JP4952491B2 - Mirror subcarrier demodulating circuit and receiving apparatus having the same - Google Patents

Description

  The present invention relates to demodulation processing of received data in a communication system such as UHF band RFID (Radio Frequency IDentification) that performs communication using a protocol defined in EPC global, and in particular, mirror subcarrier data transmitted from a tag. The present invention relates to a mirror subcarrier demodulation circuit for receiving and demodulating, and a receiving apparatus including the same.

Conventionally, there is a method disclosed in the following (Patent Document 1) as an RFID demodulation method. According to this document, a radio signal is converted into an analog signal of an I signal and a Q signal by an RF reception unit, and each obtained waveform is sampled after being converted into digital data by an AD conversion unit, and the sampled data continues. Based on the positive data number (positive data length) and the negative data number (negative data length), the I signal and the Q signal are determined to be 0 or 1, respectively, and demodulated. In the case where the demodulation result of the I signal is different from the demodulation result of the Q signal, it is described that the result demodulated with the larger signal strength is adopted.
US Pat. No. 6,501,807

  However, the above-described conventional demodulation method has a problem that if a large pulse noise occurs in a noisy environment, the sign of the sampling data changes and there is a high possibility of erroneous determination of 1-bit data.

  Further, since a circuit for separately decoding the I signal and the Q signal is necessary, there is a problem that the circuit scale becomes large.

  An RFID demodulation circuit is required to reliably demodulate more tag information under any environment.

  An object of the present invention is to provide a mirror subcarrier demodulating circuit capable of demodulating received data from a communication partner more reliably even under noise or interference from other devices, and a receiving apparatus including the same. .

  The present invention receives mirror subcarrier code data, detects the peak of the combined waveform of the I signal and Q signal, sets the acquisition timing of symbol data from the detection timing, and sets the I data and Q at the set acquisition timing. Each of the data is captured and stored as symbol data, and a correlation operation based on a set value M is performed using a plurality of symbol data in a 1-bit period, and 0 or 1 of the 1-bit data is determined. .

  As a result, demodulation is possible if only the peak data to be acquired can be acquired reliably, so that the effects of noise that occurs outside the symbol data acquisition timing can be reduced, and tagging is possible even under noise or interference from other devices. It is possible to demodulate the received data from the etc. more reliably.

  According to the present invention, the mirror subcarrier code data is received, the peak of the combined waveform of the I signal and the Q signal is detected, the symbol data acquisition timing is set from the detection timing, and the I data is set at the set acquisition timing. And Q data are captured and stored as symbol data, a correlation operation based on a set value M is performed using a plurality of symbol data in a 1-bit period, and 0 or 1 of the 1-bit data is determined. Therefore, if only the peak data to be acquired can be reliably acquired, demodulation is possible, so the influence of noise generated at portions other than the acquisition timing of symbol data can be reduced, and tags etc. even under noise or interference from other devices Therefore, a mirror subcarrier demodulating circuit that can demodulate the received data from the receiver more reliably can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments can be mutually used in related portions.

(Embodiment 1)
FIG. 1 is a configuration diagram of an RFID demodulation circuit according to Embodiment 1 of the present invention, and shows an RFID demodulation circuit of a receiving apparatus that receives and demodulates data of a mirror subcarrier code from a tag that is a communication partner. .

  In FIG. 1, reference numeral 101 denotes an antenna that receives an RFID radio signal in the UHF band. Reference numeral 102 denotes an RF receiving unit that converts an RF signal received by the antenna 101 into an analog electric signal of an I signal and a Q signal, and includes an orthogonal modulator, an analog filter, and the like. Reference numeral 103 denotes an AD converter that converts the analog signals of the I signal and the Q signal converted by the RF receiver 102 into digital signals.

  A waveform generation unit 104 generates a combined waveform of the digital I signal and Q signal converted by the AD conversion unit 103, and 105 detects a peak value of the peak value of the IQ combined waveform obtained by the waveform generation unit 104. Reference numeral 106 denotes a peak interval detection unit that detects the peak value interval of the combined waveform detected by the peak detection unit 105 and generates timing for capturing received data.

  107 is a counter unit that counts the number of acquired symbol data, 108 is a temporary storage unit that latches and temporarily stores I data and Q data at the timing set by the peak interval detection unit 106, and 109 is A calculation unit 110 that performs a correlation calculation of the acquired I data and Q data based on the setting value M of the mirror subcarrier, and 110 determines data of 0 or 1 from the correlation calculation result of a plurality of symbol data by the calculation unit 109 The determination unit 111 is a shift register unit that sequentially stores 1-bit data determined by the data determination unit 110.

  The operation of the RFID demodulating circuit configured as described above will be described below.

  FIG. 2 is an operation flowchart of the RFID demodulation circuit according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing signal waveforms of received data according to Embodiment 1 of the present invention, where the vertical axis represents voltage values and the horizontal axis represents time.

  FIG. 3A shows a signal waveform of a burst signal or pilot tone added to the first half of the preamble in the I signal or Q signal, and is output from the RF receiver 102. FIG. 3B shows a combined waveform of the I signal and the Q signal shown in FIG. FIG. 3C shows a preamble waveform of the I signal or the Q signal when M = 2. FIG. 3D shows a composite waveform of the preamble waveform of FIG.

  As shown in FIG. 2, the RFID demodulating circuit first transmits a command to the tag and then receives data (step 101). When the RF signal received by the antenna 101 is received by the RF receiving unit 102, an analog electric signal (FIG. 3 (see (a)) (step 102), and the AD converter 103 converts the analog electric signal into a digital signal (step 103).

Assuming that I data and Q data converted into digital signals are I and Q data sampled at the same timing, respectively, In and Qn, the waveform generation unit 104 synthesizes the data into In ² + Qn ² data to generate an IQ combined signal (see FIG. 3 (see FIG. 3B), and the peak detection unit 105 searches for the peak value of the combined waveform (FIG. 3B).

  Note that the synthesis of I data and Q data may be a simple circuit configuration as | In | + | Qn |, or may be a synthesized waveform with reduced noise added to the signal as | In + In + 1 | + | Qn + Qn + 1 |. Good.

  In the detection of the peak value, at least two pieces of sampling data are always temporarily stored, and a point in time when the change in the value of two consecutive sampling data changes from an increase to a decrease is taken as a peak value. In addition, 3 or more sampling data is temporarily stored, and the value of any number of 3 or more consecutive sampling data continuously increases, and then the 3 or more sampling data continuously decreases The point in time at which this is detected may be the peak value. In this way, erroneous detection of peaks due to pulse noise or the like can be reduced.

  When the peak value is detected by the peak detection unit 105, the interval to the next peak value is counted at the sampling frequency, and if it is detected that an arbitrary number of continuous peak intervals are within an arbitrary difference, The average value T is set as a data capture timing interval.

For example, as shown in FIG. 3B, assuming that the interval between four consecutive peaks (sampling count number until the next peak) is T1, T2, and T3, and the allowable difference between the intervals is 2 sampling counts, respectively. Difference T1-T2, T2-T3, and T1-T3 are | T1-T2 | ≦ 2 & | T2-T3 | ≦ 2 & | T1-T3 | ≦ 2
Then, the peak interval T is set as the average T = (T1 + T2 + T3) / 3.

  The peak interval T is set by detecting a peak within the period of the pilot tone by adding a burst signal portion or pilot tone in the first half of the preamble.

  When the peak interval T is set, peaks within an arbitrary count before and after are detected in consideration of the waveform tolerance based on the peak interval T. For example, assuming that the arbitrary count number is 3, the peak is detected by the above-described peak detection method while the counter of the peak interval detection unit is T-3 or more and T + 3 or less.

  When a peak is detected as shown in FIG. 3D, 1-bit I data and Q data are stored in the temporary storage unit 108 at the detection timing. If no peak is detected by the count T, I data and Q data are temporarily captured and stored at the count T, and if no peak is detected by the count T + 3, the value is set as one symbol data. . If a peak can be detected before the count T + 3 (step 105), I data and Q data are taken in at the detection timing and stored as one symbol data in the temporary storage unit 108 (step 106).

  The counter of the peak interval detector 106 is reset when the count is T or when a peak is detected. The number of data capture is counted by the counter unit 107, and in the case of mirror subcarrier communication with the setting value M = 2, four symbols are captured and stored in the temporary storage unit (step 107).

  When the arithmetic unit 109 uses four symbol data of each of I data and Q data, I1, I2, I3, I4, Q1, Q2, Q3, and Q4 in the order of taking in the four symbol data of I and Q respectively. (FIG. 3 (c)), correlation calculation (I1-I2) (I3-I4) + (Q1-Q2) (Q3-Q4) is performed (step 108), and the MSB (most significant bit) of the calculation result is 1. If the MSB is 0, the 1-bit data is determined to be 1 (step 109).

  The correlation calculation may be (I1-I4) (I2-I3) + (Q1-Q4) (Q2-Q3). Further, correlation calculation (I1-I3) (I2-I4) + (Q1-Q3) (Q2-Q4) is performed, and when the MSB of the calculation result is 0, the 1-bit data is determined to be 1, and the MSB When 1 is 1, the 1-bit data may be determined to be 0.

  As in the case of the setting value M = 2, in the case of mirror subcarrier communication with the setting value M = 4, 8 symbols are captured and stored in the temporary storage unit 108, and the calculation unit 109 stores the I data and Q data. Are used in the order in which the 8 symbol data of each of the I data and the Q data are taken in, in the order of I1, I2, I3, I4, I5, I6, I7, I8, Q1, Q2, Q3, Q4, Q5 , Q6, Q7, Q8, correlation calculation (I1-I2 + I3-I4) (I5-I6 + I7-I8) + (Q1-Q2 + Q3-Q4) (Q5-Q6 + Q7-Q8) is performed, and the MSB of the calculation result is 1 If the MSB is 0, the 1-bit data is determined to be 0.

  In the case of mirror subcarrier communication with a set value M = 8, after 16 symbols are captured and stored in the temporary storage unit 108, the arithmetic unit 109 uses 16 symbol data of each of I data and Q data. , I data and Q data in the order of 16 symbol data, I1, I2, I3, I4, I5, I6, I7, I8, I9, I10, I11, I12, I13, I14, I15, I16, Q1 , Q2, Q3, Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12, Q13, Q14, Q15, Q16, correlation calculation (I1-I2 + I3-I4 + I5-I6 + I7-I8) (I9-I10 + I11 -I12 + I13-I14 + I15-I16) + (Q1-Q2 + Q3-Q4 + Q5-Q6 + Q7-Q8) (Q9-Q1 + Q11-Q12 + Q13-Q14 + Q15-Q16) performed to determine if the MSB of the operation result is 1 determines data of one bit 1, a 0 data of 1 bit when the MSB is 0.

Since the number of symbol data used for demodulating 1-bit data increases as the value of M increases, the possibility of demodulation even if erroneous data is acquired due to the influence of noise or interference increases. When the final received data is demodulated, the receiving operation is terminated (step 110). In the correlation calculation formulas In and Qn (n = 1 to 16), I and Q, where n is an odd number, and n is an even number, may be interchanged.

(Embodiment 2)
FIG. 4 is a configuration diagram of an RFID demodulating circuit according to the second embodiment of the present invention. Similar to the first embodiment, a receiving apparatus that receives and demodulates mirror subcarrier code data from a tag as a communication partner. This shows an RFID demodulation circuit.

  In FIG. 4, reference numeral 201 denotes an antenna that receives an RFID radio signal in the UHF band. Reference numeral 202 denotes an RF receiving unit that converts received RF signals into analog electrical signals of I and Q signals, and includes an orthogonal modulator, an analog filter, and the like. Reference numeral 203 denotes an AD conversion unit that converts an analog signal of an I signal and a Q signal into a digital signal.

  Reference numeral 204 denotes an IQ signal selection unit that selects a signal to be used for demodulation from among digital I and Q signals. Reference numeral 205 denotes a peak detection unit that detects the peak value of the I signal or Q signal obtained by the IQ signal selection unit 204. Reference numeral 206 denotes a peak interval detection unit that detects the peak interval of the I signal or the Q signal detected by the peak detection unit 205 and generates timing for capturing received data. Reference numeral 207 denotes a counter unit that counts the number of acquired symbol data.

  208 is a temporary storage unit that latches and temporarily stores the I data and Q data at the timing obtained by the peak interval detection unit 206, and 209 is the acquired I and Q based on the set value M of the mirror subcarrier. It is a calculation part which performs the correlation calculation of data. A data determination unit 210 determines 0 or 1 data from the correlation calculation result of a plurality of symbol data in the calculation unit 209. A shift register unit 211 sequentially stores the 1-bit data determined by the data determination unit 210.

  The operation of the RFID demodulator configured as described above will be described below.

  FIG. 5 is an operation flowchart of the RFID demodulation circuit according to the second embodiment of the present invention.

  In FIG. 5, first, when reception is enabled after transmitting a command to the tag (step 201), the RF signal received by the antenna 201 is converted into an analog electric signal by the RF receiver 202 (step 202), and AD conversion is performed. The unit 203 converts the analog electrical signal into a digital signal (step 203).

When I data and Q data obtained by sampling the I data and Q data converted into digital signals at the same timing are respectively In and Qn, the IQ signal selection unit 204 selects either I signal data or Q signal data (step 204) The peak detector 205 searches for the peak of the selected I signal or Q signal.

  The IQ signal selection unit 204 first arbitrarily selects either the I signal or the Q signal, and replaces the signal to be selected every arbitrary number of receptions. The selection signal may be replaced every arbitrary time, or errors during demodulation may be counted and replaced according to the number of errors. In addition, as a method for determining a signal to be selected by the IQ signal selection unit 204, the amplitude of the I signal and the Q signal may be compared to select a higher level. In this case, the signal used for demodulation is selected by comparing the amplitudes of the I signal and the Q signal for each frame (see FIG. 6A) or for each transmission of the Query command (see FIG. 6B). As another method, the noise level of the I signal and the Q signal may be compared to select the one with less noise. In this case, the noise level detection and comparison may be performed every arbitrary number of receptions or every arbitrary time.

  In the peak detection by the peak detection unit 205, at least two pieces of sampling data are always temporarily stored, and a peak is recognized when a change in the value of two consecutive sampling data changes from an increase to a decrease. Or, when three or more sampling data are temporarily stored and the value of any number of consecutive three or more sampling data increases, then it is detected that the sampling data of three or more consecutive points has decreased. By recognizing, erroneous detection of peaks due to pulse noise or the like can be reduced.

  When a peak is detected by the peak detection unit 205, the interval until the next peak is always counted at the sampling frequency, and if it is detected that an arbitrary number of continuous peak intervals are within an arbitrary difference, the average of those intervals The value T is set as the timing interval for fetching data.

For example, as shown in FIG. 3B, when intervals of four consecutive peaks (count numbers at the sampling frequency) are T1, T2, and T3, respectively, and the allowable difference between the intervals is 2 sampling counts, the intervals are Differences T1-T2, T2-T3, T1-T3 are | T1-T2 | ≦ 2 & | T2-T3 | ≦ 2 & | T1-T3 | ≦ 2
Then, the peak interval T is set as the average T = (T1 + T2 + T3) / 3.

  When the peak interval T is set, peaks within an arbitrary count before and after are detected in consideration of the waveform tolerance based on the peak interval T. For example, if an arbitrary count number is 3, the peak detection method searches for a peak by the above-described peak detection method while the counter of the peak interval detection unit is T-3 or more and T + 3 (the actual value is 3 because the counter is reset at T). If no peak is detected by the count T, the I or Q data selected by the IQ signal selection unit 204 is temporarily captured and stored at the count T, and no peak can be detected by the count T + 3. Then, the value is converted into one symbol data.

  If the peak can be detected by the count T + 3 (step 205), the I data or Q data selected at the detection timing is taken in and stored as one symbol data in the temporary storage unit 208 (step 206). The counter of the peak interval detection unit 206 is reset when the count is T or when a peak is detected.

  The number of data acquisition is counted by the counter unit 207, and in the case of mirror subcarrier communication with the setting value M = 2, after four symbols are acquired and stored in the temporary storage unit 208 (step 207), the calculation unit 209 When the I signal is selected by the IQ signal selection unit 204 using the four symbol data of the I or Q data, the correlation calculation formula (I1-I2 ) (I3-I4) is calculated (step 208). When the MSB of the operation result is 1, the 1-bit data is determined as 1, and when the MSB is 0, the 1-bit data is determined as 0. (Step 209). When the Q signal is selected, the correlation calculation formula is (Q1-Q2) (Q3-Q4).

  In the case of mirror subcarrier communication with a set value M = 4, when 8 symbols are captured and stored in the temporary storage unit 208, the IQ unit 209 uses the 8 symbol data of I data or Q data in the arithmetic unit 209. If the I signal is selected in 204, the correlation calculation formulas (I1-I2 + I3-I4) (I5-I6 + I7-I8) are assumed to be I1, I2, I3, I4, I5, I6, I7, and I8 in the order of taking in the eight symbol data. When the MSB of the calculation result is 1, the 1-bit data is determined to be 1, and when the MSB is 0, the 1-bit data is determined to be 0. When the Q signal is selected, the correlation calculation formula is (Q1-Q2 + Q3-Q4) (Q5-Q6 + Q7-QI8).

  In the case of mirror subcarrier communication with a set value M = 8, after 16 symbols are captured and stored in the temporary storage unit 208, the IQ signal is obtained by the arithmetic unit 209 using 16 symbol data of I data or Q data. When the I signal is selected by the selection unit 204, I1, I2, I3, I4, I5, I6, I7, I8, I9, I10, I11, I12, I13, I14, I15, Assuming that I16, the correlation calculation formula (I1-I2 + I3-I4 + I5-I6 + I7-I8) (I9-I10 + I11-I12 + I13-I14 + I15-I16) is calculated. If the MSB is 0, the 1-bit data is determined to be 0. When the Q signal is selected, the correlation calculation formula is (Q1-Q2 + Q3-Q4 + Q5-Q6 + Q7-Q8) (Q9-Q10 + Q11-Q12 + Q13-Q14 + Q15-Q16).

  When the final received data is demodulated, the receiving operation is terminated (step 210).

  As described above, according to each of the above embodiments, a mirror subcarrier demodulation circuit that receives and demodulates mirror subcarrier data, and a waveform generation unit that generates a combined waveform of the received I signal and Q signal; A peak detection unit that detects a peak value of the composite waveform obtained by the waveform generation unit, a peak interval detection unit that detects a peak value interval detected by the peak detection unit and generates a timing for capturing received data, and a peak A storage unit that stores I data and Q data at the timing generated by the interval detection unit, and a correlation using the I data and Q data of the storage unit acquired during one bit period based on the mirror subcarrier setting value M Since it has a configuration including a correlation calculation unit that performs calculation and a data determination unit that determines 0 or 1 data from the calculation result in the correlation calculation unit, the peak data to be acquired Since it can be demodulated if it can only be acquired reliably, it can reduce the effects of noise that occurs outside the symbol data acquisition timing, and more reliably receive data from tags, etc. even under noise or interference from other devices. A demodulating circuit of a mirror subcarrier that can be demodulated can be realized.

  Further, when the set value M = 2, the correlation calculation unit performs the correlation calculation by (I1−I2) (I3−I4) + (Q1−Q2) (Q3−Q4).

  Further, when the set value M = 4, the correlation calculation unit performs the correlation calculation by (I1−I2 + I3−I4) (I5−I6 + I7−I8) + (Q1−Q2 + Q3−Q4) (Q5−Q6 + Q7−Q8).

  Further, when the set value M = 8, the correlation calculation unit (I1-I2 + I3-I4 + I5-I6 + I7-I8) (I9-I10 + I11-I12 + I13-I14 + I15-I16) + (Q1-Q2 + Q3-Q4 + Q5-Q6 + Q7-Q8) ( Q9−Q10 + Q11−Q12 + Q13−Q14 + Q15−Q16), and the correlation calculation is performed.

  The data determination unit determines the most significant bit of the correlation calculation unit as demodulated data having a 1-bit period.

  The peak detector detects the peak of the composite signal in the burst signal part of the first half of the preamble, measures the interval between a plurality of continuous peaks with a counter of an arbitrary period, and calculates the average time (count number). Once the symbol acquisition period is set, the next peak is detected within an arbitrary time before and after the detected peak, so that the peak interval due to fluctuations in the received waveform is corrected, and the IQ due to noise and interference The effect of reducing false detection of the peak of the composite waveform can be obtained.

  Further, since the peak detection unit sets the peak of the waveform when the change in the two consecutive sampling data decreases from the increase, the peak of the IQ composite waveform can be detected with a simple circuit configuration.

  In addition, since the peak detection unit sets the peak of the waveform when three or more consecutive sampling data continuously increase and then three or more consecutive sampling data continuously decrease, a narrow pulse The peak of the composite waveform can be detected so that noise is not erroneously detected.

  In addition, in communication in which a pilot tone is added to the response from the communication partner, the peak detection unit performs peak detection of the composite signal with the pilot tone, measures an interval between a plurality of continuous peaks with a counter of an arbitrary period, Once the average time (count) is set as the symbol latch period, the next peak is detected within an arbitrary time before and after the detected peak, so the peak interval due to fluctuations in the received waveform An effect of correcting and an effect of reducing erroneous detection of the peak of the IQ composite waveform due to noise and interference can be obtained.

  Further, since the peak detection unit detects only the peak of the I and Q signals having a level larger than an arbitrary threshold, it does not erroneously detect noise having a level lower than the threshold.

  The peak detection unit sets a level higher than the noise level as a threshold based on the noise level detected before receiving a signal from the communication partner.

The combined signal generated by the waveform generator is any one of In ² + Qn ² , | In | + | Qn |, | In + In + 1 | + | Qn + Qn + 1 |. If In ² + Qn ² , the combined waveform is a tag Since a waveform with no amplitude fluctuation due to movement of the signal can be obtained, the signal can be detected more accurately, and 1-bit data is demodulated with a plurality of symbol data acquired at the peak timing of the synthesized waveform, so noise and interference can be obtained. Even if there is incorrect data due to the influence of the above, it is possible to interpolate with other symbol data. If | In | + | Qn |, a combined waveform can be generated with a simpler circuit configuration. Furthermore, if | In + In + 1 | + | Qn + Qn + 1 |, a combined waveform in which noise added to the signal is reduced can be obtained.

  A mirror subcarrier demodulating circuit that receives and demodulates mirror subcarrier data, a selection unit that selects one of the received I signal and Q signal, and I data or Q data selected by the selection unit A peak detector that detects a peak value of a signal waveform, a peak interval detector that detects a peak value interval detected by the peak detector, and generates a timing for capturing received data, and a timing generated by the peak interval detector The storage unit that stores the I data or Q data selected by the selection unit, and the correlation using the I data or Q data of the storage unit acquired during one bit period based on the mirror subcarrier setting value M Since it has a correlation calculation unit that performs calculation and a data determination unit that determines 0 or 1 data from the calculation result in the correlation calculation unit, a simpler circuit (less Can be configured in gate scale) it has, not affected by the phase shift of the I and Q data.

  Further, when the set value M = 2, the correlation calculation unit performs the correlation calculation using (I1-I2) (I3-I4) or (Q1-Q2) (Q3-Q4).

  Further, when the set value M = 4, the correlation calculation unit performs correlation calculation using (I1-I2 + I3-I4) (I5-I6 + I7-I8) or (Q1-Q2 + Q3-Q4) (Q5-Q6 + Q7-QI8).

  Further, when the set value M = 8, the correlation calculation unit (I1-I2 + I3-I4 + I5-I6 + I7-I8) (I9-I10 + I11-I12 + I13-I14 + I15-I16) or (Q1-Q2 + Q3-Q4 + Q5-Q6 + Q7-Q8) ( Q9-Q10 + Q11-Q12 + Q13-Q14 + Q15-Q16) is used for correlation calculation.

  The data determination unit uses the most significant bit of the correlation calculation unit as demodulated data having a 1-bit period.

  In addition, since the selection unit switches between the selection of the I signal and the Q signal every arbitrary time, the reception data from more tags can be demodulated more reliably than when demodulating with only the I signal or only the Q signal.

  In addition, since the selection unit switches the selection of the I signal and the Q signal every time according to an arbitrary number of errors, the received data from more tags can be more reliably received than when demodulating with only the I signal or only the Q signal. Can be demodulated.

  In addition, since the selection unit switches the selection of the I signal and the Q signal based on the amplitude level in the burst portion or pilot tone portion of the preamble, more tag data can be obtained by demodulating using a signal having a large amplitude level. Can be demodulated.

  Further, since the amplitude levels of the I signal and the Q signal are detected for each frame, more tags are detected by detecting the amplitude levels of the I signal and the Q signal for each frame and demodulating them using a signal having a large amplitude level. Can be demodulated.

  In addition, since the amplitude levels of the I signal and the Q signal are detected every time the Query command is transmitted, more tag data can be demodulated.

  In addition, since the selection unit selects the lower noise level based on the noise level of the I signal and the Q signal detected before receiving the signal from the communication partner, the signal is demodulated using a signal having a lower noise level. , Reducing false detection due to noise and demodulating more tag data.

Further, the noise level of the I signal and the Q signal is detected every arbitrary number of query command transmissions.

  Further, the noise levels of the I signal and the Q signal are detected every arbitrary time.

  The mirror subcarrier demodulation circuit according to the present invention and the reception device including the same are useful for the demodulation circuit of the reception device used for RFID communication or the like.

Configuration diagram of an RFID demodulation circuit according to Embodiment 1 of the present invention Operational Flowchart of RFID Demodulator Circuit in Embodiment 1 of the Present Invention The figure which shows the waveform of the reception data in Embodiment 1 of this invention Configuration diagram of an RFID demodulating circuit in Embodiment 2 of the present invention Flowchart of operation of RFID demodulation circuit in Embodiment 2 of the present invention The figure which shows the detection period of the signal level in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Antenna 102 RF receiving part 103 AD conversion part 104 Waveform generation part 105 Peak detection part 106 Peak space | interval detection part 107 Counter part 108 Temporary storage part 109 Operation part 110 Data determination part 111 Shift register part

Claims (26)

A mirror subcarrier demodulation circuit that receives and demodulates mirror subcarrier data,
A waveform generator for generating a combined waveform of the received I signal and Q signal;
A peak detector for detecting a peak value of the composite waveform obtained by the waveform generator;
A peak interval detection unit that detects a peak value interval detected by the peak detection unit and generates a timing for capturing received data; and
A storage unit for storing I data and Q data at the timing generated by the peak interval detection unit;
A correlation calculation unit that performs a correlation calculation using I data and Q data of the storage unit acquired during a 1-bit period based on a set value M of a mirror subcarrier;
A mirror subcarrier demodulating circuit comprising: a data determination unit that determines 0 or 1 data from a calculation result in the correlation calculation unit. 2. The correlation calculation unit according to claim 1, wherein when the set value M = 2, the correlation calculation unit performs the correlation calculation by (I1−I2) (I3−I4) + (Q1−Q2) (Q3−Q4). Mirror subcarrier demodulation circuit. When the set value M = 4, the correlation calculation unit performs the correlation calculation using (I1-I2 + I3-I4) (I5-I6 + I7-I8) + (Q1-Q2 + Q3-Q4) (Q5-Q6 + Q7-Q8). 2. The mirror subcarrier demodulation circuit according to claim 1, wherein: When the set value M = 8, the correlation calculator (I1-I2 + I3-I4 + I5-I6 + I7-I8) (I9-I10 + I11-I12 + I13-I14 + I15-I16) + (Q1-Q2 + Q3-Q4 + Q5-Q6 + Q7-Q8) (Q9 2. The mirror subcarrier demodulation circuit according to claim 1, wherein the correlation operation is performed by -Q10 + Q11-Q12 + Q13-Q14 + Q15-Q16). 5. The mirror subcarrier demodulation circuit according to claim 1, wherein the data determination unit uses the most significant bit of the correlation calculation unit as demodulated data having a 1-bit period. 6. The peak detector detects the peak of the composite signal in the burst signal part of the first half of the preamble, measures the interval between a plurality of continuous peaks with a counter of an arbitrary period, and calculates the average time (count number) as a symbol 5. The mirror sub according to claim 1, wherein when the acquisition cycle is set, the next peak is detected within an arbitrary time before and after the set peak from the detected peak. 6. Carrier demodulation circuit. 7. The mirror subcarrier demodulating circuit according to claim 6, wherein the peak detection unit sets a waveform peak when the change in two consecutive sampling data is decreased from an increase. The peak detection unit sets a peak of a waveform when three or more consecutive sampling data continuously decrease after three or more consecutive sampling data continuously increase. 6. The mirror subcarrier demodulation circuit according to 6. In the communication in which a pilot tone is added to the response from the communication partner, the peak detection unit detects the peak of the composite signal with the pilot tone, measures the interval between a plurality of continuous peaks with a counter of an arbitrary period, 5. When the average time (count number) is set as a symbol latch period, the next peak is detected within an arbitrary time before and after the detected peak based on the set time. The mirror subcarrier demodulation circuit according to any one of the preceding claims. 5. The mirror subcarrier demodulation circuit according to claim 1, wherein the peak detection unit detects only peaks of I and Q signals having a level larger than an arbitrary threshold value. 6. 11. The mirror subcarrier demodulation circuit according to claim 10, wherein the peak detecting unit sets a level higher than the noise level as a threshold based on a noise level detected before receiving a signal from a communication partner. 5. The composite signal generated by the waveform generator is any one of In ² + Qn ² , | In | + | Qn |, | In + In + 1 | + | Qn + Qn + 1 |. A mirror subcarrier demodulation circuit according to item. A mirror subcarrier demodulation circuit that receives and demodulates mirror subcarrier data,
A selector for selecting one of the received I signal and Q signal;
A peak detection unit for detecting a peak value of a signal waveform of the I data or Q data selected by the selection unit;
A peak interval detection unit that detects a peak value interval detected by the peak detection unit and generates a timing for capturing received data; and
A storage unit for storing I data or Q data selected by the selection unit at a timing generated by the peak interval detection unit;
A correlation calculation unit that performs a correlation calculation using the I data or Q data of the storage unit acquired during a 1-bit period based on the set value M of the mirror subcarrier;
A mirror subcarrier demodulating circuit comprising: a data determination unit that determines 0 or 1 data from a calculation result in the correlation calculation unit. 14. The correlation calculation unit according to claim 13, wherein when the set value M = 2, the correlation calculation unit performs the correlation calculation using (I 1 -I 2) (I 3 -I 4) or (Q 1 -Q 2) (Q 3 -Q 4). Mirror subcarrier demodulation circuit. When the set value M = 4, the correlation calculation unit performs the correlation calculation with (I1-I2 + I3-I4) (I5-I6 + I7-I8) or (Q1-Q2 + Q3-Q4) (Q5-Q6 + Q7-QI8). 14. The mirror subcarrier demodulation circuit according to claim 13, When the set value M = 8, the correlation calculation unit (I1-I2 + I3-I4 + I5-I6 + I7-I8) (I9-I10 + I11-I12 + I13-I14 + I15-I16) or (Q1-Q2 + Q3-Q4 + Q5-Q6 + Q7-Q8) (Q9 14. The mirror subcarrier demodulating circuit according to claim 13, wherein the correlation calculation is performed by -Q10 + Q11-Q12 + Q13-Q14 + Q15-Q16). The mirror subcarrier demodulation circuit according to any one of claims 13 to 16, wherein the data determination unit uses the most significant bit of the correlation calculation unit as demodulated data having a 1-bit period. The mirror subcarrier demodulation circuit according to any one of claims 13 to 16, wherein the selection unit switches selection of an I signal and a Q signal every arbitrary time. 17. The mirror subcarrier demodulation circuit according to claim 13, wherein the selection unit switches selection of an I signal and a Q signal every time according to an arbitrary number of errors. The mirror subcarrier demodulation according to any one of claims 13 to 16, wherein the selection unit switches selection of an I signal and a Q signal based on an amplitude level in a burst portion or a pilot tone portion of a preamble. circuit. 21. The mirror subcarrier demodulation circuit according to claim 20, wherein amplitude levels of the I signal and the Q signal are detected for each frame. 21. The mirror subcarrier demodulation circuit according to claim 20, wherein amplitude levels of the I signal and the Q signal are detected every time the Query command is transmitted. 17. The method according to claim 13, wherein the selection unit selects a lower noise level based on a noise level of the I signal and the Q signal detected before receiving a signal from a communication partner. 2. A mirror subcarrier demodulation circuit according to 1. 24. The mirror subcarrier demodulating circuit according to claim 23, wherein the noise level of the I signal and the Q signal is detected every arbitrary number of transmissions of the Query command. 24. The mirror subcarrier demodulation circuit according to claim 23, wherein the noise level of the I signal and the Q signal is detected every arbitrary time. A receiving apparatus comprising a mirror subcarrier demodulation circuit, comprising the mirror subcarrier demodulation circuit according to any one of claims 1 to 25.

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