Antenna circuit and a method of optimisation thereof
AssigneeHong Kong Applied Science and Technology Research Institute Company Limited
InventorsTak Ki Wan, Yan Liu, Song He, Dan Yang, Chi Keung Angus Mak
Life of this patent
Estimating the term…
Abstract
An antenna circuit is having an impedance circuit which can cancel signal leakage from the input port into the isolation port of a directional coupler. The antenna circuit further comprises a second impedance circuit for optimizing power transfer from the input port to the output port of the directional coupler. Furthermore, the antenna is tunable in order to maximize the reception strength of the antenna. The antenna circuit provides at once the possibility of tuning the antenna strength, optimizing the power transmission and reducing signal jamming by cancelling signal leakage. The antenna finds use as an effective and miniature RFID antenna.
Claims19
A method of optimising an antenna circuit, comprising:
- providing a directional coupler having an input port, an output port that transmits a signal to an antenna, and an isolation port;
- and
- providing a first impedance load at the output port of the directional coupler that has a mismatched impedance to the output port to reflect at least a portion of the signal back into the output port to substantively cancel a leakage signal that leaks from the input port into the isolation port.
An antenna circuit, comprising:
- a directional coupler having an input port, an isolation port, and an output port that transmits a signal;
- a first impedance circuit that connects to the output port of the directional coupler and to an antenna;
- wherein the impedance circuit is tunable to mismatch an impedance of the output port and an impedance of the antenna;
- the first impedance circuit having an initialisation tuning that has a first initialisation impedance that reflects the signal back to the output port of the directional coupler to substantively cancel a leakage signal that leaks from the input port into the isolation port of the directional coupler;
- wherein the first initialisation impedance is set at a value to achieve a reflection coefficient between the output port of the directional coupler and the first impedance circuit of:
- Γ
- A
- =
- -
- I
- CT
- where,
- ΓA is the reflection coefficient between the output port and the first impedance circuit;
- T refers to insertion loss from the input port to the output port;
- C refers to a coupling factor between the input port and a couple port;
- and
- I refers to an isolation factor between the input port and the isolation port;
- wherein the first impedance circuit is tuned from the initialisation tuning, by selecting and applying a set of optimal values, to adjust an impedance to substantively cancel the leakage signal that is un-cancelled at the first initialisation impedance, wherein the set of optimal values for the first impedance circuit are pre-determined.
A handheld communication device, comprising:
- a radio-frequency identification (RFID) antenna circuit having a directional coupler that includes an input port, an output port that transmits a signal, and an isolation port;
- and
- an impedance load connected to the output port, wherein
- wherein the impedance load has a mismatched impedance to the output port of the directional coupler that reflects the signal back to the output port to substantively cancel a leakage signal that leaks from the input port into the isolation port.
A directional coupler circuit, comprising:
- a directional coupler having an input port, an output port that transmits a signal and an isolation port;
- and
- an impedance load connected to the output port,
- wherein the impedance load has a mismatched impedance to the output port of the directional coupler that reflects the signal back to the output port to substantively cancel a leakage signal that leaks from the input port into the isolation port.
Dependencies are inferred from the claim text.