JP3854264B2 - Fading simulator, fading simulation method, and RF signal generator - Google Patents

Description

  The present invention relates to a fading simulator, a fading simulation method, and an RF signal generator that artificially generate multipath fading generated between transmission lines on a transmission side and a reception side.

  In wireless communication and broadcasting, the radio wave reception level varies with the movement of a wireless station and the passage of time. When there are a plurality of transmission paths due to reflection or the like between the transmitting station and the receiving station, a phase difference corresponding to the difference between these distances occurs, and the level of reception is increased (multipath fading). In communication in the short wave band, interference between the wave reflected by the ionosphere and the surface wave is mainly caused by interference of a plurality of reflected waves caused by topography, buildings, and the like in the ultra high frequency band and higher.

  Therefore, when conducting research and development of radio frequency (RF) receivers such as televisions and radios, or when producing them, it is essential to measure the performance of the RF receiver. In this performance measurement, fading resistance is an important measurement item.

  When measuring the performance of an RF receiver, an RF signal generator and an attenuator are used in a simple measurement, but the characteristics of the RF receiver are measured when a radio wave subjected to the above multipath fading is received. To do this, an RF signal generator and a fading simulator are used.

  As such a fading simulator, the present applicant has proposed a technique as shown in Patent Document 1. A local oscillator that generates a local frequency signal, a first mixer that obtains an intermediate frequency (IF) signal by multiplying a transmitted RF signal by the local frequency signal, and an A / D converter that digitizes the IF signal A plurality of signal processing means for artificially providing a fading path to the digitized signal, and a second frequency signal obtained by adding the signal passing through each signal processing means to the local frequency signal. The mixer is provided.

Here, each signal processing means includes a delay memory that gives a delay amount in a time unit corresponding to the sampling cycle, and a FIR (Finite Impulse Response) that gives a delay amount with a short time resolution equal to or less than the time corresponding to the sampling cycle. ) Since a delay unit having a filter is provided, it is possible to set a fine delay amount, and to simulate a fading phenomenon more realistically.
JP 2001-160789 A

  However, the delay device having the FIR filter in Patent Document 1 can generate only a delay wave having a preset pattern due to its configuration. That is, the multipath fading actually generated varies depending on the propagation path, but it cannot be set in the simulator in advance. Further, even if multipath is measured by actual measurement, it is necessary to input a huge number of tap coefficients in order to reflect the measurement data in the simulator setting.

  The problem to be solved is to generate a delayed wave adapted to the multipath generated in the actual propagation path, and to make necessary settings for the simulator directly from the radio wave reception data.

The fading simulator of the present invention is a fading simulator that generates an output signal having pseudo multipath fading based on an input digital signal, and is based on the input digital signal by a finite impulse response function. Multipath generation means having a plurality of FIR filter units for outputting a plurality of analog signals having fading, and synthesis means for synthesizing the plurality of analog signals and outputting them as the output signals, and an OFDM wave is demodulated The radio wave propagation data of the I / Q baseband signal in the format described above is converted into band-type impulse response data, and the band-type impulse response data is input to the multipath generation means to directly generate multipath fading. Control means is provided.
The fading simulator of the present invention may further include analog / digital conversion means for converting an external analog signal into a digital signal, and the output thereof may be the input digital signal.
Further, the FIR filter unit outputs a result of convolution of the input digital signal delayed by the predetermined time and the band impulse response data with a fixed delay circuit that outputs the input digital signal with a predetermined time delay. Multi-stage FIR filter means and a D / A circuit for converting the result of the convolution into an analog signal can be provided.
The FIR filter unit may further include a calibration circuit that calibrates its delay / phase / amplitude characteristics.
Further, the multistage FIR filter means may have a plurality of taps for outputting the result of the convolution with a predetermined delay time.
The fixed delay circuit may be set so as to bypass the section when there is a large gap in the band impulse response data.
The fading simulation method of the present invention is a fading simulation method for generating an output signal having pseudo multipath fading based on an input digital signal, and is based on the input digital signal by a finite impulse response function. Outputting a plurality of analog signals having general multipath fading, synthesizing the plurality of analog signals and outputting them as the output signals, and an I / Q baseband signal in a form in which an OFDM wave is demodulated Radio wave propagation data is converted into band-type impulse response data, and the band-type impulse response data is input to the finite impulse response function so as to directly generate multipath fading, and has the pseudo multipath fading A process of performing control to output a plurality of analog signals. It is characterized by having.
The RF signal generator of the present invention includes any one of the fading simulators described above.

  In the fading simulator of the present invention, the actual measurement data is converted into band-type impulse response data by the control means, and the multipath generation means is controlled to generate an output signal having pseudo multipath fading. It is possible to simulate a more precise fading phenomenon suitable for the multipath generation situation of the propagation path.

  In the present invention, by utilizing the characteristics of the FIR filter, the tap coefficient of each FIR filter of the multi-stage FIR filter means is determined by using the band system impulse response data obtained from the radio wave propagation data. A signal having multipath fading in the delay propagation path can be output.

  FIG. 1 is a diagram for explaining the usage form of the fading simulator of the present invention, FIG. 2 is a diagram for explaining the configuration of the fading simulator of FIG. 1, and FIG. 3 is a diagram for explaining the internal configuration of the FIR filter unit of FIG. 4 is a diagram for explaining the internal configuration of the FIR filter unit of FIG. 3, FIG. 5 is a diagram for explaining the multistage FIR filter means of FIG. 4, and FIG. 6 is a multipath generating means of FIG. FIG. 7 is a diagram for explaining the rearrangement of frequency axis data before IFFT processing, and FIG. 8 is a diagram after IFFT processing. It is a figure for demonstrating rearrangement of this time-axis data.

  As shown in FIG. 1, the fading simulator 1 receives an IF (intermediate frequency) signal from the RF signal generator 2, generates a signal having pseudo multipath fading, and outputs the signal to the RF signal generator 2. have. By the way, a signal having pseudo multipath fading from the fading simulator 1 is up-converted into an RF signal by the RF signal generator 2 and transmitted to the RF receiver 3 through a cable or the like. The fading resistance of the RF receiver 3 due to a signal having fading can be measured.

Next, the configuration of the fading simulator 1 will be described with reference to FIG.
The fading simulator 1 includes a frequency converter unit 11, an analog / digital conversion unit 12, an FIR filter unit 13, a combiner 14, and a control unit 15.

  The frequency converter 11 serving as a frequency conversion means converts an IF1 signal (first IF signal) 51 whose center frequency is 286 MHz from the RF signal generator 2 into an IF2 signal (second IF signal) whose center frequency is 16 MHz. Downconverted to 53 and output to the analog / digital converter 12. Further, the frequency converter unit 11 converts the IF3 signal (third IF signal) 56 having the center frequency of 16 MHz from the synthesizer 14 into the IF4 signal (fourth IF signal) 52 having the center frequency of 286 MHz as the RF signal generator 2. Output to.

  When the analog / digital conversion unit 12 serving as the analog / digital signal conversion unit receives the IF2 signal 53 having a center frequency of 16 MHz down-converted from the frequency converter unit 11, the analog / digital conversion unit 12 converts the IF2 signal 53 into a digital signal 54. Output to the FIR filter unit 13.

  When receiving the digital signal 54 from the analog / digital conversion unit 12, the FIR filter unit 13 as a multipath generation unit outputs a plurality of analog signals 55 having pseudo multipath fading. Will be described later.

  A synthesizer 14 as a synthesizer synthesizes a plurality of analog signals having pseudo multipath fading from the FIR filter unit 13 and uses the synthesized IF3 signal (third IF signal) 56 having a center frequency of 16 MHz as a frequency. Output to the converter unit 11.

  The control unit 15 serving as a control unit controls the operation of the entire fading simulator 1. The most important function of the control unit 15 is input of radio wave propagation data 58 that is actually measured data, and the radio wave propagation data 58 is converted into a band system. Converted to impulse response data, tap coefficients based on the band-type impulse response data are applied to taps 102a1 to 102an of a multistage FIR filter circuit 102 (to be described later) inside the FIR filter unit 13. Also, it has a function of outputting a calibration signal and controlling the calibration circuit in the FIR unit based on the comparison of the outputs at that time so that the characteristics of delay, phase and amplitude between the FIR units are matched.

  The control unit 15 obtains data from the radio wave propagation data 58 as follows. First, an OFDM wave is demodulated to obtain an I / Q baseband signal. The amplitude value of the SP (scattered pilot) signal is extracted from each signal. Next, the radio wave propagation data 58 is processed in the fading simulator as follows. Since the SP signal is only transmitted intermittently on the frequency axis, an amplitude value obtained by interpolating the SP signal in the frequency direction is generated.

  Next, each I / Q amplitude data is treated as one complex number. That is, the I signal is assigned to the real part and the Q signal is assigned to the imaginary part. As shown in FIG. 7, when the complex number data of the data number a is divided by the central index, the right half is arranged from one of the frequency axes corresponding to the number of IFFT points to be processed later, and the left half is the maximum index (nmax ). Next, IFFT processing is performed on the data on the frequency axis to convert it into time axis data. The time axis data obtained by the IFFT processing is also complex numbers, and by performing the following rearrangement processing, the real part is equivalent to I signal equivalent low frequency impulse response data, the imaginary part is equivalent to Q signal equivalent low frequency impulse response data and Become.

As shown in FIG. 8, the rearrangement is performed by exchanging the left half and the right half when the time axis data is divided at the center. Next, the equivalent low-frequency impulse response data (I signal, Q signal) is converted into band-based impulse response data using the following equation.
hbpf (n) = hi (n) × cos {2π × (n−nmax / 2) × freq / fs} −hq (n) × sin {2π × (n−nmax / 2) × freq / fs}
here,
n: Impulse response data index nmax; Impulse response data maximum index hbpf (n); Band system impulse response data hi (n) for index n; Equivalent low frequency system impulse response data (I signal) for index n
hq (n); equivalent low-frequency impulse response data (Q component) for index n
freq; center frequency fs of signal passing through FIR filter unit 13; sampling frequency

  nmax is the maximum index of the impulse response data and is the same as the number of points to be processed by IFFT. n is a value from 1 to nmax. hi (n) and hq (n) are equivalent low-frequency impulse response data for each n, and hbpf (n) is band-based impulse response data for each n. The equivalent low-frequency impulse response data is handled as a complex number based on a frequency of 0 Hz, but the band-based impulse response data is real data based on the center frequency (freq). Therefore, freq needs to be the center frequency of the signal that actually passes through the FIR filter units 131-136. If the obtained number of band-type impulse response data is larger than the total number of coefficients of the multistage FIR filter circuit 102 that can be realized by this fading simulator, the data at both ends of the band-type impulse response data is truncated.

Next, the internal configuration of the FIR filter unit 13 will be described with reference to FIG.
The FIR filter unit 13 has six FIR filter units 131 to 136. Each of the FIR filter units 131 to 136 outputs an analog signal 55 having pseudo multipath fading with a center frequency of 16 MHz to the synthesizer 14 by a finite impulse response function and a D / A conversion function. Note that the number of FIR filter units 131 to 136 is not limited to six as shown in the figure, and may be seven or more, or may be two to five.

Next, the internal configuration of each of the FIR filter units 131 to 136 will be described with reference to FIG.
Each of the FIR filter units 131 to 136 includes a fixed delay circuit 101, a multistage FIR filter circuit 102 as a multistage FIR filter means, a calibration circuit 103, and a D / A circuit 104.

  The fixed delay circuit 101 delays the digital signal 54 by a predetermined time in the plurality of FIR filter units 131 to 136 and sends it to the next multistage FIR filter circuit 102. For example, when these six FIR filter units 131 to 136 are continuously used without a gap, the delay time to be set is, as will be described later, sample time (Ts) × number of taps (n) × FIR unit number (m ), An integer m (m = 0 to 5) times.

  As an example, the multi-stage FIR filter circuit 102 as the multi-stage FIR filter means has, for example, 720 FIR filter taps 102a1 to 102an (n = 720) as shown in FIG. The tap coefficient for each of the taps 102a1 to 102an is set by the control unit 15, and a convolution result corresponding to the value is output.

  Here, if the sample time (Ts) is 40 nsec, the 720 taps 102a1 to 102an can delay up to 28.8 μsec. Further, the six FIR filter units 131 to 136 can delay a maximum of 172.8 μsec. In addition, each tap 102a1-102an is controlled by the control part 15 as mentioned above. In this example, it is possible to simulate up to 720 × 6 = 4,320 delay propagation paths.

  Here, the case where six FIR filter units 131 to 136 are arranged side by side without any gap has been described. However, when there is a large gap in the band impulse response data, the quantitative delay circuit 101 is used for that section. Can be set to bypass. In this case, the delay time that can be simulated can be longer than the maximum delay time of 172.8 μsec, and a propagation path with a long delay time can be simulated.

  The calibration circuit 103 includes a delay calibration circuit, a phase calibration circuit, and an amplitude calibration circuit, and is generated between the input of each FIR filter unit 131 to 136 and the output of the synthesizer 14 based on the calibration signal 57 from the control unit 15. This is to absorb the delay / phase / amplitude differences and to match the delay / phase / amplitude characteristics of each path observed with the IF3 signal as the output of the combiner output 14. In other words, if there is a delay / phase / amplitude difference between the input of each of the FIR filter units 131 to 136 and the output of the synthesizer 14, optimal simulation becomes impossible.

  The calibration signal 57 is first taken into only the FIR filter unit 131 or 131 and 132, and the IF3 signal, which is an output at the time of one wave or a combined output at the time of two waves, is acquired as a reference signal or a measurement signal by the control unit 15. . By operating the delay / phase / amplitude setting in the calibration circuit 103 of the FIR filter unit 132 from the control unit 15 a plurality of times, and analyzing the change of the IF3 signal with respect to each parameter by the control unit 15, the FIR filter unit 131 and A control signal 59 is output from the control unit 15 to the FIR filter unit 132 so as to minimize the delay / phase / amplitude differences among the 132.

  Next, the calibration of the FIR filter units 131 to 136 is completed by repeating the above operation with the FIR filter unit 131 as a reference in the order of the FIR filter units 131 and 133, 131 and 134, 131 and 135, 131 and 136. Details will be described later.

  The D / A circuit 104 converts the digital signal from the calibration circuit 103 into an analog signal and outputs the analog signal to the synthesizer 14.

  Note that the delay time setting by the fixed delay circuit 101, the delay transmission path setting by tap coefficient injection at the taps 102a1 to 102an of each multistage FIR filter circuit 102, and the delay / phase / amplitude calibration by the calibration circuit 103 are all described above. Controlled by the controller 15.

Next, the operation of the fading simulator 1 will be described.
First, since it is necessary to match the characteristics of delay, phase, and amplitude from the input of each FIR filter unit 131 to 136 to the output of the synthesizer 14 at the start of operation, the calibration signal 57 from the control unit 15 is the FIR. It is output to the filter unit 13.

The calibration signal 57 from the control unit 15 is a sine wave, and the frequency is first set to 16 MHz. Calibration is performed in the order of amplitude, phase, and delay. First, only the FIR filter unit 131 is output as a reference level, and the IF3 signal 56 is diode-detected by the control unit 15. The detected DC voltage is digitized and held in the control unit 15. Next, the detection voltage of the output of only the FIR filter unit 132 is acquired and compared with the acquired voltage of the FIR filter unit 131. If the comparison results do not match, the amplitude calibration circuit in the calibration circuit 57 is operated so as to match. Similarly, the same operation is performed for the FIR filter units 133 to 136.

  In this manner, the amplitude calibration of the FIR filter units 132 to 136 is completed with the FIR filter unit 131 as a reference. Next, phase calibration will be described. A phase calibration circuit in the FIR filter unit 131 sets the phase to 0 degree and outputs it. Similarly, the FIR filter unit 132 sets the phase to +90 degrees and outputs it. Two synthesized waves are taken into the control unit 15 from the IF3 signal 56 and diode detection is performed. As in the amplitude calibration, the digitized DC voltage value is held in the control unit 15. Let this value be A. Next, the phase setting of the FIR filter unit 132 is set to −90 degrees, and the DC voltage value is set to B. If the phase of both signals is 90 degrees, the values of A and B match.

  If they do not match, the phase calibration circuit in the calibration circuit 103 of the FIR filter unit 132 is operated to find a phase set value where A and B match. Specifically, the phase setting of the FIR filter unit 132 is acquired at -89 degrees, A is acquired, and the value of B is acquired at +91 degrees, so that the phase difference for acquiring A and B is always 180 degrees. Over. When the values of A and B match, the offset phase amount from the initial state becomes the phase error α. Similarly, phase calibration is performed in the combination of the FIR filter unit 131 and the FIR filter units 133 to 136.

  Next, delay calibration will be described. The frequency of the calibration signal 57 is set to 13 MHz, and the phase calibration is similarly performed between the FIR filter unit 131 and the FIR filter unit 132, but the delay is set to 0 ns in the delay setting circuit in both the calibration circuits 103. The phase error α obtained at this time is α1A. Next, the frequency of the calibration signal 57 is set to 19 MHz, α is obtained in the same manner, and this is α1B. The difference between α1A and α1B is obtained and is defined as γ1.

  Next, in the same combination, the delay of the FIR filter unit 132 is set to 2 ns, and the value obtained in the same manner is γ2. Thereafter, the same processing is performed in steps of 1 ns until a delay of 20 ns to obtain γ1 to γ20. The delay setting value of γ having the smallest value is the delay offset. Similarly, the delay offset value is obtained in the combination of the FIR filter unit 131 and the FIR filter units 133 to 136, and the delay calibration is completed.

  After the calibration as described above, when the IF1 signal 51 having the center frequency of 286 MHz from the RF signal generator 2 is taken into the fading simulator 1, the IF1 signal 51 is converted into the IF2 signal having the center frequency of 16 MHz by the frequency converter unit 11. Downconverted to 53 and output to the analog / digital converter 12.

  The IF2 signal 53 output from the frequency converter unit 11 is converted into a digital signal 54 by the analog / digital conversion unit 12 and output to the FIR filter unit 13. In the FIR filter unit 13, the digital signal 54 output from the analog / digital conversion unit 12 is taken into the six FIR filter units 131 to 136.

  Then, the digital signal 54 taken into the FIR filter unit 131 is delayed by a fixed time different for each of the FIR filter units 131 to 136 by the fixed delay circuit 101 and then sent to the multistage FIR filter circuit 102. And the convolution result by the tap coefficient inject | poured into each tap 102a1-102an in the multistage FIR filter circuit 102 is output. Here, assuming that the sample time (Ts) is 40 nsec, for example, the result of convolution with tap coefficients injected into 720 taps 102a1 to 102an can include a delayed wave up to 28.8 μsec.

  The digital signal thus obtained is converted by the D / A circuit 104 into an analog signal 55 subjected to pseudo multipath fading with an IF having a center frequency of 16 MHz and output to the synthesizer 14.

Although the above description is for the FIR filter unit 131, the other FIR filter units 132 to 136 are similarly output to the synthesizer 14 as analog signals converted to IF having a center frequency of 16 MHz. .
Here, if the delay time of the fixed delay circuit 101 in each of the FIR filter units 131 to 136 is determined as follows, a delay signal of 172.8 μsec at maximum can be generated as a whole.
FIR filter unit number Delay time of fixed delay circuit 101
131 0μsec
132 28.8 μsec
133 57.6 μsec
134 86.4μsec
135 115.2 μsec
136 144.0 μsec
The impulse response in each of the FIR filter units 131 to 136 in this case is, for example, as shown in FIG.

  The example of FIG. 6 is a case where the FIR filter units 131 to 136 are continuously arranged, but a period in which the band system impulse response data calculated from the radio wave propagation data 58 input to the control unit 15 is blank. If there is, it is possible to set by skipping that period. Thus, the maximum delay time can be made longer than 172.8 μsec by skipping and setting the period.

  In the example of FIG. 6, each FIR filter unit is shown operating with a clock of 40 nsec. However, the setting of the band system impulse response data is about 1 nsec by forming the impulse response waveform with the FIR filter. It is possible to carry out with the resolution of.

  When the output signals of the FIR filter units 131 to 136 are taken into the synthesizer 14 as described above, the synthesizer 14 synthesizes the IF3 signal 56 with a pseudo multipath fading center frequency of 16 MHz. It is output to the frequency converter unit 11. When the IF3 signal 56 is taken into the frequency converter unit 11, it is up-converted and output as an IF4 signal 52 having a center frequency of 286 MHz.

  Then, the IF4 signal 52 having a center frequency of 286 MHz having pseudo multipath fading from the fading simulator 1 is up-converted into an RF signal in the RF signal generator 2 and transmitted to the RF receiver 3 through a cable or the like. Thus, it is possible to observe the performance degradation characteristics of the RF receiver 3 due to a signal having pseudo multipath fading.

  Thus, in this embodiment, the FIR filter unit 13 has six FIR filter units 131 to 136, and each FIR filter unit 131 to 136 has 720 taps 102a1 to 102an (n = 720). The delay time of the output digital signal 54 in each FIR filter unit 131-136 and the output of the convolution result by the tap coefficient input to each tap 102a1-102an can be set differently. It is possible to simulate a more precise fading phenomenon adapted to the actual multipath generation situation of the propagation path.

  Further, since the output delay times of the respective FIR filter units 131 to 136 can be set different from each other, fading simulation with a high degree of freedom is possible. In other words, when trying to generate a multipath fading signal that approximates the field transmission characteristics assuming a pseudo model environment, the more propagation paths, the closer to the actual field the multipath fading signal is generated. Can do.

  In the present embodiment, as shown in FIG. 2, the frequency converter unit 11 down-converts the IF1 signal 51 having the center frequency of 286 MHz into the IF2 signal 53 having the center frequency of 16 MHz, and then the analog / digital conversion unit 12. In the above description, the digital signal 54 has been described. However, instead of down-converting once, a method of down-converting a plurality of times in accordance with circuit characteristics may be employed.

Further, in this embodiment, the case where the center frequency of the IF signal is 286 MHz and 16 MHz has been described. However, both are not limited to these values, and other values of the center frequency may be used.

  Further, in the present embodiment, as shown in FIG. 2, the IF signal 51 having a center frequency of 286 MHz is down-converted from the RF signal generator 2 to the IF 2 signal 53 having a center frequency of 16 MHz by the frequency converter unit 11. The case where the IF3 signal 56 having a frequency of 16 MHz is up-converted by the frequency converter unit 11 to be sent to the RF signal generator 2 after being converted to the IF4 signal 52 having a center frequency of 286 MHz. However, the frequency converter unit 11 is deleted. The IF1 signal 51 from the RF signal generator 2 may be directly input to the analog / digital conversion unit 12 and the IF3 signal 56 from the synthesizer 14 may be directly sent to the RF signal generator 2.

  In the FIR filter units 131 to 136 described above, although not shown, a digital attenuator may be installed on the front stage side of the D / A converter 104 and an analog attenuator may be installed on the rear stage side. In this case, in the FIR filter units 131 to 136 that share an attenuation period with a small impulse response value on the vertical axis shown in FIG. 6, the impulse response data is multiplied by a fixed value, and the multiplied value is attenuated by the variable attenuator. It is also possible. By adding the variable attenuator as described above, it is possible to improve the SN ratio when the output signal level is low.

  Furthermore, the frequency of the IF2 signal 53 input to the analog / digital converter 12 shown in FIG. 2 and the frequency of the IF3 signal 56 output from the combiner 14 are not necessarily the same. Since the sample frequency of a generally available A / D converter is lower than the sample frequency of the D / A converter, any frequency can be used as long as it can be used under the best conditions of the A / D and D / A converters.

  In the present embodiment, the case where the six FIR filter units 131 to 136 can be continuously connected in the time axis has been described. However, as described above, each of the FIR filter units 131 to 136 is connected to each other. It is also possible to arbitrarily set the quantitative delay time. In other words, when multipath fading is considered on the delay time axis, signal components do not necessarily exist uniformly, and this portion is used when there is a delay interval with no component or a negligible delay interval. Therefore, multipath fading over a wider range of delay times can be realized.

  In addition, a multipath fading signal corresponding to a propagation path of one wave per unit is generated by considering the arbitrary number of taps n (about 20 to 30) in the FIR filter units 131 to 136 as a unit and performing window function processing. You may make it do. In this case, the relative delay time of each unit signal can be set to a value smaller than the period of the system clock. Here, when the RF frequency is increased, the wavelength is shortened, and the influence of a short delay time cannot be ignored.

  In the future, in radio communication in a narrow space, the use of higher-frequency radio waves is expected, which may become an important problem in multipath fading. However, by using the fading simulator 1 in this embodiment, radio communication in a narrow space is possible. It is possible to optimally perform a fading test of a wireless device at This is because the fading simulator 1 in the present embodiment can finely set the setting to data that matches the actual situation.

  If there is radio wave propagation data, by analyzing the data, parameters for approximating the delay propagation path are calculated, and multipath fading when a radio wave signal of an arbitrary system propagates through the radio wave propagation path is calculated. It can be applied when receiving received signals.

It is a figure for demonstrating the usage form of the fading simulator of this invention. It is a figure for demonstrating the structure of the fading simulator of FIG. It is a figure for demonstrating the internal structure of the FIR filter part of FIG. It is a figure for demonstrating the internal structure of the FIR filter unit of FIG. It is a figure for demonstrating the multistage FIR filter means of FIG. It is a figure for demonstrating sharing of the band system impulse response of a radio wave propagation by each FIR filter unit inside the multipath generation | occurrence | production means of FIG. It is a figure for demonstrating rearrangement of the frequency-axis data before IFFT processing. It is a figure for demonstrating rearrangement of the time-axis data after IFFT processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fading simulator 2 RF signal generator 3 RF receiver 11 Frequency converter part (frequency conversion means)
12 Analog / digital conversion part (analog / digital conversion means)
13 FIR filter section (multipath generation means)
14 Synthesizer (synthesizer)
15 Control unit (control means)
101 fixed delay circuit 102 multistage FIR filter circuit (multistage FIR filter means)
102a1 to 102an tap 103 calibration circuit 104 D / A circuit 131 to 136 FIR filter unit

Claims (8)

A fading simulator that generates an output signal having pseudo multipath fading based on an input digital signal,
Multipath generation means having a plurality of FIR filter units for outputting a plurality of analog signals having pseudo multipath fading by a finite impulse response function based on the input digital signal;
The synthesis means for synthesizing the plurality of analog signals and outputting as the output signal,
The radio wave propagation data of the I / Q baseband signal in a form in which the OFDM wave is demodulated is converted into band-type impulse response data, and the band-type impulse response data is input to the multipath generation means to perform multipath fading directly. Control means for performing settings to be generated ;
A fading simulator comprising:   2. The fading simulator according to claim 1, further comprising analog / digital conversion means for converting an analog signal from the outside into a digital signal, and using the output as the input digital signal. The FIR filter unit is
A fixed delay circuit for outputting the input digital signal with a predetermined time delay;
Multi-stage FIR filter means for outputting a result of convolution of the input digital signal delayed by the fixed time and the band impulse response data;
The fading simulator according to claim 1, further comprising: a D / A circuit that converts the result of the convolution into an analog signal.   The fading simulator according to claim 3, wherein the FIR filter unit further includes a calibration circuit that calibrates characteristics of its own delay, phase, and amplitude.   The fading simulator according to claim 3 or 4, wherein the multistage FIR filter means has a plurality of taps for outputting the result of the convolution with a predetermined delay time.   5. The fading simulator according to claim 3, wherein the fixed delay circuit is set to bypass a section when there is a large gap in the band impulse response data. 6. A fading simulation method for generating an output signal having pseudo multipath fading based on an input digital signal,
Outputting a plurality of analog signals having pseudo multipath fading by a finite impulse response function based on the input digital signal;
Combining the plurality of analog signals and outputting as the output signal;
The radio wave propagation data of the I / Q baseband signal in a form in which the OFDM wave is demodulated is converted into band system impulse response data, and the band system impulse response data is input to the finite impulse response function to perform multipath fading directly. And a step of performing control to output a plurality of analog signals having the pseudo multipath fading.   An RF signal generator comprising the fading simulator according to claim 1.

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