Electrical computers and digital data processing systems: input/ – Input/output data processing – Concurrent input/output processing and data transfer
Patent
1998-03-09
2000-07-11
Lee, Thomas C.
Electrical computers and digital data processing systems: input/
Input/output data processing
Concurrent input/output processing and data transfer
710129, 711115, 711170, G06F 1314
Patent
active
060887419
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-contact memory card system that is configured so as to perform sending and receiving of data by means of electromagnetic coupling (known also as electromagnetic induction), and more specifically to a storage medium system that uses a contactless memory card which is configured so as to perform sending and receiving of data by means of electromagnetic coupling (known also as electromagnetic induction) via an LC resonant circuit.
2. Description of Related Art
In recent years, work on achieving practically usable contactless memory cards for as a small, highly reliable storage medium has progressed, resulting in an expanded range of applications thereof, as well as a significant increase in their storage capacity.
Along with the achievement of large storage capacity, there is a naturally occurring need to transfer data at high speed.
In general, however, it is extremely difficult to increase the speed of data transmission when performing transmission using an electromagnetic coupling via an LC resonant circuit.
Methods of increasing the transmission speed which can be envisioned include such methods as (1) simply decreasing the amount of time required to send each bit, (2) providing a plurality of LC resonant circuits so as to send data in parallel, and (3) employing multiphase modulation so as to send a plurality of data bits simultaneously.
The last method (3) requires a plurality of modulator and demodulator circuits for multiphase PSK or multiphase FSK, making its employment particularly difficult in the field of contactless memory card systems, in which there is a strong demand for compact, lowcost readers and writers.
A known storage medium system that makes use of such a contactless memory card, such as that shown in FIG. 8, has a reader/writer-side electromagnetic coupling interface section 1 and a memory card side electromagnetic coupling interface section 10.
FIG. 8 is the circuit diagram of the communication circuit of a contactless memory card system of the past, and FIG. 9 is a drawing that shows the main waveforms in therein.
In a storage medium system which uses the contactless memory card of the past as shown in FIG. 8, a printed coil type antenna 2 of the reader/writer-side electromagnetic coupling interface 1 and a printed coil type antenna 12 of the LC resonant circuit 11 of the memory card side electromagnetic coupling interface 10 are in opposition to one another when access is performed, bringing these elements into electromagnetic coupling condition so that data can be passed therebetween.
That is, the antennas 2 and 12 on the reader/writer side and card side, respectively, are both used for both sending and receiving.
If the start-stop synchronized serially transmitted data BD having a bit time width (time length of 1 bit) of tb shown in FIG. 9 is sent by the card side to the reader/writer side, corresponding to the time when the transmitted data BD is 0, at the transmitted signal forming circuit 15, a transmitted signal TX is formed by a single-shot signal, this signal driving the transmitting driving transistor 13.
That is, each time the above-noted transmitted data DB is 0, the resonant circuit 11 is single-shot driven, resulting in electromagnetic induction in the antenna 2 of the reader/writer-side electromagnetic coupling interface section 1.
When this occurs, although the drive is single-shot, because of the resonating phenomenon in the resonant circuit 11, the current waveform in the antenna 12 is a freely damped waveform, the induced waveform in the antenna 2 of the reader/writer-side interface section 1 also exhibiting a similar freely damped waveform shape.
The above-noted induced waveform occurring in the antenna 2 is input to the receiving demodulation circuit 3 at which it is demodulated, the DC component being first cut from and bias being applied to this signal by means of capacitor C1 and resistors R1 and R2, thereby becoming the input signal WP which is then input to a window
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Citizen Watch Co. Ltd.
Lee Thomas C.
Tzeng Fred F.
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