Radio-card communication system
First Claim
1. A radio-card communications system having a radio card for transmitting a response signal in response to a question signal, and a card reader for transmitting the question signal and receiving the response signal,said radio card comprising:
- carrier-receiving means for receiving a carrier transmitted from said card reader;
sub-carrier generating means for generating a sub-carrier having a frequency lower than a frequency of the carrier;
first phase-modulating means for phase-modulating the sub-carrier with the response signal, thereby to generate a PSK signal;
second phase-modulating means for phase-modulating the carrier with the PSK signal, thereby to generate a PSK-PSK signal; and
PSK-PSK signal transmitting means for transmitting the PSK-PSK signal to said card reader; and
said card reader comprising;
carrier-transmitting means for transmitting the carrier to said radio card in response to the response signal;
PSK-PSK signal receiving means for receiving the PSK-PSK signal from said radio card;
sub-carrier extracting means for performing orthogonal detection on the PSK-PSK signal, thereby to extract a sub-carrier component; and
demodulating means for extracting a phase-modulated component from the sub-carrier component, thereby to demodulate the response signal.
1 Assignment
0 Petitions
Accused Products
Abstract
To receive a response signal from a radio card, a card reader transmits a carrier (not modulated) to the radio card. In the radio card, a phase modulator phase-modulates the a sub-carrier with a response signal, thereby generating a PSK signal, and a phase modulator phase-modulates the carrier with the PSK signal, producing a PSK-PSK signal. The PSK-PSK signal is supplied to an antenna via a signal-extracting device. The antenna sends the PSK-PSK signal toward the card reader. In the card reader, a distributor distributes the PSK-PSK signal to a synchronous detector and an orthogonal detector. The detectors performs synchronous detection by using carriers which differ in phase by 90°. Low-pass filters extract sub-carrier components from the outputs of the detectors. The sub-carrier components are delayed and detected by delay detectors and added together by an adder. The level of the output of the adder is determined by a data discriminator, whereby the card reader obtains the response signal transmitted from the radio card.
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Citations
9 Claims
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1. A radio-card communications system having a radio card for transmitting a response signal in response to a question signal, and a card reader for transmitting the question signal and receiving the response signal,
said radio card comprising: -
carrier-receiving means for receiving a carrier transmitted from said card reader; sub-carrier generating means for generating a sub-carrier having a frequency lower than a frequency of the carrier; first phase-modulating means for phase-modulating the sub-carrier with the response signal, thereby to generate a PSK signal; second phase-modulating means for phase-modulating the carrier with the PSK signal, thereby to generate a PSK-PSK signal; and PSK-PSK signal transmitting means for transmitting the PSK-PSK signal to said card reader; and said card reader comprising; carrier-transmitting means for transmitting the carrier to said radio card in response to the response signal; PSK-PSK signal receiving means for receiving the PSK-PSK signal from said radio card; sub-carrier extracting means for performing orthogonal detection on the PSK-PSK signal, thereby to extract a sub-carrier component; and demodulating means for extracting a phase-modulated component from the sub-carrier component, thereby to demodulate the response signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification