JPS63299505A - Receiver - Google Patents

Abstract

PURPOSE:To stabilize the phase synchronization and to improve a threshold level by using the output signal of a phase comparator of a demodulator as a gain control signal so that a phase synchronizing state is detected and at the same time the attenuation due to a tracking BPF is corrected to secure the constant intensity of an input signal applied to the phase comparator. CONSTITUTION:The oscillation signal of an oscillator 7 is partly supplied to a phase comparator 17 via a pi/2 phase shifter 15 and an input FM signal has the same phase as the oscillation signal for execution of the synchronizing wave detection while the phase synchronization is secured with a loop formed by a phase comparator 4. In other words, the output of the comparator 17 is partly supplied to a gain control driving circuit 9 so that the DC voltage or the DC current is obtained in accordance with the intensity of the input signal of the comparator 17 and supplied to a gain controller 3. As a result, the input signals are supplied to phase comparators 4, 17 at a fixed level of electric power to ensure a constant level of the loop gain. Thus the phase synchronization is stabilized and the gain control is accurate so that the intensity of the FN signals supplied to the phase comparators are kept at a fixed level. Then the threshold level is improved.

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.

2. Description of the Related Art Conventionally, receivers for satellite broadcasting and satellite communications have used phase-locked demodulators to receive incoming weak radio waves with high sensitivity. However, for a signal close to the saturation level, such as a color par signal, the threshold level can only be improved by 1 to 2 dB due to the modulation specifications. In this regard, new technology was required. Regarding this, see "Nio et al., Current Status of Satellite Broadcasting Home Receivers, Journal of the Television Society:
It is stated in vo138 no, 10J. In addition, a variable frequency filter (Tora or King 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, Jay Flapper et al.
and Frequency Feedback Systems, Academic Press 1972 (J, Klap
per, etal: Ph5ae-Looked
and Frequency-FeedbackS
systems; ACADEMIC PRESS,
(1972). 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, in which an FM signal manually input from terminal 1 is passed through a tracking bandpass filter (hereinafter referred to as - After passing through a racking BPF), the signal enters a gain controller 3 to obtain the optimal signal strength for demodulation, and then enters a phase comparator 4. profit system i
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 corresponding to the signal strength, and then input to the gain control drive circuit 9 to detect the output signal strength of the gain controller 3. Negative feedback is applied to keep the value constant. The oscillation signal of the oscillator 7 is inputted to the phase comparator 4, and the output signal corresponding to the zero phase difference is inputted to the FM signal. 6 and its output enters the oscillator 7
The phase of the oscillation signal is synchronized 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. Further, a part of the output of the LPF 6 is supplied via the BPF II to a drive circuit 10 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 1, and only the noise power decreases without changing the frequency deviation.
The threshold specific to the M signal has been improved.

Problems to be Solved by the Invention However, in the above configuration, the gain control is not linked at high speed, so the input signal strength of the phase comparator changes, the out-of-phase of the phase synchronized demodulator increases, and the threshold level will deteriorate.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a receiving device with an improved threshold level by combining a synchronization range expansion phase synchronization type 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 extended phase synchronization type demodulator that is provided with two phase comparators and expands the synchronization range. Therefore, 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 improve the threshold level. It has the following configuration.

According to the present invention, with the above-described configuration, it is possible to stabilize the synchronization and improve the threshold level by keeping the input signal strength to the phase-locked demodulator constant and suppressing changes in the loop gain.

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. The tracking BPF
The input signal that has passed through 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 comparators 4 and 17 constant. Then phase comparator 4
and enters 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. Also, a part of the oscillation signal from the oscillator 7 is sent to the phase comparator 17 through the π/2 phase shifter 15.
When the input FM signal and the oscillation signal are inputted through the phase comparator 4 and phase synchronized in the loop formed by the phase comparator 4, the input FM signal and the oscillation signal are in phase, and synchronous detection is performed. The output signal is amplified by the DC amplifier 1, enters the divider 14, and outputs the output signal from the DC amplifier 5.
6 is calculated and the result is supplied to the LPF 6. 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, 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 IO via the BPF II, and the center frequency of the retracing BPF 2 is changed in synchronization with the frequency deviation of the human-powered 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 and stabilize the phase synchronization.

Effects of the Invention As is clear from the above explanation, the present invention utilizes the output signal of one phase comparator of a phase-locked demodulator with extended locking range as a signal for gain control, thereby improving the phase-locked state. It is possible to provide a receiving device that corrects the attenuation caused by the tracking BPF 2 while detecting it, keeps the input signal strength to the phase comparator constant, stabilizes phase synchronization, and improves the threshold level.

[Brief explanation of drawings]

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...
...Drive circuit, 11...BPF, 12...
...De-emphasis.

Claims (1)

[Claims] The FM signal is input and demodulated via a variable frequency narrowband filter and a gain controller to a phase synchronized demodulator consisting of first and second phase comparators, a DC amplifier, a loop filter, a divider, and an oscillator. At this time, the center frequency of the variable frequency narrowband filter is varied using a part of the demodulated signal, and the variable frequency narrowband filter operates to follow the frequency change of the input signal, and is synchronized to detect the synchronization state of the phase synchronized demodulator. The second part performs the detection operation.
A receiving device characterized in that a part of the output of the phase comparator is used as a drive signal for a gain controller that changes input signal strength to the first and second phase comparators.