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Issue #211 February 2008
RFID Payment Terminal
by Carlos Cossio
Start | System Overview | Energy Transmission | 100% Amplitude Modulation | Load Modulation | MIFARE Card | MIFARE and ISO 14443 | Pay as You Go | Hardware Design | Antenna Design Rules | Antenna Size | Directly Matched Antenna | Firmware Design | Catch the Wave! | Sources & PDF
ANTENNA DESIGN RULES
The MF RC531 is a single-reader IC. It is designed to achieve operating distances of up to 100 mm without external amplifiers. The design of the remaining passive RF part is straightforward. First, you have to decide which of the possible basic concepts meets the application requirements best. Two different concepts are possible when designing an antenna and a matching circuit.
On one hand, directly matched antennas can be used to build small, complete terminals with a minimum distance between a reader and an antenna. Possible applications could be an access control reader in a small housing or a handheld reader.
On the other hand, 50-W matched antennas can be used for an easy solution to achieve long distances between the reader and the antenna using a coaxial cable. With a coaxial cable between the reader matching circuit and the antenna itself, distances up to 10 m between these parts are possible.
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