US 10,649,067 B1Granted

Simultaneous transmit and receive (STAR) subsystem with external noise canceller

AssigneeNorthrop Grumman Systems Corporation

InventorsJeffrey M. Yang, Eric B. Nakamura, A. Dale Parker

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Abstract

A wideband simultaneous transmit and receive (STAR) subsystem for a radar or communications system including self-interference cancellation and external noise cancellation. The STAR subsystem includes a canceller circuit which digitally prepares a cancellation signal to cancel out leaked or reflected portions of the transmit signal and correlated noise in the receiver signal. The self-interference cancellation can be adaptively configured in a closed-loop mode, and operated open loop in real time to minimize bandwidth limitations and achieve wideband performance. The STAR subsystem also includes an external noise active canceller which greatly diminishes high-power external noise in the receiver signal. The external noise canceller digitally synthesizes a cancellation signal which dramatically improves the signal-to-noise ratio in the receiver. Together, the combined cancellation techniques prevent receiver saturation and preserve receiver sensitivity.

Claims20

Dependent claims

A simultaneous transmit and receive (STAR) system with self-cancellation of transmit signal interference and external noise cancellation, said system comprising:

an antenna aperture;
a transmitter circuit for transmitting signals over a frequency band through the antenna aperture;
a receiver circuit for receiving signals from the antenna aperture, where the receiver circuit uses the same frequency band as the transmitter circuit at the same time;
a circulator for directing transmit signals from the transmitter circuit to the antenna aperture and a received signal from the antenna aperture to the receiver circuit;
a transmit signal self-canceller circuit including a plurality of tuners that operate on the transmit signals and digitally synthesize a self-cancellation signal which is applied to the received signal, where the self-cancellation signal cancels out components which are present in the received signal due to antenna reflection and circulator leakage of the transmit signals and correlated noise, and where the plurality of tuners include true time delay tuners which apply a true time delay to a leakage component and a reflection component of each of one or more digital transmit signals, and amplitude tuners which apply an amplitude scale factor to the leakage component and the reflection component of each of the digital transmit signals;
and
an external noise canceller circuit including a signal processor which applies a 180 degree phase offset to a digitized form of the received signal to synthesize a noise cancellation signal which is converted to analog and applied to the received signal, where the noise cancellation signal decreases external noise power in the received signal.

4 more elements

A radio receiver system with external noise cancellation, said receiver system comprising:

an external noise canceller circuit including a first coupler which splits a received signal from an antenna into a first path and a second path, where the first path includes a signal processor which applies a 180-degree phase offset to a digitized form of the received signal to synthesize a noise cancellation signal, and a second coupler which injects the noise cancellation signal into a time-delayed form of the received signal from the second path to produce a modified received signal;
and
a receiver circuit which receives the modified received signal from the external noise canceller circuit, said receiver circuit including a low noise amplifier, a radio frequency to intermediate frequency (RF-IF) down-converter, an IF amplifier, and an analog-to-digital converter (ADC), where the receiver circuit provides a digital receiver output signal.

A method for cancelling interference in a simultaneous transmit and receive (STAR) system, said method comprising:

providing one or more digital transmit signals to a transmitter circuit;
creating, by the transmitter circuit, an analog transmit signal for transmission from the digital transmit signals;
providing the analog transmit signal to a phased array antenna via a circulator;
preparing, in a self-canceller circuit, a self-cancellation signal from the digital transmit signals, including applying a true time delay to a leakage component and a reflection component of each of the digital transmit signals, applying an amplitude scale factor to the leakage component and the reflection component of each of the digital transmit signals, and summing the leakage components and the reflection components after the true time delays and the amplitude scale factors have been applied;
receiving a primary received signal from the antenna via the circulator;
combining the self-cancellation signal with the primary received signal into a secondary received signal;
preparing, in an external noise canceller circuit, a noise cancellation signal by applying a 180 degree phase offset to a digitized form of the secondary received signal;
combining the noise cancellation signal with the secondary received signal to produce a tertiary received signal, where the noise cancellation signal decreases external noise power in the tertiary received signal;
and
cancelling, in a receiver circuit, leaked and reflected components of uncorrelated transmit signal noise from the tertiary received signal to create a final received signal.

7 more elements

Dependencies are inferred from the claim text.