JPS6324336B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a method for detecting the amount of cross-polarized waves generated in a transmission frequency band between a moving object and a fixed station in the field of wireless communication, when the distance between the moving object and the fixed station changes. The present invention relates to a cross-polarized wave measuring device that detects the amount of cross-polarized wave generation with high accuracy by automatically compensating for the deterioration in detection accuracy caused by the above.

Conventionally, this type of device has collected the cross-polarization characteristics of an antenna device by receiving radio waves from a ground calibration device. However, this method using radio waves from a ground calibration device includes measurement errors such as ground reflection, and is unsuitable for antenna devices that have high-accuracy cross-polarization discrimination, which is required in recent years in orthogonal polarization feeding systems. be. For this purpose, an unmodulated carrier wave and a carrier suppressed modulated wave modulated by the first low frequency signal are input to two orthogonal polarization input terminals of the power supply device of the antenna under test, and the polarization characteristics of the antenna under test are The mixed polarization components are returned to the moving object and received again, and the phase and amplitude components of the cross-polarization components relative to the main polarization components are separated.
To detect. However, this cross-polarized wave component is received on the transmitting side after a delay time between transmission and reception has elapsed after it is generated, and it is clear that it changes depending on the orbital state of the satellite.

Conventional cross-polarization measurement equipment in the transmission frequency band does not compensate for the delay time between transmission and reception.
It is necessary to adjust the phase of a circuit that synchronously detects cross-polarized components included in low-frequency components in response to changes in the trajectory of a moving object, making accurate and easy-to-operate measurements impossible. It had drawbacks such as.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it modulates the signal transmitted as the main polarization component not only with the conventional unmodulated carrier wave but also with a second low frequency signal. The second low-frequency signal is used as a carrier wave residual signal, and the second low-frequency signal detects the phase difference between transmitting and receiving that varies due to changes in the delay time between transmitting and receiving, and uses this phase difference signal to synchronously detect cross-polarized components. The objective is to measure cross-polarized waves in the transmission frequency band with high precision by automatically adjusting the low-frequency signal and eliminating the need for phase adjustment.

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a carrier wave generator. The carrier wave generated by the carrier wave generator 1 is modulated by the second low frequency signal 30 generated from the synchronization section 24 in the carrier wave residual modulator 2, and becomes a residual carrier wave 27 and a sideband wave 28, which are sent to the transmission wave band feeding section 4. is input. On the other hand, the carrier wave also generated by the carrier wave generator 1 is transmitted to the first low frequency signal 31 generated from the synchronization section 24 in the carrier wave suppression modulator 3.
The modulated signal becomes a sideband wave 29, which is also input to the transmission waveband feeder 4 and becomes a cross component with respect to the sideband wave 28. These residual carrier waves 27 sideband waves 28,
29 indicates that when passing through the transmitting antenna 5, residual carrier waves 27, sideband waves 28, 29, and deterioration due to the polarization characteristics of the transmitting wave band feeding section 4 and the transmitting antenna 5 are mixed, and the transmitted wave 25 is sent to the receiving antenna of the moving object. 6, the frequency converter 7 and the transmitting antenna 8, and the received wave 26 is received by the receiving antenna 9. Here, it is clear that the transmitted wave 25 and the received wave 26 undergo a change in propagation time (ROUND TRIP TIME) due to a change in the orbit of the moving object. The received wave 26 received by the receiving antenna 9 is commonly amplified by the receiving waveband feeding unit 10, the receiving frequency converter 11, the first intermediate frequency amplifier 13, and the second intermediate frequency converting amplifier 14, and only the component related to the residual carrier wave 27 is narrowed. After separation by band filter 15, reference signal detection section 16, loop filter 20, voltage controlled oscillator 21
to form a phase-locked loop and an automatic gain control loop to normalize the cross-polarized signal. The cross-polarized components of the sidebands 28 and 29 distribute the same second intermediate frequency signal from the second intermediate frequency conversion amplifier 14;
The phase detector 17 phase-detects the in-phase component of the intermediate frequency signal using the reference phase signal 36 as a reference, and the phase detector 18 uses the reference phase signal 36 as a reference to detect the in-phase component of the intermediate frequency signal. The orthogonal phase components of the frequency signal are detected and the synchronization unit 2
A third low frequency signal 32 having the same frequency as the first low frequency signal 31 which has been phase compensated from 4 is synchronously detected by the synchronous detectors 22 and 23, smoothed, and orthogonal to the DC output 34 which is in phase with the main polarization component. DC output 35
Detect. A reference phase signal 36 having the same frequency and whose phase is adjusted is input to the phase detectors 17, 18, 19 and the reference signal detection section 16. Here, in order to detect the delay time between transmission and reception, the component of the second low frequency signal 30 is similarly detected from the second intermediate frequency conversion amplifier 14, and after phase detection by the phase detector 19, the delay time between transmission and reception is detected. phase shifted second
The fourth low frequency signal 33 having the same frequency as the low frequency signal 30 is input to the synchronization circuit 24, and the phase difference between the second low frequency signal 30 and the fourth low frequency signal 33 is measured. A delay time corresponding to this phase difference is added to the first low frequency signal 31 by the synchronization circuit 24 to form a third low frequency signal 32. The transmitting antenna 5 and the receiving antenna 9, the transmitting wave band feeding section 4 and the receiving wave band feeding section 10, and the receiving antenna 6 and the transmitting antenna 8 are configured separately for transmitting and receiving, respectively, but they can be used as a shared antenna or a shared feeding section. Even if the configuration is configured, the gist of the present invention will not be changed.

Here, the first low frequency signal 31 and the second low frequency signal 30 are signals with different frequencies that are phase synchronized with each other, and if the frequency of the first low frequency signal 31 is the ce frequency, then the second low frequency signal 30 is The frequency of the signal 30 is N/M·ce frequency. Here, M and N are integers that are mutually prime numbers.

The principle of detecting the amount of cross polarization generated in the present application will be explained with reference to FIGS. 3 to 8.

3 is a frequency spectrum diagram of the input signal of the second intermediate frequency conversion amplifier 14, and FIG. 4 is a frequency spectrum diagram of the output of the filter 15.

Second intermediate frequency conversion amplifier 14, filter 1
5, reference signal detection section 16, loop filter 20,
The input signal shown in FIG. 3 is frequency-converted by the second intermediate frequency conversion amplifier 14 by the phase-locked loop composed of the voltage-controlled oscillator 21, and the first and second low frequency components are suppressed by the filter 15. The carrier wave shown in FIG. 4 is phase-locked to the reference phase signal 36. The phase detectors 17 and 18 phase-detect the first low frequency signal shown in FIG. 5 using the reference phase signal 36 shown in FIG. 6 as a reference phase. Reference phase signal 36
is phase-locked to the carrier center of the input signal by a phase-locked loop. Phase detector 17 or 18
FIG. 7 shows the time-domain waveform of the phase-detected output. The reference phase signal 36 and the first low frequency signal are:
Since the frequencies and phases are shifted, the detected output has a beat waveform as shown in FIG. When the detection output of FIG. 7 is synchronously detected using the third low frequency component 32 of FIG. 8b as a reference, the synchronous detection output shown in FIG. 8a is obtained.

The synchronous circuit will be explained using FIG. Only one of the orthogonal component and the in-phase component of the cross-polarized wave component having the frequency of the first low-frequency signal 31 will be explained. The state of detection by the synchronous detectors 22 and 23 shown in FIG. 1 is shown in FIG. 2 by taking ON/OFF half-wave rectification by switching as an example. A shows the correct phase state of synchronous detection where the detection sensitivity is maximum, and b shows the situation when the moving object moves from the state of a and there is no phase compensation in the synchronization circuit 24, that is, the state of the conventional measuring device.
c is the timing of synchronous detection, which is calculated by the synchronization circuit 24 by the change in delay time between transmission and reception between a and b.
This shows a state in which synchronous detection is performed with a phase shift of Tr. Therefore, in b, the detection sensitivity has decreased to 100·COSθe. Here, the modulation signal is a sine wave, but
The modulation signal may be a pulse wave that is a rectangular wave. However, in that case, the sensitivity decrease at b is 100・(1−
θr/90). This decrease in detection sensitivity can be reduced by setting the frequency ce to a very low frequency, but this is difficult because it is limited by the bandwidth of the receiving phase-locked loop.

In the above embodiment, the measurement of cross-polarization in the transmission waveband of the antenna was described, but it may also be used to detect the control voltage of the cross-polarization compensator due to rain or the like occurring in the transmission waveband.

This communication polarization compensator includes synchronous detectors 22, 2
The DC outputs 34 and 35 obtained from the transmitter 3 control the retardation plate in the transmission waveband power supply unit 4.

Further, the frequency ratio M:N between the first low frequency signal 31 and the second low frequency signal 30 does not necessarily have to be a prime number ratio, and may be one that does not interfere with each other in practical terms. In addition, the first and second low frequency signals 31,
The same purpose can be achieved by using the same frequency for 30 and performing different PN code modulation to prevent mutual interference.

As described above, according to the present invention, by adding a synchronization circuit, it is possible to perform highly accurate transmission waveband cross-polarization measurement without requiring any operation.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing an embodiment according to the present invention, FIG. 2 is a waveform diagram for explaining FIG. 1, and FIG. 3 is a frequency spectrum diagram of the input signal of the second intermediate frequency conversion amplifier 14. 4 is a frequency spectrum diagram of the output signal of the filter 15 in FIG. 2, FIG. 5 is a frequency spectrum diagram of the input signal of the phase detector, FIG. 6 is a frequency spectrum diagram of the reference phase signal of phase detection, and FIG. The figure is an output waveform diagram of the phase detector, and FIG. 8 is a waveform explanatory diagram of synchronous detection. In the figure, 1 is a carrier wave generator, 2 is a carrier wave residual modulator, 3 is a carrier wave suppression modulator, 4 is a transmission band feeding section, 5 is a transmission antenna, 6 is a receiving antenna of a moving object, and 7 is a frequency of a moving object Converter, 8 is a transmitting antenna of a moving object, 9 is a receiving antenna, 10 is a receiving waveband feeding section, 11 is a receiving frequency converter, 1
2 is a local signal oscillator, 13 is a first intermediate frequency amplifier, 14 is a second intermediate frequency conversion amplifier, 15 is a narrow band filter, 16 is a reference signal detection section, 17, 1
8 and 19 are phase detectors, 20 is a loop filter,
21 is a voltage controlled oscillator, 22 and 23 are synchronous detectors, and 24 is a synchronous circuit. In addition, 30 is a second low frequency signal, 31 is a first low frequency signal, and 32 is a third low frequency signal.
33 is a fourth low frequency signal.

Claims (1)

[Claims] 1 A first sideband signal obtained by suppression modulating a carrier signal with a first low frequency signal and a second sideband signal obtained by residual modulating the carrier signal with a second low frequency signal are cross-polarized. a transmitter that transmits the cross-polarized wave signal as a wave signal; a receiver that detects a component signal having the same frequency as the second low-frequency signal from a received signal in which the cross-polarized signal is received via a target; and a second low frequency signal, and the second low frequency signal.
and a component signal having the same frequency as the second low frequency signal, and a third low frequency signal that is obtained by delaying the first low frequency signal by a delay time corresponding to this phase difference. a synchronous circuit that generates a signal, and a synchronous circuit that generates a signal from the received signal using the third low frequency signal.
and a synchronous detector that synchronously detects a second sideband signal.