ELECTRIC VEHICLE CHARGING VIA RF LOOPS TO AVOID NEED FOR PRECISE ALIGNMENT WITH WIRELESS CHARGING EQUIPMENT
A loop antenna in an electric vehicle receives energy wirelessly from a source external to the vehicle, such as from a Radio Frequency (RF) emitter. The use of RF loop antennas to both transmit and receive power greatly reduces the need to align the vehicle with charging station equipment.
1 . An apparatus for charging an electric vehicle comprising:
a first wire loop antenna, disposed within a the vehicle;
a second wire loop antenna, arranged to beneath the vehicle and to transmit energy wirelessly from a radio frequency energy source to the first antenna;
with a diameter of the first wire loop antenna at least three times a diameter of the second wire loop antenna; and
an automatic impedance adjustment circuit connected to at least one of the first or second wire loop antenna.
2 . The apparatus of claim 1 wherein each of the first and second wire loop antennas are a single turn wire loop.
3 . The apparatus of claim 1 wherein the adjustment circuit further comprises a Voltage Standing Wave Ratio (VSWR) detector and an output impedance adjustment circuit coupled to the second wire loop antenna.
4 . The apparatus of claim 1 wherein the adjustment circuit further comprises a detector and a receive impedance adjustment circuit connected to the first wire loop antenna.
5 . The apparatus of claim 1 wherein the first wire loop is three feet in diameter.
6 . The apparatus of claim 5 wherein the second wire loop is between one-half and one foot in diameter.
7 . The apparatus of claim 1 wherein the first wire loop is formed of a metallic pipe having a cross sectional dimension between one-quarter and one-half inch.
8 . The apparatus of claim 1 wherein the radio frequency energy source operates between 30 and 60 MHz.
9 . The apparatus of claim 1 wherein the second loop antenna and radio frequency energy source are packaged in a floor mat.
10 . The apparatus of claim 1 wherein the first loop antenna is further coupled to ambient power scavenging circuits.
11 . The apparatus of claim 1 wherein one or more dipole elements are disposed withing the first wireless loop.
12 . The apparatus of claim 1 addtionally comprising:
a VSWR meter coupled to the second wireless loop;
a detector coupled to the output of the VSWR meter to detect variations in transmit power above a determined level; and
a controller, coupled to disable the radio frequency energy source in response to the detector.