JP2006303718A - Receiving apparatus and demodulation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a single chip and to make it inexpensive without using an expensive and difficult band-pass filter (SAW filter).
SOLUTION: Orthogonal demodulation sections 104 and 105 convert received signals into baseband signals of I and Q signals. Local signal oscillating units 106 and 107 input local signals to quadrature demodulation units 104 and 105. The LPFs 108, 109, 110, and 111 allow only the low frequency band to pass through by limiting the band of the I and Q signals. The AGC units 112, 113, 114, and 115 convert the signal levels of the I and Q signals to optimum levels for the AD conversion units 120, 121, 124, and 125 in the subsequent stage. The signal distributor 119 divides the received signal into different bands. The AD conversion units 120, 121, 124, and 125 convert the input analog signals into digital signals.
[Selection] Figure 1

Description

  The present invention relates to a receiving apparatus and a demodulation method, and in particular, when a wideband signal such as an OFDM (Orthogonal Frequency Division Multiplexing) signal is received, a transmission band is divided into a plurality of bands, and each band-divided signal is demodulated. The present invention relates to a receiving apparatus and a demodulation method.

  An OFDM signal system is known as a multicarrier transmission system. The OFDM signal system is a frequency-division multiplexed digital modulation system that transmits digital information using a plurality of orthogonal carriers, is strong against multipath, is less likely to interfere with other transmission systems, and is less susceptible to interference. It has characteristics such as relatively high frequency utilization efficiency.

  In the OFDM system, an IFFT circuit that performs inverse fast Fourier transform (hereinafter referred to as “IFFT”) is used on the transmission side, and an FFT circuit that performs fast Fourier transform (hereinafter referred to as “FFT”) on the reception side. Perform signal processing. In recent years, in order to realize large-capacity transmission, the OFDM scheme has adopted a channel configuration using a large number of subcarriers. For this reason, the signal processing unit requires high-speed processing.

  A technique using parallel processing has been proposed as a method for reducing the processing speed. In general, the parallel processing is a method of performing processing in parallel with respect to the time axis by time-sharing portions requiring high-speed operation, assigning hardware to each portion, and increasing the hardware configuration. In the OFDM receiver, the concept of parallel processing is used not for time division but for frequency band division. That is, in the OFDM receiver, the entire frequency band to be handled is divided into a plurality of frequency bands, hardware is allocated to each frequency band, and the hardware configuration is increased to perform processing in parallel with the frequency axis. As a result, a portion requiring high-speed operation is realized at a low-speed hardware processing speed (for example, Patent Document 1 and Patent Document 2).

  FIG. 9 is a block diagram illustrating a configuration of a parallel reception apparatus described in Patent Document 1. In FIG. Note that FIG. 9 shows a configuration in which the bandwidth is divided into four.

  9 includes an antenna 901, a front-end circuit 902 including a local oscillator, a frequency converter, and an automatic gain control (hereinafter referred to as “AGC”) unit; In order to realize parallel processing, BPF 903, BPF 904, BPF 905, and BPF 906 for dividing a frequency band into four parts and a local oscillator 907, a local oscillator 908, and a local oscillator that oscillate a local frequency signal corresponding to each series 909, a local oscillator 910, frequency converters 911, 912, 913, 914 that multiply the band-limited signal in each sequence by a local frequency signal in each sequence and convert it to the second IF frequency band, and for each sequence Analog / digital converter, quadrature demodulator, and FF for OFDM demodulation of second IF frequency band signal OFDM demodulator units 915, 916, 917, and 918, and parallel signals output from OFDM demodulator units 915, 916, 917, and 918 are converted into serial signals and output as demodulated data. S portion 919.

  BPF 903, BPF 904, BPF 905, and BPF 906 are band-pass filters each having a different center frequency and a bandwidth that is ¼ of the entire bandwidth handled by the OFDM receiver (here, BW). is there. For example, the center frequency of BPF 903 is fa, the center frequency of BPF 904 is fb, the center frequency of BPF 905 is fc, the center frequency of BPF 906 is fd, and the bandwidth of each filter is BW / 4.

  Also, assuming that the second intermediate frequency after the conversion by the frequency conversion unit 911 is f2, the oscillation frequencies of the local oscillator 907, the local oscillator 908, the local oscillator 909, and the local oscillator 910 correspond to the center frequency of each series of BPF. And fa-f2, fb-f2, fc-f2, and fd-f2, respectively.

  Next, the operation of the above-described OFDM receiver will be described with reference to FIGS. FIG. 10 is a diagram showing the frequency spectrum of the output signal from each BPF of the OFDM receiver, that is, BPF903, BPF904, BPF905, and BPF906. In FIG. 10, the horizontal axis represents frequency and the vertical axis represents power.

  First, a high-frequency RF signal is input from the antenna 901, converted into a first IF frequency band f1 that is an intermediate frequency of a constant power level by processing of the front end circuit 902, and a signal with a bandwidth BW is converted into four bands. And distributed output signals a1 to a4 are output to each series.

  In the first series, the distribution output signal a1 is BPF903, the first frequency fa is the center frequency, the band is limited to the bandwidth BW / 4, and the signal having the frequency characteristics as shown in FIG. Is output. Further, in the second series, the distribution output signal a2 is a BPF 904, the second frequency fb is set as the center frequency, the band is limited to the bandwidth BW / 4, and the signal having the frequency characteristics as shown in FIG. Is output. Similarly, in the third and fourth series, the distribution output signals a3 and a4 are BPF905 and BPF906, respectively, and the third frequency fc and the fourth frequency fd are the center frequencies, and the bandwidth is limited to the bandwidth BW / 4. A signal having a frequency characteristic as shown in FIGS. 10C and 10D is output.

  In each series, the output signal from each BPF is multiplied with the local frequency signal from the corresponding local oscillator 907, 908, 909, 910 in each frequency converter 911, 912, 913, 914 to lower the frequency. The signal is converted to the second IF frequency band f2 and output to each of the OFDM demodulation units 915, 916, 917, and 918.

  In each OFDM demodulator 915, 916, 917, 918, the input signal is sampled with a certain period of high speed, converted into a digital signal, quadrature demodulated, and in-phase component and quadrature component (I, Q) baseband signals Is generated. Then, serial-parallel conversion is performed on each of the I and Q signals, and each parallel signal is subjected to discrete Fourier transform, and then decoding is performed using each I and Q signal at each timing, and decoded data is output in parallel. The parallel decoded data output from the OFDM demodulation units 915, 916, 917, and 918 are parallel-serial converted by the P / S unit 919 and output as demodulated data.

  In the receiving apparatus shown in FIG. 9, although the hardware configuration is increased by dividing the demodulation part into four circuits, the operation speed of each part can be reduced to about 1/4. .

  FIG. 11 is a block diagram illustrating a configuration of the receiving apparatus disclosed in Patent Document 2. FIG. 11 implements a parallel system using one type of BPF. Note that components similar to those in FIG. 9 are described with the same reference numerals.

  The OFDM receiver shown in FIG. 11 includes an antenna 901, a front end circuit 902, frequency converters 911, 912, 913, and 914 for each series, OFDM demodulators 915, 916, 917, and 918, and a P / S unit. 919, local oscillators 1105, 1106, 1107, 1108, BPFs 1101, 1102, 1103, 1104, and an in-phase distributor 1109, which are characteristic parts of the OFDM receiver.

  The BPFs 1101, 1102, 1103, and 1104, for example, similarly to the BPF 903 in FIG. 9, when the first frequency fa is the central frequency and the bandwidth handled by the entire apparatus is BW, the bandwidth is limited by the bandwidth BW / 4. It is a band pass filter which performs. The in-phase distributor 1109 is a distributor that distributes and outputs the input signal in four phases that are in-phase and the number of band divisions.

  FIG. 12 is a diagram illustrating the relationship between the reception bandwidth and the output signal from the BPF in the receiving apparatus of Patent Document 2, in which the horizontal axis represents frequency and the vertical axis represents power.

  The local oscillator 1105 is an oscillator that outputs a local signal such that the distributed output signal from the in-phase distributor 1109 is input to the BPF 1101 having the bandwidth BW / 4 as shown in FIG. Similarly, the local oscillator 1106 has the input shown in FIG. 12B, the local oscillator 1107 has the input shown in FIG. 12C, and the local oscillator 1108 has the input shown in FIG. It operates so as to be the input shown in (d).

The signals band-divided by the BPFs 1101, 1102, 1103, and 1104 are input to the OFDM demodulation units 915, 916, 917, and 918. In general, since it is difficult to realize a band limiting filter in a low frequency band, in the configuration of FIG. 11, analog / digital conversion is performed using undersampling. Patent Document 2 also describes a configuration in which a frequency conversion unit is placed on the output side of the BPFs 1101, 1102, 1103, and 1104. The subsequent operation after the OFDM demodulator is the same as that of the OFDM receiver in FIG.
JP 2000-49744 A JP 2002-290367 A

  However, in the conventional apparatus, since a plurality of BPFs such as SAW are used as the band limiting filter, there are problems that the cost is increased and the size cannot be reduced (one chip). In addition, the parallel receiving apparatus shown in FIG. 9 has a problem that the cost increases because BPFs having different characteristics are used. In addition, the receiving apparatus shown in FIG. 11 has a problem that the cost increases because it is necessary to use an analog / digital conversion section having a wideband characteristic capable of undersampling. In general, in the undersampling method, since it is necessary to perform filtering for all bands where aliasing occurs, there is a problem that it is necessary to use an expensive BPF with good suppression characteristics over a wide band.

  In the conventional apparatus, since the AGC unit is placed before the band limiting unit (BPF), in a system having a plurality of channels, if the signal level of the other channel is higher than the signal level of the desired channel due to the propagation environment, the AGC unit Therefore, there is a problem that it is necessary to give the AGC portion a large distortion resistance characteristic, which increases power consumption and costs.

  In the conventional apparatus, the sampling frequency of the analog / digital (hereinafter referred to as “AD”) conversion unit and the operation clock of the digital circuit are used for sampling the IF frequency and performing digital quadrature demodulation processing and FFT processing. There is a problem that it needs to be fast. In general, when digital quadrature demodulation processing is performed, in order to configure the digital quadrature demodulation processing as a switch circuit having a small circuit scale, the sampling clock of the A / D converter is 4 * n times the signal center frequency ( This is because n is an integer. In addition, in a composite receiver composed of an OFDM signal receiver and a signal receiver of another system having a narrower band than the OFDM signal, it is necessary to provide a demodulator for OFDM and a demodulator of another system, so the circuit scale There is a problem that becomes larger. Also, in a wireless receiver that can use both a broadband OFDM signal system and another system with a narrow band, when sharing a wireless part, generally, a high-speed device and a low-speed device are operated at the same speed in a digital circuit. In such a case, the power consumption of the high-speed device is larger. Therefore, even when a narrow band system is used, the use of a device such as a wideband OFDM AD converter becomes inefficient in terms of power consumption and increases the cost. There is. Also in this case, there is a problem that the bandwidth limiter cannot be shared.

  The present invention has been made in view of the above points, and can be made into one chip and can be made inexpensive without using an expensive and difficult-to-down band-pass filter (SAW filter). An object is to provide a receiving apparatus and a demodulation method.

  The receiving apparatus of the present invention includes a quadrature demodulating unit that generates an I signal and a Q signal by performing orthogonal demodulation processing on a received signal in parallel for each predetermined band, and reduces the I signal and the Q signal in parallel for each band. Baseband signal processing means for controlling only the gain of the I signal and the Q signal in parallel for each band, and the gain is controlled by the baseband signal processing means and the baseband signal processing. And a demodulating means for demodulating the I signal and the Q signal passed through the means in parallel for each band.

  In the demodulation method of the present invention, a received signal is orthogonally demodulated in parallel for each predetermined band to generate an I signal and a Q signal, and the I signal and the Q signal are low-passed in parallel for each band. Passing only a low band by passing through a filter, and controlling the gain of the I signal and the Q signal in parallel for each band, and controlling the gain and passing through the low pass filter And demodulating the I signal and the Q signal in parallel for each band.

  According to the present invention, it is possible to make a single chip and to reduce the cost without using an expensive and difficult-to-size band-pass filter (SAW filter).

  The receiving apparatus of the present invention includes a plurality of quadrature demodulating means, and by inputting different local signals to each quadrature demodulating means, signal band division is performed by a low-pass filter means (hereinafter referred to as “LPF”). The configuration is to be performed. By adopting such a band division demodulation method and an analog quadrature demodulation configuration, the cut-off frequency of the LPF can be lowered, and realization as an active filter incorporated in an LSI is facilitated. As a result, even in a system that handles a wideband signal, an inexpensive digital circuit and an analog unit made into one chip can be used, and an inexpensive and small-sized wideband receiving apparatus can be realized.

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

(Embodiment 1)
1 is a block diagram showing a configuration of receiving apparatus 100 according to Embodiment 1 of the present invention, and FIG. 2 is a diagram showing a spectrum of each part of receiving apparatus 100. Although FIG. 1 shows a case where there are two orthogonal demodulation units, the present invention is not limited to this, and the number of orthogonal demodulation units can be any number.

  The receiving apparatus 100 includes an antenna 101, an antenna duplexer 102 that shares the antenna 101 with a transmission system (not shown), a low noise amplifier 103 that amplifies the received signal with low noise, and a signal that divides the received signal into different bands. Distributing unit 119, two signal demodulating units 150 and 151, and a P / S converting unit 118 that converts parallel signals output from the plurality of signal demodulating units 150 and 151 into serial signals, synthesizes them, and outputs them as demodulated data. It consists of and.

  The signal demodulator 150 includes an orthogonal demodulator 104 that converts an input received signal into a baseband signal of I and Q signals, a local signal oscillator 106 that inputs a local signal to the quadrature demodulator 104, and I and Q signals. LPFs 108 and 109, which are baseband signal processing means for band limiting, and AGC units 112 and 113, which are baseband signal processing means for converting the signal level of the I and Q signals to an optimum level for the AD conversion unit at the subsequent stage, , An OFDM signal digital processing unit 116 which is a demodulating means for OFDM demodulating the input I and Q signals.

  Similarly, the signal demodulator 151 includes an orthogonal demodulator 105, a local signal oscillator 107, LPFs 110 and 111 as baseband signal processing means, AGC sections 114 and 115 as baseband signal processing means, and an OFDM signal. It comprises a digital processing unit 117.

  The OFDM signal digital processing unit 116 converts the input analog signal into a digital signal, AD conversion units 120 and 121, an FFT unit 122 that performs FFT processing, and a signal that can be synthesized by the P / S conversion unit 118. A decoding unit 123 is included.

  Similarly, the OFDM signal digital processing unit 117 can be synthesized by the AD conversion units 124 and 125 that convert the input analog signals into digital signals, the FFT unit 126 that performs fast Fourier transform processing, and the P / S conversion unit 118. A decoding unit 127 for converting the signal into a simple signal.

  Next, the band dividing method of the receiving apparatus 100 in FIG. 1 will be described with reference to FIG.

  2A to 2E are diagrams showing spectra of the A, B, C, D, and E portions of the receiving apparatus 100 of FIG. 1, respectively, with the horizontal axis indicating frequency and the vertical axis indicating power. Yes. 2A to 2E, the broken line indicates the filter characteristics.

  The spectrum of the signal received by the antenna 101 is shown in FIG. The received signal shown in FIG. 2A is a signal having a center frequency fc and a bandwidth BW. The received signal is filtered by the antenna duplexer 102, amplified by the low noise amplifier 103, distributed by the signal distribution unit 119, and input to the signal demodulation unit 150 and the signal demodulation unit 151.

  The signal demodulation units 150 and 151 perform OFDM demodulation on a part of the received signal. For example, the signal demodulator 150 operates to OFDM-demodulate the signal dw having the center frequency fc_dw and the bandwidth BW / 2 shown in FIG. The local signal oscillating unit 106 inputs a signal having a frequency fc_dw to the quadrature demodulating unit 104. Therefore, the reception signal input from the signal distribution unit 119 is converted into the I and Q signals having the spectrum shown in FIG.

  The converted I and Q signals are band-limited by the LPFs 108 and 109, resulting in the spectrum shown in FIG. The levels of the I and Q signals are optimized by the AGC units 112 and 113, and subjected to OFDM demodulation processing by the OFDM signal digital processing unit 116.

  Similarly, the signal demodulator 151 performs OFDM demodulation on the signal up having the center frequency fc_up and the bandwidth BW / 2 shown in FIG. The local signal oscillator 107 inputs a signal having a frequency fc_up to the quadrature demodulator 105. The reception signal input via the signal distribution unit 119 is converted by the orthogonal demodulation unit 105 into I and Q signals having the spectrum shown in FIG.

  The converted I and Q signals are band-limited by the LPFs 110 and 111, resulting in the spectrum shown in FIG. The levels of the I and Q signals are optimized by the AGC units 114 and 115 and subjected to OFDM demodulation processing by the OFDM signal digital processing unit 117.

  The output signals of the signal demodulation units 150 and 151 are combined by the P / S conversion unit 118 and output demodulated data.

  Here, as shown in FIG. 2 (c), even if a part of the signal up is not sufficiently filtered, it can be suppressed by FFT processing by setting the frequency band of the subcarrier not using the signal up. Therefore, there is no deterioration in OFDM demodulation.

  As described above, according to the first embodiment, the local signal oscillating units 106 and 107 generate different local signals, and the orthogonal demodulating units 104 and 105 perform orthogonal demodulation on different signal bands. It is possible to extract the lower signal (signal dw) of the reception signal band-limited at 109 and extract the upper signal (signal up) of the reception signal band-limited by the LPFs 110 and 111. In this way, the band division (parallel) type radio receiver can be configured in a small size by using a configuration that does not use a BPF such as a SAW filter and limits the bandwidth with an LPF that can be implemented as an active filter built in an LSI. be able to.

  In addition, according to the first embodiment, a plurality of quadrature demodulation units are provided and signal band division is performed by a low-pass filter (LPF), and the entire receiver analog unit can be built in the LSI. It becomes. As a result, the receiver can be downsized. In addition, according to the first embodiment, the processing speed of the digital unit can be reduced by the band division method, so that the digital circuit can be made inexpensive, thereby providing a more compact and inexpensive wireless receiver. Further, according to the first embodiment, the quadrature demodulation process is performed in the analog circuit unit, so that the band to be input to the AD conversion unit may be a quarter of the signal band. Therefore, the cutoff frequency of the LPF And can be easily realized as an active filter incorporated in an LSI.

  In the signal demodulator 150, since the AGC units 112 and 113 are subsequent to the LPFs 108 and 109, even in a system having a plurality of channels, the AGC unit is not easily distorted by other channels, and the AGC unit has a large distortion resistance characteristic. Since it is not necessary to provide the receiver, an inexpensive and low power consumption receiver can be provided. Also, according to the first embodiment, high quality reception characteristics can be obtained by optimizing the gain amount of the AGC unit for each OFDM signal demodulating unit. Further, according to the first embodiment, since the analog unit performs the orthogonal demodulation processing, it is not necessary to operate the AD conversion unit and the digital circuit at a high speed, and rate conversion by a decimator or the like accompanied by deterioration in signal quality. Since a configuration that does not perform processing is easy, high-precision reception processing can be performed with a low-speed and small-scale inexpensive digital circuit.

  In the first embodiment, two OFDM signal demodulation units 150 and 151 are arranged in parallel, but the same effect can be obtained even if three or more OFDM signal demodulation units are provided in parallel. . In the first embodiment, the LPF and the AGC unit are separate blocks. For example, in a case where the LPF and the AGC unit are configured in an LSI, a configuration in which filters and AGC amplifiers are alternately arranged is common. If the AGC unit is configured not to be distorted by signals other than its own carrier due to the out-of-band suppression of the LPF, the same effect can be obtained even with such a configuration. Further, in the first embodiment, the signal distribution unit 119 performs signal distribution operations for the number of signal demodulation units, but the signal bands of the respective OFDM signal demodulation units are different and are input to the respective OFDM signal demodulation units. It is sufficient that the signal to be transmitted does not deteriorate in each assigned band, and it is not always necessary to distribute the signals in the same phase and level. Also, according to the first embodiment, the signal demodulating unit performs OFDM demodulation on the band in which the reception band is equally distributed, but each signal demodulating unit can also process different numbers of FFTs. Need not be equally distributed. Also, in order to support multiple bands with different radio frequency bands, the antenna, duplexer, low noise amplifier, quadrature demodulator, local signal generator have multiple similar elements inside, and the receiving device switches The same effect is obtained in the controlled configuration.

(Embodiment 2)
FIG. 3 is a block diagram showing a configuration of receiving apparatus 300 according to Embodiment 2 of the present invention.

  The receiving apparatus 300 has a configuration in which the signal distributing unit 119 is eliminated from the receiving apparatus 100 according to the first embodiment shown in FIG.

  The OFDM receiver 350 includes an antenna 310, an antenna duplexer 302, a low noise amplifier 303, and a signal demodulator 150. The OFDM receiver 351 includes an antenna 311, an antenna duplexer 304, a low noise amplifier 305, and a signal demodulator. 151. Here, the configuration of the analog unit in the OFDM receivers 350 and 351 is a direct conversion receiver, and the analog unit of the wireless receiver (OFDM receiver) of the second embodiment is configured by two direct conversion receivers. is doing.

  Next, the operation of receiving apparatus 300 will be described. The signal received by the antenna 310 is filtered by the antenna duplexer 302, amplified by the low noise amplifier 303, and input to the signal demodulator 150. Similarly, a signal received by the antenna 311 is filtered by the antenna duplexer 304, amplified by the low noise amplifier 305, and input to the signal demodulator 151. The signal demodulation units 150 and 151 perform demodulation processing by the same operation as in the first embodiment.

  Thus, according to the second embodiment, in addition to the effects of the first embodiment, a configuration using an existing direct conversion receiver (LSI) is possible, and an inexpensive receiver can be realized. In addition, a high-quality radio receiver can be realized by selecting a proven LSI. Furthermore, even when newly designing an LSI, it is possible to make use of the conventional process technology. This makes it possible to reduce the number of trial productions and reduce costs.

(Embodiment 3)
FIG. 4 is a block diagram showing a configuration of receiving apparatus 400 according to Embodiment 3 of the present invention.

  The receiving apparatus 400 has an OFDM signal receiving function for processing a received signal of a wideband OFDM system (first communication system), and parallel reception is difficult in a narrow band compared to an OFDM signal, for example, a CDMA system (second communication system) A CDMA signal receiving function for processing the received signal.

  Receiving apparatus 400 has an antenna 401, an antenna duplexer 402, and a low noise that are operable in two frequency bands of an OFDM signal frequency and a CDMA signal frequency with respect to receiving apparatus 100 of the first embodiment shown in FIG. It comprises an amplifier 403 and signal demodulation units 450 and 151.

  The signal demodulator 450 includes an orthogonal demodulator 404 and a digital processor 412, and the digital processor 412 includes AD converters 120 and 121, a system selector 410, an OFDM signal digital processor 413, and a CDMA signal. The other system demodulation part 411 for demodulating the signal of other systems etc. is comprised. When demodulating the CDMA signal, the other system demodulation unit 411 performs demodulation for all bands in a lump.

  The system selection unit 410 operates so as to input the output signals of the AD conversion units 120 and 121 to an OFDM signal digital processing unit 413 or another system demodulation unit 411 at an optimum data rate by a control signal (not shown). . The other system demodulation unit 411 demodulates the signal by a process such as despreading, for example.

  Next, the operation of receiving apparatus 400 will be described. The receiving apparatus 400 operates to input the output of the system selection unit 410 to the OFDM signal digital processing unit 413 when receiving the OFDM signal. In this case, the output signal of OFDM signal digital processing section 413 is combined with the output signal of OFDM signal digital processing section 117 by P / S conversion section 118 as in the processing of the first embodiment. At this time, the other system demodulating unit 411 is not used, and thus can save power. Further, when receiving a signal of another system such as a CDMA signal, control is performed so that the output of the system selection unit 410 is input to the other system demodulation unit 411.

  When receiving a signal of another system, the signal received by the antenna 401 is filtered by the antenna duplexer 402, amplified by the low noise amplifier 403, and input to the quadrature demodulation unit 404 via the signal distribution unit 119. To do. The I and Q signals output from the quadrature demodulator 404 are band-limited by the LPFs 108 and 109, level-converted by the AGC units 112 and 113 to an optimum level for the AD converters 120 and 121, and input to the digital processor 412. Is done. In the digital processing unit 412, the signal converted into the digital signal is demodulated by the other system demodulation unit 411. At this time, since the signal demodulator 151, the OFDM signal digital processor 413, and the P / S converter 118 are not used, it is possible to save power.

  In general, when a high speed device and a low speed device are operated at the same speed in a digital circuit, the high speed device consumes more power, so that the wireless receiver of the present invention is a simple conventional wireless device when operating other systems. Lower power consumption than receivers.

  In the configuration of FIG. 4, in the antenna 401, the antenna duplexer 402, and the low noise amplifier 403, when the OFDM signal and the signal of the other system are in different frequency bands and the operation is difficult in both frequency bands, Configuration can be taken. 5 is different from the receiving apparatus 400 shown in FIG. 4 in that the antenna 501, the antenna duplexer 502, the low-noise amplifier 503, the switch 510, and the wideband OFDM antenna 504 are used. The antenna duplexer 505 and the low noise amplifier 506 are provided.

  When receiving a broadband OFDM signal, the switch 510 serving as a switching unit operates to connect the signal distributor 119 and the orthogonal demodulator 404, and when receiving another system such as a narrowband CDMA signal, the switch 510 is low. It operates to connect the noise amplifier 503 and the quadrature demodulator 404. In such a receiving apparatus 500 as well, the signal demodulator 450 can be shared for receiving OFDM signals and signals of other systems.

  Further, according to the third embodiment, the passband of the LPF is obtained by dividing the I and Q signal bandwidths of the divided OFDM signals below the I and Q signal bandwidths of other systems, and the FFT bandwidth of the OFDM signal. By setting the bandwidth of the I and Q signals of the other system to be equal to or larger than that, even when the bandwidth of the OFDM signal and that of the other system are different, demodulation can be performed without causing degradation due to the band limiting process. This is because in a system using an OFDM signal, it is not always necessary to extract information from all FFT-treated subcarriers, and subcarriers to be used and subcarriers to be used can be selected. This is because the used subcarriers and the unused subcarriers can be separated. An actual active filter has a function of adjusting a cutoff frequency. Having this function, the cut-off frequency can be slightly optimized in the first communication method and the second communication method.

  As described above, according to the third embodiment, in addition to the effect of the first embodiment, by using one orthogonal demodulation unit sequence of the parallel OFDM receiver when receiving other systems, The analog circuit below the quadrature demodulator can be shared in an optimal state for both systems. Further, according to the third embodiment, it is possible to reduce the size and cost without degrading performance and to reduce power consumption when receiving an OFDM signal and a signal of another system.

(Embodiment 4)
FIG. 6 is a block diagram showing a configuration of receiving apparatus 600 according to Embodiment 4 of the present invention.

  The receiving apparatus 600 has a wide-band OFDM signal receiving function and a receiving function for receiving a CDMA signal, for example, which is difficult to receive in parallel in a narrow band compared to the received OFDM signal.

  Receiving apparatus 600 is different from receiving apparatus 300 shown in FIG. 3 in that antennas 601 and 604, antenna duplexers 602 and 605, and low noise amplifiers 603 and 606 that can operate in two frequency bands of an OFDM signal frequency and a CDMA signal frequency. , Quadrature demodulation units 607 and 608, system selection unit 609, other system demodulation unit 613, and OFDM signal digital processing unit 611 in digital processing unit 650, and system selection unit 610 and other system in digital processing unit 651. The demodulator 614 and the OFDM signal digital processor 612 are provided. In addition, a synthesizing unit 654 that synthesizes the outputs of a plurality of other system demodulation units 613 and 614 is provided. The system selection units 609 and 610 perform the same operation as the system selection unit 410 shown in FIG. Similarly, the other system demodulation units 613 and 614 perform the same operation as the other system demodulation unit 411 shown in FIG.

  Next, the operation of receiving apparatus 600 will be described. 6 receives the OFDM signal, and operates so that the output of the system selection unit 609 is input to the OFDM signal digital processing unit 611 and the output of the system selection unit 610 is input to the OFDM signal digital processing unit 612. . Then, similarly to the processing in the first embodiment, the output signals of the OFDM signal digital processing units 611 and 612 are synthesized by the P / S conversion unit 118.

  On the other hand, when receiving another system, the signal received by antenna 601 is filtered by antenna duplexer 602, amplified by low noise amplifier 603, and input to quadrature demodulator 607. The I and Q signals output from the quadrature demodulating unit 607 are band-limited by the LPFs 108 and 109, converted to optimum levels by the A / D converters 120 and 121 by the AGC units 112 and 113, and sent to the digital processing unit 650. Entered. In the digital processing unit 650, the AD converted signal is demodulated by the other system demodulation unit 613.

  Similarly, the antenna 604 receives the same signal as the signal received by the antenna 601, is filtered by the antenna duplexer 605, is amplified by the low noise amplifier 606, and is input to the quadrature demodulation unit 608. The I and Q signals output from the quadrature demodulator 608 are band-limited by the LPFs 110 and 111, converted to optimum levels for the AD converters 124 and 125 by the AGC units 114 and 115, and sent to the digital processing unit 651. Entered. In the digital processing unit 651, the AD converted signal is demodulated by the other system demodulation unit 614. Then, the output signals of the other system demodulation units 613 and 614 are diversity combined by the combining unit 654 by diversity reception processing.

  As described above, according to the fourth embodiment, in addition to the effects of the first embodiment, when receiving other systems, a configuration is adopted in which reception combining processing is performed using the orthogonal demodulator sequence of the parallel radio receiver. Therefore, it is possible to achieve high performance of the receiver while reducing the size and cost. Further, according to the fourth embodiment of the present invention, the reception frequencies of a plurality of signal demodulation units can be made variable independently, and one signal demodulation unit is confirmed and received at the time of diversity reception of a CDMA signal. By using the device, for example, it is possible to check the reception status of other carriers in the multicarrier system and the reception status of other systems. Further, according to the fourth embodiment, in a system having a plurality of carriers such as multi-carrier DS-CDMA in another system, different carriers are received by setting different local frequencies for each signal demodulator sequence. Thus, it is possible to perform synthesis processing and realize a high-performance function.

(Embodiment 5)
FIG. 7 is a block diagram showing a configuration of receiving apparatus 700 according to Embodiment 5 of the present invention.

  The receiving apparatus 700 has a configuration including switching LPFs 701, 702, 703, and 704 with respect to the receiving apparatus 600 shown in FIG.

  FIG. 8 is a block diagram showing the configuration of the switchable LPFs 701, 702, 703, and 704. The switchable LPFs 701, 702, 703, and 704 include a filter circuit 801, a delay equalization circuit 802, and switches 803 and 804.

  The switchable LPFs 701, 702, 703, 704 control the switches 803, 804 so that the I and Q signals pass through the delay equalization circuit 802 when other system signals are received, so that the delay variation of the filter circuit 801 is compensated. To work. On the other hand, when receiving the OFDM signal, the switches 803 and 804 are controlled so that the I and Q signals bypass the delay equalization circuit 802.

  In general, when the CDMA signal has a group delay deviation within the band, the signal quality deteriorates in the demodulation process, so that delay correction by the delay equalization circuit 802 is effective. However, in the OFDM signal, even when there is a group delay deviation in the band, if the delay characteristics of the I and Q signals are the same in each subcarrier, the signal quality in the demodulation process does not deteriorate. When the OFDM signal I and Q signals are routed through the delay equalization circuit 802 configured by an analog circuit, the delay difference in the band is reduced, but due to device variations, the I and Q deviations in each subcarrier are increased. This leads to quality degradation.

  As described above, according to the fifth embodiment, in addition to the effects of the first embodiment, the delay in the switched LPF is matched to the reception state of signal reception of other systems such as OFDM signal reception and CDMA signal. By switching the equalization circuit 802, it is possible to suppress degradation in demodulation processing in the reception state of both signals.

  The receiving apparatus and demodulation method according to the present invention are particularly suitable for use in mobile communication systems and terrestrial digital broadcast reception.

The block diagram which shows the structure of the receiver which concerns on Embodiment 1 of this invention. The block diagram which shows the spectrum which concerns on Embodiment 1 of this invention The block diagram which shows the structure of the receiver which concerns on Embodiment 2 of this invention. The block diagram which shows the structure of the receiver which concerns on Embodiment 3 of this invention. The block diagram which shows the other structure of the receiver which concerns on Embodiment 3 of this invention. The block diagram which shows the structure of the receiver which concerns on Embodiment 4 of this invention. FIG. 9 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 5 of the present invention. The block diagram which shows the structure of the filter which concerns on Embodiment 5 of this invention. Block diagram showing the configuration of a conventional band division OFDM receiver The figure which shows the spectrum of the band division type OFDM receiver of FIG. A block diagram showing another configuration of a conventional band division OFDM receiver The figure which shows the relationship between the receiving bandwidth in the OFDM receiver of FIG. 11, and the output signal from each BPF.

Explanation of symbols

100 receiver 101 antenna 102 antenna duplexer 103 low noise amplifier 104, 105 quadrature demodulator 106, 107 local signal oscillator 108, 109, 110, 111 LPF
112, 113, 114, 115 AGC unit 116, 117 OFDM signal digital processing unit 118 P / S conversion unit 119 Signal distribution unit 120, 121, 124, 125 AD conversion unit 122, 126 FFT unit 123, 127 Decoding unit 150, 151 Signal demodulator

Claims (9)

Orthogonal demodulation means for generating an I signal and a Q signal by performing orthogonal demodulation processing on the received signal in parallel for each predetermined band;
Baseband signal processing means for controlling the gains of the I signal and the Q signal in parallel for each band while allowing the I signal and the Q signal to pass through only the low band in parallel for each band;
Demodulating means for controlling the gain by the baseband signal processing means and demodulating the I signal and the Q signal passed through the baseband signal processing means in parallel for each band;
A receiving apparatus comprising: Receiving means for receiving a received signal with one antenna;
Signal distribution means for dividing the received signal received by the receiving means into signals for each band;
2. The quadrature demodulating unit generates an I signal and a Q signal by performing quadrature demodulation processing on the signal divided by the signal distribution unit for each band in parallel for each band. Receiver device. It has a receiving means which has a plurality of antennas and receives signals of the above-mentioned different bands for each antenna,
The receiving apparatus according to claim 1, wherein the orthogonal demodulating unit generates an I signal and a Q signal by performing orthogonal demodulation processing on the signal received by the receiving unit for each band in parallel for each band. . The orthogonal demodulation means generates an I signal and a Q signal by performing orthogonal demodulation processing in parallel for each band when receiving a reception signal of a first communication system that processes a wideband reception signal, When receiving the received signal of the second communication system that processes the received signal of the narrow band, the I and Q signals are generated by performing orthogonal demodulation processing for all the bands at once,
The baseband signal processing means allows the I signal and the Q signal to pass through only a low band in parallel for each band when receiving the reception signal of the first communication system, and At the time of reception, only the low band is allowed to pass for all bands at the same time, and the gains of the I signal and the Q signal are controlled in parallel for each band at the time of reception of the received signal of the first communication system, and the second When receiving the received signal of the communication system, control all the bands at once,
The demodulating unit controls the gain of the baseband signal processing unit and the I signal and the Q signal that have passed through the baseband signal processing unit when the received signal of the first communication system is received. The receiving apparatus according to any one of claims 1 to 3, wherein the receiving apparatus demodulates in parallel each time and demodulates all bands at the same time when receiving a reception signal of the second communication system.   5. The receiving apparatus according to claim 4, further comprising a combining unit that diversity-combines received signals of the second communication system demodulated all over the band by the demodulating unit.   The baseband signal processing means performs delay correction by passing only a low frequency band for the I signal and the Q signal of the second communication system, and performs the I signal and the Q signal of the first communication system. 6. The receiving apparatus according to claim 4, wherein only the low frequency band is passed and no delay correction is performed.   Switching means for distributing the reception signal of the first communication system to the plurality of orthogonal demodulation means for each band and outputting the reception signal of the second communication system to one of the orthogonal demodulation means; The receiving device according to any one of claims 4 to 6.   The receiving apparatus according to any one of claims 4 to 7, wherein the first communication system is an OFDM system and the second communication system is a CDMA system. Orthogonally demodulating received signals in parallel for each predetermined band to generate I and Q signals;
Passing only the low band by passing the I signal and the Q signal in parallel for each band through a low-pass filter and controlling the gain of the I signal and the Q signal in parallel for each band; ,
Demodulating the I signal and the Q signal, whose gain is controlled and passed through the low-pass filter, in parallel for each band;
A demodulating method comprising:

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