Quarter wave phase shifted diode detector circuit
First Claim
1. A phase shifting diode detector system for an RFID reader comprising:
- quarter-wave delay circuitry coupled between a forward transmitted signal of the RFID reader applied at a first end of the delay circuitry, and a reflected signal returning from an RFID tag applied at a second end of the delay circuitry; and
a pair of diode detector bridges, each comprising a series-coupled diode pair configured such that diode polarities in each bridge are reversed relative to the output thereof, to produce opposite rectified signal output polarities;
wherein an input to each of the bridges is capacitively coupled, from the junction between each said diode pair, to a respective opposite end of the delay circuitry.
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Abstract
A phase shifting diode detector system for an RFID reader. Quarter-wave delay circuitry is coupled between a forward transmitted signal of the RFID reader applied at a first end of the delay circuitry, and a reflected signal returning from an RFID tag applied at a second end of the delay circuitry. The system includes a pair of diode detector bridges, each comprising a series-coupled diode pair configured such that diode polarities in each bridge are reversed relative to the output thereof, to produce opposite rectified signal output polarities. An input to each of the bridges is capacitively coupled, from the junction between each said diode pair, to a respective opposite end of the delay circuitry.
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Citations
20 Claims
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1. A phase shifting diode detector system for an RFID reader comprising:
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quarter-wave delay circuitry coupled between a forward transmitted signal of the RFID reader applied at a first end of the delay circuitry, and a reflected signal returning from an RFID tag applied at a second end of the delay circuitry; and
a pair of diode detector bridges, each comprising a series-coupled diode pair configured such that diode polarities in each bridge are reversed relative to the output thereof, to produce opposite rectified signal output polarities;
wherein an input to each of the bridges is capacitively coupled, from the junction between each said diode pair, to a respective opposite end of the delay circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A phase shifting diode detector system for an RFID reader comprising:
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quarter-wave delay circuitry coupled between a forward transmitted signal of the RFID reader applied at a first end of the delay circuitry, and a reflected signal returning from an RFID tag applied at a second end of the delay circuitry; and
a pair of diode detector bridges, each comprising a series-coupled diode pair configured such that diode polarities in each bridge are reversed relative to the output, at a first end of each diode pair, to produce opposite rectified signal output polarities, and wherein the second end of each diode pair is coupled to ground;
wherein the input to a first one of the bridges is capacitively coupled to the first end of the delay circuitry, and the input to the second one of the bridges is capacitively coupled to the second end of the delay circuitry, wherein the input to each of the bridges is connected to the junction between each said diode pair. - View Dependent Claims (9, 10, 11, 12)
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13. A phase shifting diode detector system for an RFID reader comprising:
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quarter-wave delay circuitry coupled between a forward transmitted sine wave signal of the RFID reader applied at a first end of the delay circuitry, and a reflected sine wave signal returning from an RFID tag applied at a second end of the delay circuitry; and
a pair of diode detector bridges, each comprising a series-coupled diode pair configured such that diode polarities in each bridge are reversed relative to the output thereof, to produce opposite rectified signal output polarities;
wherein the bridges each have an input, connected to the junction between each said diode pair, capacitively coupled to a respective opposite end of the delay circuitry;
wherein the transmitted sine wave enters the quarter-wave delay circuitry at one end and the received sine wave enters from the opposite end, causing both wave fronts to produce voltages that are phase-shifted 90 degrees to create two DC voltages are of the same polarity which are added in a summing amplifier to double the signal amplitude; and
wherein each of the diode detector bridges rectifies the transmitter'"'"'s carrier amplitude signal to generate rectified output voltages that are in proportion to, and opposite in polarity from, the envelope of the transmitter carrier, wherein the output voltages are fed in series to cancel the amplitude noise component of the signal returning from the RFID tag. - View Dependent Claims (14, 15)
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16. In an RFID reader, a method for doubling the signal amplitude of, and reducing amplitude noise of, a signal received from an RFID tag, comprising:
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coupling quarter-wave delay circuitry between a forward transmitted signal of the RFID reader applied at a first end of a delay circuitry, and the signal received from the RFID tag applied at a second end of the delay circuitry;
capacitively coupling, to a respective opposite end of the delay circuitry, an input to each of a pair of diode detector bridges, wherein each of the bridges comprises a series-coupled diode pair configured such that diode polarities in each bridge are reversed relative to the output thereof, to produce opposite rectified signal output polarities, wherein the input to each of the bridges is coupled to a junction between each diode pair in a respective bridge. - View Dependent Claims (17, 18)
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19. A diode detector system for an RFID reader comprising:
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a pair of diode detector bridges, each comprising a series-coupled diode pair configured such that diode polarities in each bridge are reversed relative to the output thereof, to produce modulated signals having opposite rectified signal polarities;
wherein a forward transmitted signal of the RFID reader and a reflected signal returning from an RFID tag are separated by a phase shift of 90 degrees, and are applied to both inputs of the pair of diode detector bridges; and
wherein the junction between each said diode pair corresponds to the input in each of the bridges. - View Dependent Claims (20)
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Specification