JPH04100413A - Delay difference detecting system - Google Patents

Abstract

PURPOSE:To accurately measure a difference in delay between direct waves and their reflected waves in a short time by receiving a PN pattern signal transmitted from a transmitting system by means of a receiving system as the direct waves and reflected waves and detecting the correlation between the PN pattern signal and received signals while a PN pattern signal generated from the receiving system is moved on a time base on the basis of a reproduced clock. CONSTITUTION:Direct waves SS received by one antenna 31A are converted into IF signals from RF signals at a receiving section 3 and the IF signals are sent to a clock reproducing section 4 where a clock signal synchronized to the PN pattern generator 11 of a transmitting system T is reproduced. Direct and reflected waves SS and SR received by the other antenna 31B are similarly converted into IF signals from RF signals by means of the section 3 and led to a delay detecting section 5. A PN pattern generator 51 generates a PN pattern signal which is changed on the time base. By mixing the PN pattern signal with the signals from the section 3 by means of a mixer 53 and detecting the mixed signal after amplifying the mixed signal by means of an amplifier 54, the correlation between the PN pattern signal and received signals is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microwave communication system, and more particularly to a delay difference detection system for measuring reflected waves that interfere with direct waves.

[Prior Art] Generally, in the field of microwave communication, when there is a radio wave reflecting object in the transmission path between the transmitting system and the receiving system, the radio waves reflected by this reflecting object are directly transmitted from the transmitting system to the receiving system. May interfere with transmitted direct waves.

For this reason, in the receiving system, a method is adopted in which the reflected wave is recognized by detecting the delay difference between the reflected wave and the direct wave, and correct reception is performed.

Conventionally, this type of delay difference detection method connects a spectrum analyzer or a power meter to a directional antenna, and changes the angle of this directional antenna while detecting a direction in which no direct waves arrive and there is a reception input. Looking for direction. Then, a method is used in which a line is drawn on the map from the measurement point along this direction angle, the reflective object is estimated, and the delay difference between the direct wave and the reflected wave is calculated using trigonometry.

[Problem to be solved by the invention]

The conventional delay difference detection method described above estimates reflective objects on a map, so the probability that the estimated point is actually a reflective object is low, resulting in an inability to calculate accurate delay differences. There is.

In addition, if the angle between the direct wave and the reflected wave is small, the input level of the reflected wave is extremely low, or a signal of the same frequency from another line is input, the measurement of the reflected wave using a directional antenna may be incorrect. This becomes more accurate, and the measurement error of the delay difference calculated based on this measurement result becomes even larger. Furthermore, in such cases, measurement may become impossible.

An object of the present invention is to provide a delay difference detection method that enables accurate detection of delay differences.

[Means to solve the problem]

The delay difference detection method of the present invention includes a transmission system that transmits a predetermined PN pattern signal, receives this PN pattern signal, and regenerates a clock from this PN pattern signal.
It consists of a receiving system that uses this clock to correlate the direct wave and reflected wave from the transmitting system and detects the delay difference between the two waves.

The transmission system includes a modulator that generates and modulates a PN pattern signal, and a transmitter that transmits the modulated signal as a high frequency signal.

The receiving system also includes a receiving section that receives a signal transmitted from the transmitting system, a clock regenerating section that regenerates a clock synchronized with the transmitting system based on this received signal, and a PN pattern signal that generates a PN pattern signal synchronized with the transmitting system. Furthermore, it is provided with a delay detection section that moves this PN pattern signal on the time axis using a reproduced clock, correlates each of the direct wave and the reflected wave, and determines the delay difference between the two from this correlation.

Note that the delay detection section includes a PNN butter generator that generates a PN pattern signal synchronized with the transmission system, a clock shifter that moves this PN pattern signal on the time axis, and a direct wave generator that generates a PN pattern signal that is synchronized with the transmission system. and a means for correlating the reflected waves.

[Operation] According to the present invention, the PN pattern signal transmitted from the transmitting system is received as a direct wave and a reflected wave in the receiving system,
Furthermore, by correlating the PN pattern signal generated in the receiving system with the received signal while moving it on the time axis based on the reproduced clock, it is possible to determine the delay difference between the direct wave and the reflected wave.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

In the figure, a transmission system T includes a modulation section l and an antenna 21.
It is composed of a transmitting section 2 having a. In addition, the receiving system R is 2
The receiving section 3 includes two antennas 31A and 31B, a clock reproducing section 4, and a delay detecting section 5.

The modulation section 1 of the transmission system T includes a PNN butter generator 11 that generates a predetermined PN pattern signal, and a modulator 12 that modulates this PN pattern signal. In addition, the transmitter 2
is configured to convert the modulated PN pattern signal into a high frequency signal and transmit it from the antenna 21.

The receiving section 3 of the receiving system R includes two antennas 31A, 3
1B, each has bandpass filters 32A, 32B, amplifiers 33A, 33B, mixers 34A, 34B, and amplifiers 35A, 35B, and frequency conversion is performed by mixing received signals on local oscillator 360, respectively. do. Further, the clock regenerating section 4 includes a mixer 41, a voltage controlled oscillator 42, a bandpass filter 43, a wave detector 44, a low-pass filter 45, and an A/D converter 46, and one of the receiving sections 3 The clock signal is regenerated by detecting the signal received by the antenna 31A and converting it into a digital signal. Further, the delay detecting section 5 is configured to generate a PN pattern signal that is the same as the PN pattern signal generated by the transmitting system T.
NN butter generator 51, and a clock shifter 5 that shifts (shifts) the reproduced clock signal on the time axis.
2, a mixer 53 for mixing the generated PN pattern signal with the signal received by the other antenna 31B of the receiving section 5, and an amplifier 54.

In the transmitting/receiving system configured in this way, there is a reflecting object X between the transmitting system T and the receiving system R, and this reflecting object
It is assumed that a reflected wave SR is generated by .

In the transmission system T, a PN pattern signal generated by a PN pattern generator 11 is modulated by a modulator 12, and the signal is converted into a high frequency signal by a transmitter 2, and then transmitted to space through an antenna 21.

On the other hand, in the receiving system R, the two antennas 3 of the receiving section 3
1A and 31B are made to have different directivity, so that one antenna 31A can receive only the direct wave from the transmission system T, and the other antenna 31B can receive the direct wave SS and the reflected wave SR. Make it.

Then, one antenna 31. Direct wave S received at A
S is converted into an IF multiplied signal from an RF multiplied signal in the receiving section 3, and is further sent to the IF multiplied signal clock reproducing section 4, where a clock signal synchronized with the PN pattern generator 11 of the transmitting system T is regenerated. Ru.

Further, the direct wave SS and reflected wave SR received by the other antenna 31B are similarly converted from RF multiplied signals to IF multiplied signals in the receiving section 3, and guided to the delay detection section 5. In this delay detection section 5, the clock signal regenerated by the clock regeneration section 4 is changed on the time axis in a clock shifter 52,
From the PNN butter generator 51, P is changed on the time axis.
Generate N pattern signals. Then, this PN pattern signal and the signal from the receiving section 3 are mixed in the mixer 53, and the mixed signal is amplified in the amplifier 54 and detected, thereby detecting the correlation between the PN pattern signal and the received signal. do.

Therefore, first, while gradually making clock knots, P
By correlating the PN pattern signal from the NN butter generator 51 with the received direct wave SS, and further correlating the PN pattern generated signal without Cronk shift with the reflected wave SR, the direct wave SS and It becomes possible to obtain the shift amount in the clock shifter 52 between the reflected wave SR and the time difference between the two, and it becomes possible to obtain the delay difference between the direct wave and the reflected wave from this time difference.

〔Effect of the invention〕

As explained above, the present invention provides P
The N pattern signal is received as a direct wave and a reflected wave in the receiving system, and the PN pattern signal generated in the receiving system is moved on the time axis based on the reproduced clock to correlate with the received signal. , when the angle between the direct wave and the reflected wave is small, when the input level of the reflected wave is low, when a signal of the same frequency from another line is input, etc.
This has the effect of being able to measure the delay difference between the direct wave and the reflected wave accurately and in a short time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. T...transmission system, R...reception system, SS...direct wave,
SR...Reflected wave, X...Reflecting object, 1...Modulation section,
2... Transmission section, 3... Receiving section, 4... Clock regeneration section, 5... Delay detection section, 11... PN pattern generator, 12... Modulator, 21... antenna, 31A
, 31B...Antenna, 32A, 32B...Band filter, 33A, 33B...Amplifier, 34A, 34B...
...Mixer, 35A, 35B...Amplifier, 36...
Local oscillator, 41... Mixer, 42... Voltage controlled oscillator, 43... Bandpass filter, 44... Detector, 45
...Low-pass filter, 46...A/D converter, 51...
・PN pattern generator, 52...clock shifter,
53...Mixer, 54...Amplifier.

Claims (1)

[Claims] 1. A transmission system that transmits a predetermined PN pattern signal, receives this PN pattern signal, regenerates a clock from this PN pattern signal, and uses this clock to generate a direct wave from the transmission system. and a receiving system that correlates each of the reflected waves and detects the delay difference between the two waves. 2. The transmission system includes a modulation section that generates and modulates a PN pattern signal, and a transmission section that transmits this modulated signal as a high frequency signal, and the reception system receives the signal transmitted from the transmission system. a clock regenerating section that regenerates a clock synchronized with the transmitting system based on the received signal; 2. The delay difference detection method according to claim 1, further comprising: a delay detection section that is moved above to take a correlation with each of the direct wave and the reflected wave, and calculates a delay difference between the two from this correlation. 3. The delay detection section includes a PN pattern generator that generates a PN pattern signal synchronized with the transmission system, a clock shifter that moves this PN pattern signal on the time axis, and this P
3. The delay difference detection method according to claim 2, further comprising means for correlating the N pattern signal with the received direct wave and reflected wave.