JP4972588B2 - Radio receiver and its frame synchronization detection device - Google Patents

Description

  The present invention relates to a frame synchronization method for detecting the polarity of a preamble signal in a transmission packet and determining the head of a frame in a wireless receiver in a wireless system that transmits data while hopping frequencies in a plurality of transmission bands during transmission.

  In a conventional radio system, there is a radio transmission apparatus using an OFDM (Orthogonal Frequency Division Multiplexing) scheme as a transmission scheme.

  In the MultiBand OFDM (MB-OFDM) system, which is being standardized for WPAN (Wireless Personal Network) applications, OFDM hopping with a bandwidth of 528 MHz is performed in the order determined in the three frequency bands. And performs transmission using broadband.

  In general, a receiver of a wireless system detects the polarity of a preamble signal added to the head of a packet in order to determine the head of the received data (frame head) in the packet, thereby synchronizing the frame within the packet. It is carried out.

  In the MB-OFDM scheme, 24 known symbols are added as preamble signals for this synchronization, and a signal in which the polarity of the symbol in this signal interval is periodically inverted is added. The polarity pattern is determined corresponding to the hopping pattern (see FIG. 4). In this case, only a plurality of specific symbols out of the 24 symbols have a negative polarity, and the determination of the head of the frame is performed using this negative polarity symbol.

  Here, in the MB-OFDM system, since OFDM symbols are transmitted by frequency hopping, the OFDM symbols are received in synchronization with the frequency hopping, and the correlation between the received OFDM symbols and the preamble pattern is obtained. The head of the frame is detected based on the above.

  However, since frequency hopping is performed as described above, the phase change amount added to each received OFDM symbol differs depending on the transmission path, so the polarity of the correlation peak of the correlation output is different for each received OFDM symbol. It will be different. For this reason, if the result of the complex multiplication operation with the signal obtained by delaying the correlation signal includes an operation result between signals in different frequency bands, a component of polarity change due to phase rotation is included, and the polarity of the preamble signal It becomes difficult to detect only the inversion component.

  For this reason, conventionally, the detection of the polarity of the preamble signal is generally performed by calculating a cross-correlation between the received OFDM symbol and a known preamble pattern by a correlator, and performing complex multiplication of the correlation output and the delayed signal of the correlation signal. This is done by detecting the polarity change point based on the calculation result (see, for example, Patent Document 1).

  The delay of the delay signal is for performing complex multiplication between the same bands. Thereby, even if the polarity of the correlation peak of the correlation output of an arbitrary band becomes negative with respect to the positive polarity symbol due to the polarity change due to the phase rotation (negative polarity due to the phase difference between the bands; Polarity reversal due to phase rotation between bands), and the negative polarity is complex-multiplied to obtain positive polarity, so that the above problem can be solved.

Note that “detecting a polarity change point” means detecting a portion where the complex multiplication output has a negative polarity. The complex multiplication output has a negative polarity when the correlation signal to be complex-multiplied and its delayed signal are in the case where one is positive and the other is negative, that is, the polarity changes from positive to negative (or vice versa). Is the case. The head of the frame is detected based on the detected polarity change point.
JP 2006-197375 A

  However, in the prior art of Patent Document 1, in order to detect the polarity change point of the preamble pattern, the input signal and the input signal are delayed by a delay circuit using a shift register in accordance with the TFC preamble pattern. Thus, the correlation output is detected using two correlators, and the polarity of the preamble pattern is detected by complex multiplication of each correlation output. As described above, the method of Patent Document 1 requires a plurality of correlators, and further simplification of the circuit is desired.

  Further, in the conventional method such as Patent Document 1, it is not possible to completely eliminate the influence of the polarity change (polarity inversion due to the phase difference between the bands) due to the phase rotation due to the transmission band. In other words, this effect cannot be completely removed for TFCs 3 and 4, and erroneous detection of the head of the frame cannot be prevented.

  An object of the present invention is to eliminate the influence of polarity change due to phase rotation by a transmission band with a simpler circuit configuration in a radio receiver of a frequency hopping method for OFDM symbols such as the MB-OFDM method, and to determine the polarity of the preamble. By making it possible to detect only the change component, it is possible to prevent erroneous detection of the beginning of the frame. Further, by removing the influence of the TFCs 3 and 4, it is possible to prevent erroneous detection of the beginning of the frame. Etc. is to provide.

  The first radio receiver of the present invention receives OFDM symbols frequency-hopped in a plurality of frequency bands, and detects frame heads from the hopping synchronization apparatus and the polarity of each symbol of the preamble part in the received packet. A radio receiver having a detection device, wherein the frame synchronization detection device calculates a cross-correlation between each symbol of the preamble part and a preamble pattern and outputs a correlation signal; and A delay amount variable delay means for outputting a delay signal obtained by delaying the correlation signal by a delay amount corresponding to the TFC detected by the hopping synchronizer, the correlation signal and the delay signal And a complex multiplication means for computing complex multiplications, and detecting a polarity change point based on a computation output by the complex multiplication means To detect the beginning of the frame in the.

  In the radio receiver having the above-described configuration, first, the cross-correlation is calculated, and then this correlation signal is delayed by a delay amount corresponding to the TFC at that time by a delay unit having a variable delay amount. Therefore, the circuit configuration can be simplified as compared with the prior art. Of course, only the polarity change component of the preamble can be detected by removing the influence of the polarity change due to the phase rotation due to the transmission band. However, in the above configuration, the influence of the polarity change due to the phase rotation due to the transmission band (polarity inversion due to the phase difference between the bands) cannot be completely removed for the TFCs 3 and 4, but by the following configuration of the second radio receiver It is possible.

  That is, the second radio receiver of the present invention receives OFDM symbols frequency-hopped into a plurality of frequency bands, and detects the head of the frame from the hopping synchronizer and the polarity of each symbol in the preamble portion of the received packet. A radio receiver having a frame synchronization detection device, wherein the frame synchronization detection device calculates a cross-correlation between each symbol of the preamble part and a preamble pattern and outputs a correlation signal, and the correlation calculation First delay amount variable delay means for inputting a correlation signal from the means and outputting a first delay signal obtained by delaying the correlation signal by a delay amount corresponding to the TFC detected by the hopping synchronizer; Complex multiplication means for calculating complex multiplication of the correlation signal and the first delayed signal, and the hopping synchronizer currently selected A second delay amount variable that outputs a second delay signal obtained by delaying the band identification signal by a delay amount corresponding to the TFC detected by the hopping synchronization apparatus. The delay unit, the band identification signal and the second delay signal are input, and when the bands are the same, the band determination unit that outputs a coincidence detection signal, and the calculation output by the complex multiplication unit are input. When the coincidence detection signal is output, the signal processing unit has selector means for passing the calculation output, and detects the head of the frame by detecting the polarity change point based on the output of the selector means.

  In the second radio receiver having the above-described configuration, a detection signal obtained by complex multiplication is provided by further providing second delay amount variable delay means, band determination means, and selector means to the first radio receiver. On the other hand, the complex multiplication operation result for signals with different transmission frequency bands at the time of frequency hopping of the correlation signal can be deselected, and only the complex multiplication operation result of signals in the same frequency band can be output, and the polarity change point And the head of the frame is not erroneously detected.

  Further, the delay amount is 3 symbols when the detected TFC is TFC1 or TFC2, and 1 symbol when the detected TFC is any one of TFC3 to TFC7. That is, the delay amount of the correlation signal is set so as to include a signal component in which the transmission frequency at the time of frequency hopping of the two signals subjected to complex multiplication is the same frequency.

  According to the wireless receiver or the like of the present invention, in a wireless receiver using a frequency hopping method for OFDM symbols such as the MB-OFDM method, the influence of polarity change due to phase rotation due to a transmission band can be eliminated with a simpler circuit configuration. Thus, erroneous detection at the beginning of the frame can be prevented. Further, by removing the influence of TFCs 3 and 4 as well, erroneous detection at the beginning of the frame can be prevented.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the following description, an MB-OFDM wireless system is taken as an example, but the present invention is not limited to this example.

  FIG. 1 is a block diagram showing the configuration of the receiving circuit of the wireless device of this example.

  The receiving circuit shown in the figure detects the top of the frame by detecting the “polarity changing point”.

  In the illustrated configuration, a received signal (OFDM symbol) received from the receiving antenna 1 includes an LNA (Low Noise Amp) 2, a down converter 3, an LPF (Low Pass Filter) 4, an AGC (Automatic Gain Control) 5, and A / The signal is input to the FFT calculation unit 13 via the D converter 6. The output of the A / D converter 6 is also input to the hopping synchronization circuit 11 and the frame synchronization detection circuit 12.

  The hopping synchronization circuit 11, the frame synchronization detection circuit 12, and the FFT calculation unit 13 constitute a demodulation unit 10, and a demodulated signal is output from the FFT calculation unit 13 by these configurations.

  Of the above-described configurations, the configuration other than the frame synchronization detection circuit 12 may be substantially the same as the conventional one, and will not be particularly described. However, the hopping synchronization circuit 11 will be briefly described below because the processing result is used.

  That is, the down-converter 3 receives a signal having a predetermined frequency output from the Lo oscillator 7 (a signal having a reception frequency of the receiver), thereby quadrature-detecting the received signal and outputting a complex baseband signal. The frequency (band) of the signal output from the Lo oscillator 7 is controlled by the hopping synchronization circuit 11, and particularly after detecting the TFC used on the transmission side, the band is switched and controlled in accordance with the hopping pattern of the TFC.

  That is, as is well known, the hopping synchronization circuit 11 detects the hopping pattern (any one of TFC1 to TFC7 described later) used on the transmission side based on the output of the A / D converter 6, By outputting the illustrated control signal b (for example, band ID described later) to the Lo oscillator 7 according to the TFC detection result, the frequency of the signal output from the Lo oscillator 7 is synchronized with the detected hopping pattern. To switch.

  In the hopping synchronization circuit 11 of this example, the illustrated TFC detection signal a (a TFC number to be described later of the detected TFC or the like) indicating the TFC detection result is further output to the frame synchronization detection circuit 12.

  Further, in the case of the configuration of FIG. 8 to be described later in this example, the control signal b (such as the band ID of the band currently selected by the hopping synchronization circuit 11) is also output to the frame synchronization detection circuit 12. .

  The operation of the frame synchronization detection circuit 12 to which these signals a and b are input will be described later with reference to FIGS.

  Here, in the MB-OFDM system, three transmission frequency bands (bands) identified by band ID = '1' to '3' are used, and as shown in FIG. (Time Frequency Code), and in the transmitting side radio device, the above three transmission frequency bands (bands) are represented by band ID patterns associated with any of the illustrated TFC numbers (TFC1 to TFC7). Transmit while switching.

  Hereinafter, the frequency band corresponding to band ID = “1” is referred to as band 1, and similarly, the frequency bands corresponding to band ID = “2” and “3” are referred to as band 2 and band 3, respectively.

  The period (hopping period) of each frequency hopping pattern shown in FIG. 2 is 6 symbols of OFDM symbols. Of the seven patterns shown, TFC1 and TFC2 are frequency hopping patterns every symbol, and TFC3 and TFC4 are frequency hopping every two symbols. TFC5 to TFC7 are patterns that do not perform frequency hopping (fixed to any of band 1 to band 3).

  On the receiver side, the hopping synchronization circuit 11 detects the hopping pattern (TFC) of the transmitted OFDM symbol for each OFDM symbol of the packet that is transmitted by frequency hopping in any of the above patterns, After the detection, the OFDM symbol to be hopped is received by switching and controlling the reception frequency of the receiver (the frequency of the signal output from the Lo oscillator 7) in synchronization with the hopping pattern.

  After establishing the hopping synchronization, the frame synchronization detection circuit 12 for detecting the frame start of the packet is used to detect the start of the frame based on the polarity of the received preamble signal. Note that a packet in OFDM has a configuration in which the preamble signal is added before a frame, and the frame includes a header portion and a data portion.

  FIG. 3 shows a configuration example of the frame synchronization detection circuit 12.

  The frame synchronization detection circuit 12 includes a correlation calculation unit 21 and a frame detection calculation unit 20. In addition, a known preamble pattern is stored in the preamble pattern storage unit 25 in advance. The frame detection calculation unit 20 includes a symbol delay circuit 22, a complex multiplier 23, and a threshold determination unit 24. Based on the TFC detection signal a, a preamble pattern corresponding to the detected TFC is input to the correlation calculation unit 21.

  The determination of the polarity change point of the preamble signal by the frame synchronization detection circuit 12 having the above-described configuration is performed by first calculating the cross-correlation between the received symbol and the preamble pattern by the correlation calculation unit 21, and the correlation output and the correlation output as symbol delay. A complex multiplier 23 calculates a complex multiplication with the delayed output delayed by the circuit 22 (however, taking a complex conjugate). The calculated output is input to the threshold value determination unit 24 and compared with a negative threshold value determined in advance by the threshold value determination unit 24 to detect the polarity change point.

  Note that the polarity change point has already been described, but, for example, means a portion where the frame detection signal shown in FIG. 5 (g), FIG. All negative outputs exceed the above negative threshold).

  The symbol delay circuit 22 is a delay circuit with a variable delay amount, and receives the TFC detection signal a, thereby delaying the correlation output by a delay amount corresponding to the detected TFC. This delay amount is for 3 symbols when the detected TFC is TFC1 or TFC2, and for 1 symbol when the detected TFC is any one of TFC3 to TFC7. That is, a delay is applied so that the correlation outputs of the same pass band are complex-multiplied.

  A configuration example of the symbol delay circuit 22 is not particularly illustrated, but includes, for example, a configuration in which two shift registers each delayed by one symbol by two symbols are connected in cascade, and includes a switch for inputting the output of each shift register, The switch may be configured to output any input in response to the TFC detection signal a. Of course, other configurations may be used.

  The cross-correlation calculation with the preamble pattern by the correlation calculation unit 21 and the complex multiplication by the complex multiplier 23 are existing techniques as disclosed in Patent Document 1 and the like.

  However, in the configuration of Patent Document 1, in order to detect the polarity change point in the preamble signal section, the input signal and the input signal are delayed by a delay circuit using a shift register in accordance with the detected TFC preamble pattern. The polarity of the preamble pattern is detected by detecting the correlation output of the signal using two correlation outputs and performing complex multiplication of each correlation output.

  On the other hand, in the configuration shown in FIG. 3, a correlation signal is first detected by one correlator (correlation calculation unit 21), and this is complex-multiplied with a delayed signal delayed by a delay amount corresponding to TFC. By doing so, the number of correlators can be reduced and the circuit can be simplified.

  Conventionally, regarding TFCs 3 and 4, it is not possible to prevent erroneous detection of the polarity change point due to the influence of the polarity change due to the phase difference between the bands, but in this example, it can be handled by the configuration of FIG. It is.

  Here, as described above, the correlation output for the frequency-hopped OFDM symbol differs in the amount of phase rotation applied in the transmission path depending on the frequency band that has passed, so the polarity (the polarity of the correlation output) is the band. Different for each. For example, the correlation output examples shown in FIG. 5C and FIG. 6C are examples on the assumption that there is no phase rotation due to the transmission path. On the other hand, for example, assuming that there is a phase difference of 180 ° between band 1 and band 2, as shown in FIG. 7 (c), the correlation output of the band 2 is the negative polarity due to the phase difference between the bands. (For a positive symbol). Even in such a case, if complex multiplication is performed between the same passbands (especially in this example, between bands 2), since negative × negative becomes positive, the polarity inversion component due to the phase difference between the bands can be removed. Therefore, there is no problem, but there are places where bands 3 and 4 are not the same pass band. For this reason, the configuration of FIG. 8 has been proposed as described above and will be described in detail later.

  This will be described in more detail below.

  First, in MB-OFDM, as shown in FIG. 4, the polarity of a preamble signal is defined corresponding to each TFC (each hopping pattern).

  As shown in the figure, for example, in the case of TFC1 and 2, only three symbols from the 22nd to the 24th out of 24 symbols are negative, and in the case of TFC3 and 4, the 20th, 22nd and 24th symbols. Only the three symbols are negative. The negative polarity state is a state in which all the codes are inverted with respect to the positive polarity code series.

  For this reason, in the case of TFC 1 and 2, by setting the delay amount to 3 symbols, the correlation output of the same pass band is complex-multiplied, and this is removed even if there is a polarity inversion component due to the phase difference between the bands. The polarity change point can be detected correctly.

  For example, FIG. 5 shows examples of input / output signals in the frame synchronization detection circuit 12 when TFC1 is taken as an example. In this example, the hopping synchronization circuit 11 performs reception band switching control in synchronization with the hopping pattern after detecting the TFC. In the frame synchronization detection process by the frame synchronization detection circuit 12, FIG. All symbols are received as shown in (b).

  First, as shown in FIG. 5A, the transmitter side has a pattern of band 1 → band 2 → band 3 → band 1 → band 2 as shown in FIG. The transmission is performed while switching the transmission frequency band (band) for each OFDM symbol. In the figure, PS means a positive polarity and -PS means a negative polarity OFDM symbol.

  Then, as shown in FIG. 5B, all symbols are input to the correlation calculation unit 21 as the received symbols. Since the hopping synchronization is established as described above, all the OFDM symbols are sequentially input to the correlation calculation unit 21 as illustrated.

  The “correlation output” shown in FIG. 5 (c) is an output of the correlation calculation unit 21, and when there is no influence of the phase rotation, as shown in FIG. Negative output for a negative OFDM symbol. Since TFC1 is taken as an example here, the “delay output” shown in FIG. 5 (e) is a signal obtained by delaying the “correlation output” of FIG. 5 (c) by three symbols by the symbol delay circuit 22. Become.

  5 (d), (f), and (g) show the pass bands of the “correlation output” and “delay output” and the “correlation output” and “delay output” (delay output is complex). A frame detection signal obtained after complex multiplication by the complex multiplier 23 is shown. As shown in the figure, by delaying by three symbols, it is possible to perform complex multiplication between outputs of the same pass band, and a normal frame detection signal is obtained as described above. That is, as shown in the figure, only when the polarity is inverted between the “correlation output” and the “delay output”, the complex multiplier 23 has a negative output, and the frame head of the packet is not erroneously detected. .

  Although FIG. 5 shows TFC1 as an example, the same applies to TFC2.

  Although not particularly illustrated, the demodulating unit 10 detects the frame head of the packet based on the frame detection signal and a predetermined reference. In the case of TFC1 to TFC4, the predetermined reference is that the position of the first polarity change point is used as the determination reference at the beginning of the frame when three negative outputs (polarity change points) in the frame detection signal are detected. .

  In practice, the threshold value determination unit 24 compares the frame detection signal (output of the complex multiplier 23) with a predetermined negative threshold value (for example, the detection threshold value shown in FIG. 9). Only the signal exceeding the threshold value is detected as the polarity change point. Here, it is assumed that all the negative outputs shown in the figure exceed the threshold value.

  On the other hand, in the case of TFC5 to TFC7, as shown in FIG. 4, there are many negative symbols, but the positive / negative of the frame detection signal by each symbol of symbol numbers 19 to 24 becomes a unique pattern. Therefore, the criterion is determined. That is, in the case of TFC5 to TFC7, since the symbols are delayed by one symbol, the symbol numbers are “19” and “20”, “20” and “21”, “21” and “22” “22” and “23”. As a result of complex multiplication by “23” and “24”, the positive / negative of the frame detection signal becomes negative, negative, negative, positive, positive. That is, a pattern in which three negative outputs are continued and then two positive outputs are continued. When such a pattern is detected, the position of the first negative output is used as a determination reference for the head of the frame.

  By doing so, there is no need for two adders as in Patent Document 1, so the circuit can be simplified from this point as well.

  For TFCs 5, 6, and 7, although not specifically shown, the polarity is correctly changed by complex multiplication of correlation outputs of the same passband by setting the delay amount to 1 symbol as in the case of TFCs 1 and 2 above. The point can be detected, and there is no possibility that the frame head of the packet is erroneously detected.

  On the other hand, regarding TFCs 3 and 4, even when the delay amount is one symbol, the polarity inversion component due to the phase difference between the bands cannot be completely removed in the case shown in FIG. 7 as described above.

  FIG. 6 shows examples of input / output signals in the frame synchronization detection circuit 12 when TFC3 is taken as an example. However, FIG. 6 shows a case where it is assumed that there is no phase rotation due to the transmission path in all bands. On the other hand, as already described, FIG. 7 shows an example when there is a polarity change due to phase rotation (polarity inversion due to a phase difference between bands).

  As shown in FIGS. 6 and 7, in TFCs 3 and 4, since transmission is performed in the same frequency band every 2 symbols between 6 symbols, in the multiplication operation with the signal obtained by delaying the correlation output by one symbol, The calculation results of different bands are also included. For example, the calculation results of different bands are also included, such as band 2 and band 1 next to band 1, band 3 and band 2 next to band 2, and the like.

  Nevertheless, when it is assumed that there is no phase rotation due to the transmission path, it is possible to correctly detect the polarity inversion portion of the preamble symbol as shown in FIG.

  However, when there is a polarity change due to phase rotation, as shown in FIG. 7G, a negative polarity output (incorrect polarity change point) other than polarity inversion by the preamble symbol is detected, and the head of the frame is erroneously detected. End up.

  That is, in the case of TFCs 3 and 4, the frame detection signal finally has five consecutive negative outputs as shown in FIG. 6 (g), and when the third negative output is detected according to the predetermined reference, The detected negative output position (“original detection position” shown in FIG. 7G) is the determination criterion for the head of the frame. However, when the frame detection signal shown in FIG. 7G is obtained, there is a negative output before the “original detection position” as shown in the figure, so the position of the first negative output shown in the figure is at the beginning of the frame. It becomes a determination criterion and erroneously detects the beginning of the frame of the packet.

  FIG. 8 is a configuration example of the frame synchronization detection circuit 12 for solving the above problem.

  As described in FIG. 1, the TFC detection signal a and the control signal b (such as the band ID of the band currently selected by the hopping synchronization circuit 11) are input to the frame synchronization detection circuit 12 of this example. .

  In the configuration shown in FIG. 8, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. That is, the configuration in which the correlation calculation unit 21 calculates the cross-correlation between the received symbol and the preamble pattern and outputs this correlation output to the frame detection calculation unit 31 is the same as in FIG. Further, the frame detection calculation unit 31 is different from the frame detection calculation unit 20 of FIG. 3 in that it does not include the threshold determination unit 24 (the threshold determination unit 24 is arranged at the subsequent stage of the selector 33 as illustrated). The rest is the same. That is, although not shown in particular, the frame detection calculation unit 31 includes a symbol delay circuit 22 and a complex multiplier 23, and calculates and outputs a complex multiplication of the correlation output and its delay output.

  The TFC detection signal a is input to the preamble pattern storage unit 25 and the symbol delay circuit 22 (not shown) in the frame detection calculation unit 31 as in FIG. Show.

  In the configuration of FIG. 8, a band determination device 32, a selector 33, and a delay circuit 34 are further provided. The selector 33 inputs the calculation output of the frame detection calculation unit 31 and passes the calculation output of the frame detection calculation unit 31 and inputs it to the threshold determination unit 24 only when the coincidence detection signal is output from the band determination device 32. Let Of course, when the coincidence detection signal is not input, the calculation output of the frame detection calculation unit 31 is not passed. That is, by switching the selector 33 based on the output from the band determination device 32, the negative output signal that is the source of the erroneous detection is not passed to the threshold determination unit 24 side, so that the frame head of the packet is erroneously detected. Prevent detection.

  The band determination device 32 receives the control signal b (current band ID or the like) and a delay signal b ′ obtained by delaying the control signal b by the delay circuit 34.

  The delay circuit 34 has the same configuration as the symbol delay circuit 22 of FIG. That is, the TFC detection signal a is input to the delay circuit 34, and as a result, the control signal b is delayed by a delay amount corresponding to the detected TFC as described with respect to the symbol delay circuit 22.

  The band determination device 32 determines whether or not the control signal b and the delay signal b ′ match (for example, whether or not these band IDs are the same). Output to. Thereby, the selector 33 passes only the calculation result of the same band.

  FIG. 9 shows a waveform example such as a frame detection signal when the configuration of FIG. 8 is used with respect to the example shown in FIG.

  The illustrated frame detection signal (after passing through the selector) is the output of the selector 33. The output of the frame detection calculation unit 31 may be considered to be the same as the frame detection signal shown in FIG. As can be seen by comparing FIGS. 7 (d), (f), and (g) and FIGS. 9 (d), (f), and (g), the correlation output pass band (control signal b) and the delayed output pass band (delay signal b) The negative output (complex multiplication output of the same band) of the frame detection signal when ') is the same passes through the selector 33, and is compared and detected with the detection threshold by the threshold determination unit 24.

  On the other hand, when the correlation output pass band (control signal b) and the delayed output pass band (delay signal b ') are different (in the example shown, "2" and "1", and "3" and "2"). Since the negative output of the detection signal does not pass through the selector 33, it is removed as shown in FIG. As described above, according to the configuration of FIG. 8, it is possible to remove the negative polarity signal due to the phase difference between the bands and detect only the polarity inversion component of the preamble signal. Therefore, these negative outputs are not detected by the threshold value determination unit 24 as polarity change points, and the frame head of the packet is not erroneously detected.

  As described above, in this method, the correlation signal is detected by one type of correlator, and the signal delayed by the delay amount corresponding to the preamble pattern by the delay circuit is complex-multiplied by the complex multiplier. Since the change point can be detected, the number of correlators can be reduced and the circuit can be simplified.

  Also for TFCs 3 and 4, the influence of polarity reversal due to the phase difference between the bands can be eliminated, and only the polarity change point due to the polarity change of the symbol can be detected, thereby preventing erroneous detection of the packet frame head. I can do it. In other words, when detecting frame synchronization, the result of complex multiplication of the correlation output between the received symbol and the preamble signal and the delayed signal is passed only for the calculation of the symbols in the same band, thereby detecting polarity inversion detection by phase rotation between the bands. It is possible to remove and detect only the polarity inversion of the preamble.

It is a block diagram of the configuration of the receiving circuit of the wireless device of this example. It is a figure which shows seven types of hopping patterns (TFC) in a MB-OFDM system. 2 is a configuration example of a frame synchronization detection circuit. It is a figure which shows prescription | regulation of the polarity of the preamble signal corresponding to each TFC. (A)-(g) is a figure which shows each input-output signal example in the frame-synchronization detection circuit at the time of taking TFC1 as an example. (A)-(g) is a figure which shows each input-output signal example in a frame synchronous detection circuit at the time of assuming that there is no phase rotation for TFC3 as an example. (A)-(g) is a figure which shows each input-output signal example in a frame synchronous detection circuit in case there exists phase rotation for TFC3 as an example. This is a configuration example of a frame synchronization detection circuit corresponding to a case where there is a phase rotation with respect to TFCs 3 and 4. (A)-(g) is a figure which shows each input-output signal example in the frame-synchronization detection circuit shown in FIG.

Explanation of symbols

1 Receiving antenna 2 LNA
3 Down converter 4 LPF
5 AGC
6 A / D converter 7 Lo oscillator 10 Demodulator 11 Hopping synchronization circuit 12 Frame synchronization detection circuit 13 FFT operation unit 20 Frame detection operation unit 21 Correlation operation unit 22 Symbol delay circuit 23 Complex multiplier 24 Threshold determination unit 25 Preamble pattern storage unit 31 Frame Detection Operation Unit 32 Band Determination Device 33 Selector 34 Delay Circuit

Claims (2)

A radio receiver that receives OFDM symbols frequency-hopped in a plurality of frequency bands, and has a frame synchronization detection device that detects a hopping synchronization device and a head of a frame from the polarity of each symbol of a preamble portion in a received packet,
The frame synchronization detection device includes:
Correlation calculating means for calculating a cross-correlation between each symbol of the preamble part and a preamble pattern and outputting a correlation signal;
A first delay amount variable delay for inputting a correlation signal from the correlation calculation means and outputting a first delay signal obtained by delaying the correlation signal by a delay amount corresponding to the TFC detected by the hopping synchronization device Means,
Complex multiplication means for calculating a complex multiplication of the correlation signal and the first delayed signal;
A second delay signal obtained by inputting a band identification signal indicating a band currently selected by the hopping synchronization apparatus and delaying the band identification signal by a delay amount corresponding to the TFC detected by the hopping synchronization apparatus Second delay amount variable delay means for outputting
Band determination means for inputting the band identification signal and the second delay signal and outputting a coincidence detection signal when the bands are the same;
A selector unit that inputs an arithmetic output from the complex multiplier and passes the arithmetic output when the coincidence detection signal is output;
A radio receiver characterized in that the head of a frame is detected by detecting a polarity change point based on the output of the selector means. In a radio receiver that receives OFDM symbols frequency-hopped in a plurality of frequency bands, a frame synchronization detection device that detects the beginning of a frame from the polarity of each symbol of a preamble portion in a received packet,
Correlation calculating means for calculating a cross-correlation between each symbol of the preamble part and a preamble pattern and outputting a correlation signal;
First delay amount variable delay means for inputting a correlation signal from the correlation calculation means and outputting a first delay signal obtained by delaying the correlation signal by a delay amount corresponding to the detected TFC;
Complex multiplication means for calculating a complex multiplication of the correlation signal and the first delayed signal;
A second delay amount variable delay for inputting a band identification signal indicating the currently selected band and outputting a second delay signal obtained by delaying the band identification signal by a delay amount corresponding to the detected TFC Means,
Band determination means for inputting the band identification signal and the second delay signal and outputting a coincidence detection signal when the bands are the same;
A selector unit that inputs an arithmetic output from the complex multiplier and passes the arithmetic output when the coincidence detection signal is output;
A frame synchronization detection apparatus for detecting the head of a frame by detecting a polarity change point based on an output of the selector means.