JP2591263B2 - Adaptive receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive reception apparatus having an adaptive matched filter for automatically estimating the characteristics of a fading transmission path and adaptively configuring optimal receiver characteristics. More particularly, the present invention relates to an adaptive receiver having an improved correlation value processing circuit for controlling an adaptive matched filter.

[Conventional technology]

Non-line-of-sight communication performs communication using radio wave tropospheric scattering, mountain diffraction, and the like. Fading is likely to occur because an indirect wave is received instead of a direct wave. In recent years, in digital signal transmission among non-line-of-sight communications, an adaptive receiver using an adaptive matched filter or an adaptive equalization technique has been proposed to overcome fading. The adaptive receiver described in this specification for the fading transmission path includes a transversal filter operating as an adaptive matched filter for a diversity transmission path through which a digital signal is transmitted, the number of which corresponds to the number proportional to the diversity multiplicity. It is provided, for example, as shown in the block diagram of FIG.

In FIG. 3, an adaptive receiver applied in an n (n is a positive integer) multiple diversity reception system is a transversal filter in which a first diversity transmission path signal (reception data) is input via an input terminal 1a. Adaptive matched filter 3a and another diversity transmission path signal are input terminal 1b.
1 to 1n. As exemplified by the reference numeral 3a, a plurality of delay units 34, 35,... For delaying a diversity transmission path signal (received data as a high-frequency signal) in multiple stages for a predetermined time τ.
, The complex multipliers 31, 32,... Having each delay output (tap output) as one input, and the adder 33 summing the outputs of the complex multipliers 31, 32, and using the sum as the output of the filter. It is basically composed of

Correlation circuits 40a to 40n provided corresponding to the respective adaptive matched filters 3a to 3n, as exemplified by the reference numeral 40a, transmit the input signal (high-frequency signal) of the corresponding adaptive matched filter to a predetermined time? , A plurality of delay units 44, 45,..., Each having a delayed output (tap output) as one input, and a correlator 41, 42,. Output (estimated transmission data) to modulator 16
And received via the multiplier 22 and received by the correlators 41, 4
, And a distributor 43 for distributing and outputting to the other input of each of the correlators 41, 42,..., And outputs (complex baseband signals) of the correlator 41, 42,. It is the other input.

That is, the correlation circuits 40a to 40n calculate the correlation value between the reception data and the transmission data estimation value of the corresponding adaptive matched filter, adjust the tap gain (weight) of the transversal filter as the adaptive matched filter based on the correlation value, and The transversal filter is operated as an adaptive matched filter.

The outputs of the adaptive matched filters 3a to 3n are linearly combined by the adder 5 and input to the automatic gain control amplifier 6, where they are subjected to gain control, and are respectively applied to the forward equalizer 7 and one input of the correlation circuit 17a. Supplied.

The correlation circuit 17a inputs the output (error signal) of the subtractor 12 to the other input via the modulator 15 and the multiplier 21, and outputs a control signal based on the correlation value of both inputs to the other input of the front equalizer 7. Give to input. The forward equalizer 7 adjusts the tap gain based on the output of the correlation circuit 17a, and removes the intersymbol interference caused by the leading edge of the pulse in the output signal of the automatic gain control amplifier 6. The output signal of the forward equalizer 7 is demodulated by the demodulator 9 and output to the subtracter 10.

The correlation circuit 18a includes the modulator 1 output via the multiplier 21.
A control signal based on the correlation value between the output of the modulator 5 and the output of the modulator 16 is output to the rear equalizer 8. The rear equalizer 8 forms a predetermined feedback signal based on the output of the modulator 16 and the output of the correlation circuit 18, and outputs it to the subtracter 10. The subtractor 10 subtracts the feedback signal output from the backward equalizer 8 from the output signal of the demodulator 9, that is, removes the intersymbol interference caused by the trailing edge of the pulse and outputs the result.

The discriminator 11 discriminates and determines the output of the subtractor 10 based on a predetermined threshold value, and outputs the reproduced pulse signal to the output terminal 2 as a reception output. The modulator 12 obtains the difference between the input and output signals of the determiner 11 and outputs the difference to the modulator 15 as an error signal. The demodulator 9, the modulator 15, and the modulator 16 operate based on a local signal (for example, 70 MHz) from the oscillator 20. It is well known that the forward equalizer 7 performs linear equalization and the rear equalizer 8 performs non-linear equalization and is called a decision feedback equalizer. The forward equalizer 7 and the backward equalizer 8 have the same configuration as the adaptive matched filter 3a, and the correlation circuits 17a and 18a have the same configuration as the correlation circuit 40a.

The control circuit 23 receives the baseband clock signal from the demodulator 9 and turns on and off the multipliers 21 and 22 at the time when the intersymbol interference of the demodulated data is the least in synchronization with the clock signal. I do. The sampled high-frequency outputs from multipliers 21 and 22 are output to correlation circuits 17a and 40a to 40n, respectively.

Thus, a reception output (transmitted data estimated value) which is hardly affected by the selective fading is obtained at the output terminal 2.

[Problems to be solved by the invention]

In the above-described conventional adaptive receiver, one correlation signal input to the correlation circuit corresponding to the adaptive matched filter usually has a minimum inter-symbol interference of demodulated data, that is, an eye pattern of the data. Sought in the most open position. Therefore, the correlation signal, which is a high-frequency signal output from the modulator, is input to the multiplier,
The multiplier is turned on / off in synchronization with a clock signal, and is sampled to obtain the correlation signal. Also, in the correlator, the signal integrated and averaged and detected by the correlator is output to the adaptive matched filter. However, since the output corresponds to the sampling ratio, the output voltage is low. Was. Therefore, a large gain is required for the output circuit of the correlator, and there is a disadvantage that the output circuit is easily affected by power supply ripple, leak, external noise, and the like. Further, since the correlation signal is sampled in a high frequency band, there are disadvantages that the circuit is expensive, large, and difficult to integrate.

[Means for solving the problem]

In the adaptive receiver of the present invention, the same number of diversity multiplicity and the number of complex multipliers provided for each tap receive a complex baseband signal input and adjust the gain of the tap to provide a corresponding diversity transmission path. A transversal filter constituting an adaptive matched filter, and a correlation value between an input signal of the corresponding transversal filter provided for each transversal filter and a transmission data estimation value which is a reception output of the receiver. A correlation circuit having a correlator for generating the complex baseband signal corresponding to the complex multiplier based thereon, wherein the adaptive receiver adaptively configures an optimal receiver for a fading transmission path, Detector for sampling and holding the output of a correlator for each data bit in synchronization with a clock signal Provided, and inputs the output to the corresponding said complex multiplier.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an adaptive receiver according to one embodiment of the present invention. FIG. 1 shows an example applied to the n-fold diversity receiving system as in the conventional example. Therefore, the same components as those in the conventional example are denoted by the same reference numerals and description thereof is omitted.

In this embodiment, the multipliers 21 and 22 in the conventional example are omitted, and therefore, the control circuit 23 for controlling them is also omitted. On the other hand, the correlation circuits 4a to 4n, 17 and 18 respectively have detectors (correlation circuits 4a Are provided with symbols 46 and 47), and the output is input to the complex multiplier (codes 31 and 32 in the adaptive matched filter 3a). The detector (for example, reference numerals 46 and 47) is controlled by a gate signal output from the gate signal generation circuit 19 connected to the demodulator 9 as described later, and when the intersymbol interference of the demodulated data is minimal. The integrated value of the correlation value of is output.

FIG. 2 shows the detector in FIG. 1 (for example, reference numerals 46 and 47).
It is a block diagram of an example.

In FIG. 2, 81 is an analog switch, 82 is a hold circuit, 83 is a buffer amplifier, and 84 is an integration circuit.

The gate signal generation circuit 19 synchronizes with the clock signal output from the demodulator 9 and operates for each bit of data when the intersymbol interference of the demodulated data is minimal, that is, when the eye pattern of the data is most open. Analog switch 81
To gate. Thereby, the complex baseband signal output from the correlator is gated (sampled). The gated signal is held by a hold circuit 82, amplified by a buffer amplifier 83, and integrated by an integration circuit 84. Then, the integrated value of the correlation value when the intersymbol interference of the data is the least is output. In addition, analog switch
81 may use a multiplier.

〔The invention's effect〕

As described above, the present invention samples and holds the correlator output, which is a baseband signal in a correlation circuit, bit by bit in synchronization with a clock signal.
A high signal level correlator output voltage can be obtained.
As a result, there is an effect of reducing interference, noise, or imperfections in design and manufacture by other circuits in the device.

Further, since the correlation value input to each correlation circuit is obtained by baseband signal processing, there is an effect that the size and integration can be reduced at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a block diagram of a detector according to the present invention, and FIG. 3 is a block diagram of a conventional embodiment. 1a to 1n input terminals, 2 output terminals, 3a to 3n adaptive matched filters, 4a to 4n, 40a to 40n, 17, 17a, 18, 18a
... correlation circuit, 5 ... adder, 6 ... automatic gain control amplifier, 7 ... forward equalizer, 8 ... backward equalizer, 9 ... demodulator, 10, 12 ... subtractor, 11 ... … Judgment device, 15, 16… Modulator, 19… Gate signal generation circuit, 20… Oscillator, 21, 22
…… Multiplier, 23 …… Control circuit, 31, 32 …… Complex multiplier, 3
3 ... Adder, 34,35 ... Delayer, 41,42 ... Correlator, 43
…… Distributors, 44,45 …… Delayers, 46 …… Detectors, 81 ……
Analog switch, 82 Hold circuit, 83 Buffer amplifier, 84 Integration circuit.

Claims (2)

(57) [Claims] An adaptive matched filter for a corresponding diversity transmission line by receiving complex baseband signal inputs and adjusting gains of the taps by a plurality of complex multipliers provided for each tap in the same number as the diversity multiplicity. And a correlation value between an input signal of the corresponding transversal filter and a transmission data estimation value which is a reception output of the receiver. A correlation circuit having a correlator for generating a baseband signal corresponding to the complex multiplier, wherein the adaptive receiver adaptively configures an optimal receiver for a fading transmission path. In synchronization with the clock signal, and a detector for sampling and holding data for each bit of data is provided. Adaptive receiver, characterized in that inputting a force to the corresponding said complex multiplier. 2. An analog switch for sampling the correlator output in synchronization with a clock signal;
2. The adaptive receiver according to claim 1, further comprising: a hold circuit that holds the sampled signal; and an integration circuit that integrates the held signal.