strength to the phase comparator 234.17 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 using a π/2 phase shifter! 5 and when phase synchronization is achieved in the loop by the phase comparator 4,
The signal and the oscillation signal are synchronized and synchronous detection is performed. The output signal is amplified to a predetermined magnitude by a DC amplifier 16, and then entered into a divider 14, where the ratio between the output signal output from the DC amplifier 5 and the DC amplifier 16 is fJ1X+.

and supplies the result to LPF6. 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 characteristics of the phase comparator become a tangent function. Further, the LPF 6 supplies the oscillator 7 with a limited bandwidth required to stabilize the loop. This improves the threshold level. On the other hand, a part of the output signal from the LPF 6 is outputted as a demodulated signal from a terminal 13 via a de-emphasis 12.

In addition, a part of the output signal from the LPF 6 enters the center frequency control circuit 10 via the BPF II and the tracking BPF
The center frequency of 2 is changed in synchronization with the frequency shift of the input FM signal to reduce noise power. Further, a part of the output signal of the phase comparator 17 is input to the gain control drive circuit 9 to obtain a DC voltage or a 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 with constant power to the phase comparator 4.17 to keep the loop gain constant, stabilize the phase synchronization, and improve the threshold level.

Effects of the Invention As is clear from the above description, the present invention provides a tracking BPF that connects the output signal of one phase comparator of a synchronization range extended PLL demodulator to the input side of the gain control signal.
By using it as a signal to change the bandwidth of the tracking BPF, it detects the phase synchronization state, corrects the attenuation caused by the tracking BPF2, keeps the input signal strength to the phase comparator constant, stabilizes the phase synchronization, and It is possible to provide a receiving device that optimizes the bandwidth and improves the threshold level.

[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, 10...
...Center frequency control circuit, 11...BPF, 1
2... De-emphasis, 14... Divider, 15... π/2 phase shifter, 16...
・DC amplifier, 17... Phase comparator, 18...
...Bandwidth control 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 bandwidth of the variable frequency narrowband filter.