JP2007251240A - Measuring device, and repeating installation utilizing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To process a signal formed by a plurality of channels while considering the transmission situation of the signal. <P>SOLUTION: A channel input 48 sets at least two channels to be extracted. A characteristic calculator 50 and a characteristic composite 52 generate frequency characteristics, where at least two set channels are extracted. A digital I/O filter 42 extracts at least two channels from a received signal with the generated frequency characteristics. An electric field strength measurement 58 measures strength to each of at least two channels. The characteristic calculator 50 reflects measured signal strength to a channel where the measured signal strength is larger than a threshold, when the frequency characteristics are generated where at least two channels are extracted, are generated, and uses a predetermined value to a channel where the measured signal strength becomes the threshold or smaller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a measurement technique, and more particularly, to a measurement apparatus that processes a signal formed by a plurality of channels and a relay apparatus using the measurement apparatus.

  In a broadcasting system such as a television broadcasting system, a signal is transmitted as an electromagnetic wave from a broadcasting station. The receiver receives a signal transmitted from the broadcast station, and acquires image information, audio information, and the like from the received signal. For signals transmitted by a broadcasting station, provisions such as transmission power and desired signal-to-interference wave ratio are established so that information of a predetermined quality can be obtained at a receiver existing in an area where the broadcasting station is a broadcasting area. . However, even if a broadcasting station transmits a signal that satisfies the regulations, if there are electromagnetic wave obstacles or the like in the broadcasting area, the electric field strength of the signal received by the receiver becomes insufficient, and the predetermined quality in the broadcasting area. There is a region where information on this is not available. Therefore, in order to reduce such quality degradation areas, a relay apparatus that receives a signal transmitted from a broadcasting station, amplifies and transmits the signal is installed in the broadcasting area.

  For example, the relay device receives an analog modulated signal formed by a plurality of channels by a receiving antenna, and outputs the received signal to a duplexer. The duplexer separates the received signal into channels. That is, the duplexer outputs a signal obtained by attenuating a signal in a frequency band other than the desired channel. The duplexer outputs a plurality of signals to a plurality of in-channel band amplification units. Each of the in-channel amplifying units amplifies a channel unit signal, and then converts it to an intermediate frequency band signal. In addition, after performing band limitation for attenuating a signal other than a desired channel, amplification is performed at an intermediate frequency, and the signal is again converted to a broadcast frequency band and then amplified. The amplified signals are output to the multiplexer. The multiplexer combines a plurality of signals. The signal synthesized by the multiplexer is transmitted as an electromagnetic wave via the transmission antenna.

Such a relay device separates a received signal into a plurality of channels, and individually performs band limitation and amplification on the frequency bands of the respective channels. This reduces as much as possible the interference wave caused by the intermodulation generated by the analog modulation signals of different channel frequency bands mutually affecting each other or the noise superimposed on the frequency band close to each channel frequency band. (For example, refer to Patent Document 1).
JP 2000-324036 A

  In recent years, digital television broadcasting that transmits information using a digitally modulated signal has been used, and an analog modulation signal and a digital modulation signal are mixed. Even in such a situation, the above-described relay device is used. In general, the electric field strength of a signal received by the relay device differs for each channel. Therefore, if the amplification factor in the relay device is common to all channels, the electric field strength of the signal transmitted by the relay device also differs for each channel. As a result, even if a relay device is installed, it is difficult to obtain the effect of reducing the quality degradation area for all channels. Further, when transmission of an arbitrary channel is stopped, it is preferable not to amplify the signal on the channel.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a measurement technique for processing a signal formed by a plurality of channels in consideration of a signal transmission state.

  In order to solve the above problems, a measuring apparatus according to an aspect of the present invention includes a receiving unit that receives a signal including a plurality of frequency-multiplexed channels, and a signal strength of signals to be received by the receiving unit. A setting unit configured to set at least one channel to be measured; and a measuring unit configured to measure a signal intensity for at least one channel set in the setting unit. The measurement unit performs discrete Fourier transform on the signal received by the reception unit, and then measures the signal intensity based on the result of the discrete Fourier transform, and at least one channel set by the setting unit Skip the execution of discrete Fourier transform for frequencies other than.

  According to this aspect, the discrete Fourier transform is executed for the channel whose signal intensity is to be measured, and the execution of the discrete Fourier transform is skipped for the other channels, so that the processing amount can be reduced.

  Another aspect of the present invention is a relay device. The apparatus includes: a receiving unit that receives a signal including a plurality of frequency-multiplexed channels; a setting unit that sets at least two channels to be extracted from signals to be received by the receiving unit; and a setting unit A generating unit that generates a frequency characteristic for extracting at least two set channels, a filter unit that extracts at least two channels from a signal received by the receiving unit by the frequency characteristic generated by the generating unit, and a filter unit And a transmission unit that transmits at least two channels extracted in (2) as frequency-multiplexed signals. The generation unit is configured to measure a signal intensity for each of at least two channels, and when generating a frequency characteristic that extracts at least two channels, the signal intensity measured by the measurement unit is a threshold value. An execution unit that reflects the measured signal strength for a larger channel and uses a predetermined value for a channel whose signal strength measured by the measurement unit is equal to or less than a threshold value.

  The “frequency characteristic” does not need to be indicated by a value in the frequency domain, and may be indicated by a value in the time domain having an equivalent characteristic. According to this aspect, even if it is a channel to be extracted, if the signal strength is equal to or lower than the threshold value, the signal strength is not reflected in the frequency characteristics, so when transmission on the channel is stopped, Can be avoided.

  The measurement unit measures the signal strength based on the result of the discrete Fourier transform after performing the discrete Fourier transform on the signal received by the reception unit, and at least two channels set by the setting unit. The execution of the discrete Fourier transform may be skipped for frequencies other than. In this case, the discrete Fourier transform is executed for the channel whose signal intensity is to be measured, and the execution of the discrete Fourier transform is skipped for the other channels, so that the processing amount can be reduced.

  When executing the discrete Fourier transform, the measurement unit may execute the process for the in-phase component and the process for the quadrature component in a time-sharing manner. In this case, the circuit scale can be reduced.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, a signal formed by a plurality of channels can be processed in consideration of a signal transmission state.

  Before describing the present invention in detail, an outline will be described. An embodiment of the present invention relates to a relay apparatus that receives a signal including a plurality of frequency-multiplexed channels, amplifies the received signal, and transmits the amplified signal. The plurality of channels include signals that are compatible with digital television broadcasting and that are digitally modulated. Since digital television broadcasting includes many channels, the processing in the relay device is performed in units of channels, and if the processing in units of channels is performed by another circuit, the circuit scale increases. End up. Further, if the amplification factors for a plurality of channels are set to a uniform value, a difference in transmission power occurs between channels in a signal transmitted from the relay device. As a result, since there are channels with low transmission power, it is difficult to provide uniform quality for a plurality of channels. In addition, a signal transmitted in a predetermined channel may not be transmitted. At this time, assuming that the signal of the channel is small, increasing the amplification factor for the channel will amplify noise and affect the signals of other channels. In the present embodiment, the following processing is executed in order to solve the above problems.

  The relay apparatus according to the present embodiment specifies in advance at least two channels to be relayed among a plurality of channels. In addition, a frequency characteristic that transmits at least two specified channels and attenuates the other channels is set for one filter. One filter extracts at least two channels from a plurality of received channels. In addition, the relay apparatus measures the reception intensity for each of the extracted at least two channels. At that time, the discrete Fourier transform (DFT) is performed on the channel to be relayed when the reception strength is measured, and the execution of DFT on the other channels is skipped. When the relay apparatus derives the above-described frequency characteristic, the relay apparatus reflects the measured reception intensity of each channel. At this time, if the measured reception strength of the channel is small, the reception strength is not reflected. Finally, the relay apparatus combines at least two extracted channels and then performs transmission.

  FIG. 1 shows a configuration of a relay device 100 according to an embodiment of the present invention. The relay device 100 includes a reception antenna 10, a reception filter 12, a reception amplification unit 14, a frequency converter 16, a frequency converter 22, a transmission amplification unit 24, a transmission filter 26, a transmission antenna 28, an A / D converter 40, a digital input An output filter 42, a D / A converter 44, a local oscillator 46, a channel input unit 48, a characteristic calculation unit 50, a characteristic synthesis unit 52, a normalized value calculation unit 56, and an electric field strength measurement unit 58 are included.

  The receiving antenna 10 receives a signal formed by a plurality of channels. The plurality of channels are frequency multiplexed. The plurality of channels includes a channel corresponding to digital television broadcasting and a channel corresponding to conventional analog television broadcasting. The reception antenna 10 outputs the received signal to the reception filter 12. The reception filter 12 attenuates the portion outside the band of the entire plurality of channels with respect to the signal received by the reception antenna 10. The reception amplification unit 14 amplifies the signal from the reception filter 12.

The frequency converter 16 converts the broadcast frequency band signal from the reception amplification unit 14 into an intermediate frequency band signal and outputs the signal to the A / D converter 40. The frequency converter 16, another broadcasting frequency band of the signal from the reception amplification unit 14, a local oscillator signal L ₁ from the local oscillator 46 is also input. Frequency converter 16 converts the signal of a broadcast frequency band to an intermediate frequency band signal by multiplying a local oscillator signal L ₁ to a signal of a broadcast frequency band.

Specifically, if the frequency of the local oscillator signal L ₁ is f _osc1 and the broadcast frequency band is a frequency band from the frequency f ₁ to the frequency f ₂ , the intermediate frequency band is from the frequency f ₁ −f _osc1 to the frequency f. The frequency band is up to ₂ −f _osc1 . Here, it is assumed that there is a relationship of f _osc1 <f ₁ <f ₂ . The processing by the frequency converter 16 generates an unnecessary image signal in the frequency band from the frequency f ₁ + f _osc1 to the frequency f ₂ + f _osc1, but this image signal is attenuated by the configuration _subsequent to the frequency converter 16. The The A / D converter 40 converts the intermediate frequency band signal into a digital signal and outputs the digital signal to the digital input / output filter 42.

  The channel input unit 48 sets at least two channels to be extracted from signals to be received. Here, at least two channels to be extracted correspond to channels to be relayed by the relay device 100. The channel input unit 48 has an interface for the user, and receives an instruction regarding a channel to be extracted from the user. For example, when a “channel number” is defined for each of a plurality of channels, the channel input unit 48 receives a channel number from the user.

  The characteristic calculation unit 50 generates a frequency characteristic that extracts at least two channels set in the channel input unit 48. The characteristic calculation unit 50 stores in advance frequency characteristics for extracting each of the plurality of channels. That is, frequency characteristics corresponding to a plurality of channel numbers are stored while associating channel numbers with frequency characteristics. Further, the characteristic calculator 50 selects a frequency characteristic corresponding to the channel number set in the channel input unit 48. Here, the characteristic calculation unit 50 stores in advance the frequency characteristics corresponding to each of the plurality of channels as time domain tap coefficients, and stores the plurality of types of time domain tap coefficients stored in accordance with the set at least two channels. Select the appropriate tap coefficient from

  The characteristic synthesizer 52 determines a frequency characteristic of a digital input / output filter 42 described later by synthesizing a plurality of frequency characteristics selected by the characteristic calculator 50. That is, the characteristic synthesis unit 52 determines the tap coefficient in the digital input / output filter 42 by synthesizing the tap coefficient selected by the characteristic calculation unit 50.

  Here, an outline of operations performed by the channel input unit 48, the characteristic calculation unit 50, and the characteristic synthesis unit 52 will be described. As described above, the channel input unit 48, the characteristic calculation unit 50, and the characteristic synthesis unit 52 determine the time domain tap coefficients of the channel input unit 48. Here, for the sake of simplicity, FIG. The frequency domain characteristics will be described using (a) to (f), and the description of the time domain characteristics will be described later. 2A to 2F show an outline of derivation of frequency characteristics by the characteristic calculation unit 50. FIG.

  The channel input unit 48, the characteristic calculation unit 50, and the characteristic synthesis unit 52 in FIG. 1 calculate the tap coefficient based on the input of the channel number of the broadcasting station whose broadcasting area is the area where the relay device 100 is installed. In FIG. 2A, the aforementioned “channel number” is indicated by the first channel 200 to the sixth channel 210. Here, as shown in FIG. 2A, the fifth channel 208 is assigned to the broadcasting station of the analog television broadcasting system, and the first channel 200 to the fourth channel 206 and the sixth channel 210 are the digital television. It is assumed that it is assigned to a broadcasting station of the John broadcasting system. Note that the third channel 204 is assigned to a broadcasting station of a digital television broadcasting system in which the area where the relay device 100 is installed is not a broadcasting area.

The channel input unit 48, the characteristic calculation unit 50, and the characteristic synthesis unit 52 calculate tap coefficients according to the following processes (1) to (10), and input them to the digital input / output filter 42 described later.
(1) Channel number of the broadcasting station of the digital television broadcasting system and channel number of the broadcasting station of the analog television broadcasting system are separately input to the channel input unit 48. However, it is assumed that the input channel number is assigned to a broadcasting station whose broadcasting area is the area where the relay device 100 is installed. In the example of FIG. 2A, the first channel 200, the second channel 202, the fourth channel 206, and the sixth channel 210 are input as channels of the digital television broadcasting system, and the fifth channel 208 is the analog television broadcasting system. Input as a channel. The channel input unit 48 outputs the input channel number to the characteristic calculation unit 50.

(2) The characteristic calculation unit 50 stores a channel frequency band corresponding to the channel number in advance, and calculates a broadcast frequency band based on the input channel number. From the calculated relationship between the predetermined intermediate frequency band as broadcast frequency bands to determine the frequency of the local oscillator signal L _1, local oscillator 46 sets the frequency of the local oscillator signal L ₁ to be output.
(3) The characteristic calculation unit 50 is input as the channel number of the digital television broadcast system or the channel number of the analog television broadcast system among the channel numbers of the channel frequency bands included in the calculated broadcast frequency band. It is recognized that the channel number that is not assigned is a channel number assigned to a broadcasting station that does not set the area where the relay apparatus 100 is installed as a broadcasting area. A function representing a band removal characteristic for attenuating a signal in the channel frequency band corresponding to the channel number is calculated and output to the characteristic combining unit 52. This function is assumed to be a function of frequency domain expression, and is hereinafter referred to as a band elimination characteristic function. In the example of FIG. 2A, it corresponds to the third channel 204, and the band elimination characteristic function is shown as in FIG.

(4) The characteristic calculator 50 calculates a band removal characteristic function for attenuating the signal in the channel frequency band corresponding to the channel number of the analog television broadcasting system, and outputs the band removal characteristic function to the characteristic synthesizer 52. In the example of FIG. 2A, since the analog television broadcasting system corresponds to the fifth channel 208, the band elimination characteristic function is shown as in FIG.
(5) The characteristic calculation unit 50 searches for the channel frequency band to be extracted that is the lowest among the channel numbers of the digital television broadcasting system.
(6) The characteristic calculator 50 calculates a function representing a high-pass characteristic having the low frequency end of the channel frequency band corresponding to the searched channel number as a cutoff frequency, and outputs the function to the characteristic synthesizer 52. This function is assumed to be a function of frequency domain expression, and hereinafter referred to as a high-pass characteristic function. In the example of FIG. 2 (a), the channel of the digital television broadcasting system having the lowest channel frequency band is the first channel 200, and the high-pass characteristic function is shown as in FIG. 2 (d). .

(7) The characteristic calculation unit 50 searches for the channel frequency band to be extracted that is the highest in the channel numbers of the digital television broadcasting system.
(8) The characteristic calculator 50 calculates a function representing a low-pass characteristic having the high frequency end of the channel frequency band corresponding to the searched channel number as a cutoff frequency, and outputs the function to the characteristic synthesizer 52. This function is assumed to be a function of frequency domain expression, and hereinafter referred to as a low-pass characteristic function. In the example of FIG. 2A, the channel of the digital television broadcasting system having the highest channel frequency band is the sixth channel 210, and the low-pass characteristic function is shown as in FIG.
(9) The characteristic synthesis unit 52 calculates a characteristic function obtained by multiplying the band elimination characteristic function, the high-pass characteristic function, and the low-pass characteristic function. In the example of FIG. 2A, the calculated characteristic function is shown as in FIG.
(10) The characteristic synthesizer 52 performs inverse Fourier transform on the characteristic function to calculate the characteristic function of time domain expression, calculates the tap coefficient by discretizing it, and outputs it to the digital input / output filter 42 described later To do.

  Returning to FIG. The digital input / output filter 42 extracts at least two channels from the signal from the A / D converter 40 based on the tap coefficient set by the characteristic synthesis unit 52. That is, the filter characteristics of the digital input / output filter 42 are determined by setting a tap coefficient in the digital input / output filter 42. In this embodiment, the tap coefficient is input from the characteristic synthesis unit 52. The digital input / output filter 42 is configured by a finite length impulse response (FIR) filter. The digital input / output filter 42 inputs an intermediate frequency band signal subjected to band limitation to the D / A converter 44.

  In addition, another operation | movement is added to the description mentioned above for the operation | movement of the characteristic calculation part 50 in a present Example. Before explaining the added operation, the problem with respect to the signal output from the digital input / output filter 42 according to the above explanation will be described with reference to FIGS. 3A to 3C show the problem of the frequency characteristic derived by the characteristic calculation unit 50. FIG. FIG. 3A shows a signal input to the digital input / output filter 42 as in FIG. The first channel 200, the third channel 204, the fourth channel 206, the sixth channel 210 to the eighth channel 214 are input as the channels of the above-mentioned digital television broadcasting system, and the second channel 202 and the fifth channel 208 are analog televisions. It is input as a channel of John broadcasting system. Note that the signal strengths of the first channel 200, the third channel 204, the fourth channel 206, and the sixth channel 210 to the eighth channel 214 are different due to the influence of fading or the like.

  FIG. 3B shows a frequency characteristic calculated by the characteristic calculation unit 50 and then synthesized by the characteristic synthesis unit 52. This corresponds to the frequency characteristic in the digital input / output filter 42. Note that FIG. 3B corresponds to FIG. FIG. 3C shows a signal output by the digital input / output filter 42. As shown in the figure, channels corresponding to the digital television broadcasting system are extracted. Further, the signal intensity for each extracted channel is different as in FIG. That is, the frequency characteristics set by FIG. 3B have a uniform amplification factor for the first channel 200, the third channel 204, the fourth channel 206, and the sixth channel 210 to the eighth channel 214. Therefore, the signal strength in FIG. 3A is reflected in the signal strength in FIG. As a result, since there are channels with low signal strength, it is difficult to provide uniform quality for a plurality of channels. In order to solve such a problem, the characteristic calculation unit 50 performs an additional operation.

  Returning to FIG. The electric field strength measuring unit 58 measures the signal strength for each of at least two channels from the digital input / output filter 42. Specifically, the electric field strength measuring unit 58 measures the signal strength within the channel band for each channel. That is, the electric field strength measurement unit 58 performs a discrete Fourier transform on the time domain signal input from the digital input / output filter 42, and then measures the signal strength based on the result of the discrete Fourier transform. . Here, the result of the discrete Fourier transform is shown as a frequency domain signal and numerical data corresponding to the frequency value. Further, the electric field strength measurement unit 58 derives the signal strength of the channel by integrating the numerical data in units of channels.

  The discrete Fourier transform is executed for the channel set in the channel input unit 48 and skipped for channels other than the channel set in the channel input unit 48. Details of such discrete Fourier transform will be described later. The electric field strength measurement unit 58 outputs the measured signal strength to the normalized value calculation unit 56 while associating it with the channel number. Further, the normalized value calculation unit 56 receives the signal strength corresponding to each channel to be extracted from the electric field strength measurement unit 58. When generating the frequency characteristics, the normalization value calculation unit 56 decreases the gain for a channel with a high signal strength and increases the gain for a channel with a low signal strength. For example, the normalized value calculation unit 56 derives a value corresponding to the reciprocal of the signal strength and sets it as the amplification factor in the channel corresponding to the signal strength.

  Here, the normalized value calculation unit 56 reflects the measured signal strength in the amplification factor for the channel whose signal strength measured by the electric field strength measurement unit 58 is larger than the threshold, and the electric field strength measurement unit 58 A predetermined value is used for a channel whose measured signal strength is equal to or less than a threshold value. The characteristic calculation unit 50 generates a frequency characteristic that extracts at least two channels as described above while reflecting the gain derived by the normalized value calculation unit 56. Details will be described later.

  A signal output from the digital input / output filter 42 by the operation as described above will be described with reference to FIGS. 4A to 4C correspond to FIGS. 3A to 3C, respectively. FIG. 4A is the same as FIG. FIG. 4B shows the frequency characteristic calculated by the characteristic calculation unit 50 and then synthesized by the characteristic synthesis unit 52, as in FIG. 3B. As described above, based on the signal strength measured by the electric field strength measuring unit 58, the characteristic calculating unit 50 derives the frequency characteristic while changing the amplification factor for each channel. Therefore, a small amplification factor is derived for a channel having a high received signal strength, such as the first channel 200 and the seventh channel 212 in FIG. Also, a large amplification factor is derived for a channel with a low received signal strength, such as the third channel 204 and the sixth channel 210 in FIG. FIG. 4C shows a signal output by the digital input / output filter 42. As shown in the figure, the signal intensity for each extracted channel is an equivalent value.

  FIGS. 5A to 5C show different input signal spectra to the digital input / output filter, different frequency characteristics derived by the characteristic calculator of FIG. 1, and different output signal spectra of the digital input / output filter, respectively. Indicates. FIG. 5A shows a signal input to the digital input / output filter 42 as in FIG. The second channel 202 and the fourth channel 206 are arranged with analog television broadcast system signals. Further, the first channel 200 to the eighth channel 214 are affected by multipath. FIG. 5B shows the frequency characteristic calculated by the characteristic calculation unit 50 and then synthesized by the characteristic synthesis unit 52, as in FIG. 4B. As described above, since the amplification factor is determined according to the signal strength of the channel, the amplitude in one channel, for example, the first channel 200 in FIG. 5B, has a substantially constant value. That is, the amplification factor does not reflect the effect of multipath. As a result, the processing amount is reduced. FIG. 5C shows a signal output by the digital input / output filter 42. As shown in the figure, the influence of multipath remains, but the signal strength for each extracted channel is an equivalent value.

Returning to FIG. The D / A converter 44 converts the input signal into an analog signal and inputs the analog signal to the frequency converter 22. The frequency converter 22 converts the intermediate frequency band signal into a broadcast frequency band signal and inputs the signal to the transmission amplifier 24. Frequency converter 22 converts the signal of the intermediate frequency band into a signal of a broadcast frequency band is multiplied by a local oscillator signal L ₁ to a signal of an intermediate frequency band. If the broadcast frequency band of the signal converted by the frequency converter 22 is equal to the broadcast frequency band of the signal input at the receiving antenna 10, a sneak wave is generated between the two. Therefore, the relay apparatus 100 may be provided with a wraparound canceller (not shown). Here, since the wraparound canceller is realized by a known technique, description thereof is omitted.

  The transmission amplifier 24 amplifies the signal in the broadcast frequency band and inputs it to the transmission filter 26. The transmission filter 26 attenuates the image signal included outside the broadcast frequency band of the input signal, the harmonic component signal due to the nonlinearity of the transmission amplifier 24, and the like, and inputs the attenuated signal to the transmission antenna 28. The transmission antenna 28 transmits the input signal as an electromagnetic wave. That is, at least two channels extracted by the digital input / output filter 42 are transmitted as a frequency multiplexed signal.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 6 shows the configuration of the characteristic calculation unit 50. The characteristic calculator 50 includes a first memory 60a, a second memory 60b, a third memory 60c, a fourth memory 60d, a fifth memory 60e, a sixth memory 60f, a seventh memory 60g, and an eighth memory, which are collectively referred to as the memory 60. 60h, first switch 62a, second switch 62b, third switch 62c, fourth switch 62d, fifth switch 62e, sixth switch 62f, seventh switch 62g, eighth switch 62h, amplifying unit First amplifying section 64a, second amplifying section 64b, third amplifying section 64c, fourth amplifying section 64d, fifth amplifying section 64e, sixth amplifying section 64f, seventh amplifying section 64g, and eighth amplifying section. Part 64h is included.

  The memory 60 stores a time domain waveform corresponding to a frequency characteristic for extracting each channel. Here, the first memory 60a stores a time-domain waveform corresponding to the frequency characteristics for extracting the first channel 200 of FIG. The same applies to the memories 60 other than the first memory 60a, and one memory 60 stores a time-domain waveform corresponding to the frequency domain for extracting one channel. 7A to 7H show the waveforms stored in the memory 60. FIG. On the left side of FIGS. 7A to 7H, frequency characteristics for extracting each channel are shown. Here, FIG. 7A corresponds to the first channel 200, and FIGS. 7B to 7H also correspond to the second channel 202 to the eighth channel 214, respectively. On the right side of FIGS. 7A to 7H, a time-domain waveform corresponding to the left frequency characteristic is shown. These are stored in the memory 60, respectively.

  Returning to FIG. When information about a channel to be extracted is input from the channel input unit 48, the switch 62 turns on the corresponding channel. In the example of FIG. 4A, since the first channel 200, the third channel 204, the fourth channel 206, the sixth channel 210, the seventh channel 212, and the eighth channel 214 are selected, the first switch 62a, The third switch 62c, the fourth switch 62d, the sixth switch 62f, the seventh switch 62g, and the eighth switch 62h are turned on. The remaining switches 62 are turned off.

  The amplification unit 64 receives the amplification factor from the normalized value calculation unit 56 and amplifies the waveform from the switch 62 by the received amplification factor. As described above, since the amplification factor from the normalized value calculation unit 56 generally has different values in units of channels, the amplification unit 64 outputs waveforms having different amplitudes in units of channels. The characteristic synthesis unit 52 receives the waveform amplified by the amplification unit 64 and synthesizes the received waveform to generate a tap coefficient. Note that the synthesis in the characteristic synthesis unit 52 is executed in units of each value of the normalization time. The characteristic synthesis unit 52 outputs the generated tap coefficient to the digital input / output filter 42. The digital input / output filter 42 sets the accepted tap coefficient.

  FIG. 8 shows an outline of signals processed in the electric field strength measuring unit 58. The horizontal axis indicates the frequency. As described above, the first channel 200 to the eighth channel 214 correspond to a plurality of channels. Here, signals of the digital television broadcasting system are arranged from the first channel 200 to the eighth channel 214. Further, a signal of an analog television broadcasting system is arranged in a channel having a frequency higher than that of the eighth channel 214. As shown, signal strength is measured at multiple points per channel. Furthermore, the final power measurement value is output by averaging the measured signal strength at a plurality of points included in one channel.

  For example, if the sampling frequency is 160 MHz and the number of DFT points is 160, the signal intensity is measured at 5 points per channel. Thus, by measuring one channel at a plurality of points, even when the spectrum is inclined due to multipath or the like, the power for each channel is accurately measured. Further, by measuring the power of one channel at a plurality of points, the digital television broadcast system signal and the analog television broadcast system signal can be accurately identified. Note that power measurement may be performed at one point per channel by using 16 points in the positive normalized frequency region for power measurement.

  FIG. 9 shows the configuration of the electric field strength measuring unit 58. The electric field strength measurement unit 58 is collectively referred to as a power measurement frequency setting unit 110, a counter 112, a cos table 114, a sin table 116, a first multiplier 118a, a second multiplier 118b, and an adder 120. First adder 120a, second adder 120b, first delay unit 122a, second delay unit 122b, collectively referred to as delay unit 122, first switch 124a, second switch 124b, collectively referred to as switch 124, and squaring A first squaring unit 126a, a second squaring unit 126b, and an adder 128, an adder 130, a delay unit 132, and a switch 134.

正規化周波数ｋに対応するスペクトルはＸ（ｋ）であり、その電力は｜Ｘ（ｋ）｜^２となる。ここで，ひとつのチャネルの信号帯域幅に対応する正規化周波数の数をｕと示し、最も低い正規化周波数をｓ（ｓ＝ｓ_０，ｓ_１，・・・、ｓ_Ｄ）と示すと、１チャネルの電力の和は以下のように示される。

したがって、電界強度測定部５８により正規化周波数ｓからｓ＋ｕ−１に対応する電力の和が算出される。 Before describing the configuration of the electric field strength measuring unit 58, the principle of discrete Fourier transform (DFT) will be described. The DFT for the discrete time signal sequence x (n) is defined by the following equation.

The spectrum corresponding to the normalized frequency k is X (k), and its power is | X (k) | ² . Here, when the number of normalized frequencies corresponding to the signal bandwidth of one channel is denoted by u and the lowest normalized frequency is denoted by s (s = s ₀ , s ₁ ,..., S _D ), The sum of the power of one channel is shown as follows.

Accordingly, the electric field intensity measurement unit 58 calculates the sum of power corresponding to s + u−1 from the normalized frequency s.

  The power measurement frequency setting unit 110 sets a normalized frequency corresponding to a signal band to be relayed from 0 to z−1 as a normalized frequency k with respect to the cos table 114 and the sin table 116 from a low normalized frequency. Give in order. Note that the normalized frequency may be given from the higher one. However, the power measurement frequency setting unit 110 sets the cos table 114 and the sin table 116 while repeating the normalized frequency k in a range corresponding to one channel R times.

  The cos table 114 stores a coefficient for the cos component in the DFT. FIG. 10 shows the data structure of the cos table 114. In the vertical column at the left end, “0” to “N−1” are entered, which corresponds to the normalized time n during which DFT is performed. Also, “0” to “z−1” are entered in the horizontal column at the top, which corresponds to the normalized frequency k described above. Also, the cos table 114 shows a value such as “A1” so as to correspond to a predetermined normalization time and normalization frequency. The sin table 116 is also configured in the same manner as in FIG.

  After the normalized frequency k is set by the power measurement frequency setting unit 110, the counter 112 performs normalization in the multiplier 118 by giving 0 to N−1 as the normalized time n to the cos table 114 and the sin table 116. A coefficient to be multiplied with the quantization time signal x (n) is selected. Here, the coefficients are shown in FIG. The counter 112 switches the switch 124 from the delay unit 122 side to the squaring unit 126 side when the count of the normalization time n is N-1. As a result, a spectrum X (k) corresponding to the normalized frequency k is output. Further, the counter 112 resets the normalization time n counter to 0 and gives an instruction to switch the normalization frequency k to the power measurement frequency setting unit 110, and then switches the switch 124 from the squaring unit 126 side to the delay unit 122 side. Return to. However, when the normalized frequency k in the power measurement frequency setting unit 110 exceeds the highest normalized frequency among the channels to be relayed, the power measurement frequency setting unit 110 again sets the normalized frequency k to the lowest normalized frequency. Return to frequency.

The first squaring unit 126a and the second squaring unit 126b square the real part Re [X (k)] and the imaginary part Im [X (k)] of the spectrum X (k), respectively, and the adder 128 produces the square result. Is added, the power corresponding to “s + u−1” is derived from the normalized frequency “s”. The power measurement frequency setting unit 110 is the normalized frequency “s + u−1” having the highest normalized frequency k among the normalized frequencies “s” to “s + u−1” in the range corresponding to one channel, and When the number of repetitions is R, the switch 134 is switched from the delay unit 132 side to the output side. As a result, the sum of the powers | X (k) | ² of the normalized frequencies “s” to “s + u−1” in the range of one channel is further accumulated R times by the adder 130, resulting in the following result: Is output. While the relay device 100 of FIG. 1 is in operation, the above operation is repeated unless the user sets to stop the measurement of the electric field strength and the change of the amplification factor.

ただし、かっこは、かっこ内の値の以上の最小整数を示す。例えば、Ｆｓ＝１６０ＭＨｚ、Ｂ＝６ＭＨｚ、チャネル数Ｍ＝８とすれば、以下の関係が成立する。

その結果、DFTのポイント数Ｎとして３２ポイント以上が必要となる。 Here, the number N of DFT points will be described. If the sampling frequency is Fs, the number of channels is M, and the bandwidth per channel is B, the following relationship is established.

However, parentheses indicate the smallest integer greater than or equal to the value in parentheses. For example, if Fs = 160 MHz, B = 6 MHz, and the number of channels M = 8, the following relationship is established.

As a result, a DFT point number N of 32 points or more is required.

In addition to DFT, Fast Fourier Transform (FFT) can be performed as a power measurement method for each channel. However, DFT is used here considering the amount of hardware. When calculating a normalized frequency signal formed by N points, the number of multiplications of complex numbers is N ² in DFT, the number of additions is N (N−1), and the amount of memory is 1, whereas In the FFT, the number of complex multiplications is (N / 2) × (log ₂ N−1), the number of additions is N × log ₂ N, and the amount of memory is N. However, since each normalized frequency signal can be calculated individually in the DFT, when calculating a spectrum corresponding to one normalized frequency, the number of multipliers is 2, the number of adders is 2, and the number of memories. Is also 2.

The operation of the relay device 100 configured as above will be described. FIG. 11 is a flowchart illustrating a procedure for calculating the amplification factor by the relay device 100. The electric field strength measurement unit 58 sets the channel number i to an initial value (S10). Here, the initial value corresponds to the smallest channel number among the channel numbers input to the channel input unit 48, that is, the channel numbers to be relayed. The amplification factor Ai corresponding to the channel number i is set to “1” for the channel number input to the channel input unit 48 and “0” for the channel number not input to the channel input unit 48. Is set. The electric field strength measuring unit 58 measures the electric power Pi (S12). When measuring power Pi, if FFT is used instead of DFT, power corresponding to a plurality of channels is derived instead of power corresponding to one channel. Will also execute the process. If Pi is greater than the threshold value (Y in S14), the normalized value calculation unit 56 sets | Ai | ² P / Pi to | Ai | ² (S16). P is the rated power sum.

On the other hand, if Pi is not larger than the threshold value (N in S14), the normalized value calculation unit 56 sets | Ai | ² to | Ai | ² (S18). If | Ai | ² is not equal to or less than Amax (N in S20), 1 is substituted for | Ai | ² (S22). On the other hand, if | Ai | ² is equal to or less than Amax (Y in S20), | Ai | ² is set as it is. Amax is a square value of the maximum amplification factor. The characteristic calculator 50 multiplies the filter coefficient by Ai (S24). The electric field strength measurement unit 58 adds 1 to i (S26). If i is not the set channel (N in S28), the electric field strength measuring unit 58 returns to Step 26. On the other hand, if i is the set channel (Y in S28) and i is not “maximum value + 1” (N in S30), the electric field strength measuring unit 58 returns to Step 12. If i is “maximum value + 1” (Y in S30) and the process is not completed (N in S32), the electric field strength measuring unit 58 returns to Step 10. On the other hand, if the process is completed (Y in S32), the electric field strength measuring unit 58 ends the process.

  Next, a modified example of the electric field strength measuring unit 58 will be described. FIG. 12 shows another configuration of the electric field strength measuring unit 58. The electric field strength measuring unit 58 includes a cos, sin alternating table 140 instead of the cos table 114 and the sin table 116 of the electric field strength measuring unit 58 of FIG. In the electric field strength measuring unit 58 in FIG. 12, the number of multipliers 118 and squaring units 126 is reduced compared to the electric field strength measuring unit 58 in FIG.

  In the cos, sin alternating table 140, values in the cos table 114 and values in the sin table 116 in FIG. 9 are alternately stored. That is, for one normalized frequency k, following the value in the cos table 114 for the normalized time “0”, the value in the sin table 116, the value in the cos table 114 for the normalized time “1”, A value in the sin table 116 is stored. The multiplier 118 multiplies one value of the input signal x (n) in order by two values of the cos and sine alternating table 140 in order at a period T / 2 that is half the sampling period T, and the adder 120 is output. That is, when the discrete Fourier transform is executed, the process for the in-phase component and the process for the quadrature component are executed in a time division manner. The adder 120 adds the input value from the adder 120 and the input value from the delay unit 122 at a cycle T / 2. The delay unit 122 includes two delay units having a delay time T / 2.

  FIG. 13 is a timing chart showing an outline of the operation in the electric field strength measuring unit 58. In the top row, a signal input to the electric field strength measuring unit 58 is shown, and the horizontal axis indicates time. Here, x (0) to x (N−1) are shown as signals that are subjected to DFT at one normalized frequency k. In the middle row, values output from the cos and sin alternating table 140 are shown. Two values are associated with one signal in the uppermost stage from the cos and sin alternating table 140, but the front value is the cos component and the back value is the sin component. The bottom stage shows the output from the multiplier 118. Returning to FIG.

  With the above configuration, the real part and the imaginary part of the spectrum corresponding to one normalized frequency are alternately output. Therefore, the number of multipliers 118 and adders 120 necessary for calculating a spectrum corresponding to one normalized frequency may be one. Moreover, since the real part and the imaginary part of the spectrum corresponding to one normalized frequency are output alternately, the number of the squaring parts 126 may be one. In addition to the above, since the squaring unit 126 is required after calculation of a spectrum corresponding to one normalized frequency, instead of the squaring unit 126 after calculating a spectrum corresponding to one normalized frequency, The multiplier 118 may be used by time division processing. Further, since the real part and the imaginary part of the spectrum corresponding to one normalized frequency are alternately output, the three adders of the first adder 120a, the second adder 120b, and the adder 128 in FIG. 12, the adder 120 is constituted by one adder.

  FIG. 14 shows another configuration of the relay device 100. The relay apparatus 100 in FIG. 14 relates to a relay apparatus in which a tap coefficient with an amplification factor adjusted for each channel is used, similar to the relay apparatus 100 in FIG. However, in the relay device 100 of FIG. 1, the adjustment of the amplification factor is performed by feedback processing, whereas in the relay device 100 of FIG. 14, the adjustment of the amplification factor is performed by feedforward processing.

FIG. 14 shows a configuration of the relay device 100 according to the first modification of the present invention. The components included in the relay device 100 in FIG. 14 are the same as the components included in the relay device 100 in FIG. The electric field strength measurement unit 58 receives not the signal from the digital input / output filter 42 but the signal from the A / D converter 40. The electric field strength measurement unit 58 measures the signal strength for each of at least two channels included in the signal from the digital input / output filter 42. The signal intensity is measured in the same manner as in the example. The normalized value calculation unit 56 derives amplification factors corresponding to at least two channels as described above based on the signal strength from the electric field strength measurement unit 58. Further, the characteristic calculation unit 50 generates a frequency characteristic that extracts at least two channels as described above while reflecting the gain derived by the normalized value calculation unit 56. The operation of the relay apparatus 100 configured as described above is different in step 16 in the flowchart of FIG. That is, the normalized value calculation unit 56 sets P / Pi to | Ai | ² . In other respects, the same processing as that of the relay device 100 of FIG. 1 is executed, and thus the description thereof is omitted here.

  FIG. 15 shows still another configuration of the relay device 100. The relay apparatus 100 of FIG. 15 includes a reception oscillator 80 and a transmission oscillator 82 instead of the local oscillator 46 of FIG. The reception oscillator 80 is a local oscillator used at the time of reception, and the transmission oscillator 82 is a local oscillator used at the time of transmission. With such a configuration, the relay apparatus 100 can set the frequency to be used for reception and the frequency to be used for transmission to different frequencies. Since other processes are the same as those of the relay apparatus 100 of FIG. 1, the description thereof is omitted here.

  FIG. 16 shows still another configuration of the relay device 100. The relay apparatus 100 of FIG. 16 includes a reception oscillator 80 and a transmission oscillator 82 instead of the local oscillator 46 of FIG. That is, the configuration in FIG. 16 is a configuration in which the relay device 100 in FIG. 14 and the relay device 100 in FIG. 15 are combined. Therefore, description is abbreviate | omitted here.

  According to the embodiment of the present invention, for one digital input / output filter, a frequency characteristic that extracts a desired channel and a frequency characteristic that reflects the signal strength of each channel is used. The difference in signal strength between channels can be reduced while suppressing an increase in circuit scale. Further, since the channel to be extracted can be set by the user, the channel to be extracted can be easily changed as necessary. In addition, since the signal strength measurement result is reflected in the tap coefficient, it is possible to execute control according to the actual reception status. Further, since control according to the actual reception situation is executed, it is possible to follow fluctuations in the propagation path. In addition, since the difference in signal strength between channels can be reduced, the quality degradation area can be reduced for all channels. In addition, since the time domain tap coefficient is stored in advance, the process of converting the frequency characteristic value into the time domain can be omitted, and an increase in the processing amount can be suppressed.

  In addition, by utilizing the fact that the influence of the intermodulation signal generated in the adjacent channel frequency band is due to the digital modulation signal is smaller than that due to the analog modulation signal, One input / output filter. In addition, the influence of the interference wave generated by the noise superimposed on the frequency band close to each channel frequency band, such as the interference wave generated in the adjacent channel frequency band at the time of frequency conversion, is also due to the analog modulation signal Compared to a digital modulation signal, the digital input / output filter can be integrated into one. This is a signal in which a large amount of power is concentrated in a narrow frequency band while an analog modulation signal is a signal in which power is distributed with a uniform density in a channel frequency band. It is because. That is, if the signals have the same power, the lower the power density in the frequency domain, the smaller the influence on the adjacent channel frequency band. Further, since the amplification factor is controlled by feedforward control, it is possible to follow even if the propagation path changes to some extent. Since the difference in signal strength between channels can be reduced, quality degradation areas can be reduced for all channels.

  Even if the channel to be extracted is not the threshold value, if the signal strength is below the threshold value, the signal strength is not reflected in the frequency characteristics. Amplification can be avoided. Moreover, since DFT is performed with respect to the channel which should measure signal strength, and execution of DFT is skipped with respect to the other channel, a processing amount can be reduced. Further, since the DFT is used instead of the FFT when measuring the signal strength, the processing amount can be reduced. Further, when executing DFT, the processing for the in-phase component and the processing for the quadrature component are executed in a time-sharing manner, so that the circuit scale can be reduced. Moreover, the number of multipliers and adders can be reduced by executing the time division processing. Even in the case of being affected by multipath, the amplification factor is determined without correcting the influence of multipath, so that the processing can be simplified.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the relay device 100 is described. However, the present invention is not limited to this. For example, the present invention may be applied to a measuring apparatus. The configuration of the measuring device corresponds to the relay device 100 according to the embodiment in which functions related to transmission are omitted. According to this modification, in a receiving apparatus including a plurality of tuners, the signal strength for a desired channel can be measured with a small amount of processing.

  In the embodiments of the present invention, a description is given on the assumption that a 13-segment system is used as a digital television broadcasting system to be relayed. However, the present invention is not limited to this. For example, the digital television broadcasting system to be relayed may be a one-segment system. In that case, the frequency is set in the digital input / output filter 42 and the electric field strength measuring unit 58 so as to be adapted to one segment. According to this modification, the present invention can be applied to various systems.

It is a figure which shows the structure of the relay apparatus based on the Example of this invention. 2A to 2F are diagrams showing an outline of derivation of frequency characteristics by the characteristic calculation unit of FIG. FIGS. 3A to 3C are diagrams showing a problem of frequency characteristics derived by the characteristic calculation unit of FIG. 4A to 4C are diagrams showing an input signal spectrum to the digital input / output filter, a frequency characteristic derived by the characteristic calculation unit in FIG. 1, and an output signal spectrum of the digital input / output filter, respectively. FIGS. 5A to 5C show different input signal spectra to the digital input / output filter, different frequency characteristics derived by the characteristic calculator of FIG. 1, and different output signal spectra of the digital input / output filter, respectively. FIG. It is a figure which shows the structure of the characteristic calculation part of FIG. FIGS. 7A to 7H are diagrams showing waveforms stored in the memory of FIG. It is a figure which shows the outline | summary of the signal processed in the electric field strength measurement part of FIG. It is a figure which shows the structure of the electric field strength measurement part of FIG. It is a figure which shows the data structure of the cos table of FIG. It is a flowchart which shows the calculation procedure of the amplification factor by the relay apparatus of FIG. It is a figure which shows another structure of the electric field strength measurement part of FIG. It is a timing chart which shows the operation | movement outline | summary in the electric field strength measurement part of FIG. It is a figure which shows another structure of the relay apparatus of FIG. It is a figure which shows another structure of the relay apparatus of FIG. It is a figure which shows another structure of the relay apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Reception antenna, 12 Reception filter, 14 Reception amplification part, 16 Frequency converter, 22 Frequency converter, 24 Transmission amplification part, 26 Transmission filter, 28 Transmission antenna, 40 A / D converter, 42 Digital input / output filter, 44 D / A converter, 46 local oscillator, 48 channel input unit, 50 characteristic calculation unit, 52 characteristic synthesis unit, 56 normalized value calculation unit, 58 electric field strength measurement unit, 100 relay device.

Claims (4)

A receiver for receiving a signal including a plurality of frequency-multiplexed channels;
Of the signals to be received by the receiving unit, a setting unit for setting at least one channel whose signal strength is to be measured;
A measurement unit that measures the signal strength for at least one channel set in the setting unit,
The measurement unit, after performing a discrete Fourier transform on the signal received by the receiving unit, measures the signal intensity based on the result of the discrete Fourier transform, and at least set in the setting unit A measurement apparatus characterized by skipping execution of discrete Fourier transform for frequencies other than one channel. A receiver for receiving a signal including a plurality of frequency-multiplexed channels;
A setting unit for setting at least two channels to be extracted from signals to be received by the receiving unit;
A generating unit that generates a frequency characteristic for extracting at least two channels set in the setting unit;
A filter unit that extracts at least two channels from the signal received by the receiving unit according to the frequency characteristics generated by the generating unit;
A transmission unit that transmits at least two channels extracted in the filter unit as a frequency-multiplexed signal;
The generator is
A measurement unit for measuring signal strength for each of at least two channels;
When generating a frequency characteristic that extracts at least two channels, the measured signal strength is reflected to a channel whose signal strength measured by the measurement unit is larger than a threshold value, and measured by the measurement unit. A relay apparatus comprising: an execution unit that uses a predetermined value for a channel whose signal strength is equal to or less than a threshold value.   The measurement unit, after performing a discrete Fourier transform on the signal received by the receiving unit, measures the signal intensity based on the result of the discrete Fourier transform, and at least set in the setting unit The relay apparatus according to claim 2, wherein execution of discrete Fourier transform is skipped for frequencies other than two channels.   The relay apparatus according to claim 3, wherein the measurement unit performs, in a time division manner, a process for an in-phase component and a process for a quadrature component when performing discrete Fourier transform.

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