Quadrature demodulator
First Claim
1. A quadrature demodulator comprising reception means for receiving a signal transmitted by an RFID tag and containing a specific pattern and data following the specific pattern, multiplying the reception signal by a local signal to generate an I-signal, and multiplying the reception signal by the local signal shifted in phase by 90 degrees to generate a Q-signal, first demodulating means, and second demodulating means, the first demodulating means comprising an I-signal squaring section which squares the I-signal, a Q-signal squaring section which squares the Q-signal, an adding section which adds the output from the I-signal squaring section to the output from a Q-signal squaring section, an automatic gain control section which controls gain of the I- and Q-signals on the basis of a value from the adding section, and a data generating section which generates data by inverting a signal level of a signal output by the adding section every time the value of the signal becomes equal to or greater than a predetermined threshold or smaller than a predetermined threshold, the second demodulating means comprising I-signal specific-pattern detecting means for detecting the specific pattern in the I-signal, Q-signal specific-pattern detecting means for detecting the specific pattern in the Q-signal, and decoding means for decoding the data following the specific pattern detected by one of the specific-pattern detecting means, the quadrature demodulator being configured to select one of the first demodulating means and the second demodulating means in accordance with a gain of the automatic gain control section.
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Accused Products
Abstract
A quadrature demodulator includes a reception section which receives a signal transmitted by an RFID tag and containing a specific pattern and data following the specific pattern and multiplies the reception signal by a local signal to generate an I-signal, while multiplying the reception signal by the local signal shifted in phase by 90 degrees to generate a Q-signal, a first demodulating circuit which squares the I- and Q-signals and adding the resulting I- and Q-signals together to generate data on the basis of the addition result, a second demodulating circuit which detects the specific pattern in the I- and Q-signals to decode the data following one of the detected specific patterns, and a control section which selects one of the first and second demodulating circuits in accordance with a gain determined by the result of the addition between the values of the squared I- and Q-signals.
11 Citations
13 Claims
- 1. A quadrature demodulator comprising reception means for receiving a signal transmitted by an RFID tag and containing a specific pattern and data following the specific pattern, multiplying the reception signal by a local signal to generate an I-signal, and multiplying the reception signal by the local signal shifted in phase by 90 degrees to generate a Q-signal, first demodulating means, and second demodulating means, the first demodulating means comprising an I-signal squaring section which squares the I-signal, a Q-signal squaring section which squares the Q-signal, an adding section which adds the output from the I-signal squaring section to the output from a Q-signal squaring section, an automatic gain control section which controls gain of the I- and Q-signals on the basis of a value from the adding section, and a data generating section which generates data by inverting a signal level of a signal output by the adding section every time the value of the signal becomes equal to or greater than a predetermined threshold or smaller than a predetermined threshold, the second demodulating means comprising I-signal specific-pattern detecting means for detecting the specific pattern in the I-signal, Q-signal specific-pattern detecting means for detecting the specific pattern in the Q-signal, and decoding means for decoding the data following the specific pattern detected by one of the specific-pattern detecting means, the quadrature demodulator being configured to select one of the first demodulating means and the second demodulating means in accordance with a gain of the automatic gain control section.
- 8. A quadrature demodulator comprising reception means for receiving a signal transmitted by an RFID tag and containing a specific pattern and data following the specific pattern, multiplying the reception signal by a local signal to generate an I-signal, and multiplying the reception signal by the local signal shifted in phase by 90 degrees to generate a Q-signal, first demodulating means for squaring each of the I- and Q-signals and adding the resulting I- and Q-signals together to generate data on the basis of the addition result, second demodulating means for detecting the specific pattern in each of the I- and Q-signals to decode the data following one of the detected specific patterns, and selecting means for selecting one of the first demodulating means and the second demodulating means in accordance with a gain determined by the addition result.
Specification