JP2008124915A - Radio communications system and radio communications device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superior radio communications system and a radio communications device which are robust, with respect to multipath interference and disturbance waves from other communications systems. <P>SOLUTION: A mobile terminal device transmits both modulated reflected wave signals generated in the positive and negative directions from the frequency of an unmodulated carrier, when transmission data are primarily modulated with a subcarrier frequency f<SB>s</SB>and the primarily modulated signal is multiplied by the input of unmodulated carrier f<SB>0</SB>. A non-contact transmission device side performs adaptive reception processing, according to reception qualities of the modulated reflected wave signals, for example, by selectively receiving a modulated reflected wave signal, having a better reception quality between the two modulated reflected wave signals or performing ratio combining processing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication system and a wireless communication apparatus that realize a communication operation with low power consumption between devices in a relatively short distance, and in particular, transmission of an unmodulated carrier from a reflected wave reader side and a reflector side The present invention relates to a radio communication system and a radio communication apparatus for performing data communication by a reflected wave transmission method using absorption and reflection of a received radio wave based on an antenna termination operation.

  More particularly, the present invention relates to a wireless communication system and a wireless communication apparatus that removes the influence of DC offset and transmitter noise on the reflected wave reader side that reads a modulated reflected wave signal, and improves reception sensitivity. The present invention relates to a radio communication system and a radio communication apparatus for realizing high-speed transmission by a modulated reflected wave signal obtained by first modulating transmission data on a reflector side and further multiplying the primary modulated signal by an input of an unmodulated carrier.

  Wireless communication technology is expected as a system for releasing users from cable wiring in a wired communication system, and is rapidly spreading. Examples of the wireless communication include a mobile phone (PDC: Personal Digital Cellular), PHS (Personal Handyphone System), a wireless LAN (Local Area Network) represented by IEEE 802.11, Bluetooth communication, and the like.

  Recently, a data communication system using a non-contact communication method used for RFID (Radio Frequency IDentifier) has been proposed. Non-contact communication methods include an electrostatic coupling method, an electromagnetic induction method, a radio wave communication method, and the like. Among them, the radio wave communication type RFID system includes a reflector that transmits data by a reflected wave obtained by modulating a received unmodulated carrier, and a reflected wave reader that reads data from a modulated reflected wave signal from the reflector. It is configured to perform reflected wave transmission, also called “backscatter”.

  When a non-modulated carrier is sent from the reflected wave reader, the reflector modulates the reflected wave and superimposes data based on an antenna load impedance switching operation or the like. That is, since no carrier generation source is required on the reflector side, the data transmission operation is driven with low consumption. On the reflected wave reader side, such modulated reflected waves can be received and demodulated and decoded to obtain transmission data.

  In addition, an antenna switch for changing the load impedance of the antenna in the reflector can be incorporated in a circuit module for transmission / reception processing and configured by a CMOS transistor. However, it is separated from the circuit module, and gallium arsenide (GaAs) is separated. By using this IC (Integrated Circuit), it is possible to perform a high-speed switching operation with low power consumption. In the latter case, the data transmission rate by reflected wave modulation is improved and the power consumption is suppressed to several tens of μW or less. Therefore, considering that the wireless LAN consumes power of several hundred mW to several W during communication, it can be said that the reflected wave communication has an overwhelming performance difference compared to the average power consumption of a general wireless LAN ( For example, see Patent Document 1).

  Since a terminal equipped with a reflector only performs an operation of reflecting a received radio wave, it is not regarded as a radio station, and is treated as being out of the scope of legal regulations imposed on radio wave communication. Further, other non-contact communication systems such as the electromagnetic induction system use a frequency of several MHz to several hundred MHz (for example, 13.65 MHz), whereas the reflected wave communication system uses, for example, 2 called ISM (Industry Science and Medical Band). High-speed data transmission using a high band of 4 GHz band can be realized.

  For example, a reflector is incorporated in a mobile terminal device such as a digital camera, a video camera, a mobile phone, a portable information terminal, a portable music player, and the like to minimize power consumption, and a TV, monitor, printer, PC, VTR. A reflected wave reader is incorporated in a host device such as a stationary home appliance such as a DVD player. Then, image data taken with a camera-equipped mobile phone or digital camera can be uploaded to a PC via a reflected wave transmission path, and image data can be stored, displayed, and printed out.

  In the configuration of a basic reflected wave transmission system, the unmodulated carrier transmitted from the reflected wave reader and the center frequency of the modulated reflected wave transmitted from the reflector are usually the same. In such a case, on the reflected wave reader side, transmission and reception are performed at the same frequency. Therefore, the reception unit is easily affected by DC offset and transmitter noise, and it is difficult to extend the transmission distance. There is. In addition, considering the simplification of the circuit on the reflector side, a modulation scheme with a low modulation rate such as ASK (Amplitude Shift Keying) or PSK (Phase Shift Keying) is used, and it is difficult to increase the speed.

  For example, a modulation backscatter system has been proposed in which QPSK (Quadrature Phase Shift Keying) modulation is performed on a subcarrier as primary modulation, and then a reflected wave is modulated by ASK or PSK as secondary modulation (for example, (See Patent Document 2). In such a case, a weak modulated wave of the reflected wave appears at a position corresponding to the subcarrier frequency in both positive and negative directions centered on the frequency of the unmodulated carrier from the reflected wave reader. Only one modulated wave is received at. The modulated signal from the reflector is already attenuated due to reflection. Furthermore, the transmission power of the reflected wave signal is dispersed in the positive and negative directions of the center frequency. For this reason, if there is multipath interference or interference with interference waves from other communication systems, reception becomes difficult because the reception level is low.

FIG. 4 shows a configuration example of a communication system in which the reception frequency f _o is shifted in the positive or negative direction by a predetermined center frequency f _s and a reflected wave is sent back on the reflector side. The illustrated communication system includes a reflector 100 and a reflected wave reader 110, and performs data transmission from the reflector 100 to the reflected wave reader 110 by a reflected wave transmission method. For example, an application unit 105 such as a digital camera is connected to the reflector 100, and an application unit 119 such as a printer is connected to the reflected wave reader 110.

The reflected wave reader 110 includes an antenna 111, a circulator 112 that separates a transmission wave and a reception wave, a reception unit 114, a local oscillator 115 of the reception unit 114, a transmission unit 116, and a local oscillator 117 of the transmission unit 116. The baseband processing unit 118 is provided. In the illustrated example, both the reception unit 114 and the transmission unit 116 use the direct conversion method. Transmission of unmodulated carrier to the reflector 100, by turning on the transmission unit 116 from the baseband processing unit is performed by transmitting a frequency f _o of local oscillator 117 from the antenna 111 via the circulator 112.

The unmodulated carrier f _o transmitted from the reflected wave reader 110 reaches the reflector 100. The reflector 100 includes an antenna 101, a backscatter modulator 102, a subcarrier QPSK modulator 103, and a subcarrier oscillator 104. The subcarrier QPSK modulator 103 performs QPSK modulation at the subcarrier frequency f _s . Data subjected to QPSK modulation is supplied from the application unit 105 as transmission data (TXDATA) and transmission clock (TXCLK). In general, a 90 ° phase shifter is required for QPSK modulation, but if it is performed by a digital circuit, it can be easily generated from a clock four times f _s . Alternatively, an analog delay line can be used. The QPSK modulated wave having the center frequency f _s thus generated is ASK or PSK modulated by the backscatter modulator 102. Backscatter modulation can be easily configured with a diode, a GaAs switch, or the like. In this way, the reflector 100, the center frequency f _s the transmission data subjected to primary modulation by QPSK, the the QPSK modulated signal and inputs the multiplied unmodulated carrier frequency f _o, or the frequency f _o + f _s A modulated wave of a reflected wave in which any one of f _o −f _s is suppressed is transmitted. In the illustrated example, it is assumed to use a modulated wave f _o + f _s.

In the reflection wave reader 110, f _o + f _s reflected wave transmitted QPSK modulated wave signal is received by the receiver 114 via the antenna 111 and the circulator 112. In the reception unit 114, direct conversion reception is performed at the frequency f _o + f _s of the local oscillator 115, and the QPSK modulated wave is converted into a baseband signal of each axis of I and Q and sent to the baseband processing unit 118. The baseband processing unit 118 performs QPSK demodulation processing (carrier synchronization and symbol synchronization), generates reception data RXDATA and a reception clock RXCLK, and passes them to the application unit 119.

FIG. 5 shows a spectrum of reflected waves in the communication system shown in FIG. The modulation method for reflected wave transmission is ASK. Reference numeral 200 in the figure is an unmodulated carrier of frequency f _o transmitted from the reflected wave reader 110. Further, reference numeral 201 is wherein the QPSK modulation of a center frequency f _o + f _s, the reference numeral 202 is the QPSK modulated wave of the center frequency f _o -f _s. Thus, the reflected wave is generated by being divided into two frequency bands.

Here, if the multipath interference and other systems, the interference wave as shown by reference numeral 203 arrives, can not receive a reflected wave reader 110 is receiving only QPSK modulated signal f _o + f _s It will be.

JP 2005-64822 A Japanese Patent Laid-Open No. 10-209914

  An object of the present invention is to suitably perform data communication by transmission of an unmodulated carrier from the reflected wave reader side and a reflected wave transmission method using absorption and reflection of received radio waves based on an antenna termination operation on the reflector side. It is an object of the present invention to provide an excellent wireless communication system and wireless communication apparatus.

  A further object of the present invention is to provide an excellent radio communication system and radio communication apparatus capable of removing the influence of DC offset and transmitter noise on the side of a reflected wave reader that reads a modulated reflected wave signal and improving reception sensitivity. Is to provide.

  A further object of the present invention is to provide an excellent radio that can realize high-speed transmission by a modulated reflected wave signal obtained by first modulating transmission data on the reflector side and further multiplying this primary modulated signal by an input of an unmodulated carrier. A communication system and a wireless communication device are provided.

The present invention has been made in consideration of the above problems, and a reflector that receives an unmodulated carrier and transmits a modulated reflected wave signal, and a reflected wave that transmits an unmodulated carrier and receives a modulated reflected wave signal. A wireless communication system comprising a reader,
In the reflector side, the transmission data subjected to primary modulation by the subcarrier frequency f _s, further positive and negative about the frequency of the unmodulated carrier when entering and multiplying the unmodulated carrier f _o the primary modulation signal Transmit each modulated reflected wave signal generated at each of the bidirectional frequencies,
In the reflected wave reader, adaptive reception processing is performed according to the reception quality of each modulated reflected wave signal.
This is a wireless communication system.

  However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not (hereinafter the same).

  The present invention is a reflected wave reader equipped with a reflector that receives a non-modulated carrier and transmits a modulated reflected wave on which data is superimposed, and a reflected wave reader that reads data from the modulated reflected wave. The present invention relates to a wireless communication system using radio wave reflection technology. According to a communication system using reflected wave transmission, since no carrier generation source is required on the reflector side, data transmission can be performed while dramatically reducing power consumption, compared to a general wireless LAN. It is an overwhelming performance difference.

  In a wireless communication system to which reflected wave transmission is applied, a modulation method having a low modulation rate such as ASK or PSK is used in consideration of simplification of circuits on the reflector side where the reflector is mounted and low power consumption. It is difficult to make it.

  On the other hand, there is a reflected wave transmission method using subcarrier modulation in which a QPSK modulation is performed with a subcarrier as a primary modulation on the reflector side, and then a reflected wave is subjected to a modulation process with ASK or PSK as a secondary modulation. Conceivable.

  In such a case, a modulated reflected wave appears at a position corresponding to the subcarrier frequency in both positive and negative directions centering on the frequency of the unmodulated carrier. Here, since the modulated signal from the reflector has already attenuated due to reflection and is further dispersed in the positive and negative directions of the center frequency, each reflected wave signal is weak. For this reason, when one reflected reflected wave signal is received by the reflected wave reader, if there is multipath interference or interference with interference waves from other communication systems, reception becomes difficult because the reception level is low.

  Therefore, in the wireless communication system according to the present invention, the reflector transmits both the modulated reflected wave signal generated in both the positive and negative directions centered on the frequency of the unmodulated carrier, and the reflected wave reader side has two modulated reflected waves. An adaptive reception process is performed according to the reception quality of each modulated reflected wave signal, such as selectively receiving a wave signal having a better reception quality or performing a ratio combining process. As a result, it is possible to avoid the influence of multipath interference and interference with interference waves from other communication systems.

Here, in the case where the reflected wave reader side selectively receives one of the two modulated reflected wave signals, which has the better reception quality or the reception quality is stable, the received modulated reflected wave signal is orthogonally modulated. Later, it is necessary to exchange the I-axis signal and the Q-axis signal in accordance with switching of the reception frequency. Because, in the modulation wave and the negative side modulation wave on the positive side with respect to the frequency f _o of the unmodulated carrier, because the rotational direction of the different phases.

  Alternatively, the reflected wave reader is independently provided with each receiving unit that performs quadrature modulation at each of the reception frequencies in the positive direction and the negative direction at the center of the frequency of the unmodulated carrier, and one of the receptions is performed according to switching of the reception frequency. It can also be configured to distribute the received signal to the unit.

  In order to realize a mechanism for adaptively performing reception processing according to reception quality on the reflected wave reader side, for example, a preamble detection section of a frame transmitted from the reflector to the reflected wave reader has a frequency of an unmodulated carrier. The first half of a preamble detection interval for sending a preamble pattern at either the positive or negative frequency in the center of the first half, the second half of the preamble detection interval for sending a preamble pattern at the other frequency, and the first half and the second half A frequency switching section is included in between.

  In such a case, the reflected wave reader receives the first half at one reception frequency, checks the reception input level or preamble pattern of the preamble, and determines the other half in the frequency switching interval according to the check result. By switching the reception frequency, receiving the latter half at the other reception frequency and checking the reception input level or preamble pattern of the preamble, it is possible to select a reception frequency with good or stable reception quality. .

  According to the present invention, there is provided an excellent wireless communication system and wireless communication apparatus capable of removing the influence of a DC offset and transmitter noise on the reflected wave reader side that reads a modulated reflected wave signal and improving reception sensitivity. Can be provided.

  Further, according to the present invention, it is possible to realize high-speed transmission with a modulated reflected wave signal obtained by first-modulating transmission data on the reflector side and further multiplying this primary modulated signal by an input of an unmodulated carrier. A wireless communication system and a wireless communication device can be provided.

  In addition, according to the present invention, transmission data is first-order modulated on the reflector side, and when this primary modulation signal is multiplied by the input of the unmodulated carrier, plus and minus bidirectional with the frequency of the unmodulated carrier as the center. By using the modulated reflected wave signal generated in the above, it is possible to provide an excellent wireless communication system and wireless communication apparatus that are robust against multipath interference and interference waves from other communication systems.

  In the wireless communication system according to the present invention, the reflector transmits the modulated reflected wave signal generated in both positive and negative directions around the frequency of the unmodulated carrier as it is. On the other hand, on the reflected wave reader side, multipath interference and other factors can be obtained by performing adaptive reception processing such as selective reception or ratio combining processing of the two modulated reflected wave signals. It is possible to avoid the influence of interference with interference waves from the communication system.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

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

  FIG. 1 shows a configuration of a communication system according to an embodiment of the present invention. In the illustrated communication system, reflected wave transmission is performed between a mobile device equipped with the reflector 100 and the reflected wave reader 110. In the present embodiment, it is assumed that reflected wave transmission using subcarrier modulation is performed.

  For example, an application unit 105 such as a digital camera is connected to the reflector 100, and an application unit 119 such as a printer is connected to the reflected wave reader 110.

  The reflected wave reader 110 includes an antenna 111, a circulator 112 that separates a transmission wave and a reception wave, a reception unit 114, an IQ switcher (SWAP) 302, a local oscillator 301 of the reception unit 114, and a transmission unit 116. The local oscillator 117 of the transmission unit 116 and the baseband processing unit 118 are provided. In the illustrated example, both the reception unit 114 and the transmission unit 116 use the direct conversion method.

Transmission of unmodulated carrier to the reflector 100, by turning on the transmission unit 116 from the baseband processing unit is performed by transmitting a frequency f _o of local oscillator 117 from the antenna 111 via the circulator 112. The unmodulated carrier f _o transmitted from the reflected wave reader 110 reaches the reflector 100.

The reflector 100 includes an antenna 101, a backscatter modulator 102, a subcarrier QPSK modulator 103, and a subcarrier oscillator 104. The subcarrier QPSK modulator 103 performs QPSK modulation at the subcarrier frequency f _s . Data to be subjected to QPSK modulation is received from the application unit 105 as transmission data (TXDATA) and transmission clock (TXCLK).

The generated subcarrier QPSK modulated wave having the center frequency f _s is ASK or PSK modulated by the backscatter modulator 102. Backscatter modulation can be easily configured with a diode, a GaAs switch, or the like. In this way, the reflector 100, the center frequency f _s the transmission data subjected to primary modulation by QPSK, the this sub-carrier QPSK modulated signal to input multiplied unmodulated carrier frequency f _o, the frequency f _o + f _A modulated reflected wave signal composed of both _s and f _o −f _s is transmitted.

In the reflection wave reader 110, f _o + f _s and f _o -f _s reflected wave transmitted QPSK modulated wave signal is received by the receiver 114 via the antenna 111 and the circulator 112. The local oscillator 301 is a synthesizer system that can switch the frequency between f _o + f _s and f _o −f _s, and the frequency switching is controlled by the baseband control unit 118. In the receiving unit 114, respectively direct conversion receiver by frequency f _o + f _s and f _o -f _s in accordance with the frequency switching of the local oscillator 301 is performed, QPSK modulated wave into a baseband signal of each axis of the I and Q It is converted and sent to the baseband processing unit 118.

However, the IQ switcher 302 switches the I signal and the Q signal output from the receiving unit 114 when switching the reception frequency between f _o + f _s and f _o −f _s . This is the modulated wave and the negative side modulation wave on the positive side with respect to the frequency f _o of the unmodulated carrier, because the rotational direction of the different phases. That is, the IQ switch 302 operates as follows.

When the reception frequency is f _o + f _s : I = I ′, Q = Q ′
When the reception frequency is f _o −f _s : I = Q ′, Q = I ′

  Switching control of the IQ switch 302 is performed by the baseband processing unit 118. Alternatively, the IQ switcher 302 may be included in the baseband processing unit 118.

  The reflected wave reader 110 does not replace each signal of the IQ after quadrature modulation in response to switching of the reception frequency, but each reception frequency in the positive direction and the negative direction at the center of the frequency of the unmodulated carrier. It is also possible to provide each receiving unit that performs quadrature modulation independently, and to distribute the received signal of the antenna 111 to one of the receiving units according to switching of the receiving frequency. FIG. 2A shows the configuration of the communication system in this case. Similarly, in this case, the reflected wave reader cannot receive signals due to multipath interference or interference with interference waves from other systems at one of the two reflected frequencies. Even so, if the modulated reflected wave signal can be selectively received at the other reception frequency, the reception rate can be increased and a transmission system that is resistant to interference can be provided.

  FIG. 2B shows a configuration example of still another communication system. In the illustrated example, the reflected wave reader does not have a distributor, and an independent antenna is provided for each reception frequency. In this case, the reflected wave reader can increase the reception rate by ratio-synthesizing the received signals at each reception frequency, in addition to selectively receiving the modulated reflected wave signal by switching the reception frequency, and is resistant to interference. A system can be provided.

Refer to FIG. 3 for a mechanism for adaptively receiving and processing QPSK modulated wave signals transmitted by reflected waves of f _o + f _s and f _o −f _s according to the respective reception qualities on the reflected wave reader 110 side. While explaining.

  In the figure, reference numeral 400 is a frame format of data transmitted from the reflector 100 to the reflected wave reader 110. The data frame 400 may be transmitted concatenated or transmitted as a packet in bursts.

  Reference numeral 401 is a preamble part necessary for synchronizing bits or symbols. For example, in the case of the QPSK modulation method, the pattern is 10011001. Following the preamble portion 401, a unique word portion (UW) 402 is transmitted and used on the receiving side to determine the data start position.

  After transmitting these frame headers, a data portion 403 in which actual transmission data (payload) is stored is transmitted. A CRC (Cyclic Redundancy Code) unit 404 for error detection is added to the end of the frame. The CRC unit 404 is calculated and assigned to the data unit 403.

  There are several possible timings for switching the reception frequency (or switching the ratio synthesis of the reception signals of each reception frequency) on the reflected wave reader 110 side. Below, the case where it performs in the preamble part 401 is demonstrated as the example.

The preamble section 401 is set longer than the length necessary for actual synchronization, and for example, a preamble detection section 405 is provided in the first half. Front half 406 of the preamble detection section 405, for example, the frequency is f _o + f _s (or f _o -f _s), to detect the preamble pattern.

At this time, the average received input level is also calculated by the baseband processing unit 118. And if it was possible to detect the preamble at a constant value L _th or more, while the frequency was to f _o + f _s, to migrate to the detection of the unique word part. Here, when the level is lower than L _th or when the preamble cannot be detected, the reception frequency is switched to f _o −f _s (or f _o + f _s ) in the subsequent frequency switching section 407. In conjunction with this reception frequency switching operation, the IQ switching unit 302 after quadrature modulation by the reception unit 114 is controlled as described above.

Then, similarly, also in the latter half portion 408 of the preamble detection section, if the average reception input level is higher than the predetermined value L _th, and checks whether detects a preamble. Then, if both the OK, while in f _o -f _s after switching the reception frequency, the process proceeds to the detection of the unique word part. On the other hand, even if the result of checking the reception frequency by switching to f _o −f _s is NG, the process proceeds to detection of the unique word part as it is. When starting from the next frame, it shall start from the frequency received in the previous frame.

In the example shown in FIG. 3, since the average reception input level of the first half 406 was lower than L _th , the preamble was detected by the second half 408 after switching to the other reception frequency in the frequency switching section 407. It shows a state. In the example described here, the detection of the received input level and the detection of the preamble pattern are combined, but only one of the detections may be performed.

  If the frequency switching unit 407 is provided at the head of each frame, it is expected that the overhead increases and the data transmission efficiency decreases. In such a case, it is possible to avoid an increase in overhead by performing frequency selection only at the start of data transmission (that is, providing the frequency switching unit 407 only in the data frame at the time of disclosure of data transmission). is there.

  In this way, a reflected wave reader that receives a modulated reflected wave signal while transmitting a modulated reflected wave signal generated in both positive and negative frequencies centered on the frequency of the unmodulated carrier from the reflector. On the side of the reflected wave signal consisting of two reception frequencies, even if it cannot be received due to multipath interference or interference with interference waves from other systems at one reception frequency, If the modulated reflected wave signal can be received, the reception rate can be increased, and a transmission system that is resistant to interference can be provided.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention. FIG. 2A is a modification of the communication system shown in FIG. FIG. 2B is a modification of the communication system shown in FIG. FIG. 3 is a diagram for explaining a mechanism for adaptively receiving processing according to reception quality in the communication system shown in FIG. FIG. 4 is a diagram showing a configuration example of a communication system in which the reception frequency f _o is shifted in the positive or negative direction by a predetermined center frequency f _s and the reflected wave is sent back on the reflector side. FIG. 5 is a diagram showing a spectrum of reflected waves in the communication system shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Reflector 101 ... Antenna 102 ... Backscatter modulator 103 ... Subcarrier QPSK modulator 104 ... Subcarrier oscillator 105 ... Application part 110 ... Reflected wave reader 111 ... Antenna 112 ... Circulator 114 ... Reception part 115 ... Local oscillator ( Receiver)
116: Transmitter 117: Local oscillator (transmission side)
118 ... Baseband processing unit 119 ... Application unit 301 ... Local oscillator 302 ... IQ switcher (SWAP)

Claims (12)

A wireless communication system comprising a reflector that receives an unmodulated carrier and transmits a modulated reflected wave signal, and a reflected wave reader that transmits the unmodulated carrier and receives the modulated reflected wave signal,
In the reflector side, the transmission data subjected to primary modulation by the subcarrier frequency f _s, further positive and negative about the frequency of the unmodulated carrier when entering and multiplying the unmodulated carrier f _o the primary modulation signal Transmit each modulated reflected wave signal generated at each of the bidirectional frequencies,
In the reflected wave reader, adaptive reception processing is performed according to the reception quality of each modulated reflected wave signal.
A wireless communication system. The reflected wave reader switches to the reception frequency in the plus or minus direction at the center of the frequency of the unmodulated carrier, depending on the reception quality of each modulated reflected wave signal.
The wireless communication system according to claim 1. The reflected wave reader switches the I-axis signal and the Q-axis signal after orthogonally modulating the received modulated reflected wave signal in response to switching the reception frequency in the positive or negative direction of the center of the frequency of the unmodulated carrier. Do,
The wireless communication system according to claim 2. Each of the reflected wave readers performs orthogonal modulation at the respective reception frequencies in the positive direction and the negative direction at the center of the frequency of the unmodulated carrier, and receives a received signal at any of the reception units according to switching of the reception frequency Equipped with a distributor
The wireless communication system according to claim 2. The preamble detection section of the frame transmitted from the reflector to the reflected wave reader includes a first half of a preamble detection section that transmits a preamble pattern at either the plus or minus direction center of the frequency of the unmodulated carrier. A second half of a preamble detection section for sending a preamble pattern at the other frequency, and a frequency switching section between the first half and the second half,
The reflected wave reader receives the first half at one reception frequency, checks the reception input level or preamble pattern of the preamble, and switches the other reception frequency in the frequency switching interval according to the check result. The latter half is received at the other reception frequency, and the received input level of the preamble or the preamble pattern is checked.
The wireless communication system according to claim 1. A wireless communication device that receives an unmodulated carrier and transmits a modulated reflected wave signal,
An antenna,
Primary modulation means for primarily modulating transmission data with a center frequency f _s ;
Secondary modulation means for performing secondary modulation by multiplying the primary modulation signal by an unmodulated carrier received by the antenna;
Transmitting a modulated reflected wave signal composed of both the frequency numbers f _o + f _s and f _o −f _s generated by the secondary modulation means;
A wireless communication apparatus. The preamble detection interval of at least a part of the transmission frame to be transmitted includes the first half of the preamble detection interval in which the preamble pattern is transmitted at either the positive or negative frequency center of the frequency of the unmodulated carrier, and the other frequency. Including a frequency switching section between the latter half of the preamble detection section for sending the preamble pattern and the first half and the latter half,
The wireless communication apparatus according to claim 6. A wireless communication device that transmits an unmodulated carrier and receives a modulated reflected wave signal,
An antenna,
When the transmission data from the communication partner that has transmitted the unmodulated carrier is subjected to primary modulation at the subcarrier frequency f _s and further multiplied by the input of the unmodulated carrier f _o , the frequency of the unmodulated carrier Receiving means for receiving a signal received by the antenna with each of the modulated reflected waves generated respectively in the positive and negative bidirectional frequencies,
Control means for performing adaptive reception processing according to the reception quality of each modulated reflected wave signal;
A wireless communication apparatus comprising: The control means switches the reception frequency in the reception means to either the plus or minus direction of the center of the frequency of the unmodulated carrier according to the reception quality of each modulated reflected wave signal.
The wireless communication apparatus according to claim 8. IQ switching means for switching the I-axis signal and the Q-axis signal after orthogonally modulating the received modulated reflected wave signal according to the switching operation of the reception frequency in the receiving means,
The wireless communication apparatus according to claim 9. The receiving means includes each receiving unit that performs orthogonal modulation at each receiving frequency in the positive direction and the negative direction at the center of the frequency of the unmodulated carrier,
Further comprising a distributor that distributes the received signal to any one of the receiving units in response to switching of the receiving frequency in the receiving means;
The wireless communication apparatus according to claim 9. The preamble detection interval of the transmission frame received from the communication partner is the first half of the preamble detection interval that transmits the preamble pattern at either the positive or negative frequency center of the frequency of the unmodulated carrier, and the preamble at the other frequency. A frequency switching section is included between the latter half of the preamble detection section for sending the pattern, and the first half and the second half,
The control means receives the first half at one reception frequency, checks the reception input level or preamble pattern of the preamble, switches the other reception frequency in the frequency switching section according to the check result, and The second half is received at the other reception frequency, and the reception input level or preamble pattern of the preamble is checked.
The wireless communication apparatus according to claim 8.

Images