JP2001203666A - Ofdm receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an OFDM receiver that can extract an effective symbol signal having a sufficient signal strength from which delayed wavs having delay times more than a guard interval time are eliminated. SOLUTION: The OFDM receiver has antennas 11a and 11b, reception means 12a and 12b that process received signals to convert them into base band signals, delay equalization means 131a and 131b that eliminate signal components delayed more than a guard interval time of an OFDM modulation signal from each of output signals from the means 12a and 12b, a diversity synthesis means 100 that synthesizes output signals form the delay equalization means 131a and 131b, and an OFDM demodulation means 17 that extracts an effective symbol signal from an output signal from the diversity synthesis means 10 to demodulate the OFDM modulation signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus for OFDM-modulated signals such as terrestrial digital TV broadcasting in Japan and Europe, and more particularly to a diversity receiving type OFDM receiving apparatus suitable for use in vehicles.

[0002]

In recent years, OFDM (O rthogonal F requenc as a transmission (modulation) scheme of the digital audio signal and the video signal represented by digital terrestrial TV broadcasting
y D ivision M ultiplexing, orthogonal frequency division multiplexing) by the multi-carrier (multi-carrier) modulation scheme is being put to practical use. Broadcasting by this modulation method divides coded data, distributes the data to one thousand to several thousand or more carrier waves, multiplexes and transmits the multiplexed data. FIG. 12 is a block diagram showing the configuration of an OFDM transmitting apparatus, and FIG. 13 conceptually shows a modulation process by OFDM.

In FIG. 12, OFDM modulation means 191
A modulation means 192 for modulating an input digital signal such as QPSK, a serial / parallel conversion means (S / P) 193 for converting a modulated serial signal into a parallel signal, and an inverse parallel signal Fast inverse Fourier transform means (IFFT) 194 for performing Fourier transform, parallel / serial transform means (P / S) 195 for converting the inverse Fourier transformed signal into a serial sequence and outputting it as a time signal, Guard interval insertion means 1 for inserting a guard interval
96. 197 is a transmitting means (TX), and 198 is an antenna.

In the above configuration, an input digital signal is modulated by a modulation means 192 in a predetermined modulation scheme (for example,
As shown in FIG. 13, a modulation symbol obtained by performing information modulation by QPSK modulation is converted into a lower-speed modulation symbol sequence by a serial / parallel converter (S / P) 193.
That is, the modulation symbols are converted into N modulation symbol sequences of mutually orthogonal carrier waves arranged at a constant frequency interval (Δf). This modulation symbol sequence is subjected to fast inverse Fourier transform (IFFT) 194 by fast inverse Fourier transform (IFFT) means 194.
T), and the output of the fast inverse Fourier transform means (IFFT) 194 is converted to a serial series by a parallel / serial conversion means (P / S) 195 and output as a time signal, and the in-phase component of the orthogonal time axis signal (Hereinafter referred to as I) and orthogonal components (hereinafter referred to as Q) are generated.

Further, guard interval inserting means 19
6, a predetermined time (guard interval time) at the end of the signal divided by a predetermined time (effective symbol time) Ts
Tg is copied and inserted at the start of the time axis signals I and Q, and this is used as a guard interval. The time axis signal into which the guard interval has been inserted as described above is generated from the guard interval inserting means 196 as a baseband time-series signal.

[0006] The guard interval is inserted to prevent delayed wave interference (interference) generated during reception.
This symbol absorbs adjacent symbol interference due to the relative delay of a signal in a multipath environment. Here, (Tg + T
s) A time axis signal of time is treated as one unit of OFDM symbol, and the guard interval is removed by processing at the time of reception, and only a signal of Ts time is extracted as an effective symbol signal and demodulated. Then, the baseband time-series signal generated by the guard interval insertion unit 196 is put on a predetermined carrier by a transmission unit (TX) 197 including a D / A conversion unit, and after being power-amplified, radiated into space from an antenna 198. You.

Next, FIG. 14 conceptually shows a configuration of a basic OFDM receiver, and FIG. 15 conceptually shows a demodulation process by OFDM. In FIG. 14, the OFDM receiving apparatus has an antenna 212, a receiving unit (REC) 213, and an OFDM demodulating unit 211. Further, the OFDM demodulation unit 211 removes a guard interval from the received signal to extract an effective symbol signal, and a serial / parallel conversion unit (S / P) 215 that converts the effective symbol signal into a parallel signal. , A fast Fourier transform means (FFT) 216 for performing a Fourier transform on the parallel signal, a parallel / serial transform means (P / S) 217 for converting the parallel signal into a serial signal, and a demodulation means 218.

In FIG. 14, a signal radio wave captured by an antenna 212 is amplified and frequency-converted by a receiving means (REC) 213, output as a baseband time-series signal, and demodulated by an OFDM demodulating means 211. In the OFDM demodulation means 211, as shown in FIG.
With reference to the FDM symbol, a sum of products of two symbol signals separated by a time Ts is calculated over a time Tg to generate an autocorrelation signal, which is used as a reference signal. Next, OFDM
The peak (maximum value) of the reference signal (autocorrelation signal) of the symbol is detected, the start time of the inserted guard interval is detected based on the peak of the autocorrelation signal, and the guard interval is removed to remove the I of the effective symbol. , Q are extracted.

Next, serial / parallel conversion means (S / P) 21
5 converts the effective symbol signal into a parallel signal, and converts the converted parallel signal into a fast Fourier transform means (FFT) 216.
To perform fast Fourier transform (FFT) to extract modulation symbols of N carrier waves whose frequencies are shifted by Δf. The modulation symbol thus extracted is converted into a serial time series by a parallel / serial conversion means (P / S) 217, and then demodulated by a demodulation means 218 in a predetermined manner to decode a digital signal.

As described above, the peak (maximum value) of the received reference signal (autocorrelation signal) of the OFDM symbol is detected, and the effective symbol is extracted based on the peak of the autocorrelation signal. If not detected, the data of the OFDM symbol adjacent to the extracted effective symbol will be included, causing a problem that a bit error occurs. On the other hand, when a broadcast signal based on OFDM modulation is received while moving in a car or the like, the signal is affected by fading and the received signal level fluctuates, so that a reference signal cannot be accurately generated. As a result, a bit error as described above occurs, so that the level fluctuation is suppressed by diversity reception during mobile reception.

[0011]

However, in the above-described conventional OFDM receiver, even if diversity reception is performed, a delay wave delayed more than the guard interval time (Tg) of the OFDM symbol is mixed. ,
There has been a problem that adjacent valid symbols interfere with each other and the number of bit errors after demodulation increases. The present invention has been made in view of such circumstances, and has a sufficient signal strength by providing a diversity combining unit and a delay equalizing unit at a stage preceding the Fourier transform processing unit of an OFDM modulated signal, and An object of the present invention is to provide a diversity reception type OFDM receiving apparatus capable of extracting an effective symbol signal from which a delay wave having a delay time equal to or longer than a guard interval time has been removed.

[0012]

In order to achieve the above object, an OFDM receiving apparatus according to the present invention is provided with a plurality of antennas arranged at a distance from each other to capture an OFDM-modulated signal, and A plurality of receiving means connected to each other to process a supplied signal into a baseband signal, and connected to each output side of the plurality of receiving means, and each output signal is delayed by at least a guard interval time of an OFDM modulated signal. A plurality of delay equalizing means for removing signal components, a diversity combining means for combining respective output signals of the plurality of delay equalizing means, and a guard interval signal inserted at the time of modulation from an output signal of the diversity combining means. OFD for removing, demodulating and extracting effective symbol signals
M demodulation means.

In the OFDM receiver according to the present invention, a plurality of antennas spaced apart from each other capture OFDM-modulated signals, and signals supplied by a plurality of receiving means connected to the plurality of antennas are used. It is processed and converted to a baseband signal. Next, OFDM signals are output from the output signals of the plurality of receiving units by a plurality of delay equalizing units connected to the respective output sides of the plurality of receiving units.
Signal components of the modulated signal that are delayed more than the guard interval time are removed, and the output signals of the plurality of delay equalizers are synthesized by the diversity synthesizer. The guard interval signal inserted at the time of modulation is removed from the output signal of the diversity combining means by the OFDM demodulating means,
An effective symbol signal is extracted and demodulated.

In the OFDM receiver according to the present invention, an autocorrelation detecting means for detecting an autocorrelation of each output signal of the plurality of receiving means is connected to an output side of the plurality of receiving means, Means for removing signal components of the OFDM modulated signal which are delayed by a guard interval time or more based on the detection result of the autocorrelation detecting means.

In the OFDM receiver according to the present invention, an autocorrelation detecting means connected to an output side of the plurality of receiving means detects an autocorrelation of each output signal of the plurality of receiving means, Based on the detection result, the signal components of the OFDM modulated signal that are delayed by the guard interval time or more are removed by the delay equalizing means.

Further, in the OFDM receiving apparatus according to the present invention, the delay equalizing means may be configured such that, among the autocorrelation values detected by each of the autocorrelation detecting means, the maximum autocorrelation value other than the maximum autocorrelation value is the maximum autocorrelation value. A plurality of feedback means for negatively feeding back an output signal of the delay equalization means based on a delay time from a correlation value and a complex amplitude coefficient calculated from the maximum autocorrelation value.

In the OFDM receiving apparatus according to the present invention, among the autocorrelation values detected by each of the autocorrelation detecting means, the maximum autocorrelation value other than the maximum autocorrelation value is obtained by the plurality of feedback means included in the delay equalizing means. The output signal of the delay equalizer is negatively fed back based on the delay time from the maximum autocorrelation value and the complex amplitude coefficient calculated from the maximum autocorrelation value.

The OFDM receiver according to the present invention is also characterized in that the autocorrelation detecting means outputs an effective symbol time delay means for delaying a signal supplied to the autocorrelation detecting means by an effective symbol time; A complex conjugate signal generating means for generating and outputting a complex conjugate signal from the signal supplied to the autocorrelation detecting means, a multiplying means for multiplying the delayed signal and the complex conjugate signal, and a multiplication result of the multiplying means And accumulating means for accumulating for a predetermined time.

In the OFDM receiving apparatus according to the present invention, the autocorrelation detecting means outputs a delayed signal obtained by delaying the signal supplied to the autocorrelation detecting means by the effective symbol time delaying means by an effective symbol time, and outputs a complex conjugate signal. A complex conjugate signal is generated from the signal supplied to the autocorrelation detecting means by the signal generating means and output. Further, the multiplication means multiplies the delayed signal and the complex conjugate signal, and the accumulation means accumulates the multiplication result of the multiplication means for a predetermined time.

In the OFDM receiver according to the present invention, first cross-correlation detecting means for detecting a cross-correlation between output signals of the plurality of receiving means is connected to an output side of the plurality of receiving means, Diversity combining means has signal combining means and the first cross-correlation detecting means, and the signal combining means converts each output signal of the delay equalizing means based on a detection result of the first cross-correlation detecting means. It is characterized in that the phase is corrected and the phases are combined.

In the OFDM receiver according to the present invention, the first cross-correlation detecting means connected to the output side of the plurality of receiving means detects a cross-correlation between output signals of the plurality of receiving means. In the diversity combining means, the signal combining means corrects each output signal of the delay equalizing means to have the same phase based on the detection result of the first cross-correlation detecting means, and combines them.

In the OFDM receiver according to the present invention, a second cross-correlation detecting means for detecting a cross-correlation between respective output signals of the delay equalizing means is connected to each output side of the delay equalizing means. The diversity combining means includes a signal combining means and the second cross-correlation detecting means, and the signal combining means is configured to control each of the delay equalizing means based on a detection result of the second cross-correlation detecting means. It is characterized in that the output signals are corrected to have the same phase and then synthesized.

In the OFDM receiving apparatus according to the present invention, the cross-correlation between the output signals of the delay equalizing means is detected by the second cross-correlation detecting means connected to each output side of the delay equalizing means. . In the diversity combining means, the signal combining means corrects each output signal of the delay equalizing means to have the same phase based on the detection result of the second cross-correlation detecting means and combines them.

Further, in the OFDM receiving apparatus according to the present invention, the first cross-correlation detecting means or the second cross-correlation detecting means may be a first cross-correlation detecting means or a second cross-correlation detecting means. Complex conjugate signal generating means for generating and outputting a complex conjugate signal from one of the signals supplied to the first and second signals, and multiplying the complex conjugate signal by another of the two signals to be compared And multiplying means for accumulating the multiplication result of the multiplying means for a predetermined time.

In the OFDM receiver according to the present invention, the first
In the cross-correlation detecting means or the second cross-correlation detecting means, one of the signals supplied to the first cross-correlation detecting means or the second cross-correlation detecting means by the complex conjugate signal generating means. A complex conjugate signal is generated and output from the signal, and the complex conjugate signal is multiplied by another of the two signals to be compared by a multiplication means,
The accumulating means accumulates the multiplication result of the multiplying means for a predetermined time.

In the OFDM receiving apparatus according to the present invention, an autocorrelation detecting means for detecting an autocorrelation of each output signal of the plurality of receiving means is connected to an output side of the plurality of receiving means, Means for removing signal components of the OFDM modulated signal delayed by a guard interval time or more based on the detection result of the autocorrelation detection means, and the signal synthesizing means detects the detection result of the autocorrelation detection means and the first signal.
The output signals of the plurality of delay equalizers are corrected to have a predetermined amplitude and the same phase based on the detection result of the cross-correlation detector, and then synthesized and output.

In the OFDM receiver according to the present invention, the autocorrelation of each output signal of the plurality of receiving means is detected by the autocorrelation detecting means connected to the output side of the plurality of receiving means. The delay equalizer removes signal components of the OFDM modulated signal that are delayed by the guard interval time or more based on the detection result of the autocorrelation detector. The signal synthesizing unit corrects each output signal of the plurality of delay equalizing units to a predetermined amplitude and the same phase based on the detection result of the autocorrelation detecting unit and the detection result of the first cross-correlation detecting unit. It is performed and synthesized and output.

An autocorrelation detecting means for detecting an autocorrelation of each output signal of the plurality of receiving means is connected to an output side of the plurality of receiving means, and the delay equalizing means detects the autocorrelation of the output signals of the plurality of receiving means. Based on the result, the signal components delayed by the guard interval time of the OFDM modulated signal are removed, and the signal synthesizing unit detects the signal component based on the detection result of the autocorrelation detection unit and the detection result of the second cross-correlation detection unit. The output signals of the plurality of delay equalizers are corrected to have a predetermined amplitude and the same phase, and then synthesized and output.

In the OFDM receiving apparatus according to the present invention, the autocorrelation of each output signal of the plurality of receiving means is detected by the autocorrelation detecting means connected to the output side of the plurality of receiving means. The delay equalizer removes signal components of the OFDM modulated signal that are delayed by the guard interval time or more based on the detection result of the autocorrelation detector. The signal synthesizing unit corrects each output signal of the plurality of delay equalizing units to a predetermined amplitude and the same phase based on the detection result of the autocorrelation detecting unit and the detection result of the second cross-correlation detecting unit. It is performed and synthesized and output.

Further, in the OFDM receiving apparatus according to the present invention, the OFDM demodulating means may determine a time point when a maximum autocorrelation value indicating a maximum value among the autocorrelations detected by each of the autocorrelation detecting means is detected. A guard interval signal is removed from an output signal of the diversity combining means, and an effective symbol is extracted.

In the OFDM receiving apparatus according to the present invention,
By the DM demodulation means, a guard interval signal is obtained from the output signal of the diversity combining means based on the time point when the maximum autocorrelation value indicating the maximum value among the autocorrelations detected by each of the autocorrelation detection means is detected. It is removed and the effective symbol is extracted. As described above, the OFD of the present invention
According to the M receiving apparatus, the diversity combining means for performing antenna diversity is provided before the FFT calculating means for performing the FFT calculation on the effective symbol of the OFDM modulated signal;
A delay equalizer for removing a signal component (delay wave) delayed by a predetermined time or more from the FDM modulated signal is provided, and the delay equalizer is provided in front of the diversity unit so as to eliminate the delay wave. Therefore, an output signal having a sufficient CN ratio can be obtained, and a bit error after demodulation can be eliminated.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings. An OFDM receiving apparatus according to each embodiment of the present invention includes a diversity combining means for performing antenna diversity before a FFT calculating means for performing an FFT calculation on an effective symbol of an OFDM modulated signal, and a predetermined time or more for a received OFDM modulated signal. A delay equalizer for removing a delayed signal component (delay wave) is provided, and the delay equalizer is provided before the diversity combiner, thereby removing a signal having a sufficient signal strength and a large delay. An effective symbol signal of the OFDM modulated signal can be extracted.
Hereinafter, a case where the number of antenna elements is 2 in the OFDM receiving apparatus according to each embodiment of the present invention will be described.

FIG. 1 shows an O type according to the first embodiment of the present invention.
2 shows a configuration of an FDM receiver. An OFDM receiving apparatus according to an embodiment of the present invention is configured to perform diversity combining after first removing unnecessary delay waves by delay equalizing means provided for each receiving means. In FIG. 1, an antenna 11a that captures the OFDM-modulated signal of the # 1 system and a # that is arranged separately from the antenna 11a
Antenna 1 for capturing two OFDM-modulated signals
1b, receiving means 12a and 12b, and a plurality of receiving means 1
Cross-correlation detecting means 13 for detecting a cross-correlation between the output signals of 2a and 12b, auto-correlation detecting means 14a for detecting the auto-correlation of the output signal of receiving means 12a, and receiving means 12
autocorrelation detecting means 1 for detecting the autocorrelation of the output signal b
4b.

Further, the OFDM receiving apparatus according to the present embodiment includes a delay equalizing means 131a for removing a signal component delayed by a predetermined time or more from an output signal of the receiving means 12a based on a detection result of the autocorrelation detecting means 14a. A delay equalizer 131b for removing a signal component delayed for a predetermined time or more from an output signal of the receiver 12b based on a detection result of the autocorrelation detector 14b, and a delay based on a detection result of the cross-correlation detector 13. It has a signal combining means 133 for combining output signals of the equalizing means 131a and 131b by a predetermined diversity method, and an OFDM demodulating means 17 for demodulating an output signal of the signal combining means 133. Here, the cross-correlation detecting means 13 and the signal synthesizing means constitute a diversity combining unit 100. Further, the cross-correlation detecting means 1
Reference numeral 3 corresponds to first cross-correlation detecting means of the present invention. The specific configuration of the OFDM demodulation means 17 is a known OFDM demodulation means.
This is the same as the DM demodulation means 211.

In the above configuration, the signals received by the antennas 11a and 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals. The signals are input to the delay equalizers 131a and 131b. In the delay equalizers 131a and 131b, the receiving means 1 based on the detection results of the autocorrelation detectors 14a and 14b.
Signal components delayed from the output signals 2a and 12b by a predetermined time or more, specifically, by a guard interval time or more of the OFDM modulated signal are removed.

The output signals of the delay equalizers 131a and 131b are supplied to the signal combiner 133 by the cross-correlation detector 1.
Based on the detection result of No. 3, the phase is corrected so as to have the same phase, and diversity combining is performed. Next, the signal combining means 1
The OFDM demodulation unit 17 removes guard symbols of the guard interval inserted at the time of modulation from the combined output of 33, and extracts and demodulates effective symbols.

As described above, according to the OFDM receiving apparatus according to the first embodiment of the present invention, the plurality of receiving means 12a and 12b are provided before the diversity combining of the output signals of the plurality of receiving means 12a and 12b. The cross-correlation detection between the respective output signals and the auto-correlation detection of the respective output signals of the receivers 12a and 12b are performed. The unnecessary signal delayed by the guard interval time or more is removed from each output signal of
Diversity combining is performed on the output signals 1a and 131b based on the cross-correlation detection result, so that a delayed wave (unwanted wave) having a sufficient signal strength and a delay time longer than the guard interval time is generated. The removed effective symbol signal can be extracted.

Next, the delay equalizing means 131a shown in FIG.
FIG. 2 shows a specific configuration of (131b). The delay equalizing means 131a (131b) shown in the figure is configured to perform delay equalization up to two signals. 2, the delay equalizing means 131a (131b) includes an adding means 91,
Delay means 9 for delaying the output of adder 91 for a predetermined time
2, 94; and complex amplitude correction means 93, 95 for correcting the complex amplitudes of the output signals of the delay means 92, 94, respectively.
A delay time calculating means 97 for calculating a delay time in the delay means 92 and 94; a complex amplitude coefficient calculating means 98 for calculating a complex amplitude coefficient which is an amplitude correction amount in the complex amplitude correcting means 93 and 95; It has a maximum local autocorrelation search means 96 for searching for a maximum value and a local maximum value from the values.

Here, one delayed signal is removed by the negative feedback means of the signal constituted by the delay means 92 and the complex amplitude correction means 93, and the delay means 94 and the complex amplitude correction means 95 Another delayed signal is removed by means of the negative feedback of the constructed signal.

In FIG. 2, when the auto-correlation value is supplied from the auto-correlation detecting means 14a (14b), the maximum auto-correlation searching means 96 searches the auto-correlation maximum value and the maximum value from them. Then, the control signal relating to the maximum value and the maximum value of the autocorrelation is sent to the delay time calculating means 97 and the complex amplitude coefficient calculating means 98. Maximum local autocorrelation search means 96
The delay time calculating means 97 receives the control signal from the maximum auto-correlation value and uses the maximum auto-correlation value as a reference. The time until the correlation value is detected is calculated, and the calculated time is used as a delay time.
94.

Here, the calculated delay time is a predetermined time,
Specifically, when the time is shorter than the guard interval time included in the OFDM modulated signal, the delay time to be transmitted is set to zero. Further, upon receiving the control signal from the maximum local autocorrelation searching means 96, the complex amplitude coefficient calculating means 98 should remove the maximum autocorrelation value from the maximum autocorrelation values other than the maximum autocorrelation value based on the maximum autocorrelation value. The respective ratios to the maximum autocorrelation values corresponding to the two delayed signals are calculated and sent to the complex amplitude correction means 93 and 95 as complex amplitude coefficients.

Here, in the delay time calculating means 97 and the complex amplitude coefficient calculating means 98, the autocorrelation detecting means 14a
The delay time and the complex amplitude correction coefficient are calculated with reference to the autocorrelation value supplied from (14b). Delay means 92, 9
4 delays the input signal based on the delay time provided by the delay time calculating means 97. Here, when the given delay time is zero, the delay time of the delay signal is equal to or less than the guard interval time of the OFDM modulation signal, and there is no need to remove the delay signal. Is output. The complex amplitude correction means 93 and 95 perform amplitude correction based on the complex amplitude coefficient given by the complex amplitude coefficient calculation means 98.

As described above, the addition means 9 is passed through the negative feedback means including the delay means 92 and 94 and the amplitude correction means 93 and 95.
1 is negatively fed back and supplied to the input of the same adding means 91. In the configuration shown in FIG. 1, the receiving means 12a (1
The output signal of 2b) is provided to the adding means 91, and the output of the adding means 91 is based on the delay time and the complex amplitude coefficient given by the delay time calculating means 97 and the complex amplitude coefficient calculating means 98. The delay time adjustment and the amplitude adjustment are performed by the 94 and the complex amplitude correction means 93 and 95, and the signals subjected to the delay time adjustment and the amplitude correction are added by the addition means 91 with the opposite polarity. As a result, the signal component delayed from the output signal of the receiving means signal 12a (12b) by the guard interval time of the OFDM modulated signal is removed, and the signal from which the unnecessary wave is removed is converted to the signal combining means 133.
Is output to

Next, a specific configuration of the signal synthesizing means 133 in FIG. 1 is shown in FIG. In the figure, the signal combining means 133 has phase shifting means 21 and 22 and an adding means 23. In the figure, delay equalizing means 131a, 131
The output signals b are phase-corrected by the phase shift means 21 and 22 so as to be in phase with each other with reference to the detection result (cross-correlation value) of the cross-correlation detection means 13, added by the addition means 23 and combined, The signal is output to the OFDM demodulation unit 17. Thus, when diversity combining is performed in phase,
The power of the combined output can be maximized.

Next, the autocorrelation detecting means 14 shown in FIG.
FIG. 4 shows a specific configuration of a (or 14b). In FIG. 4, the autocorrelation detecting means 14a (or 14b)
An effective symbol time delay means 50 for outputting a delayed signal obtained by delaying a signal supplied to the autocorrelation detection means 14a (or 14b) by an effective symbol time, and a signal supplied to the autocorrelation detection means 14a (or 14b) Complex conjugate signal generation means 51 for generating and outputting a complex conjugate signal
A multiplying means 52 for multiplying the delayed signal by the complex conjugate signal; and an accumulating means 53 for accumulating the multiplication result of the multiplying means 52 for a predetermined time.

In the above configuration, the autocorrelation detecting means 14
a (or 14b), the effective symbol time delay means 5
0 outputs a delayed signal obtained by delaying the signal supplied from the input terminal 144 to the autocorrelation detecting means by the effective symbol time, and outputs a complex conjugate signal from the signal supplied from the input terminal 144 by the complex conjugate signal generating means 51. A signal is generated and output. The delayed signal and the complex conjugate signal are multiplied by a multiplying unit 52, and the multiplication result of the multiplying unit 52 is accumulated by an accumulating unit 53 for a predetermined time. Further, the autocorrelation value as the accumulation result of the accumulation means 53 is output from the output terminal 145 to the delay equalization means 131a (131b).

Next, the cross-correlation detecting means 13 shown in FIG.
FIG. 5 shows a specific configuration of the first embodiment. In FIG. 5, a cross-correlation detecting unit 13 generates a complex conjugate signal from one of two signals to be compared among signals supplied to the cross-correlation detecting unit 13 and outputs the complex conjugate signal. Means 6
0, a multiplying unit 61 for multiplying the complex conjugate signal generated by the complex conjugate signal generating unit 60 with another of the two signals to be compared, and a multiplication result by the multiplying unit 61 for a predetermined time. And accumulating means 62 for accumulating only the data.

In the above configuration, the cross-correlation detecting means 13
In one of the signals supplied to the cross-correlation detecting means 13 via the input terminals 140 and 141, one of the two signals to be compared (the signal input from the input terminal 141) is used to generate a complex conjugate signal. The complex conjugate signal is generated by the complex conjugate signal generation means 60 and output. The complex conjugate signal obtained by the complex conjugate signal generation means 60 and another signal of the two signals to be compared (the signal input from the input terminal 140).
Are multiplied by the multiplication means 61.

Further, the multiplication result obtained by the multiplication means 61 is accumulated by the accumulation means 62 for a predetermined time,
The cross-correlation value as the accumulation result is output from the output terminal 142 to the signal combining means 133.

Next, the data configuration of the OFDM modulated signal and the operation of removing the delayed wave in the OFDM receiving apparatus having the above configuration will be described with reference to FIG. 6 and FIG. FIG. 6 shows O
4 shows a relationship between a data configuration of an FDM modulated signal and an autocorrelation detection signal. At the time of OFDM modulation, a signal for a predetermined time at the end of the effective symbol is copied to the head of the effective symbol as a guard interval, and the signal of the sum of the guard interval and the effective symbol is transmitted as an OFDM symbol.

Therefore, at the time of demodulation, it is necessary to remove the copied guard interval and extract the effective symbol signal. However, if the autocorrelation of the received signal is obtained by the autocorrelation detecting means, the autocorrelation value is obtained at the start of the guard interval signal. Since the autocorrelation value of the received signal is monitored, the OFDM receiver
The output timing of M symbols can be recognized.

FIG. 7 shows the effect of a delayed wave of an OFDM modulated signal including a delayed wave on an effective symbol of a composite wave. In the figure, it is assumed that the main wave, the delayed wave 1 and the delayed wave 2 are received by the OFDM receiving apparatus according to the present embodiment. The main wave of the received signal wave is a unit OFD between time t11 and t21 by detecting the maximum value of the autocorrelation.
It is recognized that M symbols i are formed, and OFDM
The output period of the symbol i includes a valid symbol output period and a guard interval period based on a signal copied from the end of the valid symbol.

Similarly, the delayed wave 1 has a maximum auto-correlation value next to the maximum auto-correlation value among the detected auto-correlation values. By detecting the next maximum autocorrelation value, it is recognized that the unit OFDM symbol i is formed between times t13 and t23. Here, O of delayed wave 1
Since the FDM symbol start timing t12 is within the guard interval of the main wave, it does not directly interfere. However,
Since the delayed wave 2 has a large delay time and the OFDM symbol start timing t13 is later than the guard interval period of the main wave, the symbol i of the synthesized wave after detecting the effective symbol includes:
The end part of the symbol (i-1) of the delayed wave 2 is included, and it becomes an interference area in the effective symbol.

Therefore, OFD signal having a delay time longer than the guard interval period of the main wave of the received signal is used.
It is necessary to eliminate the delayed wave in which the M symbol starts, and as described above with reference to FIG.
The signal from which the delayed wave has been eliminated by the negative feedback means in 31b) is input to the signal combining means 133, and after being subjected to diversity combining, it is demodulated by the OFDM demodulation means 17 to obtain a good demodulated signal.

As described above, according to the OFDM receiving apparatus according to the first embodiment of the present invention, the plurality of receiving means 12a and 12b are output before the diversity combining of the output signals of the plurality of receiving means 12a and 12b. , And autocorrelation detection of each output signal of the receiving means 12a and 12b, and based on the autocorrelation detection result, the delay equalizing means 131a and 131b detect the plurality of receiving means 12a and 12b. Since unnecessary delayed waves are removed from each output signal and each output signal of the delay equalizing means 131a and 131b is subjected to diversity combining based on the result of the cross-correlation detection, it has sufficient signal strength and An OFDM receiver capable of extracting an effective symbol signal from which a delayed wave having a delay time equal to or longer than a guard symbol time has been removed can be obtained.

Next, an OF according to a second embodiment of the present invention will be described.
FIG. 8 shows the configuration of the DM receiver. The OFDM receiving apparatus according to the embodiment of the present invention employs the OFDM receiving apparatus according to the first embodiment.
The difference from the FDM receiver in configuration is that the cross-correlation detection result used in the diversity combining means is received by the receiving means 12a,
12b, the delay equalization means 1
31a and 131b.
Other configurations are the same. The cross-correlation detecting means 1
Reference numeral 32 denotes the same configuration as the cross-correlation detecting means 13 shown in FIG.

Referring to FIG. 8, an OFDM receiving apparatus according to an embodiment of the present invention includes an antenna 11a for capturing an OFDM-modulated signal of # 1 system, and an OFDM receiving system of # 2 system separated from antenna 11a. An antenna 11b for capturing the modulated signal, receiving means 12a and 12b,
It has an autocorrelation detecting means 14a for detecting the autocorrelation of the output signal of the receiving means 12a, and an autocorrelation detecting means 14b for detecting the autocorrelation of the output signal of the receiving means 12b.

The OFDM receiving apparatus according to the present embodiment includes a delay equalizing means 131a for removing a signal component delayed by a predetermined time or more from an output signal of the receiving means 12a based on a detection result of the autocorrelation detecting means 14a. And a delay equalizer 131b for removing a signal component delayed for a predetermined time or more from the output signal of the receiver 12b based on the detection result of the autocorrelation detector 14b.

Further, the OFDM receiving apparatus according to the present embodiment is based on the cross-correlation detecting means 132 for detecting the cross-correlation between the output signals of the delay equalizing means 131a and 131b and the detection result of the cross-correlation detecting means 132. Delay equalization means 1
A signal synthesizing unit 133 for synthesizing the output signals of the signals 31a and 131b by a predetermined diversity system;
And an OFDM demodulating means 17 for demodulating the output signal of the output signal 33. Cross-correlation detecting means 132 and signal synthesizing means 1
Reference numeral 33 denotes the diversity combining means 101. The cross-correlation detecting means 132 corresponds to the second cross-correlation detecting means of the present invention.

In the above configuration, the signals received by the antennas 11a and 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals. The signals are input to the delay equalizers 131a and 131b.

The delay equalizers 131a and 131b detect the output signals of the receivers 12a and 12b for a predetermined time or more based on the detection results of the autocorrelation detectors 14a and 14b.
Specifically, a signal component of the OFDM modulated signal that is delayed by a guard interval time or more is removed. Delay equalization means 13
The output signals of 1a and 131b are phase-corrected by the signal combining means 133 based on the detection result of the cross-correlation detecting means 132 which detects the cross-correlation of the output signals of the delay equalizing means 131a and 131b. And diversity synthesis.

Next, the OFDM demodulation unit 17 removes the guard interval inserted at the time of modulation from the combined output of the signal combining unit 133, and extracts and demodulates only effective symbols.

As described above, according to the OFDM receiving apparatus according to the second embodiment of the present invention, the plurality of receiving means 12a and 12b are output before the diversity combining of the output signals of the plurality of receiving means 12a and 12b. Of the respective output signals, and based on the result of the autocorrelation detection, the delay equalizers 131a and 131b detect the plurality of receivers 12.
a, 12b to remove unnecessary waves delayed from each output signal,
Each of the output signals of the delay equalizers 131a and 131b is subjected to diversity combining based on the result of cross-correlation detection between the output signals of the delay equalizers 131a and 131b. An OFDM receiving apparatus capable of extracting an effective symbol signal from which a delayed wave having a delay time equal to or longer than the guard symbol time has been removed can be obtained.

Next, the O according to the third embodiment of the present invention will be described.
FIG. 9 shows the configuration of the FDM receiver. The OFDM receiver according to the embodiment of the present invention is the ODM receiver according to the first embodiment.
The difference from the FDM receiver in configuration is that the signal combining means 1
Reference numeral 5 denotes each output of the delay equalizers 131a and 131b based on the autocorrelation detection result of each output signal of the plurality of receivers 12a and 12b and the cross-correlation detection result between each output signal of the plurality of receivers 12a and 12b. The difference is that signals are diversity-combined, and the other configurations are the same.

In FIG. 9, an antenna 11a for capturing the OFDM-modulated signal of the # 1 system and an antenna 11a
Antenna 11b for capturing OFDM-modulated signals of # 2 system, which are arranged at a distance from the antenna, and receiving means 12a and 12b
b, a cross-correlation detecting means 13 for detecting a cross-correlation between output signals of the plurality of receiving means 12a and 12b, and a receiving means 1
It has an autocorrelation detecting means 14a for detecting the autocorrelation of the output signal of 2a, and an autocorrelation detecting means 14b for detecting the autocorrelation of the output signal of the receiving means 12b.

Further, the OFDM receiving apparatus according to the present embodiment comprises a delay equalizing means 131a for removing a signal component delayed from the output signal of the receiving means 12a by a predetermined time or more based on the detection result of the autocorrelation detecting means 14a. A delay equalizer 131b for removing a signal component delayed from the output signal of the receiver 12b by a predetermined time or more based on the detection result of the autocorrelation detector 14b; and an autocorrelation detector 14a, 1
Signal combining means 1 for combining the output signals of the delay equalizing means 131a and 131b by a predetermined diversity method based on the detection result of 4b and the detection result of the cross-correlation detecting means 13.
51, an OF for demodulating the output signal of the signal synthesizing means 151
DM demodulation means 17. Here, the cross-correlation detecting means 13 and the signal combining means 151 constitute the diversity combining means 102.

In the above configuration, the signals received by the antennas 11a and 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals. The signals are input to the delay equalizers 131a and 131b. In the delay equalizers 131a and 131b, the receiving means 1 based on the detection results of the autocorrelation detectors 14a and 14b.
Signal components delayed from the output signals 2a and 12b by a predetermined time or more, specifically, by a guard interval time or more of the OFDM modulated signal are removed.

The output signals of the delay equalizers 131a and 131b are output from the signal
Based on the detection results of 4a and 14b and the detection result of the cross-correlation detecting means 13, the amplitude is corrected so as to have a predetermined amplitude and the diversity is combined so that the phase is corrected so as to have the same phase. Next, in the OFDM demodulation means 17, the guard interval inserted at the time of modulation is removed from the combined output of the signal combining means 15, and effective symbols are extracted and demodulated.

Next, FIG. 10 shows the configuration of the signal synthesizing means 151 in FIG. Referring to FIG.
1 denotes amplitude correction means 111 and 113, and phase shift means 112,
114 and an adder 115. In the figure, the output signals of the delay equalizers 131a and 131b are:
Predetermined amplitude correction is performed by the amplitude correction units 111 and 113 based on the detection results of the autocorrelation detection units 14a and 14b, and the amplitude-corrected signals are output to the phase shift units 112 and 1.
The phase is corrected by the detection output (control signal) of the cross-correlation detecting means 13 so as to be in phase with each other at 14, added by the adding means 115 and combined, and output to the OFDM demodulating means 17. At this time, the amplitude correction means 11
At 1, 113, the autocorrelation detecting means 14a, 14b
When the amplitude correction is performed in proportion to the maximum value of the detected autocorrelation value, the carrier power-to-noise power ratio (CN ratio) of the combined output output from the adding means 115 can be maximized.

As described above, according to the OFDM receiving apparatus according to the third embodiment of the present invention, the plurality of receiving means 12a and 12b are output before the diversity combining of the output signals of the plurality of receiving means 12a and 12b. The cross-correlation detection between the respective output signals and the auto-correlation detection of the respective output signals of the receivers 12a and 12b are performed. Since unnecessary waves delayed from each output signal are removed and the output signals of the delay equalizers 131a and 131b are subjected to diversity combining based on the autocorrelation detection result and the cross-correlation detection result, a sufficient signal can be obtained. An OFDM receiver capable of extracting an effective symbol signal from which a delayed wave having a strength and a delay time longer than a guard symbol time is removed. Device is obtained.

Next, the O according to the fourth embodiment of the present invention will be described.
FIG. 11 shows the configuration of the FDM receiver. The OFDM receiving apparatus according to the embodiment of the present invention is different from the OFDM receiving apparatus according to the third embodiment in the configuration in that the detection result of the cross-correlation used by the diversity combining means at the time of signal combining is delayed or the like. The cross-correlation detecting means 132 for detecting the cross-correlation between the respective output signals of the converting means 131a and 131b is provided and obtained from the detection result of the cross-correlation detecting means, and the other configuration is the same.

In FIG. 11, an antenna 11a for capturing the OFDM-modulated signal of the # 1 system and an antenna 11
and antennas 11b for capturing OFDM-modulated signals of # 2 system, which are arranged at a distance from the receiving means 12a, and receiving means 12a, 1
2b, an autocorrelation detecting means 14a for detecting the autocorrelation of the output signal of the receiving means 12a, and an autocorrelation detecting means 14b for detecting the autocorrelation of the output signal of the receiving means 12b.

The OFDM receiving apparatus according to the present embodiment includes a delay equalizing means 131a for removing a signal component delayed for a predetermined time or more from an output signal of the receiving means 12a based on a detection result of the autocorrelation detecting means 14a. And a delay equalizer 131b for removing a signal component delayed for a predetermined time or more from the output signal of the receiver 12b based on the detection result of the autocorrelation detector 14b.

Further, the OFDM receiving apparatus according to the present embodiment includes a cross-correlation detecting means 132 for detecting a cross-correlation of each output signal of delay equalizing means 131a and 131b, and a detection result of auto-correlation detecting means 14a and 14b. And delay equalizing means 131 based on the detection result of cross-correlation detecting means 132
a signal synthesizing means 151 for synthesizing the output signals of the signals a and 131b by a predetermined diversity method;
And an OFDM demodulating means 17 for demodulating the output signal. Here, the cross-correlation detecting means 132 and the signal combining means 151 constitute the diversity combining means 103.

In the above configuration, the signals received by the antennas 11a and 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals. The signals are input to the delay equalizers 131a and 131b.

The delay equalizers 131a and 131b detect the output signals of the receivers 12a and 12b for a predetermined time or more based on the detection results of the autocorrelation detectors 14a and 14b.
Specifically, a signal component of the OFDM modulated signal that is delayed by a guard interval time or more is removed. Delay equalization means 13
The output signals of 1a and 131b are subjected to amplitude correction so as to have a predetermined amplitude based on the detection results of the auto-correlation detecting means 14a and 14b and the cross-correlation detecting means 132 in the signal synthesizing means 151, and have the same phase. The diversity is synthesized so that the phase is corrected.

Next, the OFDM demodulator 18 removes the guard interval inserted at the time of modulation from the combined output of the signal combiner 151, and extracts and demodulates only effective symbols.

As described above, according to the OFDM receiving apparatus according to the fourth embodiment of the present invention, the plurality of receiving means 12a, 12b are output before the diversity combining of the output signals of the plurality of receiving means 12a, 12b. Of the respective output signals, and based on the result of the autocorrelation detection, the delay equalizers 131a and 131b detect the plurality of receivers 12.
a, 12b to remove unnecessary waves delayed from each output signal,
The output signals of the delay equalizers 131a and 131b are compared with the autocorrelation detection result and the delay equalizers 131a and 131b.
Diversity combining is performed based on the cross-correlation detection result between each output signal, so that an effective symbol signal having sufficient signal strength and removing a delayed wave having a delay time longer than a guard symbol time is extracted. An OFDM receiving apparatus that can perform the above operations is obtained.

The operation of the OFDM receiver according to the first to fourth embodiments of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Even a design change or the like within a range not departing from the gist of the invention is included in the present invention. For example, the number of input antennas is not limited to two, and three or more antennas are included in the present invention.

In the delay equalizing means, two negative feedback means are provided so as to remove two delayed signals.
Other systems may be included.

[0081]

As described above, according to the present invention, the diversity combining means for performing antenna diversity, the FFT calculating means for performing the FFT calculation on the effective symbol of the OFDM modulated signal, and the received OFDM modulated signal A delay equalizer for removing a signal component (delay wave) delayed for a predetermined time or more is provided, and the delay equalizer is provided in front of the diversity means to eliminate the delay wave. Thus, it is possible to obtain an output signal having a high CN ratio, and to eliminate a bit error after demodulation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an OFDM receiving apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of a delay equalizer in FIG. 1;

FIG. 3 is a block diagram showing a specific configuration of a signal combining unit in FIG. 1;

FIG. 4 is a block diagram showing a specific configuration of an autocorrelation detection unit in FIG. 1;

FIG. 5 is a block diagram showing a specific configuration of a cross-correlation detection unit in FIG. 1;

FIG. 6 is an explanatory diagram showing a relationship between a data configuration of an OFDM modulated signal and an autocorrelation detection signal.

FIG. 7 is an explanatory diagram showing an effect of a delayed wave of an OFDM reception signal including a delayed wave on an effective symbol of a combined wave.

FIG. 8 is a block diagram showing a configuration of an OFDM receiving apparatus according to a second embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of an OFDM receiver according to a third embodiment of the present invention.

FIG. 10 is a block diagram showing a specific configuration of a signal combining unit in FIGS. 8 and 9;

FIG. 11 is a block diagram showing a configuration of an OFDM receiver according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram illustrating a configuration of an OFDM transmission device.

FIG. 13 is an explanatory view conceptually showing a modulation process by OFDM.

FIG. 14 is a block diagram showing a configuration of a conventional basic OFDM receiver.

FIG. 15 is an explanatory view conceptually showing a demodulation process by OFDM.

[Explanation of symbols]

11a, 11b Antennas 12a, 12b Receiving means (REC) 13, 132 Cross-correlation detecting means 14a, 14b Autocorrelation detecting means 133, 151 Signal combining means 131a, 131b Delay equalizing means 17 OFDM demodulating means 21, 22, 112, 114 Phase shift means 23, 91, 115 Addition means 111, 113 Amplitude correction means 50 Effective symbol time delay means 51, 60 Complex conjugate signal generation means 52, 61 Multiplication means 53, 62 Accumulation means 92, 94 Delay means 93, 95 Complex Amplitude correction means 96 Maximum local autocorrelation search means 97 Delay time calculation means 98 Complex amplitude coefficient calculation means 100, 101, 102, 103 Diversity synthesis means

Claims (10)

[Claims] 1. A plurality of antennas arranged apart from each other for capturing an OFDM-modulated signal, and a plurality of receptions respectively connected to the plurality of antennas and processing a supplied signal into a baseband signal. Means, connected to each output side of the plurality of receiving means, for removing signal components delayed from the output signal by more than the guard interval time of the OFDM modulated signal, and the plurality of delay equalizers Diversity combining means for combining each output signal of the means, and OFDM demodulation means for removing a guard interval signal inserted at the time of modulation from the output signal of the diversity combining means, extracting an effective symbol signal, and demodulating the OFDM signal. An OFDM receiver characterized by the above-mentioned. 2. An autocorrelation detecting means for detecting an autocorrelation of each output signal of the plurality of receiving means is connected to an output side of the plurality of receiving means, and the delay equalizing means comprises an autocorrelation detecting means. 2. The OFDM receiving apparatus according to claim 1, wherein a signal component of each OFDM modulated signal that is delayed by a guard interval time or more is removed based on the detection result. 3. The delay equalization means, of the autocorrelation values detected by each of the autocorrelation detection means, a delay time from the maximum autocorrelation value of the maximum autocorrelation value other than the maximum autocorrelation value; 3. The OFDM receiving apparatus according to claim 2, further comprising a plurality of feedback units for performing negative feedback on an output signal of the delay equalizing unit based on a complex amplitude coefficient calculated from the maximum autocorrelation value. 4. An effective symbol time delay means for outputting a delay signal obtained by delaying a signal supplied to the autocorrelation detection means by an effective symbol time, and an autocorrelation detection means for supplying the autocorrelation detection means. Complex conjugate signal generating means for generating and outputting a complex conjugate signal from the signal, multiplying means for multiplying the delayed signal by the complex conjugate signal, and accumulating the multiplication result of the multiplying means for a predetermined time The OFDM receiving apparatus according to claim 2, further comprising: 5. A first cross-correlation detecting means for detecting a cross-correlation between output signals of the plurality of receiving means is connected to an output side of the plurality of receiving means, wherein the diversity combining means comprises a signal combining means; The first
Wherein the signal synthesizing means corrects and synthesizes each output signal of the delay equalizing means to have the same phase based on the detection result of the first cross-correlation detecting means. The OFDM receiver according to claim 1, wherein: 6. A second cross-correlation detecting means for detecting a cross-correlation between respective output signals of the delay equalizing means is connected to each output side of the delay equalizing means; Correction means for synthesizing each output signal of the delay equalization means to have the same phase based on the detection result of the second cross-correlation detection means. 2. The OFDM receiving apparatus according to claim 1, wherein the signal is combined by performing the following. 7. The first cross-correlation detecting means or the second cross-correlation detecting means comprises: a signal supplied to the first cross-correlation detecting means or the second cross-correlation detecting means. Complex conjugate signal generation means for generating and outputting a complex conjugate signal from one signal; multiplication means for multiplying the complex conjugate signal by another of the two signals to be compared; 7. An OFDM receiving apparatus according to claim 5, further comprising: accumulating means for accumulating the multiplication result of for a predetermined time. 8. An autocorrelation detecting means for detecting an autocorrelation of each output signal of said plurality of receiving means is connected to an output side of said plurality of receiving means, and said delay equalizing means is connected to said autocorrelation detecting means. Based on the detection result, the signal components delayed by the guard interval time or more of the OFDM modulated signal are removed, and the signal synthesizing unit outputs the detection result of the autocorrelation detection unit and the detection result of the first cross-correlation detection unit. 6. The OFDM receiving apparatus according to claim 5, wherein the output signals of the plurality of delay equalizers are corrected based on a predetermined amplitude and the same phase, and then combined and output. 9. An autocorrelation detecting means for detecting an autocorrelation of each output signal of said plurality of receiving means is connected to an output side of said plurality of receiving means, and said delay equalizing means is connected to said autocorrelation detecting means. Based on the detection result, the signal components delayed by the guard interval time or more of the OFDM modulated signal are removed, and the signal synthesizing unit sets the detection result of the autocorrelation detection unit and the detection result of the second cross correlation detection unit as 7. The OFDM receiving apparatus according to claim 6, wherein the output signals of the plurality of delay equalizers are corrected based on a predetermined amplitude and the same phase, and then combined and output. 10. The OFDM demodulation means outputs an output of the diversity combining means based on a point in time when a maximum autocorrelation value indicating a maximum value among autocorrelations detected by each of the autocorrelation detection means is detected. 10. The OFDM receiver according to claim 2, wherein a guard interval signal is removed from the signal to extract an effective symbol.