US-12627330-B2 - Simultaneous transmit and receive through active cancellation

Abstract

A simultaneous transmit and receive (STAR) system comprises a plurality of radiating elements and a plurality of antenna transmit/receive (T/R) elements. The plurality of antenna T/R elements are each in operable communication with a respective radiating element. Each T/R element comprises a transmit channel, a receive channel, a switch, and a directional coupler. The directional coupler comprises an RF input in operable communication with an antenna array receiving signals, an RF output coupling the received signals to an input of the receive channel, and a coupled input operably coupled to the switch. If the switch is set to a predetermined state, the respective transmit channel couples an active cancellation signal to the coupled input of the directional coupler to cancel at least some coupling effects arising on an input to the receive channel, arising from operation of at least some of the T/R elements in the array.

Inventors

• Zachary Dunn

Assignees

• RAYTHEON COMPANY

Dates

Publication Date

20260512

Application Date

20230502

Claims (20)

1. 1 . A simultaneous transmit and receive (STAR) system, comprising: a plurality of radiating elements configured as part of an antenna array, the antenna array configured for transmitting signals and for receiving signals; and a plurality of antenna transmit/receive (T/R) elements, each respective T/R element being in operable communication with a respective radiating element, each respective T/R element comprising a transmit channel, a receive channel, a switch, and a directional coupler, wherein, for each respective T/R element: the directional coupler comprises a radiofrequency (RF) input in operable communication with the antenna array to receive a signal received by the antenna array, an RF output configured to couple the received signal to an input of the receive channel, and a coupled input in operable communication with the switch; and when the switch is set to a first predetermined state, the transmit channel is configured to couple an active cancellation signal to the coupled input of the directional coupler, the active cancellation signal configured to cancel at least some coupling effects that arise on an input to the receive channel, the coupling effects arising from operation of at least a portion of the plurality of T/R elements.
2. 2 . The STAR system of claim 1 , wherein, for each respective T/R element, the active cancellation signal is configured to enable the input to the receive channel to be as close a match as possible to the signal received by the antenna array.
3. 3 . The STAR system of claim 1 , wherein: a transmit channel input of at least a first T/R element of the plurality of T/R elements is configured to receive the respective active cancellation signal at substantially a same time that at least a second T/R element of the plurality of T/R elements is configured to receive a transmit signal to be provided to the respective radiating element of the second T/R element; and the respective active cancellation signal at the first T/R element is configured to cancel at least one coupling effect that appears at the first T/R element and that is caused by the second T/R element.
4. 4 . The STAR system of claim 1 , wherein: the antenna array further comprises transmit and receive channels; and the active cancellation signal for each respective T/R element is based at least in part on a coupling matrix for the antenna array and on at least one characterization of at least one of the transmit channels and the receive channels of the antenna array.
5. 5 . The STAR system of claim 1 , wherein: the active cancellation signal for each respective T/R element is based at least in part on one or more parameters out of a set of parameters measured and determined during a calibration of the antenna array; and the set of parameters comprises a maximum delay necessary to fully characterize signal coupling in the antenna array, a receive element number, a transmit element number, one or more characterized feedback paths, one or more characterized coupling matrix values, knowledge of an antenna array channel's characterization, knowledge of a commanded excitation for each antenna element at a given time sample, and one or more antenna array channel transmit output signals.
6. 6 . The STAR system of claim 1 , wherein, for each respective T/R element, the first predetermined state comprises a feedback state configured to couple an output of the transmit channel to the coupled input of the directional coupler.
7. 7 . The STAR system of claim 1 , wherein, for each respective T/R element, when the switch is set to a second predetermined state, an output of the transmit channel is coupled to the respective radiating element.
8. 8 . The STAR system of claim 1 , wherein: a first subset of T/R elements are configured to have their respective switches set to the first predetermined state; and the first predetermined state comprises, for each of the first subset of T/R elements, a feedback state configured to couple an output of the transmit channel to the coupled input of the directional coupler.
9. 9 . The STAR system of claim 8 , wherein a second subset of T/R elements are configured to have their respective switches set to a second predetermined state in which, for each of the second subset of T/R elements, an output of the transmit channel is coupled to the respective radiating element.
10. 10 . The STAR system of claim 1 , wherein, for each respective T/R element: the switch comprises an input in operable communication with an output of the transmit channel, a transmit pole in operable communication with the respective radiating element, and a feedback pole in operable communication with the coupled input of the directional coupler; wherein the switch is set to the transmit pole, the output of the transmit channel is provided to the respective radiating element; and wherein the switch is set to the feedback pole, the output of the transmit channel is provided to the coupled input of the directional coupler.
11. 11 . A simultaneous transmit and receive (STAR) system, comprising: a plurality of radiating elements configured as part of an antenna array, the antenna array configured for transmitting signals and for receiving signals; and a plurality of antenna transmit/receive (T/R) elements, each respective T/R element being in operable communication with a respective radiating element, each respective T/R element comprising a first transmit channel, a second transmit channel independent of the first transmit channel, a receive channel, and a directional coupler, wherein, for each respective T/R element: the first transmit channel has an input configured to receive a signal to be transmitted and an output configured to operably couple the signal to be transmitted to the respective radiating element; the second transmit channel has an input configured to receive an active cancellation signal and an output configured to operably couple the active cancellation signal to the directional coupler; the directional coupler comprises a radiofrequency (RF) input in operable communication with the antenna array to receive a signal received by the antenna array, an RF output configured to couple the received signal to an input of the receive channel, and a coupled input in operable communication with the output of the second transmit channel; and the active cancellation signal is configured to cancel at least some coupling effects that arise on an input to the receive channel, the coupling effects arising from operation of at least a portion of the plurality of T/R elements.
12. 12 . The STAR system of claim 11 , wherein, for each respective T/R element, the active cancellation signal is configured to enable the input to the receive channel to be as close a match as possible to the signal received by the antenna array.
13. 13 . The STAR system of claim 11 , wherein, for each respective T/R element, the input of the second transmit channel is configured to receive the active cancellation signal at substantially a same time that the first transmit channel is configured to receive the signal to be transmitted.
14. 14 . The STAR system of claim 11 , wherein: the input of the second transmit channel of a first T/R element of the plurality of T/R elements is configured to receive the active cancellation signal at substantially a same time that the input of the first transmit channel of any respective T/R element of the plurality of T/R elements is configured to receive a transmit signal to be provided to the respective T/R element's respective radiating element; and the active cancellation signal at the first T/R element is configured to cancel at least one coupling effect that appears at the first T/R element and that is caused by the respective T/R element.
15. 15 . The STAR system of claim 11 , wherein: the antenna array further comprises transmit channels and receive channels; and the active cancellation signal for each respective T/R element is based at least in part on a coupling matrix for the antenna array and on at least one characterization of at least one of the transmit channels and the receive channels of the antenna array.
16. 16 . The STAR system of claim 11 , wherein: the active cancellation signal for each respective T/R element is based at least in part on one or more parameters out of a set of parameters measured and determined during a calibration of the antenna array; and the set of parameters comprises a maximum delay necessary to fully characterize signal coupling in the antenna array, a receive element number, a transmit element number, one or more characterized feedback paths, one or more characterized coupling matrix values, knowledge of an antenna array channel's characterization, knowledge of a commanded excitation for each antenna element at a given time sample, and one or more antenna array channel transmit output signals.
17. 17 . A method for simultaneous transmit and receive (STAR) operation, comprising: operating a system comprising (i) a plurality of radiating elements configured as part of an antenna array, the antenna array configured for transmitting signals and for receiving signals, and (ii) a plurality of antenna transmit/receive (T/R) elements coupled to be in operable communication with the plurality of radiating elements, wherein: each respective T/R element is in operable communication with a respective radiating element; each respective T/R element comprises a first transmit channel, a receive channel, a switch, and a directional coupler; and for each respective T/R element: the directional coupler comprises a radiofrequency (RF) input in operable communication with the antenna array to receive signals received by the antenna array, an RF output configured to couple the received signals to an input of the receive channel, and a coupled input in operable communication with the switch; and the switch comprises an input in operable communication with an output of the first transmit channel, a transmit pole in operable communication with the respective radiating element, and a feedback pole in operable communication with the coupled input of the directional coupler; setting, for at least a first T/R element of the plurality of T/R elements, the switch of the first T/R element to the transmit pole to cause an output of the first transmit channel of the first T/R element to be provided to the respective radiating element for the first T/R element; setting, for at least a second of the plurality of T/R elements, the switch of the second T/R element to the feedback pole to cause an output of the first transmit channel of the second T/R element to be provided to the coupled input of the directional coupler; providing a transmit signal to an input of the first transmit channel of the first T/R element, wherein the first T/R element provides the transmit signal to its respective radiating element to be radiated into a target area; receiving, at the antenna array, a received signal that is provided to an input of the receive channel of the second T/R element; and providing an active cancellation signal to an input of the first transmit channel of the second T/R element, wherein the directional coupler of the second T/R element is configured to provide the active cancellation signal to the input of the receive channel of the second T/R element, wherein the active cancellation signal is configured to cancel at least some coupling effects that arise on the input to the receive channel of the second T/R element, the coupling effects arising from providing the transmit signal to the first T/R element, and wherein the active cancellation signal is configured to enable the input to the receive channel to be as close a match as possible to the received signal.
18. 18 . The method of claim 17 , wherein the active cancellation signal is provided as an input to the first transmit channel of the second T/R element at substantially a same time that the transmit signal is provided as an input to the first transmit channel of the first T/R element.
19. 19 . The method of claim 17 , wherein: the antenna array further comprises transmit channels and receive channels; and the active cancellation signal is generated based at least in part on one or more of: a coupling matrix for the antenna array; at least one characterization of at least one of the transmit channels and the receive channels of the antenna array; and one or more parameters out of a set of parameters measured and determined during a calibration of the antenna array, the set of parameters comprising a maximum delay necessary to fully characterize signal coupling in the antenna array, a receive element number, a transmit element number, one or more characterized feedback paths, one or more characterized coupling matrix values, knowledge of an antenna array channel's characterization, knowledge of a commanded excitation for each antenna element at a given time sample, and one or more antenna array channel transmit output signals.
20. 20 . The method of claim 17 , wherein: each respective T/R element further comprises a second transmit channel having an input configured to receive the active cancellation signal and an output configured to couple the active cancellation signal to the directional coupler; and the method further comprises: receiving, at the input of the second transmit channel of the first T/R element, the active cancellation signal, wherein the active cancellation signal is received at substantially a same time that the transmit signal is provided to the input of the first transmit channel of the first T/R element; and configuring the active cancellation signal to cancel at least one coupling effect that appears at the first T/R element and that is caused by any other T/R element.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/338,938, filed May 6, 2022, and entitled “Simultaneous Transmit and Receive Through Active Cancellation,” which is incorporated herein by reference in its entirety. FIELD Embodiments of the disclosure generally relate to devices, systems, and methods for transmitting and receiving electromagnetic waves. More particularly, the disclosure describes embodiments relating to devices, systems, and methods for transmitting and receiving simultaneously, such as in a radar system. BACKGROUND In various commercial or military systems that transmit and receive electromagnetic waves, such as communications systems or radar systems, it may be useful to transmit and receive simultaneously. This operation is known in the art as simultaneous transmit and receive (STAR) (also known in the art as same-frequency transmit and receive) or in-band full-duplex (IBFD)). STAR is becoming an area of increasing interest, especially for applications such as radars, communications, spectral sensing, etc. Transmitting and receiving at the same frequency is one way to optimize use of available bandwidth (e.g., doubling spectrum efficiency) and increase network throughput, which can be advantageous especially in defense systems. SUMMARY The following presents a simplified summary in order to provide a basic understanding of one or more aspects of the embodiments described herein. This summary is not an extensive overview of all of the possible embodiments and is neither intended to identify key or critical elements of the embodiments, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present some concepts of the embodiments described herein in a simplified form as a prelude to the more detailed description that is presented later. The ability for an antenna system and/or radar system to operate in STAR mode opens many possible applications and solutions that are otherwise impossible on a non-STAR capable system. However, in STAR systems, transmitting and receiving at the same frequency can present challenges, due to coupling of the transmitted signal into the receiver, and other types of in-band self-interference (SI), such as leakage, which can interfere with receiver operation, such as interfering with a receive signal that is weaker than the interfering transmitted signal. Various techniques are used in some STAR implementations to help provide ways to mitigate transmit-to-receive coupling and other types of self-interference. One factor hindering STAR operation is the antenna's transmit signal coupling back and compressing the receive signal path, removing most or all of the receiver's dynamic range. Effectively, in some instances STAR can create a self-jamming issue for the receiver. For example, FIG. 1 is a simplified block diagram 100 of a prior art digital array architecture, showing a plurality of transmit channels 102a, 102b, 102c, 102d and a plurality of receive channels 103a, 104b, 104c, 104d, that together form a plurality of respective transmit and receive (T/R) elements 105a, 105b, 105c, 105d. The T/R elements 105 produce transmit signals 122a, 1222c, 122d. Each T/R element 105 is coupled through a respective isolating element 108 (e.g., a circulator), to a respective radiating element 110. For simplicity, other known components in the transmit and receive path, such as low noise amplifiers (LNAs), power amplifiers (PAs), filters, mixers, oscillators, and the like, are not shown in FIG. 1, but will be well understood by those of skill in the art. Antenna transmit signals, especially in STAR systems, tend to couple and reflect back and compress their own receive signal paths. Consider T/R element 105b in FIG. 1. The receiver channel 104b of T/R element 105b receives an isolation path transmit signal 126, as well as the received signal 120 from the target area. As noted above, the received signal 120 often is weaker than the transmitted signal (e.g., 80-100 dB or more below the transmitted signal), but it can be difficult to provide enough isolation via isolation element 108b to prevent the transmitted signal from appearing stronger in the receiver channel 104 than the desired received signal. It can be necessary to have >100 dB isolation between Tx and Rx channels to achieve true STAR/IBFD operation, and this has been challenging to achieve in practice. Such transmitter interference can exceed the receiver's dynamic range by orders of magnitude, leading to issues that decrease dynamic range and sensitivity of the receiver, including problems such as intermodulation distortion (IMD), gain compression, and increased noise figure. In addition, it can be challenging to have enough isolation to deal with transmitter interference with high power array antennas, where transmitters may be operating near saturation, resulting in distortion and noise that may leak to the receiver. Furthe