JPS5857026B2 - Ghost damage wave measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In television broadcasting, the present invention provides a system in which direct waves that arrive directly from a transmitting antenna and reflected waves that arrive late due to being reflected by buildings, mountains, etc. and have taken a detour are transmitted to the same receiving antenna. This invention relates to a method for measuring ghost interference waves that are the cause of ghost interference waves on television that occur due to reception by television.

Conventionally, to quantitatively measure television ghost interference waves using direct waves as a reference, the detection output waveform of the receiver that receives those radio waves is observed with an oscilloscope, and the direct wave detection in the detection output is performed. Generally, a method has been used to measure the signal-to-interference ratio (SI ratio) as a relative value of the wave height between the output waveform and the interference detection output waveform.

However, in such a measurement method, the relative peak value of the interference detection output waveform with respect to the direct wave detection output waveform in the detection output described above is complicated due to the relative relationship between the high frequency phases of the direct wave and ghost interference wave that are received at the same time. Since the SI ratio of the measurement results changes due to changes in the SI ratio, it is necessary to accurately determine the desired wave-to-disturbance ratio (DU ratio), which is expressed by the high-frequency level ratio of the direct wave and the ghost interference wave, from the measurement results of the SI ratio. was difficult.

In other words, in order to obtain the DU ratio using the conventional measurement method described above, the installation point of the receiving antenna is moved variously in order to match the high frequency phases of the direct wave and the ghost interference wave, which are received at the same time. Since it is necessary to find the state where the high value is the maximum, measurement is extremely time-consuming and difficult to obtain accurate measured values.

Furthermore, simply guiding the detection wave output waveform of the receiver to an oscilloscope and observing it would make it difficult to observe the signal-to-noise ratio of the detection output (
If the signal-to-noise ratio (S/N ratio) is poor, the interference detection output waveform will be buried in the noise waveform and the measurement accuracy will drop significantly, so this method has a high limit on the received electric field that can measure ghost interference waves, and the measurable range is narrow. There was also a drawback.

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and measure the high frequency relative level of ghost interference waves relative to direct waves, i.e., DU It is an object of the present invention to provide a measurement method that allows the ratio and delay time to be measured accurately and easily.

That is, in the ghost interference wave measurement method of the present invention, when detecting the direct wave reception input and the ghost interference wave reception input, which are composed of the same high-frequency signal, by synchronous detection, the same waveform portion that is periodically and repeatedly included in the high-frequency signal is detected. By extracting the synchronous detection output of the synchronous detection and changing the reference detection phase in the synchronous detection with a much longer period than the repetition period of the same waveform portion, the direct wave reception input and the ghost interference wave reception input are The relative level between the two received inputs can be obtained from the extracted synchronous detection output regardless of the phase difference between the received inputs.

The present invention will be described in detail below with reference to the drawings.

An example of the basic configuration of a ghost interference wave measuring device according to the method of the present invention is shown in FIG. 1, and signal waveforms of each part thereof are shown in FIG.

In the basic configuration shown in Figure 1, the measured wave from the receiving antenna 1- is transmitted directly or after frequency conversion.
After being suitably amplified, one of the divided or branched outputs is guided to a synchronous detection circuit 5 and the other output is guided to a carrier wave generation circuit 2 in addition to a divider or branch.

A carrier wave output signal generated in a carrier wave generating circuit 2 in a phase-synchronized state with the direct wave component of the maximum amplitude among the measured waves is applied to a variable phase shifter 3, so that the phase of the carrier wave signal can be adjusted appropriately.

The phase-variable carrier wave signal is applied to the above-mentioned synchronous detection circuit 5, and the previously guided wave signal to be measured is synchronously detected by the carrier wave signal, and the wave signal to be measured is converted into a television video signal of synchronous detection output. .

When the leading edge of the vertical synchronizing signal waveform of the television video signal is enlarged, it becomes the waveform shown in FIG. 2a.

If the signal waveform observation oscilloscope is appropriately adjusted so that only the leading edge portion of the vertical synchronization signal can be repeatedly extracted and observed, the row of horizontal synchronization signal waveforms of the vertical synchronization leading edge portion can be observed.

The video signal of the synchronous detection output having the above-mentioned waveform is guided to a waveform display device 12 such as a high-performance synchroscope through the waveform processing circuit 6 so that the above-mentioned waveform can be observed. , in the waveform processing circuit 6,
A delayed signal obtained by delaying the synchronous detection output video signal by an appropriate time width At such as the slope width of the falling edge of the leading edge of the vertical synchronization pulse of 0.004H is subtracted from the original video signal, or alternatively, the synchronous detection output If the video signal waveform is differentiated as it is, the processed signal waveform of the leading edge portion of the vertical synchronization signal mentioned above that can be observed on the waveform display device 12 will become as shown in FIG. The pulse waveform in the upward or downward direction having the width of the above-mentioned delay time width At, or the set of differential waveforms in the upward and downward directions separated by the pulse width of the equalization pulse is the period of the equalization pulse, that is, horizontal synchronization. Although the pulse appears repeatedly at 1/2 of the period H of the pulse, only a downward pulse waveform appears at the leading edge of the vertical synchronizing signal, as shown surrounded by a dotted line in FIG.

Note that in the waveform processing described above, if necessary, delay subtraction and differentiation of the input video signal may be performed together to obtain a desired processed signal waveform.

Therefore, when the part shown surrounded by the dotted line in the above-mentioned figure 2 is enlarged and observed using the waveform display device 12, it is shown in figure 2C.
As shown in , the direct wave synchronous detection output pulse D, which corresponds to the falling edge of the pulse at the leading edge of the vertical sync pulse of the synchronous detection output video signal, appears most downwardly, and then the direct wave The high frequency phase difference is 90
in the up and down direction depending on whether it is greater or less than the degree, and
The synchronous detection output pulses U1 . U2゜...
...Un appears as many times as the number of arriving ghost interference waves.

Here, if synchronous detection is performed in a state where the phase of the carrier signal from the variable phase shifter 3 applied to the synchronous detection circuit 5 matches the phase of the direct wave, the synchronous detection as shown in FIG. An output waveform appears, but since the synchronous detection axis matches only the phase of the direct wave, the pulse height of the synchronous detection output pulse U for each ghost interference wave is relative to the pulse height of the synchronous detection output pulse D of the direct wave. value is,
It shows the detection output SI ratio when the detection output is reduced to a value corresponding to the cosine of the high-frequency phase difference between the direct wave and each ghost interference wave, and shows the relative level DU of the ghost interference wave with respect to the direct wave.
3 Therefore, in the measurement method of the present invention, in order to be able to directly and accurately observe the DU ratio and delay time of the ghost interference wave by the synchronous detection output waveform appearing on the waveform display device 12, , the following method is adopted.

That is, the variable phase shifter 3 that changes the phase of the carrier wave signal from the carrier wave generation circuit 2 is controlled by the control signal from the phase amount control circuit 4, and the phase of the carrier wave signal is adjusted to the field period of 1/60 seconds of the television video signal. The speed is changed slowly at a constant speed with a period much longer than that, for example, a period of 1/3 second which is 20 times that period, that is, a period of 3 Hz.

If the detection axis in the synchronous detection circuit 5 rotates at such a slow period, the synchronous detection output pulses of the direct wave and ghost interference wave will have the maximum downward wave height and the reverse phase when the detection axis is in phase, respectively. If the same maximum wave height is shown upward when The amplitude ratio of the detection output waveform U and the ghost interference detection output waveform U accurately indicates the relative value DU ratio of the received input level, and the mutual spacing on the figure is determined by the waveform display device 12 at that time. This accurately shows the delay time of the ghost interference wave relative to the direct wave, which is determined from the sweep speed.

As described above, according to the method of the present invention, the DU ratio and delay time of ghost interference waves can be measured extremely accurately and easily, but the received electric field of ghost interference waves is low,
If the S/N ratio is low, even if the synchronous detection output pulse waveform to be observed is not buried in noise, noise will be superimposed on the pulse waveform and it will not be possible to obtain accurate pulses. It becomes difficult to measure wave height.

Therefore, in the measuring device shown in FIG. 1 according to the method of the present invention, the synchronous detection output signal from the waveform processing circuit 6 is guided to the sample hold circuit 7, and the sample pulse from the sample pulse generation circuit 8 is As shown, the position of the sample pulse is shifted to extract the highest level portion of the direct wave detection output pulse D or the ghost interference wave detection output pulse U to be measured in the synchronous detection output waveform, and hold the wave height level.

At this time, the generation period of the sample pulse is made to exactly match the repetition period of the vertical synchronization pulse of the television video signal, and the pulse width of the sample pulse is appropriately adjusted according to the waveform of the ghost interference detection output pulse U to be measured. , the phase of the sample pulse is changed minutely and stably, and its position is sequentially moved, so that the synchronous detection output signal waveform at each desired position can be accurately sampled.

That is, at the beginning of the sample pulse movement,
As shown in a and e-2a, the direct wave detection output pulse D
The position of the sample pulse is aligned with the highest level part of , and the necessary signal processing described below is performed.
As shown in -1b and e-2b, the sample pulse is aligned with the highest level portion of the ghost interference detection output pulse U to be measured, and necessary signal processing is performed.

Therefore, as mentioned above, when the synchronous detection axis determined by the phase of the synchronous detection carrier signal rotates slowly at a cycle of, for example, 1/3 second, the phase difference between the wave under test and the synchronous detection carrier signal is The respective sample and hold values obtained in the vertical synchronization period according to the changes are shown sequentially in Fig. 2 e-3a and e-3b, respectively, and Fig. 2 e
-4a and e-4b, respectively, 1
It changes in a stepwise manner with a width of 1/60 seconds along a cosine waveform with a period of /3 seconds.

As signal processing for such sample and hold values, the output signal waveforms shown in FIG. 2 e-5a and e-sb of the sample and hold circuit 7 are led to the frequency selection circuit 9,
Only the 3Hz component which is the fundamental frequency component of each
When selected and extracted as shown in Figures e-6a and e-6b, respectively, the amplitude of the extracted output signal is the direct wave obtained by sample-holding the synchronous detection output signal waveform shown in Figure 2d, and the amplitude of the output signal to be measured. The maximum amplitude of the synchronized detection output signal of the ghost interference wave is proportional to each receiving input high frequency level, and the effect of rerandom noise is smoothed and removed by sample hold and frequency selection. It becomes a cosine waveform with a period of 3 Hz.

The selected output signal of the frequency selection circuit 9 is guided to an amplitude measurement circuit 10, and is further fed to a two-dimensional display circuit 11 such as a recorder.
A sweep signal that is phase-synchronized with the sample pulse from the sample pulse generation circuit 8 is applied to the other input terminal of the two-dimensional display circuit 11, and then
By sequentially changing the phase of the sample pulse from the sample pulse generation circuit 8 and sequentially moving the sample position, for example, as shown in FIG. 2 e-7 and e-8 with different sweep widths, Since a synchronous detection output pulse waveform is obtained in which the horizontal axis represents the delay time τ of the arrival of the radio wave and the vertical axis represents the high frequency level of the arriving radio wave, it is possible to directly The high frequency level ratio of the wave and the ghost interference wave, that is, the DU ratio, and the arrival delay time of the ghost interference wave can be measured extremely accurately and easily without being affected by noise.

The specific configurations of each of the circuits in the basic configuration of the ghost interference wave measuring device according to the method of the present invention shown in the first diagram can be well-known and commonly used.
Therefore, manufacturing of such a measuring device is extremely easy, and no special techniques are required for its adjustment.

It is preferable that the specific configuration of the circuit portion that produces the characteristic effects of the measuring method of the present invention is as follows.

First, as is clear from the above, the waveform processing circuit 6 for processing the synchronous detection output waveform and separating the waveforms of the direct wave detection output and the coast interference wave detection output for easy observation is a Jt delay circuit. , a combination of a polarity inversion circuit and an addition circuit, or a differentiation circuit.

In addition, since the sample pulse generation circuit 8 separates and extracts the differential waveform of the falling edge of the leading edge of the vertical synchronization pulse into a direct wave and a ghost interference wave, it generates a narrow pulse that is accurately and stably synchronized with the vertical synchronization signal. For example, the equalization pulse located just before the leading edge of the vertical sync pulse must be extracted and delayed appropriately to synchronously form a narrow sample pulse.

Further, the frequency selection circuit 9 that extracts a frequency component corresponding to the rotation period of the detection axis in the synchronous detection circuit 5 from the sample-and-hold value may be any circuit that functions as a 3Hz bandpass filter, for example, and may be an LO filter. It is configured so that a high Q value can be obtained using a small and high-performance active filter.

Therefore, the phase amount control circuit 4 and the variable phase shifter 3 that control the rotation of the synchronous detection axis described above may be configured such that the variable phase shifter 3 includes a goniometer, and its rotation is controlled by a drive signal of, for example, 3 Hz. If the motor is controlled to maintain a non-integer relationship with the vertical synchronization frequency, the pulse waveform shown in FIG. In order to further sample and hold the waveform in Figure 2d and accurately extract only the above-mentioned 3Hz component of the level change, for example, as shown in Figure 3, the incoming television radio wave is amplified and detected. Alternatively, the vertical synchronous frequency component is extracted from the subsequent synchronous detection output, and the vertical synchronous frequency component is divided to form a drive signal that maintains accurate frequency and phase stably, and the above-mentioned goniometer The drive motor can be controlled, and can also be controlled by frequency division of the crystal oscillator output.

As is clear from the above description, according to the present invention, ghost interference waves, which cause ghost interference that significantly deteriorates the received image quality of television broadcasting, are completely separated from direct waves and other ghost interference waves, and In addition, it can be sufficiently separated from receiver noise and measured accurately and easily quantitatively, making it possible to accurately and easily quantify ghost interference waves, which has been a long-awaited goal in the past. It can be extremely effective in promoting this.

In particular, by automatically rotating the detection axis in synchronous detection and automatically sweeping the synchronous detection reference phase, we have improved the measurement of coast interference waves by synchronous detection, which has been attempted in the past. Since the detection output pulse waveform that accurately represents the relative level and arrival time interval of the ghost interference wave is displayed very accurately and easily visually, the DU ratio and delay time of the ghost interference wave can be accurately and easily measured.

Furthermore, by sampling and holding the detected output pulse waveform as described above, and then extracting the automatic sweep frequency component of the above-mentioned synchronous detection reference phase from the sample-hold value, the reception effect on the above-mentioned measurement can be determined. The influence of machine noise is completely removed, and the S of the detected output pulse waveform is
Regardless of the N ratio, the DU ratio and delay time of ghost interference waves can be measured without being affected by receiver noise, and the electric field region in which ghost interference waves can be measured.

Compared to the past, it can be expanded significantly.

In addition, depending on the high-frequency phase difference between the desired wave and the ghost wave, even if the DU ratio is constant, the ghost interference appearing on the screen changes in various ways and becomes noticeable.

Therefore, if the high-frequency phase difference between the desired wave and the ghost wave is known, this high-frequency phase difference can be used as a parameter for image evaluation when evaluating received images, allowing for more realistic and rigorous numerical evaluation. This method is extremely advantageous in that it becomes possible to perform the following measurements, and the measurement of such high-frequency phase differences can be easily and accurately performed by applying the method of the present invention.

That is, the phase comparison between the automatic sweep frequency component of the above-mentioned synchronous detection reference phase, for example, the output signal of the phase amount control circuit 4 and the desired wave component signal and the ghost wave component signal, which are the selected output signals of the frequency selection circuit 9, is carried out using a well-known method. The high frequency phase difference between the desired wave and the ghost wave can be detected by calculating the respective phase differences from the reference phase.

The method for measuring ghost interference waves of the present invention described above can not only be applied extremely effectively to the measurement of coast interference waves in television broadcasting, but also to the separation measurement of reflected waves in various transmission lines that can be regarded as ghost interference waves. can be applied in exactly the same manner as described above to obtain exactly the same effect, and is extremely suitable for application to, for example, measuring reflected waves in a feeder line connecting a transmitter and a transmitting antenna. It is.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the basic configuration of a coast disturbance measurement device according to the method of the present invention, and FIG. 2 a, b
, c, d, e-1a ~ e-5a, e-1b
~e-5b, e-7, and e-8 are signal waveform diagrams respectively showing signal waveforms of the respective parts, and FIG. 3 is a block diagram mainly showing a configuration example of the phase amount control circuit. DESCRIPTION OF SYMBOLS 1... Receiving antenna, 2... Carrier wave generation circuit, 3... Variable phase shifter, 4... Phase amount control circuit, 5...・Synchronous detection circuit, 6...
... Waveform processing circuit, 7 ... Sample hold circuit, 8 ... Sample pulse generation circuit, 9 ...
... Frequency selection circuit, 10 ... Amplitude measurement circuit, 11 ... Two-dimensional display circuit, 12 ...
・Waveform display device, 13... Synchronization extraction circuit, 14
...Vertical synchronous frequency divider, 15...Drive circuit, 16...Motor.

Claims (1)

[Scope of Claims] A reference carrier wave having the same frequency as a carrier wave of an input wave modulated with a signal wave having a specific waveform portion is generated every fixed cycle, and the phase of the reference carrier wave is changed at a desired cycle longer than the fixed cycle. synchronously detect the input wave using the reference carrier wave to demodulate the signal wave, detect and store the peak value of the specific waveform portion from the demodulated signal wave, and calculate the maximum value from the stored peak value. A ghost interference wave measurement method characterized by detecting ghost interference waves. 2. The ghost interference wave measuring method according to claim 1, wherein when extracting a specific waveform portion from a signal wave, the specific waveform is delayed by a predetermined time and then inverted and added. 3. The ghost interference wave measuring method according to claim 1, wherein the peak value of the specific waveform portion is displayed and stored in an afterglow waveform display device, and the maximum value thereof is detected. 4. In detecting the maximum value from the peak value of the stored specific waveform portion, the specific waveform portion is sampled at each predetermined period and its output is held, and the desired period is determined from the sampled and held output. The method for measuring ghost interference waves according to claim 1, characterized in that the components are extracted.