JP5085499B2 - Wireless communication method, system, wireless transmitter and wireless receiver - Google Patents

Description

  The present invention provides a wireless communication method, system, and wireless communication that can form a band-pass filter that allows only a desired transmission signal to pass therethrough even when the transmission frequency of a signal indicating the presence of the transmitter is not known. The present invention relates to a transmitter and a wireless receiver.

  In wireless communication in which a signal is transmitted using an RF frequency, a carrier frequency to be used between transmitters and receivers is usually determined prior to communication. In the transmitter, the baseband signal to be transmitted is converted to a frequency higher by a frequency determined in advance with the receiver, and transmitted as an RF signal. The frequency of the RF signal, that is, the frequency after conversion is the carrier frequency. The receiver converts the received RF signal to a frequency lower than that determined in advance with the transmitter, that is, the carrier frequency, thereby obtaining a baseband signal transmitted by the transmitter as an RF signal.

  Patent Document 1 discloses a method capable of data transmission without having to decide a carrier frequency of a signal in advance between a transmitter and a receiver. According to Patent Document 1, a transmitter transmits a signal obtained by code-spreading a baseband signal using a spreading code and a spreading code used for spreading by a frequency Δf and transmitting at an arbitrary carrier frequency. In the receiver, a baseband signal can be obtained around DC by multiplying the reception signal and the complex conjugate sequence of the signal obtained by frequency shifting the reception signal by Δf. Therefore, even if the carrier frequency of the transmission signal is unknown, the receiver can obtain the desired signal as long as Δf is known.

  On the other hand, it is known to use a bandpass filter in a receiver in order to extract a desired signal located at a predetermined frequency and suppress unnecessary components located at other frequencies in wireless communication. The bandpass filter can be realized by an analog circuit using a capacitor or an inductor, an element such as a surface acoustic wave filter, or an IIR filter or FIR filter by digital signal processing. However, these bandpass filters need to know in advance the frequency at which the desired signal is located in order to extract the desired signal.

Furthermore, there is known an adaptive equalizer that performs equalization by changing parameters of a digital filter in accordance with a wireless environment (see Non-Patent Document 1). The adaptive equalizer has a reference signal input in addition to the equalization input signal, performs the equalization operation on the equalization input signal during the training period, and the difference between the resulting equalization output signal and the reference signal The operation parameter of the filter is adjusted so that becomes smaller. In periods other than the training period, the adaptive equalizer operates under operating parameters adjusted by training.
JP 2008-177914 A Simon Haykin, “Adaptive filter theory,” Prentice Hall (2001)

  According to the method of Patent Document 1, it is possible to transmit a signal with an unknown carrier frequency between a transmitter and a receiver. However, the method of Patent Document 1 also multiplies the noise components distributed in the reception band during the multiplication process at the time of reception, and as a result, the noise power becomes approximately square. Therefore, it is desired to remove noise and unnecessary signals located outside the vicinity of the carrier frequency of the transmission signal using a band pass filter before multiplication. However, as described above, the bandpass filter cannot be designed unless the frequency component to be passed is known.

  The present invention provides a wireless communication method that allows a receiver to set a communication procedure by forming a band-pass filter that allows only a desired transmission signal to pass even if the transmission frequency of a signal indicating the presence of the transmitter is not known. An object is to provide a system, a wireless transmitter, and a wireless receiver.

  According to a first aspect of the present invention, a step of generating a training signal; a step of frequency-converting the training signal to generate a plurality of first conversion signals having a predetermined frequency difference; and the plurality of first conversions Synthesizing signals to generate a transmission signal; transmitting the transmission signal; receiving the transmission signal to obtain a reception signal; frequency-converting the reception signal to correspond to the frequency difference Generating a second converted signal shifted by a frequency; and an adaptive equalizer having one of the received signal and the second converted signal as a reference signal and the other signal as an input signal performs training. After the training, the adaptive equalizer equalizes the other signal to obtain an equalized signal; and a step of demodulating the equalized signal. To provide a wireless communication method having a; If.

  According to a second aspect of the present invention, a signal generator that generates a training signal; a transmission frequency converter that generates a plurality of first converted signals having a predetermined frequency difference by frequency-converting the training signal; A combining unit that combines a plurality of first converted signals to generate a transmission signal; a transmission unit that transmits the transmission signal; a reception unit that receives the transmission signal and obtains a reception signal; and frequency-converts the reception signal A reception frequency conversion unit that generates a second converted signal shifted by a frequency corresponding to the frequency difference; one of the received signal and the second converted signal as a reference signal, and the other signal as An adaptive equalizer that performs training as an input signal and equalizes the other signal after the training to obtain an equalized signal; and a demodulator that demodulates the equalized signal; Providing line communication system.

  According to a third aspect of the present invention, a step of generating a training signal having a predetermined time length; a step of generating the transmission signal by repeating the training signal a plurality of times; and a step of transmitting the transmission signal; Receiving the transmission signal and obtaining a received signal; delaying the received signal by a time corresponding to the time length to generate a delayed signal; and one of the received signal and the delayed signal And an adaptive equalizer having the other signal as an input signal performs training; and after the training, the adaptive equalizer equalizes the other signal to obtain an equalized signal; A radio communication method comprising: demodulating the equalized signal;

  According to a fourth aspect of the present invention, a training signal generation unit that generates a training signal having a predetermined length of time; a transmission signal generation unit that generates a transmission signal by repeating the training signal a plurality of times; and the transmission signal A transmission unit that receives the transmission signal and obtains a reception signal; a delay unit that generates a delay signal by delaying the reception signal by a time corresponding to the time length; and the reception signal and An adaptive equalizer that performs training using one of the delayed signals as a reference signal and the other signal as an input signal, and equalizes the other signal after the training to obtain an equalized signal; A radio communication system comprising: a demodulator that demodulates a signal;

  According to a fifth aspect of the present invention, a first signal generation unit that generates a training signal; a first frequency conversion unit that converts the training signal into a first frequency to obtain a first converted signal; and modulation data A second signal generation unit that generates a signal; a first multiplication unit that generates a first multiplication signal by multiplying the training signal and the modulated data signal in a period other than a training period; A second frequency converter that obtains a second converted signal by converting the multiplication signal into a second frequency having a predetermined frequency difference from the first frequency in a period other than the training signal and the training period; There is provided a wireless transmitter comprising: a combining unit that combines the first converted signal and the second converted signal to generate a transmission signal; and a transmission unit that transmits the transmission signal.

  According to a sixth aspect of the present invention, a receiving unit that receives the transmission signal transmitted from the radio transmitter according to the fifth aspect and obtains a received signal; and frequency conversion of the received signal to convert the frequency difference A third frequency converting unit that generates a third converted signal shifted by a frequency corresponding to the frequency; and training using the received signal as a reference signal, the third converted signal as an input signal, and the third signal after the training. An adaptive equalizer that equalizes a transformed signal to obtain an equalized signal; a digital filter that obtains a filtered signal by filtering the received signal using tap coefficients after training of the adaptive equalizer; and the equalized signal A complex conjugate computation unit that performs complex conjugate computation on the complex conjugate signal to obtain a complex conjugate signal; and multiplies the complex conjugate signal and the filter signal to generate a second multiplication signal A radio receiver comprising: a multiplier of 2; a low-pass filter that passes only a low-frequency component of the second multiplied signal to obtain the modulated data signal; and a demodulator that demodulates the modulated data signal I will provide a.

  According to a seventh aspect of the present invention, a reception unit that receives the transmission signal transmitted from the radio transmitter according to the fifth aspect and obtains a reception signal; and frequency conversion of the reception signal to convert the frequency difference A third frequency converting unit that generates a third converted signal shifted by a frequency corresponding to the above; performing training using the received signal as a reference signal, the third converted signal as an input signal, and performing an adaptive operation after the training A first adaptive equalizer that obtains a first equalized signal by equalizing the third converted signal and performing training using the third converted signal as a reference signal and the received signal as an input signal; A second adaptive equalizer that later equalizes the received signal to obtain a second equalized signal; a complex conjugate arithmetic unit that performs a complex conjugate operation on the first equalized signal to obtain a complex conjugate signal; Said compound A second multiplier for multiplying the conjugate signal and the second equalized signal to generate a second multiplied signal; passing only the low frequency component of the second multiplied signal and passing the modulated data signal A radio receiver comprising: a low-pass filter to be obtained; and a demodulator that demodulates the modulated data signal.

  According to an eighth aspect of the present invention, a first signal generating unit that repeatedly generates a training signal having a predetermined time length τ; a second signal generating unit that generates a modulated data signal; and a training having a time length of 2τ or more. A first multiplication unit that generates a multiplication signal by multiplying the training signal and the modulated data signal in a period other than a period and a pilot signal period equal to or longer than a time length τ following the training period; A frequency conversion unit that generates a transmission signal by frequency-converting the training signal in a pilot signal period, and a frequency other than the training signal and the multiplication signal in a period other than the pilot signal period; and a transmission unit that transmits the transmission signal; A wireless transmitter is provided.

  According to a ninth aspect of the present invention, there is provided a receiving unit for receiving a transmission signal from the radio transmitter according to the eighth aspect; and delaying the received signal by time τ during the training period to obtain a delayed signal A delay unit; adapting to perform training during a time τ of the latter half of the training period using the delayed signal as a reference signal and the received signal as an input signal, and equalize the input signal after the training to obtain an equalized signal An equalizer; a complex conjugate operation unit that performs a complex conjugate operation on the equalized signal to obtain a complex conjugate signal; a storage unit that stores the complex conjugate signal during the pilot signal period; and the training period; A second multiplier for multiplying the equalized signal and the complex conjugate signal stored in the storage unit during a period other than the pilot signal period to obtain a second multiplied signal; Provided is a radio receiver comprising: a low-pass filter that obtains the modulated data signal by passing only low frequency components of the multiplication signal; and a demodulator that demodulates the modulated data signal.

  According to a tenth aspect of the present invention, a receiving unit that receives a transmission signal from the radio transmitter according to the eighth aspect; and delaying the received signal by time τ during the training period to obtain a delayed signal A delay unit; adapting to perform training during a time τ of the latter half of the training period using the delayed signal as a reference signal and the received signal as an input signal, and equalize the input signal after the training to obtain an equalized signal An equalizer; a storage unit for storing the equalized signal during the pilot signal period; and a complex conjugate operation for the equalized signal read from the storage unit during a period other than the training period and the pilot signal period. A complex conjugate operation unit for obtaining a complex conjugate signal; and multiplying the equalized signal obtained by the adaptive equalizer and the complex conjugate signal to obtain a second multiplied signal A radio receiver comprising: a second multiplication unit; a low-pass filter that obtains the modulated data signal by passing only a low frequency component of the second multiplied signal; and a demodulator that demodulates the modulated data signal. Provide a machine.

  According to the present invention, a plurality of first converted signals having a predetermined frequency difference obtained by frequency conversion of a training signal are combined and transmitted, and the reception side converts the received signal to frequency and corresponds to the frequency difference. The second converted signal shifted by the frequency is generated, and the frequency of the training signal is received by an adaptive equalizer that uses either the received signal or the second converted signal as a reference signal and the other signal as an input signal. Even if it is not known on the side, it is possible to form a bandpass filter that allows only a desired signal having a predetermined frequency to pass therethrough.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the communication system according to the first embodiment of the present invention includes a transmitter 100, a transmission antenna 110, a reception antenna 201, and a receiver 200. The transmitter 100 includes a transmission processing unit that generates a radio signal to be transmitted. The receiver 200 includes a band-pass filter 202 and a reception processing unit 203 that performs demodulation processing of the received radio signal.

<About the transmission processing unit in the transmitter 100>
FIG. 2 shows a transmission processing unit in the transmitter 100. FIG. 3 shows a time waveform and a spectrum of a signal generated by the transmission processing unit. The transmission processing unit in FIG. 2 includes a training sequence generation unit 101, a first frequency conversion unit 102, a second frequency conversion unit 103, a local oscillator 104, and a synthesis unit 105. A transmission signal 116 that is a training signal output from the synthesizer 105 is supplied to a transmission unit including the transmission antenna 110 in FIG.

  The training sequence generation unit 101 generates a training sequence 111 to be transmitted to the receiver 200. The training sequence 111 is not necessarily a specially determined sequence, and an arbitrary sequence such as a modulated pseudo-random sequence or a sine wave can be used. In this embodiment, the training sequence 111 is assumed to be a BPSK (Binary Phase Shift Keying) modulated pseudo-random sequence. The training sequence 111 has a sequence length of τ and a modulation speed of Fs. That is, the training sequence generation unit 101 generates a training sequence 111 as indicated by a solid line in the time waveform of FIG.

  The local oscillator 104 generates local signals 112 and 113 for the first frequency converter 102 and the second frequency converter 103 to perform frequency conversion. The first frequency conversion unit 102 and the second frequency conversion unit 103 convert the baseband training sequence 111 generated by the training sequence generation unit 101 into predetermined transmission frequencies f1 and f2, respectively, as shown by the broken lines in FIG. The first training signal 114 and the second training signal 115 are generated. The first frequency conversion unit 102 and the second frequency conversion unit 103 are synchronized with each other, and a predetermined frequency difference Δf (= f2−f1) is provided between the frequencies f1 and f2.

  The first frequency conversion unit 102 and the second frequency conversion unit 103 are typically realized by a mixer. In this case, the local oscillator 104 supplies the first local signal 112 and the second local signal 113 having the frequency difference Δf to the first frequency conversion unit 102 and the second frequency conversion unit 103, respectively. The local oscillator 104 supplies a common local signal to the first frequency conversion unit 102 and the second frequency conversion unit 103 by providing a signal generator and a mixer having a frequency Δf in the second frequency conversion unit 103 in advance. You may do it. That is, for example, the first frequency converter 102 uses a common local signal as the first local signal, and the second frequency converter 103 generates the second local signal by mixing the common local signal and the signal of the frequency Δf. To.

  The first training signal 114 and the second training signal 115 are synthesized by the synthesis unit 105. That is, the synthesizer 105 synthesizes the first training signal 114 having the frequency f1 and the second training signal 115 having the frequency f2, and generates a transmission 116 having two frequency spectra. The transmission signal 116 generated in this way is supplied to the transmission antenna 110 in FIG. 1 and radiated as a radio wave to the space.

  When the transmission signal 116 is expressed on the time-frequency plane, the spectrum is as shown on the right side of FIG. That is, BPSK signals whose frequencies are separated by Δf are arranged in the frequency direction, and these two BPSK signals are transmitted simultaneously (that is, synchronously) in the time direction. In other words, the transmission signal 116 in the present embodiment is an FDM signal in which two BPSK signals are frequency-multiplexed.

  Although the two frequency conversion units 102 and 103 are provided in the transmission processing unit of the transmitter 100, either one of the frequency conversion units 102 and 103 may be omitted. For example, if the second frequency conversion unit 103 is omitted, the signal of the training sequence 111 is directly used as the second training signal 115.

<Bandpass Filter 202 in Receiver 200>
Next, the bandpass filter 202 in the receiver 200 of FIG. 1 will be described in detail with reference to FIGS. The band pass filter 202 includes a frequency conversion unit 205 and an adaptive equalizer 206 as shown in FIG.

  The reception antenna 201 in FIG. 1 included in the reception unit receives the broadband, high-frequency transmission signal 116 including the training signals 114 and 115 of the frequencies f1 and f2 from the transmitter 100, and outputs the reception signal 211. The reception signal 211 output from the reception antenna 201 further includes noise generated in the transmitter 100 and the receiver 200 and interference waves generated by other wireless devices.

  In the frequency converter 205, the received signal 211 from the receiving antenna 201 is frequency-converted. The frequency conversion unit 205 includes a mixer 2051 and a local oscillator 2052. The local oscillator 2052 generates a local signal 212 for the mixer 2051 to perform frequency conversion.

The local signal 212 from the local oscillator 2052 is a signal having a frequency corresponding to the frequency difference Δf between the frequencies f1 and f2 of the first training signal 114 and the second training signal 115 included in the transmission signal 115 transmitted from the transmitter 100, For example, a sine wave signal having a frequency Δf represented by ^ej2πΔft is used. That is, the mixer 2051 performs frequency conversion by multiplying the first training signal and the second training signal of the frequencies f1 and f2 included in the received signal 211 by the local signal 212 of the frequency Δf, and converts the frequency f2 and the converted signal 213 of f2 + Δf. Is generated. The converted signal 213 is output from the frequency conversion unit 205.

  The adaptive equalizer 206 has two input terminals, a reference signal input terminal and an equalizer input terminal, and the received signal 211 input to the bandpass filter 202 is input as a reference signal to the reference signal input terminal, and is subjected to frequency conversion. The converted signal 213 from the unit 205 is input to the equalizer input terminal as an input signal. In the adaptive equalizer 206 of this embodiment, the received signal 211 is used as a reference signal and the converted signal 213 is used as an input signal, but conversely, the received signal 211 may be used as an input signal and the converted signal 213 may be used as a reference signal.

  FIG. 5 shows a well-known form of adaptive equalizer 206. In the adaptive equalizer 206, the result of applying the FIR filter 206 to the input signal (converted signal in this example) 213 to the equalizer input terminal is output as an equalized signal 214 from the equalizer output terminal. The adaptive equalizer 206 has a function of reducing the difference between the input signal 213 to the equalizer input terminal and the reference signal (in this example, the received signal 211) input to the reference signal input terminal.

  For example, in the well-known LMS (Least Mean Square) algorithm, as shown in FIG. 5, an adaptive equalization algorithm is used that tap coefficients that reduce the mean square error between the input signal 213 or the equalized signal 214 and the reference signal 211. It is obtained adaptively according to 2065 and set in the FIR filter 206. In FIG. 5, a difference between the equalized signal 214 and the reference signal 211 is obtained by a subtractor 2064, and this difference is applied to the adaptive equalization algorithm 2065 to calculate a mean square error, and a tap for minimizing this error. The coefficient is obtained.

  The FIR filter 206 shown in FIG. 5 includes a plurality of cascaded delay stages 2061 that receive an input signal 213, a multiplier 2062 that multiplies each tap output from the delay stage 2061 by a tap coefficient (FIR tap coefficient), and each An adder 2063 is provided that adds the output signals from the multiplier 2062 to obtain an equalized signal 214. A reference signal is indispensable for training to obtain a tap coefficient. However, after the training is completed, the reference signal is not necessary, and the tap coefficient is generally fixed to a value at the end of the training.

  In this embodiment, a signal as shown in FIG. 6 is input to the adaptive equalizer 206. That is, the received signal 211 in which the same signal components S11 and S12 are located at a frequency f2 separated by Δf from the frequencies f1 and f1 is input as a reference signal, and the input signal is a frequency f2 + Δf separated by Δf from the frequencies f2 and f2. A conversion signal 213 in which the same signal components S21 and S22 as the signal components S11 and S12 of the reference signal are located is input.

  Here, as shown in FIG. 6, since the noise components N1 and N2 of the input signal and the reference signal have undergone frequency conversion, they have different waveforms having no correlation. Therefore, the noise components N1 and N2 are suppressed by the operation of the adaptive equalizer 206. When attention is paid to the frequency f1, the signal component S11 exists in f1 of the received signal 211 that is the reference signal, but there is no signal component in f1 of the converted signal 213 that is the input signal. Even if a signal component exists in the input signal f1, it is an interference signal component coming from the interference source. As described above, the signal component located at the frequency f1 is not matched in the reference signal with the input signal of the adaptive equalizer 206, and thus is suppressed by the operation of the adaptive equalizer 206.

  Regarding the frequency f2 + Δf, the signal component S22 exists in f2 + Δf of the converted signal 213 that is the input signal, but there is no signal component in f2 + Δf of the received signal 211 that is the reference signal. Even if a signal exists in the reference signal f2 + Δf, it is an interference signal component coming from the interference source. Thus, the signal component located at f2 + Δf does not match in the input signal of the adaptive equalizer 206 and the reference signal, and thus is suppressed by the operation of the adaptive equalizer 206.

  On the other hand, for the periphery of the frequency f2, the adaptive equalizer 206 basically outputs the input signal as it is. This is because the signal component located at f2 of the converted signal 213 that is the input signal as shown in FIG. 6 is the first training signal component S12 included in the received signal 211, and the signal component located at f2 of the reference signal is , A second training signal component S21 included in the received signal 211.

  As described with reference to FIG. 2, the first training signal 114 and the second training signal 115 are composed of the same training sequence 111 and have the same frequency. Have the same signal shape. Accordingly, the adaptive equalizer 206 outputs the input signal as it is without modifying the f2 component of the input signal. Thus, the signal component located at the frequency f2 matches the input signal of the adaptive equalizer 206 in the reference signal, so that the input signal is not suppressed by the operation of the adaptive equalizer 206 and is output as it is.

  As described above, the band-pass filter 202 shown in FIG. 4 has a band-pass characteristic that passes only the component of the desired frequency f2 and suppresses other frequency components (for example, components of f1, f2 + Δf). Moreover, in general, a bandpass filter is designed with a predetermined frequency band to pass through, but in this embodiment, it is not necessary to know the frequencies f1 and f2 in advance, and only knows the frequency difference Δf. There is an advantage that the band-pass filter 202 is automatically formed.

  FIG. 7 shows an example when the operation of the bandpass filter 202 in this embodiment is confirmed by computer simulation. The same signal separated by Δf is used as an LMS reference signal, and a signal obtained by frequency-converting the reference signal by Δf is input. Noise is added to both. When the adaptive equalizer 206 using the LMS algorithm is operated on these signals, an FIR filter having frequency characteristics as shown in the figure can be obtained.

(Second Embodiment)
<About the transmission processing unit in the transmitter 100>
FIG. 8 shows a transmission processing unit in the transmitter of FIG. 1 according to the second embodiment of the present invention. FIG. 9 shows a time waveform of a signal generated by the transmission processing unit. The transmission processing unit of FIG. 8 includes a training sequence generation unit 101, a transmission delay unit 106, a selection unit 107, a third frequency conversion unit 108, and a local oscillator 109, and a transmission signal 120 output from the third frequency converter 108. Is supplied to the transmitting antenna 110 in FIG.

  The training sequence generation unit 101 generates a training sequence 111 to be transmitted to the receiver 200 as in the first embodiment. The training sequence 111 is not necessarily a specially determined sequence, and an arbitrary sequence such as a modulated pseudo-random sequence or a sine wave can be used. In this embodiment, the training sequence 111 is assumed to be a BPSK (Binary Phase Shift Keying) modulated pseudo-random sequence. Further, it is assumed that the training sequence 111 has a sequence length of τ and a modulation speed of Fs. That is, the training sequence generation unit 101 generates the third training sequence 111 that is the source of the first half (third training signal) of the transmission signal indicated by the solid line in the time waveform of FIG.

  The third training sequence 111 generated by the training sequence generation unit 101 is input to the transmission delay unit 106 and the selection unit 107. If the length of the third training sequence 111 is τ, the transmission delay unit 106 delays the third training sequence 111 by time τ and generates a fourth training sequence 117.

  The selection unit 107 selects and outputs one of the third training sequence 111 and the fourth training sequence 117. Specifically, the selection unit 107 outputs the third training sequence 111 during the time τ, and outputs the fourth training sequence 117 during the subsequent time τ. The training sequence 118 selected by the selection unit 107 is input to the third frequency conversion unit 108.

  The local oscillator 109 generates a local signal 119 for the third frequency conversion unit 108 to perform frequency conversion. The third frequency conversion unit 108 uses the local signal 119 to convert the training sequence 118 (the third training sequence 111 or the fourth training sequence 117) from the selection unit 107 into a predetermined transmission frequency f3 and generate a transmission signal 120. To do. The third frequency conversion unit 108 can be typically realized by a mixer or the like.

  An example of the transmission signal 120 output from the third frequency conversion unit 108 is shown in FIG. The first half of FIG. 9 is a third training signal obtained by frequency conversion of the third training sequence 111, and the second half of FIG. 9 is a fourth training signal obtained by frequency conversion of the fourth training sequence 117. In other words, the transmission signal 120 in this embodiment is a TDM signal in which two training signals are time-multiplexed. The transmission signal 120 generated in this way is supplied to the transmission antenna 110 in FIG. 1 and radiated as a radio wave to the space. The waveform of the radiated signal is as shown by the dotted line in FIG.

  In FIG. 8, the third frequency conversion unit 108 is arranged after the selection unit 107, but may be arranged immediately after the training sequence generation unit 101. That is, even if the training sequence from the training sequence generation unit 101 is converted to the transmission frequency f3 by the third frequency conversion unit 108 and then guided to the transmission delay unit 106 and the selection unit 107, the same result as in FIG. 8 is obtained. be able to.

<Bandpass Filter 202 in Receiver 200>
Next, the band pass filter 202 in the receiver 200 of FIG. 1 in the second embodiment will be described in detail with reference to FIGS. As shown in FIG. 10, the bandpass filter 202 in the second embodiment includes a reception delay unit 207 and an adaptive equalizer 206.

  1 receives a broadband, high-frequency transmission signal 120 including a training signal having a frequency f3 from the transmitter 100, and outputs a reception signal 221. At the same time, the reception signal 221 output from the reception antenna 201 includes noise generated in the transmitter 100 and the receiver 200 and interference waves generated by other wireless devices.

  In the reception delay unit 207, the reception signal 221 from the reception antenna 201 is delayed by time τ, and a delay signal 223 is generated. The reception signal 221 from the reception antenna 201 and the delay signal 223 from the reception delay unit 207 are input to the adaptive equalizer 206. The adaptive equalizer 206 has two input terminals, that is, a reference signal input terminal and an equalizer input terminal. A reception signal 221 input to the bandpass filter 202 is input to the equalizer input terminal as an input signal and received. The delay signal 223 from the delay unit 207 is input to the reference signal input terminal as a reference signal. In the adaptive equalizer 206 of the present embodiment, the received signal 221 is used as an input signal and the delayed signal 223 is used as a reference signal. Conversely, the received signal 221 may be used as a reference signal and the delayed signal 223 may be used as an input signal.

  In the present embodiment, for example, according to FIG. 11, a training signal is repeatedly input to the adaptive equalizer 206 a plurality of times. That is, the first half (third training signal) of the reception signal 221 is input as an input signal, and the second half (fourth training signal) of the reception signal 221 is input as a reference signal. Since these two signals are training signals, they are the same signal except for noise and time-varying transmission path distortion. Therefore, the adaptive equalizer 206 outputs the input signal as it is. However, since noise and interference waves have different shapes in the first half and the second half of the received signal 221, they are suppressed by the adaptive equalizer 206.

  As described above, the band-pass filter 202 shown in FIG. 10 has a band-pass characteristic that passes only the component of the desired frequency f3 and suppresses other frequency components. Moreover, in general, the bandpass filter is designed with a predetermined frequency band to pass, but in this embodiment, it is not necessary to know the frequency f3 in advance, and only knows the delay time τ. There is an advantage that the band-pass filter 202 is automatically formed.

(Third embodiment)
In the third embodiment, a bandpass filter described in the first embodiment is used, and a reception processing unit capable of demodulation even when the carrier frequency is unknown is also presented. According to the third embodiment, it is possible to realize a wireless communication system that enables data transmission without sharing the carrier frequency between the transceivers.

<About frame format>
FIG. 12 is a diagram illustrating a format of a transmission signal from the transmission antenna 110 of FIG. 1 in the third embodiment. A signal is transmitted simultaneously from the transmission antenna 110 at the frequencies f1 and f2. The transmission signal shown in FIG. 12 includes an equalizer header at time τ and a payload for transmitting data. The equalizer header located at the frequency f1 is the first training signal 114 in the first embodiment, and the equalizer header located at the frequency f2 is the second training signal 115 in the first embodiment. In addition, a payload section located at the frequency f1 is referred to as a first data signal, and a section located at f2 is referred to as a second data signal.

<About transmitter 100>
FIG. 13 shows details of the transmitter 100 in the third embodiment. The transmitter 100 in FIG. 13 includes a first signal generator 121, a second signal generator 122, a multiplier 123, a first frequency converter 124, a second frequency converter 125, a local oscillator 126, and a combiner 127. The transmission signal 148 output from the combining unit 127 is supplied to the transmission antenna 110. The operations of the first frequency conversion unit 124, the second frequency conversion unit 125, the local oscillator 126, and the synthesis unit 127 are basically the same as those in the first embodiment.

  The first signal generation unit 121 operates in the same manner as the training sequence generation unit 101 in the first embodiment, except that the first signal generation unit 121 continues to generate signals in the payload section in this embodiment. As with the training sequence generation unit 101 in the first embodiment, any training signal 141 generated by the first signal generation unit 121 may be used. In the present embodiment, the first signal generation unit 121 generates, as an example, a BPSK-modulated pseudorandom sequence as the training signal 141.

  The second signal generator 122 modulates data to be transmitted to the receiver 200 and outputs a modulated data signal 142. Data to be transmitted to the receiver 200 is, for example, digitized voice data, image data, user data such as text messages, broadcast data such as communication system parameters, or control data for controlling the receiver 200 Is included. Assume that the bandwidth of the second signal 142 is equal to or less than the bandwidth of the training signal 141. The second signal generator 122 outputs “1” as the modulated data signal 142 in the equalizer header section.

  The multiplier 122 multiplies the training signal 141 and the modulated data signal 142 in the payload period. Since “1” is output as the modulated data signal 142 from the second signal generator 122 in the equalizer header section, the multiplier 122 substantially outputs the training signal 141 from the first signal generator 121 as it is. Will do. In addition, the multiplier 122 spreads the modulated data signal 142 from the second signal generator 122 with the training signal 141 from the first signal generator 121 in the payload section.

  The training signal 141 from the first signal generator 121 is frequency-converted by the first frequency converter 124 as in the first embodiment, and the first converted signal 146 having the center frequency f1 is generated. The multiplication signal 143 output from the multiplier 123 is frequency-converted by the second frequency conversion unit 125 to generate a second conversion signal 147 having a center frequency f2 = f1 + Δf.

  The first frequency conversion unit 124 and the second frequency conversion unit 125 are typically realized by a mixer. In this case, the local oscillator 126 supplies the first local signal 144 and the second local signal 145 having the frequency difference Δf to the first frequency converter 124 and the second frequency converter 125, respectively. The local oscillator 126 supplies a common local signal to the first frequency converter 124 and the second frequency converter 124 by providing a signal generator and a mixer having a frequency Δf in the second frequency converter 125 in advance. You may do it.

  The first converted signal 146 and the second converted signal 147 are combined by the combining unit 127 to generate a transmission signal 148 as shown by the broken line in FIG. The transmission signal 148 generated in this way is transmitted by the transmission antenna 110. When the transmission signal 148 is expressed on the time-frequency plane, the spectrum is as shown on the right side of FIG. That is, BPSK signals whose frequencies are separated by Δf are arranged in the frequency direction, and these two BPSK signals are transmitted simultaneously (that is, synchronously) in the time direction.

<About receiver 200>
FIG. 15 shows details of the receiver 200 in the third embodiment. 15 includes a reception antenna 201, a frequency conversion unit 205, an adaptive equalizer 206, a complex conjugate calculation unit 208, a digital filter 209, a multiplier 220, a low-pass filter (LPF) 221 and a signal detection unit 222. ing. The frequency conversion unit 205 includes a mixer 2051 and a local oscillator 2052. The local oscillator 2052 generates a local signal 212 for the mixer 2051 to perform frequency conversion. Among these, the reception antenna 201, the frequency conversion unit 205, and the adaptive equalizer 206 operate in the same manner as in the first embodiment, and adaptively form a bandpass filter.

The reception antenna 201 receives the transmission signal 148 shown in FIG. 14 and generates a reception signal 211. The received signal 211 is input to the frequency conversion unit 205 and is frequency-converted using a local signal generated by the local oscillator 2052 in the mixer 2051, that is, a sine wave signal having a frequency Δf represented by ^ej2πΔft , and the frequency is shifted by Δf. The converted signal is generated. That is, the frequency conversion unit 205 multiplies the notification signals of the frequencies f1 and f2 included in the received signal 211 and the local signal of the frequency Δf, and obtains signals of the frequencies f2 and f2 + Δf as converted signals. The converted signal is input to the adaptive equalizer 206. The received signal is also input as a reference signal for the adaptive equalizer 206.

  The adaptive equalizer 206 performs a training operation in the equalizer header section (time τ) of the received signal 211. That is, the tap coefficient of the internal filter (for example, FIR filter) is adaptively changed so that the difference between the input signal (converted signal in this example) 213 and the reference signal (received signal 211 in this example) becomes small. With this operation, the adaptive equalizer 206 functions as a band-pass filter that passes only the signal of the frequency f2. When the training period by the equalizer header ends, the adaptive equalizer 206 fixes the coefficient of the internal filter. In the payload section of the received signal 211, training is not performed and only the signal of the frequency f2 is passed.

  On the other hand, the digital filter 209 has the same configuration as the internal filter of the adaptive equalizer 206. The tap coefficient obtained by training in the adaptive equalizer 206 is also set as the tap coefficient 241 for the digital filter 209. The digital filter 209 operates as a bandpass filter that passes only the component of the frequency f2 in the received signal.

  FIG. 16 shows the output spectrum of the digital filter and the output spectrum of the adaptive equalizer 206. Noise and signals located at the frequencies f1 and f2 + Δf are suppressed by the digital filter 209 and the adaptive equalizer 206, and a signal located at the frequency f2 passes through the digital filter 209 and the adaptive equalizer 206.

The equalized signal 214 output from the adaptive equalizer 206 is input to the complex conjugate calculation unit 208. The complex conjugate computation unit 208 performs complex conjugate computation on the input equalized signal 214 to generate a signal obtained by inverting the sign of the imaginary part, that is, a complex conjugate signal 243. For example, the complex conjugate calculation unit 208 ^converts the equalized signal 214 represented by e ^j2πf2t into a complex conjugate signal 243 represented by e− ^j2πf2t .

  The multiplier 220 multiplies the filter signal 242 output from the digital filter 209 and the complex conjugate signal 243 output from the complex conjugate calculation unit 208 to generate a multiplication signal 244. The multiplication signal 244 is input to the low pass filter 221. The low-pass filter 221 passes only a signal (a baseband signal in this example) having a frequency equal to or lower than a predetermined frequency among high-frequency signals that are the multiplication signals 244. Here, when the pass bandwidth of the low-pass filter 221 is equal to the bandwidth of the modulated data signal 142 generated by the second signal generator 122 in the transmitter 100 of FIG. 13, the modulated data is output as the output signal 245 of the low-pass filter 221. The signal 142 itself is obtained.

  The signal detection unit 222 demodulates the modulated data signal 142 obtained as the output signal 245 from the low-pass filter 221, and digitized voice data, image data, user data such as text messages, and notification data such as communication system parameters. Then, data such as control data for controlling the receiver is extracted.

  Next, operations after the digital filter 209 and the adaptive equalizer 206 in FIG. 15 will be described with reference to FIG. As shown in FIG. 16, in the filter signal 242 output from the digital filter 209, the product of the signal 141 and the signal 142 exists at the position of the frequency f2. On the other hand, in the equalized signal 214 output from the adaptive equalizer 206, the signal 141 exists at the position of the frequency f2. The difference in the frequency f2 component between the filter signal 242 and the equalized signal 214 is only whether or not the signal 142 is multiplied.

  Here, the complex conjugate of the equalized signal 214 output from the adaptive equalizer 206 by the complex conjugate arithmetic unit 108 is obtained, and the multiplier 220 multiplies the complex conjugate signal 243 and the filter signal 242 output from the digital filter 209. Consider the case. This means that two signals originally present at the same frequency are complex-conjugated for one and then multiplied, so that the multiplication signal 244 output from the multiplier 220 is centered on DC as shown in FIG. Becomes a signal. The component of the first signal 141 included in both the complex conjugate signal 243 and the filter signal 242 becomes DC in the multiplication signal 244, and a signal obtained by multiplying the remaining component of the second signal 142 is obtained. However, as shown in FIG. 16, signals other than the center frequency DC are also generated. However, by removing unnecessary signals by the low-pass filter 221, only the component of the second signal 142 can be extracted.

  As described above, according to the third embodiment, the receiver 200 does not need to know the frequencies such as f1 and f2. If the receiver 200 knows only the difference between f1 and f2, that is, the frequency difference Δf, it is transmitted from the transmitter 100. Series, that is, the component of the modulated data signal 142 can be extracted. In addition, since the adaptive equalizer 206 can adaptively form a band-pass filter, demodulation is possible even in a high noise environment with low received power and relatively high noise power.

  FIG. 17 shows an example in which the receiver 200 of FIG. 15 is modified. In the receiver 200 of FIG. 17, in addition to the adaptive equalizer 206 using the received signal 211 as a reference signal and the converted signal 213 from the frequency converting unit 205 as an input signal, a second alternative to the digital filter 209 in FIG. An adaptive equalizer 210 is included. Unlike the adaptive equalizer 206, the second adaptive equalizer 210 uses the converted signal 213 from the frequency converter 205 as a reference signal and the received signal 211 as an input signal. Even with such a configuration, a bandpass filter can be formed for the adaptive reception signal 211.

(Fourth embodiment)
In the fourth embodiment, a bandpass filter described in the second embodiment is used, and a reception processing unit capable of demodulation even when the carrier frequency is unknown is also presented. Therefore, according to the fourth embodiment, similarly to the third embodiment, it is possible to realize a wireless communication system that enables data transmission without sharing the carrier frequency between the transceivers.

<About frame format>
FIG. 18 is a diagram illustrating a format of a transmission signal transmitted from the transmission antenna 110 of FIG. 1 in the fourth embodiment. A signal is transmitted from the transmission antenna 110 at an arbitrary frequency. The transmission signal includes an equalizer header having a time length of 2τ, a demodulation header (also referred to as a pilot signal), and a payload for transmitting data. The first half of the equalizer header is the third training signal in the second embodiment. The second half of the equalizer header is the fourth training signal in the second embodiment. In addition, the payload section is referred to as a third data signal.

<About transmitter 100>
FIG. 19 shows details of the transmitter 100 according to the fourth embodiment. 19 includes a first signal generation unit 121, a second signal generation unit 122, a multiplier 123, a transmission delay unit 128, a selection unit 129, a third frequency conversion unit 130, and a local oscillator 131. A transmission signal 152 output from the conversion unit 130 is supplied to the transmission antenna 110. The operations of the transmission delay unit 128, the third frequency conversion unit 130, and the local oscillator 131 are the same as those in the second embodiment.

  The first signal generation unit 121 operates in the same manner as the training sequence generation unit 101 in the second embodiment, except that the sequence of the generated length τ is repeatedly generated in the payload section in the present embodiment. Similar to the training sequence generation unit 101 in the second embodiment, any training signal 141 generated by the first signal generation unit 121 may be used. In the present embodiment, the second signal generation unit 121 generates a BPSK-modulated pseudo-random sequence as an example of the training signal 141 as an example.

  The second signal generator 122 modulates data to be transmitted to the receiver 200 and outputs a modulated data signal 142. Data to be transmitted to the receiver 200 is, for example, digitized voice data, image data, user data such as text messages, broadcast data such as communication system parameters, or control data for controlling the receiver 200 Is included. The bandwidth of the modulated data signal 142 is assumed to be less than or equal to the bandwidth of the training signal 141. The second signal generator 122 outputs “1” as the modulated data signal 142 in the equalizer header section and the demodulation header section.

  The multiplier 122 multiplies the training signal 141 and the modulated data signal 142 as in the third embodiment. Similarly to the second embodiment, the transmission delay unit 128 delays the training signal 141 generated by the first signal generation unit 121 by the time τ and outputs a delay signal 149.

  The selection unit 129 selects the multiplication signal 143 from the multiplier 122 and outputs it to the third frequency conversion unit 130 during the transmission period of the third training signal, the demodulation header, and the third data signal in FIG. Further, the selection unit 129 outputs the delay signal 149 from the transmission delay unit 128 to the third frequency conversion unit 130 in the transmission period of the fourth training signal in FIG.

  Similar to the second embodiment, the third frequency converter 130 uses the sine wave local signal 151 generated by the local oscillator 131 to select the signal 150 (multiplier signal 143 or delay signal 149) selected by the selector 129. ) To generate a transmission signal 152.

<About receiver 200>
FIG. 20 shows details of the receiver 200 in the fourth embodiment. 20 includes a reception antenna 201, an adaptive equalizer 206, a first reception selection unit 231, a reception delay unit 232, a second reception selection unit 233, a complex conjugate calculation unit 208, a storage unit 234, and a multiplier 235. , A low-pass filter (LPF) 221 and a signal detector 222 are provided. Among these, the receiving antenna 201, the adaptive equalizer 206, the multiplier 235, the low-pass filter 221, and the signal detection unit 222 perform the same operations as in the third embodiment.

  The reception antenna 201 receives the transmission signal 152 shown in FIG. 12 and outputs a reception signal 251. The reception signal 251 is input to the first reception selection unit 231. The first reception selection unit 231 outputs the reception signal 251 to the reception delay unit 232 when receiving the third training signal, and the reception signal 251 to the adaptive equalizer 206 when receiving the fourth training signal and the third data signal. Output.

  The reception delay unit 232 delays the reception signal 221 by the time τ and inputs it to the adaptive equalizer 206 as a reference signal. The adaptive equalizer 206 receives the third training signal in the reception signal 221 as a reference signal and the fourth training signal in the reception signal 221 as an input signal in the header section for the equalizer of the reception signal 251. It will be. The third training signal and the fourth training signal are the same signal, and the shapes of noise and interference waves are different. Therefore, as a result of the training of the adaptive equalizer 206, a bandpass filter is formed in the same manner as in the second embodiment.

  The tap coefficient of the adaptive equalizer 206 is fixed in the section of the demodulation header of the received signal 251 and the third data signal. Therefore, the bandpass filter formed by the adaptive equalizer 206 suppresses noise and interference waves in the demodulation header and the third data signal.

  The equalized signal 253 output from the adaptive equalizer 206 is input to the second selection unit 233. The second selection unit 233 outputs nothing in the equalizer header section of the received signal 251, and inputs the equalized signal 253 that is an input signal to the complex conjugate calculation unit 208 in the demodulation header section. Further, the second selection unit 233 outputs an equalized signal 253 that is an input signal to the multiplier 235 in the payload section.

The complex conjugate calculation unit 208 performs complex conjugate calculation on the input high frequency signal that is the equalized signal 253, and generates a signal obtained by inverting the sign of the imaginary part, that is, the complex conjugate signal 254. For example, the complex conjugate calculation unit 208 ^converts the signal 253 represented by e ^j2πf2t into a complex conjugate signal 254 represented by e− ^j2πf2t . The storage unit 234 stores the reception demodulation header signal of the complex conjugate signal 254 and repeatedly outputs it to the multiplier 235. Note that the positions of the complex conjugate calculation unit 208 and the storage unit 234 are interchanged, the reception demodulation header signal included in the signal from the second selection unit 233 is stored in the storage unit 234, and the received reception demodulation header signal is stored. The complex conjugate calculation may be performed by the complex conjugate calculation unit 208 after reading.

  Multiplier 235 multiplies the signal in the payload section by the reception demodulation header signal included in complex conjugate signal 254 output from complex conjugate calculation unit 208. As a result, similarly to the third embodiment, the second signal 142 is obtained as DC of the multiplication signal 257 output from the multiplier 235. The multiplication signal 257 is input to the pass filter 221. The low-pass filter 221 passes only a signal (a baseband signal in this example) having a frequency equal to or lower than a predetermined frequency among the high-frequency signal that is the multiplication signal 257. Here, when the pass bandwidth of the low-pass filter 221 is equal to the bandwidth of the modulated data signal 142 generated by the second signal generator 122 in the transmitter 100 of FIG. 19, the modulated data is output as the output signal 245 of the low-pass filter 221. The signal 142 itself is obtained.

  The signal detector 222 demodulates the modulated data signal output from the low-pass filter 221, digitized voice data, image data, user data such as a text message, notification data such as a communication system parameter, and a receiver. Data such as control data for control is extracted.

  Thus, according to the fourth embodiment, it is not necessary for the receiver to know the frequency of the transmission signal, and if only the time τ is known, the transmission sequence transmitted by the transmitter, that is, the second signal that is data is transmitted. It can be taken out. In addition, since the adaptive equalizer 206 can adaptively form a band-pass filter, demodulation is possible even in a high noise environment with low received power and relatively high noise power.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

A block diagram showing an outline of a wireless communication system having a bandpass filter in a receiver The block diagram which shows the principal part of the radio transmitter which concerns on 1st Embodiment. The figure shown about the 1st training signal and the 2nd training signal which are contained in the transmission signal transmitted from the wireless transmitter of FIG. 1 is a block diagram showing a bandpass filter in a wireless receiver according to a first embodiment. Block diagram showing an example of an adaptive equalizer in FIG. The figure which shows the example of the signal waveform input into the equalizer for demonstrating operation | movement of the adaptive equalizer in FIG. The figure which shows the result of the computer simulation which was done to confirm the operation of the band pass filter The block diagram which shows the principal part of the wireless transmitter which concerns on 2nd Embodiment. The figure shown about the 3rd training signal and the 4th training signal which are contained in the transmission signal transmitted from the wireless transmitter of FIG. The block diagram which shows the band pass filter in the radio receiver which concerns on 2nd Embodiment The figure which shows the example of the signal waveform input into the equalizer for demonstrating operation | movement of the adaptive equalizer in FIG. The figure which shows the format of the transmission signal from the wireless transmitter which concerns on 3rd Embodiment. The block diagram which shows the principal part of the wireless transmitter which concerns on 3rd Embodiment. The figure which shows the waveform of the transmission signal transmitted from the wireless transmitter of FIG. The block diagram which shows the radio receiver which concerns on 3rd Embodiment The figure for demonstrating operation | movement of the radio | wireless receiver of FIG. FIG. 15 is a block diagram showing a modified example of the wireless receiver of FIG. The figure which shows the format of the transmission signal in 4th Embodiment. The block diagram which shows the principal part of the wireless transmitter which concerns on 4th Embodiment A block diagram showing a radio receiver concerning a 4th embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Transmitter 101 ... Training sequence production | generation part 102,103 ... Frequency conversion part 104 ... Local oscillator 105 ... Synthesis | combination part 106 ... Transmission delay part 107 ... Selection part 108 Third frequency converter 109 ... Local oscillator 110 ... Transmitting antenna 121 ... First signal generator 122 ... Second signal generator 123 ... Multipliers 124, 125, 130 ...・ Frequency converter 127... Synthesizer 128... Transmission delay unit 129... Selection unit 200... Receiver 201... Reception antenna 202. ... Frequency converter 206 ... Adaptive equalizer 207 ... Reception delay unit 208 ... Complex conjugate arithmetic unit 209 ... Digital filter 210 ... Adaptive Of 220 ... multipliers 221 ... low pass filter 222 ... signal detector

Claims (12)

Generating a training signal;
Frequency-converting the training signal to generate a plurality of first converted signals having a predetermined frequency difference;
Combining the plurality of first converted signals to generate a transmission signal;
Transmitting the transmission signal;
Receiving the transmission signal to obtain a reception signal;
Generating a second converted signal obtained by frequency-converting the received signal and shifting the received signal by a frequency corresponding to the frequency difference;
An adaptive equalizer having one of the received signal and the second converted signal as a reference signal and the other signal as an input signal performs training;
After the training, the adaptive equalizer equalizes the other signal to obtain an equalized signal;
And a step of demodulating the equalized signal. A signal generator for generating a training signal;
A transmission frequency conversion unit that frequency-converts the training signal to generate a plurality of first conversion signals having a predetermined frequency difference;
A combining unit that combines the plurality of first converted signals to generate a transmission signal;
A transmission unit for transmitting the transmission signal;
A receiving unit for receiving the transmission signal and obtaining a reception signal;
A reception frequency converter that converts the frequency of the received signal to generate a second converted signal shifted by a frequency corresponding to the frequency difference;
Adaptive equalization in which either one of the received signal and the second converted signal is used as a reference signal, training is performed using the other signal as an input signal, and the other signal is equalized after the training. With a vessel;
A radio communication system comprising: a demodulator that demodulates the equalized signal. Generating a training signal of a predetermined length of time;
Generating a transmission signal by repeating the training signal a plurality of times;
Transmitting the transmission signal;
Receiving the transmission signal to obtain a reception signal;
Delaying the received signal by a time corresponding to the time length to generate a delayed signal;
An adaptive equalizer having one of the received signal and the delayed signal as a reference signal and the other signal as an input signal performs training;
After the training, the adaptive equalizer equalizes the other signal to obtain an equalized signal;
And a step of demodulating the equalized signal. A training signal generator for generating a training signal of a predetermined length of time;
A transmission signal generation unit that generates the transmission signal by repeating the training signal a plurality of times;
A transmission unit for transmitting the transmission signal;
A receiving unit for receiving the transmission signal and obtaining a reception signal;
A delay unit that delays the received signal by a time corresponding to the time length to generate a delayed signal;
An adaptive equalizer that performs training using one of the received signal and the delayed signal as a reference signal and the other signal as an input signal, and equalizes the other signal after the training to obtain an equalized signal; ;
A radio communication system comprising: a demodulator that demodulates the equalized signal.   The wireless communication system according to claim 4, wherein the transmission signal generation unit includes a frequency conversion unit that converts the training signal to a predetermined transmission frequency. A first signal generator for generating a training signal;
A first frequency converter that converts the training signal to a first frequency to obtain a first converted signal;
A second signal generator for generating a modulated data signal;
A first multiplier that multiplies the training signal and the modulated data signal in a period other than a training period to generate a first multiplied signal;
A second converted signal is obtained by converting the training signal in the training period and converting the multiplication signal into a second frequency having a predetermined frequency difference from the first frequency in a period other than the training period. A frequency converter of;
A combining unit that combines the first converted signal and the second converted signal to generate a transmission signal;
A radio transmitter comprising: a transmission unit that transmits the transmission signal.   The first multiplication unit is configured to output the training signal as it is to the second frequency conversion unit during the training period, and to generate the first multiplication signal during a period other than the training period. The wireless transmitter according to claim 6. A receiving unit that receives the transmission signal transmitted from the wireless transmitter according to claim 6 and obtains a reception signal;
A third frequency converter that converts the frequency of the received signal to generate a third converted signal that is shifted by a frequency corresponding to the frequency difference;
An adaptive equalizer that performs training using the received signal as a reference signal, the third converted signal as an input signal, and equalizes the third converted signal after the training to obtain an equalized signal;
A digital filter that obtains a filtered signal by filtering the received signal using tap coefficients after training of the adaptive equalizer;
A complex conjugate computation unit that performs complex conjugate computation on the equalized signal to obtain a complex conjugate signal;
A second multiplier for multiplying the complex conjugate signal and the filter signal to generate a second multiplied signal;
A low-pass filter that obtains the modulated data signal by passing only low frequency components of the second multiplication signal;
And a demodulator for demodulating the modulated data signal. A receiving unit that receives the transmission signal transmitted from the wireless transmitter according to claim 6 and obtains a reception signal;
A third frequency converter that converts the frequency of the received signal to generate a third converted signal that is shifted by a frequency corresponding to the frequency difference;
A first adaptive equalizer that performs training using the received signal as a reference signal, the third converted signal as an input signal, and equalizes the third converted signal after the training to obtain a first equalized signal;
A second adaptive equalizer that performs training using the third converted signal as a reference signal, the received signal as an input signal, and equalizes the received signal after the training to obtain a second equalized signal;
A complex conjugate calculation unit that performs a complex conjugate calculation on the first equalized signal to obtain a complex conjugate signal;
A second multiplier for multiplying the complex conjugate signal and the second equalized signal to generate a second multiplied signal;
A low-pass filter that obtains the modulated data signal by passing only low frequency components of the second multiplication signal;
And a demodulator for demodulating the modulated data signal. A first signal generator for repeatedly generating a training signal having a predetermined time length τ;
A second signal generator for generating a modulated data signal;
A first multiplier for generating a multiplication signal by multiplying the training signal and the modulated data signal in a period other than a training period having a time length of 2τ or more and a pilot signal period having a time length of τ or more following the training period; ;
A frequency converter that generates a transmission signal by converting the frequency of the training signal during the training period and the pilot signal period, and frequency-converting the multiplication signal during periods other than the training period and the pilot signal period;
A radio transmitter comprising: a transmission unit that transmits the transmission signal. A receiving unit for receiving a transmission signal from the wireless transmitter according to claim 10;
A delay unit that delays the received signal by time τ during the training period to obtain a delayed signal;
An adaptive equalizer that performs training during a period τ of the latter half of the training period using the delayed signal as a reference signal and the received signal as an input signal, and equalizes the input signal after the training to obtain an equalized signal; ;
A complex conjugate computation unit that performs complex conjugate computation on the equalized signal to obtain a complex conjugate signal;
A storage unit for storing the complex conjugate signal during the pilot signal period;
A second multiplication unit that obtains a second multiplication signal by multiplying the equalized signal and the complex conjugate signal stored in the storage unit during a period other than the training period and the pilot signal period;
A low-pass filter that obtains the modulated data signal by passing only low frequency components of the second multiplication signal;
And a demodulator for demodulating the modulated data signal. A receiving unit for receiving a transmission signal from the wireless transmitter according to claim 10;
A delay unit that delays the received signal by time τ during the training period to obtain a delayed signal;
An adaptive equalizer that performs training during a period τ of the latter half of the training period using the delayed signal as a reference signal and the received signal as an input signal, and equalizes the input signal after the training to obtain an equalized signal; ;
A storage unit for storing the equalized signal during the pilot signal period;
A complex conjugate calculation unit that performs a complex conjugate calculation on the equalized signal read from the storage unit during a period other than the training period and the pilot signal period to obtain a complex conjugate signal;
A second multiplier for multiplying the equalized signal obtained by the adaptive equalizer and the complex conjugate signal to obtain a second multiplied signal;
A low-pass filter that obtains the modulated data signal by passing only low frequency components of the second multiplication signal;
And a demodulator for demodulating the modulated data signal.

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