JPS6218195A - Method and apparatus for measuring adjacent interference - Google Patents

Abstract

PURPOSE:To improve the accuracy and to reduce the measuring time by using a spectrum analyzer to measure electrically the interference level thereby reduc ing the errors of measurement. CONSTITUTION:In conducting measurement, a signal generator 1 is matched with a video carrier 20kHz of a channel desired for measurement and 30% AM modulation is applied. Then a signal generator 2 is applied with 30% AM modulation of 20kHz and the channel is matched with the video carrier of the adjacent channels. Then a spectrum analyzer 5 measures 20kHz in the detection output of the generator 1 to use it as a reference and the output of the generator 2 is adjusted while the 20kHz of the detected output of the generator 2 is being measured. That is, the output where the 20kHz level is -46dB with respect to the reference level is obtained and the output difference between the generators 1 and 2 is takes as the adjacent interference ratio. Then the accuracy is increased the measuring time is reduced with less errors by measuring the value while the output of the generator 1 is matched with the RF level and changed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for measuring adjacent interference in television receivers.

BACKGROUND OF THE INVENTION In recent years, with the increase in the number of CATV and broadcasting stations, it has become important to evaluate the ability of television receivers to eliminate adjacent interference.

This evaluation is conventionally provided in JIS6101, and is shown in FIG. In FIG. 4, the two-signal generator is a device that generates a video carrier wave and an audio carrier wave. 21 is a video signal generator which generates a vertical stripe force as shown in FIG.
The video compensator 22 outputs a color bar' signal, shown in Figure 6, which modulates the video carrier of two signal generators 23, 24, respectively. The signal is input to the television receiver 26 through a two-signal pad 25, which is a combiner of two two-signal generators.

The measurement method is to match the two signal generators 23 to a desired carrier wave. Next, the two signal generators 24 are tuned to the carrier waves of adjacent channels. The input of the two-signal generator 24 at the point where no interference is detected in the television receiver is obtained, and the difference from the desired signal is taken as the adjacent interference ratio. This is done by changing the inputs of the two signal generators 23.

Problems to be Solved by the Invention However, with the above method, there are many errors in the measured values due to individual differences among the measurers, surrounding conditions, etc. Another problem was that the measurement time was long.

The present invention aims to reduce errors in measured values, improve accuracy, and shorten measurement time.

Means for Solving the Problems To achieve this object, the present invention measures the level of interference electrically using a spectrum analyzer. Also, the detection limit is -46 interference level compared to the reference value.
dB.

Function As a result, since the measured values are obtained using a spectrum analyzer, there are fewer errors and the measurement time is shorter than that of human eyes.Example An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a wiring diagram showing an embodiment of the method for measuring adjacent interference according to the present invention. The signal generator is 100
AM whose frequency can be varied from KHz to 1000 MHz
It can be modulated. A spectrum analyzer with a resolution of up to 100 Hz is used.

The measurement method uses two signal generators 1 and 2 as shown in Figure 1.
RF of the television receiver 4 using the two signal mixer 3
input to the terminal. The input of the spectrum analyzer 5 is a tuner 6°, an IF amplifier 7. Detection circuit 8
1 from the detection output of the television receiver obtained through
: Pass through one probe. Note that 9 is a demodulation matrix.

First, set the signal generator 1 to the video carrier wave of the channel you want to measure at 20 KHz and 30% A as shown in Figure 2.
Performs M modulation. The 20 KHz level of the detection output is measured by the spectrum analyzer 5 and used as a reference value. Next, the modulation of signal generator 1 is turned off, and signal generator 2 similarly performs 20 KHz 30% AM modulation to match the video carrier wave of the adjacent channel. The output of the signal generator 2 is adjusted while measuring the 20 KHz level in the detection output with the spectrum analyzer 5, and the output at the point where the 20 KHz level is -46aBJlc with respect to the previously determined reference value is determined. Let the difference in output between signal generators 1 and 2 be the adjacent interference ratio. This is measured while changing the output of the signal generator 1 according to the RF level.

As described above, according to this embodiment, by measuring the interference level with the spectrum analyzer 5, it is possible to improve the measurement accuracy and shorten the measurement time.

In this example, the modulation frequency is 20 KHz.
GaN Futian country fake feudal arrival/yl Dou Sang 11 Ren = 4 Bo'RT Taihi and Nijobi both l θ) 11 White 18 - Effects of the Invention As described above, the present invention uses a spectrum analyzer. However, the following excellent effects can be achieved.

(b) Measurement accuracy can be improved.

(b) Measurement time can be reduced to 5% compared to conventional methods.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram embodying the method for measuring adjacent interference in an embodiment of the present invention, Fig. 2 is a modulation waveform diagram showing the modulation method of the signal generator, and Fig. 3 shows the measurement points. FIG. 4 is a wiring diagram embodying the conventional measurement method, and FIGS. 5 and 6 are signal waveform diagrams used for measurement. 1.2...signal generator, 3...2 signal mixer, 4...television receiver. 5...
...Spectrum analyzer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) A first signal generator capable of variable frequency and AM modulation, a second signal generator having the same functions as the first signal generator, and each of the first and second signal generators. and a two-signal mixer whose output is an input, the output of the two-signal mixer is connected to the RF terminal of the measurement television receiver, and the detected output of the measurement television receiver is 1:1. A device for measuring adjacent interference that is input to a spectrum analyzer via a probe. (2) A first signal generator capable of variable frequency and AM modulation, a second signal generator having the same functions as the first signal generator, and each of the first and second signal generators. and a two-signal mixer whose output is input, the output of the two-signal mixer is connected to the RF terminal of the measurement television receiver, and the detected output of the measurement television receiver is connected to a 1:1 probe. The first signal generator is configured to input the output level of the adjacent channel to the spectrum analyzer, determine the measurement reference value of the channel to be measured with the first signal generator, and switch to the second signal generator to input the output level of the adjacent channel to the first signal. A method for measuring adjacent interference in which the adjacent interference ratio is measured based on the difference between the output levels of first and second signal generators, while controlling the generator while comparing it with a standard.