JP5696539B2 - Spurious measuring device and receiving device and communication system using the same - Google Patents

Description

  The present invention relates to a spurious measuring device, a receiving device using the spurious measuring device, and a communication system.

  In a communication system having a communication terminal such as a cellular phone or a portable information terminal and a base station, a harmonic component (hereinafter referred to as spurious) included in a clock signal, which is a periodic rectangular signal, interferes with the received signal, and the received signal Deteriorates. In addition, in the case of the orthogonal frequency division multiplexing (OFDM) system, the received signal interferes with the spurious signal, so that timing synchronization cannot be achieved and discrete Fourier transform (DFT) cannot be performed normally.

  Spurious, which is a harmonic component of the clock signal, is generated at a position where the clock frequency is multiplied, and changes in a sine wave (sin) cycle depending on the duty ratio of the clock signal. Therefore, it has been proposed to suppress spurious in the communication frequency band by appropriately setting the duty ratio. For example, Patent Documents 1 and 2 are cited.

  Further, improvement examples in the OFDM method are described in Patent Documents 3 and 4 and the like.

JP 2000-49576 A JP 2009-44271 A JP 2006-279254 A JP 2007-324704 A

  However, since the spurious changes with the sin period, even if the duty ratio of the clock signal is adjusted, it is impossible in principle to simultaneously reduce spurious adjacent frequencies. On the other hand, in the case of a communication system such as an OFDM system that multiplexes a plurality of subcarriers, there are a plurality of spurious signals in the wide communication frequency band. For this reason, it is not possible to reduce the spurious at the maximum power among the spurious within the communication frequency band by simply adjusting the duty ratio of the clock signal.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a spurious measuring device, a receiving device using the spurious measuring device, and a communication system for suppressing spurious noise in the communication frequency band.

The first aspect of the spurious measurement device is a spurious measurement device that measures spurious in a partial frequency region that divides a communication frequency band.
A pseudo-noise signal generator that generates a pseudo-noise signal in synchronization with a sample clock having a frequency twice the bandwidth of the partial frequency domain, and converts the frequency of the pseudo-noise signal to a frequency of the partial frequency domain A partial correlation synchronization pattern generator having a mixer and a DFT unit that generates a partial correlation synchronization pattern by performing a discrete Fourier transform (hereinafter DFT) on the frequency-converted pseudo noise signal;
An IDFT unit for generating a reference time domain signal by performing inverse discrete Fourier transform (hereinafter referred to as IDFT) on the partial correlation synchronization pattern;
On the transmission side, the correlation value is obtained by integrating the multiplication value of the reception time domain signal transmitted by IDFT of the transmission synchronization pattern obtained by DFT of the frequency-converted pseudo noise signal and the reference time domain signal. A correlation value generator to be generated;
A spurious determination unit that extracts spurious from the correlation value.

  According to the first aspect, each spurious intensity in the communication frequency region can be measured with high accuracy.

It is a figure which shows the spectrum of the harmonic component of a clock signal. It is a figure which shows the transmitter and receiver of the communication system in this Embodiment. It is a figure explaining the reception time domain signal S (t) and the reference time domain signal Rm (t) in the receiving apparatus of this Embodiment. It is a block diagram of the partial correlation measurement part 22 in the receiver in this Embodiment. 3 is a configuration diagram of a partial correlation synchronization pattern generator 220. FIG. It is a figure explaining operation | movement of the partial correlation synchronous pattern generator 220. FIG. It is a figure explaining operation | movement of the partial correlation synchronous pattern generator 220. FIG. It is a figure which shows the example of the power spectrum of a PN signal. It is a block diagram of the partial correlation synchronous pattern generator 16 in a transmitter. It is a block diagram of the correlation value detection part 224 in the partial correlation measurement part 22 of a receiver. It is a block diagram of each integrator 50-1 to 50-M of FIG. It is a figure which shows an example of correlation voltage _Cm ((tau)) of several 7. 3 is a detailed configuration diagram of a partial correlation measurement unit 22. FIG. FIG. 10 is a flowchart showing the operation of a spurious suppression control unit 228. It is a figure which shows the example of a relationship between the duty ratio D of a clock, and spurious intensity | strength. It is a block diagram of the partial correlation measurement part 22 in 3rd Embodiment.

  The spurious measuring apparatus, the receiving apparatus and the communication system using the spurious measuring apparatus in the present embodiment will be described by taking orthogonal frequency division multiplexing (OFDM) as an example of the communication method. However, as will be described later, the present embodiment is not limited to the OFDM system.

  FIG. 1 is a diagram illustrating a relationship between a harmonic component (spurious) of a clock signal and a communication frequency band. A receiving device of a communication system performs reception processing using a clock signal that is a periodic rectangular signal. For example, the receiving apparatus has a downmixer that downconverts a received high-frequency signal to a baseband, and this downmixer multiplies the received high-frequency signal by a local clock. The digital processing circuit in the receiving apparatus also performs digital processing in synchronization with the internal system clock.

  Among the receiving devices, especially mobile communication terminals are equipped with high-density electronic components due to advanced functions, shorter and lighter weight, and neglected deterioration of received signals due to interference with spurious generated from the terminal's own signal lines. Can not. For example, it takes time to synchronize the timing of the received signal due to interference with spurious signals, or erroneous detection of the received signal causes a decrease in throughput.

  An example of spurious generated by the terminal itself is a harmonic component of the clock signal. In the case of the clock frequency fc and the duty ratio D, the nth-order harmonic component (spurious) is expressed by the following equation (1). That is, the clock signal is decomposed into the following harmonic components by Fourier transform.

When the duty ratio D is D = 1/2, the nth harmonic component is expressed by the following equation (2).

  FIG. 1 is a diagram illustrating a spectrum of harmonic components of a clock signal. The horizontal axis indicates the frequency n and the order n of nfc, which is n times the clock frequency fc, and the vertical axis indicates the signal strength. FIG. 1 shows cases where the duty ratio D is 1/2, 1/3, and 1/4, respectively. As shown in the above formulas 1 and 2, the high frequency component (spurious) appears at a position multiplied by the clock frequency fc, and its intensity changes depending on the duty ratio D and the order n. For example, in the case of the duty ratio D = 1/2 in FIG. 1A, the spurious intensity is zero when n = 2k (k is a positive integer), and the peak intensity is obtained when n = 2k−1. The peak intensity attenuates in inverse proportion to nfc.

  When the duty ratio D = 1/3 in FIG. 1 (2), the spurious intensity becomes zero when n is a multiple of 3, and when the duty ratio D = 1/4 in FIG. Is a multiple of 4, the spurious intensity is zero.

  For example, when the communication frequency band is a narrow band of frequency 39fc shown in FIG. 1, if the duty ratio is set to D = 1/3, the 39th harmonic appearing in the narrow band becomes zero intensity. Therefore, when the communication frequency band is such a narrow band, the influence of spurious due to the clock signal can be suppressed by selecting a duty ratio at which the intensity of the harmonics appearing therein becomes zero. Thus, the spurious intensity can be made zero by selecting the duty ratio without changing the clock frequency of the communication terminal.

  However, as described above, in a communication method using a plurality of subcarriers such as the OFDM communication method, the communication frequency band is wide, and as shown in FIG. 1, a plurality of spurious signals appear in the band. . Therefore, it is not easy to extract and compare the plurality of spurious intensities. Further, in a communication system using phase amplitude modulation, since the amplitude is modulated during modulation, it is difficult to measure the spurious intensity because the modulation component is included in the intensity of the received signal.

  Furthermore, there is the following problem in the method of obtaining the spurious strength according to the above formulas 1 and 2 and setting the optimum duty ratio without actually measuring the spurious strength. That is, since both adjacent spurious cannot be made zero, the above method cannot be applied when a plurality of spurious exists in the communication frequency band. Furthermore, when the communication terminal is a mobile object, the interference position between the reception frequency and the spurious frequency shifts due to the influence of the Doppler shift, and the optimum duty ratio cannot be found by the calculation using the equations (1) and (2). That is, the above method can be applied only to fixed terminals.

[First Embodiment]
FIG. 2 is a diagram illustrating a transmission device and a reception device of the communication system according to the present embodiment. The transmission device TX includes an encoding processing unit 10 that encodes transmission data, an IDFT processing unit 12 that modulates the encoded data with subcarriers and performs IDFT processing, and an IDFT time domain signal S _BS (t) And RF transmission processing section 14 for up-converting the signal to a high frequency, amplifying it, and transmitting it from the antenna. Further, the transmission device TX includes a partial correlation synchronization pattern generator 16 that generates a partial correlation synchronization pattern instead of encoded data in the preamble period and outputs the partial correlation synchronization pattern to the IDFT processing unit 12. The partial correlation synchronization pattern generator 16 will be described later.

  On the other hand, the receiving device RX of FIG. 2 is based on an RF reception processing unit 20 that amplifies a received high-frequency signal and down-converts it to baseband, a baseband reception time domain signal S (t), and a partial correlation synchronization pattern (not shown). A partial correlation measurement unit 22 that measures a correlation value with the generated reference time domain signal and detects and sets an optimum duty ratio is provided. Further, the receiving device RX includes a synchronization unit 24 that performs frequency synchronization and timing synchronization based on the baseband reception time domain signal S (t), and a DFT process on the reception time domain signal S (t) to perform a plurality of subcarriers. 1 includes a DFT processing unit 26 that demodulates data and a decoding processing unit 28 that decodes the demodulated data.

FIG. 3 is a diagram for explaining the reception time domain signal S (t) and the reference time domain signal R _m (t) in the reception apparatus of the present embodiment. FIG. 3 shows frequency spectra of the reception time domain signal S (t) and the reference time domain signal R _m (t). The horizontal axis corresponds to the frequency f, and the frequency band WB of the OFDM baseband time domain signal is divided into _M partial frequency domains W _{1 to} W _M. The partial frequency regions W _{1 to} W _M are divided so that each region includes at most one spurious SP _{1 to} SP _M and further includes a plurality of subcarriers (not shown). That is, the bandwidth fw of each partial frequency region is as follows, assuming the subcarrier frequency interval fsc and the spurious frequency interval fsp.
fsc <fw <fsp
Then, the bandwidth of the m partial frequency range W _m is as follows.

That is, the bandwidths of the _{first to M} -1 partial frequency regions W _{1 to} W _M-1 are fw, respectively. For example, in the example of detecting and suppressing the spurious intensity by the clock signal, the bandwidth fw is made equal to the frequency fc of the clock signal. By setting the bandwidth fw in this way, a maximum of one harmonic of the clock signal shown in FIG. 1 exists in each partial frequency region. The bandwidth of the Mth partial frequency region WM is a width obtained by subtracting the total (M-1) fw of the bands of the first to M-1 partial frequency regions from the communication frequency band WB.

According to the present embodiment, in the transmission apparatus, during the preamble period, the partial correlation synchronization pattern generator 16 generates a different synchronization pattern (partial correlation synchronization pattern) for each partial frequency region, and the synchronization pattern is converted into a subcarrier. The IDFT processing unit 12 multiplexes the subcarrier signal by IDFT processing to form a time domain signal S _BS (t), which is transmitted after RF processing. The configuration of the partial correlation synchronization pattern generator 16 on the transmission device side will be described later.

On the other hand, the transmitted time domain signal is received by the receiving device RX and RF-processed by the RF reception processing unit 20 to be a baseband time domain signal S (t). As shown in FIG. 3, the time domain signal S (t) includes, for example, spurious SP _{1 to} SP _M that are harmonic components of the clock signal. As described above, each partial frequency region W _{1 to} W _M includes one or less spurious SP 1 to SPM.

In the receiving device RX, the partial correlation measurement unit 22 generates the reference time domain signal R _m (t) shown in FIG. 3 in order to detect the intensity of the spurious in the mth partial frequency domain W _m . To do. The reference time domain signal R _m (t) for the partial frequency domain W _m is a pseudo noise signal (PN signal: Pseudo Noise signal) having a power higher by the bandwidth fw of the partial frequency domain at a frequency m * fw. This is a time domain signal obtained by up-converting, generating a partial correlation synchronization pattern by DFT of the PN signal, and IDFT of the partial correlation synchronization pattern. Then, the partial correlation measuring unit 22 measures the correlation value between the reception time domain signal S (t) and the reference time domain signal R _m (t), and the intensity of the spurious SP _m in the mth partial frequency domain W _m . Is detected.

In the present embodiment, when a pseudo noise signal (PN signal) is generated at the sampling frequency 2fw, the PN signal has a bandwidth centered on the center frequency, as will be more apparent from the configuration of the partial correlation measurement unit 22 described later. Only the frequency of fw is high power. Using the frequency characteristics of this PN signal, the transmission device TX and the reception device RX allocate a synchronization pattern (frequency domain signal) generated from the same PN signal to the same partial frequency region W _m , and IDFT is used to generate a time domain signal, and by obtaining a correlation value between the reception time domain signal S (t) and the reference time domain signal R _m (t) corresponding to each time domain signal, the partial frequency domain W Measure the strength of spurious contained in _m .

By using this method, it is possible to extract the intensity of spurious waves that are included at most in each of the partial frequency regions W _{1 to} W _M. Then, while changing the duty ratio D of the clock signal, the maximum spurious intensity at each duty ratio is measured, and the duty ratio that minimizes the maximum spurious intensity is selected. As a result, the terminal device can be operated with the duty ratio of the clock signal with suppressed spurious.

  FIG. 4 is a configuration diagram of the partial correlation measuring unit 22 in the receiving apparatus according to the present embodiment. The partial correlation measuring unit 22 is based on the spurious measuring units 220, 222, 224, and 226 that measure the respective spurious in a plurality of partial frequency regions, and the spurious intensity measured by the spurious measuring unit, and the optimum duty ratio of the clock signal. And a spurious suppression control unit 228 for detecting and setting the above.

Spurious measurement unit, in accordance with the control signal m specifying the partial frequency range W _m, partial frequency domain from the PN signal generated by the sample frequency FW W _m partial correlation synchronization pattern {d _n} partial correlation synchronization for generating the _m A pattern generator 220, an IDFT unit 222 that generates a reference time domain signal R _m (t) by IDFT of a partial synchronization pattern {d _n } _m , a reception time domain signal S (t), and a reference time domain signal R _m A correlation value generation unit 224 that detects a correlation value (correlation voltage) with (t) and a spurious determination unit 226 that determines the strength of spurious from the correlation value (correlation voltage). The intensity of the spurious SP _m detected by the spurious determination unit 226 is given to the spurious suppression control unit 228.

  As described in detail later, the spurious suppression control unit 228 detects, for each of a plurality of duty ratios of the clock signal, the maximum spurious that is the maximum value of each spurious within the plurality of partial frequency regions measured by the spurious measurement unit, A duty ratio corresponding to the minimum maximum spurious is detected from the maximum spurious detected for each of a plurality of duty ratios, and the detected duty ratio is set in the clock generation circuit.

FIG. 5 is a configuration diagram of the partial correlation synchronization pattern generator 220. 6 and 7 are diagrams for explaining the operation of the partial correlation synchronization pattern generator 220. FIG. The partial correlation synchronization pattern generator 220 generates a synchronization pattern for acquiring partial correlation. The partial correlation synchronization pattern generator 220 is a sample clock 30− of the frequency 2fw (= 2fc) multiplied by 2 from the reference clock having the frequency of the bandwidth fw (= fc) of the partial frequency regions W _{1 to} W _M. 1 has a PLL synthesizer 30 that generates 1. The PLL synthesizer 30 further includes a clock 30-2 having a frequency mfw (= mfc) obtained by multiplying the reference clock by m times according to the control signal m, and a clock 30-3 having a frequency Mfw (= Mfc) multiplied by M times. Also generate.

The partial correlation synchronization pattern generator 220 includes a pseudo noise signal generator 32 that generates a pseudo noise signal 32-1 in synchronization with a sample clock 30-1 having a frequency of 2fw (= 2fc), and a pseudo noise signal 32. The mixer MIX1 that converts the frequency of −1 to the partial frequency region W _m including the spurious to be measured, and the converted pseudo noise signal 32-2 are serial-parallel converted by the clock 30-3 of the frequency Mfw (= Mfc), Further, the signal subjected to serial-parallel conversion is subjected to discrete Fourier transform (hereinafter DFT) with a clock obtained by dividing the clock 30-3 having the frequency Mfw (= Mfc) by the number of DFT points of the communication system used, and the partial correlation synchronization pattern { d _n } _m for generating D _n } _m . The pseudo noise signal generator 32 is constituted by, for example, a ΔΣ modulator.

  As shown in FIG. 7, the pseudo noise signal (PN signal) 32-1 generated by the pseudo noise signal generator 32 is set to +1 or −1 for each rising edge of the sample clock 30-1 having the frequency 2fw (= 2fc). It is a pulse signal that changes. Therefore, the PN signal 32-1 changes to +1, −1 with a period of 1 / 2fw. Therefore, as shown in FIG. 6, the spectrum of the PN signal 32-1 has high power in the frequency band fw (= fc) and low power in the other frequency bands.

Then, as shown in FIG. 6, the PN signal 32-1 generated by the pseudo noise signal generator 32 is up-converted to a frequency mfw (= mfc) corresponding to the partial frequency region W _{m from} which a correlation value is to be taken. Thus, it is converted into a PN signal 32-2 centered on the corresponding frequency.

The DFT unit 34 performs DFT processing on the PN signal 32-1 converted to a frequency corresponding to the partial frequency region W _m by using the high-speed clock Mfw (= Mfc), and generates a synchronization pattern {d _n } _m . That is, the PN signal 32-1 that is a time domain signal is converted into a synchronization pattern {d _n } _m that is a frequency domain signal. As shown in FIG. 7, the PN signal PN _m corresponding to the partial frequency region W _m is a pseudo-noise signal having a fixed period, and is up-converted and subjected to DFT processing for each frequency of a plurality of subchannels. It is converted into a synchronization pattern {d _n } _m having +1, 0, −1.

In the present embodiment, the transmission device and the reception device can separately generate correlation values in each partial frequency domain by using the same synchronization pattern {d _n } _m in each partial frequency domain Wm. . Therefore, as shown in FIG. 7, the partial correlation synchronization pattern generator 220 on the receiving device side generates a PN signal generated continuously by the pseudo noise (PN) signal generator 32 for a certain period (PN _{1 to} PN _m , PN _{m + 1 to} PN _M ), up-conversion and DFT processing are performed in turn, and synchronization patterns {d _n } ₁ to corresponding to multiple partial frequency regions W _{1 to} W _m and W _{m + 1 to} W _M {d _n } _m , {d _n } _{m + 1} to {d _n } _M are generated. Then, if necessary, a synchronization pattern {d _n } _m corresponding to the partial frequency region W _m of interest is output.

As shown in FIG. 4, the synchronization pattern {d _n } _m is modulated by the IDFT unit 222 and IDFT, and a reference time domain signal R _m (t that is obtained by multiplexing a plurality of subcarriers in the OFDM band. ) Is generated. If the modulation method of the preamble period in which the synchronization pattern is transmitted is Binary Phase Shift Keying (BPSK), the cos component of the synchronization pattern {d _n } _m is multiplexed, so the mth partial frequency domain The time domain signal R _m (t) for reference composed only of the frequency is given by the following equation (4).

Here, the number of subcarriers included in the m partial frequency domain and N _m, the frequency of the subcarrier of the m partial frequency domain ((m-1) N m + n) fsc (n = 1~N m ).

  FIG. 8 is a diagram illustrating an example of the power spectrum of the PN signal. This is a power spectrum when a PN signal generated by a PN signal generator at a sampling rate of 1 MHz is up-converted to a 3 GHz band. As shown in FIG. 7, since the symbol length of the PN signal is the clock period fc (= fw), the PN signal sample rate is 1 MHz (2fw (= 2fc)), which is half of 500 kHz (fw (= fc). )) The power spectrum has a steep bandwidth.

FIG. 9 is a configuration diagram of the partial correlation synchronization pattern generator 16 in the transmission apparatus. The partial correlation synchronization pattern generator 16 in the transmission apparatus has the same configuration as the partial correlation synchronization pattern generator 220 provided in the partial correlation measurement unit 22 in the reception apparatus in FIG. That is, the partial correlation synchronization pattern generator 16 in the transmission device uses the sample clock 30-1 having the frequency 2fw (= 2fc) and the frequency mfw (= mfc) from the clock having the frequency of the bandwidth fw (= fc) in the partial frequency domain. ) And a PLL synthesizer 30 that generates a clock 30-3 having a frequency Mfw (Mfc). Further, the partial correlation synchronization pattern generator 16 in the transmission apparatus includes a PN signal generator 32 that generates a PN signal based on the sample clock 30-1, and a mixer MIX2 that upconverts the PN signal to a frequency mfw (= mfc). The up-converted time-domain signal is serial-parallel converted with the clock 30-3 having the frequency Mfw (= Mfc), and the clock 30- having the frequency Mfw (= Mfc) is further converted into the serial-parallel converted signal. And a DFT unit 34 that generates a synchronization pattern {d _n } _m in the partial frequency domain Wm by performing DFT with a clock obtained by _dividing 3 by the number of DFT points of the communication system used. This synchronization pattern {d _n } _m is a frequency domain signal as shown in FIG.

Further, the partial correlation synchronization pattern generator 16 in the transmission device accumulates synchronization patterns {d _n } ₁ to {d _n } _M of all partial frequency regions in the communication band and outputs them to the IDFT unit 12. A generator 36 is included. The synchronization patterns {d _n } ₁ to {d _n } _M are converted into a time domain signal S _BS (t) that is IDFT-multiplexed by the IDFT unit 12 and sent to the communication medium after RF processing.

This transmitted time domain signal S _BS (t) is equivalent to the reference time domain signal R _m (t) of Formula 4 multiplexed with m = 1 to M. is there.

Also in this case, the modulation method in the preamble period in which the synchronization pattern is transmitted is BPSK.

As described above, on the transmission device side, all partial frequency domain synchronization patterns are converted into time domain signals S _BS (t) that are IDFT-multiplexed by the IDFT unit 12 and transmitted to the communication medium after RF processing. The Then, as shown in FIGS. 4 and 5, the receiving apparatus, and the received time domain signal S (t), the synchronization pattern {d _n} reference time domain signal IDFT the _m R _m (t of each partial frequency range ) And measure the signal strength in each partial frequency region. As shown in FIGS. 7 and 8, the PN signal has large power in the partial frequency domain band fw (= fc), and the other bands have small power. Therefore, by using the reference time domain signal R _m (t) generated from this PN signal, the signal intensity of each partial frequency domain W _m band can be extracted from the received time domain signal S (t). .

FIG. 10 is a configuration diagram of the correlation value detection unit 224 in the partial correlation measurement unit 22 of the reception apparatus. As shown in FIG. 4, the receiving apparatus converts the received signal into a baseband time domain signal S (t) by the RF reception processing unit 20. This reception time domain signal S (t) is a signal in which the transmission time domain signal S _BS (t) shown in Equation 5 has propagated through the transmission path. Further, the reception time domain signal S (t) includes a spurious component due to the clock signal of the receiving device. Therefore, if the channel matrix of the propagation path is ^ H (t) and the spurious is Ds (t), the received time domain signal S () received at time t is the signal S _BS (0) transmitted at time t = 0. t) is expressed by the following equation (6).

The correlation value generation unit 224 illustrated in FIG. 10 detects the correlation values in the first to M partial frequency regions in parallel. For this purpose, the memory 40 stores the reference time domain signal R _m (t) generated by the IDFT unit 222 in advance for m = 1 to M. The correlation value generation unit 224 includes M integrators 50-1 to 5-M that detect correlation values in the first to M partial frequency regions, respectively. Each integrator 50-1 to 50-M inputs a reception time domain signal S (t) and reference time domain signals R ₁ (t) to R _M (t) corresponding to each partial frequency domain, respectively. Correlation values (correlation voltages) C ₁ (t) to C _M (t) are generated.

FIG. 11 is a block diagram of each integrator 50-1 to 50-M in FIG. The integrator 50 includes a flip-flop FF that delays the reception time domain signal S (t) by each sample time dt, and reception time domain signals S (4dt−τ) to S (dt−τ) at the respective delayed sample points. , S (−τ) and reference time domain signals R _m (4dt) to R _m (0), and an adder 52 that accumulates the multiplication values. In the example of FIG. 11, the number of sample points is 4, but the number is not limited to this number, and any appropriate sample point is desirable.

Here, τ is a scanning phase. That is, each of the integrators 50-1 to 50-M scans the received signal region signal S (t) received at the sample point and corresponds to the received signal region S (t) to be scanned and each partial frequency region. A correlation value C _m with the reference time domain signal R _m (t) is generated. This correlation value is specifically a correlation voltage.

Since there are a plurality of subcarriers in the partial frequency domain and the number of spurious signals is 1 or less, the correlation voltage C _m (reception voltage between the reception time domain signal S (t) and the reference time domain signal R _m (t) ( τ) can be reduced to the following equations (7) and (8) having a steep peak.

Here, I _m is the maximum value of the partial correlation voltage in the m-th partial frequency region, tp is the timing position of the maximum value, A is the ideal partial correlation voltage of only the synchronization pattern considering the propagation path characteristics, and D _m is the reception A change in correlation voltage due to spurious generated from the apparatus, Ts, is a normalization constant. Further, the integration of Equation 7 is performed at t = dt to 4 dt.

The correlation value generation unit 224 illustrated in FIG. 10 generates correlation values (correlation voltages) C _m (τ) for all partial frequency regions. However, the correlation value generation unit 224 may have one integrator 50. In that case, the single integrator 50 sequentially generates the correlation values C _m (τ) (m = 1 to M) of the first to Mth partial frequency regions in a time division manner. Therefore, the partial correlation synchronization pattern generation unit 220 sequentially generates the synchronization pattern {d _n } _m of each partial frequency domain, and the reference time domain signal R _m (t) obtained by IDFT of the synchronization pattern {d _n } _m in the correlation value generation unit 224. The correlation voltage C _m (τ) is generated in order by supplying to the integrator.

FIG. 12 is a diagram illustrating an example of the correlation voltage C _m (τ) of Equation 7. The horizontal axis represents the scanning phase τ, and the vertical axis represents the correlation voltage C _m (τ). When the scanning phase is tp, the correlation voltage C _m (tp) becomes the maximum value I _m . Therefore, the function δ of Expression 7 takes the maximum value Im when the scanning phase τ is τ = tp.

FIG. 13 is a detailed configuration diagram of the partial correlation measurement unit 22. Compared with the partial correlation measurement unit 22 in FIG. 4, FIG. 13 particularly shows the configuration of the spurious suppression control unit 228. Hereinafter, the operation of the spurious determination unit 226 that extracts spurious from the correlation value C _m (t) (m = 1 to M) of each partial frequency region generated by the correlation value generating unit 224, and the duty that can suppress the spurious. The operation of the spurious suppression control unit 228 that detects the ratio will be described.

Spurious determination unit 226, the correlation value I _m of the partial frequency range, finding an ideal part 'variation D of the correlation value due to spurious removing the' estimated value A of a correlation voltage A _{m =} I m -A _' . For example, in the case of mobile phone communication, the estimated value A ′ is an average value of the received signal strength (RSSI) detected by automatic gain control (AGC) because the received signal is generally larger than noise. is there. This is because the spurious noise component is suppressed or substantially removed from the received signal strength by averaging. By removing the estimated value A 'from such correlation value I _m, the correlation value I _m due to the frequency offset between the Doppler shift and transceiver fluctuates, spurious which part frequency domain becomes the maximum value Can not be detected correctly.

In this way, the spurious determination unit 226 holds the absolute value of the value obtained by dividing the estimated value A ′ for the correlation voltage C _m acquired in each partial frequency region as the spurious intensity, and spurious in all partial frequency regions. The maximum value of the intensity is output to the spurious suppression control unit 228 as the maximum interference spurious J. This maximum interference spurious J is as shown in the following equation (9).

  Next, the operation of the spurious suppression control unit 228 that detects the duty ratio of the clock that suppresses spurious will be described. The spurious suppression control unit 228 has a duty ratio control unit 60 and a clock generator 62 that can variably set the duty ratio, and changes the duty ratio D in the range of 0 to 1 while changing the duty ratio D to the clock generator 62. A clock signal CLK having a frequency fc with a ratio D is generated. The clock signal CLK is used as a clock in the receiving apparatus and is supplied as a reference clock to the PLL synthesizer in the partial correlation synchronization pattern generator 220. Since the PLL synthesizer operates based on the rising edge of the reference clock, there is no problem even if the duty ratio D is changed.

  Then, the maximum interference spurious J of the spurious due to the clock signal CLK having the set duty ratio is stored, and the duty ratio D that minimizes the maximum interference spurious J is detected. By setting the duty ratio D in the clock generator 62, the maximum spurious within the communication frequency band can be further reduced.

  FIG. 14 is a flowchart showing the operation of the spurious suppression control unit 228. The duty ratio control unit 60 in the spurious suppression control unit 228 performs the control of FIG. 14 by software. First, a scanning program for scanning an optimum duty ratio at the time of power activation of the receiving device is read from a memory (not shown) (S10). When reception is started (S12), the duty ratio control unit 60 sets the duty ratio D to D = 0.5−nΔ for the clock generator 62. Since the initial value of n is n = 0, the initial duty ratio is D = 0.5 (S14). Thereby, the clock generator 62 generates a clock CLK having a duty ratio D = 0.5 and a frequency fc = fw (S16).

Then, this clock partial correlation synchronization pattern generator 220 on the basis of the CLK generates a sync pattern {d _{n} m,} the reference time-domain signal by the correlation value generation unit 224 and IDFT a synchronization pattern {d _{n} m} R _m A correlation value between (t) and the reception time domain signal S (t) is generated, and the spurious determination unit 226 determines the maximum spurious value J for each partial frequency domain (S18). Then, the duty ratio D is set to D = 0.5−Δ (n = 1), and the above steps S14, S16, and S18 are repeated. This repetition is repeated until the duty ratio D reaches the minimum value Dmin≈0 (S20).

  FIG. 15 is a diagram illustrating a relationship example between the duty ratio D of the clock and the spurious intensity. As shown in this, the duty ratio D = 0 to 0.5 and D = 0.5 to 1.0 are in a target relationship. Therefore, when searching for the duty ratio D that minimizes the spurious as described above, the duty ratio D should be searched in the range of D = 0 to 0.5 or D = 0.5 to 1.0. Good. The example of FIG. 14 is an example of searching for D = 0 to 0.5.

  Returning to FIG. 14, the optimum duty ratio D corresponding to the smallest J among the maximum interference spurious J at all duty ratios D is determined (S22), and the optimum duty ratio D is set in the clock generator 62 (S24). ). As a result, the subsequent clock CLK is set to the duty ratio with the smallest maximum interference spurious J.

  Subsequent maximum interference spurious J is monitored based on the maximum interference spurious J (Dop) based on the optimum duty ratio Dop, and the maximum interference spurious J (D) at a certain duty ratio D is the maximum at the optimum duty ratio Dop. If it is detected that there is a difference equal to or greater than the interference spurious J (Dop) and the threshold value Jth (YES in S28), steps S14 to S24 are executed again to search for a new optimum duty ratio Dop, and the detected duty ratio Set Dop again.

  The reason for constantly monitoring the maximum interference spurious J is that, for example, when the receiving apparatus is a mobile terminal, the maximum interference spurious J within the communication frequency band varies due to a change in the band of the received signal due to Doppler shift. Because there are cases.

[Second Embodiment: Improvement of Spurious Detection Accuracy]
The estimated value A ′ of Equation 9 can be obtained from the average value of RSSI detected from the AGC as described above when the spurious intensity as noise is smaller than the received signal. However, when the spurious intensity is large and the S / N ratio of the received signal is poor, the spurious detection accuracy does not increase even if the estimated value A ′ is obtained by the above method.

In the second embodiment, the spurious determination unit 226 obtains a correlation voltage D _m by spurious using preamble period twice. First, the synchronization pattern generator of the transmission device generates a certain synchronization pattern {d _n } _m for m = 1 to M in the first preamble period, transmits it by IDFT, and in the second preamble period, A synchronization pattern / {d _n } _m obtained by inverting the sign of the synchronization pattern {d _n } _m is generated for m = 1 to M, IDFT, and transmitted.

On the other hand, in the receiving apparatus, the correlation value generation unit obtains correlation values C ⁽¹⁾ m and C ⁽²⁾ m in the m-th partial frequency domain in the first and second preamble periods, respectively. As a result, the maximum value I ⁽²⁾ m of the ^second partial correlation voltage is as shown in the following equation ⁽¹⁰⁾ .

Therefore, by adding the maximum value I _m of the first and second partial correlation voltage by 1/2, it is possible to obtain the maximum value I _m of the partial correlation voltage spurious moiety removed A. According to this method, since it is not necessary to obtain the estimated value A ′ from the gain value of AGC, it is possible to increase the spurious detection accuracy even when the spurious is large and the S / N ratio of the received signal is bad.

[Third Embodiment: Improvement of Spurious Detection Accuracy]
As the spurious intensity increases, the influence of the relative phase between the interference spurious and the received signal becomes significant. That is, the spurious component Ds (t) of Equation 6 is expressed by the following Equation 11, where fs is the spurious frequency included in the mth partial frequency region and θs is the relative phase with the received signal.

From the equation (11), it can be understood that under the condition that the spurious intensity is large, the influence of the interference spurious and the relative phase θs of the received signal is significant. That is, the spurious component Ds (t) varies according to the relative phase.

  Therefore, in the third embodiment, the pattern partial correlation measuring unit 22 uses the correlation value on the in-phase phase I side and the quadrature phase Q using the fact that the modulation method in the preamble period for transmitting the synchronization pattern is BPSK. Side correlation values are generated, and the generated correlation values are squared and added to remove the component of the relative phase θs and extract only the spurious intensity Ns.

FIG. 16 is a configuration diagram of the partial correlation measuring unit 22 in the third embodiment. The partial correlation measurement unit 22 includes an in-phase phase I side 224I and a quadrature phase Q side 224Q as the correlation value generation unit 224. Correspondingly, the IDFT unit for IDFT of the synchronization pattern also has an in-phase phase I side 222I and a quadrature phase Q side 222Q.
Here, the reception time domain signal S (t) is input to both the in-phase phase I side 224I and the quadrature phase Q side 224Q.

On the other hand, the reference time domain signal R _mI (t) of the I-IDFT unit 222I is multiplexed as a cos component and input to the in-phase phase I side 224I. The mathematical formula is as shown in Equation 12 as in Equation 4.

At this time, the output value of the correlation value generation unit (I) 224I is expressed by the following equation (13) with respect to the scanning phase (time) τ.

The reference time domain signal R _mI (t) of the Q-IDFT unit 222Q is multiplexed as a sin component and input to the quadrature phase Q side 224Q. The mathematical formula is as follows.

Here, as in the case of Equation 7, since the number of spurs in the partial frequency domain is 1 or less, the number of subcarriers is plural, so that the correlation value generating unit ( I) Correlation values having a steep peak are alternately obtained by 224I and the correlation value generator (Q) 224Q. In particular, when attention is focused on the correlation value generation unit (I) 224I, the maximum value of the output C _I (τ) of the correlation value generation unit (I) 224I is expressed by the following equation (15).

At this time, at the same timing, the output value of the correlation value generation unit (Q) 224Q is as the following Expression 16.

  The spurious intensity calculation unit 60 in the spurious determination unit 226 includes both the partial correlation values CI and CQ at the maximum output timing of the correlation value generation unit (I) 224I and the estimated value A ′ acquired from the spurious determination unit 64. Thus, the component of the relative phase θs is removed as shown in the following equation (17).

The spurious intensity Ns ² obtained by Expression 17 is the correlation power in the m-th partial frequency region, and is stored in the memory 62 for each partial frequency region. Then, the spurious determination unit 64 determines the maximum spurious intensity Ns ² in the entire partial frequency region and outputs it to the spurious suppression control unit 228. The subsequent control operation for detecting and updating the optimum duty ratio is the same as that of the first embodiment described with reference to FIG.

[Fourth Embodiment]
In the third embodiment, A is removed using the estimated value A ′. However, this A can be eliminated by adding and multiplying the spurious intensity obtained in the two preamble periods described in the second embodiment to 1/2. That is, the spurious strengths C _I ⁽¹⁾ and C _I ⁽²⁾ obtained in the two preamble periods are as follows.

By adding this and halving it, CI = Ns × sin θs can be obtained.

  Therefore, in the fourth embodiment, the spurious intensity calculator 60 obtains CI = Ns × sin θs from the spurious intensity obtained in the two preamble periods.

  As described above, according to the present embodiment, it is possible to detect the spurious intensity such as the harmonics of the clock signal with high accuracy, and to detect the optimum duty ratio that can suppress the maximum spurious intensity using this. Can do.

  In the above embodiment, the spurious due to the harmonic signal of the clock signal is measured, and the optimum duty ratio is detected. Therefore, the bandwidth fw in the partial frequency domain is set to the frequency fc of the clock signal.

  However, the spurious measurement units 220, 222, 224, and 226 of the present embodiment can also be applied to spurious other than the harmonics of the clock signal, and the intensity of each spurious discretely present in the communication frequency domain is It can be extracted using a synchronization pattern generated from the PN signal. In this case, the partial frequency domain band fw is set so that at most one spurious component exists in each partial frequency domain Wm. Thus, the spurious measurement unit of the present embodiment can measure the intensity of any spurious component.

  Further, the present embodiment has been described by taking the OFDM method as an example. However, in orthogonal frequency division multiplexing (OFDM), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiplexing (SC-OFDM), and single carrier frequency division multiple access (SC-FDMA) systems, A frequency domain signal, which is a plurality of subcarriers, is subjected to inverse discrete Fourier transform (IDFT) to generate a time domain signal, up-converted and transmitted to a communication medium, and a receiving device down-converts the received signal to generate a time-domain signal. Are subjected to discrete Fourier transform (DFT) to generate a plurality of frequency domain signals, and each signal is demodulated. In SC-OFDM and SC-FDMA, in addition to the above, the transmission apparatus generates a plurality of frequency domain signals by performing discrete Fourier transform on the time domain signal, and the transmission apparatus performs inverse discrete Fourier transform on the plurality of frequency domain signals. One time domain signal is generated.

  Therefore, this embodiment can be applied to any communication system other than OFDM, such as OFDMA, SC-OFDM, and SC-OFDMA.

  The above embodiment is summarized as follows.

(Appendix 1)
In a spurious measurement device that measures spurious in a partial frequency domain that divides a communication frequency band,
A pseudo-noise signal generator that generates a pseudo-noise signal in synchronization with a sample clock having a frequency twice the bandwidth of the partial frequency domain, and converts the frequency of the pseudo-noise signal to a frequency of the partial frequency domain A partial correlation synchronization pattern generator having a mixer and a DFT unit that generates a partial correlation synchronization pattern by performing a discrete Fourier transform (hereinafter DFT) on the frequency-converted pseudo noise signal;
An IDFT unit for generating a reference time domain signal by performing inverse discrete Fourier transform (hereinafter referred to as IDFT) on the partial correlation synchronization pattern;
On the transmission side, the correlation value is obtained by integrating the multiplication value of the reception time domain signal transmitted by IDFT of the transmission synchronization pattern obtained by DFT of the frequency-converted pseudo noise signal and the reference time domain signal. A correlation value generator to be generated;
A spurious measurement device including a spurious determination unit that extracts spurious from the correlation value.

(Appendix 2)
In Appendix 1,
The spurious determination unit performs IDFT on the first correlation value generated by the correlation value generation unit in the first period and a code-inverted transmission synchronization pattern obtained by inverting the sign of the transmission synchronization pattern in the first period. A spurious measurement device that extracts the spurious by adding the second correlation value generated by the correlation value generation unit in the second period transmitted in the above.

(Appendix 3)
In Appendix 1,
The IDFT unit IDFT an in-phase component of the partial correlation synchronization pattern to generate an in-phase reference time domain signal, and an IDFT quadrature phase component of the partial correlation synchronization pattern to generate a quadrature reference time domain signal. A quadrature phase IDFT section to be generated,
The correlation value generation unit integrates a multiplication value of the reception time domain signal and the in-phase reference time domain signal to generate an in-phase correlation value; and the reception time domain signal and the quadrature phase reference A quadrature correlation value generator that integrates a multiplication value with a time domain signal to generate a quadrature correlation value;
The spurious determination unit is a spurious measurement device that obtains a correlation power by the spurious by squaring and adding the in-phase correlation value and the quadrature phase correlation value, respectively.

(Appendix 4)
In Appendix 1,
The correlation value generation unit multiplies the reception time domain signal by a plurality of reference time domain signals generated by the partial correlation synchronization pattern generator for each of the plurality of partial frequency domains, and integrates the multiplication value. A plurality of integrators for generating correlation values for the plurality of partial frequency regions,
The reception time domain signal is a signal transmitted by performing an IDFT on a plurality of transmission synchronization patterns obtained by DFT of a plurality of pseudo noise signals frequency-converted to each of the plurality of partial frequency domains by a transmission apparatus. A spurious measuring device.

(Appendix 5)
In a receiving device that converts a reception time domain signal into a plurality of frequency domain signals,
A clock generation circuit that generates a clock signal with a set duty ratio;
A spurious measurement unit that measures each spurious in a plurality of partial frequency regions into which a communication frequency band is divided;
For each of a plurality of duty ratios of the clock signal, a maximum spurious that is a maximum value of each spurious in the plurality of partial frequency regions measured by the spurious measurement unit is detected, and a maximum spurious detected for each of the plurality of duty ratios is detected. And a spurious suppression control unit that detects a duty ratio corresponding to the smallest maximum spurious and sets the detected duty ratio in the clock generation circuit.

(Appendix 6)
In Appendix 5,
The spurious measuring unit is
A pseudo-noise signal generator that generates a pseudo-noise signal in synchronization with a sample clock having a frequency twice the bandwidth of the partial frequency domain, and converts the frequency of the pseudo-noise signal to a frequency of the partial frequency domain A partial correlation synchronization pattern generator having a mixer and a DFT unit that generates a partial correlation synchronization pattern by performing a discrete Fourier transform (hereinafter DFT) on the frequency-converted pseudo noise signal;
An IDFT unit for generating a reference time domain signal by performing inverse discrete Fourier transform (hereinafter referred to as IDFT) on the partial correlation synchronization pattern;
Correlation that generates a correlation value by integrating a multiplication value of a reception time domain signal transmitted by IDFT of a transmission synchronization pattern obtained by DFT of the frequency-converted pseudo noise signal and the reference time domain signal A value generator,
And a spurious determination unit that extracts spurious from the correlation value.

(Appendix 7)
In Appendix 5,
The receiving apparatus in which the partial frequency region is set to a frequency region having a single harmonic component of the clock signal.

(Appendix 8)
A receiving device according to any one of appendices 5, 6 and 7;
A transmission device for transmitting the reception time domain signal;
The transmitter is
A transmission-side pseudo-noise signal generator that generates a pseudo-noise signal in synchronization with a sample clock having a frequency twice the bandwidth of the partial-frequency region; and a frequency of the transmission-side pseudo-noise signal in the partial frequency region. A transmission-side partial correlation synchronization pattern generator having a transmission-side mixer for conversion, and a transmission-side DFT unit for generating a transmission-side partial correlation synchronization pattern by performing discrete Fourier transform (hereinafter DFT) on the frequency-converted pseudo noise signal; ,
A transmission-side IDFT unit that generates a transmission time domain signal by IDFT of the transmission-side partial correlation synchronization pattern;
A communication system in which the transmission time domain signal transmitted from the transmission apparatus is received as the reception time domain signal by the reception apparatus.

fc: clock frequency fsc: subcarrier frequency FW: communication frequency band fw (= fc): partial frequency domain bandwidth _W 1 to _W-M of: a plurality of partial frequency domain SP: Spurious D: duty ratio D _m: Spurious _{d n} , {D _n } _m : synchronization pattern

Claims (4)

In a spurious measurement device that measures spurious in a partial frequency domain that divides a communication frequency band,
A pseudo-noise signal generator that generates a pseudo-noise signal in synchronization with a sample clock having a frequency twice the bandwidth of the partial frequency domain, and converts the frequency of the pseudo-noise signal to a frequency of the partial frequency domain A partial correlation synchronization pattern generator having a mixer and a DFT unit that generates a partial correlation synchronization pattern by performing a discrete Fourier transform (hereinafter DFT) on the frequency-converted pseudo noise signal;
An IDFT unit for generating a reference time domain signal by performing inverse discrete Fourier transform (hereinafter referred to as IDFT) on the partial correlation synchronization pattern;
On the transmission side, a pseudo noise signal is generated in synchronization with a sample clock having a frequency twice the bandwidth of the partial frequency domain, and the frequency of the pseudo noise signal is converted to a frequency of the partial frequency domain and simulated. A noise signal is generated, and a product of a reception time domain signal transmitted by IDFT of a transmission synchronization pattern obtained by DFT of the frequency-converted pseudo noise signal and the reference time domain signal is integrated. A correlation value generator for generating correlation values;
A spurious measurement device including a spurious determination unit that extracts spurious from the correlation value. In claim 1,
The spurious determination unit performs IDFT on the first correlation value generated by the correlation value generation unit in the first period and a code-inverted transmission synchronization pattern obtained by inverting the sign of the transmission synchronization pattern in the first period. A spurious measurement device that extracts the spurious by adding the second correlation value generated by the correlation value generation unit in the second period transmitted in the above. In claim 1,
The IDFT unit IDFT an in-phase component of the partial correlation synchronization pattern to generate an in-phase reference time domain signal, and an IDFT quadrature phase component of the partial correlation synchronization pattern to generate a quadrature reference time domain signal. A quadrature phase IDFT section to be generated,
The correlation value generation unit integrates a multiplication value of the reception time domain signal and the in-phase reference time domain signal to generate an in-phase correlation value; and the reception time domain signal and the quadrature phase reference A quadrature correlation value generator that integrates a multiplication value with a time domain signal to generate a quadrature correlation value;
The spurious determination unit is a spurious measurement device that obtains a correlation power by the spurious by squaring and adding the in-phase correlation value and the quadrature phase correlation value, respectively. In claim 1,
The correlation value generation unit multiplies the reception time domain signal by a plurality of reference time domain signals generated by the partial correlation synchronization pattern generator for each of the plurality of partial frequency domains, and integrates the multiplication value. A plurality of integrators for generating correlation values for the plurality of partial frequency regions,
The reception time domain signal is a signal transmitted by performing an IDFT on a plurality of transmission synchronization patterns obtained by DFT of a plurality of pseudo noise signals frequency-converted to each of the plurality of partial frequency domains by a transmission apparatus. A spurious measuring device.

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