Methods and apparatus for a self-calibrated signal injection setup for in-field receive phased array calibration system
Methods and apparatus provide calibration of a system using a cable check configuration and a calibration test configuration. A short to ground reflects an injected signal to characterize a first signal path in the cable check configuration. Switch setting can then be adjusted to inject a signal that is coupled to an array element and received from a feed. The signal paths can be characterized to enable in-field calibration testing.
1. A method, comprising:
injecting a first signal through a first signal path including a first element, a first cable, a multiport switch, a second cable, and a feed switch;
setting the feed switch to have a connection to ground prior to injecting the first signal;
receiving the first signal reflected from ground through the feed switch, the second cable, the multiport switch, the first cable, the first element, and a receive switch for reception by a receiver;
measuring characteristics of the first signal received by the receiver;
characterizing the first signal path from the first signal that is received;
modifying settings on the feed switch and the receive switch;
injecting a second signal through the first element, the first cable, the multiport switch, the second cable, and the feed switch into a feed coupled to an array element via a coupler;
receiving the second signal from the array element through a second signal path including the feed and the receiver switch;
characterizing the second signal path based on the received second signal;
subtracting at least some of the characteristics of the first path from calibration signals injected into the array element; and
deriving phase and amplitude correction constants from the calibration signal measurements.
2. The method according to claim 1 , further including sending information for the phase and amplitude correction constants to phase shifters and/or transmit/receive modules via a beam steering module.
3. The method according to claim 1 , wherein at least some of the characteristics comprise substantially half of the relative phase and loss of the calibration paths.
4. The method according to claim 1 , wherein the characteristics include phase and amplitude.
5. The method according to claim 1 , wherein the array elements form part of a phased array radar.
6. The method according to claim 1 , wherein calibration is independent of the length of the first and second cables.
7. The method according to claim 1 , wherein the first element comprises a circulator.
8. The method according to claim 1 , wherein the receiver performs digital beamforming.
9. The method according to claim 1 , further including performing in-field calibration for a deployed phased array radar system.
10. The method according to claim 1 , further including performing calibration immediately after the step of deriving phase and amplitude correction constants from the calibration signal measurements.
11. An article, comprising:
a non-transitory computer-readable storage medium containing stored instructions that enable a computer to:
subtract at least some of the characteristics of a first path from calibration signals injected into an array element; and
derive phase and amplitude correction constants from the calibration signal measurements,
after:
injecting a first signal through the first signal path including a first element, a first cable, a multiport switch, a second cable, and a feed switch;
setting the feed switch to have a connection to ground prior to injecting the first signal;
receiving the first signal reflected from ground through the feed switch, the second cable, the multiport switch, the first cable, the first element, and a receive switch for reception by a receiver;
measuring characteristics of the first signal received by the receiver;
characterizing the first signal path from the first signal that is received;
modifying settings on the feed switch and the receive switch;
injecting a second signal through the first element, the first cable, the multiport switch, the second cable, and the feed switch into a feed coupled to an array element via a coupler;
receiving the second signal from the array element through a second signal path including the feed and the receiver switch; and
characterizing the second signal path based on the received second signal.
12. The article according to claim 11 , further including instructions for sending information for the phase and amplitude correction constants to phase shifters and/or transmit/receive modules via a beam steering module.
13. The article according to claim 11 , wherein at least some of the characteristics comprise substantially half of the relative phase and loss of the calibration paths.
14. The article according to claim 11 , wherein the characteristics include phase and amplitude.
15. The article according to claim 11 , wherein the array elements form part of a phased array radar.
16. The article according to claim 11 , wherein calibration is independent of the length of the first and second cables.
17. The article according to claim 11 , wherein the first element comprises a circulator.
18. The article according to claim 11 , wherein the receiver performs digital beamforming.
19. The article according to claim 11 , further including performing in-field calibration for a deployed phased array radar system.
20. A radar system, comprising:
a calibration system including a multiport switch, a RF switch, and a feed switch; and
a feed coupled to array elements;
a processor coupled to a memory, the processor and memory configured to:
inject a first signal through a first signal path including a first element, a first cable, the multiport switch, a second cable, and the feed switch;
set the feed switch to have a connection to ground prior to injecting the first signal;
receive the first signal reflected from ground through the feed switch, the second cable, the multiport switch, the first cable, the first element, and a receive switch for reception by a receiver;
measure characteristics of the first signal received by the receiver;
characterize the first signal path from the first signal that is received;
modify settings on the feed switch and the receive switch;
inject a second signal through the first element, the first cable, the multiport switch, the second cable, and the feed switch into a feed coupled to an array element via a coupler;
receive the second signal from the array element through a second signal path including the feed and the receiver switch;
characterize the second signal path based on the received second signal; and
subtract at least some of the characteristics of the first path from calibration signals injected into the array element; and
derive phase and amplitude correction constants from the calibration signal measurements.