JP2006261826A - Receiving apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving apparatus and a receiving method capable of demodulating received data stably even against amplitude variations of a received signal and a code error due to noise. <P>SOLUTION: An incidence rate calculation section 140 obtains an incidence rate RF of received pulses on the basis of the number of the received pulses RP received by each update time UT and known transmission rate information of an OOK modulation signal, and a threshold value conversion section 150 converts the incidence rate RF into a threshold voltage Vt for the comparison by a comparator 111 of a level comparison section 110 and controls the incidence rate RF of the received pulses so that the incidence rate RF is convergent to a reference value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving apparatus and a receiving method for demodulating a modulation signal by a pulse modulation method used in the fields of wireless communication and optical communication.

  Pulse modulation methods include the OOK (On Off Keying) modulation method that transmits information depending on the presence or absence of a pulse, and the PPM (Pulse Position Modulation) modulation method that transmits information depending on the position of a pulse. When demodulating the pulse modulated signal, a method is known in which the received pulse is compared with a certain threshold voltage and the received data is demodulated as “1” if it is larger than this threshold voltage and “0” if it is smaller. Yes.

  Conventionally, as this type of receiving apparatus, for example, there is one described in Patent Document 1.

  FIG. 13 is a block diagram illustrating a configuration of the receiving device described in Patent Document 1. In FIG. In FIG. 13, the received signal received by the antenna 11 is amplified by the high frequency amplifier 12 and given to the bandpass filter 13 to extract a necessary signal. Thereafter, the signal is detected by the envelope detector 14 and compared by the discriminator 16. At this time, the comparison voltage supplied to the discriminator 16 is configured such that the output of the bandpass filter 13 is input to the comparison voltage generator 15 and the comparison voltage generator 15 generates a comparison voltage inversely proportional to the received signal level. Is known.

According to this receiving apparatus, the comparison voltage of the discriminator 16 is controlled to be increased when the received signal level is small, and conversely, it is decreased when the received signal level is large. That is, the received data is demodulated so as to minimize the code error by controlling the comparison voltage of the discriminator according to the received signal level.
JP 7-183922 A

  However, in such a conventional receiving apparatus, a comparison voltage that is inversely proportional to the received signal level is used. Therefore, when the received signal level is always small, the comparison voltage is large, so that it is near the upper side of the pulse signal. If the received signal level is always high or the received signal level is always high, the comparison voltage is low, so the comparison is made based on the lower side of the pulse signal and the noise signal is picked up. There is.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a receiving apparatus and a receiving method capable of demodulating stable received data even with respect to a code error due to amplitude fluctuation or noise of a received signal. To do.

  The receiving apparatus of the present invention compares the amplitude level of a pulse modulated pulse modulated signal with a predetermined threshold value and converts it into binary received data, and generates a reproduction clock having a pulse period from the received data. A clock recovery means, a measuring means for measuring the received data as the number of pulses received every predetermined update period, and the number of data to be received in the update period based on the designated transmission rate information and the update period. Based on the measured number of data calculation means, the measured number of received pulses and the number of data to be received, the appearance rate calculation means for obtaining the appearance rate of received pulses in the update period, the output of the clock recovery means, and the Based on the appearance rate of the received pulse, a configuration including a threshold value calculation means for calculating the threshold value supplied to the comparison means is adopted.

  The reception method of the present invention includes a step of obtaining an appearance rate of a reception pulse for each update period from a received pulse modulation signal, a step of obtaining a threshold value of a reception signal level from the reception pulse appearance rate, and pulse modulated pulse modulation Comparing the amplitude level of the signal with the threshold value and converting it to binary received data.

  According to the present invention, stable received data can be easily demodulated with a simple configuration without using a complicated circuit. Further, it is possible to cope with demodulation of a pulse modulation signal modulated by a carrier wave signal. Furthermore, since it is possible to support a plurality of modulation schemes such as OOK and PPM, it is possible to construct a receiving apparatus that supports a plurality of modulation schemes by a simple method without increasing the circuit scale of the receiving apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 1 of the present invention. The receiving apparatus of this embodiment is an example applied to a receiving apparatus that demodulates a modulation signal by an OOK modulation method.

  In FIG. 1, the receiving apparatus 100 includes a level comparison unit 110 including a comparator 111 and a one-shot circuit 112, a clock recovery unit 120, a counter 130, an appearance rate calculation unit 140 including a multiplier 141 and a divider 142, A threshold conversion unit 150 including a conversion table 151 and a D / A converter 152 is provided.

  The level comparison unit 110 compares the amplitude levels of the pulse modulation signals and converts them into binary reception data BD. The clock recovery unit 120 generates a recovery clock CR having a pulse period from the received data BD. The counter 130 measures the number of received pulses RP for each update time UT based on the reproduction clock CR. The appearance rate calculation unit 140 calculates the appearance rate RF of the received pulse in the period of the update time UT from the number of data RD to be received in the period of the update time UT from the number of received pulses RP measured by the counter 130 and the transmission rate information. . The threshold conversion unit 150 converts the appearance rate RF into a threshold voltage Vt to be given to the level comparison unit 110.

  Hereinafter, the operation of the receiving apparatus 100 configured as described above will be described.

  FIG. 2 is a timing chart for explaining operations in the level comparison unit 110 and the clock recovery unit 120 of the receiving device 100, and FIG. 3 explains operations of the counter 130, the appearance rate calculation unit 140, and the threshold value conversion unit 150 of the receiving device 100. FIG. 4 is a graph showing the conversion rules in the conversion table 151 of the receiving apparatus 100.

  As shown in FIG. 2, the OOK modulation signal is modulated on the transmission side according to the rule of “0” if the transmission data is “0” and “1” if the transmission data is “1”. Assume that it is scrambled by a code having pseudo-random characteristics.

  The level comparison unit 110 of the receiving apparatus 100 inputs an OOK modulation signal, compares the pulse amplitude level with the threshold voltage Vt, detects whether a pulse exists, and outputs a pulse detection PD. The one-shot circuit 112 is a circuit that detects a rising edge of an input signal and outputs a pulse having a constant width. When a pulse is detected by the pulse detection PD detected by the comparator 111, the one-shot circuit 112 is “H” over the width of the pulse period Tp. "If there is no pulse, it is converted to binary received data BD as" L ".

  The clock recovery unit 120 generates a recovery clock CR having a pulse period Tp when received data BD is input, and is generally configured by a phase comparator, a loop filter, a VCO (voltage controlled oscillator), and the like. It can be realized by a PLL (phase locked loop) circuit or the like.

  The counter 130 measures only the data “1” in the received data BD for each designated update time UT and outputs it as the received pulse number RP.

  The multiplier 141 of the appearance rate calculation unit 140 obtains the number of data RD to be received in the period of the update time UT from the designated transmission rate information and the update time UT. The number of data RD to be received here is the number of both “0” and “1” data. That is, it can be obtained by multiplying the transmission rate information and the update time UT. In the example of FIG. 3, since it is assumed that the transmission rate is 1 Mbps and the update time UT is 1 ms, the number of data RD is “1000”. The divider 142 divides the number of received pulses RP, which is measured only in the “1” state actually received in the period of the update time UT, by the number of data RD, so that the appearance of the received pulse in the period of the update time UT. Determine the rate RF. This appearance rate RF indicates how much the number of received pulses of “1” is received with respect to the number of data of “0” and “1” to be received in the period of the update time UT. . In this embodiment, the transmission data to be sent on the transmission side is scrambled by a code having pseudo-random characteristics and OOK-modulated. Therefore, the appearance rate when correctly received without a code error is the pseudo-randomness of the transmission data. Although it is “0.5” due to the characteristics, if a code error or the like occurs, it changes in the range of 0 to 1.0. For example, when the transmission rate is 1 Mbps and the update time UT is 1 ms, the number of “1” data received during the update time UT is “500”, and the number of data “0” and “1” to be received RD Since there are “1000”, the appearance rate is “0.5”. The appearance rate “0.5” at this time is a reference value when there is no code error and the data is correctly received.

  The conversion table 151 of the threshold conversion unit 150 is a table memory that converts a value so that the value of the appearance rate RF is within the range of the threshold voltage Vt for comparison by the comparator 111. FIG. 4 shows that the input appearance rate RF (0 to 1.0) is converted into threshold data TD (−1 to +1) when the control range of the threshold voltage Vt of the comparator 111 is assumed to be −1 to +1. It is a graph showing the state to output, and the conversion rule is “threshold data TD = 2 × (appearance rate RF) −1”. That is, when the appearance rate RF is large, the ratio of receiving “1” pulses is high, so the threshold voltage Vt is increased. When the appearance rate RF is small, the ratio of receiving “1” pulses is increased. Since it is low, it is converted into threshold data TD so that the threshold voltage Vt is lowered. The converted threshold data TD is converted into an analog signal by a D / A converter 152 which is a digital-analog converter, and is given to the comparator 111 as a threshold voltage Vt and controlled.

  The operation as described above is performed every update time UT, and the appearance rate RF is controlled to converge to the reference value “0.5”.

  As described above, according to the first embodiment, the appearance rate RF of the received pulse is obtained from the number RP of received pulses received every update time UT and the transmission rate information of the known OOK modulation signal, and the appearance rate RF is calculated from the appearance rate RF. By converting to the threshold voltage Vt for comparison by the comparator 111 and controlling the appearance rate RF of the received pulse to converge to the reference value “0.5”, stable received data can be easily demodulated with a simple configuration. can do.

  Here, in the first embodiment, the comparator 111 of the level comparison unit 110 is configured to determine the presence / absence of a pulse based on the threshold voltage Vt of the amplitude level of the input pulse. However, hysteresis characteristics such as a Schmitt trigger are used. In this way, a signal such as noise shorter than a prescribed pulse width to be transmitted can be removed. Further, although the update time UT is shown as a time of a fixed period, the time may be defined so as to be shortened or lengthened according to the propagation characteristics of the transmission path through which the pulse modulation signal is transmitted.

(Embodiment 2)
FIG. 5 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 2 of the present invention. In the description of the present embodiment, the same components as those in FIG.

  The difference from the first embodiment is that a receiving apparatus 200 according to the present embodiment receives an OOK modulation signal in which a pulse signal to be transmitted is pulse-modulated by a carrier wave signal, and detects an envelope of the modulation signal. 210 is provided.

  Hereinafter, the operation of the receiving apparatus 200 configured as described above will be described.

  FIG. 6 is a timing chart showing the operation of envelope detection in the detector 210.

  As shown in FIG. 6, the OOK modulation signal is a modulation signal in which a carrier signal, which is a single sine wave signal, is superimposed on a pulse to be transmitted on the transmission side. The detector 210 detects an envelope of the modulation signal (a line in which the maximum points of the modulation signal are smoothly connected). First, the OOK modulation signal is rectified by a diode to cut off the negative portion, and then the resistance is reduced. A detection signal DS is obtained by smoothly connecting waveforms with a low-pass filter composed of a capacitor. Note that the processing and operation of signals after the detection signal DS are the same as those in the first embodiment, and thus description thereof is omitted.

  As described above, according to the second embodiment, by providing the detector 210, it is possible to cope with demodulation of an OOK modulation signal pulse-modulated by a carrier wave signal with a simple configuration without using a complicated circuit. it can.

  Although FIG. 6 shows the case of the OOK modulation method, the basic operation is the same in the PPM modulation method.

(Embodiment 3)
FIG. 7 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 3 of the present invention. The receiving apparatus of this embodiment is an example when applied to a binary PPM modulation system. The same components as those in FIG.

  The difference from Embodiment 1 is that receiving apparatus 300 of this embodiment includes control section 310 that updates (rewrites) the conversion rule contents of conversion table 151 in accordance with the specified modulation scheme information. is there.

  Hereinafter, the operation of the receiving apparatus 300 configured as described above will be described.

  FIG. 8 is a timing chart showing a binary PPM modulation signal, and FIG. 9 is a graph showing a conversion rule of the conversion table 151.

  As shown in FIG. 8, the binary PPM modulation method is a method in which one pulse according to 1-bit information (0 or 1) is allocated and transmitted at one position in any of two pulse slots. A unit indicating 1-bit information composed of two pulse slots is called a symbol, and its data rate is called a symbol rate.

  Due to the characteristics of this binary PPM modulation method, the number of data “RD” of “0” and “1” to be received in the period of the update time UT and the number of received pulses RP of only “1” measured by the counter 130 are the same value. It becomes. Therefore, the reference value of the appearance rate RF when there is no code error and is correctly received is “1.0”, and when a code error or the like occurs, it changes in the range of 0 to 2.0.

  Further, in the transmission rate information input to the multiplier 141 of the appearance rate calculation unit 140, unlike the OOK modulation method, a value obtained by multiplying the symbol rate by m according to the m (m is an arbitrary natural number) value PPM modulation method. Is specified as transmission rate information. Since receiving apparatus 300 according to the present embodiment is based on the binary PPM modulation scheme, transmission rate information is designated as a value obtained by doubling the symbol rate.

  The control unit 310 rewrites the conversion table 151 based on the modulation scheme information so as to have the contents shown in FIG. That is, according to the conversion rule “threshold data TD = (appearance rate RF) −1”, the input appearance rate RF (0 to 2.0) is converted as threshold data TD (−1 to +1). Since subsequent signal processing and operations are the same as those in the first embodiment, description thereof is omitted.

  As described above, according to the third embodiment, by providing the control unit 310 that rewrites the conversion rule contents of the conversion table 151 based on the modulation method information, the binary PPM modulation method can be supported in addition to the OOK modulation method. Therefore, it is possible to construct a receiving apparatus corresponding to a plurality of modulation schemes by a simple method without increasing the circuit scale of the receiving apparatus.

  8 and 9 show an operation example in the case of the binary PPM modulation method, the basic operation is the same in a plurality of m-value PPM modulation methods such as 4-value and 8-value. In this case, it can be dealt with only by rewriting the conversion table 151 in accordance with the conversion rule corresponding to the m-value PPM modulation method.

(Embodiment 4)
FIG. 10 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 4 of the present invention. The receiving apparatus of this embodiment is an example when applied to the OOK modulation method. The same components as those in FIG.

  The difference from Embodiment 3 is that reception apparatus 400 of this embodiment includes quality measurement section 410 that measures the reception quality state of the received pulse modulation signal.

  Hereinafter, the operation of the receiving apparatus 400 configured as described above will be described.

  FIG. 11 is a graph showing the relationship of the optimum discrimination level with respect to the carrier power / noise power ratio CNR in the OOK modulation method, and FIG. 12 is a graph showing the conversion rules of the conversion table 151.

  In general, when a transmitted pulse is identified, it may be erroneously identified by noise mixed in the transmission path, which is called a code error. Factors that dominate the code error include carrier power to noise power ratio CNR and timing jitter. In particular, in the case of the OOK modulation system, the carrier power to noise power ratio CNR is important because of modulation by amplitude. It becomes a parameter. The code error rate can be obtained from the amplitude probability density distribution function of the received pulse on which transmission line noise is superimposed, the occurrence probability of “1” and “0” of the pulse, and the like. In the case of the OOK modulation method, the optimum discrimination level can be obtained from the probability density distribution function, and the relationship between the carrier power to noise power ratio CNR and the optimum discrimination level is defined, and the graph shown in FIG. It is known to become a characteristic. That is, by demodulating with the optimum threshold according to the carrier power-to-noise power ratio CNR of the received pulse modulation signal, it is possible to demodulate the received data stably against the code error due to the amplitude fluctuation of the received signal and noise. it can.

  The quality measurement unit 410 is a block that measures the carrier power to noise power ratio CNR of the received pulse modulation signal, and includes an A / D converter 411 that performs analog-digital conversion and a calculation unit 412. Based on the carrier power-to-noise power ratio CNR measured at each update time UT, the calculation unit 412 calculates the offset value of the conversion rule and outputs it to the control unit 310 as an offset OS.

  Now, it is assumed that the carrier power to noise power ratio CNR measured during an arbitrary update time UT is 12 dB. The optimum discrimination level at 12 dB is 0.55 from FIG. Further, the optimum discrimination level in FIG. 11 is shown when the absolute amplitude is “1”. Since the threshold range of the threshold converter 150 is −1 to +1 and the absolute amplitude is “2”, the arithmetic unit 412 performs correction so as to match the absolute amplitude “2”. That is, the optimum threshold value when the carrier power to noise power ratio CNR is 12 dB is 2 × 0.55 = 1.1, and since “1.1” is the case where the threshold value range is 0 to 2, the actual threshold value is obtained. Apply correction to the range -1 to +1. That is, since it is only necessary to correct by -1, 1.1-1 = 0.1 is an actual optimum threshold value. This means that the threshold when the appearance rate RF is the reference value 0.5 is changed from “0” to “0.1”, and as shown in FIG. 12, the conversion rule is only “0.1”. Change to apply an offset to the upper side. Actually, the calculation unit 412 gives a change instruction to the control unit 310 using “−0.9” obtained by adding “0.1” to the offset OS that was originally “−1” as the offset OS. The control unit 310 updates the conversion table 151 with the changed conversion rule “threshold data TD = 2 × (appearance rate RF) −0.9” (graph shown by a solid line in FIG. 12).

  As described above, according to the fourth embodiment, by including the quality measuring unit 410 that measures the reception quality state of the received pulse modulation signal, the optimum threshold is set according to the reception quality state of the received pulse modulation signal. Since it can be demodulated, it is possible to demodulate the received data stably against the code error due to the amplitude fluctuation of the received signal and noise.

  Although FIG. 11 shows an example of the carrier power to noise power ratio CNR, quality information such as the signal to noise power ratio SNR may be used. In this way, the modulation scheme and propagation path to be applied can be used. Thus, it is possible to construct a receiving apparatus that can perform optimal demodulation according to the characteristics.

  In the fourth embodiment, the offset OS by the quality measuring unit 410 is input to the control unit 310, and the control unit 310 changes the offset value of the conversion rule. The reception quality measurement result may be used in any way as long as the rate is converted into the threshold voltage.

  The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this.

  Further, the present invention can be incorporated as a wireless terminal, for example, and can also be realized as a mobile communication system including the receiving apparatus and the receiving method.

  In the above embodiment, the names of the receiving device and the receiving method are used. However, this is for convenience of explanation, and it is needless to say that the transmitting / receiving device, the transmitting / receiving method, and the like may be used.

  Further, the type, number, connection method, and the like of each circuit unit constituting the receiving apparatus are not limited to the above-described embodiments.

  The receiving device and the receiving method according to the present invention have an effect that it is possible to easily demodulate stable received data with a simple configuration, and as a pulse modulation type receiving device used in the field of wireless communication or optical communication. Useful.

The block diagram which shows the structure of the receiver which concerns on Embodiment 1 of this invention. Timing chart for explaining operations in the level comparison unit and the clock recovery unit of the receiving apparatus according to the first embodiment. Timing chart for explaining operations of the counter, the appearance rate calculation unit, and the threshold conversion unit of the receiving apparatus according to Embodiment 1 above The graph which shows the conversion rule in the conversion table of the receiver which concerns on the said Embodiment 1. The block diagram which shows the structure of the receiver which concerns on Embodiment 2 of this invention. Timing chart for explaining the operation of envelope detection in the detector of the receiving apparatus according to the second embodiment The block diagram which shows the structure of the receiver which concerns on Embodiment 3 of this invention. Timing chart explaining operation of binary PPM modulated signal The graph which shows the conversion rule in the conversion table of the receiver which concerns on the said Embodiment 3. The block diagram which shows the structure of the receiver which concerns on Embodiment 4 of this invention. The graph which shows the relationship of the optimal discrimination | determination level with respect to carrier power to noise power ratio in an OOK modulation system The graph which shows the conversion rule in the conversion table of the receiver which concerns on the said Embodiment 4. Block diagram showing the configuration of a conventional receiving apparatus

Explanation of symbols

100, 200, 300, 400 Receiver 110 Level comparison unit 111 Comparator 112 One-shot circuit 120 Clock recovery unit 130 Counter 140 Appearance rate calculation unit 141 Multiplier 142 Divider 150 Threshold conversion unit 151 Conversion table 152 D / A converter 210 Detector 310 Control unit 410 Quality measurement unit 411 A / D converter 412 Calculation unit

Claims (6)

A comparison means for comparing the amplitude level of the pulse-modulated pulse-modulated signal with a predetermined threshold value and converting it to binary received data;
A clock recovery means for generating a recovery clock of a pulse period from the received data;
Measuring means for measuring the received data as the number of pulses received every predetermined update period;
Based on the designated transmission rate information and the update period, a data number calculating means for obtaining the number of data to be received in the update period;
Based on the measured number of received pulses and the number of data to be received, an appearance rate calculating means for obtaining an appearance rate of received pulses in the update period;
And a threshold value calculating means for calculating the threshold value supplied to the comparing means based on the output of the clock recovery means and the appearance rate of the received pulse.   The receiving apparatus according to claim 1, wherein the threshold value calculating unit calculates the threshold value so that the appearance rate of the received pulse converges to a predetermined reference value.   The receiving apparatus according to claim 1, further comprising: a detection unit that inputs a pulse modulation signal pulse-modulated by a carrier wave signal and detects an envelope of the modulation signal.   4. The control unit according to claim 1, further comprising a control unit configured to update a conversion rule for converting the appearance rate of the received pulse into the threshold value according to a modulation method of the pulse modulation signal. A receiving device according to claim 1.   The receiving apparatus according to claim 1, further comprising a quality measuring unit that measures a reception quality state of the received pulse modulation signal. From the received pulse modulation signal, obtaining the appearance rate of the received pulse for each update period;
Obtaining a threshold of a received signal level from the received pulse appearance rate;
A step of comparing the amplitude level of the pulse-modulated pulse-modulated signal with the threshold value and converting it into binary received data.

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