JP2007166424A - Repeating device, relay method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a simple configuration and high performance coexist in a frequency division multiple access system. <P>SOLUTION: This repeating device is equipped with a first filter which receives an analog signal wherein frequency division multiplexing of a plurality of channels is performed and restricts the frequency band of the received signal, an A/D converter for converting the received analog signal whose frequency band is restricted into a digital reception signal, a band divider for dividing the digital reception signal into a plurality of signals by channel, a signal operation portion which performs a predetermined signal operation processing by channel with respect to the plurality of signals divided by channel, a band composition portion for compositing a plurality of signals on a channel-by-channel basis to which the signal operation processing is applied into a frequency-division-multiplexed digital transmission signal, and a D/A converter for converting the composite digital transmission signal into an analog transmission signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a signal processing technique for a frequency-multiplexed signal (frequency multiplexed signal) used in the communication field, and more particularly to a technique for filtering a signal of a desired bandwidth from a frequency multiplexed signal.

  In wireless communication and wired communication, various multiple access methods are used for effective use of communication resources. For example, the frequency multiple access method (FDMA) is arranged such that a plurality of users (information / channels) do not overlap each other in the frequency axis direction. In a transmission apparatus, a reception apparatus, a relay apparatus, and the like that employ such a frequency multiple access method, frequency conversion and a filter play an important role in order to synthesize and separate signals of each channel.

By the way, in a frequency multiple access relay device or the like, as the number of multiplexed channels increases, it is necessary to prepare a corresponding number of frequency converters and filters (see, for example, Patent Document 1). Therefore, there is a problem that the number of circuit components increases as the number of channels increases, and the cost increases in proportion to the number of channels. In addition, when a frequency bandwidth signal needs to be changed for each channel of a frequency multiple access method, a complicated circuit configuration is required, which increases the size and cost of the relay device.
JP-A-7-38532

  As described above, the conventional relay apparatus, relay method, and computer program have a problem that the circuit configuration becomes complicated as the number of multiplexed channels increases, resulting in an increase in the size and cost of the apparatus.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a relay device, a relay method, and a computer program that achieve both a simple configuration and high performance in a frequency multiple access method. .

  In order to achieve the above-described object, the relay apparatus of the present invention includes a filter that receives an analog reception signal in which a plurality of channels are frequency-multiplexed and limits the frequency band of the reception signal, and the frequency band is limited. An A / D converter that converts an analog received signal into a digital received signal, a band dividing unit that divides the digital received signal into a plurality of signals in units of channels, and a frequency multiplex of the plurality of signals in the divided channels A band synthesizing unit that synthesizes the synthesized digital transmission signal, and a D / A conversion unit that converts the synthesized digital transmission signal into an analog transmission signal.

  The relay method of the present invention also includes a step of receiving an analog reception signal in which a plurality of channels are frequency-multiplexed and limiting the frequency band of the reception signal, and a digital reception of the analog reception signal having a limited frequency band. A step of converting the received signal into a signal; a step of dividing the digital received signal into a plurality of signals in units of channels; and a step of executing predetermined signal arithmetic processing in units of the channels on the plurality of signals divided in units of channels And a step of synthesizing a plurality of signals for each channel on which signal arithmetic processing has been performed into a frequency-multiplexed digital transmission signal, and a step of converting the synthesized digital transmission signal into an analog transmission signal. ing.

  Furthermore, the computer program of the present invention includes a first filter that receives an analog reception signal in which a plurality of channels are frequency-multiplexed and limits the frequency band of the reception signal, and an analog having a limited frequency band. An A / D converter that converts the received signal into a digital received signal, a band divider that divides the digital received signal into a plurality of signals in units of channels, and a plurality of signals divided in units of channels A signal calculation unit that performs predetermined signal calculation processing in units of channels, a band combination unit that combines a plurality of signals in units of channels for which signal calculation processing has been performed, into a frequency-multiplexed digital transmission signal, and combined digital And a D / A converter that converts the transmission signal into an analog transmission signal.

  ADVANTAGE OF THE INVENTION According to this invention, in a communication apparatus of a frequency multiple access system, simple structure and high performance can be reconciled.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a relay apparatus according to the first embodiment of the present invention. In the following description, it is assumed that a frequency multiplexed signal having M channels is relayed.

  As shown in FIG. 1, the relay apparatus 1 of this embodiment includes a front end unit 11 connected to an antenna ANT1, a low-pass filter (LPF) unit 12, an A / D conversion (ADC) unit 13, a first filter bank. 14, a signal calculation unit 15, a second filter bank unit 16, a D / A conversion (DAC) unit 17, an LPF unit 18, and a final stage unit 19 connected to the antenna ANT 2.

  The front end unit 11 is a receiving unit that receives a high-frequency signal that is frequency-multiplexed from a signal received from the antenna ANT1. The front end unit 11 includes a filter (high-pass filter / band-pass filter) that removes image frequency components and passes a frequency-multiplexed signal in a desired frequency band, and a high-frequency amplifier that amplifies the frequency-multiplexed signal to a predetermined level. ing. Moreover, you may provide the frequency conversion part which converts the signal taken in from the antenna into an intermediate frequency etc.

  The LPF unit 12 is an anti-aliasing filter for A / D conversion. The LPF unit 12 operates to remove a signal having a frequency equal to or higher than the Nyquist frequency of the subsequent A / D conversion from the frequency multiplexed signal received by the front end unit 11.

  The ADC unit 13 is an A / D converter that converts an analog frequency multiplexed signal that has passed through the LPF unit 12 into a digital signal. The ADC unit 13 acts to convert a desired entire frequency multiplexed signal entire region (the entire signal region that has passed through the front end unit 11 and the LPF unit 12) into a digital signal.

  The first filter bank unit 14 converts the digital signal output from the ADC unit 13 into a time-series signal divided into a predetermined number of channels M (N ≧ M) using inverse Fourier transform. It is a filter. The configuration of the first filter bank unit 14 can select an optimum method according to the contents of the signal calculation unit 15 at the subsequent stage, and uses, for example, DFT (Discrete Fourier Transform) or FFT (Fast Fourier Transform). (See “Multi-rate signal processing technology” published by Shojido and Hitoshi Kiya). Note that any transform other than DFT or FFT can be applied as long as the transform has an orthogonal basis depending on the application.

  The signal calculation unit 15 is a digital signal processing unit that separately performs a predetermined calculation process on each of the time-series signals band-divided by the first filter bank unit 14. Since the signal input to the signal calculation unit 15 is a band-divided (channel-divided) digital signal, the signal calculation unit 15 implements various signal calculation processes for each channel by predetermined numerical calculation processing.

  The second filter bank unit 16 is a digital filter that performs a Fourier transform on each digital signal in units of channels processed by the signal calculation unit 15 to synthesize a band, and further synthesizes all channels into a frequency-multiplexed digital signal. is there. The second filter bank unit 16 has a configuration corresponding to the first filter bank unit 14.

  The DAC unit 17 is a D / A converter that collectively converts digital frequency-multiplexed signals output from the second filter bank unit 16 into analog frequency-multiplexed signals. The DAC unit 17 corresponds to the ADC unit 13 and collectively converts the entire digital frequency-multiplexed signal into analog.

  The LPF unit 18 is a filter that removes harmonics and the like higher than the Nyquist frequency from the analog frequency multiplexed signal output from the DAC unit 17.

  The final stage unit 19 is a transmission unit that amplifies the frequency multiplexed signal that has passed through the LPF unit 18 to a predetermined power and transmits the amplified signal through the antenna ANT2. The final stage unit 19 includes a broadband power amplifier that covers the entire region of the frequency-multiplexed analog signal, and a filter (low-pass filter / band-pass filter) that removes spurious signals and the like from the amplified high-frequency signal. Note that the final stage unit 19 may include a frequency conversion unit that converts the frequency from the intermediate frequency to a predetermined transmission frequency.

  Next, the first filter bank unit 14 and the second filter bank unit 16 in the relay device 1 of this embodiment will be described in detail with reference to FIGS. 2 and 3. FIG. 2 is a block diagram showing the configuration of the first filter bank unit 14 of this embodiment, and FIG. 3 is a block diagram showing the configuration of the second filter bank unit 16 of this embodiment. In the relay apparatus 1 of this embodiment, the number of band divisions (number of channels) is M (N ≧ M), but in FIG. 2 and FIG. As shown in FIG. 2, the first filter bank unit 14 of this embodiment includes delay elements 21 to 23, decimators 31 to 34, filters 41 to 44, and an IFFT unit 51. As shown in FIG. 3, the second filter bank unit 16 of this embodiment includes an FFT unit 52, filters 61 to 64, interpolators 71 to 74, delay elements 81 to 83, and adders 91 to 93. Yes.

  The delay elements 21 to 23 are signal delay means connected in series with each other and connected to the output of the ADC unit 13 at one end. Inputs of decimators 31 to 34 are connected to both ends of the delay elements 21 to 23, respectively. The delay elements 21 to 23 act to delay the digital signal input from the ADC unit 13 in a stepwise manner and perform serial-to-parallel conversion (serial-parallel conversion) from serial to N columns of parallel.

  Decimators 31 to 34 are downsampler elements whose inputs are connected to one end of delay elements 21 to 23 and outputs are connected to filters 41 to 44, respectively. Decimators 31 through 34 thin out a predetermined number of samples from the input digital signal. Decimators 31 to 34 include, for example, a cut-off filter and a down sampler. Decimators 31 to 34 independently thin out a predetermined number of samples of the output signal of ADC unit 13 and the signal delayed through delay elements 21 to 23 and output them to filters 41 to 44, respectively.

  The filters 41 to 44 are a group of filters that perform band limitation, in which each input is connected to the output of the corresponding decimator 31 to 34. In the example shown in FIG. 2, the filters 41 to 44 are shown as having a filter function of H (z). The filters 41 to 44 function to independently filter signals obtained by thinning out a predetermined number of samples by the decimators 31 to 34, respectively.

  The IFFT 51 is a fast inverse Fourier transformer in which the outputs of the filters 41 to 44 are connected to the input. The IFFT 51 performs inverse Fourier transform processing on each signal that has been serial-parallel converted, thinned, and filtered. As a result, the IFFT 51 outputs M digital time-series signals divided for each channel to the signal calculation unit 15.

  Next, the second filter bank unit 16 will be described.

  The FFT unit 52 is a fast Fourier transformer that performs a Fourier transform process on the output of the signal calculation unit 15. The FFT unit 52 performs a Fourier transform process on each signal that has undergone signal computation processing for each channel. As a result, the FFT unit 52 outputs N-band signals subjected to band synthesis to the filters 61 to 64.

  The filters 61 to 64 are a group of filters each having an input connected to the output of the FFT unit 52 and each output connected to the inputs of the interpolators 71 to 74. The filters 61 to 64 function to synthesize the signals for each channel output from the FFT unit 52 into signals for each channel.

  Interpolators 71 to 74 are upsampler elements whose inputs are connected to the outputs of filters 61 to 64 and whose outputs are connected to the input of delay element 81 and one input of adders 91 to 93, respectively. The interpolators 71 to 74 operate to interpolate a predetermined number of samples between samples of the input digital signal. The interpolators 71 to 74 include, for example, an upsampler and an imaging removal filter. The interpolators 71 to 74 independently interpolate a predetermined number of samples and output the digital signals output from the filters 61 to 64, respectively.

  The delay elements 81 to 83 are signal delay means whose input is connected to the output of the interpolator 71 or the outputs of the adders 91 and 92 and the other end is connected to one input of the adders 91 to 93. In the adders 91 to 93, one input is connected to the outputs of the delay elements 81 to 83, the other input is connected to the outputs of the interpolators 72 to 74, and the outputs are the delay elements 82 and 83 and the DAC unit as the output destination. 17 is an adder connected to 17 inputs. That is, the delay elements 81 to 83 and the adders 91 to 93 are alternately connected in series, and the outputs of the interpolators 71 to 74 are connected to the input of the delay element 81 and one input of the adders 91 to 93, respectively. The input of the DAC unit 17 is connected to the output of the device 93. The delay elements 81 to 83 and the adders 91 to 93 operate to delay the parallel signals in units of channels output from the interpolators 71 to 74 in a stepwise manner and convert them into serial signals.

  Here, the operation of the relay apparatus 1 of this embodiment will be described.

  A signal received by the antenna ANT1 is converted into a desired frequency band by the front end unit 11, band-limited, and input to the LPF unit 12. When receiving a signal from the front end unit 11, the LPF unit 12 performs filtering to remove a frequency component equal to or higher than the Nyquist frequency in order to prevent aliasing in the subsequent ADC unit 13. The ADC unit 13 collectively performs analog / digital conversion on the entire area of the input signal (frequency-multiplexed signal) and inputs it to the filter bank unit 14.

  The first filter bank unit 14 converts the input digital signal into a time-series signal that is band-divided for each channel and outputs the time-series signal to the signal calculation unit 15. Specifically, the signal output from the ADC unit 13 is input to the delay elements 21 to 23 connected in series, and the serial-parallel-converted N is output from the output of the ADC unit 13 and the outputs of the delay elements 21 to 23. Output as a column signal. The serial / parallel converted signal is input to the decimators 31 to 34. Decimators 31 to 34 are generally represented as “↓ N”. That is, the decimator represented by “↓ N” has a decimation rate of N and outputs one sample for the input sample N. In other words, thinning out is performed in units of N samples. This decimated signal is input to the filters 41 to 44 and band-limited, and then is output to the signal calculation unit 15 as a time-series signal divided into M (N ≧ M) channels by IFFT processing. . The signal calculation unit 15 performs predetermined signal processing.

  M (N ≧ M) time-series signals for each channel output from the signal calculation unit 15 are band-combined by FFT processing in the FFT unit 52 and then input to the filters 61 to 64 as N-sequence signals. The The signals inputted to the filters 61 to 64 are subjected to interpolator processing by the interpolators 71 to 74. The interpolators 71 to 74 are generally represented as “↑ N”. That is, the interpolator represented by “↑ N” has an interpolation rate of N, and N samples are output for one output sample. In other words, interpolation is performed in units of N samples. The interpolated signal is input to one input of the delay element 81 and the adders 91 to 93, subjected to parallel-serial conversion, frequency-multiplexed, and input from the output of the adder 93 to the DAC unit 17.

  The DAC unit 17 collectively converts the input digital frequency multiplexed signals into analog frequency multiplexed signals. From the analog signal, the LPF unit 18 removes a repetitive component higher than the Nyquist frequency. The signal that has passed through the LPF unit 18 is converted and amplified to a desired frequency by the final stage unit 19 and then transmitted from the antenna ANT2.

  Here, with reference to FIG. 4A thru | or FIG. 4D, the filter characteristic of the relay apparatus 1 of this embodiment is demonstrated. 4A to 4D are conceptual diagrams showing the filter function of this embodiment.

  In the relay apparatus 1 of this embodiment, the front end unit 11 has a so-called reception function such as amplification and frequency conversion. Such a receiving unit is designed to receive only a frequency band of a desired reception band in order to prevent a local oscillation frequency or the like from entering. Specifically, the image frequency is designed to be cut by a band pass filter or a high pass filter. FIG. 4A shows a state in which a low frequency component corresponding to the image frequency is cut as a result of the reception signal passing through the front end portion.

  Next, the LPF unit 12 functions as an anti-aliasing filter to prevent so-called aliasing noise. Therefore, high frequency components of the received signal are cut. FIG. 4B shows a state where high frequency components are cut. FIG. 4B also shows a state in which the image component that has not been partitioned by the front end portion 11 is folded back and remains. The operation so far is an operation as an analog filter.

  When the signal that has passed through the LPF unit 12 is converted into a digital signal by the ADC unit 13, the frequency that is equal to or higher than the sampling frequency fs is folded back to become an alias component. FIG. 4C shows the state of the received signal that is folded back to the sampling frequency fs or lower.

  When a digital frequency multiplexed signal is input, the filter bank unit 14 performs band division on a channel basis. FIG. 4D shows a state of the output that is band-divided into an elongated rectangular shape. Here, if the signals of the image component and the alias component are removed, the rectangular filtering characteristic can be obtained by the band division filter characteristic in the filter bank unit 14. In FIG. 4D, the filter characteristics finally obtained as the output of the filter bank unit 14 are indicated by bold lines.

  Thus, according to the relay apparatus 1 of this embodiment, due to the interaction between the front end unit 11 and the LPF unit 12 that perform analog filtering, the ADC unit 13 that performs digital filtering, and the first filter bank unit 14, Excellent filter characteristics (channel selection characteristics) can be obtained.

  Further, according to the relay device 1 of this embodiment, the first and second filter bank units 14 and 16 perform band division and band synthesis, so that the signal calculation unit 15 performs processing even when the number of channels increases. The amount does not change, and the configuration of the signal calculation unit 15 can be simplified.

  Subsequently, the signal calculation unit 15 of this embodiment will be described in detail with reference to FIGS. FIG. 5 is a block diagram showing the configuration of the signal calculation unit 15 of this embodiment, FIG. 6 is a schematic diagram showing the gain control function in the relay device 1 of this embodiment, and FIG. 7 is the frequency conversion function of this embodiment. It is a schematic diagram which shows. The signal calculation unit 15 of this embodiment realizes level adjustment between channels (power level adjustment).

  As shown in FIG. 5, the signal calculation unit 15 of this embodiment includes power measurement units 121 to 124, a level adjustment unit 131, and a matrix type frequency conversion unit 132 separately prepared for each channel (each subchannel). And a control unit 133.

  The power measuring units 121 to 124 are provided for each channel, each input is connected to each output of the first filter bank unit 14, and each output is connected to each input of the level adjusting unit 131. It is a signal detection means which measures. The power measuring units 121 to 124 pass the respective detection results to the control unit 133. The power level for each channel can be calculated using a method based on the estimated value from the received intensity of the channel output signal or a method based on the maximum value of the power spectrum of the channel signal.

  The level adjustment unit 131 is a signal control unit that is connected to the output of each of the power measurement units 121 to 124 and adjusts the power level for each channel. The level adjustment unit 131 outputs a signal for each channel on which the power level has been adjusted to each input of the matrix type frequency conversion unit 132. The level adjustment unit 131 operates to adjust a level difference between channels due to fading, a path difference in a propagation path, and the like. For the adjustment of the power level, a method of controlling the gain of the amplifier, a method of controlling the amount of reduction of the attenuator, or the like can be used.

  The matrix type frequency conversion unit 132 is a signal conversion unit that has an input connected to the output of the level adjustment unit 131 and converts the arrangement of the channels on the frequency axis. The matrix type frequency conversion unit 132 outputs the converted signal for each channel to the input of the second filter bank unit 16.

  The control unit 133 is a signal control instruction unit that obtains an adjustment amount of the power level in units of channels based on the power levels detected by the power measurement units 121 to 124 and instructs the level adjustment unit 131 to make adjustments.

  Next, the operation of the signal calculation unit 15 of this embodiment will be described with reference to FIGS. 6 and 7. Upon receiving a channel unit signal from the first filter bank unit 14, the power measurement units 121 to 124 measure and calculate the power level (reception power) for each channel. For example, if the reception level differs for each channel due to fading that occurs before reaching the antenna ANT1, the power level may differ for each channel when the first filter bank unit 14 performs band division (FIG. 6). Waveform shown by broken line). The power measuring units 121 to 124 pass the power level information for each channel to the control unit 133. Based on the received power level information, the control unit 133 specifies a channel to increase the power level (or a channel to be decreased), calculates each amplification amount (attenuation amount), and performs power level control for each channel. The level adjustment unit 131 is instructed. The level adjustment unit 131 adjusts the amplification level (attenuation level) for each channel based on an instruction from the control unit 133, and outputs the adjustment level to the matrix type frequency conversion unit 132.

  The matrix type frequency converter 132 converts the input channel arrangement. For example, as shown in FIG. 7, the matrix type frequency conversion unit 132 performs conversion for switching the fifth channel and the Mth channel. This conversion may be stored in advance in the matrix type frequency conversion unit 132 or may be performed based on an instruction from the control unit 133 or the like. The frequency-converted signal for each channel is output to each input of the second filter bank unit 16.

The frequency conversion of the matrix type frequency conversion unit 132 is realized by matrix calculation. For example, the output signal of the channel is S _k (n) (where k is the channel number and n is the sample number). Further, if the output signal frequency-converted by the matrix-type frequency converter 132 is Y _k (n) and the matrix indicating the frequency conversion of the matrix-type frequency converter 132 is M, the input / output of the matrix-type frequency converter 132 is It can be expressed as follows.

  Note that, as a property of the frequency conversion matrix M, the elements are {0, 1}, and only one 1 can be entered at the same time in the row direction and the column direction, and the other is 0. If M is a unit matrix, it means that frequency conversion is not performed.

  According to the relay device 1 of this embodiment, the signal calculation unit 15 adjusts the power level as shown in FIG. 6 to make the power level between channels uniform. Thereby, the dynamic range of the DAC section 17 at the subsequent stage can be effectively utilized. In terms of analog signal processing, signal degradation due to intermodulation (IM) can be suppressed by uniformly adjusting the power level between channels.

  Also, according to the relay device 1 of this embodiment, since the digital signal band-divided by the first filter bank unit 14 is arithmetically processed, all the arithmetic processing means do not depend on the number of channels and Arithmetic can be realized. This makes it possible to suppress an increase in hardware cost even when the number of channels to be processed increases.

  Furthermore, according to the relay apparatus 1 of this embodiment, since the frequency conversion of the channel is realized by the matrix type frequency conversion unit on the digital signal, it is possible to perform complex frequency conversion with a simple configuration.

  Next, a relay device according to the second embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a block diagram illustrating a configuration of the signal calculation unit 215 in the relay apparatus 2 according to the second embodiment of the present invention, and FIG. 9 is a schematic diagram illustrating a power spectrum for explaining the function of the unnecessary wave identification unit according to this embodiment. FIG. 10 and FIG. 10 are conceptual diagrams showing the unnecessary wave removing function of this embodiment.

  In the relay device 2 of the second embodiment, only the signal calculation unit 15 of the relay device 1 of the first embodiment shown in FIGS. 1 to 3 is replaced with a signal calculation unit 215 shown in FIG. Therefore, in FIGS. 8 to 10, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, the signal calculation unit 215 identifies channels individually and realizes removal of unnecessary channels.

  As shown in FIG. 8, the signal calculation unit 215 of this embodiment includes an unnecessary wave identification unit 221 to 224, an unnecessary wave removal unit 231, a matrix type frequency conversion unit 132, and a control that are individually prepared for each channel. Part 233.

  The unnecessary wave identifying units 221 to 224 are provided for each channel, and each input is connected to each output of the first filter bank unit 14, and each output is connected to each input of the unnecessary wave removing unit 231. It is the signal detection means to identify. As a specific example, the unnecessary wave identifying units 221 to 224 identify whether a channel signal is a terrestrial digital broadcast wave or a conventional analog television broadcast wave, and pass the results to the control unit 233. There are various methods for identifying the channel. Specifically, a method of detecting the number of carrier peaks, a method of detecting whether digital demodulation is successful, or the like can be used.

  The unnecessary wave removing unit 231 is a signal control unit that removes signals in units of channels by connecting inputs to the outputs of the unnecessary wave identifying units 221 to 224, respectively. The unnecessary wave removal unit 231 outputs a signal for each channel from which predetermined channel removal has been performed, to each input of the matrix type frequency conversion unit 132. For example, a method of removing all the symbol values of a digital signal can be used for signal removal in units of channels.

  The control unit 233 is a signal control instruction unit that instructs the unnecessary wave removing unit 231 to remove the channel when the channel is an analog broadcast wave based on the identification result detected by the unnecessary wave identifying units 221 to 224.

  Here, a method of unnecessary wave identification by the unnecessary wave identification unit 221 will be described. As shown in FIG. 9, the power spectrum of the terrestrial digital TV broadcast signal and the power spectrum of the analog TV broadcast signal have different spectrum waveforms. That is, in the power spectrum of an analog TV broadcast signal, the peak of the power spectrum appears in the frequency domain corresponding to the video signal, color signal, and audio signal. On the other hand, in the power spectrum of the terrestrial digital TV broadcast signal, the waveform appears in a trapezoidal shape. Therefore, it is possible to identify digital broadcast waves and analog broadcast waves by identifying the characteristics of the power spectrum waveform for each channel. Specifically, it is possible to define an analog TV broadcast that has three peaks in the band and whose power fluctuation in the band is equal to or greater than a predetermined value. On the other hand, it is possible to define a terrestrial digital broadcast that has a power fluctuation within a band equal to or less than a predetermined value.

  As another method for identifying unnecessary waves, signal processing can be performed on the time axis. That is, when the amplitude distribution approximately follows a Gaussian distribution, it can be defined as a terrestrial digital TV broadcast, and otherwise it can be defined as an analog TV broadcast. In addition, when an analog TV broadcast synchronization signal is detected from a signal on the time axis, it can be defined as an analog TV broadcast, otherwise it can be defined as a terrestrial digital TV broadcast. Further, by proceeding to the demodulation, if the MER characteristic is equal to or less than a predetermined value, it can be identified as a terrestrial digital TV broadcast, otherwise it can be identified as an analog TV broadcast. It is also possible to detect and identify TMCC (Transmission and Multiplexing Configuration Control) of terrestrial digital TV broadcasting. Such unnecessary wave identification can improve identification accuracy by making a comprehensive judgment using individual identification information.

  Subsequently, the operation of the signal calculation unit 215 of this embodiment will be described with reference to FIGS. 9 and 10. Here, as an example, a description will be given assuming that the broadcast wave of analog TV broadcast is an unnecessary wave among terrestrial digital TV broadcast and analog TV broadcast.

  The output of the first filter bank unit 14 is input to unnecessary wave identification units 221 to 224. The unnecessary wave identifying units 221 to 224 identify whether or not the input channel unit signal is a relay target of the relay device 2. The type of signal identified by the unnecessary wave identifying units 221 to 224 is transmitted to the control unit 233. The control unit 233 instructs the unnecessary wave removal unit 231 to remove unnecessary channels based on the received type for each channel. The unnecessary wave removal unit 231 removes a signal identified as an unnecessary wave in units of channels. As a result, the signal data identified as an unnecessary wave is replaced with 0. The signal from which unnecessary waves are removed is input to the matrix type frequency converter 132 and subjected to predetermined frequency conversion and the like. The signal subjected to frequency conversion or the like is input to the second filter bank unit 16.

  Here, FIG. 10 shows how unnecessary waves are removed according to this embodiment. As shown in FIG. 10, when the unnecessary wave (broken line part) is removed by the unnecessary wave removing unit 231, the frequency spectrum of the part is removed and output. According to the relay device 2 of this embodiment, since unnecessary waves are identified and relayed, unnecessary radio wave radiation can be prevented. Specifically, when only the broadcast wave of the terrestrial digital broadcast is relayed, even if the broadcast wave of the analog broadcast is received by the front end unit 11, only the analog broadcast wave can be removed and relayed. As a result, it is possible to prevent the ghost phenomenon on the receiving side and maintain the signal quality on the receiving side.

  Next, with reference to FIG. 11 and FIG. 12, a relay device according to a third embodiment of the present invention will be described. FIG. 11 is a block diagram showing the configuration of the signal calculation unit 315 in the relay device 3 according to the third embodiment of the present invention, and FIG. 12 is a schematic diagram for explaining the channel identification function of this embodiment.

  In the relay device 3 of the third embodiment, only the signal calculation unit 15 of the relay device 1 of the first embodiment shown in FIGS. 1 to 3 is replaced with a signal calculation unit 315 shown in FIG. Therefore, in FIG. 11 and FIG. 12, the same components as those in the first and second embodiments are denoted by the same reference numerals, and redundant description is omitted. The signal calculation unit 315 of this embodiment realizes the detour removal for each channel.

  As shown in FIG. 11, the signal calculation unit 315 of this embodiment includes channel estimation units 321 to 324 prepared individually for each channel, a total channel estimation unit 331, and a wraparound prepared individually for each channel. Cancellers 341 to 344, a matrix type frequency converter 132, and a controller 333 are provided.

  Channel estimators 321 to 324 are provided for each channel. Each input is connected to each output of the first filter bank unit 14, and each output is connected to each input of the overall channel estimator 331. It is a signal detection means which estimates (transmission path is estimated). Channel estimation units 321 to 324 pass the respective detection results to control unit 333.

  As a channel estimation method in the channel estimation units 321 to 324, for example, the following method can be used. That is, in the first channel estimation method, in a communication system employing orthogonal division multiplexing (OFDM) or the like, a pilot signal is inserted at a predetermined carrier position of a transmission signal, and the pilot signal is extracted from the received signal and propagated. In this method, a transfer function of a path is estimated and an impulse response of the propagation path is estimated from the transfer function. The second channel estimation method is a method that uses a so-called guard interval in a communication system that employs orthogonal division multiplexing (OFDM) or the like. In this method, the received signal is held for a certain period of time as a time signal, and channel estimation is realized by performing a correlation operation between the held signal and the received signal. The third channel estimation method is a method of estimating a delay profile by time-averaging the power spectrum of a received signal and then performing an inverse Fourier transform process. In this method, the level of the delayed wave and the interval between the delayed waves are fixed, but the phase of each delayed wave is not fixed. Therefore, the phase of the delayed wave is estimated under the minimum phase condition. The fourth channel estimation method is a method of estimating by using a predetermined known signal sequence and performing loss calculation with this known progression sequence.

  The total channel estimation unit 331 is a signal control unit that is connected to the outputs of the channel estimation units 321 to 324, respectively, and corrects channel estimation for each channel. The total channel estimation unit 331 outputs a signal for each channel on which channel estimation correction has been performed to each input of the corresponding wraparound cancellers 341 to 344. The overall channel estimation unit 331 operates to improve the channel estimation accuracy by performing correction using the channel responses estimated by the independent individual channel estimation units 321 to 324.

  The control unit 333 instructs the overall channel estimation unit 331 to correct the channel estimation based on the channel estimation results estimated by the channel estimation units 321 to 324, and removes the wraparound signal for each channel to the wraparound cancellers 341 to 344. Is a signal control instruction means for instructing

  The wraparound cancellers 341 to 344 are signal control means for removing the wraparound signal independently for each signal for each channel based on an instruction from the control unit 333. The wraparound cancellers 341 to 344 input the signals from which the wraparound signal is removed to the matrix type frequency converter 132.

  Next, the operation of the signal calculation unit 315 of this embodiment will be described with reference to FIG.

  The first filter bank unit 14 performs IFFT processing for each channel and outputs the result to the channel estimation units 321 to 324. The channel estimation units 321 to 324 perform channel estimation processing for each channel and pass the estimation result to the control unit 333. Specifically, the channel estimation units 321 to 324 calculate a complex impulse response (transmission path transfer function) from the IFFT-processed signal. The control unit 333 instructs the general channel estimation unit 331 to correct the estimation result based on the channel estimation result (transfer function) for each channel.

  The total channel estimation unit 331 corrects the corrected complex impulse response of the channel and corrects it, thereby improving the estimation accuracy of the complex impulse response of the channel. For example, if the propagation path does not depend on the frequency, or if there is no dependence between adjacent channels or is negligible, the complex impulse responses of all channels are the same. In such a propagation path, the overall channel estimation unit 331 performs averaging correction processing on the complex impulses of all the channels, and wraps the averaged complex impulse responses in the cancellers 341 to 344. Used for cancellation processing.

  Also, in an orthogonal frequency division (OFDM) system, it is theoretically difficult to perform channel estimation of side lobes outside the signal band based on pilot signals. Therefore, interpolation processing using both end portions (edge portions) of the channel is also effective as the correction processing.

The channel signal output from the overall channel estimation unit 331 is input to the wraparound cancellers 341 to 344, and the corrected complex impulse response is input to the wraparound cancellers 341 to 344 via the control unit 333. Based on the complex impulse response corrected by the overall channel estimation unit 331, the wraparound cancellers 341 to 344 directly receive from the relay transmission antenna (antenna ANT2) from the relay transmission antenna (antenna ANT2). A component that wraps around the antenna ANT1) is suppressed. The signal in which the wraparound signal is suppressed is input to the matrix type frequency converter 16 for each channel.
A specific operation of the wraparound cancellers 341 to 344 will be described. The complex impulse response of the propagation path between the parent transmitter side and the repeater and the complex impulse response of the return path from the transmission antenna of the repeater to the reception antenna are output from the total channel estimation unit 331. In other words, the complex impulse responses of these propagation paths are superimposed with the propagation response of general frequency selective fading and the propagation path response due to wraparound. Therefore, the wraparound cancellers 341 to 344 separate a general frequency selective fading propagation path response from a propagation path response due to wraparound. Next, the wraparound cancellers 341 to 344 calculate filter tap coefficients for wraparound cancellation from complex impulse responses that are propagation path responses due to wraparound. The wraparound cancellers 341 to 344 convolve the filter tap coefficients for wraparound cancellation with respect to the time series signals of the outputs of the first filter bank unit 14, and output the outputs of the first filter bank unit 14. A sneak component is suppressed from the time-series signal (see, for example, JP-A-11-35160).

  Note that the wraparound canceller is required when the reception frequency and transmission frequency of the repeater 3 are the same, so the matrix type frequency converter 132 basically outputs a signal without converting anything. (Outputs through pass-through). Therefore, the matrix type frequency converter 132 may be omitted.

  According to the relay device 3 of this embodiment, since channel estimation is corrected using a plurality of channels, the performance of wraparound cancellation can be improved.

  Next, a relay device 4 according to a fourth embodiment of the present invention will be described with reference to FIG. 13 and FIGS. 14A to 14C. FIG. 13 is a block diagram illustrating the configuration of the signal calculation unit 415 in the relay device 4 according to the fourth embodiment of the present invention, and FIGS. 14A to 14C are schematic diagrams illustrating the frequency redistribution function according to the fourth embodiment. is there.

  The relay device 4 of the fourth embodiment is obtained by replacing only the signal calculation unit 15 of the relay device 1 of the first embodiment shown in FIGS. 1 to 3 with a signal calculation unit 415 shown in FIG. Therefore, in FIG. 13 and FIGS. 14A to 14C, the same components as those in the first to third embodiments are denoted by the same reference numerals, and redundant description is omitted. The signal calculation unit 415 of this embodiment realizes an arrangement change on the frequency axis of a segment for each channel (information unit in the channel).

  As illustrated in FIG. 13, the signal calculation unit 415 of this embodiment includes signal selection units 421 to 424, a matrix type frequency conversion unit 132, and a control unit 433 that are individually prepared for each channel.

  The signal selectors 421 to 424 are provided for each channel, each input is connected to each output of the first filter bank unit 14, and each output is connected to the input of the matrix type frequency converter 132. Signal selection means for selecting a channel and a segment for each channel. The signal selection units 421 to 424 pass the respective identification results to the control unit 433.

  The segments selected by the signal selection units 421 to 424 are information units (signal units) that are further finely divided into frequency units in the channel. Taking terrestrial digital TV broadcasting as an example, terrestrial digital TV broadcasting adopts an orthogonal frequency division (OFDM) system in which one channel (subchannel) is divided into 13 segments. In this case, the number of segments occupied by the transmission target can be freely defined according to the amount of information to be transmitted. For example, as an application for terrestrial digital TV broadcasting, provision of a service using only one central segment among 13 segments is scheduled. Here, if the transmission target of only one segment is information limited to a closed space such as a building or an underground mall, the frequency bands for the remaining 12 segments are not effectively used in the closed space. The signal calculation unit 415 of this embodiment assumes such a case and enables transmission of only an arbitrary segment and release of an arbitrary segment.

  The matrix type frequency conversion unit 432 corresponds to the matrix type frequency conversion unit 132 of the first embodiment and converts the arrangement of the input channels. In addition, the matrix type frequency conversion unit 432 of this embodiment also performs an operation of performing frequency conversion (frequency position conversion) in segment units in the channel. The frequency-converted signal for each channel is output to each input of the second filter bank unit 16.

  The control unit 433 is signal control instruction means for instructing the matrix type frequency conversion unit 132 to perform frequency conversion of a predetermined channel and a predetermined segment based on the results identified by the signal selection units 421 to 424.

  Next, the operation of the signal calculation unit 415 of this embodiment will be described with reference to FIGS. 14A to 14C. The output of the first filter bank unit 14 is input to the signal selection units 421 to 424.

  The signal selection units 421 to 424 extract only signal components (segments) having a desired bandwidth from the channel signals output from the first filter bank unit 14. FIG. 14A shows a state where only a frequency band for one segment is selected for each channel. The signal selection units 421 to 424 pass the result of the signal selection process to the control unit 433.

  The control unit 433 instructs the matrix type frequency conversion unit 432 to execute a predetermined frequency rearrangement process. When the control unit 433 instructs to output only the selected segment with the same frequency arrangement, the matrix type frequency conversion unit 432 does not perform special frequency conversion and outputs the input signal as it is. As a result, as shown in FIG. 14B, the frequency region between the selected segments is released as a free frequency. As another example, when the control unit 433 instructs to arrange the selected segments on the frequency axis without gaps, the matrix type frequency conversion unit 432 converts and outputs the frequency bands of the segments. To do. As a result, as shown in FIG. 14C, the frequency region other than the collected segments is released as a free frequency.

  When predetermined frequency conversion is performed by the matrix type frequency conversion unit 132, signals in units of channels are respectively input to the second filter bank unit 16.

  According to the relay device 4 of this embodiment, since the first filter bank unit that performs frequency band division and the signal selection unit that selects a predetermined segment in the channel are provided, any frequency conversion (in units of segments) Frequency relocation). Thereby, effective utilization of frequency resources can be achieved.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components 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 constituent elements 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.

  In the above embodiment, the relay device is described as a relay unit of the wireless system, but the present invention is not limited to this. In other words, it may be applied as a relay means for a wired system such as CATV. In the above embodiment, the frequency conversion is performed in the front end part and the final stage part, but the present invention is not limited to this. That is, processing may be performed without frequency conversion to a local signal.

  Furthermore, in the above-described embodiment, the relay apparatus is described as being realized by hardware, but may be realized by a computer program installed in a computer, a PIC, or the like.

  The present invention relates to a frequency division multiplexing relay system, and is capable of reducing the size, price, and cost of relay devices such as terrestrial digital TV broadcasting, analog TV broadcasting, and CATV broadcasting that employ frequency division multiplexing. It can be widely applied as a technology aiming at power consumption.

It is a block diagram which shows the structure of the relay apparatus of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the 1st filter bank part in the relay apparatus of 1st Embodiment. It is a block diagram which shows the structure of the 2nd filter bank part in the relay apparatus of 1st Embodiment. It is a conceptual diagram which shows the analog filter function of 1st Embodiment. It is a conceptual diagram which shows the analog filter function of 1st Embodiment. It is a conceptual diagram which shows the digital filter function of 1st Embodiment. It is a conceptual diagram which shows the digital filter function of 1st Embodiment. It is a block diagram which shows the structure of the signal calculating part of 1st Embodiment. It is a schematic diagram which shows the gain control function in the relay apparatus of 1st Embodiment. It is a schematic diagram which shows the frequency distribution function of 1st Embodiment. It is a block diagram which shows the structure of the signal calculating part in the relay apparatus of the 2nd Embodiment of this invention. It is a schematic diagram which shows the power spectrum explaining the function of the unnecessary wave identification part of 2nd Embodiment. It is a conceptual diagram which shows the unnecessary wave removal function of 2nd Embodiment. It is a block diagram which shows the structure of the signal calculating part in the relay apparatus of the 3rd Embodiment of this invention. It is a schematic diagram explaining the channel estimation function of 3rd Embodiment. It is a block diagram which shows the structure of the signal calculating part in the relay apparatus of the 4th Embodiment of this invention. It is a schematic diagram which shows the frequency redistribution function of 4th Embodiment. It is a schematic diagram which shows the frequency redistribution function of 4th Embodiment. It is a schematic diagram which shows the frequency redistribution function of 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Front end part, 12 ... LPF part, 13 ... ADC part, 14 ... 1st filter bank part, 15 ... Signal operation part, 16 ... 2nd filter bank part, 17 ... DAC part, 18 ... LPF part, DESCRIPTION OF SYMBOLS 19 ... Final stage, 21-23 ... Delay element, 31-34 ... Decimator, 41-44 ... Filter, 51 ... IFFT part, 52 ... FFT part, 61-64 ... Filter, 71-74 ... Interpolator, 81-83 ... delay elements, 91 to 93 ... adders.

Claims (11)

A filter that receives an analog reception signal in which a plurality of channels are frequency-multiplexed and limits the frequency band of the reception signal;
An A / D converter that converts an analog received signal having a limited frequency band into a digital received signal;
A band dividing unit that divides the digital received signal into a plurality of signals in units of channels;
A band synthesizing unit that synthesizes a plurality of divided channel unit signals into a frequency-multiplexed digital transmission signal;
A relay apparatus comprising: a D / A converter that converts the synthesized digital transmission signal into an analog transmission signal. A first filter that receives an analog reception signal in which a plurality of channels are frequency-multiplexed and limits the frequency band of the reception signal;
An A / D converter that converts an analog received signal having a limited frequency band into a digital received signal;
A band dividing unit that divides the digital received signal into a plurality of signals in units of channels;
A signal calculation unit that performs predetermined signal calculation processing in units of the channels on the plurality of signals divided in units of the channels;
A band synthesizing unit that synthesizes a plurality of signals in units of channels on which the signal calculation processing has been performed into a digital transmission signal that is frequency-multiplexed;
A relay apparatus comprising: a D / A converter that converts the synthesized digital transmission signal into an analog transmission signal. The band dividing unit includes:
A first delay unit that delays the digital reception signal to perform serial-parallel conversion;
A decimator for thinning each of the plurality of serial-parallel converted signals;
A second filter unit that limits each of the plurality of thinned-out signals to a predetermined frequency band;
A first filter bank including an IFFT unit that performs a fast inverse Fourier transform on the plurality of signals having the frequency bands limited;
The band synthesizing unit
An FFT unit that performs a fast Fourier transform on the plurality of signals that have undergone the signal arithmetic processing;
A third filter unit for limiting the plurality of fast Fourier transformed signals to a predetermined band;
An interpolator for interpolating each of the plurality of signals having a limited frequency band;
3. The relay apparatus according to claim 2, further comprising a second filter bank including a second delay unit that delays and combines the plurality of interpolated signals.   The relay apparatus according to claim 2, wherein the signal calculation unit includes a frequency conversion unit that changes a frequency arrangement of each of the plurality of divided signals. The signal calculation unit is
A signal detector for detecting a predetermined signal from each of the plurality of divided signals;
5. The relay device according to claim 2, further comprising a signal processing unit that performs predetermined signal processing on the detected predetermined signal. 6. The signal detection unit selects a signal whose power level does not satisfy a predetermined reference value from among the plurality of divided signals,
The relay apparatus according to claim 5, wherein the signal processing unit amplifies the selected signal so that a power level of the selected signal satisfies the reference value. The signal detection unit selects a signal of a predetermined broadcasting system from each of the plurality of divided signals,
The relay apparatus according to claim 5, wherein the signal processing unit performs a suppression process on the selected signal. The relay apparatus according to claim 4, wherein the signal calculation unit further changes a frequency arrangement of a predetermined frequency segment constituting each of the plurality of divided signals. The signal calculation unit is
A channel estimation unit that estimates a sneak component of the analog transmission signal included in the analog reception signal in units of the plurality of divided signals;
5. The wraparound canceller that suppresses the wraparound component from each of the plurality of divided signals based on an estimation result of the channel estimation unit. 6. Relay device. Receiving an analog reception signal in which a plurality of channels are frequency-multiplexed and limiting the frequency band of the reception signal;
Converting the analog reception signal having a limited frequency band into a digital reception signal;
Dividing the digital received signal into a plurality of signals per channel;
Executing a predetermined signal calculation process in units of channels on the plurality of signals divided in units of channels;
Synthesizing a plurality of signals for each channel on which the signal calculation processing has been performed into a frequency-multiplexed digital transmission signal;
Converting the synthesized digital transmission signal into an analog transmission signal. Computer
A first filter that receives an analog reception signal in which a plurality of channels are frequency-multiplexed and limits the frequency band of the reception signal;
An A / D converter that converts an analog received signal having a limited frequency band into a digital received signal;
A band dividing unit that divides the digital received signal into a plurality of signals in units of channels;
A signal calculation unit that performs predetermined signal calculation processing in units of the channels on the plurality of signals divided in units of the channels;
A band synthesizing unit that synthesizes a plurality of signals in units of channels on which the signal calculation processing has been performed into a digital transmission signal that is frequency-multiplexed;
A computer program that functions as a relay device including a D / A converter that converts the combined digital transmission signal into an analog transmission signal.

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