JPH05129972A - Adaptive receiver - Google Patents

Abstract

PURPOSE:To quicken a focusing speed of power in an adaptive matching filter of transversal filter configuration having plural taps. CONSTITUTION:Reception signals at each tap are weighted by an adaptive matching filter 111 and resulting outputs are subject to addition processing. Analog switches 181-18N stop addition processing of tap outputs other than that of a reference tap when a clock of a reception signal is asynchronous with a clock in its own equipment. Thus, a focusing speed of power by the adaptive matching filter 111 is quickened at application of power or synchronization locking from out of clock synchronism.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adaptive receiver, and more particularly to an adaptive receiver that automatically estimates the characteristics of a fading transmission line in non-line-of-sight wireless communication and adaptively configures the optimum receiver characteristics.

[0002]

2. Description of the Related Art Non-line-of-sight communication is a communication that utilizes tropospheric scattering of radio waves and mountain diffraction, and does not directly receive radio waves but indirectly receives radio waves, which causes fading. There is. Therefore, in digital signal transmission of non-line-of-sight communication, adaptive receivers using adaptive filters and adaptive equalization techniques have been studied to overcome fading.

FIG. 2 shows a configuration example of a conventional adaptive receiver. This configuration is an example of N-fold diversity, and has a number of adaptive matched filters proportional to the diversity multiplicity.

That is, the present receiver has adaptive matched filters 111 to 11N having a transversal filter configuration having a complex multiplier corresponding to each tap, and N output units of these adaptive matched filters are linearly combined. Adder 140
And an adder 1 and an automatic gain control amplifier 2 for performing automatic gain control of the linearly combined signal.

Further, the present receiver receives the transmission data estimation value and adjusts the tap gain of each adaptive matched filter so as to form a matched filter for each diversity transmission line, and the complex multiplier 131 in each adaptive matched filter. In addition to having correlators 161 to 16N corresponding to ~ 13N, delay devices 151 to 15N
... and a correlator 121 to 12N having a distributor 170, a complex multiplier at each tap, and a linear equalizer for removing intersymbol interference in a transversal configuration, and a forward equalizer as a decision feedback equalizer. And a rear equalizer 4.

Furthermore, the present receiver receives the transmission data estimation value and the output signals of the front equalizer 3 and the rear equalizer 4 and uses the error signal which is the difference between the input of the decision unit 7 and the output signal. , A group of correlators corresponding to each complex multiplier in the front equalizer 3 and the rear equalizer 4 in order to adjust the tap gains of the front equalizer 3 and the rear equalizer 4 so that intersymbol interference is minimized. 9 and 10, and a subtractor 5, a demodulator 6 and a determiner 7 for obtaining a reception output signal which is a transmission data estimation value.

In such a configuration, the power of the received signal of each path is dispersed on the time axis due to the effect of fading in the propagation path, but each delay unit 121 in each adaptive matched filter 121
The power before and after ~ 12K… is focused symmetrically around the reference tap. This reference tap position is the same tap for each diversity path, and by combining these in the adder 1, the maximum ratio combining of diversity is performed and the SN ratio of the signal becomes maximum. Upon reception of this signal, the inter-code interference is removed by the front equalizer 3 and the rear equalizer 4. The signal (IF) from which the interference component has been removed is demodulated by the demodulator 6 into a baseband signal, which is binarized by the determiner 7 and output as transmission estimation data.

In the modulator 13, the output of the oscillator 11 is modulated by the output of the determiner 7 and the distributor 170 in each correlation circuit is modulated.
The correlation ratio is obtained by each correlator based on this distributed output.

Further, the subtractor 8 calculates an error between the output of the demodulator 6 and the output of the decision unit, and the oscillator 11 uses the error output.
The output of is modulated and input to the correlator groups 9 and 10, and the correlation ratio is obtained. Then, the output of the correlator group 9 causes the front equalizer 3 to delay the advance component of the power dispersed in the time axis, and the output of the correlator group 10 causes the rear equalizer 4 to output.
Controls to advance the delay component of the power.

In the conventional adaptive receiver described above, the correlator output of each tap of each correlation circuit is directly applied to the multiplier of the corresponding tap in the adaptive matched filter.

Since the adaptive matched filter has a plurality of taps, an arbitrary tap becomes a tap having the highest signal level, that is, a reference tap, when the power is turned on or when the synchronization is pulled from the clock out of sync state. there is a possibility.

At this time, for example, when the tap at the end of the adaptive matched filter becomes the reference tap, the one that focuses the power dispersed on the time axis with the reference tap as the center is originally on the one side of the reference tap. Since there are no taps, there is a drawback that the signal cannot be fully focused and a signal containing many distortion components is output.

The adaptive matched filter operates similarly to the automatic equalizer, and controls the tap coefficient of each tap so that the SN ratio of the output signal is maximized. Therefore, when obtaining the optimum tap coefficient, the larger the number of taps,
There is also a drawback that the convergence speed becomes slower and the data disconnection time becomes longer accordingly.

As a recent tendency, the number of taps tends to increase as a countermeasure against fading, which becomes more and more severe due to the reduction of antenna diameter and the lengthening of transmission lines. It is particularly important to improve the convergence speed by this tap switching control. is there. Therefore, effective improvement measures have been desired.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and its object is to eliminate the distortion component at the time of turning on the power supply or pulling the synchronization from the state out of clock synchronization while converging the power in the filter. An object of the present invention is to provide an adaptive receiver that can increase the speed.

[0016]

An adaptive receiver according to the present invention has a plurality of taps, a transversal filter for weighting each received signal for each tap, and then adding their outputs, and a clock for the received signal. A means for suppressing addition processing of tap outputs other than the reference tap among the plurality of taps when the clock in the aircraft is in an asynchronous state, and demodulation processing is performed using the output of the transversal filter. Is characterized by.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the adaptive receiver according to the present invention, and the same parts as those in FIG. 2 are designated by the same reference numerals.

In the figure, in addition to the conventional configuration, the receiver of the present embodiment inhibits the tap weighting operation of each complex multiplier in each adaptive matched filter, and weights only the reference tap (center tap). Analog switch 18 for
1 to 18N (18k does not exist) and a controller 14 for controlling these analog switches are provided.

An alarm signal out of clock synchronization is input from the demodulator 6 to the controller 14. That is, the demodulator 6 compares the phase of the clock of the received signal with the clock of its own device, and when it is determined that they are asynchronous, an alarm signal is output and input to the controller 14. It is. As a result, all the analog switches are turned off when the power is turned on or when the synchronization is pulled from the clock synchronization lost state.

A CMOS type analog switch may be used for each analog switch.

In this configuration, the received signals input from the input terminals 101, 102, ..., 10N of the present adaptive receiver are focused by the adaptive matched filters 111, 112, ..., 11N centering on the reference tap for each diversity path. To do. The signals of these paths are combined by the adder 1, the inter-symbol interference is removed by the front equalizer 3 and the rear equalizer 4, then demodulated by the demodulator 6, and the transmission data is estimated by the decision unit 7. The value is output.

In the demodulator 6, the clock is reproduced from the input signal. At this time, the main response of the signal components dispersed on the time axis exists in the reference tap of the adaptive matched filter, for example, the complex multiplier 13K. And if the position of this reference tap is near the center of the taps forming the adaptive matched filter, there are enough taps on both sides of the reference tap,
The dispersed signal components can be sufficiently focused. Therefore, when synchronizing the clocks, if the adaptive matched filter is only the reference taps, the clocks are synchronized and normally operated, and then other taps are also connected, the main response becomes the reference taps.

Therefore, in the adaptive receiver of this example, the demodulator 6
In response to the clock out of sync alarm signal from, the controller 14 controls on / off of the analog switch provided on the correlator output side of the correlation circuit of each diversity path. That is, when the clocks are asynchronous, the adaptive matched filter has only the reference taps, and the other taps do not use the analog switch in the off state. This allows
Convergence speed is accelerated.

It should be noted that all analog switches may be turned on when clocks are synchronized, and all taps in the adaptive matched filter may be operated.

In the present embodiment, the configuration in the case of N-fold diversity has been described. However, N = 1, that is, an adaptive receiver provided with one adaptive matched filter and one correlation circuit is also provided with a similar configuration. It is clear that the convergence speed of will be faster.

As described above, the tap coefficient given to the complex multiplier of each tap of the adaptive matched filter is controlled to be turned on / off by an analog switch, and only the reference tap is used and all taps are used. By switching between and, the convergence speed of the adaptive matched filter is accelerated, and the power distributed in the time axis direction is focused around the reference tap that is near the center of the adaptive matched filter, so that taps can be fully utilized and distortion is eliminated. Does not occur.

[0028]

As described above, according to the present invention, it is possible to accelerate the convergence speed of the adaptive matched filter by suppressing the addition processing of tap outputs other than the reference tap when the clocks are in the asynchronous state. There is.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an adaptive receiver according to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional adaptive receiver.

[Explanation of symbols]

 14 Controller 111 to 11N Adaptive matched filter 121 to 12N Correlation circuit 181 to 18N Analog switch

Claims (1)

[Claims] 1. A transversal filter that has a plurality of taps, weights each received signal for each tap, and then performs addition processing of their outputs, and a clock of the received signal and a clock in its own device are in an asynchronous state. And a means for suppressing addition processing of tap outputs other than the reference tap among the plurality of taps, and demodulation processing is performed using the output of the transversal filter. ..