JP5173490B2 - Sensitivity degradation estimation system and sensitivity degradation estimation method - Google Patents

Description

  The present invention relates to an electronic device having a wireless or wired reception function or communication function, and electromagnetic noise radiated from a part of the electronic device or a part of the electronic device, or electromagnetic waves observed in an installation environment of the electronic device. The present invention relates to an apparatus and method for estimating reception sensitivity deteriorated by noise. The present invention is particularly directed to an electronic device that handles a multicarrier signal typified by a high-frequency signal modulated using orthogonal frequency division division.

  For example, in the stage of development and design of electronic devices such as television receivers and wireless or wired LAN devices, reception of electronic devices deteriorated by electromagnetic noise radiated from the electronic device itself or electromagnetic noise observed in the installation environment of the electronic device. It is important to evaluate sensitivity. As a basic method for evaluating such sensitivity degradation, (1) a desired signal source desired to be received, (2) an electronic device, and (3) an electromagnetic noise source are prepared, and noise is superimposed on the desired signal to obtain an electronic signal. It is common to input to a device and check whether the electronic device can receive normally.

  Incidentally, electronic devices are often developed and manufactured by a plurality of manufacturers as well as being mounted alone. In such a case, it has been difficult to evaluate the reception sensitivity in the final mounting state from the development stage of the receiving unit in the electronic device.

In order to solve such a problem, it is preferable that it is possible to estimate how much the reception sensitivity deteriorates from noise from an electromagnetic noise source. As a technique similar to such an estimation technique, a method for estimating a bit error rate (BER) due to electromagnetic noise is known, as described in Non-Patent Documents 1 to 3, for example. In this estimation method, the amplitude probability distribution of electromagnetic noise is measured, and the BER is estimated based on the amplitude probability distribution. For example, an apparatus described in Patent Document 1 is known as an amplitude probability distribution measuring apparatus.
Japanese Patent No. 3156152 K. Wiklundh, "Relation between the amplitude probability distribution of an interfering signal and its impact on digital radio receivers", IEEE Trans. On Electromagnetic Compatibility, Vol.48, No.3, pp.537-544, Aug. 2006 Y. Matsumoto, "On the Relation Between the Amplitude Probability Distribution of a Noise and Bit Error Probability", IEEE Trans. On Electromagnetic Compatibility, Vol.49, No.4, pp.940-941, Nov. 2007 Hori, et al., “Evaluation method of internal interference noise in digital wireless communication devices”, Electronics Packaging Society Conference, 2006

  However, in actual development sites, although BER can be used as an evaluation value, there is a demand to measure the degree of deterioration of reception sensitivity with respect to a reference value rather than BER, and the above estimation technique did not satisfy the demand. . The above estimation technique is applicable only to a single carrier scheme in which a carrier wave is distributed in a single frequency band. On the other hand, in recent years, a multi-carrier system using a carrier of a plurality of divided frequency bands (hereinafter referred to as sub-channels) has become widespread as a communication system from the viewpoint of efficient use of radio waves and communication stability. There has been a demand to obtain a degree of deterioration of reception sensitivity in multi-carrier electronic devices. As a typical technique for realizing the multi-carrier scheme, an OFDM (Orthogonal Frequency Division) adopted in ISDB-T (Integrated Services Digital Broadcasting for Terrestrial) digital television, IEEE802.11a / g standard wireless LAN, and the like. Multiplexing: orthogonal frequency multiplexing).

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an apparatus and a method for estimating deterioration of reception sensitivity in a multi-carrier electronic device.

In order to achieve the above object, a sensitivity deterioration estimation system according to the present invention includes (1) a sensitivity for calculating a degree of deterioration of reception sensitivity at a receiving unit of an evaluated communication device based on electromagnetic noise radiated from the evaluated communication device. A degradation estimation system, a frequency conversion unit that converts an input signal related to electromagnetic noise into an intermediate frequency, an A / D conversion unit that converts an output signal of the frequency conversion unit into a digital signal, and a plurality of multicarrier signals A plurality of filtering means provided in parallel to filter the output signal of the A / D conversion means for each of the subchannels, and envelope detection of the output signal of the filtering means provided for each filtering means. A plurality of envelope detection means to perform, and a plurality of envelope detection means provided for each envelope detection means to measure the amplitude probability distribution of the output signal of each envelope detection means Based on the width probability distribution measuring means, the BER calculating means for calculating the bit error rate (BER) over all subchannels based on the amplitude probability distribution measured by each amplitude probability distribution measuring means, and the BER calculated by the BER calculating means Sensitivity deterioration calculation means for calculating a degree of sensitivity deterioration relative to the reference sensitivity is provided.

  According to the present invention, the amplitude probability distribution is measured for each subchannel used in the multicarrier signal, and the BER over all subchannels is calculated based on each amplitude probability distribution, and relative to the reference sensitivity based on the BER. The degree of sensitivity degradation is calculated.

  As an example of a preferred aspect of the present invention, (2) the BER calculation means calculates the arithmetic average value of BER calculated from the amplitude probability distribution measured by each amplitude probability distribution measurement means before error correction over all subchannels. After calculating as the BER, a method is proposed in which an approximate value using a BER reduction amount by an appropriate noise model such as stationary Gaussian noise is calculated as the BER after error correction. To do. According to the present invention, since the degree of deterioration of the reception sensitivity is calculated using the BER after error correction processing that directly corresponds to the reception sensitivity, a value closer to the actual value can be obtained.

  Further, as an example of a preferred aspect of the present invention, (3) the number of subchannels and band values in the filtering means, and the number of envelope detection means corresponding to the number of subchannels and the amplitude probability distribution measuring means We propose a device with setting value changing means for changing the number according to the structure of the multicarrier signal to be evaluated. Furthermore, (4) what is provided with the setting value change means which changes the setting value in the said BER calculation means and a sensitivity deterioration calculation means is proposed. ADVANTAGE OF THE INVENTION According to this invention, the suitable estimation according to the various standards of the target multicarrier signal is attained.

  An example of the sensitivity degradation estimation method according to the present invention is as follows. (5) The sensitivity degradation estimation system according to any one of (1) to (4) is used, and the frequency and bandwidth of the subchannel are set as the reception sensitivity. It is characterized in that the deterioration degree or BER of the reception sensitivity is estimated by making the same as the frequency and bandwidth of the subchannel of the communication device to be evaluated for evaluating the deterioration degree.

  Another example of the sensitivity degradation estimation method according to the present invention is (6) using the sensitivity degradation estimation system according to any one of (1) to (4) above to evaluate electromagnetic noise received by a probe or an antenna. It is characterized by doing.

  In addition, another example of the sensitivity deterioration estimation method according to the present invention is (7) an evaluation target for evaluating the deterioration degree of reception sensitivity using the sensitivity deterioration estimation system according to any one of (1) to (4) above. The electromagnetic noise generated from the communication device itself is received and evaluated by an antenna attached to the evaluated communication device for wireless communication.

  As described above, according to the present invention, the amplitude probability distribution is measured for each subchannel used in the multicarrier signal, and the BER over all subchannels is calculated based on each amplitude probability distribution. Based on this, the degree of sensitivity degradation relative to the reference sensitivity is calculated. Therefore, it is useful when developing and designing various electronic devices on which a multicarrier signal receiver is mounted.

  A sensitivity deterioration estimation system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an example of a sensitivity deterioration estimation system. FIG. 2 is a configuration diagram of another example of the sensitivity deterioration estimation system.

  As shown in FIG. 1, the sensitivity deterioration system according to the present embodiment operates an electronic device 1 that is a source of electromagnetic noise in a shield box 2 that blocks intrusion of electromagnetic waves from the outside. The electronic apparatus 1 is a device including a multicarrier signal receiver such as a single digital television receiver or a digital television tuner device, or a computer or portable device connected to a digital television tuner device, for example. It is a device that operates in cooperation with a multicarrier signal receiver such as a terminal. The sensitivity deterioration estimation system according to the present invention calculates the degree of deterioration of reception sensitivity in the multi-carrier signal reception unit by electromagnetic noise radiated by these electronic devices due to its own operation.

  A probe 3 for detecting electromagnetic noise radiated from the electronic device 1 is disposed in the shield box 2. An example of the probe 3 is a dipole antenna. Further, as shown in FIG. 2, it is also effective to use the antenna 1b of the wireless receiver itself mounted on the electronic device 1 as an antenna for receiving electromagnetic noise.

  The electromagnetic noise detected by the probe 3 is input to the spectrum analyzer 100. In the present embodiment, spectrum analyzer 100 is used only as a means for selecting electromagnetic noise in the same frequency band as the radio signal to be evaluated for sensitivity degradation and converting the frequency to a predetermined intermediate frequency (IF). Do not use other functions. As shown in FIG. 1, the spectrum analyzer 100 includes a frequency mixing type frequency converter 110, specifically, an oscillator 111 and a mixer 112. Further, the spectrum analyzer 100 includes an IF filter 120 that allows only a signal in the intermediate frequency band to pass.

  The electromagnetic noise down-converted to the intermediate frequency by the spectrum analyzer 100 is input to the amplitude probability distribution measuring apparatus 200. As shown in FIG. 1, the amplitude probability distribution measuring apparatus 200 includes an A / D converter 210 that performs analog-digital conversion on an input signal, a digital filter 220 for the input signal that has been A / D converted, and a filtered signal. On the other hand, an envelope detection unit 230 that performs envelope detection processing and an amplitude probability distribution measurement unit 240 that measures an amplitude probability distribution from the envelope signal are provided. Here, the digital filter 220, the envelope detection unit 230, and the amplitude probability distribution measurement unit 240 are provided in parallel by the number K of subcarriers of the multicarrier signal. The digital filter 220 is set so as to pass only each subcarrier band of the multicarrier signal.

  The measurement result of the amplitude probability distribution for each subchannel in the amplitude probability distribution measuring apparatus 200 is input to the computer 300. As shown in FIG. 1, the computer 300 includes a BER calculation unit 310 that calculates a bit error rate (BER) from the amplitude probability distribution for each subchannel input from the amplitude probability distribution measurement apparatus 200, and a BER calculation unit 310. A sensitivity deterioration calculation unit 320 that calculates the degree of reception sensitivity deterioration based on the calculated BER, a display unit 330 that displays and outputs the deterioration degree calculated by the sensitivity deterioration calculation unit 320, and a storage unit 340 that stores various data. The BER calculation unit 310, the sensitivity deterioration calculation unit 320, and the control unit 350 that controls the operation of the amplitude probability distribution measuring apparatus 200.

  The storage unit 340 stores each data received from the amplitude probability distribution measuring device 200, each data calculated by the BER calculating unit 310, and each data calculated by the sensitivity deterioration calculating unit 320, as well as the amplitude probability distribution measuring device 200 / BER. Various parameters used by the calculation unit 310 and the sensitivity deterioration calculation unit 320 are stored. Various parameters stored in the storage unit 340 are set in advance, and are changed by the evaluator as necessary, such as changing the measurement target.

  The control unit 350 controls the operations of the amplitude probability distribution measuring apparatus 200, the BER calculation unit 310, and the sensitivity deterioration calculation unit 320 based on various parameters stored in the storage unit 340. Specifically, the number of sets of the digital filter 220, the envelope detection unit 230, and the amplitude probability distribution measurement unit 240 provided in parallel in the amplitude probability distribution measurement apparatus 200 according to the standards and specifications of the multicarrier signal, And the frequency band is set. In addition, the BER calculation unit 310 and the sensitivity deterioration calculation unit 320 are provided with various parameters related to the standards and specifications of the multicarrier signal.

Next, the operation of the BER calculation unit 310 will be described. First, the functional configuration of the receiver in the interfered radio system assumed in the present invention will be described with reference to FIG. The receiver in the interfered radio system may be an electronic device that operates in cooperation with the electronic device 1 in addition to the electronic device 1 itself that is an electromagnetic noise source as described above. For example, as shown in FIG. 3, the receiver 10 includes a frequency converter 11, an A / D converter 12, a fast Fourier transformer 13, a frequency and time deinterleaver 14, a demapper 15, a bit interleaver 16, and a Viterbi decoder. 17, a byte interleave unit 18, and an RS decoder unit 19. The BER calculation unit 310 first calculates a bit error rate P _{(dec # in)} before error correction, and then calculates a bit error rate P _{(dec # out)} after error correction from P _{(dec # in)} . Refer to FIG. 3 for the assumed signal position of each bit error rate P _{(dec # in)} and P _{(dec # out)} .

  The probability amplitude distribution APD (x) for each subcarrier obtained in the amplitude probability distribution measuring unit 240 of the amplitude probability distribution measuring apparatus 200 is expressed by the following equation (1) as a complementary function of the cumulative distribution F (x) of x. expressed.

That is, the amplitude probability distribution means a distribution of a probability that a variable exceeds a certain threshold (= excess probability). In particular, the amplitude probability distribution in the time series noise measurement is obtained by the ratio of the total time when the measured signal level exceeds a certain threshold and the total measurement time. The BER calculation unit 310 calculates an approximate value of the bit error rate P _{(dec # in)} before error correction using the following equation (2).

Where each parameter is
APDk (x): amplitude probability distribution of the kth subcarrier K: number of subcarriers (number of subcarriers used for information transmission)
A _k : RMS amplitude of the _kth subcarrier m _k : Number of bits transmitted per symbol of the kth subcarrier β _k : 1/2 of the normalized minimum intersymbol distance in the kth subcarrier
Is defined.

Note that the assumptions in the equation (2) are as follows:
1) Demodulation in the interfered radio communication system is performed by synchronous detection, and the demodulator is in a completely synchronized state. 3) The measurement frequency of amplitude probability distribution measuring apparatus 200 is equal to each subcarrier frequency in the interfered radio communication system 4) The measurement bandwidth of amplitude probability distribution measuring apparatus 200 is the matched filter bandwidth (subchannel) in the interfered radio communication system Equal to (bandwidth). Note that the above equation (2) is considered to be the arithmetic average of the bit error rate in each subcarrier.

Then, BER calculation unit 310, as shown in the following equation (3), applies the function f with respect to uncorrected bit error rate P _{(dec # in),} bit error rate P after error correction _{(dec # out)} . FIG. 4 shows an example of a graph of the bit error rate P _{(dec # in)} before correction calculated by the BER calculation unit 310 and the bit error rate P _{(dec # out)} after error correction. The horizontal axis represents the signal level per bit, and the vertical axis represents the bit error rate.

  Here, the function f depends on the nature of the noise input to the receiver, but an approximate value is obtained assuming an appropriate noise model. For example, as a typical example, an approximate expression for calculating a BER reduction amount for stationary Gaussian noise is well known for various error correction methods. Alternatively, the following document reports an example of estimating BER for periodic interference noise superimposed on receiver Gaussian noise. K. Gotoh, Y. Matsumoto, and S. Ishigami, "Performance evaluation of multicarrier wireless systems affected by a disturbance using amplitude probability distribution", in Proc. EMC Europe Workshop, Paris, June, 2007.

The sensitivity deterioration calculation unit 320 calculates the degree of reception sensitivity deterioration at the receiver of the interfered radio system based on the error-corrected bit error rate P _{(dec # out)} calculated by the BER calculation unit 310. Specifically, as shown in FIG. 5, the bit error rate P ₀ at the receiver of the interfered radio system without electromagnetic interference, that is, only the receiver thermal noise is obtained in advance by measurement or calculation, previously stored in the minimum reception level E each storage unit 340 to previously obtain a bit error rate P _min when the _min in the receiver from the bit error rate P _0. Here, the minimum reception level E _min means the minimum value of the reception level necessary for obtaining appropriate reception data. For example, in the case of a digital television, it is the reception level necessary for moving image demodulation. Desensitization calculating unit 320, as shown in FIG. 5, the bit error rate P after error correction calculated by the BER calculation unit 310 _{(dec # out),} the reception level E _x corresponding to the bit error rate P _min the calculated, calculates the difference between the minimum reception level E _min and the received level E _x as a degree of deterioration of reception sensitivity. The unit of degree of deterioration of the reception sensitivity is the same as the received level E _x and the minimum reception level E _min, it is preferable to use a [dB].

  The display unit 330 displays and outputs the deterioration degree calculated by the sensitivity deterioration calculation unit 320 in a format that the evaluator can intuitively understand, such as “sensitivity deterioration is 3 dB”. Further, the display unit 330 displays the graphs shown in FIGS. 4 and 5, the numerical values related to the graphs, the output result of the amplitude probability distribution measuring apparatus 200, and the graphed version thereof as necessary. Is preferred.

  As described above, according to the reception sensitivity degradation estimation system according to the present embodiment, the degree of sensitivity degradation relative to the reference sensitivity is calculated and displayed, which is useful in the development and design of various electronic devices. In addition, the reception sensitivity degradation estimation system according to the present embodiment can easily cope with various multicarrier signals by updating various parameters related to the multicarrier signals stored in storage unit 340. In particular, according to the present embodiment, the digital filter 220, the envelope detector 230, and the amplitude probability distribution measuring unit 240 provided in parallel in the amplitude probability distribution measuring apparatus 200 according to the number of subcarriers and the subcarrier frequency band. Since the number of sets and the frequency band can be set, it is highly convenient.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this. For example, in the above embodiment, the probe 3 is provided to detect electromagnetic noise from the electronic device 1, but as shown in FIG. 2, when the electronic device 1 includes an antenna, this is used. You may do it.

  Further, in the above embodiment, in order to construct a reception sensitivity deterioration estimation system, various functional units are distributed and implemented in three apparatuses, that is, the spectrum analyzer 100, the amplitude probability distribution measuring apparatus 200, and the computer 300. These implementations are unquestioned. For example, the frequency conversion unit 110 and the IF filter 120 in the spectrum analyzer 100 may be mounted on the amplitude probability distribution measuring apparatus 200.

  The present invention can be used in the field of broadcasting / communication using multicarrier signals in a transmission medium, and the transmission medium may be wireless or wired. Suitable for estimating the degree of deterioration of reception sensitivity in digital television single receivers, digital television receivers, wireless LAN devices, power line communication devices, etc. used by being mounted on computers, portable game terminals, car navigation devices, etc. is there. Based on the degree of deterioration of the reception sensitivity, it is possible to evaluate the magnitude of noise that affects the communication device.

The block diagram which shows an example of a sensitivity degradation estimation system. The block diagram which shows the other example of a sensitivity degradation estimation system. Functional configuration diagram of the receiver in the interfered radio system Graph of bit error rate before and after error correction Graph explaining the principle of calculating the degree of deterioration of reception sensitivity

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electronic device, 2 ... Shield box, 3 ... Probe, 100 ... Spectrum analyzer, 110 ... Frequency converter, 120 ... IF filter, 200 ... Amplitude probability distribution measuring device, 210 ... A / D converter, 220 ... Digital filter , 230 ... envelope detector, 240 ... amplitude probability distribution measurement unit, 300 ... computer, 310 ... BER calculation unit, 320 ... sensitivity deterioration calculation unit, 330 ... display unit, 340 ... storage unit, 350 ... control unit

Claims (7)

A sensitivity deterioration estimation system that calculates a deterioration degree of reception sensitivity in a receiving unit of the communication device to be evaluated based on electromagnetic noise radiated from the communication device to be evaluated,
Frequency conversion means for converting an input signal related to electromagnetic noise into an intermediate frequency;
A / D conversion means for converting the output signal of the frequency conversion means into a digital signal;
A plurality of filtering means provided in parallel to filter the output signal of the A / D conversion means for each of the sub-channels for a plurality of divided frequency bands (hereinafter referred to as “sub-channels”);
A plurality of envelope detection means provided for each filtering means for performing envelope detection of the output signal of each filtering means;
A plurality of amplitude probability distribution measuring means provided for each envelope detection means for measuring the amplitude probability distribution of the output signal of each envelope detection means;
BER calculating means for calculating a bit error rate (BER) over all subchannels based on the amplitude probability distribution measured by each amplitude probability distribution measuring means;
A sensitivity deterioration estimation system comprising: a sensitivity deterioration calculation unit that calculates a degree of sensitivity deterioration relative to a reference sensitivity based on the BER calculated by the BER calculation unit. The BER calculating means calculates the arithmetic average value of BER calculated from the amplitude probability distribution measured by each amplitude probability distribution measuring means as the BER before error correction over all subchannels, and then calculates the BER before error correction. The BER after error correction is calculated by approximation using a BER reduction amount assuming an appropriate noise model. The sensitivity deterioration estimation system according to claim 1. And a setting value changing means for changing the number of subchannels and the band value in the filtering means, and the number of envelope detection means and the number of amplitude probability distribution measuring means corresponding to the number of subchannels. The sensitivity deterioration estimation system according to claim 1. The sensitivity deterioration estimation system according to claim 1, further comprising setting value changing means for changing setting values in the BER calculating means and the sensitivity deterioration calculating means. Using the sensitivity degradation estimation system according to any one of claims 1 to 4, the frequency and bandwidth of the subchannel are the same as the frequency and bandwidth of the subchannel of the communication device to be evaluated for evaluating the degree of degradation of reception sensitivity. A sensitivity deterioration estimation method characterized by estimating the degree of deterioration or BER of reception sensitivity by A sensitivity deterioration estimation method, comprising: evaluating the electromagnetic noise received by a probe or an antenna using the sensitivity deterioration estimation system according to claim 1. An electromagnetic noise generated from an evaluated communication device itself that evaluates the degree of deterioration of reception sensitivity using the sensitivity deterioration estimation system according to any one of claims 1 to 4 for the wireless communication to the evaluated communication device. A sensitivity degradation estimation method characterized by receiving and evaluating with an antenna attached to the antenna.

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