JP2009081745A - Transmission system, transmitter, receiver, and transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a transmission system and the like that can solve the problems hindering the realization of a highly efficient and large-capacity transmission system, and that can realize downsizing and low power consumption.
A transmitter having at least one transmission unit that transmits a transmission signal obtained by modulating a source signal from a transmission antenna, and a reception unit that demodulates a reception signal obtained through a reception antenna. In the transmission system 1 including the receiver 5 having at least one, the nonlinear modulation unit 11 of the transmission unit 9 obtains a transmission signal by performing constant envelope modulation on the source signal, and the analog processing unit 21 of the reception unit 17 The received signal is converted into an IF signal, and the IF signal is sampled to generate an actual sampling signal.
[Selection] Figure 1

Description

  The present invention relates to a transmission system, a transmitter, a receiver, and a transmission method, and more particularly to a transmitter having at least one transmission means for transmitting a transmission signal obtained by modulating a source signal from a transmission antenna, and the reception antenna. The present invention relates to a transmission system including a receiver having at least one receiving means for demodulating a received signal.

  In order to meet the demand for high-speed transmission, conventionally, MIMO transmission technology using a plurality of antennas and OFDM that is strong in multipath transmission have been actively applied (see Non-Patent Document 1).

  FIG. 12 is a schematic block diagram of a conventional transmission system 301 that transmits signals using MIMO transmission technology and OFDM. In the transmission system 301, a signal is transmitted from a transmitter 303 having a plurality of antennas 309 and 311 to a receiver 305 having a plurality of antennas 313 and 315 through a MIMO transmission path 307.

  The transmitter 303 includes a linear modulation unit 317 and a linear amplifier unit 319 corresponding to the antenna 309, and includes a linear modulation unit 321 and a linear amplifier unit 323 corresponding to the antenna 311. A signal transmitted from the antenna 309 is subjected to linear modulation such as OFDM by the linear modulation unit 317 and subjected to power conversion processing by the linear amplifier unit 319. Similarly, the signal transmitted from the antenna 311 is processed by the linear modulation unit 321 and the linear amplifier unit 323.

  The receiver 305 includes a multi-level quantization AD unit 325 and a linear demodulation unit 327 corresponding to the antenna 313, and includes a multi-level quantization AD unit 329 and a linear demodulation unit 331 corresponding to the antenna 315. A demodulator 333 is included. A reception signal received by the antenna 313 is converted into a digital signal by the multi-level quantization AD unit 325. The multi-level quantization AD unit 325 is usually realized using an analog / digital converter (hereinafter referred to as “ADC”). The ADC is a multi-valued ADC that can express a converted digital signal with 10 bits for one sample signal. The digital signal converted by the multilevel quantization AD unit 325 is linearly demodulated by the linear demodulation unit 327. The signal received by the antenna 315 is also subjected to the same processing by the multilevel quantization AD unit 329 and the linear demodulation unit 331. The MIMO demodulator 333 separates interference components included in each signal subjected to linear demodulation by the linear demodulator 327 and 331.

Ye (Geoffrey) Li, 2 other authors, MIMO-OFDM for Wireless Communications: Signal Detection With Enhanced Channel Estimation, IEEE TRANSACTIONS ON COMMUNICATIONS, Vol.50, No.9, September 2002

  However, when a linear modulation scheme such as MIMO-OFDM is employed, application of a linear transmission amplifier is essential (see linear amplifier units 319 and 323 in FIG. 12). The application of the linear transmission amplifier can only achieve a power conversion efficiency of around 20% at the highest, and is the biggest impediment to reducing power consumption.

  Further, when a linear modulation scheme such as a MIMO-OFDM signal is employed, a highly accurate ADC is essential on the receiver side (see the multi-level quantization AD units 325 and 329 in FIG. 12). The ADC requires an analog circuit such as a comparator. This analog circuit cannot benefit from LSI miniaturization. For this reason, although it is a simple function, a large chip area is required, and both the circuit scale and the power consumption are increased. In particular, when MIMO is applied, it is necessary to apply a highly accurate ADC to each antenna, and therefore ADCs corresponding to the number of antennas are required. Furthermore, in order to maximize the performance of high-precision ADCs, application of AGC circuits is essential, but these circuits require complex control mechanisms including analog circuits, further increasing circuit area and power consumption. I will let you. Such a problem can be a problem not only in the case of MIMO but also in the case of SISO.

  Accordingly, an object of the present invention is to solve the above-described problems that impede achievement of a highly efficient and large-capacity transmission system, and to propose a transmission system and the like that can realize downsizing and low power consumption.

  The invention according to claim 1 includes a transmitter having at least one transmission means for transmitting a transmission signal obtained by modulating a source signal from a transmission antenna, and a reception means for demodulating the reception signal obtained via the reception antenna. In a transmission system including at least one receiver, the transmission means includes modulation means for obtaining the transmission signal by constant envelope modulation of the source signal, and the reception means converts the reception signal into an IF signal. First conversion means for conversion and analog / digital conversion means for sampling the IF signal to generate an actual sampling signal are provided.

  The invention according to claim 2 is the transmission system according to claim 1, wherein the source signal is generated by a code division multiplexed signal.

  The invention according to claim 3 is the transmission system according to claim 1 or 2, wherein the analog-to-digital conversion means performs 1-bit analog-to-digital conversion processing for outputting different values based on the amplitude of the signal. Outputs different values depending on whether the signal amplitude is greater than or equal to a predetermined value and less than a predetermined value, or greater than a predetermined value and less than or equal to a predetermined value .

  The invention according to claim 4 is the transmission system according to any one of claims 1 to 3, wherein the receiving means converts the real sampling signal into a complex baseband signal; and the complex Differentiating means for differentiating the baseband signal to generate a differential complex baseband signal, and the receiver receives the differential complex baseband signal in correlation with the complex baseband signal as a reference signal. A first correlation receiving unit that determines a received output value to generate a temporary determination bit; and a recombination unit that generates a modulation signal replica based on the temporary determination bit and generates a reference signal from the modulation signal replica And second correlation receiving means for correlating and receiving the differential complex baseband signal with the reference signal generated by the recombining means.

  The invention according to claim 5 is the transmission system according to claim 4, wherein the transmission path when the transmission signal reaches the receiver is a multipath transmission path, and the first correlation receiving means and The second correlation receiving means performs correlation reception for each path of the transmission path, and synthesizes the output signal after the correlation reception.

  The invention according to claim 6 is the transmission system according to any one of claims 1 to 5, wherein the transmitter has a plurality of transmission means, the receiver has a plurality of reception means, The transmission signal generated by each transmission means is simultaneously transmitted from the transmission antenna of each transmission means using the same carrier frequency, and after each transmission signal is combined via the transmission path, it is transmitted to the reception antenna of each reception means. Each of the receiving means performs correlation reception for each path of the transmission path with respect to the transmission path connecting each receiving antenna and one of the plurality of transmitting means, and the receiver It has an interference removal circuit for removing an interference component included in the output value after correlation reception outputted from each receiving means.

  The invention according to claim 7 is a transmitter having at least one transmission means for transmitting a transmission signal obtained by modulating a source signal from a transmission antenna, wherein each of the transmission means performs non-linear modulation on the source signal, and Modulation means for obtaining a transmission signal is provided, and the transmission signal is converted into an IF signal in a receiver that has arrived via a transmission path, and the IF signal is sampled to generate an actual sampling signal.

  According to an eighth aspect of the present invention, there is provided a receiver having at least one receiving means for demodulating a received signal obtained via a receiving antenna, wherein the received signal is obtained by nonlinearly modulating the received signal in a transmission path. And having a conversion means for converting the received signal into an IF signal and an analog / digital conversion means for sampling the IF signal to generate an actual sampling signal.

  The invention according to claim 9 comprises a transmitter having at least one transmission means for transmitting a transmission signal obtained by modulating the source signal from the transmission antenna, and a reception means for demodulating the reception signal obtained via the reception antenna. A transmission method in a transmission system comprising at least one receiver, wherein the modulation means of the transmission means performs constant envelope modulation on the source signal to obtain the transmission signal, and the first conversion means of the reception means Converting the received signal into an IF signal, an analog / digital converting means of the receiving means sampling the IF signal to generate an actual sampling signal, and a second converting means of the receiving means A step of converting a sampling signal into a complex baseband signal, and a differentiating means of the receiving means converting the complex baseband signal to A step of partial to generate a differentiated complex baseband signal, the correlation receiver of the receiver is intended to include a step of correlating receiving said differential complex baseband signal.

  An example of constant envelope modulation is FM modulation.

  According to the invention according to each claim of the present application, signal transmission by nonlinear modulation such as constant envelope modulation (for example, FM modulation) can be realized.

  Therefore, it is possible to apply a non-linear amplifier, and the power conversion efficiency can achieve 90% or more. A linear amplifier can only achieve a power conversion efficiency of around 20%. Therefore, efficient signal transmission can be realized.

  Further, as in the invention according to claim 3, it is possible to directly apply a 1-bit ADC of a sample. Such a low quantization ADC can be used, and further, since an AGC circuit is not required, it is possible to reduce the size.

  For example, it is important to enable broadband wireless access anywhere. However, as broadband advances, the communication area that one base station can defend becomes smaller, and as a result, a large number of base stations must be installed. Significant installation costs are required. Therefore, a cellular architecture is being studied in which each base station is relayed through the base station and a wired communication line is not required when installing the base station. These are called wireless mesh networks. In such a wireless mesh network, it is important to increase the efficiency and capacity of a wireless relay line connecting base stations. In order to increase the efficiency and capacity of a wireless relay line, it is effective to employ MIMO transmission for the line. In order to reduce the installation cost of a base station having a wireless relay function, it is necessary to apply a MIMO transmission system that enables a compact and low power consumption implementation. According to the present invention, such a compact and low power consumption mounting is possible.

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

  FIG. 1 is a schematic block diagram showing an example of a transmission system 1 according to an embodiment of the present invention. In the transmission system 1, the signal is transmitted from the transmitter 3 to the receiver 5 through the transmission path 7.

  The transmitter 3 includes a transmission unit 9 (corresponding to “transmission means” in claims). The transmission unit 9 includes a nonlinear modulation unit 11 that performs nonlinear modulation such as constant envelope modulation (for example, FM modulation) on the source signal, an amplifier unit 13 that performs power conversion processing to generate a transmission signal, and a transmission An antenna 15 is provided. Since the nonlinear modulation unit 11 performs nonlinear modulation such as FM modulation, the amplifier unit 13 can be realized by using a saturation amplifier that can achieve a power conversion efficiency of 90% or more. The transmission signal is transmitted from the transmission antenna 15. The source signal may be generated by a code division multiplexed signal.

  The receiver 5 includes a reception unit 17 (corresponding to “reception means” in claims) and a correlation reception processing unit 18. The receiving unit 17 includes a receiving antenna 19, an analog processing unit 21, and a digital processing unit 23. The reception signal obtained through the reception antenna 19 is demodulated by the analog processing unit 21, the digital processing unit 23, and the correlation reception processing unit 18. The analog processing unit 21 converts the received signal into an IF signal, samples the IF signal, and generates an actual sampling signal. In this embodiment, the analog processing unit 21 is realized using a 1-bit ADC (see 1-bit ADC 47 in FIG. 5). The digital processing unit 23 converts the real sampling signal into a complex baseband signal and differentiates the complex baseband signal to generate a differential complex baseband signal. The correlation reception processing unit 18 receives the differential complex baseband signal by correlation using the reference signal. When the transmission path is a multipath transmission path, correlation reception is performed for each path of the transmission path, and an output signal after correlation reception is synthesized.

  Next, the transmitter 3 in FIG. 1 will be described in detail with reference to FIGS.

FIG. 2 is a diagram illustrating a specific example of the transmitter 3 of FIG. The nonlinear modulation unit 11 includes a CDM (Code Division Multiple) unit 31 that performs code division multiplexing on the _N source signals b ₀ , b ₁ ,..., B _(N−1) , and pulse shaping for band limitation. A pulse shaping unit 33 for performing FM modulation, and an FM modulation unit 35 for performing FM modulation processing. The amplifier unit 13 includes an RF unit 37 including, for example, a transmission amplifier and a filter.

First, the operation of the CDM unit 31 in FIG. 2 will be described with reference to FIG. FIG. 3 is a diagram illustrating the time relationship of symbols that are simultaneously processed by the transmitter 3. 1 symbol consists of N _CM chips (representing a single chip in the symbol k in the chip 39.), N symbols are assumed to be multiplexed after diffusion. N _CM (≧ N) is equivalent to the spreading factor. C _i (t) is the spreading sequence of the i-th spreading code, T _C is the chip period, and T _B is the symbol period (= N _CM · T _C ). At this time, the output Ω _I (t) of the CDM unit 31 with respect to a certain information symbol k is expressed as the following equation (1). S _i represents an information symbol.

Next, the operation of the pulse shaping unit 33 in FIG. 2 will be described with reference to FIG. 4A is a diagram showing an example of the spectrum of Ω _I (t) before pulse shaping by the pulse shaping unit 33 of FIG. 2, and FIG. 4B is the spectrum of Ω _O (t) after pulse shaping. It is a figure which shows an example. FIG. 4 shows that the band is limited by pulse shaping.

Next, the operation of the FM modulation unit 35 in FIG. 2 will be described. The FM modulation unit 35 inputs Ω _O (t) and outputs f _FM (t) expressed by the equation (2). Here, ω _C is a carrier frequency, and k _FM is a modulation index.

The RF unit 37 performs power conversion processing and the like on f _FM (t), and the processed signal is transmitted from the transmission antenna 15.

  Next, the receiver 5 in FIG. 1 will be described in detail with reference to FIGS.

FIG. 5 is a diagram illustrating a specific example of the receiver 5 of FIG. The analog processing unit 21 includes an RF unit 41 including an LNA (Low Noise Amplifier) and a filter, a MIX unit 43 that performs frequency selection and generates an IF signal, a band pass filter (BPF) 45, and a 1-bit ADC 47. Have The digital processing unit 23 includes a digital MIX unit 49, a low pass filter (LPF) 51, and a differentiation circuit 52. The correlation reception processing unit 18 has a configuration in the case of a three-stage correlator, and includes delay elements 56 and 59, correlator banks 53, 55 and 58, and recombiners 54 and 57. In the correlation reception processing unit 18, the correlator bank 53 uses the baseband signal R ₀ (t) generated by passing through the LPF 51 as a reference signal, and the signal generated by passing R ₀ (t) through the differentiating circuit 53. Are received in correlation. The output of the correlator bank 53 is re-synthesized by the re-synthesizer 54. The correlator bank 55 receives the signal R _{r, 01} (t) after the recombining process by the recombiner 54 and the output signal of the differentiating circuit 52 delayed by the delay element 56. The correlator bank 55 uses R _{r, 01} (t) as a reference signal and correlates and receives the signal after the delay processing by the delay element 56. The output of the correlator bank 55 is re-synthesized by the re-synthesizer 57. The correlator bank 58 receives the signal R _{r, 02} (t) after the recombining process by the recombiner 57 and the signal delayed by the delay element 59. The correlator bank 58 uses R _{r, 02} (t) as a reference signal, and receives a signal subjected to delay processing by the delay element 59 in correlation.

  The operation of each part will be described more specifically.

  The RF unit 41 includes an LNA, a filter, and the like, and performs amplification and noise removal of the signal received by the antenna 19.

The MIX unit 43 performs frequency conversion from the frequency ω _c of the signal processed by the RF unit 41 to a lower frequency ω _i .

The BPF 45 extracts only the component in the vicinity of the frequency ω _{i from the} signal frequency-converted to ω _i by the MIX unit 43 and generates an IF signal by improving the SN ratio.

  The 1-bit ADC 47 outputs −1 or 1 compared with the reference amplitude for the IF signal generated by the BPF 45. For example, if the reference amplitude is 0, 1 is output if the amplitude of the signal input to the 1-bit ADC 47 is greater than 0, and -1 is output otherwise.

The digital MIX unit 49 and the LPF 51 perform frequency conversion processing again on the 1-bit ADC-processed IF signal, and convert the input signal into a signal near the frequency 0, that is, a baseband signal. The output baseband signal of the LPF 51 is represented by a signal R ₀ (t) represented by equation (3). Here, A (t) represents the amplitude.

Differentiating circuit 52 differentiates the baseband signal R ₀ (t), to produce a (4) signal D ₀ of the formula (t). Here, since FM modulation is used, the amplitude A (t) is almost given by a constant α that does not depend on time as shown in the equation (5). Therefore, the signal D ₀ (t) expressed by the equation (4) is given as the equation (6).

  Application of a 1-bit ADC causes a large quantization error. Therefore, it cannot be applied to a linear modulation type demodulation circuit in which information is transmitted with amplitude. However, the FM modulation employed by the present invention does not carry information on the amplitude but carries information on the frequency (or phase). Therefore, if sampling is performed at a sufficient sampling rate that does not impair frequency information, it is considered that information can be restored even with a 1-bit ADC. This is why the present invention performs sampling on an IF signal in which information energy is concentrated at a higher frequency than the baseband signal.

  With reference to FIG. 6, it will be described that information can be actually restored by IF signal sampling. FIG. 6 shows the result (a) of detecting the impulse response of the transmission line by the transmission method of the present invention that employs a 1-bit ADC when the transmission line of the impulse response given in (c) is given, and 10 The result (b) which detected the impulse response of the said transmission line at the time of changing to bit ADC is represented.

Specifically, the transmitter Ω _I (t) (see FIG. 2) is given by only one PN sequence code CPN (t), and at the same time, it is output from only one transmission antenna. Path detection to be performed at the receiving antenna.

A filter M (hereinafter referred to as “matching filter”) that matches CPN (t) is passed through the output of the differentiation circuit 52 of FIG. The impulse response of the matched filter is given by h _M (t) = C ^* _PN (T _M −t). Here, an asterisk * represents a complex conjugate, and T _M represents a time offset amount.

  FIG. 6 is a diagram illustrating an example of an output impulse response of the matched filter M. As described above, when (a) applies 1-bit ADC, (b) applies high-density quantized ADC (10-bit ADC). The result is shown. Further, (c) is an impulse response of the given multipath transmission path. The horizontal axis shows the passage of time.

  As shown in FIG. 6A, it can be seen that even when 1-bit ADC is applied, two peaks corresponding to the multipath transmission path shown in FIG. It can be seen that the difference between the results of applying the high-density quantization ADC shown in FIG. 6A and FIG. 6B is very small. Therefore, it was shown that path detection can be performed correctly even when 1-bit ADC is applied. Since path separation is possible even when 1-bit ADC is applied as shown in FIG. 6, the CPN (t) is multiplied by the information bit and transmitted, and the peak value appearing after passing through the matched filter is combined, that is, RAKE received. In this case, the information bit can be detected immediately. In this embodiment, this processing is performed by the correlator banks 53, 55 and 58 subsequent to the differentiation circuit 52.

Next, operations of the correlator banks 53, 55 and 58 will be described with reference to FIGS. FIG. 7 is a diagram illustrating an example of the configuration of the correlator banks 53, 55, and 58 of FIG. In the correlator bank 53, first, processing is performed using the baseband signal R ₀ (t) before passing through the differentiating circuit defined by Expression (3) as the reference signal R _r (t).

The delay unit 61 gives a time offset T ₀ to the signal D ₀ (t), the multiplier 63 multiplies p ₀ ^* c ₀ (t) R ₀ (t), and the integrator 65 performs integration processing.

Here, c ₀ (t) is a spreading sequence of the 0th spreading code. With reference to FIG. 8, T ₀ and p ₀ will be described. FIG. 8 is a diagram illustrating an example of a multipath transmission path. p ₀ , p ₁ , and p ₂ represent the amplitudes of the paths at times α ₀ , α ₁ , and α ₂ , respectively, and are complex numbers. For a multipath transmission path shown in Figure 8, T _0, T ₁ and T ₂ to T _D as a _{T B> T D> α 2} > α 1> α 0 with respect to the symbol period T _B, T ₀ = T _D −α ₀ , T ₁ = T _D −α ₁ , T ₂ = T _D −α ₂ are set.

Similarly, each multipath component is obtained by so-called correlation reception by the delay unit 67, the multiplier 69 and the integrator 71, and the delay unit 73, the multiplier 75 and the integrator 77, and finally, in-phase synthesis is performed in the addition 79. , Output b ^c ₀ is generated.

By the same processing, b ^c ₁ ,..., B ^c _(N−1) are obtained.

The re-synthesizer 54 re-synthesizes b ^c ₀ , b ^c ₁ ,..., B ^c _(N−1) . The re-synthesizer 54 generates the signal Ω _{r, I} (t) according to the equation (7). Here, det (b ^c _i ) (i is a number from 0 to N−1) is a provisional determination bit, and for each b ^c ₀ , b ^c ₁ ,..., B ^c _(N−1) − It is determined by judging 1 or 1. Next, the re-synthesizer 54 generates a modulated signal replica Ω _{r, O} (t) according to equation (8). Here, Fil (•) is a pulse shaping filter equivalent to the pulse shaping unit 33 of FIG. Next, the re-synthesizer 54 generates a signal R _{r, 01} (t) using equation (9). The re-synthesizer 54 inputs this signal R _{r, 01} (t) to the correlator bank 55.

The output signal of the differentiation circuit 52 is subjected to delay processing (T _D (> T _B )) by the delay element 56 and input to the correlator bank 55. Similarly to the correlator bank 53, the correlator bank 55 uses the signal R _{r, 01} (t) as the reference signal R _r (t), and with respect to the signal delayed by the delay element 56, refer to FIG. The same processing as described is performed.

Recombiner 57, the output signal of the correlator bank 55, produces a signal R _{r, 02} in the same manner as recombiner 54 (t), the input signal R _{r, 02} (t) to the correlator bank 58 To do.

The output signal of the delay element 56 is further subjected to delay processing by the delay element 59 and is input to the correlator bank 58. Similarly to the correlator banks 53 and 55, the correlator bank 58 uses the signal R _{r, 02} (t) as the reference signal R _r (t), and refer to FIG. 7 for the signal delayed by the delay element 59. The same processing as described above is performed.

  In the correlation reception processing unit 18 of FIG. 5, an interference removal circuit may be provided for at least one output signal of the correlator banks 53, 55, and 58. The interference cancellation circuit generates a signal obtained by separating interference components (inter-bus interference and the like) included in a certain signal. The interference cancellation circuit will be described more specifically later (see the description of the interference cancellation circuit 163 in FIG. 10). When providing an interference cancellation circuit for the output signal of the correlator bank 53 or 55, the recombiner 54 or 57 may perform a resynthesis process on the signal after the interference cancellation processing by the interference cancellation circuit. Good (see re-synthesizers 164, 167, 173 and 176 in FIG. 10).

  Next, a case of MIMO transmission will be described with reference to FIGS.

  FIG. 9 is a schematic block diagram showing an example of a transmission system 121 according to another embodiment of the present invention. In the transmission system 121, the signal is transmitted from the transmitter 123 having the transmission units 129 and 131 to the receiver 125 having the reception units 133 and 135 through the MIMO transmission path 127.

  Regarding the transmitter 123, the configurations of the transmission units 129 and 131 are the same as those described with reference to FIG.

  Next, the receiver 125 of FIG. 9 will be specifically described with reference to FIG. FIG. 10 is a diagram illustrating a specific example of the receiver 125 of FIG.

  The receiver 125 includes reception units 133 and 135 and a correlation reception processing unit 137.

  The reception unit 133 includes a reception antenna 141, an analog processing unit 142, and a digital processing unit 143. The digital processing unit 143 includes a digital MIX unit 144, an LPF 145, and a differentiation circuit 146. The reception unit 135 includes a reception antenna 147, an analog processing unit 148, and a digital processing unit 149. The digital processing unit 149 includes a digital MIX unit 151, an LPF 152, and a differentiation circuit 153. The receiving units 133 and 135 perform the same processing as that described for the receiving unit 17 in FIG.

  In the present embodiment, the correlation reception processing unit 137 performs the same processing as the correlation reception processing unit 18 in FIG. However, the re-synthesizers 164, 167, 171 and 174 perform re-synthesizing processing based on the output signal of the interference removal circuit, not the output signal of the correlator bank. Hereinafter, the operation of the correlation reception processing unit 137 will be specifically described.

The correlator bank 161 uses the output signal of the LPF 145 as a reference signal and receives the correlation of the output signal of the differentiating circuit 146 (see FIG. 7). This output signal is assumed to be b ^c ₀₀ , b ^c ₀₁ ,..., B ^c _{0 (N−1)} . Further, the correlator bank 162 uses the output signal of the LPF 152 as a reference signal, and receives the correlation output of the output signal of the differentiating circuit 153. This output signal is assumed to be b ^c ₁₀ , b ^c ₁₁ ,..., B ^c _{1 (N−1)} . For example, in the case of the correlator bank 161, the settings of the T _i and p _i of the correlator banks 161 and 162 are targeted for the transmission path connecting the transmission antenna of the transmission unit 129 in FIG. 9 and the reception antenna 141 in FIG. In the case of the correlator bank 162, the transmission path connecting the transmission antenna of the transmission unit 131 in FIG. 9 and the reception antenna 147 in FIG.

The interference cancellation circuit 163 includes interference components (intersymbol interference components, intersymbol interference components, antennas ₎ included in the signals b ^c ₀₀ ,..., B ^c _{1 (N−1)} generated by the correlator banks 161 and 162. during the interference component, etc.) were separated signals B _00, and generates an _{···, B 1 (N-1} ). For example, if the multipath delay spread is within one symbol period, the interference removal circuit 163 may only remove intersymbol interference and inter-antenna interference. Multipath components within one symbol period are combined with path diversity by a correlator bank. In this case, the transmission path matrix describing the state of intersymbol interference and inter-antenna interference is H, the vector of b ^c _00, ..., B ^c _{1 (N−1)} is β ^c, and B ₀₀ ,. ·, when the vector of the B _{1 (N-1)} is B, because it is beta ^c = H-beta, interference cancellation circuit, to ^{β c, B = H -1 ·} β c = H -1 · H Realized by a circuit that multiplies a matrix H ⁻¹ satisfying β = β.

The re-synthesizer 164 performs re-synthesizing processing based on the signals B ₀₀ ,..., B _{0 (N−1)} (see equations (7) to (9)), and the re-synthesized signal is correlator. Input to bank 165. Similarly to the correlator bank 55 of FIG. 5, the output signal of the differentiation circuit 146 is input to the correlator bank 165 after being delayed by the delay element 166 (T _D (> T _B )). Similarly, the re-synthesizer 167 performs re-synthesizing processing based on the signals B ₁₀ ,..., B _{1 (N−1)} , and inputs the re-synthesized signal to the correlator bank 168. Similarly to the correlator bank 55 in FIG. 5, the correlator bank 168 receives the output signal of the differentiating circuit 146 after being delayed by the delay element 166. The correlator banks 165 and 168 perform correlation reception processing in the same manner as the correlator bank 55 in FIG.

  Interference signals are removed from the signals after the correlation reception processing by the correlator banks 165 and 168 by the interference removal circuit 170 in the same manner as the interference removal circuit 163. The signals processed by the interference cancellation circuit 170 are recombined by recombiners 171 and 174 and input to correlator banks 172 and 175, respectively. In addition, the signals after delay processing of the delay elements 166 and 169 are also subjected to delay processing by the delay elements 173 and 176 and input to the correlator banks 172 and 175, respectively. The correlator banks 172 and 175 perform correlation reception processing in the same manner as the correlator bank 58 in FIG.

  The signal after correlation reception processing by the correlator banks 172 and 175 is subjected to interference removal processing by the interference removal circuit 177.

Next, another example of the embodiment of the present invention will be described with reference to FIG. When the modulation index k _FM is a low modulation index (k _FM << π / (2T _C )), the exponent function part in the equation (6) can be regarded as a substantially constant as in the equation (10). As a result, when k _FM is a low modulation index, equation (6) is greatly simplified as equation (11), and D ₀ (t) can be almost regarded as a linearly modulated CDM signal. .

FIG. 11 is a diagram illustrating an example of the receiver 181 in the MIMO transmission when the modulation index _kFM is a low modulation index, which is another embodiment of the present invention. The configuration of the transmitter in this embodiment is the same as that of the transmitter 123 in FIG.

  The receiver 181 includes reception units 183 and 185 and a correlation reception processing unit 187.

  First, the receiving unit 183 will be described. The receiving unit 183 includes a receiving antenna 189, an analog processing unit 191, and a digital processing unit 193. The reception antenna 189 and the analog processing unit 191 operate in the same manner as the reception antenna 19 and the analog processing unit 21 in FIG. The digital processing unit 193 includes a digital MIX unit 201, an LPF 203, and a differentiation circuit 205. The digital MIX unit 201, LPF 203, and differentiation circuit 205 operate in the same manner as the digital MIX unit 49, LPF 51, and differentiation circuit 53 of FIG. The receiving unit 185 also operates in the same manner as the receiving unit 183.

The correlation reception processing unit 187 includes correlator banks 213 and 215 and an interference removal circuit 217. As described above, when k _FM is a low modulation index, D ₀ (t) can be almost regarded as a linearly modulated CDM signal, so the correlator bank 213 sets the reference signal to 1 (ie, for example, The multiplier 63 in FIG. 7 generates signals b ^c ₀₀ ,..., B ^c _{0 (N−1)} by multiplying p ₀ ^* c ₀ (t), etc. The correlator bank 215 also generates signals b ^c ₁₀ ,..., B ^c _{1 (N−1)} in the same manner as the correlator bank 213.

The interference canceling circuit 217 operates in the same manner as the interference canceling circuits 163, 170, and 177 in FIG. 10, and the interference component (b _-1) is included in each signal from the signals b ^c ₀₀ , ..., b ^c _{1 (N-1).} Inter-symbol interference component, intersymbol interference component, inter-antenna interference component, etc.) are separated to generate signals B ₀₀ ,..., B _{1 (N−1)} .

1 is a schematic block diagram showing an example of a transmission system 1 according to an embodiment of the present invention. It is a figure which shows the specific example of the transmitter 3 of FIG. It is a figure which shows the time relationship of the symbol processed simultaneously by the transmitter 3 of FIG. (A) is a figure which shows an example of the spectrum of (omega) _I (t) before the pulse shaping by the pulse shaping part 33 of FIG. 2, (b) shows an example of the spectrum of (omega) _O (t) after pulse shaping. FIG. It is a figure which shows the specific example of the receiver 5 of FIG. When the transmission path of the impulse response given in (c) is given, the result (a) of detecting the impulse response of the transmission path by the transmission method of the present invention adopting the 1-bit ADC and the 10-bit ADC are changed. It is a figure which shows the result (b) which detected the impulse response of the said transmission line at the time of doing. It is a figure which shows an example of a structure of the correlator banks 53, 55, and 57 of FIG. It is a figure which shows an example of a multipath transmission path. It is a general | schematic block diagram which shows the example of the transmission system 121 which concerns on other embodiment of this invention. It is a figure which shows the specific example of the receiver 125 of FIG. It is a figure which shows an example of the receiver 181 in MIMO transmission in case modulation index _kFM is a low modulation index which is other embodiment of this invention. It is a general | schematic block diagram of the transmission system 301 which performs the transmission of the signal using the conventional MIMO transmission technique and OFDM.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Transmission system, 3 Transmitter, 5 Receiver, 7 Transmission path, 9 Transmission part, 11 Non-linear modulation part, 13 Amplifier part, 17 Reception part, 18 Correlation reception process part, 19 Reception antenna, 21 Analog processing part, 23 Digital Processing unit, 35 FM modulation unit, 37 RF unit, 43 MIX unit, 47 1-bit ADC, 49 Digital MIX unit, 51 LPF, 52 Differentiating circuit, 53, 55, 58 Correlator bank, 54, 57 Recombiner, 121 Transmission System, 123 transmitter, 125 receiver, 129, 131 transmitter, 133, 135 receiver, 137 correlation reception processor, 141, 147 reception antenna, 142, 148 analog processor, 143, 149 digital processor, 144 151 Digital MIX, 145,152 LPF, 146,153 Fine Circuit, 161, 162, 165, 168, 172, 175 Correlator bank, 164, 167, 171, 174 Recombiner, 163, 170, 177 Interference cancel circuit, 181 receiver, 183, 185 receiver, 187 Correlation reception processing Unit, 189, 195 receiving antenna, 191, 197 analog processing unit, 193, 199 digital processing unit, 201, 207 digital MIX unit, 203, 209 LPF, 205, 211 differentiation circuit, 213, 215 correlator bank, 217 interference cancellation circuit ,

Claims (9)

A transmitter having at least one transmission means for transmitting a transmission signal obtained by modulating a source signal from a transmission antenna; and a receiver having at least one reception means for demodulating a reception signal obtained via the reception antenna. In transmission systems,
The transmission means includes modulation means for obtaining the transmission signal by constant envelope modulation of the source signal,
The receiving means includes
First conversion means for converting the received signal into an IF signal;
Having analog-to-digital conversion means for sampling the IF signal to generate an actual sampling signal;
Transmission system.   The transmission system according to claim 1, wherein the source signal is generated by a code division multiplexed signal. The analog / digital conversion means performs 1-bit analog / digital conversion processing for outputting different values based on the amplitude of a signal,
When the signal amplitude is greater than or equal to a predetermined value and smaller than the predetermined value, or when the signal amplitude is greater than the predetermined value and less than or equal to the predetermined value, a different value is output.
The transmission system according to claim 1 or 2. The receiving means includes
Second conversion means for converting the real sampling signal into a complex baseband signal;
Differentiating means for differentiating the complex baseband signal to generate a differentiated complex baseband signal;
Have
The receiver
First correlation receiving means for receiving the differential complex baseband signal as a reference signal using the complex baseband signal as a reference signal, and temporarily determining an output value of the correlation reception to generate a temporary determination bit;
Recombining means for generating a modulated signal replica based on the provisional determination bit and generating a reference signal from the modulated signal replica;
A second correlation receiving means for receiving the differential complex baseband signal in correlation with the reference signal generated by the re-synthesis means;
Having
The transmission system according to any one of claims 1 to 3. When the transmission path when the transmission signal reaches the receiver is a multipath transmission path,
The first correlation receiving means and the second correlation receiving means perform correlation reception for each path of the transmission path, and synthesize an output signal after correlation reception.
The transmission system according to claim 4. The transmitter has a plurality of transmission means, and the receiver has a plurality of reception means;
The transmission signal generated by each transmission means is transmitted using the same carrier frequency simultaneously from the transmission antenna of each transmission means,
Each of the transmission signals is combined via a transmission path, then reaches the receiving antenna of each receiving means,
Each receiving means performs correlation reception for each path of the transmission path with respect to the transmission path connecting each receiving antenna and any one of the plurality of transmitting means.
The receiver includes an interference removal circuit that removes an interference component included in an output value after correlation reception output from each receiving unit.
The transmission system according to claim 1. In a transmitter having at least one transmission means for transmitting a transmission signal obtained by modulating a source signal from a transmission antenna,
Each of the transmission means includes modulation means for nonlinearly modulating the source signal to obtain the transmission signal,
The transmission signal is converted into an IF signal in a receiver that has arrived via a transmission path, and the IF signal is sampled to generate an actual sampling signal.
Transmitter. In a receiver having at least one receiving means for demodulating a received signal obtained via a receiving antenna,
The received signal is a signal obtained by non-linear modulation in the transmitter and reaches the receiver via a transmission line,
Conversion means for converting the received signal into an IF signal;
A receiver having analog-digital conversion means for sampling the IF signal to generate an actual sampling signal. A transmitter having at least one transmission means for transmitting a transmission signal obtained by modulating a source signal from a transmission antenna; and a receiver having at least one reception means for demodulating a reception signal obtained via the reception antenna. A transmission method in a transmission system,
The modulation means of the transmission means performs constant envelope modulation on the source signal to obtain the transmission signal;
A first converting means of the receiving means for converting the received signal into an IF signal;
The analog-to-digital conversion means of the receiving means samples the IF signal to generate an actual sampling signal;
A second converting means of the receiving means for converting the real sampling signal into a complex baseband signal;
The differentiating means of the receiving means differentiates the complex baseband signal to generate a differentiated complex baseband signal;
Correlation receiving means of the receiver correlatively receiving the differential complex baseband signal;
Including transmission method.