ADJUSTING PARAMETERS ASSOCIATED WITH TRANSMITTER LEAKAGE
An apparatus comprises a transmitter, a receiver, an antenna and a signal cancellation circuit. The transmitter is configured to send a transmitter signal associated with a frequency. The receiver is associated with the frequency. The antenna is coupled to the transmitter and the receiver. The signal cancellation circuit is coupled to the transmitter, the receiver and the antenna. The signal cancellation circuit is configured to phase shift a first portion of the transmitter signal to produce a phase-shifted signal. The signal cancellation circuit is configured to combine the phase-shifted signal with a second portion of the transmitter signal to produce a combined signal. The second portion of the transmitter signal is associated with a reflection of a third portion of the transmitter signal from the antenna. The first portion, the second portion and the third portion of the transmitter signal are different from each other.
1 . A method for reducing noise, comprising:
sampling, on a receiver path, Radio Frequency (RF) signal including a signal received from a transponder and an interference signal, the interference signal based, at least in part, on an RF transmission signal;
dynamically adjusting a portion of the RF transmission signal based, at least in part, on the sampled signal; and
combining the adjusted portion of the RF transmission signal into receive path to reduce the interference signal.
2 . The method of claim 1 , further comprising splitting, from the RF transmission signal, the portion of the RF transmission signal.
3 . The method of claim 1 , wherein dynamically adjusting the portion of the transmission signal comprises:
dynamically adjusting the amplitude of the portion of the transmission signal based, at least in part, on the sampled signal; and
dynamically adjusting the phase of the portion of the transmission signal based, at least in part, on the sampled signal.
4 . The method of claim 1 , wherein the interference signal includes a portion of the RF transmission signal reflected by an antenna.
5 . The method of claim 1 , a frequency of the RF transmission signal is substantially the same frequency of the signal received from the transponder.
6 . The method of claim 1 , wherein the receive-path signal is sampled as an RF signal.
7 . The method of claim 1 , wherein the interference signal is reduced by at least 30 dB by the adjusted portion of the transmission signal.
8 . The method of claim 1 , wherein sampling the RF signal from the received path comprises determining an amplitude of the receive-path signal.
9 . Method of claim 1 , further comprising:
dynamically generating control signals for adjusting the amplitude of the portion of the RF transmission signal based, at least in part, on the sampled signal;
dynamically generating control signals for adjusting the phase of the portion of the RF transmission signal based, at least in part, on the sampled signal; and
wherein the amplitude and the phase of the portion of the RF transmission signal are adjusted in response to at least the control signals.
10 . The method of claim 1 , wherein the portion of the RF transmission signal is dynamically adjusted using a control loop.
11 . An RF reader, comprising:
a detector configured to sample, on a receive path, an Radio Frequency (RF) signal including a signal received from a transponder and an interference signal, the interference signal based, at least in part, on a RF transmission signal;
a control element configured to dynamically adjust a portion of the RF transmission signal based, at least in part, on the sampled signal; and
a coupler configured to combine the adjusted portion of the RF transmission signal to the receive path to reduce the interference signal.
12 . The RF reader of claim 11 , further comprising a coupler configured to split, from the RF transmission signal, the portion of the RF transmission signal.
13 . The RF reader of claim 11 , wherein the control element comprises:
a amplitude element configured to dynamically adjust an amplitude of the portion of the transmission signal based, at least in part, on the sampled signal; and
a phase element configured to dynamically adjust a phase of the portion of the transmission signal based, at least in part, on the sampled signal.
14 . The RF reader of claim 11 , wherein the amplitude element comprises a variable attenuator.
15 . The RF reader of claim 11 , wherein the phase element comprises a phase shifter.
16 . The RF reader of claim 11 , wherein the interference signal includes a portion of the RF transmission signal reflected by an antenna.
17 . The RF reader of claim 11 , the frequency of the RF transmission signal is substantially the same frequency of the signal received from the transponder.
18 . The RF reader of claim 11 , wherein the receive-path signal is sampled as an RF signal.
19 . The RF reader of claim 11 , wherein the interference signal is reduced by at least 30 dB by the adjusted portion of the transmission signal.
20 . The RF reader of claim 11 , wherein the detector is configured to determine an amplitude of the receive-path signal.
21 . The RF reader of claim 11 , further comprising wherein the control element includes a controller configured to dynamically generate control signals for adjusting an amplitude and a phase of the portion of the RF transmission signal based, at least in part, on the sampled signal, wherein an amplitude and a phase of the portion of the RF transmission signal are adjusted in response to at least the control signals.
22 . The RF reader of claim 1 , wherein the portion of the RF transmission signal is dynamically adjusted using a control loop.