Wireless communication apparatus

Abstract

A wireless communication apparatus utilizing an orthogonal frequency division multiplexing communication method includes an antenna transmitting and receives a radio-frequency signal; a receiver frequency converter frequency-converting the radio-frequency signal into a baseband signal in accordance with a low-intermediate frequency method; an analog-to-digital converter converting the baseband signal into a digital signal; an orthogonal frequency division multiplexing demodulator acquiring a plurality of subcarriers in a frequency domain; a data reproduction unit reproducing data; a transmission data generator generating transmission data; an orthogonal frequency division multiplexing modulator performing orthogonal frequency division multiplexing modulation of the plurality of subcarriers; a digital-to-analog converter converting the digital orthogonal frequency division multiplexing signal into an analog signal; and a transmitter frequency converter converting the analog transmission baseband signal into a transmission radio-frequency signal in accordance with a zero-intermediate frequency method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of an MB-OFDM transceiver according to an embodiment of the present invention;

FIG. 2 shows band regions in which a signal of a different system is detectable and band regions in which a signal of a different system is not detectable in a group A shown in FIG. 11 when a receiver adopts a Low-IF method;

FIG. 3 shows band regions in which the noise floor level should be reduced in a UWB transmitter;

FIG. 4 shows blocks for combining frequencies for frequency hopping in the receiver adopting the Low-If method;

FIG. 5 shows spurious components caused by a harmonic wave of 528 MHz in the blocks for combining frequencies shown in FIG. 4;

FIG. 6 shows an example of a configuration of blocks for combining frequencies for frequency hopping used in a Zero-IF method (a case of a three-band mode of the group A);

FIG. 7 shows a result in which a composite wave obtained by combining a fundamental wave, a third harmonic wave, and a fifth harmonic wave is shifted by 45 degrees and by 90 degrees, and weighting is assigned to the composite waves at a ratio of 1:√2:1 when a digital sine wave is used for a Low-IF signal;

FIGS. 8A and 8B show images of output spectra of the transmitter having the Zero-IF configuration using a digital sine wave;

FIGS. 9A to 9C schematically show a communication operation of subband avoidance;

FIGS. 10A to 10C schematically show a communication operation of subcarrier avoidance;

FIG. 11 shows an example of frequency allocation defined by an MB-OFDM communication system;

FIG. 12 shows a state in which data transmission is performed while frequency hopping is performed for an OFDM symbol in a time axis in the MB-OFDM method;

FIG. 13 shows a sate in which a notch is provided in a frequency band region in which a narrow-band signal is detected in an OFDM symbol;

FIG. 14 shows an example of a configuration of a receiver used in the MB-OFDM system;

FIG. 15 shows a state in which self-mixing of a local signal is generated in a receiver utilizing the Zero-IF method;

FIG. 16 is an illustration for explaining a DC offset generated by self-mixing;

FIG. 17 shows a state in which interference to a baseband desired signal is generated by self-mixing;

FIG. 18 shows an example of a circuit configuration in which capacitors are inserted in series with each other between stages of mixer outputs in order to remove a DC offset;

FIGS. 19A to 19C are illustrations for explaining generation of a carrier leakage in an MOD output;

FIG. 20 is an illustration for explaining generation of a carrier leakage in an MOD output; and

FIGS. 21A to 21C show states in which an image spurious component is generated due to IQ imbalance when orthogonal modulation is performed in the transmitter having the Low-IF configuration.

Claims

1. A wireless communication apparatus utilizing an orthogonal frequency division multiplexing communication method, comprising: an antenna that transmits and receives a radio-frequency signal;a receiver frequency converter that frequency-converts the received radio-frequency signal into a baseband signal in accordance with a low-intermediate frequency method using a local signal obtained by adding a predetermined low intermediate frequency to a center frequency of the radio-frequency signal;an analog-to-digital converter that converts the baseband signal into a digital signal;an orthogonal frequency division multiplexing demodulator that acquires a plurality of subcarriers in a frequency domain by performing orthogonal frequency division multiplexing demodulation of the digitized signal;a data reproduction unit that reproduces data from each of the plurality of subcarriers;a transmission data generator that generates transmission data by allocating to the plurality of subcarriers data that is requested from an upper layer to be transmitted;an orthogonal frequency division multiplexing modulator that performs orthogonal frequency division multiplexing modulation of the plurality of subcarriers in the frequency domain;a digital-to-analog converter that converts the digital orthogonal frequency division multiplexing signal into an analog signal at a resolution with a signal-to-noise ratio of a predetermined value or less; anda transmitter frequency converter that converts the analog transmission baseband signal into a transmission radio-frequency signal in accordance with a zero-intermediate frequency method using a local signal having a frequency the same as the frequency of the radio-frequency signal.

2. The wireless communication apparatus according to claim 1, wherein ultra-wideband communication using a wide band is performed.

3. The wireless communication apparatus according to claim 1, wherein multiband communication is performed in which frequency hopping is performed for each orthogonal frequency division multiplexing symbol between a plurality of subbands obtained by dividing a used frequency band.

4. The wireless communication apparatus according to claim 3, wherein the receiver frequency converter uses a value corresponding to half the bandwidth of each of the plurality of subbands as the low intermediate frequency.

5. The wireless communication apparatus according to claim 3, further comprising: an interference detector that detects interference with a communication system in accordance with signal detection after the orthogonal frequency division multiplexing demodulation is performed by the orthogonal frequency division multiplexing demodulator; andan interference avoidance unit that avoids the interference in a frequency band region in which a signal of the communication system is detected.

6. The wireless communication apparatus according to claim 5, wherein when detecting interference with the communication system in a frequency band region not it the vicinity of the local signal of the receiver, the interference avoidance unit avoids using a corresponding subcarrier or a corresponding subband.

7. The wireless communication apparatus according to claim 5, wherein when detecting interference with the communication system in a frequency band region in the vicinity of the local signal of the receiver, the interference avoidance unit avoids using a corresponding subband.

8. The wireless communication apparatus according to claim 3, further comprising: a multiband generator that generates a local signal for each of the plurality of subbands by repeatedly performing frequency division on a single frequency output from an oscillator and by mixing the frequency-divided outputs,wherein the multiband generator uses a digital sine wave as a frequency signal having a value corresponding to half the bandwidth of each of the plurality of subbands when the local signal for transmission is generated.

9. A multiband orthogonal frequency division multiplexing wireless communication apparatus that performs multiband communication in which frequency hopping is performed for each orthogonal frequency division multiplexing symbol using a plurality of subbands obtained by dividing a used frequency band, comprising: a receiver that sets a dead band region in the vicinity of a boundary between the plurality of subbands and that performs a reception operation; anda transmitter that reduces the noise floor in the dead band region to a predetermined level or less and that performs a transmission operation.

10. The wireless communication apparatus according to claim 9, wherein the receiver is configured based on a low-intermediate frequency method in which frequency conversion is performed using a local signal obtained by adding a low intermediate frequency having a value corresponding to half the bandwidth of each of the plurality of subbands to a center frequency of a radio-frequency signal.

11. The wireless communication apparatus according to claim 9, wherein the transmitter is configured based on a zero-intermediate frequency method in which frequency conversion is performed using a local signal having a frequency the same as the frequency of a radio-frequency signal and converts a digital transmission signal into an analog signal at a resolution with a signal-to-noise ratio of a predetermined value or less.

12. The wireless communication apparatus according to claim 9, wherein ultra-wideband communication using a wide band is performed.

13. The wireless communication apparatus according to claim 9, further comprising: an interference detector that is provided in the receiver and that detects interference with a communication system in accordance with signal detection after orthogonal frequency division multiplexing demodulation is performed; andan interference avoidance unit that is provided in the transmitter and that performs the transmission operation while avoiding the interference in a frequency band region in which a signal of the communication system is detected.

14. The wireless communication apparatus according to claim 9, wherein when detecting interference with the communication system in a frequency band region not in the vicinity of a local signal of the receiver, the interference avoidance unit avoids using a corresponding subcarrier or a corresponding subband.

15. The wireless communication apparatus according to claim 9, wherein when detecting interference with the communication system in a frequency band region in the vicinity of a local signal of the receiver, the interference avoidance unit avoids using a corresponding subband.

16. The wireless communication apparatus according to claim 9, further comprising: a multiband generator that generates a local signal for each of the plurality of subbands by repeatedly performing frequency division on a single frequency output from an oscillator and by mixing the frequency-divided outputs,wherein the multiband generator uses a digital sine wave as a frequency signal having a value corresponding to half the bandwidth of each of the plurality of subbands when a local signal for transmission is generated.

17. The wireless communication apparatus according to claim 1 or 9, further comprising a bandpass filter for restricting frequencies other than frequency regions of the plurality of subbands, the bandpass filter being arranged upstream of an antenna terminal.