JP3141661B2 - Equalization demodulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
It is used in a receiver of a digital wireless communication system using TDMA, and is used for spatial diversity using a plurality of antennas and a decision feedback equalizer (hereinafter, DF).
The present invention relates to an equalizer / demodulator which can improve an error rate improvement characteristic of the equalizer in a combining diversity equalizer having a configuration in which E is abbreviated.

[0002]

2. Description of the Related Art In recent years, digital data communication T
Research and development of digital mobile radio communication systems using DMA have been active. In mobile radio communication, it is necessary to take measures against deterioration of a transmission path which cannot be avoided in communication between mobile objects such as multipath and fading.
As one of the above measures, there is a method of using a combined diversity equalizer combining spatial diversity using a plurality of antennas effective for fading and DFE effective for multipath (for example, Japanese Patent Application Laid-Open No. 3-34262).
No. 7).

[0003] A conventional combining diversity equalizer will be described below. FIG. 4 shows a block configuration of a conventional combining diversity equalizer. In FIG.
Reference numerals 1 and 402 are reception antennas. 403 and 404 are receiving units for amplifying and frequency-converting a received signal.
Is a band limiting filter (hereinafter abbreviated as BPF). A switch 407 switches the outputs of the BPFs 405 and 406 at intervals of half the symbol rate of the digital modulation wave. A quadrature demodulator 408 converts the input signals from the receiving antennas 401 and 402 into a quadrature baseband signal. A sampling unit 409 samples the orthogonal baseband signal and converts the signal into a digital signal. Reference numeral 410 denotes a DFE.

The operation of the combining diversity equalizer constructed as described above will be described below.

[0005] First, modulated signals of two systems in a carrier (hereinafter abbreviated as RF) band received by two antennas 401 and 402 are received by receiving units 402 and 403 at an intermediate frequency (hereinafter abbreviated as IF). The frequency is converted into a band, and the band is limited by the BPFs 405 and 406. Next, the two IF signals are switched by the switch 407 at intervals of half the symbol rate, and 408
Is converted to an orthogonal baseband signal by the orthogonal demodulator. The converted quadrature baseband signal is sampled by a sampling unit 409 and converted into digital data, and is then equalized by a DFE 410 and output as equalized demodulated data.

[0006]

However, in the above-described conventional configuration, the signal is switched and sampled at a time interval of half the symbol rate, so that one system of signals has the maximum aperture point of the eye pattern of the demodulated signal. When the sampling is performed by the above method, the other system signal is sampled at the transition point of the signal shifted in timing by a half symbol length, and thus there is a problem that the maximum diversity effect cannot be obtained. I was

The present invention solves the above-mentioned conventional problems. In a receiver of a digital radio communication system using TDMA, when synthesizing signals obtained from respective reception systems constituting a diversity system, a serial correlation is used. It is an object of the present invention to provide an equalizer / demodulator that can improve the error rate improvement characteristics of the equalizer by combining signals having strong characteristics.

[0008]

In order to achieve the above object, an equalizer / demodulator according to the present invention converts an orthogonal baseband signal obtained by asynchronous quadrature detection of a received modulated wave into a signal having a tap interval of 2 times the tap interval of a feedforward filter section of a DFE. An equalizer that combines a signal sequence having a strong sequence correlation by using a correlation signal of a frame sync unit that performs frame synchronization using a sequence correlation from the sampled orthogonal baseband signal by sampling at an interval of an integral number of the above. Has an arrangement for performing an equalization process as an input signal.

[0009]

With this configuration, the information of the digital modulation signal input from each antenna can be effectively used in the equalizer / demodulator using the combining diversity by the switching method, so that the error rate improvement characteristic of the equalizer can be obtained. Can be improved.

[0010]

【Example】

(Embodiment 1) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, 101 and 102 are receiving antennas, 103 and 104 are receiving sections, and 105 and 106 are IFs.
A band limit filter 107, an IF band changeover switch 107, an asynchronous quadrature demodulator 108, a data sampling unit 109, a DFE 110, and a frame sync unit 111.

The operation of the equalizer / demodulator configured as described above will be described below with reference to FIG.

First, two systems of modulated signals received by two systems of antennas 101 and 102 are received by a receiving unit 102 and
After being frequency-converted to the IF band by 103, the band is limited by band-limiting filters 105 and 106. The band-limited received signals of the two IF bands are transmitted to the switch 10.
The signal is switched at time intervals of half the symbol rate at 7, and is converted into a quadrature baseband signal by a 108 quadrature demodulator asynchronously. The converted quadrature baseband signal is 1
In the data sampling unit 09, each symbol is sampled by an integer multiple of 2 and converted into digital data, and then sent to the frame sync unit 111. The frame sync unit 111 generates a frame synchronization signal from the transmitted orthogonal digital data using the sequence correlation. The correlation signal obtained at this time is sent to data sampling section 109. In the data sampling unit 109, from among the sampled orthogonal baseband signals,
Based on the correlation signal sent from the frame sync unit 111, a signal sampled at the timing with the strongest sequence correlation is selected from the two-system received signal and used as the DFE input signal of 110. DFE110
Performs an equalization process on the input signal to obtain equalized demodulated data.

Next, the data sampling timing will be described with reference to FIG. In FIG.
FIG. 2A shows data before sampling 201 in FIG.
Reference numeral 202 denotes an operation clock of the changeover switch, and FIG.
203 in (c) is a sampling clock.

The quadrature demodulated data of the two systems are switched by a switching clock 202, and the data 201
Becomes Data 201 is a sampling clock 203
Thus, sampling is performed a plurality of times at each switching timing. From the sampled data, one having a timing with a strong serial correlation is selected and input to the equalizer.

According to the present embodiment, the sampling unit 1
09 and the frame sync unit 111, and the received data at the sampling timing having strong serial correlation is input to the equalizer, whereby the error rate improvement characteristics of the equalizer can be improved.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

In FIG. 3, reference numeral 301 in FIG. 3A denotes data before sampling, 302 in FIG. 3B denotes an operation clock of the changeover switch, and 303 in FIG. 3C denotes a sampling clock.

The orthogonally demodulated data of the two systems are switched by a switching clock 302 for each symbol of an integral multiple of 2 or more, and become data 301.
The data 301 is sampled once by the sampling clock 303 at each switching timing. From the sampled data,
A timing with a strong sequence correlation is selected and input to the equalizer.

The block configuration of the equalizer / demodulator in the present embodiment is the same as that in the first embodiment.

As described above, according to the present embodiment, the error rate improvement characteristic of the equalizer is improved by combining the sampling unit and the frame sync unit and using the received data at the sampling timing having a strong serial correlation as the input to the equalizer. Can be done. In the first and second embodiments, the total number of antennas is 2
However, any number may be used as long as it is an integer of 2 or more.

[0022]

As described above, the present invention provides an IF switch unit for switching a plurality of IF band signals at intervals of a fraction of the number of receiving antennas, and a quadrature baseband for switching the switched IF band signals by asynchronous quadrature detection. A quadrature demodulation unit for converting the signal into a signal, and a quadrature baseband signal obtained by asynchronous quadrature detection.
By providing a sampling unit that samples at an integer multiple of 2 or more of the number of receiving antennas per symbol and a frame sync unit that performs frame synchronization using sequence correlation from the sampled orthogonal baseband signal, sampling timing with strong sequence correlation Can be input to the equalizer, and an equalizer / demodulator having excellent error rate improvement characteristics can be realized. .

[Brief description of the drawings]

FIG. 1 is a block diagram of an equalizer / demodulator according to a first embodiment of the present invention;

FIG. 2 is a clock timing chart of the equalizer / demodulator in the first embodiment.

FIG. 3 is a clock timing chart of an equalizer / demodulator according to a second embodiment of the present invention;

FIG. 4 is a block diagram of a conventional frame signal processing device.

[Explanation of symbols]

 101, 102, 401, 402 Receiving antenna 103, 104, 403, 404 Receiving unit 105, 106, 405, 406 BPF 107, 407 Changeover switch 108, 408 Quadrature demodulating unit 109, 409 Data sampling unit 110, 410 DFE 111 Frame sync Unit 201, 301 Data before sampling 202, 302 Switching clock 203, 303 Sampling clock

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B ⁷ /005-7/015

Claims (2)

(57) [Claims] 1. A plurality of receiving antennas, a receiving unit for converting a received modulated signal in a carrier band into an intermediate frequency band, a band limiting filter having a minimum bandwidth required for reception in the intermediate frequency band, An intermediate frequency band switch unit that switches the signal of the intermediate frequency band at intervals of a fraction of a symbol of a receiving antenna, and a quadrature demodulation unit that converts the switched intermediate frequency band signal into a quadrature baseband signal by asynchronous quadrature detection, A sampling unit that samples an orthogonal baseband signal subjected to asynchronous quadrature detection at an integer multiple of 2 or more per symbol, and a frame sync unit that performs frame synchronization from the sampled orthogonal baseband signal using sequence correlation; A transbar in which the tap interval of the feedforward filter is one symbol of the total number of receiving antennas An equalization demodulator including a monkey type decision feedback equalizer. 2. A plurality of receiving antennas, a receiving section for converting a received modulated signal in a carrier band into an intermediate frequency band, and a band limiting filter having a minimum bandwidth required for reception in the intermediate frequency band. , A plurality of intermediate frequency band signals
An intermediate frequency band switching unit that switches at an integer multiple of two or more of the number of receiving antennas per symbol, a quadrature demodulation unit that converts a signal of the switched intermediate frequency band into a quadrature baseband signal by asynchronous quadrature detection, and a quadrature with asynchronous quadrature detection The sampling unit that samples the baseband signal in accordance with the switching timing of the intermediate frequency band switch unit, the frame sync unit that performs frame synchronization from the sampled orthogonal baseband signal using serial correlation, and the tap interval of the feedforward filter are received. An equalization demodulator including a decision feedback equalizer that is one symbol of the total number of antennas.