JPH0548567A - Digital multiplex radio system - Google Patents

Abstract

PURPOSE:To reduce the deterioration of the interference compensation characteristics in digital multiplex radio even when there is a delay time difference between cross polarizations by carrying out retiming of identification signals for the first and second main signals using clocks of their self polarizations. CONSTITUTION:Receiving signals of V polarization and H polarization input in receiving sections 21 and 23 are treated for IF conversion, and demodulating sections 22 and 24 take out the first and second base band signals and their corresponding clocks Ck1 and Ck2. Next, A/D converters 31a and 31b identify the base band signals using self polarization clocks Ck1 and Ck2, and send the results to their corresponding transversal equalizers 41a and 41b and to retiming sections 51a and 51b. The equalizers 41a and 41b treat the identification signals for wave equalization to take out the first and second equalization main signals. Sections 51a and 51b recorrect retiming, respectively, and send the results to cross polarization compensators 52a and 52b, respectively. With this, even when there is a time delay difference of V/H polarizations, the identification signals can always be used at the eye opening reduce the detrioration of the compensation characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital multiplex radio system using cross polarization. In recent years, in the digital multiplex radio system, multi-level modulation technology has been adopted in order to improve the frequency utilization efficiency and increase the capacity of the line, and at present, the 256QAM system is being put to practical use. Further, in order to further increase the transmission efficiency, cross polarization is used to obtain twice the frequency efficiency at the same frequency.

In the case of utilizing cross polarization, since the respective polarizations are separated by the antenna, the cross polarization identification (XPD) characteristic of the antenna becomes important, and this characteristic has been improved. When fading occurs on the line, XPD is relatively deteriorated because the level of the desired wave decreases.

Therefore, it is actually practiced to provide a cross-polarization interference compensator in order to compensate for the deterioration of XPD. However, in the case of a cross-polarization interference compensator having a T-space configuration (described later), cross-polarization It is necessary to prevent deterioration of the interference compensation characteristics even if there is a delay time difference.

[0004]

2. Description of the Related Art FIG. 4 is a configuration diagram of a conventional example, FIG. 5 is an explanatory diagram of cross polarization interference, (A) is a frequency arrangement diagram, and (B) is a cross polarization interference diagram. Further, FIG. 6 is an explanatory diagram of interference compensation characteristics. In the figure, the case of the conventional example is shown, and is the case of the present invention as described later (is explained in the section of the embodiment).

Hereinafter, referring to FIGS. 5 and 6, FIG.
The operation of will be described. First, on the transmission side in FIG. 4, the first main signal and the second main signal are input to the modulators (MOD ₁ , MOD ₂ ) 11 and 13. Each modulator has a common carrier generator 15
Since the carriers from are applied, the carriers are modulated by the first and second main signals and then input to the corresponding transmission units (TX ₁ , TX ₂ ) 12, 14.

Each transmitter has a common local oscillator.
Since the local signal from 16 is added, it is converted into first and second transmission signals having the same transmission frequency (for example, f ₁ ) and a predetermined transmission power. Then, the first transmission signal is, for example, vertically polarized wave (hereinafter, abbreviated as V polarization), and the second transmission signal is horizontally polarized (hereinafter, abbreviated as H polarization) from the antenna ( (See FIG. 5A).

On the receiving side, the antenna separates the first received signal of V polarization from the second received signal of H polarization, the former being the receiving section (RX ₁ ) 21 and the latter being the receiving section (RX ₁ ). Input to RX ₂ ) 23 respectively. Therefore, the reception units 21 and 22 convert the reception signals into reception signals in the intermediate frequency band of a predetermined level and add them to the corresponding demodulation units (DEM ₁ , DEM ₂ ) 22, 24.

The demodulators 22 and 24 demodulate the applied received signals to extract clocks CK ₁ and CK ₂ corresponding to the first and second baseband (BB) signals, respectively, and convert them to analog / analog
Digital converter (hereinafter abbreviated as A / D converter) 31a,
Add to 31b.

Here, Ich and Qc from each demodulator
Although the baseband signal of h 1 can be obtained, these baseband signals are collectively referred to as the first and second baseband signals.

Now, the A / D converters 31a and 31b identify the applied baseband signals, extract the identification signals of V polarization and H polarization, and output the corresponding transversal equalizer (T-QEL) 41.
The waveforms are equalized by a and 41b and the first and second equalized main signals are extracted and applied to adders 62a and 62b.

Here, in the first reception signal of the V polarization and the second reception signal of the H polarization, the H polarization component, V, which leaks as shown by the hatched portion in FIG. 5B. Since it contains the polarization component, it must be compensated.

Therefore, on the side of the first received signal, in the A / D converter 32a, the baseband signal of the H polarization output from the demodulation section 24 is output from the clock CK extracted from the demodulation section 22.
The identification signal of H polarization obtained by identification using ₁ is added to the cross polarization interference canceller (XPic) 61a.

Therefore, the cross-polarization interference compensator generates an interference compensation signal and adds it to the adder 62a. Since the output of the transversal equalizer (T-QEL) 41a is also applied here, The leaked H polarization component is compensated and the first reproduced main signal is obtained.

Similarly, for the V-polarized component leaked into the second received signal, the A / D converter 32b identifies the identified V-polarized baseband signal using the clock CK _2. The V polarization identification signal obtained by
In addition to (XPic) 61b, an interference compensation signal is generated here and added to the adder 62b to obtain a second reproduction main signal.

[0015]

[Problems to be Solved by the Invention] Here, the A / D converter 3
2a, eye phase identified in 32b, the state of the propagation path (fading) and device power on / off (however, if there is a speed conversion circuit therein) so changed by using the CK _2, CK ₁ When identification is performed by the A / D converters 32a and 32b, there is a high possibility that identification points will be extracted by identifying points that are not the eye opening points.

Then, a cross polarization interference canceller (XPic) 61a,
61b uses this identification data to generate an interference compensation signal, but if it is not eye aperture data, it is difficult to create a waveform that is equal to the interference wave of the other polarization that leaks into the main signal.

Therefore, the compensating ability of the cross polarization interference compensator (XPic) using the transversal filter having the T space configuration is deteriorated by the delay time difference between the V polarization and the H polarization as shown in FIG. To do.

The T space means that when the frequency of the data clock is f, the frequency of the clock of the modulator / demodulator is also f, and the delay line provided in the transversal equalizer is selected at T = 1 / f. This is the case of the configuration.

That is, in the case of the cross-polarization interference compensator having the T-space configuration, there is a problem that the interference compensation characteristics may be deteriorated if there is a delay time difference between the cross-polarizations. It should be noted that in order to prevent this degradation, a fractional configuration will reduce the degradation, but it is necessary to increase the clock frequency, which complicates the configuration.

Here, when the frequency of the data clock is f, for example, the frequency of the clock of the modulator / demodulator is 2f and the delay line in the transversal equalizer is (T / 2) = 1 / 2f. This is the case of the configuration to be selected.

It is an object of the present invention to reduce the deterioration of interference compensation characteristics in the case of a cross-polarization interference compensator having a T-space configuration, even if there is a delay time difference between cross-polarizations.

[0022]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, reference numeral 1 denotes the first and second main signals, which are modulated by a common carrier to generate the first and second modulated signals, and which have the same transmission frequency and whose polarization planes are orthogonal to each other. 2 is a transmission unit that converts the signal into two transmission signals and transmits the signal.

Reference numeral 2 denotes, on the receiving side, frequency-converts and amplifies the first and second received signals separated by the receiving antenna, and then detects and reproduces the first and second baseband signals and the first and second reproduced signals. It is a receiving / demodulating unit that extracts a clock.

3a and 3b use the first and second reproduced clocks to identify the first and second baseband signals and extract the first and second identification signals. In the identification part,
Reference numerals 4a and 4b denote first and second transversal equalization units for equalizing the first and second identification signals and extracting the first and second equalization main signals.

Reference numerals 5a and 5b synchronize the second and first identification signals with the first and second reproduction clocks, and then use the synchronized second and first identification signals to provide the second and the second identification signals. A first interference compensation signal is generated and added to the first and second equalized main signals to compensate for second and first main signal components included in the first and second equalized main signals. The first and second cross polarization interference canceling means for extracting the first and second reproduced main signals.

[0026]

According to the present invention, if the identification signal identified by the eye opening can always be input to the first and second cross polarization interference canceling means, the other polarization component leaking into the main signal can be obtained. It is possible to create a waveform that is equal to the waveform of (the same principle as the transversal equalizer).

On the other hand, the first and second discriminating portions are the first and second
The reproduced clock of is used to identify the first and second baseband signals to extract the first and second identification signals. These identification signals are identified at the eye opening, This is sent to the first and second cross polarization interference canceling means.

At this time, the problem is that the clock phases of the own polarization and the other polarization are not always constant as described above, so that the outputs of the first and second transversal equalizers When the outputs of the second and first cross polarization interference canceling means are added, there is a high possibility that a timing problem occurs and the addition operation becomes impossible.

Therefore, in order to prevent this, the timing problem is solved by retiming the second and first identification signals with CK ₁ and CK ₂ which are self-polarization clocks. As a result, even if there is a delay time difference between the cross polarizations, the interference compensation characteristic does not deteriorate.

[0030]

FIG. 2 is a block diagram of an embodiment of the present invention (reception side),
FIG. 3 is a block diagram (reception side) of another embodiment of the present invention.

Here, the retiming portions 51a and 51b, the cross polarization interference cancelers 52a and 52b, and the adders 53a and 53b are components of the first and second cross polarization interference compensation means 5a and 5b.
In addition, the same reference numerals indicate the same symmetrical objects throughout the drawings.

The operation of FIGS. 2 and 3 will be described below assuming that the orthogonal polarized waves are V polarized waves and H polarized waves. However, the parts described in the conventional example will be briefly described to explain the parts of the present invention. Will be described in detail.

First, in FIG. 2, a reception signal of V polarization and a reception signal of H polarization are separated by an antenna (not shown). The former is a receiving unit (RX ₁ ) 21 and the latter is a receiving unit. (RX ₂ ) Enter in 23.

The receiving units 21 and 22 convert the received signal into a received signal in the intermediate frequency band of a predetermined level and convert it to the corresponding demodulation unit (DEM ₁ ,
DEM ₂ ) 22, 24. The demodulators 22 and 24 demodulate the applied reception signal to extract the _first and _second baseband signals and the corresponding clocks CK ₁ and CK _{2 and} to convert the analog / digital converter (hereinafter referred to as A / D conversion). Abbreviated as vessel) 31a, 31b.

The A / D converters 31a and 31b are connected to the applied base bar.
Clock signal CK₁, CK ₂Identify using
The identification signals of V polarization and H polarization are extracted and the corresponding trans
Subversal equalizer (T-QEL) 41a, 41b and retiming part
It is sent to 51b and 51a. This identification signal is always
In addition, it is identified by the opening point of the eye.

The transversal equalizers 41a and 41b waveform-equalize the applied identification signal to extract the first and second equalized main signals and apply them to the adders 53a and 53b. Further, the retiming portion 51b re-times the first identification signal with CK ₂ and the retiming portion 51a with the second identification signal with CK ₁ , and then the corresponding cross polarization interference compensators 52b and 52a.
To send to.

As a result, even if there is a delay time difference between the V polarization and the H polarization, the identification signal identified by the eye opening can always be sent to the cross polarization interference canceller. Now,
The cross polarization interference canceller 52a generates an interference compensation signal by using the applied second identification signal, but as described above, the waveform of the H polarization component leaking into the main signal of the V polarization. Can produce a waveform equal to. Therefore, as shown in FIG. 6, it is possible to create a compensation signal having a higher compensation capacity than the conventional example.

Then, the cross polarization interference canceller 52a adds the generated interference compensation signal to the adder 53a.
Since the output of the transversal equalizer (T-QEL) 41a is also applied, the leaked H polarization component is compensated and the first reproduced main signal is obtained.

Similarly, the cross-bias interference compensator 52b similarly generates an interference compensation signal and sends it to the adder 53b.
A second reproduced main signal is obtained. Next, FIG. 3 shows that the identification signals output from the A / D converters 31a and 31b are waveform-equalized by the corresponding transversal equalizers 41a and 41b, and CK ₂₁ and After retiming with CK ₁₁ , the signals are applied to the cross polarization interference cancellers 55b and 55a, which makes it possible to use a more accurate identification signal than in the case of FIG.

At this time, in order to add the output of the transversal equalizer and the output of the cross polarization interference canceller by the adders 56a and 56b, the former output is delayed by the delay portions 57a and 57b, and the addition timing is added. Are matched. The delay amount corresponds to the processing time of the cross polarization interference canceller.

[0041]

As described in detail above, according to the present invention, it is possible to reduce the deterioration of the interference compensation characteristics even if there is a delay time difference between cross polarized waves.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a configuration diagram (reception side) of an embodiment of the present invention.

FIG. 3 is a configuration diagram (reception side) of another embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional example.

FIG. 5 is an explanatory diagram of cross polarization interference.

FIG. 6 is an explanatory diagram of interference compensation characteristics.

[Explanation of symbols]

 1 Transmitter 2 Receiver / Demodulator 3a First Discriminating Unit 3b Second Discriminating Unit 4a First Transversal Equalizing Unit 4b Second Transversal Equalizing Unit 5a First Cross Polarization Interference Compensation Means 5b 2 Cross polarization interference compensation means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenzo Kobayashi 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (1)

[Claims] 1. A transmitting side, after modulating a common carrier with first and second main signals synchronized with each other to generate first and second modulated signals, at the same transmitting frequency, a plane of polarization is Transmitting section for converting into first and second transmission signals orthogonal to each other and transmitting
(1) is provided, and on the receiving side, the first and second received signals separated by the receiving antenna are frequency-converted and amplified, and then detected to detect the first and second baseband signals and the first and second baseband signals. A receiving / demodulating section (2) for extracting a reproduction clock and, using the first and second reproduction clocks, identifying the first and second baseband signals and extracting the first and second identification signals. The first and second identification units (3a,
3b) and a first and a second transversal equalization unit (4a, 4b) for equalizing the first and second identification signals and extracting a first and a second equalization main signal. In the method, after synchronizing the second and first identification signals with the first and second reproduction clocks, the synchronized second and first identification signals are used to perform second and first interference. A compensation signal is generated and added to the first and second equalized main signals, and the second and first main signal components included in the first and second equalized main signals are compensated to obtain the first and second equalized main signals. A digital multiplex radio system characterized by comprising first and second cross polarization interference canceling means (5a, 5b) for extracting first and second reproduced main signals.