HDX demodulator
First Claim
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1. A process for demodulating a low frequency half-duplex (HDX) frequency shift keying (FSK signal, comprising:
- receiving the HDX FSK signal using a resonant antenna, where the HDX FSK signal comprises a plurality of HDX FSK signal frequencies distributed around a center frequency nominally at mid-point between the lowest and highest HDX FSK signal frequencies;
upwardly mixing the HDX FSK signal to an intermediate frequency FSK signal having a center frequency higher than the center frequency of the received HDX FSK signal by mixing the HDX FSK signal with a fixed local oscillator frequency;
filtering the intermediate frequency FSK signal using at least one ceramic bandpass filter, wherein the at least one ceramic bandpass filter has a 6 dB bandwidth of at least +/−
10 KHz centered at the intermediate frequency; and
demodulating the filtered intermediate frequency FSK signal to produce a binary output;
wherein the HDX FSK signal frequencies are 134.2 KHz and 124.2 KHz.
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Abstract
Low noise mixers for use in RFID readers and RFID readers configured to receive data from ISO HDX transponders in accordance with embodiments of the invention are illustrated. One embodiment of the invention receives the HDX FSK signal using a resonant antenna, upwardly mixes the FSK signal to an intermediate frequency, filters the intermediate frequency FSK signal using at least one ceramic bandpass filter, and demodulates the filtered intermediate frequency FSK signal to produce a binary output.
62 Citations
12 Claims
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1. A process for demodulating a low frequency half-duplex (HDX) frequency shift keying (FSK signal, comprising:
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receiving the HDX FSK signal using a resonant antenna, where the HDX FSK signal comprises a plurality of HDX FSK signal frequencies distributed around a center frequency nominally at mid-point between the lowest and highest HDX FSK signal frequencies; upwardly mixing the HDX FSK signal to an intermediate frequency FSK signal having a center frequency higher than the center frequency of the received HDX FSK signal by mixing the HDX FSK signal with a fixed local oscillator frequency; filtering the intermediate frequency FSK signal using at least one ceramic bandpass filter, wherein the at least one ceramic bandpass filter has a 6 dB bandwidth of at least +/−
10 KHz centered at the intermediate frequency; anddemodulating the filtered intermediate frequency FSK signal to produce a binary output; wherein the HDX FSK signal frequencies are 134.2 KHz and 124.2 KHz. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An RFID receiver, comprising:
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a resonant antenna configured to receive a half-duplex (HDX) frequency shift keying (FSK) signal from a transponder, where the HDX FSK signal comprises a set of HDX FSK signal frequencies distributed around a center frequency nominally at mid-point between the lowest and highest HDX FSK signal frequencies; a mixer configured to upwardly mix an FSK signal received via the resonant antenna to an intermediate frequency FSK signal having a center frequency higher than the center frequency of the received FSK signal using a local oscillator frequency, where the local oscillator is a fixed frequency local oscillator; at least one ceramic filter configured to bandpass filter the intermediate frequency FSK signal, wherein the at least one ceramic filter has a 6 dB bandwidth of at least +/−
10 KHz centered at the intermediate frequency;at least one intermediate frequency amplifier configured to amplify the filtered frequency intermediate FSK signal; and a demodulator configured to demodulate the filtered intermediate frequency FSK signal and detect binary data; wherein the resonant antenna is configured to receive HDX FSK signal frequencies of 134.2 KHz and 124.2 KHz. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification