JP2504184B2 - Cross polarization communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used for orthogonal polarization digital wireless communication using two polarized waves orthogonal to each other. In particular, it relates to elimination of cross polarization interference.

〔Overview〕

The present invention, in an orthogonal polarization communication system that transmits two series of signals by using two polarized waves that are orthogonal to each other, when the input of the modulation circuit on the transmission side is disconnected, the output of the modulation circuit is By cutting off, the cross polarization interference canceling circuit of the receiving side device is reset,
This is to enable normal demodulation of the polarization signal on the normal side.

[Conventional technology]

In recent years, in the field of microwave radio communication, two polarizations orthogonal to each other (vertical and horizontal, and left-hand circular polarization and right-hand circular polarization)
Orthogonal polarization digital wireless communication systems that transmit different information to each other and use frequencies effectively have attracted attention. When such orthogonal polarization is used, cross polarization interference occurs due to anisotropy of the medium caused by rainfall or the like. In order to remove this cross polarization interference, various cross polarization interference removal methods have been proposed.

In such a conventional technique, when the demodulator loses carrier synchronization due to fading or the like and an abnormality occurs in the demodulation output, the cross polarization interference canceling circuit does not operate normally. Further, at the time of recovery, it causes troubles such as delaying the convergence of the control operation. Therefore, a method of resetting the cross polarization interference canceling circuit by a carrier synchronization desynchronization signal has been conventionally used.

FIG. 3 shows an example of a conventional orthogonal polarization digital wireless communication system.

The signals input to the input terminals 1 and 2 for the horizontal and vertical polarizations (H and V polarizations) are transmitted to the air by the antennas 9 and 10 via the modulation circuits 3 and 4 and the transmission circuits 7 and 8. To be done. The antennas 11 and 12 and the receiving circuits 13 and 14 are supplied with signals that have been subjected to cross polarization interference. The subtraction circuit 17 (18) calculates the difference between the output signal of the reception circuit 13 (14) and the signal output from the reception circuit 14 (13) through the cross polarization interference cancellation circuit 16 (15). Taken, H side (V side)
Is input to the demodulation circuit 19 (20).

FIG. 4 is a block diagram showing an example of the cross polarization interference canceling circuit. In this figure, an example of a transversal filter having 3 taps is shown, but a transversal filter other than 3 taps may be used. Receiver circuit 14 (1
The output signal of 3) is branched and input to the input terminal 62, passes through each of the weighting circuits 69 to 74, the combining circuits (Σ) 65, 66, and the 90 ° coupler 67 through the delay circuits 63 and 64, Terminal
It is output from 75 and input to the subtraction circuit 17 (18) in FIG.

The weighting circuits 69 to 74 of the respective taps correlate from the error signal which is the error component of the reception signal output from the demodulation circuit 19 (20) in FIG. 3 and the data signal which is the V (H) polarized wave signal. The correlation detection signal RS2 (R obtained by the detection circuit 22 (21)
By S1), the error signal is controlled to be the minimum.

Further, the demodulation circuits 19 and 20 output the carrier wave out-of-sync signals NS1 and NS2 when they are in the asynchronous state. With this signal, the control circuit 68 resets the tap control voltages in the cross polarization interference canceling circuits 15 and 16 so that the output levels of the weighting circuits 69 to 74 are minimized. This carrier out-of-sync signal NS
4, NS5 is supplied to the cross polarization interference canceling circuits 15 and 16 via the OR circuit 23, so when either demodulation circuit 19 or 20 outputs the carrier synchronization desynchronization signal NS1 or NS2,
The cross polarization interference canceling circuits 15 and 16 are reset.

[Problems to be solved by the invention]

However, in the above-mentioned conventional technique, when the input of the demodulation circuit is disconnected on the polarization side of either one of the two,
The output of the modulation circuit on the polarization side is in a non-modulated state, and only the carrier wave is input to the demodulation circuit.

Here, a case will be described in which the V polarization and the H polarization are used as the orthogonal polarizations and a signal disconnection occurs on the V polarization side. At this time, since the demodulation circuit on the V polarization side synchronizes with the carrier wave, it does not output the carrier wave out-of-sync signal. Therefore, the two cross polarization interference canceling circuits operate without being reset. At this time, the cross polarization interference canceling circuit for the H polarization continues the compensating operation by the erroneous control signal. Then, when the demodulation circuit on the H polarization side is out of carrier synchronization, the two cross polarization interference canceling circuits are reset.
When the cross polarization interference canceling circuit on the H polarization side is reset, the demodulation circuit for the H polarization is brought into carrier synchronization and the reset is released. As a result, the cross polarization interference canceling circuit for the H polarization continues the compensating operation with the wrong control signal.

As described above, when one polarization signal is disconnected (non-modulated), the demodulation circuit on the polarization side cannot reproduce normal demodulated data even if the other polarization signal is normal. It was

It is an object of the present invention to solve the above problems and to provide an orthogonal polarization communication system that can normally demodulate the other polarization signal even when one polarization signal is disconnected.

[Means for solving problems]

The orthogonal polarization communication system of the present invention includes a transmission side device and a reception side device that transmit and receive two series of signals using mutually orthogonal polarized waves, and the transmission side device performs two series modulation and transmission of signals. A receiving side device is provided with a two-series receiving circuit and a demodulating circuit for receiving and demodulating a signal, and a receiving side device is further provided with an output of the receiving circuit based on the output of the demodulating circuit. In the orthogonal polarization communication system, which includes interference compensating means for compensating the cross polarization interference included therein and means for resetting the interference compensating means when the demodulation circuit becomes out of synchronization with the carrier wave, the modulation circuit is provided to the transmitting side device. And a means for cutting off the output of the modulation circuit in which the input signal stage is detected.

[Action]

When the output of the modulation circuit is cut off, the demodulation circuit on the receiving side corresponding to the modulation circuit is out of carrier synchronization and the cross polarization interference canceling circuit is reset. Unless the supply of the carrier wave to the modulation circuit is restarted, the corresponding demodulation circuit is not brought into the carrier wave synchronization state, and the cross polarization interference canceling circuit remains reset. Therefore, the demodulation circuit on the normal side normally reproduces the demodulated data without inputting a meaningless compensation signal.

〔Example〕

FIG. 1 is a block diagram of an orthogonal polarization digital radio communication device according to an embodiment of the present invention.

This device includes two series of modulation circuits 3 and 4, transmission circuits 7 and 8, and a transmission side antenna 9 that respectively modulate, transmit, receive and demodulate two series of input terminals 1 and 2 using mutually orthogonal polarized waves. , 10, receiving side antennas 11, 12, receiving circuit 1
3, 14 and demodulation circuits 19, 20. Also, demodulation circuit 1
Correlation detection circuits 21 and 22, cross-polarization interference canceling circuits 15 and 16 and subtraction circuits are provided as interference compensating means for compensating for cross-polarization interference included in outputs of receiving circuits 13 and 14 based on outputs of 9 and 20. Equipped with 17, 18. Furthermore, when the demodulation circuits 19 and 20 are out of carrier synchronization, the cross polarization interference canceling circuit
As means for resetting 15, 16, the carrier wave out-of-sync signals NS1, NS2 of the demodulation circuits 19, 20 are passed through the OR circuit 23,
It is supplied to the cross polarization interference canceling circuits 15 and 16.

Here, the feature of the present embodiment is that the modulation circuit 3,
4 is provided with signal loss detection circuits 5 and 6 as means for detecting input signal loss, and the modulation circuits 3 and 4 are provided with means for blocking the modulation output when the input signal loss is detected. is there.

FIG. 2 is a block configuration diagram showing details of the modulation circuit and the signal loss detection circuit.

The signals input to the P channel input terminal 24 and the Q channel input terminal 25 are input to the D / A converters 26 and 27, pass through the reduction filter circuits 28 and 29, and are input to the multipliers 30 and 31. The output of the carrier wave oscillator 32 becomes a carrier wave having a different π / 2 phase in the π / 2 phase shifter 34, and is input to the multipliers 30 and 31. The signals modulated by the multipliers 30 and 31 are combined by the combiner 35, the signal level is adjusted by the automatic gain control amplifier 36, and the signal is output from the output terminal 40 at a constant signal level. The automatic gain control circuit 39 detects the signal level at the output terminal 40,
Gain control voltage N2 that determines the gain of the amplifier 36 with automatic gain control
Occurs. The voltage generator 37 includes an amplifier 36 with automatic gain control.
Minimize the gain of. That is, the voltage N1 is generated so that the signal at the output terminal 40 is cut off. The signal loss detection circuit 33 is
A signal break of the input signals 24 and 25 of the modulation circuit is detected, and a signal break detection reset signal S is generated. Analog switching circuit 38
Selects the output voltage N2 of the automatic gain control circuit 39 or the output voltage N1 of the voltage generator 37 for the voltage N3 that determines the gain of the amplifier 36 with automatic gain control by the signal disconnection detection reset signal S. That is, the amplifier with automatic gain control is normally used.
Automatic gain control is applied to 36, and a normal output signal is obtained at the output terminal 40. When the input signal of the modulation circuit is cut off, the gain of the automatic gain control amplifier 36 is most narrowed down, and the output terminal 40 is in the output signal cutoff state. When the output terminal 40 is in the state where the output signal is disconnected, the receiving circuit 13 (when the H polarized wave is disconnected) or 14 (when the V polarized wave is disconnected) in FIG.
Output signal is disconnected, and the carrier wave is out of synchronization in the demodulation circuit 19 or 20, and the carrier out-of-sync signal NS1 (in the case of H polarization) or NS2 (in the case of V polarization) is transmitted to eliminate cross-polarization interference. Circuits 15 and 16 are reset. Therefore, the cross polarization interference canceling circuit for normal V polarization (or H polarization) repeatedly resets and releases reset,
It is possible to prevent a malfunction of the conventional cross polarization interference canceling circuit in which normal data cannot be reproduced by the demodulation circuit.

In this embodiment, positive logic (“H”: alarm,
Although the case of “L”: normal) has been described, the present invention can be similarly implemented in the case of negative logic. The signal disconnection detection circuit 33 can be easily realized by arranging flip-flops corresponding to the number of input signal rows in a column. If the amplifier 36 with automatic gain control has a minimum gain of about 0 V, that is, if the output signal is cut off, the voltage generator
37 should be grounded.

〔The invention's effect〕

As described in detail above, the present invention disconnects the output of the modulation circuit by using the circuit that detects the disconnection of the input signal of the modulation circuit. This prevents the demodulation circuit from outputting the carrier synchronization desynchronization signal due to the unmodulated carrier wave, and even if the modulation circuit input signal is cut off, the demodulation circuit sends the carrier desynchronization signal as usual to cause cross polarization interference. The removal circuit can be reset, and the malfunction can be prevented.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an orthogonal polarization digital wireless communication device according to an embodiment of the present invention. FIG. 2 is a block configuration diagram showing details of the modulation circuit and the signal loss detection circuit. FIG. 3 is a block diagram of a conventional orthogonal polarization digital wireless communication device. FIG. 4 is a block diagram showing an example of a cross polarization interference canceling circuit. 1, 2, 62 ... Input terminals, 3, 4 ... Modulation circuit, 5,
6, 33 ... Signal loss detection circuit, 7, 8 ... Transmission circuit, 9,
10, 11, 12 ... Antenna, 13, 14 ... Receiving circuit, 15, 16
...... Cross-polarization interference canceller, 17, 18 …… Subtractor, 1
9, 20 …… Demodulation circuit, 21, 22 …… Correlation detection circuit, 23 ……
OR circuit, 24 …… P channel input terminal, 25 …… Q channel input terminal, 26,27 …… D / A converter, 28,29 …… Reduction filter, 30,31 …… Multiplier, 32 ...... Carrier oscillator, 34 ...
… Π / 2 phase shifter, 35 …… combiner, 36 …… amplifier with automatic gain control, 37 …… voltage generator, 38 …… analog switching circuit, 39
...... Automatic gain control circuit, 40 …… Output terminal, 63,64 …… Delay circuit, 65,66 …… Synthesis circuit, 67 …… 90 ° coupler, 68
...... Control circuit.

Claims (1)

(57) [Claims] 1. A transmission side device and a reception side device for transmitting and receiving two series of signals by using polarized waves orthogonal to each other, wherein the transmission side device performs two series modulation and transmission of the two series signals. A receiver circuit and a demodulator circuit for receiving and demodulating the two-series signals, and the receiver device further includes an output of the demodulator circuit. An orthogonal polarization communication system including interference compensation means for compensating for cross polarization interference included in the output of the receiving circuit based on the above, and means for resetting the interference compensation means when the demodulation circuit is out of carrier synchronization. In the transmitting device, an input signal loss detection means for detecting an input signal loss of the modulation circuit, and an output of the series side modulation circuit in which the signal loss is detected by the input signal loss detection means are cut off. Orthogonal polarization communication system, characterized in that a that means.