JPH10294952A - Interference reduction circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce FSC signal input interference by tuning and setting the filter frequency of a PAL/NTSC multi-mode digital comb filter interference reduction circuit to the respective FSCs of the FSC (sub carrier) of PAL and the FSC of NTSC. SOLUTION: This circuit constituted of a PAL/NTSC switching transistor 5 and a protective resistor 31 is turned off by PAL/NTSC control signals, the filter frequency constituted of elements 15, 28, 20, 21 and 29 is tuned to the FSC of the PAL and the FSC signal input interference of the PAL is reduced. The circuit constituted of the PAL/NTSC switching transistor 4 and the protective resistor 30 is turned off, the filter frequency constituted of the elements 14, 26, 18, 19 and 27 is tuned to the FSC higher harmonic interference frequency of the PAL and the FSC signal input higher harmonic interference of the PAL is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a PAL / NTSC multimode digital comb filter interference mitigation circuit for a television receiver.

[0002]

2. Description of the Related Art A conventional PAL / NTSC multi-mode digital comb filter interference mitigation circuit will be described below.

FIG. 2 shows a PAL of a conventional television receiver.
/ NTSC multi-mode digital comb Filter interference mitigation circuit. In FIG. 2, 1 is PAL / NTS
C multi-mode digital comb filter, 2, 3
Is an emitter follower transistor, 6, 7 are pull-up resistors, 8, 9, 10, 11 are bias resistors, 12, 1
3 is a filter resistor, 16 and 17 are filter coils 2
2, 23, 24 and 25 are filter condensers.

[0004]

However, in the above conventional configuration, in the PAL / NTSC multi-mode, the PAL FSC (subcarrier) and the NTSC FS
The filter frequency of the filter interference mitigation circuit cannot be set for each FSC (subcarrier) of C (subcarrier), and the FSC (subcarrier) of PAL
, And the filter frequency of the filter disturbance reduction circuit is set between FSC (subcarrier) of NTSC and dot disturbance as FSC (subcarrier) signal input disturbance given to the luminance signal output in the PAL / NTSC multi-mode digital comb filter. Becomes
Also, harmonic interference occurs as FSC (subcarrier) signal input interference applied to the chroma signal output.

[0005]

In order to solve this problem, the present invention provides a PAL / NTSC multi-mode digital comb filter which reduces the filter frequency of an interference reduction circuit by using a PAL FSC (subcarrier) and an NTSC FSC.
The interference is mitigated by setting in synchronization with each FSC (subcarrier) of the SC (subcarrier).

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claims 1, 2 and 3 of the present invention is directed to a PAL / NTSC multi-mode digital comb filter circuit which outputs a luminance signal and a FSC (sub Carrier) has the effect of reducing signal input interference.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 shows a PAL / NTSC multi-mode digital comb filter interference mitigation circuit of a television receiver of the present invention, 1 is a PAL / NTSC multi-mode digital comb filter, 2, 3 are emitter follower transistors, 6, 7 are pull-up resistors,
8, 9, 10, 11 are bias resistors, 12, 13, 1,
4, 15 are filter resistances, 16, 17, 18, 1
9, 20, 21 are filter coils, 22, 23, 2
Reference numerals 4, 25, 26, 27, 28 and 29 denote filter capacitors, reference numerals 4 and 5 denote PAL / NTSC switching transistors, and reference numerals 30 and 31 denote protection resistors.

The operation of the PAL / NTSC multi-mode digital comb filter interference mitigation circuit of the television receiver configured as described above will be described with reference to FIG.

First, an FSC (subcarrier) signal input disturbance reduction circuit for giving a luminance signal output at the time of PAL image reception is a PAL / NTSC switching transistor and a protection resistance circuit of 31 PAL / NT.
It is turned off by the SC control signal, 15, 28, 20,
The filter frequency composed of 21 and 29 is tuned to the PSC FSC (subcarrier), and the PAL FSC (subcarrier) signal input interference is reduced to provide a luminance signal processing circuit with transistors composed of 10, 11 and 3. And proceed. On the other hand, the FSC (subcarrier) signal input harmonic interference mitigation circuit applied to the chroma signal output is a PAL / NT of 4
A circuit composed of an SC switching transistor and 30 protection resistors is turned on by a PAL / NTSC control signal.
FF, the filter frequency composed of 14, 26, 18, 19, 27 is tuned to the PAL FSC (subcarrier) harmonic interference frequency, and the PAL FSC (subcarrier) signal input harmonic harm is reduced to 8, The process proceeds to the chroma signal processing circuit by the transistors composed of 9 and 2.

Next, an FSC (subcarrier) signal input disturbance reduction circuit for giving a luminance signal output at the time of NTSC image reception is a circuit composed of 5 PAL / NTSC switching transistors and 31 protection resistors.
It is turned on by the SC control signal, shorts the 21 coil, and the filter frequency composed of 15, 28, 20, 29 is tuned to the FSC (subcarrier) of NTSC,
The NTSC FSC (subcarrier) signal input interference is reduced, and the process proceeds to the luminance signal processing circuit by the transistors composed of 10, 11, and 3. On the other hand, the FSC (subcarrier) signal input harmonic interference mitigation circuit applied to the chroma signal output is constituted by four PAL / NTSC switching transistors and thirty protection resistors are provided by PAL / NT.
It is turned on by the SC control signal and shorts 19 coils, the filter frequency composed of 14, 26, 18 and 27 is tuned to the FSC (subcarrier) harmonic interference frequency of NTSC, and the FSC (subcarrier) signal of NTSC The input harmonic damage is reduced, and the process proceeds to the chroma signal processing circuit by the transistors composed of 8, 9, and 2.

[0011]

As described above, according to the present invention, PAL /
Digital Com's FSC in NTSC Multimode
An advantageous effect of reducing (subcarrier) signal input interference and FSC (subcarrier) signal input harmonic damage is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an interference mitigation circuit of a television receiver according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional interference reduction circuit of a television receiver.

[Explanation of symbols]

1 PAL / NTSC Multimode Digital Com
Filter 2-3 Emitter follower transistor 4-5 PAL / NTSC switching transistor 6-7 Pull-up resistor 8-11 Bias resistor 12-15 Filter resistor 16-21 Filter coil 22-29 Filter capacitor 30-31 Protection resistor

Claims (3)

[Claims] 1. A PAL / NTSC multi-mode digital comb filter circuit for PAL FSC (sub-carrier) signal interference and NTSC FSC (sub-carrier) signal interference, and a filter frequency of the interference reduction circuit is set to PAL FSC (sub-carrier). NTSC FSC
Each FSC (subcarrier) of (subcarrier)
An interference mitigation circuit for a television receiver, which is set in synchronization with 2. A PA applied to a luminance signal output of a PAL / NTSC multi-mode digital comb filter circuit.
L FSC (subcarrier) signal interference and NTSC
FSC (subcarrier) signal interference The filter frequency of the interference mitigation circuit is set to PAL FSC (subcarrier) and NT
An interference mitigation circuit for a television receiver, wherein the FSC (subcarrier) of the SC is set in synchronization with each FSC (subcarrier). 3. The P signal applied to a chroma signal output of a PAL / NTSC multi-mode digital comb filter circuit.
AL FSC (subcarrier) signal jamming and NTSC
The FSC (subcarrier) signal interference is reduced by setting the filter frequency of the interference mitigation circuit to PAL FSC (subcarrier) and N
FSC of each FSC (subcarrier) of TSC
An interference mitigation circuit for a television receiver, which is tuned to (subcarrier).