System and method of emulating echo signals from emulated targets with reduced interference from reflection
A system and method emulate an echo signal from an emulated target in response to a radar signal from a radar DUT. The system includes an antenna configured to receive the radar signal, and to direct a reflected portion of the radar signal away from an incident direction of the radar signal at a predetermined deflection angle to prevent the radar DUT from receiving the reflected portion; and a transceiver configured to provide an RF signal having an RF frequency shifted from a frequency of the radar signal in an amount indicating a distance to the emulated target, and to transmit the RF signal to the radar DUT as an emulated echo signal. An antenna pattern includes a peak beam angled away from a normal incidence of the antenna at a beam squint angle that compensates for the predetermined deflection angle to direct the peak beam toward the radar DUT.
1 . A system for emulating an echo signal reflected from an emulated target in response to a radar signal transmitted by a radar device under test (DUT), the system comprising:
at least one antenna positioned outside a near-field of the radar DUT, and configured to receive the radar signal over-the-air from the radar DUT, wherein the at least one antenna reflects a portion of the radar signal and is configured to direct the reflected portion of the radar signal away from an incident direction of the radar signal at a predetermined deflection angle to prevent the radar DUT from receiving the reflected portion of the radar signal, the incident direction being substantially perpendicular to a wavefront of the radar signal; and
a transceiver coupled to the at least one antenna to receive the radar signal, wherein the transceiver is configured to mix the received radar signal with a generated signal having a frequency that provides a radio frequency (RF) signal having an RF frequency shifted from a radar frequency of the radar signal in an amount indicating a distance to the emulated target, and to transmit the RF signal to the radar DUT as an emulated echo signal via the at least one antenna,
wherein the at least one antenna has an antenna pattern comprising a peak beam angled away from a normal incidence of the at least one antenna at a beam squint angle, the beam squint angle compensating for the predetermined deflection angle in order to direct the peak beam toward the radar DUT for receiving the radar signal and transmitting the RF signal.
2 . The system of claim 1 , wherein the at least one antenna comprises a patch array antenna, wherein the patch array antenna comprises a ground plane mirror canted at a blaze angle from the incident direction of the radar signal, the predetermined deflection angle being about twice the blaze angle.
3 . The system of claim 2 , wherein the blaze angle is the same value as and opposite to the squint angle.
4 . The system of claim 2 , wherein the patch array antenna further comprises:
a plurality of microstrips extending in parallel from at least one feed source; and
a plurality of patch elements connected to the plurality of microstrips, and arranged in parallel rows across the plurality of microstrips, wherein adjacent rows of the parallel rows are offset an electrical degree distance from one another to produce a phase gradient between the adjacent rows to provide the beam squint angle of the patch array antenna.
5 . The system of claim 4 , wherein the at least one feed source comprises an unbalanced port.
6 . The system of claim 4 , wherein the at least one feed source comprises balanced differential ports.
7 . The system of claim 1 , wherein the at least one antenna comprises a plated cavity backed antenna comprising a plated air cavity in a substrate, and a dipole antenna arranged on the substrate over the air cavity such that the air cavity acts as a reflector, and wherein a position of the dipole antenna relative to a cavity physical center of the air cavity changes the antenna pattern of the dipole antenna to provide the beam squint angle of the cavity backed antenna.
8 . The system of claim 7 , wherein the beam squint angle is in an opposite direction from an offset position of an antenna phase center of the dipole antenna from the cavity physical center.
9 . The system of claim 1 , wherein the predetermined deflection angle and the squint angle are in a substantially vertical plane with respect to the incident direction of the radar signal.
10 . The system of claim 1 , wherein the predetermined deflection angle and the squint angle are in a substantially horizontal plane with respect to the incident direction of the radar signal.
11 . A method for emulating an echo signal reflected from an emulated target in response to a radar signal transmitted by a radar device under test (DUT), the method comprising:
angling at least one antenna of a radar target simulator (RTS) at a blaze angle with respect to an incidence direction of a radar signal to be transmitted by the radar DUT, wherein the at least one antenna is outside a near-field of the radar DUT;
adjusting an antenna pattern of the at least one antenna to angle a peak beam of the antenna pattern away from a normal incidence of the at least one antenna at a beam squint angle;
receiving a radar signal over-the-air from the radar DUT using the adjusted antenna pattern, and reflecting a portion of the radar signal away from the incident direction of the radar signal at a predetermined deflection angle due to the blaze angle of the at least one antenna to prevent the radar DUT from receiving the reflected portion of the radar signal;
mixing the received radar signal with a locally generated signal having a frequency that provides a radio frequency (RF) signal having an RF frequency shifted from a radar frequency of the radar signal in an amount indicating a distance to the emulated target; and
transmitting the RF signal to the radar DUT as an emulated echo signal via the at least one antenna using the adjusted antenna pattern,
wherein the beam squint angle compensates for the predetermined deflection angle in order to direct the peak beam toward the radar DUT for receiving the radar signal and transmitting the RF signal.
12 . The method of claim 11 , wherein the at least one antenna comprises a patch array antenna having a ground plane mirror canted at the blaze angle from the incident direction of the radar signal, the predetermined deflection angle being about twice the blaze angle.
13 . The method of claim 12 , wherein the blaze angle is the same value as and opposite to the beam squint angle.
14 . The method of claim 11 , wherein the at least one antenna comprises a plated cavity backed antenna having a plated air cavity in a substrate, and a dipole antenna arranged on the substrate over the air cavity such that the air cavity acts as a reflector, and wherein a position of the dipole antenna relative to a cavity physical center of the air cavity changes the antenna pattern of the dipole antenna to provide the beam squint angle of the cavity backed antenna.
15 . The method of claim 14 , wherein the beam squint angle is in an opposite direction from an offset position of an antenna phase center of the dipole antenna from the cavity physical center.
16 . The method of claim 11 , wherein the predetermined deflection angle and the beam squint angle are in a substantially vertical plane with respect to the incident direction of the radar signal.
17 . The method of claim 11 , wherein the predetermined deflection angle and the beam squint angle are in a substantially horizontal plane with respect to the incident direction of the radar signal.
18 . An antenna system for receiving a radar signal transmitted by a radar device under test (DUT) outside a near-field of the radar DUT, and transmitting an emulated echo signal reflected from an emulated target to the radar DUT in response to the radar signal, the antenna system comprising:
a plurality of microstrips extending in parallel from at least one feed source;
a plurality of matching feedlines connected to the plurality of microstrips;
a plurality of patch elements connected to the plurality of microstrips, and arranged in parallel rows across the plurality of microstrips; and
a ground plane for the plurality of patch elements, wherein at least the ground plane is angled to reflect a portion of the radar signal away from an incident direction of the radar signal at a predetermined deflection angle to prevent the radar DUT from receiving the reflected portion of the radar signal, the incident direction being substantially perpendicular to a wavefront of the radar signal,
wherein an antenna pattern of the antenna system comprises a peak beam angled away from a normal incidence of the ground plane at a beam squint angle, the beam squint angle compensating for the predetermined deflection angle in order to direct the peak beam toward the radar DUT for receiving the radar signal and transmitting the emulated echo signal.
19 . The antenna system of claim 18 , wherein the beam squint angle is in a substantially horizontal plane with respect to the incident direction of the radar signal, and is a function of respective lengths of the plurality of matching feedlines.
20 . The antenna system of claim 18 , wherein the beam squint angle is in a substantially vertical plane with respect to the incident direction of the radar signal, and is a function of lengths between adjacent patch elements on each of the plurality of microstrips.