JPS6266786A - Satellite broadcast receiver - Google Patents

Abstract

PURPOSE:To prevent the generation of a differential output caused by the rear edge of peak noise in a satellite broadcast receiving set that detects a television signal of satellite broadcast and obtains a video signal by removing a differential output that comes out at fixed time intervals in the differential output of a video signal. CONSTITUTION:In a satellite broadcast receiving set 7 that detects television signals of satellite broadcast and obtains video signals, output of differentiating circuits 12, 16 and a horizontal oscillation AFC circuit 14 is processed by a pulse processing circuit 13, and only the front edge of peak noise is taken out. The output of the pulse processing circuit 13, that is, only a fixed width (for instance 1us) from the front edge of peak noise, and the output of a delay circuit 19 is taken out in place of output of a delay circuit 17 and sent out. By such constitution, the differential output of a rear edge can be removed basing on the differential output of the front edge of peak noise, and the generation of two differential outputs from one noise can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a satellite broadcast receiver, and more particularly to a satellite broadcast receiver equipped with a circuit for removing FM noise on a screen.

Conventional technology FM detected video (F at the time of C/N deterioration included in issue i
Conventionally, as means for detecting peak noise peculiar to M waves, a method has been proposed that differentiates FM waves and determines a differential output of a certain value or more as noise.

Problems to be Solved by the Invention However, in the above-mentioned conventional method, when the rise and fall of the peak noise are steep, when the video signal is differentiated, both the leading edge of the noise and &M are There is a problem in that when the differential pulse exceeds a certain value, it is erroneously determined that noise is present.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to stop the generation of differential output due to the trailing edge of peak noise by 11/J.

Means for Solving the Problems In order to solve the problems, the present invention provides a satellite broadcasting receiver that detects a satellite broadcasting television signal and obtains a video < rs signal, by reducing the peak noise characteristic of FM waves. The apparatus is equipped with a circuit for detecting peak noise by differentiating the surface video signal for removal, and a circuit for removing the differential output that is cursed within a certain time interval during the differential output of the video signal.

If the effect is like this, the peak noise will be 1'+ii
Based on the differential output in %, the differential output at the trailing edge can be removed. Therefore, it is possible to prevent two differential outputs from being generated from the negative noise.

Embodiment Hereinafter, a satellite broadcasting receiver which is an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a C
An example of a receiving system for bunt or K14 bread 1- is shown.

In the figure] - is a parabolic antenna, and 2 is a low-noise converter called LNB. 3 is 'nhaata 2
A cable 6 is installed along this column 3 from the output end of the converter 2. 4 is a polarization plane switcher, which switches between inherited polarization and vertical polarization in the Ni band (in the United States), and circular polarization in the Ku band, but switching is not necessary. Reference numeral 5 denotes a pillar of the antenna 1, to which an actuator for changing the direction of the antenna is attached in the case of C band (USA). The cable 6 connects the converter 2 and the input end of the receiver 7, and a cable with good high frequency characteristics is used.

Reception +! &7 consists of a satellite broadcast receiver called an indoor unit (IDTJ). Here, 8 is a tuner that tunes to a desired wave output from converter 2, and is also called a second mixer. 9 is an IF amplifier, and 10 is a detection circuit for a frequency-modulated video signal. The output of the detection circuit 10 contains the audio signal as it is modulated, and the audio detection circuit 11 demodulates the signal into an audible frequency band signal. American C-band uses FM detection, but Japanese satellite broadcasting uses PCM demodulation. On the other hand, 12.16
is a video signal differentiating circuit having the same configuration, the contents of which are shown in FIG. 2 and described in detail later. 14 is synchronous separation, horizontal oscillation AFC
The circuit 15 is an analog IH delay line.

This may be delayed by a CCD. 13 is a differentiation circuit 12
, 16 and the output of the horizontal oscillation AFC circuit 14, and extracts only the leading edge of peak noise.

17 and 19 are short-time (for example, LH) delay circuits that adjust the difference with the output of the pulse processing circuit 13. 18 is
The output of the pulse processing circuit 13, that is, the peak noise [)η
This is a noise removal circuit that extracts and sends out the output of the delay circuit 19 instead of the output of the delay circuit I7 for only a certain width (for example, 1 μs) from the string. If you convert the output audio signal of the audio detection circuit 11 and the video No. 43 output from the noise removal circuit 18 into RF, or connect it directly to a monitor '1'V or stereo receiver, you can convert the video and audio. can be viewed and listened to.

Next, referring to FIG. 2, the differential circuit 12 according to the present invention.
16 will be explained in detail. Since both circuits 12 and 16 have the same configuration, only the differentiating circuit 12 will be described, and the differentiating circuit 16
will be explained by adding a dash to each part number. 4
9 is a human-powered buffer transistor.

In the case of circuit 12, the output of the detection circuit lO is the transistor 1
In the case of circuit 16, the output of LII delay line 15 is fed to the base of transistor 49'. 20 is an emitter resistor. Both the container 21 and the resistor 22 and the container 30 and the resistor 31 form a differential circuit,
I'm here. The voltage detected across the resistor 20 is φ in FIG. At this time, the pressure waveform at both ends of the resistor 22 and the resistor 31 becomes φ1 in FIG. 4. However, due to the action of the diodes 23 and 32, the waveform at both ends of the resistor 22 becomes φ1 in FIG. There is only an upward pulse, and the waveform at both ends of the resistor 31 is only a downward pulse, as shown by φ□ in Fig. 5.
In the figure + tnll to1' + tnll. 2' is the waveform obtained by differentiating the peak noise.

φ□1 in Figure 4. tl at φ1□, t3T
ts+use t,. , t41, etc. are obtained by differentiating the video signal and the synchronization signal. φ12 in FIG. 4 is a differential waveform before IH and is a waveform that should appear at both ends of the 5g resistors 22' and 31'. However, it is assumed that there is no peak noise before IH. Even if it existed, it would be the same as shown in Figure 4. □.

If it is a place other than tnz, φ. t 11 included in
1 +tn2 peak noise removal.

The transistor 24 in FIG. is inverted and amplified, and the monostable multivibrator 26 is driven. Here, the pulse width of the monostable multivibrator 26 is assumed to be 1,071.
Let it be s. The output of the monostable multivibrator 26 is φ, 1 in FIG. On the other hand, the transistor 35 is φ
0. is inverted and amplified, T1. to the collector. In addition, 33 is 8 pins, 34 is the base leak resistance of the transistor 35, 36 is the collector resistance of the transistor 35, and 25 is the base leak resistance of the transistor 35.
is the collector resistance of transistor 24.

When the monostable multivibrator 37 is driven by 9'-x S, the output becomes φ, 5 in FIG. φ, 7 and T4. to AND gate 28. , φ4.T, which is inverted by the inverter 27 to the AND gate 38. and φ0. If we add , we get the fifth
The differential pulse of tn1'+ tnz' in the figure is removed,
The output of 28 to AND gate I is φ, 8, AND gate 38
The output of is φ1. Therefore, the output of the OR gate 29 is φ2u
becomes.

Note that since noise is not included before LH, OR gate 2
The output of 9' becomes φ2□. As described above, the differential circuit 12
As the output of , the leading edge of the peak noise. ,.

Then, a differential output φ2o containing only n2 is obtained. Differential circuit 12
Assuming that the output of φ2. is the (x-1)Hth differential output.

Next, noise removal using the differential output will be described based on FIG. 39 and 40 are short-time delay buffers, for example, there is a 30 ns delay between the two. φ2□ in Figure 5
and 19,1 in φ2u. The phase difference is minute (for example, 1
0 ns or less), so if you look at it microscopically, as mentioned above, φ
2o is delayed by 30 S, and as the output of the buffer 10, φ
, 2 (1j), while φ, multivibrator 4
3, outputs φ2J with a pulse width of 100 S as an output, and supplies it to the AND gate 41.
The pulse at ts+tc, which is obtained by differentiating the video signal inside, is removed. To the reset input of the multivibrator 42,
The output φ1 of the horizontal oscillation AFC circuit 14. If you add
Even if the pulses obtained by differentiating the video signal and synchronization signal before and after the horizontal retrace period remain at the output JJ of the AND gate 41, the multivibrator 42 is not triggered. Assuming that the pulse width of the output φ, 4 of the multivibrator 42 is 1.2 μs, it is as shown in FIG.

A gate pulse starting from j nl l t n2 is obtained.

By the way, even if the delay from the output of the detection circuit 10 to the output of the multivibrator 42 is zero.

With φ24, there is a problem that the leading edge of the peak noise of t nl l t n2 cannot be completely removed. As a result, the delay amount of the delay circuit 17.19 is (
Δ′r+α) is required. Therefore, the number 44 of the xH is delayed by (ΔT+α) and supplied to the analog gate = 14, and the number (8) of the Therefore, the output of the delay circuit 17, that is, the xH-th signal is gated at φ24, and for example, 1.
If the output of the delay circuit 19, that is, the (x-1)t signal, is taken out as the output of the analog gate 4.1 for 2IJs, then t
It is replaced with Moe's H signal at point U, ν, which is slightly earlier than the peak noise of ni. For example, if α=200 ns, then if the tail of the peak noise from 1 is less than 11 Js, the noise is removed by the pulse width of φ24 of 1.2 μsec and replaced with an H signal of 1ijj.

In addition, in the above explanation, it was assumed that if there is a certain RF human gradient, the peak noise will not be cursed by the same radical for 2 hours in a row, but this assumption is almost impossible when the voice input is of a practical level. It is conceivable that there are q cases. Therefore, in FIGS. 3 and 5, when φ2□ is set to 1 at φ2, φ2. There are almost no cases where the differential output of the peak noise is incorrectly removed.

Also, except for diagonal lines, if it is a video, 1) I +
'+: There is almost no sense of incongruity even if the Ibo numbers of f are different.

By configuring as described above, when detecting peak noise by differentiating an image (No. 8), only the leading edge of the peak noise can be extracted and used as a gate pulse for noise removal.

Effects of the Invention As described above, according to the present invention, the differential output of only the leading edge of peak noise can be obtained and the differential output of the trailing edge can be removed, thereby preventing two differential outputs from being generated from one noise. It is possible to prevent errors in determining whether there is no fT of noise.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
3 is a detailed block diagram of the noise removal circuit in FIG. 1, FIG. 4 is a waveform diagram illustrating the operation of the differential circuit shown in FIG. 4, and FIG. 5 is a waveform diagram illustrating another operation. 12...Differential circuit, 13...Pulse processing circuit, +5
-1 t (delay line, 16. Differential circuit, 17.-Delay circuit, 18. Noise removal circuit, 19. Delay circuit 3rd F24 41st

Claims (1)

[Claims] 1. A satellite broadcast receiver that detects a satellite broadcast television signal to obtain a video signal, and a circuit that differentiates the video signal to detect peak noise in order to remove peak noise specific to FM waves; A satellite broadcasting receiver comprising: a circuit for removing differential output that appears within a certain time interval during differential output of the video signal.