JPS61131636A - Polarized wave multiplex radio communication system - Google Patents

Abstract

PURPOSE:To decrease a setting-disable time by applying a frequency offset to one of polarized waves of the orthogonal polarized wave communication system. CONSTITUTION:The oscillation frequency of a local oscillator 11 or 12 is offset within a capture range of a demodulator in advance. For example, when the oscillation frequency of one local oscillator is shifted by nearly 100kHz to that of the other local oscillator, the time requiring the 90 deg. phase rotation is quickened to nearly 10musec in comparison with nearly 1sec without the offset.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polarization multiplexing wireless communication system, such as a quadrature amplitude modulation (QAM) communication system, which improves the frequency utilization efficiency of microwave digital communication. In particular, in polarization multiplexing wireless communication systems that have a cross-polarization discrimination compensation circuit in the receiving device,
The present invention relates to a transmitting device including means for applying a frequency offset during signal transmission.

[Conventional technology]

In microwave digital communications, orthogonal polarization communication systems that use two orthogonal polarized waves are attracting attention.

In order to effectively utilize frequencies by sharing this orthogonal polarization,
Improving cross-polarization characteristics of the antenna system and improving cross-polarization discrimination (CrossPolariz) by fading
ation Discrimination: X
If the deterioration of PD) is significant, it is necessary to compensate for it. Deterioration of cross-polarization discrimination, that is, cross-polarization interference, occurring in a radio wave propagation path is caused by anisotropic phase shift (DPS) and anisotropic attenuation (DA) during fading. Therefore, in systems that require high cross-polarization discrimination, a cross-polarization discrimination compensation circuit (
XPIC) is required.

This cross-polarized wave discrimination compensating circuit is a system in which a reception side device correlates an error signal corresponding to an interference bone with a data signal, controls a variable coupler, and removes cross-polarized wave interference. In order for this cross-polarization discrimination compensation circuit to operate stably,
When the phase of the error signal changes due to a change in the phase difference of the reproduced carrier signal, it is necessary to correct the error signal so that it has a correct correlation with the data signal. To do this, it is necessary to provide a means for detecting the phase relationship of each reproduced carrier signal, obtain an error signal corrected according to the phase difference of the reproduced carrier signals, and then It is necessary to provide a means for correctly correlating regardless of the phase relationship between each reproduced carrier signal and the demodulator (
(Refer to Japanese Patent Laid-Open No. 59-112739, "Cross Polarization Interference Elimination Circuit").

[Problem that the invention seeks to solve]

However, such conventional cross-polarization interference cancellation circuits
By detecting the phase relationship between two demodulator outputs corresponding to two orthogonal polarized waves and correcting the error signal obtained as a result, the signal is always maintained no matter how the phase difference of the reproduced carrier signal changes. This is a method that allows normal operation to occur. Therefore, it depends on the phase difference detection ability of the means for detecting the phase from the two demodulator outputs. For example, if the phase difference is 0°, 90',
In the very vicinity of 180° or 270°, determination may become impossible.

Furthermore, if a phase rotation occurs in the received signal due to a change in delay time due to fading, for example, and if it fluctuates in a fluctuating manner, the phase detection indeterminable region may extend for a long time (several seconds).

The present invention has been made by focusing on such conventional problems, and the present invention is made by focusing on the problem of the conventional technology. Another object of the present invention is to provide a polarization multiplexing wireless communication system that makes it possible to almost ignore the time during which phase difference determination becomes impossible.

[Means for solving problems]

The present invention is characterized in that a frequency offset is applied to the local oscillator of the transmitter for both polarizations.

That is, the first invention of the present invention includes a transmitting device including means for transmitting a radio wave signal in which different information is modulated on intersecting polarized waves, and a plurality of demodulating means for receiving this radio wave signal and demodulating it for each polarized wave. and a receiving device including means for removing cross-polarized interference using the output of the demodulating means, the transmitting device is arranged such that the carrier frequencies of the crossed polarized waves are slightly different from each other. They are characterized by different configurations.

This slight difference in carrier frequency may be within the demodulator capture range.

A second aspect of the present invention is a transmitting device including means for transmitting a radio signal in which different information is modulated on intersecting polarized waves, a plurality of demodulating means for receiving the radio signal and demodulating it for each polarized wave, In the polarization multiplexing wireless communication system, the transmitting device has a polarization multiplexing wireless communication system including a receiving device including means for removing cross-polarization interference by the output of the demodulating device, and the transmitting device has an output frequency that is within the demodulator capture range according to the control signal. The present invention is characterized by comprising a local oscillator that changes slightly within the range of , and a detection circuit that detects a modulation signal input and sends the detected output to the local oscillator as the control signal.

[For production]

The first invention speeds up the phase rotation between the polarized waves by applying a frequency offset to the local oscillators of the transmitting devices for both polarized waves within the demodulator capture range in advance. Therefore, the phase detection means on the receiving side can almost ignore the time during which it cannot make a determination, and stable operation of the cross-polarization interference removal circuit is established.

The second invention changes the oscillation frequency of the local oscillator in response to the modulated input signal of one or both of the polarized waves transmitting device, and can easily obtain the frequency offset between the two polarized waves.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the first aspect of the present invention. In FIG. 1, modulated waves (intermediate frequency signals) are input to input terminals 10 and 20, and microwave signals to be transmitted are output to output terminals 19 and 29, respectively. Input terminal 10.20 and output terminal 19.29
Frequency converters 12.22 and amplifiers 13.2 each receive the output of local oscillators 11.21 as inputs.
3 is connected.

The oscillation frequency of the local oscillator 11 or 21 is offset in advance within the demodulator capture range. For example, if one local oscillator is shifted by about 100 kHz relative to the other local oscillator, the time required to rotate the phase by 90'', which was approximately 1 second without offset, will be reduced to approximately 10 microseconds. speed (can be rotated).

However, when performing frequency offset, the first invention uses a method in which the carrier frequency of the modulator or the frequency of the local oscillator of the transmitter is offset in advance, but the adjustment is quite complicated and the line Confusion is likely to occur in maintenance or equipment manufacturing management.

Therefore, the second invention is characterized in that it includes means for applying a frequency offset only when a modulated signal is input to the transmitter. Therefore, since the configuration circuits of the transmitter for both polarizations are of the same standard (device manufacturing management can be extremely simplified).

FIG. 2 is a block configuration diagram illustrating an embodiment of the second invention. In Figure 1, input terminal 10.2
A modulated wave (intermediate frequency signal) is input to each terminal 0, and a microwave signal to be transmitted is outputted to each output terminal 19 and 29. Input terminal 10.20 and output terminal 19.
Frequency converters 12.22 and their amplifiers 13.23, each receiving the output of the local oscillator 11.21, are connected between the frequency converters 12.29 and 29. Further, one of the transmitting devices is configured such that the input signal is branched and connected to a modulated signal detector 14, and the output of this modulated signal detector 14 controls the oscillation frequency of the local oscillator 11.

A modulated signal is input from input terminal 10.20, mixed with the output of local oscillator 11.21 by frequency converter 12.22, converted into a microwave band, amplified by amplifier 13.23, and sent to output terminal 19.29. The signal is sent to each polarization input terminal of the antenna system. - Here, the feature of the second invention of the present invention is that the modulated signal detector 14 in one transmitting device determines whether or not a modulated signal is input, and if there is a modulated input signal, A control signal for offsetting or wobbling the local oscillation frequency is output to the local oscillator 11.

Therefore, by providing one transmitter with the modulation signal detector 14 and the local oscillator 11 whose oscillation frequency is controlled by its output control signal, a frequency offset can be easily applied.

In this embodiment, an example of a heterodyne system is shown, but in the case of a direct modulation system, the frequency converters 12 and 22 become microwave band modulators, and the input signal becomes a digital signal.

In addition, in this embodiment, the shift amount of the frequency offset is 10
Although an example of 0 kHz is shown, any frequency offset that allows the phase to be rotated at high speed so that the time is sufficiently shorter than the detection time constant of the phase difference detection means of the cross-polarization interference removal circuit may be used.

In addition, in the present invention, the local oscillation frequency of the transmitting device is offset or wobbled, but when using an intermediate frequency band modulator, a method of similarly offsetting or wobbling the carrier wave by determining the presence or absence of an input data signal is required. The present invention can also be carried out using the following methods.

〔Effect of the invention〕

The present invention speeds up the phase rotation of the error signal by applying a frequency offset to one of the two polarized waves in the orthogonal polarization communication system within the range of the demodulator capture range. The time during which the phase detection means of the wave interference removal circuit becomes unable to make a determination can be almost ignored.

That is, stable operation of the cross-polarization interference cancellation circuit is guaranteed.

In addition, by adding a means for applying a frequency offset only when the modulated signal shown in the second invention is input, the transmitter for both polarizations can be of the same standard, making manufacturing management and maintenance management very easy. It has an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the first aspect of the present invention. FIG. 2 is a block diagram showing an embodiment of the second invention. 10, 20... Input terminal, 19.29... Output terminal, 11.21... Local oscillator, 12.22... Frequency converter, 13.23... Amplifier, 14... Modulation signal detector.

Claims (2)

[Claims] (1) A transmitting device including means for transmitting a radio signal in which different information is modulated on intersecting polarized waves, a plurality of demodulating means for receiving this radio wave signal and demodulating each polarized wave, and an output of this demodulating means In the polarization multiplexing radio communication system, the transmission device is configured such that the carrier frequencies of the crossed polarizations are slightly different from each other. Features a polarization multiplexing wireless communication system. (2) A transmitting device including a means for transmitting a radio signal in which different information is modulated on intersecting polarized waves, a plurality of demodulating means for receiving this radio wave signal and demodulating each polarized wave, and an output of this demodulating means In a polarization multiplexing wireless communication system, the transmission device includes a local oscillator whose output frequency slightly changes according to a control signal, and a modulation signal. A polarization multiplexing wireless communication system comprising: a detection circuit that detects an input and sends the detected output as the control signal to the local oscillator.