Systems and methods to use radar in RFID systems
Systems and methods to use radar systems for radio frequency identification (RFID) applications. In one embodiment, radar systems are adapted to use RFID communications protocols and methods to enhance the usefulness of radar systems beyond the determination of the presence, distance, direction and/or speed of a vehicle or object, to additionally include the transmission of data such as object identification and additional messages or data.
1. A radio frequency identification (RFID) system, comprising:
an RFID tag storing one or more parameters that characterize radar signals used in the system and having a controller that adjusts states of the RFID tag,
wherein the states include a first state and a second state,
wherein the RFID tag is more reflective in the second state than in the first state, and
wherein data in reflected radar pulses reflected from the RFID tag is modulated according to the one or more parameters, and
wherein the one or more parameters comprise at least one of pulse repetition frequency, or pulse duration, or any combination thereof; and
a radar system including:
a radar transmitter,
a radar receiver, and
an RFID reader circuit, wherein:
the radar receiver receives a pulse of radio frequency electromagnetic wave transmitted by the radar transmitter and reflected by the RFID tag,
the RFID reader circuit determines, from the pulse of radio frequency electromagnetic wave received by the radar receiver, the data reflected by the RFID tag, and
the radar system determines at least one of distance, direction and speed of objects based on pulses of radio frequency electromagnetic wave transmitted by the radar transmitter and received by the radar receiver,
the radar transmitter transmits the radio frequency electromagnetic wave in a first mode to allow the RFID reader circuit to determine the data; and the radar transmitter is to transmit in a second mode to determine a range of the RFID tag.
2. The RFID system of claim 1 , wherein the RFID tag modulates the radio frequency electromagnetic wave according to a predetermined characteristic of electromagnetic waves transmitted by the radar transmitter.
3. The RFID system of claim 1 , wherein the radar system determines a position of the RFID tag based on a round trip time of the radio frequency electromagnetic wave.
4. The RFID system of claim 1 , wherein the radar system determines a speed of the RFID tag based on a Doppler frequency shift in the radio frequency electromagnetic wave reflected by the RFID tag.
5. A radio frequency identification (RFID) reader, comprising:
a transmitter configured to transmit pulses of a radio frequency electromagnetic wave;
a receiver configured to receive the pulses of the radio frequency electromagnetic wave reflected by an object;
a radar circuit of a radar system configured to determine at least a distance, a direction or a speed of the object based on pulses of radio frequency electromagnetic wave reflected by the object and received in the receiver;
a reader circuit configured to determine data modulated on the pulses of radio frequency electromagnetic wave reflected by the object and received in the receiver,
wherein the object modulates the data on the pulses reflected by the object using a controller according to one or more parameters stored in the object that characterize radar signals used in the system,
wherein the one or more parameters comprise at least one of pulse repetition frequency, or pulse duration, or any combination thereof, and
wherein a predetermined number of bits of the data are modulated on each of the pulses reflected by the object; and
a duplexer configured to:
couple the radar circuit to the transmitter and the receiver in a first mode, and
couple the RFID reader circuit to the transmitter and the receiver in a second mode.
6. The RFID reader of claim 5 , wherein the reader circuit controls the transmitter to modulate data on a radio frequency electromagnetic wave transmitted by the transmitter.
7. A radio frequency identification (RFID) reader, comprising:
a transmitter configured to transmit pulses of a radio frequency electromagnetic wave;
a receiver configured to receive the pulses of the radio frequency electromagnetic wave reflected by an object;
a radar circuit of a radar system configured to determine at least a distance, a direction or a speed of the object based on pulses of radio frequency electromagnetic wave reflected by the object and received in the receiver;
a reader circuit configured to determine data modulated on the pulses of radio frequency electromagnetic wave reflected by the object and received in the receiver,
wherein the object modulates the data on the pulses reflected by the object using a controller according to one or more parameters stored in the object that characterize radar signals used in the system,
wherein the one or more parameters comprise at least one of pulse repetition frequency, or pulse duration, or any combination thereof,
wherein a predetermined number of bits of the data are modulated on each of the pulses reflected by the object, and
wherein the receiver has a matched filter configured to receive an input signal generated according to the pulses of radio frequency electromagnetic wave reflected by the object and received in the receiver; and a pulse width of an output of the matched filter is smaller than a pulse width of the input.