Input impedance arrangement for RF transponder
First Claim
1. A transponder for a radio frequency (RF) identification system comprising an antenna having an antenna impedance having a real part (RA) connected to transponder circuitry presenting a load impedance having a real part (RL), a ratio
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Accused Products
Abstract
A transponder 14.1 for a radio frequency (RF) identification system comprises an antenna 22.1 having an antenna Impedance (ZA) having a real part (RA) connected to transponder circuitry presenting a load impedance (ZL) having a real part (RL), a ratio (Ra/Rl) of the real part (RL) of the load impedance and the real part (RA) of the antenna impedance having a first value that is bigger than one when the transponder is not transmitting data. During transmission of data the ratio is switched between the first value and a second smaller value.
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Citations
8 Claims
- 1. A transponder for a radio frequency (RF) identification system comprising an antenna having an antenna impedance having a real part (RA) connected to transponder circuitry presenting a load impedance having a real part (RL), a ratio
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8. A method of reading a plurality of radio frequency transponders each comprising an antenna having an antenna impedance having a real part and a load connected to the antenna, the load having a load impedance having a real part, the method comprising the steps of:
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transmitting a radio frequency interrogation signal towards the transponders;
at each transponder, normally causing a ratio of the real part of the load impedance and the real part of the antenna impedance to have a first value of bigger than one; and
when transmitting date, causing the ratio to be switched between the first value and a second smaller value in accordance with the data. 9. A method of modulating an impinging radio frequency signal comprising the steps of;
receiving the signal via an antenna having an antenna impedance having a real part;
adjusting a real part of a load impedance connected to the antenna to cause a ratio of the real part of the load impedance and the real part of the antenna impedance to alternate between a first value bigger than one and a second smaller value, thereby to backscatter modulate the impinging signal.
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Specification