WO2007007761A1

WO2007007761A1 - Receiving apparatus and receiving method

Info

Publication number: WO2007007761A1
Application number: PCT/JP2006/313784
Authority: WO
Inventors: Kazuhiko Takeyama; Takashi Enoki
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2005-07-12
Filing date: 2006-07-11
Publication date: 2007-01-18
Also published as: JP2007027879A

Abstract

A receiving apparatus capable of suppressing non-desired signals even when using a band limiting filter, the suppression characteristic of which is not steep and which exhibits variation in frequency characteristic, in a multicarrier communication. In this apparatus, a frequency selecting part (112) selects a control frequency (Δf), which controls the frequency of a frequency-variable local signal oscillator (113), such that a noise signal shifts to a suppressing band of the band limiting filter. The frequency selecting part (112) outputs the control signal, which is to shift the frequency by (Δf), to the frequency-variable local signal oscillator (113), while outputting information about the control frequency (Δf) to a decoding part (114). The decoding part (114) selects, based on the information of the control frequency (Δf) from the frequency selecting part (112), a subcarrier to which information data is assigned, thereby performing an OFDM decoding.

Description

Receiving apparatus and receiving method

Technical field

TECHNICAL FIELD [0001] The present invention relates to a receiving device and a receiving method, and more particularly to a receiving device and a receiving method in a system to which multicarrier communication is applied.

Background art

[0002] In recent years, even in mobile communication systems, studies have been made to increase system capacity in order to provide a throughput of 100 Mbps or higher over a wide range of coverage. For example, mobile communication with a radio bandwidth of 100 MHz or higher has been studied. Studies using the system have been reported.

[0003] An OFDM (Orthogonal Frequency Division Multiplex) system is known as a transmission system using a wide bandwidth of a radio bandwidth of 100 MHz (see Non-Patent Document 1 and Non-Patent Document 2). The OFDM signal is a frequency division multiplexing digital modulation method that transmits digital information using multiple orthogonal subcarriers. It is multipath-resistant, is not susceptible to interference in other transmission systems, is not susceptible to interference, and is used in frequency. It has characteristics such as relatively high efficiency.

[0004] Incidentally, as an OFDM receiver, for example, one disclosed in Patent Document 1 is known. FIG. 1 is a configuration diagram showing an example of a wideband signal receiving apparatus using an OFDM decoding algorithm (see Patent Document 1). A receiving apparatus 10 shown in FIG. 1 includes an antenna 11, a front end unit 12, a band limiting unit 13, an A / D (Analog to Digital) conversion unit 14, and an OFDM signal processing unit 15.

[0005] The front end unit 12 amplifies the received signal with low noise and converts it to an IF (Intermediate Frequency) frequency.

[0006] The band limiting unit 13 includes a wide band filter 16 and a band suppression filter (notch filter) 17 that gives sharp attenuation to a specific frequency.

[0007] The wideband filter 16 extracts the band of the OFDM signal converted into the IF frequency band.

Generally, in a mobile communication system, a frequency selective filter is used as a band limiting filter. An excellent filter, for example, a SAW (Surface Acoustic Wave) filter using a surface vibration wave of a piezoelectric element is often used. Also, in direct conversion receiver ICs that convert received signals to baseband frequencies without converting them to IF frequencies, band limiting is performed using a low-pass filter in the baseband frequency band! Yes.

[0008] The band suppression filter 17 removes adjacent interference components that cannot be removed by the wideband filter 16 alone. Normally, the band suppression filter 17 affects the phase in the OFDM band. However, in the case of OFDM, the phase change is compensated by equalization and demodulation processing of delay detection, so the phase effect is virtually eliminated. It has a special feature.

The AZD conversion unit 14 performs A / D conversion on the signal band-limited by the band limiting unit 13 and outputs the AZD-converted signal to the OFDM signal processing unit 15.

[0010] The OFDM signal processing unit 15 has functions of orthogonal demodulation processing, FFT (Fast Fourier Transform) processing, and channel estimation processing, and performs OF DM decoding processing on the AZD converted signal. .

[0011] By the way, in the AZD conversion unit 14, it is desirable that the oversampling number is as large as possible. However, it is generally difficult to increase the oversampling number in consideration of the power consumption of the logic components, the device volume, the cost, and the like. Therefore, there is a possibility that the noise signal is folded back and enters the signal band by the sampling in the AZD converter 14. Therefore, it is indispensable to provide a band limiting filter having a steep frequency characteristic before the AZD conversion unit 14.

Non-patent document 1: ITU—RS contribution (TGI 1Z3)

Non-Patent Document 2: Television Society Research Report Vol.17, No.54, p7-12, BCS 93-33 (Sep.l99 3)

Patent Document 1: Japanese Patent Laid-Open No. 2000-13357

Disclosure of the invention

Problems to be solved by the invention

However, when trying to realize a band limiting filter that has a steep suppression characteristic and has no variation in frequency characteristics, the circuit scale increases and the cost increases. There is a title. Furthermore, when a semiconductor filter is used, there is a problem that power consumption increases due to an increase in the filter order.

[0013] An object of the present invention is to provide a receiving apparatus and a receiving apparatus that can suppress undesired signals even when a band-limiting filter having a non-steep suppression characteristic and a variation in frequency characteristics is used in multicarrier communication. Is to provide a method.

Means for solving the problem

[0014] In order to solve a problem, a receiving apparatus according to the present invention includes a receiving unit that receives a signal including frequency components corresponding to a plurality of carriers to which information data is assigned, and all of the signals included in the received signal. Frequency conversion means for shifting the frequency component frequency, a filter for suppressing the frequency-shifted frequency of some of the frequency components included in the received signal, and the plurality of frequency components among the frequency components remaining without being suppressed. Decoding means for decoding a frequency component corresponding to a carrier, wherein the frequency conversion means matches the frequency of an undesired frequency component whose reception quality does not satisfy a predetermined standard with a frequency suppressed by the filter. Use a configuration that allows

The invention's effect

[0015] According to the present invention, undesired signals can be suppressed even in the case of using a band limiting filter having a variation in frequency characteristics that is not sharp in suppression characteristics in multicarrier communication.

Brief Description of Drawings

FIG. 1 is a block diagram showing a configuration of a conventional receiving apparatus

FIG. 2 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 1 of the present invention.

[Figure 3] Diagram showing frequency characteristics of OFDM signal

[Figure 4] Diagram showing frequency characteristics of desired signal and nearby noise

FIG. 5 is a diagram showing frequency characteristics of a received signal in the IF frequency band of the receiving apparatus according to Embodiment 1.

FIG. 6 is a diagram showing frequency characteristics of a received signal in the IF frequency band of the receiving apparatus according to Embodiment 1.

FIG. 7 shows the frequency characteristics of the received signal in the IF frequency band of the receiving apparatus according to Embodiment 1. Figure

[FIG. 8] A diagram showing the frequency characteristics of the received signal in the IF frequency band of the receiving apparatus according to Embodiment 1.

FIG. 9 is a diagram showing the frequency characteristics of the received signal in the IF frequency band of the receiving apparatus according to Embodiment 1.

FIG. 10 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 2 of the present invention.

FIG. 11 is a diagram showing frequency characteristics of frequency domain signals after fast Fourier transform of the receiving apparatus according to Embodiment 2;

FIG. 12 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 3 of the present invention.

FIG. 13 shows frequency characteristics of frequency domain signals after fast Fourier transform of the receiving apparatus according to Embodiment 3.

FIG. 14 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 4 of the present invention.

[Figure 15] Figure showing the frequency characteristics of desired and undesired signals after undersampling

FIG. 16 is a diagram showing frequency characteristics of a received signal, a band suppression filter, and a bandpass filter in the IF frequency band of the receiving apparatus according to Embodiment 4

FIG. 17 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 5 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

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

[0018] (Embodiment 1)

FIG. 2 is a block diagram showing a configuration of receiving apparatus 100 according to Embodiment 1 of the present invention. The receiving apparatus 100 shown in FIG. 2 includes an antenna 101, an antenna sharing unit 102, a low noise amplification unit 103, a frequency conversion unit 104, a bandpass filter 105, an AGC (Auto Gain Control) 106, an oral signal oscillator 107, an orthogonal Demodulator 108, low-pass filter 109-1, low-pass filter 109-2, AZD converter 110-1, AZD converter 110-2, FFT unit 111, frequency selector 112, frequency variable local A signal oscillator 113 and a decoding unit 114 are provided.

[0019] The antenna sharing unit 102 is illustrated as a receiving system in which the antenna 101 is configured by the above blocks. Share with a non-transmission system.

The low noise amplification unit 103 amplifies the received signal with low noise and outputs the amplified signal to the frequency conversion unit 104.

[0021] Frequency conversion section 104 multiplies the amplified received signal by a local signal output from frequency variable local signal oscillator 113 to convert it to an IF frequency, and outputs the converted IF signal to bandpass filter 105 To do.

[0022] The bandpass filter 105 limits the band of the IF signal and outputs the obtained IF signal to the AGC 106.

[0023] The AGC 106 adjusts the amplitude level of the IF signal to an optimum level by using the AZD conversion unit 110-1 and the AZD conversion unit 110-2 in the subsequent process, and orthogonally recovers the level-adjusted IF signal. Output to control unit 108.

The local signal oscillator 107 converts a local signal having a frequency f (MHz) into a quadrature demodulator 108.

if

Output to.

The quadrature demodulator 108 converts the level-adjusted IF signal into I and Q baseband signals, and converts the obtained baseband signal into a low-pass filter 109-1 and a low-pass filter 109. — Output to 2.

[0026] The low-pass filter 109-1 and the low-pass filter 109-2 remove unnecessary components from the I and Q baseband signals, respectively, and obtain the obtained I and Q baseband signals. Output to AZD converter 110-1 and AZD converter 110-2.

[0027] The AZD conversion unit 110-1 and the AZD conversion unit 110-2 are used for I and Q baseband signals.

AZD conversion is performed, and the AZD converted I and Q baseband signals are output to the FFT unit 111.

[0028] The FFT unit 111 performs fast Fourier transform on the AZD-converted I and Q baseband signals to convert a time domain signal into a frequency domain signal. The FFT unit 111 outputs the obtained frequency domain signal to the decoding unit 114.

[0029] Frequency selection section 112 measures the filter characteristics of bandpass filter 105 output from a filter characteristic measurement section (not shown) and the frequency arrangement of its own channel or the noise signal frequency measurement section (not shown). Noise based on the noise signal frequency and level The control frequency Δ ί that controls the frequency of the frequency variable low-power signal oscillator 113 is selected so that the signal shifts to the suppression band of the bandpass filter 105. For example, when there is a signal of a system other than the OFDM signal constantly in the reception environment, the frequency selection unit 112 selects the control frequency Δ ί using the frequency of the signal of the other system as the frequency of the noise signal. The frequency selection unit 112 outputs a control signal for shifting the frequency by Δί to the variable frequency local signal oscillator 113 and outputs the information about the control frequency Δ f to the decoding unit 114.

The variable frequency local signal oscillator 113 generates a local signal having a frequency f −f Δ ί (MHz) based on the control signal output from the frequency selection unit 112 and performs frequency conversion.

c if

Output to part 104. Here, f represents the center frequency of the OFDM signal, and Δ ί represents the control frequency selected by the frequency selection unit 112.

[0031] Decoding section 114 performs OFDM decoding on the signal converted to the frequency domain. At this time, based on the information on the control frequency Δί output from the frequency selection unit 112, the subcarrier to which the information data is assigned is selected, and OFDM decoding is performed. Subcarrier selection will be described in detail later. Decoding section 114 outputs the received data obtained to the subsequent process.

[0032] Next, a reception operation by the receiving apparatus 100 configured as described above will be described.

The OFDM signal is output to low noise amplification section 103 via antenna 101 and antenna sharing section 102. Then, the received signal is amplified by low noise amplification section 103 and output to frequency conversion section 104.

[0034] The amplified received signal is multiplied by the local signal output from the frequency variable local signal oscillator 113 by the frequency converter 104 and converted to an IF frequency, and the converted IF signal is converted into a bandpass filter 105. Is output. At this time, the frequency of the local signal output from the frequency variable low-power signal oscillator 113 is shifted by the control frequency Δf selected by the frequency selector 112. The selection of the control frequency Δf controlled by the frequency selection unit 112 will be described in detail later.

A control signal for shifting the frequency by Δ ί is output to frequency variable local signal oscillator 113, and information about control frequency Δ ί is output to decoding unit 114. Is done.

[0036] Then, the IF signal converted to the IF frequency is band-limited by the bandpass filter 105, and the obtained IF signal is output to the AGC 106. And by AGC106, I

The F signal is adjusted to an optimum level by the AZD conversion unit 110-1 and the AZD conversion unit 110-2, and is output to the quadrature demodulation unit 108.

[0037] The level-adjusted IF signal is multiplied by a local signal from which the local signal oscillator 107 output is also output by the quadrature demodulator 108, and converted into an I and Q baseband signal.

[0038] The I and Q baseband signals pass through the low-pass filter 109-1 and the low-pass filter 109-2, respectively, and then pass through the AZD converter 110-1 and the AZD converter 110-2.

AZD conversion is performed and output to FFT section 111.

Then, the I and Q baseband signals are converted into signals in the time domain force frequency domain by the FFT unit 111, and the frequency domain signal is output to the decoding unit 114.

[0040] Based on the control frequency Δί output from the frequency selection unit 112, the decoding unit 114 selects a subcarrier to which the information data is assigned, and performs OFDM decoding. Received data obtained by OFDM decoding is output to a subsequent process.

[0041] Next, the receiving operation when receiving apparatus 100 receives an OFDM signal as shown in FIG. 3 will be described.

FIG. 3A shows frequency characteristics of an OFDM signal having a center frequency f (MHz) and a signal bandwidth of 50 MHz composed of 682 subcarriers (USC). In FIG. 3A, the horizontal axis represents frequency (MHz), the second horizontal axis represents subcarrier (SB) number, and the vertical axis represents power (dBm).

By the way, in an OFDM transmitter, a time domain signal is generated from a frequency domain signal by IFFT (Inverse Fast Fourier Transform). Time domain signals are often calculated using the number of power subcarriers. However, in general, the OFDM signal is often not composed of a power of 2 subcarrier due to the limitation of the subcarrier spacing due to the phase noise of the local frequency. Therefore, the transmitting apparatus assigns null data to subcarriers, and generates a power-of-two subcarrier. Specifically, 682 subs as shown in Figure 3A. An OFDM signal with a signal bandwidth of 50 MHz consisting of carriers is assigned information data only to 682 subcarriers out of 1024 subcarriers, and the remaining 342 subcarriers are assigned null data as unused subcarriers. Thus, the power of unused subcarriers is generated with zero. As a result, in the radio frequency band, an OFDM signal composed of 682 subcarriers is transmitted with a signal bandwidth of 50 MHz.

Consider a case where the receiving apparatus 100 receives the OFDM signal shown in FIG. 3A. Figures 3B, 3C, and 3D show f -f (MHz), f -f + 12.5 (MHz), and f --f --12. 5 (MHz) local signal c if c if c if

Signal and frequency converter 104, and f

if

The frequency characteristics of the baseband signal multiplied by the local signal (MHz) and input to the low-pass filter 109-1 and low-pass filter 109-2 are shown. In FIGS. 3B, 3C, and 3D, as in FIG. 3A, the horizontal axis represents frequency (MHz), the second horizontal axis represents subcarrier (SB) number, and the vertical axis represents power (dBm). Show me.

[0045] At this time, as described above, the decoding unit 114 selects and demodulates the used subcarriers to which the information data is assigned, so that the receiving apparatus 100 can perform frequency characteristics shown in FIGS. 3B, 3C, and 3D. Any baseband signal with can be demodulated.

[0046] For example, for the OFDM signal shown in FIG. 3B, information data is obtained by selecting subcarrier numbers 172 to 853 as used subcarriers and performing OFDM decoding in the same manner as the OFDM signal shown in FIG. 3A. Can be decrypted. Also, for the OFDM signal shown in FIG. 3C, information data can be decoded by selecting subcarrier numbers 1 to 682 as used subcarriers and performing OFDM decoding. For the OFDM signal shown in FIG. 3D, information data can be decoded by selecting subcarrier numbers 342 to 1024 as used subcarriers and performing OFDM decoding.

That is, in frequency converter 104, the frequency band in which the power of 2 subcarrier power used in the fast Fourier transform is also configured, that is, the subcarrier used is included in the frequency range that can be decoded in decoder 114. When the frequency conversion is performed, the decoding unit 114 correctly detects the used subcarriers, so that all the used subcarriers are detected. It is possible to decrypt information data using For example, for an OF DM signal as shown in FIG. 3A, if the control frequency Δ ί satisfies −12.5 ≦ Δ ί≤12.5Η (ΜΗζ), the subcarrier to which the information data is assigned is assigned. It is possible to decrypt information data using all of these.

[0048] Hereinafter, a method of controlling the frequency of the local signal output from the frequency variable local signal oscillator 113, selecting a subcarrier based on the control frequency Δf, and performing OFDM decoding is described as "OFDM signal sub "Carrier offset demodulation".

[0049] Next, the receiving operation when receiving apparatus 100 receives an OFDM signal and a noise signal as shown in FIG. 4 will be described. In Fig. 4, the horizontal axis shows the frequency (MHz), the vertical axis shows the noise signal in the vicinity of the OFDM signal with power (dBm), center frequency f (MHz), and bandwidth 50MHz. Yes. The noise signal is 57MHz higher than its center frequency f (MHz) force and has a bandwidth of 12MHz.

[0050] In the following, it is assumed that the sampling frequency f of the AZD conversion unit 110-1 and the AZD conversion unit 110-2 is 75 MHz. At this time, the received signal s in the IF frequency band of receiving apparatus 100

Figure 5A shows the frequency characteristics of the signal. In FIG. 5A, the horizontal axis represents frequency (MHz), the vertical axis represents signal level (dBm), and the second vertical axis represents filter suppression (dB). Note that the horizontal axis is the frequency (MHz) and the vertical axis is the signal level (d

Bm), the second vertical axis represents the amount of filter suppression (dB).

[0051] FIG. 5A shows the OFDM signal, the filter characteristics of the bandpass filter 105, the noise signal, and the noise signal after passing through the bandpass filter 105 as the desired signal, filter characteristics, neighborhood noise, and input noise, respectively. Show me.

FIG. 5B shows the frequency characteristics of the desired signal and input noise in the baseband frequency band output from quadrature demodulator 108.

[0053] Sampling frequency in AZD converter 110-1 and AZD converter 110-2 is

In the case of 75 MHz, frequency components higher than 37.5 (= 75Z2) MHz are folded back into the band. Therefore, after the AZD conversion, the aliasing noise shown in FIG. 5B is input into the band.

[0054] FIG. 6A is a graph obtained when the slope of the suppression characteristic of the bandpass filter 105 is relaxed compared to FIG. 5A. Shows the frequency characteristics of the received signal in the IF frequency band. From FIG. 6A, it can be seen that the input noise after passing through the band-pass filter 105 is larger than that in FIG. 5A. As shown in Fig. 6B, the noise signal level that is folded back in the band is also large, so the quality of the desired signal deteriorates due to the relaxation of the filter characteristics.

[0055] Here, the frequency of the frequency variable local signal oscillator 113 is f -f -6.25 (MHz).

C if

Thus, the case of demodulating using “OFDM signal subcarrier offset demodulation” will be described. At this time, as shown in Fig. 7A, the frequency characteristics of the received signal in the IF frequency band shift the desired signal and noise signal to 6.25 MHz toward the high frequency side. As a result, the noise signal 1S suppression amount shifts to a large frequency region, and the noise signal level after passing through the band-pass filter 105 becomes lower than that in FIG. 6A, and the same characteristics as in FIG. 5A can be obtained.

FIG. 7B shows frequency characteristics of the received signal in the baseband frequency band. As shown in Fig. 7B, it can be seen that the signal level folded back in the band is lower than that in Fig. 6B.

[0057] As described above, since the control frequency Δ ί is within the range of −12.5 ≦ Δ ί ≦ 12.5Η (MHz), the subcarrier is appropriately selected based on the control frequency Δ ί. This makes it possible to OFDM-decode the desired signal.

That is, even when the suppression characteristic of the band limiting filter is relaxed by shifting the frequency of the frequency variable local signal oscillator 113 using “OFDM signal subcarrier offset demodulation” and demodulating, The noise signal can be removed and OFDM decoding can be performed. As a result, a low-order filter can be used as the band limiting filter, and a low-power consumption filter can be used when an inexpensive semiconductor filter is used.

In the above-described example, the case where the suppression characteristic of the bandpass filter 105 has been described has been described. Next, the case where the frequency characteristic of the bandpass filter 105 is asymmetric with respect to the center frequency will be described. In general, there are variations in analog devices, and depending on how they vary, the performance of the machine may be degraded. For example, when the bandpass filter 105 having the filter characteristics shown in FIG. 5A as a basic value varies and the center frequency is shifted to the high frequency side, the filter characteristics shown in FIG. 8A are obtained. At this time, when the OFD M signal and the noise signal as shown in FIG. 4 pass through the band-pass filter 105 having the filter characteristics shown in FIG. 8A, the level of the input noise becomes larger than that in FIG. 5A. Also shown in Figure 8B. In addition, the level of the noise signal that is folded back within the band increases, and the quality of the received desired signal deteriorates.

[0060] In this case, the frequency of the variable frequency local signal oscillator 115 is set to f f 6.

C if

The case of demodulation using “OFDM signal subcarrier offset demodulation” at 25 (MHz) will be described. At this time, the IF frequency characteristics of the received signal after passing through the band-pass filter 105 shift the desired signal and the noise signal to 6.25 MHz to the high frequency side as shown in FIG. 9A. As a result, the noise signal shifts to the high frequency side, and the noise signal level after passing through the bandpass filter 105 becomes lower than that in FIG. 8A, and the same characteristics as in FIG. 5A can be obtained. In addition, as shown in FIG. 9B, the level of the noise signal folded back within the band is also similar to that in FIG. 5B.

That is, in the case where the frequency characteristics of the band-limiting filter vary by demodulating by shifting the frequency of the frequency variable local signal oscillator 113 using “OFDM signal subcarrier offset demodulation”. This eliminates the need for a variation correction circuit, reduces performance degradation due to variations in frequency characteristics, and eliminates noise signals and enables OFDM decoding.

As described above, according to the present embodiment, the frequency of frequency variable local signal oscillator 113 is controlled using “OFDM signal subcarrier offset demodulation” to filter undesired signals in the filter suppression band. Shift to, and OFDM decode. As a result, when the filter characteristics of the band limiting filter deteriorate, a circuit that corrects the deterioration is not required, the deterioration of the filter characteristic can be reduced, and undesired signals can be suppressed and OFDM decoding can be performed. The performance can be improved. In addition, since noise components input to the A / D conversion unit 110-1 and the AZD conversion unit 1102 are reduced, performance degradation due to quantization noise is reduced, and reception performance is improved.

[0063] In the above-described example, the case where the receiving apparatus 100 uses a bandpass filter has been described. However, the OFDM signal may also be used when converting to the baseband frequency band by direct conversion without converting to the IF frequency band. By applying subcarrier offset demodulation, even when the filter characteristics of the low-pass filter deteriorate, it is possible to suppress the undesired signal by avoiding the performance deterioration of the filter characteristics and perform OFDM decoding. Become.

[0064] Further, in the frequency selection unit 112, a filter output from a filter characteristic measurement unit (not shown). Instead of using the filter characteristic, the filter characteristic may be predicted using a temperature sensor. In general, devices such as SAW filters predict the fluctuation of the center frequency according to the temperature at which the center frequency fluctuates according to the temperature, and apply “OFDM signal subcarrier offset demodulation” as described above. The same effect as the OFDM receiver shown in Fig. 2 can be obtained.

[Embodiment 2]

The feature of Embodiment 2 of the present invention is that the frequency of the undesired signal is estimated and the undesired signal is shifted to the suppression band of the band limiting filter.

FIG. 10 is a block diagram showing a configuration of receiving apparatus 100 according to Embodiment 2 of the present invention. In the receiving apparatus of the present embodiment in FIG. 10, the same components as in FIG. 2 are assigned the same reference numerals as those in FIG. 10 employs a configuration in which a frequency selection unit 202 is provided instead of the frequency selection unit 112 and a noise measurement unit 201 is added to FIG.

[0067] The noise measuring unit 201 measures the signal power to noise power ratio of the noise signal in the vicinity of the desired signal for each frequency component, and the measured signal power to noise power. Frequency components whose ratio is equal to or greater than a predetermined threshold are determined (estimated) as noise signal frequencies. Regarding the measurement of the signal power-to-noise power ratio and the frequency of the noise signal in the noise measuring unit 201, the case where the bandpass filter 105 has the filter characteristics as shown in FIG. 5A and receives a signal as shown in FIG. To do.

[0068] Similarly to Embodiment 1, when the sampling clock f of the AZD conversion unit 110-1 and the AZD conversion unit 110-2 is 75 MHz, the baseband frequency s output from the orthogonal demodulation unit 108

The frequency characteristics of the desired signal and input noise in several bands are as shown in Fig. 5B. When the FFT unit 111 performs fast Fourier transform on the signal shown in FIG. 5B, the frequency characteristics of the output after the fast Fourier transform are shown in FIG. At this time, the noise measurement unit 201 measures the signal power to noise power ratio in unused subcarriers for each carrier, and the measurement result power also determines (estimates) the frequency of the noise signal. For example, when the noise measurement unit 201 detects that the signal power-to-noise power ratio is equal to or higher than a predetermined threshold when the subcarrier number 1 of the unused subcarriers is also 172 as shown in FIG. 11, noise is detected in the frequency domain. The signal exists or is higher frequency than the desired signal There is a noise signal, and it is estimated that the level has increased due to the aliasing, and the frequency of the noise signal is estimated. The noise measurement unit 201 outputs the estimated frequency of the noise signal and the signal power to noise power ratio to the frequency selection unit 202. The estimation method of the noise signal frequency and the signal power to noise power ratio is not limited to this, and other estimation methods may be used.

[0069] The frequency selection unit 202 is a frequency variable local signal oscillator so as to shift a noise signal having a measured signal power-to-noise power ratio for each carrier equal to or higher than a predetermined threshold to the suppression band of the bandpass filter 105. Select the control frequency Δ f that controls the frequency of 113. Then, the frequency selection unit 202 outputs a control signal for shifting the frequency by Δί to the frequency variable local signal oscillator 113, and outputs information about the control frequency Δf to the decoding unit 114. .

[0070] Next, a reception operation by the receiving apparatus 100 configured as described above will be described.

[0072] The amplified received signal is multiplied by the local signal output from the frequency variable local signal oscillator 113 by the frequency converter 104 and converted to an IF frequency, and the converted IF signal is converted into a bandpass filter 105. Is output. At this time, the frequency of the local signal output from the frequency variable low-power signal oscillator 113 is shifted by the control frequency Δ ί selected by the frequency selector 202. As described above, the control frequency Δ ί is selected from the level of the noise signal estimated by the noise measuring unit 201 so that a noise signal having a level equal to or higher than a predetermined threshold is shifted to the suppression band of the bandpass filter 105.

A control signal for shifting the frequency by Δ ί is output to frequency variable local signal oscillator 113, and information about control frequency Δ ί is output to decoding unit 114.

[0074] The IF signal converted into the IF frequency is the same as in the first embodiment. The bandpass filter 105, the AGC 106, the quadrature demodulation unit 108, the low-pass filter 109-1, and the low-pass filter The data is output to the FFT unit 111 via the filter 109-2, the AZD conversion unit 110-1 and the AZD conversion unit 110-2.

[0075] Then, the I and Q baseband signals are converted into time domain power frequency domain signals by the FFT unit 111, and the frequency domain signals are output to the decoding unit 114.

Thereafter, the decoding unit 114 selects the subcarrier number to which the information data is assigned based on the information on the control frequency Δί output from the frequency selection unit 112, as in the first embodiment, and performs OFDM. Decryption is performed. The obtained received data is output to the later stage.

As described above, according to the present embodiment, the frequency of the frequency variable local signal oscillator 113 is controlled by estimating the frequency of the undesired signal using “OFDM signal subcarrier offset demodulation”. Then, the undesired signal is shifted to the filter suppression band and subjected to OFDM decoding. As a result, even in an environment where the level and frequency of the undesired signal fluctuate, the undesired signal can always be suppressed and OFDM decoding can be performed, and reception performance can be improved.

[Embodiment 3]

The feature of Embodiment 3 of the present invention is that the subcarrier with the lowest level is detected and the subcarrier with the lowest level is shifted to the suppression band of the filter characteristics.

FIG. 12 is a block diagram showing the configuration of the receiving apparatus according to Embodiment 3 of the present invention.

In the receiving apparatus of the present embodiment in FIG. 12, the same components as in FIG. 2 are assigned the same reference numerals as in FIG. Fig. 12 shows a direct conversion receiving device. Compared with Fig. 2, AGC106, low-pass filter 109-1, low-pass filter 109-1, and frequency selector 112 are replaced with AGC302- 1, AGC302-2, low-pass filter 301-1, 1, low-pass filter 301-2, and frequency selector 30 4; frequency converter 104, bandpass filter 105, and local signal oscillator 1 07 Is deleted, and the level determination unit 303 is added.

[0080] The low-pass filter 301-1 and the low-pass filter 301-2 remove unnecessary components from the I and Q baseband signals, respectively, and use the obtained I and Q baseband signals. Output to AGC302-1 and AGC302-2. Note that the low-pass filter 301-1 and The low-pass filter 301-2 has a configuration that cuts the DC component by placing a capacitor in series in the signal transmission path (C coupling) to avoid DC offset caused by local signal leakage. Have it.

[0081] Level determination section 303 measures the signal level of each subcarrier from the frequency domain signal after the fast Fourier transform, and determines the subcarrier with the lowest reception level. Level determination section 303 outputs information about the determined subcarrier frequency to frequency selection section 304.

[0082] The frequency selection unit 304 uses the frequency of the subcarrier with the lowest reception level determined by the level determination unit 303 to determine whether the subcarrier is a low-pass filter 301-1 and a low-pass filter 301-2. The control frequency Δ ί of the variable frequency local signal oscillator 113 is selected so as to coincide with the suppression band. Then, the frequency selection unit 304 outputs a control signal for shifting the frequency by Δ ί to the frequency variable local signal oscillator 113 and outputs the information about the control frequency Δ f to the decoding unit 114. .

[0083] Next, a reception operation by the receiving apparatus 100 configured as described above will be described.

The OFDM signal is output to low noise amplification section 103 via antenna 101 and antenna sharing section 102. Then, the received signal is amplified by the low noise amplification unit 103 and output to the frequency modulation unit 108.

The amplified received signal is multiplied by the local signal output from frequency variable local signal oscillator 113 by frequency demodulator 108 and converted to an I or Q baseband signal. The converted baseband signal is output to the low-pass filter 301-1 and the low-pass filter 301-2. At this time, the frequency of the local signal output from the frequency variable local signal oscillator 113 is shifted by the control frequency Δf selected by the frequency selection unit 304. Selection of the control frequency Δf by the frequency selection unit 304 will be described with reference to FIG.

FIG. 13 shows a signal in the frequency domain after the fast Fourier transform output from the FFT unit 111, where the horizontal axis indicates the subcarrier number and the vertical axis indicates the signal level. As shown in FIG. 13, it is generally known that mobile communication has a frequency band in which the reception level drops due to propagation conditions such as fading. Figure 13 shows the frequency band with subcarrier number 520. This shows how the signal level drops in the area.

[0087] At this time, the frequency selection unit 304 makes the frequency of the subcarrier number 520 having the lowest reception level match the suppression band of the low-pass filter 301-1 and the low-pass filter 301-2. The control frequency Δ ί for controlling the frequency of the frequency variable type local signal generator 113 is selected.

[0088] Since the frequency at which the signal level drops varies with time, the frequency at which the reception level drops is always detected by the level determination unit 303, and the frequency at which the reception level drops is detected by the bandpass filter 301-. By selecting the control frequency Δf in the frequency selection unit 304 so as to coincide with the suppression band of the first and low-pass filters 301-2, it is possible to mitigate the deterioration in reception performance.

The baseband signal is output to the FFT unit 111 via the AGC 302-1 and AGC 302-2, the AZD conversion unit 110-1 and the AZD conversion unit 110-2.

[0091] Then, the FFT unit 111 converts the I and Q baseband signals into a signal in the time domain force frequency domain, and outputs the signal in the frequency domain to the decoding unit 114.

Thereafter, as in Embodiment 1, the decoding unit 114 selects the subcarrier number to which the information data is assigned based on the information regarding the control frequency Δί output from the frequency selection unit 304, and performs OFDM. Decryption is performed. The obtained received data is output to the later stage.

[0093] As described above, according to the present embodiment, by using "OFDM signal subcarrier offset demodulation", the subcarrier with the minimum received signal strength after fast Fourier transform is detected, and the frequency variable type is detected. By controlling the frequency of the local signal oscillator 113, the carrier having the lowest reception level is shifted to the suppression band of the band limiting filter, and OFDM decoding is performed. As a result, the carrier with the lowest reception level is suppressed by the band limiting filter, and the carrier with the higher reception level is used for decoding, so that the degradation in reception performance can be reduced. [0094] (Embodiment 4)

The feature of Embodiment 4 of the present invention is that the frequency of the undesired signal is shifted to the suppression band of the band suppression filter.

FIG. 14 is a block diagram showing the configuration of the receiving apparatus according to Embodiment 4 of the present invention.

In the receiving apparatus of the present embodiment shown in FIG. 14, the same reference numerals as those in FIG. FIG. 14 shows a receiving apparatus that performs undersampling. Compared to FIG. 2, the bandpass filter 105, AGC 106, AZD conversion unit 110-1, 80 conversion unit 110-2, and frequency selection unit 112 are replaced with AGC402. In addition, the band pass filter 403, the AZD conversion unit 404, and the frequency selection unit 405 are provided, and the band suppression filter 401 is added.

[0096] The band suppression filter 401 suppresses a narrowband undesired signal. The IF signal after passing through the band suppression filter 401 is output to the AGC 402.

AGC 402 converts the level of the IF signal to an optimum level in AZD conversion section 404, and outputs the level-converted IF signal to bandpass filter 403.

The bandpass filter 403 removes unnecessary components from the IF signal and outputs the obtained IF signal to the AZD conversion unit 404.

[0099] The AZD conversion unit 404 performs undersampling on the IF signal. Undersampling is performed using a frequency lower than the frequency of the IF signal. For this reason, the aliasing component of the desired signal and the aliasing component of the undesired signal included in the IF signal may overlap, and the desired signal may not be reproduced. This will be specifically described below with reference to FIG. In FIG. 15, the horizontal axis represents frequency and the vertical axis represents signal level. FIG. 15A shows the frequency characteristics of the desired signal and undesired signal in the radio frequency band, and FIG. 15B shows the frequency characteristics of the desired signal and undesired signal after undersampling. As shown in Fig. 15B, it can be seen that the undesired signal may be superimposed on the desired signal after undersampling. For this reason, it is effective to exclude the undesired signal by band limiting by the band suppression filter 401 before the undersampling is performed.

[0100] Frequency selection section 405 is measured by a band suppression filter characteristic measurement section (not shown). Based on the characteristics of the band suppression filter 401, the control frequency Δ ί that controls the frequency of the frequency variable local signal oscillator 113 is selected so that the undesired signal is shifted to the suppression band of the filter. Thereby, the frequency of the undesired signal is shifted to the suppression band of the band suppression filter 401, and the undesired signal can be efficiently suppressed.

Then, frequency selection section 405 outputs a control signal for shifting the frequency by Δί to frequency variable local signal oscillator 113 and also decodes the information for control frequency Δf. Output to.

[0102] Next, a reception operation by the receiving apparatus 100 configured as described above will be described.

[0103] The OFDM signal is output to low noise amplification section 103 via antenna 101 and antenna sharing section 102. Then, the received signal is amplified by low noise amplification section 103 and output to frequency conversion section 104.

The amplified received signal is multiplied by the local signal output from the frequency variable local signal oscillator 113 by the frequency conversion unit 104 and converted to an IF frequency, and the converted IF signal is converted into the band suppression filter 401. Is output.

FIG. 16 shows the frequency characteristics of the desired signal and the undesired signal output from frequency converter 104 and the frequency characteristics of band suppression filter 401 and bandpass filter 403. FIG. 16 shows that the suppression band of the band suppression filter 401 does not match the frequency of the undesired signal. In general, the band suppression filter 401 is a resonance circuit, and there is a variation in the frequency characteristics in which the band where the amount of attenuation can be taken is narrow, so the frequency of the undesired signal and the suppression band of the band suppression filter 401 are In some cases, there is a case.

At this time, the suppression band of the band suppression filter measured by the filter characteristic measurement unit (not shown) matches the frequency of the undesired signal measured by the undesired signal measurement unit (not shown). The frequency selection unit 405 selects the control frequency Δ ί of the frequency of the local signal output from the variable frequency local signal oscillator 113. As a result, the undesired signal is removed in the previous stage of undersampling, and it is possible to reduce the deterioration of the reception performance in which the desired signal and the undesired signal are not superimposed after undersampling. A control signal for shifting the frequency by Δ ί is output to frequency variable local signal oscillator 113, and information about control frequency Δ ί is output to decoding unit 114.

Then, the IF signal after passing through the filter suppression filter 401 is output to the AZD conversion unit 404 via the band suppression filter 401, AG C402, and bandpass filter 403. Then, the AZD conversion unit 404 performs oversampling on the IF signal, and the quadrature modulator 108 converts it into I and Q baseband signals.

[0109] The I and Q baseband signals pass through the low-pass filters 109-1 and 109-2 and are output to the FFT unit 111, respectively. Then, the FFT unit 111 converts the I and Q baseband signals into a time domain force frequency domain signal and outputs the frequency domain signal to the decoding unit 114.

[0110] Thereafter, as in the first embodiment, the decoding unit 114 selects the subcarrier number to which the information data is assigned based on the information regarding the control frequency Δ ί output from the frequency selection unit 405, and transmits the OFDM Decryption is performed. Then, the received data obtained by the decoding unit 114 is output to a subsequent process.

As described above, according to the present embodiment, the frequency of the frequency variable local signal oscillator 113 is controlled using “OFDM signal subcarrier offset demodulation”, and the frequency of the undesired signal is set to the band. Shift to the suppression band of the suppression filter and perform OFDM decoding. As a result, when there is variation in the frequency characteristics of the band-limiting filter, it is possible to eliminate the undesired signal and perform OFDM decoding without reducing the performance degradation due to the variation in frequency characteristics without the need for a variation correction circuit. It becomes.

[0112] In addition, in FIG. 14, the power described for the receiver using undersampling is not limited to this, and by performing frequency conversion so that the undesired signal matches the suppression band of the band suppression filter, other sampling is performed. The same effect can be obtained when the method is used.

[0113] (Embodiment 5)

A feature of Embodiment 5 of the present invention is that, in a composite receiving apparatus having a function of receiving a modulated signal of another system having a wider signal band than the OFDM signal band, when receiving an OFDM signal, the undesired signal is wideband. In the suppression band of the band limit filter optimal for the signal It is to do.

FIG. 17 is a block diagram showing a configuration of receiving apparatus 500 according to Embodiment 5 of the present invention. The receiving apparatus shown in FIG. 17 is a composite receiving apparatus having a function of receiving a modulated signal (for example, a CDMA signal) of another system having a wider signal band than the OFDM signal band. In the receiving apparatus 500 of the present embodiment in FIG. 17, the same reference numerals as those in FIG. FIG. 17 differs from FIG. 12 in that a low-pass filter 501-1, a low-pass filter 301-1, a low-pass filter 301-1, and a frequency selector 112 are replaced with a low-pass filter 501-1. A configuration is employed in which a filter 501-2 and a frequency selection unit 504 are included, the level determination unit 303 is deleted, and a system selection unit 502 and another system decoding unit 503 are added.

[0115] The low-pass filter 501-1 and the low-pass filter 501-2 perform band limitation on both OFDM signals having different signal bands and modulation signals of other systems. Since receiving apparatus 500 limits the band of both modulated signals having different signal bands, the pass band has a wide signal band and is optimal for modulated signals of other systems.

[0116] The system selection unit 502 uses the FFT unit 111 or the baseband signals I and Q output from the AZD conversion unit 110-1 and the AZD conversion unit 110-2 based on instruction information not shown. Is output to the other system decoding unit 503. The instruction information indicates the modulation method of the signal received by receiving apparatus 500. In the case of an OFDM modulated signal, system selection unit 502 outputs I and Q baseband signals to FFT unit 111, and other systems In the case of the modulated signal of I, the baseband signals of I and Q are output to other system decoding section 503. Further, the system selection unit 502 outputs the instruction information to the frequency selection unit 504.

[0117] Other system decoding section 503 performs a decoding process on the baseband signal using a decoding method applied in the other system, and outputs the received data obtained to the subsequent process.

[0118] Frequency selection section 504 selects control frequency Δ ί of variable frequency local signal oscillator 113 based on the instruction information. Specifically, when the indication information indicates an OFDM modulation system, the frequency selection unit 504 makes the frequency of the undesired signal coincide with the suppression band of the filter characteristic output from the filter characteristic measurement unit (not shown). The control frequency Δ ί of the frequency variable type local signal oscillator 113 is selected. As mentioned above, the low pass type The filter band of the filter 501-1 and the low-pass filter 501-2 has a wide signal band, and is suitable for the modulation signal of other systems. Controls the frequency of the local signal of the variable frequency local signal oscillator 113 Then, the undesired signal can be suppressed while sharing the band limiting filter by shifting the undesired signal to the suppression band of the low-pass filter 501-1 and the low-pass filter 501-2. Is possible. As a result, it is not necessary to prepare a band-limiting filter for each system, which enables downsizing and cost reduction.

[0119] Next, a reception operation by the receiving apparatus 100 configured as described above will be described.

[0120] The OFDM signal is output to the low noise amplifying unit 103 via the antenna 101 and the antenna sharing unit 102. Then, the received signal is amplified by the low noise amplification unit 103 and output to the frequency modulation unit 108.

[0121] The amplified received signal is multiplied by the local signal output from the frequency variable local signal oscillator 113 by the frequency demodulator 108, converted into an I and Q baseband signal, and converted into a converted baseband signal. The signal is output to the low-pass filter 501-1 and the low-pass filter 501-2. At this time, the frequency of the local signal output from the frequency variable local signal oscillator 113 is shifted by the control frequency Δ ί selected by the frequency selection unit 504. As described above, the control frequency Δ ί is selected so that the undesired signal is shifted to the suppression band of the filter characteristic output from the filter characteristic measurement unit (not shown).

Control frequency Δ ί selected by frequency selection section 504 is output to frequency variable local signal oscillator 113 and also output to decoding section 114.

[0123] The baseband signal is output to system selection unit 502 via AGC302-1, AGC302-2, AZD conversion unit 110-1, and AZD conversion unit 110-2.

[0124] Then, the baseband signal is obtained from the instruction information (not shown) by the system selection unit 502.

It is output to the FFT unit 111 or the other system decoding unit 503.

[0125] The baseband signal output to FFT section 111 is converted from a time domain signal to a frequency domain signal, and the frequency domain signal is output to decoding section 114.

[0126] Thereafter, the output from the frequency selection unit 112 is performed by the decoding unit 114 in the same manner as in the first embodiment. Based on the information regarding the control frequency Δf to be transmitted, the subcarrier number to which the information data is assigned is selected, and OFDM decoding is performed. Then, the received data obtained by the decoding unit 114 is output to a subsequent process.

[0127] On the other hand, the baseband signal output to other system decoding section 503 is subjected to the decoding system of the other system, and the obtained received data is output to the subsequent process.

[0128] As described above, according to the present embodiment, by using "OFDM signal subcarrier offset demodulation", when receiving an OFDM signal, the undesired signal is converted into a suppression characteristic of a band-limited filter suitable for other systems. The frequency of the frequency variable local signal oscillator 113 is controlled so as to match, and OFDM decoding is performed. As a result, it is possible to share the band limiting filter with other systems, which enables downsizing and cost reduction.

[0129] Depending on the signal band difference between the OFDM signal and the modulation signal of the other system, the low-pass filter 501-1 and the low-pass filter 501-2 have the OFDM signal power after passing through the latter FFT unit 111. If the frequency is within the decodable frequency range, a frequency change that again shifts the frequency of the OFDM signal is placed downstream of the low-pass filter 501-1 and the low-pass filter 501-2. It may be provided. As a result, the OFDM signal in which the undesired signal is suppressed is shifted again to a decodable frequency range, and as a result, all carriers to which information data is allocated can be used for decoding, and reception performance is improved. Deterioration can be prevented.

[0130] The receiving apparatus according to the first embodiment of the present invention includes a receiving means for receiving a signal including frequency components corresponding to a plurality of carriers to which information data is assigned, and all of the reception signals. Frequency conversion means for shifting the frequency of the frequency component, a filter for suppressing the frequency after frequency shift of some of the frequency components included in the received signal, and the plurality of carriers among the frequency components remaining without being suppressed Decoding means for decoding the frequency component corresponding to the frequency component, and the frequency conversion means matches the frequency of the undesired frequency component whose reception quality does not meet a predetermined standard with the frequency suppressed by the filter. Take the configuration.

[0131] According to this configuration, the frequency shift is performed by shifting the frequencies of all the frequency components included in the signal including the frequency components corresponding to the plurality of carriers to which the information data is assigned. Among the frequency components included in the received signal after the transmission, the frequency of the undesired frequency component whose reception quality does not satisfy a predetermined standard is suppressed by the filter, and the frequency components remaining without being suppressed are applied to a plurality of carriers. In order to decode the corresponding frequency components, even when a filter with a steep suppression characteristic and a variation in frequency characteristic is used, the deterioration of the filter characteristic can be reduced without requiring a circuit for correcting the deterioration of the filter characteristic. The frequency of undesired frequency components can be suppressed, and reception performance can be improved.

[0132] In the reception device according to the second exemplary embodiment of the present invention, in the first aspect, the frequency conversion unit may convert frequency components other than frequency components corresponding to the plurality of carriers to undesired frequency components. The configuration is as follows.

[0133] According to this configuration, since frequency components other than frequency components corresponding to a plurality of carriers to which information data is assigned are set as undesired frequency components, only frequencies other than frequency components corresponding to a plurality of carriers are suppressed. Thus, the frequency components corresponding to a plurality of carriers are decoded without being suppressed, and reception performance can be improved.

[0134] In the receiver according to the third embodiment of the present invention, in the first aspect, the frequency conversion means measures a signal power to noise power ratio for each frequency component included in the received signal. And a noise measurement unit, wherein a frequency component having a measured signal power to noise power ratio equal to or greater than a predetermined threshold is used as an undesired frequency component.

[0135] According to this configuration, the noise level included in the received signal is estimated, and the frequency component corresponding to the noise whose estimated level is equal to or greater than the predetermined threshold is set as the undesired frequency component. Even in an environment where the frequency fluctuates, it is always possible to improve the reception performance by suppressing the frequency component corresponding to the noise whose estimated level is equal to or higher than a predetermined threshold and suppressing it.

[0136] In the reception apparatus according to the fourth exemplary embodiment of the present invention, in the first aspect, the frequency conversion means measures the level for each frequency component corresponding to the plurality of carriers. The frequency component with the lowest measured level is the undesired frequency component.

[0137] According to this configuration, the level of each frequency component corresponding to a plurality of carriers to which information data is assigned is measured, and the frequency component with the smallest measured level is determined as an undesired frequency. Because it is a component, among the frequency components corresponding to multiple carriers, the frequency component with the highest level is not suppressed, and only the frequency component with the lowest reception level is suppressed. Can be reduced.

[0138] In the reception apparatus according to the fifth exemplary embodiment of the present invention, in the first aspect, the frequency conversion means uses the decoding means to determine the frequencies of all frequency components corresponding to the plurality of carriers. A configuration is adopted that shifts to a frequency range that can be decoded.

[0139] According to this configuration, the frequencies of all the frequency components corresponding to the plurality of carriers to which the information data is allocated are shifted to the range of frequencies that can be decoded. All frequency components corresponding to the carrier can be used for decoding.

[0140] In the receiver according to the sixth embodiment of the present invention, in the first aspect, the decoding means corresponds to the plurality of carriers based on a frequency shift amount by the frequency converting means. Select a frequency component to be decoded and decode the selected frequency component

[0141] According to this configuration, since the frequency components corresponding to the plurality of carriers to which the information data is assigned are selected based on the frequency shift amount, and the selected frequency components are decoded, the information data All frequency components corresponding to a plurality of carriers to which are assigned are appropriately used and decoded.

[0142] In the reception device according to the seventh exemplary embodiment of the present invention, in the first aspect, the decoding means has a frequency component frequency that remains without being suppressed within a frequency range that can be decoded. A re-frequency conversion unit that shifts again, and adopts a configuration for decoding frequency components corresponding to the plurality of carriers after the re-frequency shift.

[0143] According to this configuration, the frequency of the frequency component that remains without being suppressed is shifted again to a decodable frequency range, and it corresponds to a plurality of carriers to which information data after re-frequency shift is assigned. Even when a filter with a wider pass band than the signal bands of multiple carriers to which information data is assigned is used, the frequency of the undesired frequency component is suppressed and the information data is assigned. All the frequency components of multiple received carriers can be used for decoding, and deterioration of reception performance can be prevented. it can. In addition, the signal band is wider than the signal bands of multiple carriers to which information data is assigned, and a composite receiver having a function of receiving a modulated signal of another system can share a filter. As a result, downsizing and low cost can be achieved.

[0144] The reception method according to the eighth embodiment of the present invention includes a reception step of receiving a signal including frequency components corresponding to a plurality of carriers to which information data is allocated, and all of the reception signals. A frequency conversion step for shifting the frequency of the frequency component, a suppression step for suppressing the frequency after the frequency shift of some of the frequency components included in the received signal, and the plurality of frequency components among the frequency components remaining without being suppressed. A decoding step of decoding a frequency component corresponding to a carrier, wherein the frequency conversion step matches a frequency of an undesired frequency component whose reception quality does not satisfy a predetermined standard with a frequency suppressed by the filter. The process to make is taken.

[0145] According to this method, the frequencies of all frequency components included in a signal including frequency components corresponding to a plurality of carriers to which information data is assigned are shifted and included in the received signal after the frequency shift. Of the frequency components, the frequency of undesired frequency components whose received quality does not meet a predetermined standard is suppressed by the filter, and the frequency components corresponding to multiple carriers are decoded from the remaining frequency components without being suppressed. Even when a filter with a steep suppression characteristic and a variation in frequency characteristics is used, the frequency of the undesired frequency component can be reduced by reducing the deterioration of the filter characteristics without requiring a circuit for correcting the deterioration of the filter characteristics. It is possible to suppress it and improve the reception performance.

[0146] Based on Japanese Patent Application 2005-203340 filed on July 12, 2005. This content [all included here.

Industrial applicability

[0147] The receiving apparatus and the receiving method of the present invention can suppress undesired signals even in the case of using a band limiting filter in which the suppression characteristics are not steep and the frequency characteristics vary in multicarrier communication. For example, it is useful for a receiving apparatus and a receiving method in a system to which multicarrier communication is applied.

Claims

The scope of the claims

Receiving means for receiving a signal including frequency components corresponding to a plurality of carriers to which information data is assigned;

A frequency converting means for shifting the frequencies of all frequency components included in the received signal; a finerator for suppressing the frequency after frequency shifting of some frequency components included in the received signal;

Decoding means for decoding frequency components corresponding to the plurality of carriers among frequency components remaining without being suppressed,

The frequency conversion means includes

A receiving apparatus that matches a frequency of an undesired frequency component whose reception quality does not satisfy a predetermined standard with a frequency that is suppressed by the filter.

The frequency conversion means includes

The receiving apparatus according to claim 1, wherein frequency components other than frequency components corresponding to the plurality of carriers are set as undesired frequency components.

The frequency conversion means includes

A noise measurement unit that measures the signal power to noise power ratio for each frequency component included in the received signal,

2. The receiving apparatus according to claim 1, wherein a frequency component having a measured signal power to noise power ratio equal to or greater than a predetermined threshold is set as an undesired frequency component.

The frequency conversion means includes

A level measuring unit that measures the level of each frequency component corresponding to the plurality of carriers,

The receiving apparatus according to claim 1, wherein the frequency component having the minimum measured level is set as an undesired frequency component.

The frequency conversion means includes

2. The receiving apparatus according to claim 1, wherein frequencies of all frequency components corresponding to the plurality of carriers are shifted to a frequency range that can be decoded by the decoding unit. [6] The decoding means includes:

2. The receiving device according to claim 1, wherein a frequency component corresponding to the plurality of carriers is selected based on a frequency shift amount by the frequency converting means, and the selected frequency component is decoded.

[7] The decoding means includes

A re-frequency converter that re-shifts the frequency of the frequency component that remains without being suppressed to a decodable frequency range;

2. The receiving apparatus according to claim 1, wherein frequency components corresponding to the plurality of carriers after re-frequency shifting are decoded.

[8] A reception step of receiving a signal including frequency components corresponding to a plurality of carriers to which information data is assigned;

A frequency conversion step for shifting the frequencies of all frequency components included in the received signal, a suppression step for suppressing the frequency after frequency shift of some frequency components included in the received signal,

Decoding a frequency component corresponding to the plurality of carriers among frequency components remaining without being suppressed, and

The frequency conversion step includes

A receiving method in which a frequency of an undesired frequency component whose reception quality does not satisfy a predetermined standard is matched with a frequency to be suppressed by the filter.