JP5023857B2 - Wireless communication device - Google Patents

Description

  The present invention is a wireless communication apparatus that transmits a transmission signal to a communication target such as a wireless tag, receives a response signal, and decodes the response signal, and can improve a bit error rate (BER) and an S / N ratio. The present invention relates to a wireless communication apparatus that can reliably acquire information without interference from radio waves to be communicated such as a wireless tag even in an environment where (Signal to Noise Ratio) is not good.

  In recent years, in place of barcodes, non-contact wireless tags such as RFID (Radio Frequency Identity) tags have been spotlighted. And it is expected that the RFID tag and the like will be affixed to and distributed in every article in the future. For this reason, wireless communication devices such as reader / writer devices that communicate with RFID tags in a non-contact manner have become widespread.

  As a communication method between the RFID tag and the wireless communication device, there are roughly the following communication methods. The first type is a communication system using electromagnetic induction. There are also two types of electromagnetic induction methods. The frequency used is 400 kHz to 530 kHz, the degree of electromagnetic coupling is high, and communication is performed mainly by mutual induction / electromagnetic induction between the RFID tag coil and the reader coil. Alternatively, there are those that use electromagnetic waves of 13.56 MHz, have a relatively low degree of electromagnetic coupling, and communicate using an induced voltage between both coils.

  On the other hand, there is a radio wave system as a second type. A microwave radiated from an antenna of a wireless communication apparatus is received by a plane wave antenna of an RFID tag, and data is transmitted using the reflected wave. There are also two types of microwave systems: a system that communicates using 2.45 GHz microwaves and a system that communicates using radio waves in the UHF (860 MHz to 960 MHz) band. The former communication distance is about 1 m at the maximum, but the latter communication distance is relatively long and about 8 m at the maximum.

  When communicating by the second type of radio wave system, the wireless communication apparatus performs automatic gain control based on RSSI (Received Signal Strength Indication) indicating the received electric field strength. However, the radio wave transmitted from the wireless communication device to the wireless tag and the reach of the radio wave transmitted from the wireless tag receiving this radio wave depend on the environment to which the wireless tag is applied and are used by the wireless communication device. It is not always appropriate for each individual site. For this reason, when trying to read the information stored in the wireless tag from one of a plurality of wireless tags arranged close to each other, the wireless tag that is not the readout target of the wireless communication device The response radio wave transmitted may be picked up, and the BER deteriorates, causing the system to malfunction. Such a problem is particularly serious in a wireless communication apparatus using a wide frequency band such as the UHF band. In GSM (Global System for Mobile Communications) or the like, there is a similar situation just by changing the communication target.

  Therefore, conventionally, the reception signal and the oscillation signal of the local oscillator are input from the first DBM (Double Balanced Mixer) of the quadrature detection circuit to output the I (In-phase) signal, and the reception signal is output to the second DBM. A signal with the phase of the oscillation signal of the local oscillator shifted by 90 degrees (π / 2) is input to output a Q (Quadrature-phase) signal. This I signal passes through the first filter, Is amplified by the amplifier circuit and input to the demodulation circuit, and the Q signal is generated by the demodulation circuit in the wireless communication device that passes through the second filter and then is amplified by the second amplifier circuit and input to the demodulation circuit. When the demodulated data to be output is output to the baseband processing circuit, a part of the I signal that passes through the first filter and is amplified by the first amplifier circuit and the second filter pass through. A signal obtained by combining a part of the Q signal amplified in the amplifier circuit 2 is input to the RSSI circuit, and a voltage corresponding to the combined signal is output from the RSSI circuit to the baseband processing circuit (for example, , See Patent Document 1).

  The sum of the I signal and Q signal that have passed through the LPF (Low Pass Filter), which is the first and second filters, is input to the RSSI circuit, and this output signal is output to the baseband processing circuit. The RSSI circuit of this (Patent Document 1) is amplified stepwise by a plurality of limiter saturation amplifiers, and synthesizes and outputs output voltages from each detector provided in each limiter saturation amplifier. The relationship between the combined signal obtained by summing the I signal and the Q signal and the output voltage is substantially proportional.

  However, in the case where the sum of the I signal and the Q signal is taken, in the environment where the S / N ratio is small, a signal having a large noise among the I signal and the Q signal is also input to the RSSI circuit. Since such noise is also amplified at the same time, a response radio wave transmitted from an RFID tag that is not a read target may be picked up, which may cause a malfunction.

In addition to the combined signal obtained by summing the I signal and the Q signal, the higher signal level of the I signal and the Q signal is simply adopted and input to the RSSI circuit. . However, it is not possible to avoid malfunction in an environment with a small S / N ratio. In addition, the wireless communication apparatus assumes a plurality of modulation schemes, and calculates the magnitude of a signal when quadrature demodulation is performed as a combined signal, and calculates (I ² + Q ² ) ^1/2 An AGC adjustment is also performed by selecting a scaling coefficient in accordance with a modulation method, turning on and off an LNA (Low Nice Amplifier) control signal and a VGA (Variable Gain Amplifier) control signal (see, for example, Patent Document 2).
JP 2006-120090 A JP 2006-109200 A

  As described above, the wireless communication apparatus performs automatic gain control based on RSSI. However, the reach of radio waves transmitted from a wireless communication device to a radio tag and radio waves transmitted from a radio tag that has received this radio wave depends on the environment to which the radio tag is applied and is placed close to each other. When trying to read information from one of a plurality of wireless tags, the response radio waves transmitted from wireless tags that are not read by the wireless communication device are picked up, causing the system to malfunction It was. This becomes a problem in a wireless communication apparatus using a wide frequency band such as the UHF band.

  For this reason, in the wireless communication device of (Patent Document 1), the sum of the I signal and the Q signal is input to the RSSI circuit, and this output signal is output to the baseband processing circuit. However, in the composite signal obtained by summing the I signal and the Q signal, the signal having the larger noise is amplified and input to the RSSI circuit in an environment with a small S / N ratio, which may cause interference. .

Similarly, a method in which a signal having higher reliability of the signal level of the I signal and the Q signal is adopted and processed by the baseband processing circuit, or a synthesized signal (I ² ) as in (Patent Document 2). A method of adjusting AGC after scaling processing by calculating + Q ² ) ^1/2 is also known, but none of them is a solution that fundamentally solves interference from the wireless tag.

  Certainly, the sum of the I signal and the Q signal is taken as a composite signal, the signal with less noise is adopted, or the magnitude of the signal at the time of quadrature demodulation is calculated to be the composite signal. The negative effect is to reduce the influence of noise. However, if we can change the idea here and further emphasize the more reliable I and Q signals and reduce the unreliable level, we can improve the BER, Even if there is another wireless tag, interference can be avoided.

  Accordingly, the present invention has been made in view of such circumstances, and a wireless communication apparatus that can reliably acquire information from radio waves to be communicated even in an environment where the S / N ratio is not good and can improve the bit error rate. The purpose is to provide.

Wireless communication device of the present invention in order to solve such a problem, a receiving unit that receives a response signal from the communication target, demodulated to two demodulation signals quadrature demodulating the response signal from the receiver parts and a control unit for determining a control amount of the gain with respect to the demodulated signal, row cormorants automatic gain control gain adjusted in accordance with the control amount received from the controller before SL receives two demodulated signals from the demodulator , An AD converter that converts the two demodulated signals from the automatic gain control unit into a digital signal, and the noise level of the two demodulated signals digitized from the AD converter is reduced and the signal level is enhanced a weighting processing a signal demodulation section for outputting rows Utotomoni the weighted result to the control unit, the control unit before further accordance with the weighted results from the signal demodulation unit And key features to determine the control amount.

  According to the wireless communication apparatus of the present invention, it is possible to reliably acquire information from radio waves to be communicated even in an environment where the S / N ratio is not good, improve the bit error rate, and have a communication object at a close position. Even in such a case, radio wave interference can be avoided.

  In order to solve the above-mentioned problem, a first invention of the present invention is a wireless communication apparatus that transmits a transmission signal to a communication target, receives a response signal from the communication target, and decodes the received response signal. A transmitter that transmits a predetermined transmission signal to a target, a receiver that receives a response signal from a communication target, and a quadrature demodulated by a carrier wave that is 90 degrees out of phase with the response signal received by the receiver. An orthogonal demodulator, an automatic gain controller that performs gain adjustment on two response signals of the baseband that are orthogonally demodulated by the orthogonal demodulator, and a reception state that detects a signal level and a noise level when the response signal is received A detection unit, a combined signal generation unit that generates a combined signal by performing weighting processing that enhances the signal level of each signal and reduces the noise level with respect to two response signals that are out of phase; It is a wireless communication device, characterized in that the decryption unit to decrypt the weighting process synthesis signal and a signal decoding unit which is provided by the Patent generator. With this configuration, even in an environment where the S / N ratio is not good, it is possible to reliably acquire information from the radio waves to be communicated, improve the bit error rate, and the radio waves can be transmitted even when there is a communication target at a close position. Interference can be avoided.

  According to a second aspect of the present invention, there is provided a wireless communication apparatus according to the first aspect, wherein a communication target is a wireless tag. With this configuration, radio waves from two adjacent wireless tags do not interfere with each other.

  A third invention of the present invention is an invention subordinate to the first or second invention, wherein the synthesized signal generator weights each of the two baseband response signals orthogonally demodulated as a weighting process with an increasing function. Then, the wireless communication apparatus is characterized in that the sum is taken as a composite signal. With this configuration, by performing weighting processing, the signal level is greatly emphasized, and the noise level is greatly reduced.

  A fourth invention of the present invention is an invention subordinate to the third invention, wherein when one signal is significantly larger than the other signal of two orthogonally demodulated baseband response signals, the combined signal The generation unit weights only one signal as a weighting process. With this configuration, weighting can be performed simply by determining the levels of the two response signals.

  A fifth invention of the present invention is an invention dependent on any one of the second to fourth inventions, wherein the reception state detecting unit sets the noise level in the response response waiting period of the response signal as a noise level by the synthesized signal. The wireless communication apparatus is characterized in that the signal level of the preamble of the response signal is detected as the signal level. With this configuration, by using the noise level and the preamble signal level during the power supply response waiting period until the response signal from the wireless tag is detected, the wireless communication is ensured for each tag response even in an environment where the S / N ratio is poor. Information can be acquired from the radio wave of the tag.

  A sixth invention of the present invention is an invention dependent on any one of the first to fifth inventions, wherein the synthesized signal generation unit obtains the S / N ratio from the signal level and the noise level, and is orthogonal as a weighting process. A radio communication apparatus characterized in that each of two demodulated baseband response signals is weighted according to the S / N ratio. With this configuration, weighting according to the S / N ratio is performed, so that the signal level is easily greatly emphasized and the noise level is greatly reduced.

  A seventh invention of the present invention is an invention dependent on the first or second invention, characterized in that the increasing function is a power or a product of a power and a weighting factor proportional to the S / N ratio. A wireless communication device. With this configuration, the signal level is easily greatly enhanced and the noise level is greatly reduced by a simple calculation.

  An eighth aspect of the present invention is a wireless communication apparatus that transmits a transmission signal to a communication target, receives a response signal from the communication target, and decodes the received response signal, and sends a predetermined transmission signal to the communication target. A transmitting unit for transmitting, a receiving unit for receiving a response signal from a communication target, an orthogonal demodulating unit for inputting two response signals that are received by the receiving unit and outputting two response signals demodulated, and an orthogonal demodulating unit An automatic gain control unit that adjusts the gain for two baseband response signals demodulated orthogonally, a reception state detection unit that detects a noise level at the time of reception of the response signal, and noise detected by the reception state detection unit A control unit that determines a control amount in the automatic gain control unit according to a level, and a signal decoding unit that can decode a combined signal obtained by combining two response signals of orthogonally demodulated baseband; It is a wireless communication device characterized by comprising a. With this configuration, even in an environment where the S / N ratio is not good, it is possible to reliably acquire information from radio waves to be communicated, improve the bit error rate, and radio waves can be transmitted even when there is a communication object at a close position. Interference can be avoided.

  A ninth aspect of the present invention is an invention according to the eighth aspect, wherein the reception state detecting unit detects a noise level during a power supply response waiting period for the response signal, and the control unit performs noise according to the noise level. The wireless communication apparatus is characterized in that a control amount is determined by determining a level determination threshold and switching the noise level determination threshold. With this configuration, the noise level determination threshold value is determined based on the noise level in the power supply response waiting period, and the control amount in the automatic gain control unit is determined according to the noise level based on the determination threshold value, so that the S / N ratio is not good. In this case, it is possible to reliably acquire information from radio waves to be communicated, and to improve the bit error rate.

  A tenth aspect of the present invention is a wireless communication apparatus that transmits a transmission signal to a communication target, receives a response signal from the communication target, and decodes the received response signal, and sends a predetermined transmission signal to the communication target. A transmitting unit for transmitting, a receiving unit for receiving a response signal from a communication target, an orthogonal demodulating unit for inputting two response signals that are received by the receiving unit and outputting two response signals demodulated, and an orthogonal demodulating unit An automatic gain control unit that adjusts the gain for two baseband response signals demodulated orthogonally, a reception state detection unit that detects a noise level at the time of reception of the response signal, and noise detected by the reception state detection unit Control unit that determines the control amount of the attenuator of the receiving unit according to the level, and signal decoding that can decipher a synthesized signal obtained by synthesizing two orthogonally demodulated baseband response signals When a wireless communication device characterized by comprising a. With this configuration, even in an environment where the S / N ratio is not good, it is possible to reliably acquire information from radio waves to be communicated, improve the bit error rate, and radio waves can be transmitted even when there is a communication object at a close position. Interference can be avoided.

(Embodiment 1)
A radio communication apparatus according to Embodiment 1 of the present invention will be described. The wireless communication apparatus according to Embodiment 1 is a reader / writer apparatus that communicates with a communication target such as an RFID tag by radio waves, and is a wireless apparatus that includes a duplexer. FIG. 1 is an overall configuration diagram of a radio communication apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a detailed configuration diagram of a main part of the radio communication apparatus according to Embodiment 1 of the present invention.

  First, the structure of the main part which comprises the radio | wireless communication apparatus of Embodiment 1 is demonstrated based on FIG. In FIG. 1, reference numeral 1 denotes a transmission signal generation unit that generates a baseband signal such as a read request toward a wireless tag such as an RFID tag (a communication target of the present invention). 2 is a modulation unit (orthogonal modulation unit) that orthogonally modulates the baseband signal generated by the transmission signal generation unit 1 using an ASK (Amplitude shift keying) method or the like, and 3 is a predetermined frequency (860 MHz˜ This is a carrier generation unit that generates a local oscillation signal (carrier wave) of 960 MHz UHF band), for example, 900 MHz. This is composed of a local oscillator circuit (Local Oscillator) or the like. Furthermore, 4 is a variable power amplifier (Power Amplifier) that amplifies a transmission signal in which the local oscillation signal and the baseband signal are modulated by the ASK method. A transmission system circuit for transmitting transmission signals such as the transmission signal generation unit 1, the modulation unit 2, the carrier wave generation unit 3, and the power amplifier 4 is a transmission unit in the present invention.

  Reference numeral 5 denotes a transmission / reception sharing unit that transmits a transmission signal only to the antenna side and transmits a reception signal only to a reception system circuit. Reference numeral 6 denotes an antenna switching unit that selects one of a plurality of antennas by input from a sensor or the like. , 7 are antennas for wireless communication with a wireless tag at a frequency in the UHF band. Therefore, the antenna 7 of Embodiment 1 is a planar antenna. The transmission signal from the transmission system circuit is output to the antenna 7 side, but does not wrap around the reception system circuit described later from the transmission / reception shared unit 5, and conversely, the reception signal received by the antenna 7 is transmitted / received. Does not sneak into the transmission system circuit.

  The transmission system circuit of the wireless communication apparatus that transmits a transmission signal from the antenna 7 has been described above. Next, the reception system circuit will be described. In FIG. 1, 8 is a low noise amplifying unit that receives a reflected wave as a response from the wireless tag and amplifies the received signal with low noise, and 9 is a phase of 90 degrees of the outputs that are low noise amplified by the low noise amplifying unit 8. This is a demodulator (orthogonal demodulator of the present invention) that performs quadrature demodulation using the shifted carrier waves. In the demodulator 9, the local oscillation signal of the carrier wave generator 3 is input with the same phase as the received signal and with the phase shifted by 90 degrees (π / 2) at the same time, and mixed with the received signal from the antenna 7 to be orthogonal. Demodulated.

  Therefore, the demodulator 9 outputs two signals of the baseband orthogonal to the I (In-phase) signal having the same phase as the received signal and the Q (Quadrature-phase) signal by the carrier wave delayed by 90 degrees from this. . An automatic gain control unit 10 is a VGA (Variable Gain Amplifier) that amplifies the I signal and the Q signal, and 11 is a Received Signal Strength Indication (RSSI) detection unit. The RSSI detection unit 11 can be used freely by switching a switch 14 to be described later, or can not be used.

  A signal decoder 12 can decode response information returned from a wireless tag as a communication target after converting each of the I and Q signals whose gains have been adjusted by the automatic gain control unit 10 into digital signals. Reference numeral 12a denotes an IQ calculation unit (combined signal generation unit of the present invention) provided in the signal decoding unit 12. When decoding the response information in the signal decoding unit 12, it is necessary to extract the response information from the I signal and the Q signal after reducing the noise level included in the I signal and the Q signal as much as possible. The process of emphasizing the signal level in order to reduce the noise level and actively increase the reliability of the data is the I signal / Q signal weighting process of the present invention, and this process (calculation) is performed by the IQ calculation. Part 12a.

  Reference numeral 12b denotes a reception state detection unit that detects a signal level (S) and a noise level (N) of communication performed between the wireless communication device and a wireless tag (for example, RFID tag) that is a communication target. A weighted signal exceeding a predetermined determination threshold is sampled and averaged (noise level), the signal level is also sampled to obtain an average value, and it is detected whether it falls within the determination threshold. Thereby, the S / N ratio can be calculated. If the S / N ratio is bad, the gain is adjusted and the antenna 7 is switched. As the S / N ratio increases, the BER also improves. Next, 12c is a decoding unit for extracting the baseband signal from the received signal based on the output weighted by the IQ calculation unit 12a and decoding the response information from the wireless tag included in the received signal.

  Subsequently, in FIG. 1, reference numeral 13 denotes a control unit, and reference numeral 14 denotes a switch provided between the RSSI detection unit 11 and the control unit 13. By switching the switch 14, the gain of the I signal and the Q signal can be adjusted by controlling the VGA constituting the automatic gain control unit 10 based on the received electric field strength detected by the RSSI detection unit 11. As in the first to seventh embodiments, the control amount of gain adjustment performed by the automatic gain control unit 10 can be determined based on the weighting of the I signal and the Q signal from the response signal or the noise level detection. .

  FIG. 2 shows the configuration of the wireless communication apparatus described above in more detail. Note that the RSSI configuration is omitted. In FIG. 2, 21 is a DA converter that D / A converts the baseband signal generated by the transmission signal generator 1, 22 is a smooth filter for removing aliasing that occurs during D / A conversion, and 23 is An amplifying unit for amplifying the baseband signal after removing aliasing.

  Next, details of the modulation unit 2 will be described. The modulation unit 2 is an orthogonal modulation unit, 24 is a hybrid circuit that can output the local oscillation signal (carrier wave) of the carrier wave generation unit 3 as two signals having a phase difference of 90 degrees (π / 2), and 25a and 25b are multipliers. It is. Reference numeral 26 denotes a combiner that combines the baseband signal and two signals obtained by mixing the signals having a phase difference of 90 degrees from the hybrid circuit 24 and outputs the combined signal as a transmission signal. Note that the hybrid circuit 24 is not limited to the above-described use, and one of the divided local oscillation signals may be output in the same phase and the other output may be provided with a π / 2 phase shift circuit.

  The output from the modulation unit 2 is amplified by the power amplification unit 4, and after the high frequency component is removed by the filter unit 27 made of LPF (Low Pass Filter), it is transmitted from the antenna unit 7 selected by the antenna switching unit 6. . The switching by the antenna switching unit 6 is performed by selecting the antenna unit 7 that is estimated to be most suitable for transmission / reception from among the antenna units 7 arranged close to each other. This determination is made based on an input from a separately provided sensor or the like.

  Subsequently, a reception system circuit for extracting information on the wireless tag from the reception signal received from the antenna unit 7 will be described. Reference numeral 30 denotes an attenuator for adjusting the signal level of the received signal, and reference numeral 31 denotes a filter unit composed of a BPF (Band Pass Filter) that extracts a predetermined frequency component from the received signal.

  Further, the demodulator 9 will be described in detail. The demodulator 9 is an orthogonal demodulator, and 32 is a distributor. The distributor 32 divides the reception signal amplified by the low noise amplification unit 8 into two equal parts and distributes them to two signals having the same phase. The two signals are mixed with the two signals having a phase difference of 90 degrees (π / 2) by the adjusting unit 9. Reference numeral 33 denotes a hybrid circuit that can output the local oscillation signal (carrier wave) of the carrier wave generation unit 3 as two signals having a phase difference of 90 degrees. Reference numerals 34a and 34b denote the two distributed signals as I signals having the same phase as the reception signal. This is a multiplier for outputting as a Q signal delayed in phase by 90 degrees. The multipliers 34a and 34b are for multiplying two distributed signals by a local oscillation signal having a phase difference of 90 degrees.

  Next, reference numeral 35 denotes an anti-area filter for performing anti-aliasing that removes excess frequency components before A / D conversion. Reference numeral 36 denotes an AD converter that performs A / D conversion on the received signal that was an analog signal. With the above configuration, the received signal received by the antenna unit 7 is quadrature demodulated by the demodulating unit 9 to be an I signal and a Q signal, which are two baseband signals, and the signal decoding unit 12 weights both signals. And decoding is performed based on the weighted I and Q signals. Therefore, although the RSSI detection unit 11 is an analog circuit as in the past, the reception state detection unit 12b of the first embodiment performs weighting by digital processing, and the control unit 13 detects the magnitude of noise according to this output, and automatically The control amount of the gain control unit 10 is determined.

Here, the weighting process of the I signal and the Q signal according to the first embodiment will be described. I signal of the first embodiment, the output V _out that weighting was performed of the Q signal, respectively increasing function of I signal, Q signal, wherein the sum of the exponentiation is determined by the relationship of V _out = I ^m + Q ^m . Here, m ≧ 2. As a result, an output that is relied upon (highlighted) by the more reliable signal of the I signal and the Q signal is obtained. That is, for example, assuming that the I signal and the Q signal are larger and the noise level is relatively low, for example, this is emphasized, and the signal level of the Q signal is lower (the noise level is relatively lower). To be larger). At this time, if (I ^m + Q ^m ) is calculated, (I + Q) or (I ² + Q ² ) ^1/2 is simply calculated as in the past, or the larger I or Q is selected. Thus, a reliable signal is emphasized by a power of m (m ≧ 2), and this weighted V _out can be output. It should be noted that the increase function is not limited to the power.

Therefore, based on the highly reliable V _out , the automatic gain control unit 10 determines the relationship between the level value of (I ^m + Q ^m ) stored in the memory (not shown) by the control unit 13 and the gain of the VGA. A control amount to be instructed is determined, and a control signal is output to the automatic gain control unit 10 to perform AGC adjustment. Actually, if the level value of the I signal and the level value of the Q signal are detected, the level value of (I ^m + Q ^m ) is determined according to the set ^m , and the control amount of the automatic gain control unit 10 is determined. Note that (I ² + Q ² ) ^1/2 may be raised to the power of n, and the output V _{out obtained} by weighting the I signal and the Q signal may be V _out = (I ² + Q ² ) ^{n / 2} . At this time, n> 1. The signal level is weighted more than when n = 1, and the noise level is relatively lowered.

Thus, in the signal decoding unit 12 of the first embodiment, when V _out is calculated from the I signal and the Q signal, V _out = I ^m + Q ^m (where m ≧ 2) or V _out = (I ² + Q ² ) Since the weighting is performed by the increasing function of ^{n / 2} (where n> 1), the noise level is reduced, the BER (Bit Error Rate) is improved, and the reliability of the value of _Vout is increased. Also, based on this V _out , the response radio wave transmitted from the wireless tag that is not the readout target in order to determine the control amount in the automatic gain control unit 10 from the correspondence relationship between the V _out level value and the VGA gain. Therefore, even in an environment with a small S / N ratio, interference of received radio waves can be prevented, antenna switching can be performed in a short time, and information can be reliably acquired from radio waves.

(Embodiment 2)
A radio communication apparatus according to Embodiment 2 of the present invention will be described. The wireless communication apparatus according to the second embodiment is different from the first embodiment in weighting when calculating the output from the I signal and the Q signal. The wireless communication apparatus according to the second embodiment is different from the wireless communication apparatus according to the first embodiment only in the weighting processing contents for the I signal and the Q signal performed by the IQ calculation unit in the signal decoding unit. Are common. Accordingly, FIGS. 1 and 2 are referred to also in the second embodiment, and the same reference numerals indicate the same configurations.

The weighting of the I signal and the Q signal, which is a feature of the wireless communication apparatus in the second embodiment, will be described. The output V _out subjected to the weighting in the first embodiment is determined by the relationship of V _out = I ^m when I >> Q, and V _out = Q ^m when Q >> I. Here, m ≧ 2. The calculation of the power is simple, but it may be weighted by another increase function. As a result, the more reliable signal of the I signal and the Q signal is output with higher emphasis. That is, for example, of the I signal and the Q signal, if the I signal is larger and the noise level is relatively low I >> Q, the Q signal level becomes lower (noise becomes relatively larger). At this time, ignoring Q with a large noise and calculating V _out = I ^m , than simply calculating (I + Q) or (I ² + Q ² ) ^1/2 or selecting I, The reliable I signal is enhanced by a power of m (increasing function) and this weighted _Vout can be output.

Similarly, when the Q signal is larger and the noise level is relatively low Q >> I, the I signal level is lower (noise is relatively larger). At this time, if I which ignores the noisy I and calculates V _out = Q ^m , than simply calculating (I + Q) or (I ² + Q ² ) ^1/2 or selecting Q, A reliable Q signal is emphasized by a power of m (increasing function), and this weighted _Vout can be output.

Accordingly, I»Q the IQ calculation unit 12a, performs case analysis of Q»I, if applicable to any of these conditions, the level value of I ^m or Q ^m the control unit 13 is previously memory and VGA A control amount to the automatic gain control unit 10 is determined from the relationship with the gain, and a control signal is output to the automatic gain control unit 10 to perform AGC adjustment. In the case of m = 2, the level value of the I signal is compared with the level value of the Q signal. When I >> Q, V _out = I ² , and when Q >> I, V _out = Q ² is As a result, the control amount for the automatic gain control unit 10 is determined.

Thus, in the signal decoding unit 12 of the second embodiment, V _out = I ^m is selected when I >> Q, and V _out = Q ^m (where m ≧ 2) is selected when Q >> I. Since the I signal and the Q signal are weighted, the noise level is lowered and the reliability of the value of V _out is increased. This prevents the system from malfunctioning by picking up response radio waves transmitted from wireless tags that are not subject to readout, improves BER even in an environment with a small S / N ratio, and prevents interference of received radio waves. It is possible to reliably acquire information from radio waves.

(Embodiment 3)
A radio communication apparatus according to Embodiment 3 of the present invention will be described. The wireless communication apparatus according to the third embodiment is different from the first embodiment in that a signal having a larger S / N ratio of the I signal and the Q signal is selected. The wireless communication apparatus according to the third embodiment is the same as the wireless communication apparatus according to the first embodiment except for the processing content performed by the IQ calculation unit in the signal decoding unit. Accordingly, FIGS. 1 and 2 are also referred to in the third embodiment, and the same reference numerals indicate the same configuration. FIG. 3 is an explanatory diagram for the signal level detection of the S / N ratio of the wireless communication apparatus according to the third embodiment of the present invention.

  The wireless communication apparatus according to the third embodiment improves the BER by selecting the signal having the larger S / N ratio among the I signal and the Q signal, and increases the reliability of the data of the response signal from the wireless tag. Is. For this reason, as shown in FIG. 3, the transmission data 1 is transmitted from the wireless communication apparatus, and the carrier wave transmission period until the response of the reception data 1 is received from the wireless tag (power supply period for the passive wireless tag having no power supply) And the first preamble of the received data 1 is used.

  That is, in a wireless communication apparatus that obtains a response signal from a wireless tag or the like using a frequency band such as a UHF band, power is supplied to the wireless tag after transmitting a transmission signal to a passive wireless tag or the like. To continue transmitting the carrier wave. The wireless tag returns a response signal by the power supply by the carrier wave and is received by the wireless communication device. As shown in FIG. 3, the format of the response signal of the wireless tag is composed of a leading preamble, subsequent response data to be read, and a final CRC code. The wireless communication apparatus according to the third embodiment uses a response waiting time before receiving a response signal from the wireless tag and a carrier wave transmission period serving as a power supply period (hereinafter referred to as a response waiting time and a period serving as a power supply period). This is referred to as a response waiting period A. The noise level is determined during the power supply response waiting period of the present invention. The signal level is detected by detecting the preamble level of the response signal.

  The reception state detection unit 12b provided in the signal decoding unit 12 illustrated in FIG. 1 detects a noise level in the power supply response waiting period A, and detects a peak value of, for example, 5 to 10 samples from the beginning of the preamble. There may be more. The sampling interval is about 1 μs to 1 ms, the average signal level is obtained by calculating the average of the peak values, and the S / N ratio is calculated. Next, a signal having a larger S / N ratio is selected from the I signal and the Q signal. The average value may be calculated by excluding the peak value having the largest fluctuation amount as an abnormal value.

The output V _out is an increase function of the I signal when S _I / N _I >> S _Q / N _Q , where V _out = I ^m , which is the power of ^m , and S _Q / N _Q >> S _I / N _I In this case, the increase function of the Q signal, here the power V _out = Q ^m is determined. Here, m ≧ 2. It should be noted that the increase function is not limited to the power. As a result, the more reliable signal of the I signal and the Q signal is output with higher emphasis. Therefore, in the IQ calculation unit 12a, the case of S _I / N _I >> S _Q / N _Q and S _Q / N _Q >> S _I / N _I is divided. A control amount to the automatic gain control unit 10 is determined from the relationship between the I ^m or Q ^m level value stored in advance and the gain of the VGA, and a control signal is output to the automatic gain control unit 10 to perform AGC adjustment. . For m = 2, the level value of level values and the Q signal of the I signal is compared, S _I / N _I »S if the _Q / N _Q is ^{_{V out = I 2, S Q}} / N Q »S I In the case of / N _I , V _out = Q ² is selected, and the control amount for the automatic gain control unit 10 is determined.

  In this way, the noise level is detected using the power supply response waiting period A before the preamble, and the signal level is detected by the preamble. Therefore, suitable gain adjustment can be performed in real time even in an environment with a small S / N ratio, and the BER is improved. , Radio information from radio tags can be obtained even if the radio wave environment is bad, so that accurate information can be obtained from the radio tag, and response radio waves transmitted from radio tags that are not to be read are picked up and the system does not malfunction. Information can be acquired reliably.

(Embodiment 4)
A radio communication apparatus according to Embodiment 4 of the present invention will be described. The wireless communication apparatus according to the fourth embodiment is different from the first embodiment in that weighting is further performed with the S / N ratio with respect to the weighting of the I signal and the Q signal. The wireless communication apparatus according to the fourth embodiment is the same as the wireless communication apparatus according to the first embodiment except for the calculation performed by the IQ calculation unit in the signal decoding unit. Accordingly, FIGS. 1 and 2 are referred to also in the fourth embodiment, and the same reference numerals indicate the same configuration.

The wireless communication apparatus according to the fourth embodiment is basically the same as the wireless communication apparatus according to the first embodiment, but further weights the first embodiment by detecting the S / N ratio of the I signal and the Q signal. To do. That is, the increasing function of the I signal and the Q signal is a function obtained by taking the product of the weighting factors “a” and “b”, which are functions of the S / N ratio, to the power of m. The output V _out is output in a relationship of V _out = a · I ^m + b · Q ^m . Here, m ≧ 2, the coefficient a is a weighting coefficient proportional to S _I / N _I , and the coefficient b is a weighting coefficient proportional to S _Q / N _Q.

Noise level in the reception state detecting section provided in the signal decoding unit 12 is powered response wait period A, when detecting the signal level of the preamble, the product of the coefficients a and I ^m of IQ calculating section 12A is previously memory, coefficient takes the sum of the products of b and Q ^m, determines the control amount to the automatic gain control unit 10 from the relationship between the level value and the VGA gain, the output to AGC adjusts the control signal to the automatic gain control unit 10 Do.

The coefficient a single read request with the wireless tag that is a wireless communication device and the target - a marked coefficient weighting factor proportional to the S _I / N _I detected for each response, the coefficient b is also the wireless communication device And a weighting coefficient proportional to S _Q / N _Q detected for each read request-response of the wireless tag. As a result, the more reliable signal of the I signal and the Q signal is emphasized as a power of m and further weighted by the weighting coefficient (increasing function), and the noise is reduced. When m = 2, the output V _out is determined by the relationship of V _out = a · I ² + b · Q ² . In this case as well, an increasing function such as V _out = (a · I ² + b · Q ² ) ^{n / 2} can be used. In this case, n> 1.

As described above, in the signal decoding unit 12 according to the fourth embodiment, if (I ^m + Q ^m ) is calculated mechanically with an increasing function of the power of m for the I signal and the Q signal, (I + Q) or ^Compared to calculating (I ² + Q ² ) ^1/2 or selecting the larger I or Q, the signal with higher reliability is emphasized, and the contribution of noise becomes lower. At the same time, the communication state detection unit 12b detects the actual communication status at that time, and selects the weighting coefficient a proportional to S _I / N _I and the weighting coefficient b proportional to S _Q / N _Q to provide high reliability. If the signal is more emphasized, the BER is further improved, the response radio wave transmitted from the wireless tag not to be read is not picked up, and the system does not malfunction, even in an environment with a small S / N ratio. It is possible to prevent interference of received radio waves and reliably acquire information from the radio waves.

(Embodiment 5)
A radio communication apparatus according to Embodiment 5 of the present invention will be described. Wireless communication apparatus according to the fifth embodiment, the fourth embodiment is a process when a relationship of _{S I / N I »S Q /} N Q, S Q / N Q »S I / N I. The wireless communication apparatus according to the fifth embodiment is the same as the wireless communication apparatus according to the first embodiment except for the calculation performed by the IQ calculation unit in the signal decoding unit. Accordingly, FIGS. 1 and 2 are also referred to in the fifth embodiment, and the same reference numerals indicate the same configurations. FIG. 3 is an explanatory diagram for the signal level detection of the S / N ratio of the wireless communication apparatus according to the third embodiment of the present invention.

That is, in the wireless communication device according to the fifth embodiment, when the communication state detection unit 12b of the wireless communication device detects an actual communication state, the S / N ratio of the I signal and the S / N ratio of the Q signal are predetermined determination threshold values. In the case of S _Q / N _Q <noise level determination threshold, b = 0 and V _out = a · I ^m are output in the fourth embodiment, and S _I / N _I > noise level determination threshold In this case, a = 0 and V _out = b · Q ^m are selected in the fourth embodiment. In addition, when S _I / N _I <noise level determination threshold, a = 0 and V _out = b · Q ^m are output in the fourth embodiment, and when S _Q / N _Q > noise level determination threshold. In the fourth embodiment, b = 0 and V _out = a · I ^m are selected. In the above, m ≧ 2.

For example, when m = 2, when S _Q / N _Q <noise level determination threshold, b = 0 and V _out = a · I ² are output in the fourth embodiment, and S _I / N _I > noise level In the case of the determination threshold value, a = 0 and V _out = b · Q ² are selected in the fourth embodiment. In addition, when S _I / N _I <noise level determination threshold, a = 0 and V _out = b · Q ² are output in the fourth embodiment, and when S _Q / N _Q > noise level determination threshold. In the fourth embodiment, b = 0 and V _out = a · I ² .

As described above, in the signal decoding unit 12 according to the fifth embodiment, the noise level is determined, the communication state detection unit 12b detects the actual communication state at that time, and the weighting coefficient a proportional to S _I / N _I. Since the weighting coefficient b proportional to S _Q / N _Q is selected to emphasize more highly reliable signals, the BER is further improved, and the response radio wave transmitted from the wireless tag that is not the readout target Therefore, even in an environment with a small S / N ratio, it is possible to prevent interference of received radio waves and reliably acquire information from the radio waves.

(Embodiment 6)
A radio communication apparatus according to Embodiment 6 of the present invention will be described. The wireless communication apparatus according to the sixth embodiment determines the noise level of the received signal at the time of reception and switches the reception gain. Accordingly, FIGS. 1 and 2 are referred to also in the sixth embodiment, and the same reference numerals indicate the same configurations. FIG. 4 is an explanatory diagram for the signal level detection of the S / N ratio of the wireless communication apparatus according to the sixth embodiment of the present invention.

  As in the third embodiment, the wireless communication apparatus according to the sixth embodiment has a response signal based on a signal having a larger S / N ratio among the I signal and the Q signal, or a combined signal of the I signal and the Q signal. AGC controlled. For this reason, as shown in FIG. 4, the transmission period 1 from when the transmission data 1 is transmitted from the wireless communication apparatus until the response of the reception data 1 is received from the wireless tag (power supply period for the passive wireless tag having no power source) And the first preamble of the received data 1 is used.

  That is, after transmitting a transmission signal to the wireless tag, the wireless communication apparatus continuously transmits a carrier wave for supplying power to the wireless tag in order to operate the wireless tag. The wireless tag can return a response signal by the power supply by the carrier wave, and the wireless communication device can receive the response signal. As shown in FIG. 4, the format of the response signal from the wireless tag is composed of a leading preamble, subsequent response data, and a final CRC code. The wireless communication apparatus according to the sixth embodiment uses noise level detection by detecting a noise level in a response waiting time before receiving a response signal from a wireless tag and in a carrier wave transmission period (power feeding response waiting period A) of a power feeding period. Perform level judgment.

  The reception state detection unit 12b shown in FIG. 1 detects the noise level of the signal having the larger S / N ratio of the I signal and the Q signal or the combined signal of the I signal and the Q signal during the power supply response waiting period A. . The sampling interval is about 1 μs to 1 ms, and the average noise level is obtained by calculating the average of the peak values. The noise level may be calculated by removing the peak value having the largest fluctuation amount as an abnormal value.

  Therefore, in the sixth embodiment, the control unit 13 switches the gain of the VGA based on the noise level of the power supply response waiting period A to be arranged before the preamble. Alternatively, the control unit 13 controls the attenuation amount of the attenuator 30 based on the detection result. Therefore, a combined signal of the I signal and the Q signal calculated by the IQ calculation unit 12a is detected by determining a noise level by a slice level controller (not shown) of the communication state detection unit 12b, and based on this detection result. Then, the control unit 13 adjusts the gain of the VGA. The combined signal of the I signal and the Q signal is decoded by the decoding unit 12c, and response information from the wireless tag is extracted and passed to the control unit 13.

  In this way, since the VGA gain is switched using the power supply response waiting period A before the preamble, suitable gain adjustment can be performed in real time even in an environment with a small S / N ratio, BER can be improved, and information from the wireless tag can be obtained. Is accurate, and does not cause the system to malfunction by picking up response radio waves transmitted from radio tags that are not subject to readout, and prevents radio wave interference from radio tags even in poor radio wave environments. Information can be acquired reliably.

(Embodiment 7)
A radio communication apparatus according to Embodiment 7 of the present invention will be described. The radio communication apparatus according to the seventh embodiment performs AGC control of the sixth embodiment with higher reliability. Accordingly, FIGS. 1 and 2 are referred to also in the seventh embodiment, and the same reference numerals indicate the same configurations. FIG. 5 (a) is an explanatory diagram of noise level determination when the noise level of the wireless communication apparatus according to Embodiment 7 of the present invention is small, and FIG. 5 (b) is the noise of the wireless communication apparatus according to Embodiment 7 of the present invention. It is explanatory drawing of noise level determination when a level is large.

  Also in the seventh embodiment, the reception state detection unit 12b receives the I signal and Q signal having the larger S / N ratio during the power supply response waiting period A or the I signal calculated by the IQ calculation unit 12a. The noise level of the synthesized signal of the Q signal is detected. Based on the detection result, the control unit 13 adjusts the gain of the VGA. The control unit 13 switches the gain of the VGA based on the noise level in the power supply response waiting period A. The combined signal of the I signal and the Q signal is decoded by the decoding unit 12c, and response information from the wireless tag is extracted and passed to the control unit 13.

  In the communication state detection unit 12b, the slice level controller detects the noise level, and based on this, the control unit 13 adjusts the gain of the VGA. However, in the seventh embodiment, when the noise level is detected, the determination threshold for the noise level is changed between a case where the noise level is low and a case where the noise level is high for each read request-response. That is, it is better that there is a difference in the determination threshold between the noise level determination when the noise level is small and the S / N ratio is large and the noise level determination when the noise level is small and the S / N ratio is small. Therefore, in the seventh embodiment, the determination threshold is changed for each read request-response, and the noise level is detected by the slice level controller. 5A shows a noise level determination when the noise level is low, and FIG. 5B shows a noise level determination when the noise level is high.

  When the noise level is high, a combined signal of the I signal and the Q signal calculated by the IQ calculation unit 12a is input to the communication state detection unit 12b, and the noise level is detected by changing the determination threshold for each read request-response. Based on this, the control unit 13 adjusts the gain of the VGA. When the noise level is low, the gain is decreased, but the same is true.

  In this way, the power supply response waiting period before the preamble is used, and the VGA gain is switched by changing the noise level judgment threshold for each transmission and response, so that suitable gain adjustment can be performed in real time even in an environment with a small S / N ratio. Yes, the BER is improved, the information from the wireless tag is accurate, the response radio wave transmitted from the wireless tag that is not the target of reading is not picked up, and the system does not malfunction, and the radio wave environment is poor. However, radio wave interference from the wireless tag can be prevented and information can be acquired with certainty.

  The present invention can be applied to a wireless communication device such as a reader / writer device that wirelessly communicates with a wireless tag or the like.

1 is an overall configuration diagram of a wireless communication apparatus according to Embodiment 1 of the present invention. FIG. 1 is a detailed configuration diagram of a main part of a wireless communication apparatus according to Embodiment 1 of the present invention. Explanatory drawing for the signal level detection of the S / N ratio of the wireless communication apparatus in the third embodiment of the present invention Explanatory drawing with respect to the signal level detection of the S / N ratio of the radio | wireless communication apparatus in Embodiment 6 of this invention (A) Explanatory drawing of noise level determination when the noise level of the wireless communication apparatus in Embodiment 7 of the present invention is small, (b) Noise when the noise level of the wireless communication apparatus in Embodiment 7 of the present invention is large Illustration of level judgment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission signal generation part 2 Modulation part 3 Carrier wave generation part 4 Power amplifier 5 Transmission / reception sharing part 6 Antenna switching part 7 Antenna 8 Low noise amplification part 9 Demodulation part 10 Automatic gain control part 11 RSSI detection part 12 Signal decoding part 12a IQ calculation part 12b Reception state detection unit 13 Control unit 14 Switch 21 D / A converter 22 Smooth filter 23 Amplification unit 24 Hybrid circuit (0/90)
25a, 25b multiplier 26 coupler 27 filter unit (LPF)
30 Attenuator (ATT)
31 Filter section (BPF)
32 Distributor 33 Hybrid circuit (0/90)
34a, 34b Multiplier 35 Anti-area filter 36 A / D converter

Claims (3)

A receiver for receiving a response signal from the communication target;
A demodulator for the two demodulated signals quadrature demodulating the response signal from the receiving unit,
A control unit for determining a gain control amount for the two demodulated signals;
And row Cormorant automatic gain controller a gain adjusted in accordance with the control amount received from the controller before SL receives two demodulated signals from the demodulator,
An AD converter for converting the two demodulated signals from the automatic gain control unit into digital signals;
The noise level is the signal level reduces the digitized said two demodulated signals from the AD converter and a signal demodulator for outputting a weighting process emphasizing line Utotomoni the weighted result to the control unit,
The wireless communication apparatus, wherein the control unit determines the control amount according to the weighted result from the signal demodulation unit . The wireless communication apparatus according to claim 1, wherein the communication target is a wireless tag. The radio communication apparatus according to claim 1, wherein the signal demodulating unit performs weighting with an increasing function as weighting processing.

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