JPS6260387A - Satellite broadcast receiver - Google Patents

Abstract

PURPOSE:To securely prevent a signal from being mistakingly recognized by comparing the differentiation output of a video signal A delayed by 2H through two 1H delay lines with that of a 1H delayed video signal B and making the differentiation output appearing at the same horizontal phase continuously by 2H a signal and an output other than said output a noise, respectively. CONSTITUTION:A clock generator 13 drives the analog 1H delay lines 11 and 12 by a clock four times as much as a chrominance subcarrier. If the output of an FM detector 7 is (N+1)Hth, the outputs of the 1H delay lines 11 and 12 are nHth and (n-1)Hth, respectively. Monostable multivibrators 16 and 17 widen the outputs phi101 and phi100 of the 1H delay lines 11 and 12 to 0.5mus, for instance, through differentiation circuits 15 and 14, and a NAND gate 18 forms their AND and applies it to an AND gate 19. Then the pulse phi23 of the differentiation circuit 15 is removed. A pulse phi24 available from differentiating noise is applied to an analog gate as the output of the AND gate 19, to form a gate pulse of 0.5mus, for instance, and the signal of phi100' is outputted instead of the 'H' period at the pulse phi24. Then a signal excluding an impulse noise is supplied to an RF converter 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a satellite broadcast receiver for receiving satellite broadcast signals.

BACKGROUND OF THE INVENTION The present applicant has developed a noise removal circuit that first detects black peak noise that is higher than the pedestal level of the signal and white peak noise that is higher than the white peak of the signal, and when noise is detected, replaces it with the signal from 1H before. provided.

(Unexamined Japanese Patent Publication No. 60-99-814) Problems to be Solved by the Invention However, in the conventional example described above, black noise at a time when the video signal is close to the white peak and white noise when the video signal is close to the black peak are removed. The problem is that it can't be done. Furthermore, if the video signal is simply differentiated and the output level is used for determination, there is a problem in that the white peak (character) and black peak signals on the screen are mistaken for noise.

Means for Solving the Problems The satellite broadcasting receiver according to the present invention delays the video signal by 2H using two 1H delay lines, and outputs the differential output of the video signal B delayed by 2H and the differential output of the video signal B delayed by 1H. Compare. Then, only when the differential output of the video signal M is above a certain value and the differential output of the video signal B is below a certain value, it is determined to be FM impulse noise, and the video signal B is replaced for a certain period of time in place of the video signal. This is how it was done.

According to the present invention, by treating the differential output that appears with the same horizontal phase continuously for 2H as a signal and treating the rest as noise, it is possible to reliably prevent the signal from being misrecognized.

Embodiment FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a system configuration of a satellite broadcasting receiver incorporating the noise removal circuit of the present invention. First, in Figure 2, 1 is an outdoor unit (O
DU) and is also called I,NB (Low Noise Block Down Converter). 2 is a pillar that supports the outdoor unit 1,
A high frequency cable 4 is installed inside or outside the unit, and transmits the output signal of the outdoor unit 1 to the tuner 6. 3
The person is the parabolic antenna, and 3B is the pillar of the antenna 3m. 6 is a tuner that tunes to a desired radio wave and is also called a 7-channel mixer. 6 is an intermediate frequency (rF) amplifier, 7
8 is an FM detector, and 8 is an audio detector. When there are multiple audio carriers, they can be detected in synchronization. 9 is RF converter and 1
9 have the same configuration whether receiving Japanese satellite broadcasting (12 GHz) or American C-band satellite broadcasting (4G) lx).

10 is a noise removal circuit which is a feature of the present invention, and when the C/N ratio deteriorates, FM! appears in the video detection output! This is to remove excessive impulse noise.

Noise removal will be described below with reference to FIGS. 1, 3, and 4. In FIG. 1, reference numeral 11.12 is an analog 1H delay line composed of COD, which is driven by the clock generator 13. The clock of the clock generator 13 is 14.31818M)lz, which is four times the color subcarrier. When the output of the FM detector 7 is the (n+1)Hth, let's say the 102ndH, the output is 1H.
The output of the delay line 11 is the nHth (101H), and the output of the 1H delay line 12 is the (n-1)H (100H). The output φ101 of the 1H delay line 11 shown in FIG.
When differentiated by 5, the output becomes φ, 1. In addition to noise, a differential output is also obtained at the signal change point t1.

Further, when the output φ+oo of the 1H delay line 1'2 is differentiated by the differentiating circuit 14, the differential output φ, is obtained. get. Differential circuit 14゜1
6 assumes that the differential output in the negative direction is inverted and output.

The output of the differentiating circuit 14 is converted to a monostable multino
If the output of the differentiating circuit 15 is similarly widened by a monostable multivibrator 17 to a constant width, for example 0.5 μs, the voltage will change from φ1o to φ20.
+φ1. From φ2. You can get each one.

φ2o and φ2. When the logical product of is formed by the NAND gate 18, the output terminal of
is obtained. When φ22 is added to the AND gate 19, the t1 tenoval of the differential circuit 16 which differentiates the signal is φ2. is removed. When the time for the output axis of the differentiating circuit 15 to be transmitted to the AND gate 19 is Δt, the output φ25 of the differentiating circuit 16 is set to Δt.
Although it is necessary to delay .DELTA.t by more than 10 seconds, .DELTA.t is omitted in FIG. As the output of the AND gate 19, a pulse φ24 at time t5 obtained by differentiating the noise is obtained. This nokurusuφ
24 to analog gate 21. At t5 at the beginning of the pulse φ24, the multi-noise ibrator in the analog gate 21 is driven, and the width as shown in φ25 in FIG.
s gate pulse is formed.

On the other hand, 2o is a delay circuit of 4 clos) of 14.31818 M)lz, $+OQ *φ,. 1 by 4 clocks (x4-2sons). Therefore, on the input side of the analog gate 21, φ100
1φ. , and the switch pulse φ24 are as shown in FIG. 4, and a noise point tt is included in the gate pulse. If the width of the noise is wide, t~t is 1 μs instead of 4 μs.
You can spread it out as much as you like. Analog gate 21, φ24
rH” period (between 1 and t4) φ + oo instead of φ kidney
By outputting the signal, a signal containing no impulse noise is supplied to the RF converter 9.

In the case of this means, the signal of FIG.
Assuming that there are 0H to 125H, only the 90th H is determined to be noise and the signal of the 89th H is replaced, so the vertical line is shortened by 1H, but it is hardly noticeable in the video. Continuously for 2 hours, unless the C/N deteriorates extremely and the noise increases.
Since noise does not appear at the same horizontal phase, the noise can be removed using the method described above. Also, misunderstanding the signal is
It is only 1H in the vertical direction, and the entire diagonal line is 121H.
Since the screen is shifted downward by a minute, you can get a screen that is much easier to see than a screen that is difficult to see due to a lot of noise. Also, 2H in the same 1st block
Since it is delayed, even if the klovk frequency fluctuates, the difference of 1H is maintained accurately, making it possible to clearly distinguish between noise and signal.

Effects of the Invention As described above, according to the present invention, by combining a 2H delay line, a differentiating circuit, and an analog gate, impulse noise that does not reach the white peak or black peak can be detected and reliably removed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of a satellite broadcasting receiver according to an embodiment of the present invention, FIG. 2 is a block diagram of the entire satellite broadcasting receiving system including FIG. 1, and FIG. 3 is the operation of FIG. 1. FIG. 4 is a partially enlarged waveform diagram of FIG. 3 to explain the operation. 11...1H delay machine, 12...1H delay line, 13...clock generator, 14...
... Differential circuit, 15... Differential circuit, 16...
...-semi-stable multivibrator, 17...monostable multivibrator, 18...NAND gate, 19...AND gate, 2o...
・Delay circuit, 21...Analog gate. Name of agent: Patent attorney Toshio Nakao and one other person θ~ :2: ≧ Q −~ o.

Claims (1)

[Claims] a delay circuit that delays a video signal by 1H or more; a first differentiation circuit that differentiates a video signal A that arrives 1H later than the output of the circuit; and a second differentiation circuit that differentiates an output video signal B of the delay circuit.
A differentiating circuit is provided, and the outputs of both differentiating circuits are compared, and only when the differential output of the first differentiating circuit is above a certain value and the differential output of the second differentiating circuit is below a certain value, FM impulse noise is detected. A satellite broadcasting receiver characterized in that the satellite broadcasting receiver determines that the output video signal B is substituted for the video signal A only for a certain period of time.