Radar apparatus and objection detection method, and signal processing apparatus therefor
An FMCW radar apparatus employing frequency hopping technique in which a center frequency of each chirp signal is variable enables the accuracy of range measurement of the radar to be improved, by determining a high resolution range value based on a composite beat signal generated by determining a beat signal for each of a plurality of chirp signals, parts of respective frequency bands of which overlap one another, and then compensating the beat signal for a phase difference value.
1. A radar apparatus comprising:
an antenna assembly;
a signal transceiver transmitting a linear frequency modulation signal and receiving a signal reflected from an object via the antenna assembly; and
a signal processor extracting information on the object by controlling the signal transceiver and processing the received reflected signal,
wherein the signal transceiver is configured to
generate a plurality of chirp signals, each of which has a different center frequency from one or more previous chirp signals for each modulation period while having an individual frequency band equal to the one or more previous chirp signals,
transmit via the antenna assembly the plurality of chirp signals, and
receive via the antenna assembly the plurality of chirp signals reflected back at the radar apparatus,
wherein the signal processor comprises:
a function of deriving a first chirp signal and a second chirp signal that overlap each other in a fractional frequency band of 0 or more among the plurality of chirp signals,
a function of determining a phase difference value between a first beat signal corresponding to the first chirp signal and a second beat signal corresponding to the second chirp signal,
a function of generating a composite beat signal by compensating at least one of the first beat signal and the second beat signal for the phase difference value between the first beat signal and the second beat signal, and
a function of determining a high resolution range value of the object by using the composite beat signal, and
wherein the signal processor performs a detection algorithm for extracting information on the object determined by using each chirp signal, and only when an object detection peak obtained by performing the detection algorithm is not clear whether the object detection peak is a single object or a plurality of objects, performs the function of generating the composite beat signal by using overlapping chirp signals and the function of determining the high resolution range value.
2. The radar apparatus according to claim 1 , wherein the signal processor further comprises a function of deriving a third chirp signal that overlaps at least one of the first chirp signal or the second chirp signal in the fractional frequency band of 0 or more, and generating a third beat signal corresponding to the third chirp signal, and generates a composite beat signal by compensating at least one of the first beat signal, the second beat signal, or the third beat signal for a phase difference value between the third beat signal and at least one of the first beat signal or the second beat signal.
3. The radar apparatus according to claim 1 , wherein the phase difference value is proportional to product (R*Δfc) of the range value R of the object and a center frequency difference value Δfc that is a difference value between a first center frequency c1 of the first chirp signal and a second center frequency c2 of the second chirp signal.
4. The radar apparatus according to claim 1 , wherein a resolution of the high resolution range value determined by the composite beat signal is proportional to a center frequency difference value Δfc that is a difference value between a first center frequency c1 of the first chirp signal and a second center frequency c2 of the second chirp signal.
5. The radar apparatus according to claim 1 , wherein a resolution of the high resolution range value determined by the composite beat signal is proportional to a value (2BWe-BWo) obtained by subtracting an overlapping frequency band BWo from a value corresponding to two times the individual frequency band BWe.
6. A signal processing apparatus for a radar sensor for a vehicle, the signal processing apparatus comprising:
a signal generator generating and transmitting a plurality of chirp signals, each of which has a different center frequency from one or more previous chirp signals for each modulation period while having an individual frequency band equal to the one or more previous chirp signals;
a beat signal compositing circuit deriving a first chirp signal and a second chirp signal that overlap each other in a fractional frequency band of 0 or more among the plurality of chirp signals, determining a phase difference value between a first beat signal corresponding to the first chirp signal and a second beat signal corresponding to the second chirp signal, and generating a composite beat signal by compensating at least one of the first beat signal and the second beat signal for the phase difference value between the first beat signal and the second beat signal; and
a range information determining circuit determining a high resolution range value of an object having a range resolution greater than a range resolution by the individual frequency band by using the composite beat signal,
wherein the range information determining circuit performs a detection algorithm for extracting information on the object determined by using each chirp signal, and only when an object detection peak obtained by performing the detection algorithm is not clear whether the object detection peak is a single object or a plurality of objects, performs a function of generating the composite beat signal by using overlapping chirp signals and a function of determining the high resolution range value.
7. The signal processing apparatus according to claim 6 , wherein the signal compositing circuit further comprises a function of deriving a third chirp signal that overlaps at least one of the first chirp signal or the second chirp signal in the fractional frequency band of 0 or more, and generating a third beat signal corresponding to the third chirp signal, and generates a composite beat signal by compensating at least one of the first beat signal, the second beat signal, or the third beat signal for a phase difference value between the third beat signal and at least one of the first beat signal or the second beat signal.
8. The signal processing apparatus according to claim 6 , wherein the phase difference value is proportional to product (R*Δfc) of the range value R of the object and a center frequency difference value Δfc that is a difference value between a first center frequency c1 of the first chirp signal and a second center frequency c2 of the second chirp signal.
9. The signal processing apparatus according to claim 6 , wherein a resolution of the high resolution range value determined by the composite beat signal is proportional to a center frequency difference value Δfc that is a difference value between a first center frequency c1 of the first chirp signal and a second center frequency c2 of the second chirp signal.
10. The signal processing apparatus according to claim 6 , wherein a resolution of the high resolution range value determined by the composite beat signal is proportional to a value (2BWe-BWo) obtained by subtracting an overlapping frequency band BWo from a value corresponding to two times the individual frequency band BWe.
11. A method of detecting an object comprising:
generating and transmitting a plurality of chirp signals, each of which has a different center frequency from one or more previous chirp signals for each modulation period while having an individual frequency band equal to the one or more previous chirp signals;
deriving a first chirp signal and a second chirp signal that overlap each other in a fractional frequency band of 0 or more among the plurality of chirp signals;
determining a phase difference value between a first beat signal corresponding to the first chirp signal and a second beat signal corresponding to the second chirp signal;
generating a composite beat signal by compensating at least one of the first beat signal and the second beat signal for the phase difference value between the first beat signal and the second beat signal; and
determining a high resolution range value of the object having a range resolution greater than a range resolution by the individual frequency band by using the composite beat signal,
wherein the generating of the composite beat signal by using overlapping chirp signals and the determining of the high resolution range value are performed only when a detection algorithm is performed for extracting information on the object determined by using each chirp signal, and an object detection peak obtained by performing the detection algorithm is not clear whether the object detection peak is a single object or a plurality of objects.
12. The method of detecting the object according to claim 11 , wherein the phase difference value is proportional to product (R*Δfc) of the range value R of the object and a center frequency difference value Δfc that is a difference value between a first center frequency c1 of the first chirp signal and a second center frequency c2 of the second chirp signal.
13. The method of detecting the object according to claim 11 , wherein a resolution of the high resolution range value determined by the composite beat signal is proportional to a center frequency difference value Δfc that is a difference value between a first center frequency c1 of the first chirp signal and a second center frequency c2 of the second chirp signal.
14. The method of detecting the object according to claim 11 , wherein a resolution of the high resolution range value determined by the composite beat signal is proportional to a value (2BWe-BWo) obtained by subtracting an overlapping frequency band BWo from a value corresponding to two times the individual frequency band BWe.