Calibration in a phased array system
A system comprises a plurality of antenna elements, a transmitter circuit, and first and second receiver circuits. The transmitter is operable to: transmit, via a first antenna element, a series of signals having a calibration component and each of the signals being generated with a different configuration of the transmitter circuit; and select a configuration for a future transmission based on a signal metric. The first receiver circuit is operable to: receive the signal via a second antenna element; and detect the calibration component in the signal to generate a first calibration signal. The second receiver circuit is operable to: receive the signal via a third antenna element; detect the calibration component in the signal to generate a second calibration signal; combine the first and second calibration signals to generate a combined calibration signal; and generate the signal metric based on the combined calibration signal.
1. A system comprising:
a phased-array comprising a plurality of antenna elements, a transmitter circuit, a first receiver circuit, and a second receiver circuit, wherein:
the transmitter circuit is operable to:
transmit, via a first of the antenna elements, a series of signals, each signal of the signals having a calibration component and each of the signals being generated with a different one of a plurality of configurations of the transmitter circuit; and
select one of the configurations for a future transmission based on a signal metric;
the first receiver circuit is operable to:
receive a first received version of the signal via a second of the antenna elements; and
detect the calibration component in the first received version of the signal to generate a first calibration signal;
the second receiver circuit is operable to:
receive a second received version of the signal via a third of the antenna elements;
detect the calibration component in the second received version of the signal to generate a second calibration signal;
combine the first calibration signal and the second calibration signal to generate a combined calibration signal; and
generate the signal metric based on the combined calibration signal.
2. The system of claim 1 , wherein each one of the signals is generated by:
a first modulation of a carrier wave by a data signal to generate an intermediate signal; and
a second modulation of the intermediate signal by a calibration signal.
3. The system of claim 1 , wherein the transmitter circuit is operable to decide to add the calibration component to the series of signals in response to a detected condition.
4. The system of claim 3 , wherein the detected condition is an alert from a receiver that an error rate has exceeded a threshold.
5. The system of claim 1 , wherein each of the configurations corresponds to a different set of phase and/or amplitude coefficients used by the transmitter circuit.
6. The system of claim 5 , wherein the phase and/or amplitude coefficients control the phase and/or amplitude of local oscillator signals generated in the transmitter circuit.
7. The system of claim 6 , wherein the local oscillators signals are part of a circulator circuit that couples the transmitter circuit to the first of the antenna elements.
8. The system of claim 1 , wherein:
the first receiver circuit is configured to apply first beamforming coefficients to the first received version of the signal before performance of the detection; and
the second receiver circuit is configured to apply second beamforming coefficients to the second received version of the signal before performance of the detection;
the first beamforming coefficients are different than the second beamforming coefficients.
9. The system of claim 1 , wherein:
the first receiver circuit and the second receiver circuit reside on different integrated circuits;
the first receiver circuit is operable to send the first calibration signal to the second receiver circuit via a data bus; and
the second receiver circuit is operable to receive the first calibration signal via a data bus.
10. The system of claim 1 , wherein the metric is a measure of leakage of transmit-band signals leaking into a receive band.
11. A method comprising:
transmitting, by a transmitter circuit via a first antenna element of a phased-array of antenna elements, a series of signals, each signal of the signals having a calibration component and each of the signals being generated with a different one of a plurality of configurations of the transmitter circuit;
for each signal of the series of signals:
receiving a first received version of the signal via a second antenna element of the phased-array and a second received version of the signal via a third antenna element of the phased array;
detecting, by a first receiver circuit, the calibration component in the first received version of the signal to generate a first calibration signal;
detecting, by a second receiver circuit, the calibration component in the second received version of the signal to generate a second calibration signal;
combining the first calibration signal and the second calibration signal to generate a combined calibration signal; and
measuring a metric of the combined calibration signal; and
selecting one of the configurations for future transmissions by the transmitter circuit, wherein the selecting is based on the measured metric.
12. The method of claim 11 , comprising generating each one of the signals by:
modulating a carrier wave by a data signal to generate an intermediate signal; and
modulating the intermediate signal by a calibration signal.
13. The method of claim 11 , comprising deciding, by the transmitter circuit, to add the calibration component to the series of signals in response to a detected condition.
14. The method of claim 13 , wherein the detected condition is an alert from a receiver that an error rate has exceeded a threshold.
15. The method of claim 11 , wherein each of the configurations corresponds to a different set of phase and/or amplitude coefficients applied used by the transmitter circuit.
16. The method of claim 15 , wherein the phase and/or amplitude coefficients control the phase and/or amplitude of local oscillator signals generated in the transmitter circuit.
17. The method of claim 16 , wherein the local oscillators signals are part of a circulator circuit that couples the transmitter circuit to the first of the antenna elements.
18. The method of claim 11 , wherein:
the first receiver circuit applies first beamforming coefficients to the first received version of the signal before performing the detecting; and
the second receiver circuit applies second beamforming coefficients to the second received version of the signal before performing the detecting;
the first beamforming coefficients are different than the second beamforming coefficients.
19. The method of claim 11 , wherein:
the first receiver circuit and the second receiver circuit reside on different integrated circuits;
the combining is performed by the second receiver circuit; and
the method comprises the first receiver circuit sending the first calibration signal to the second receiver circuit via a data bus.
20. The method of claim 11 , wherein the metric is a measure of leakage of transmit-band signals leaking into a receive band.