Cancellation of interference and harmonics

1. A system for mitigating interference from an interference signal, wherein the system comprises cancellation circuitry configured to:

receive a first signal from a first antenna, the first signal comprising an interference component deriving from the interference signal and a desired component deriving from a desired signal;

receive a second signal comprising an interference component deriving from the interference signal and received at one or more of a different antenna or a different frequency to the first signal, wherein the interference component in the second signal is stronger than the interference component in the first signal;

derive a cancellation signal from the second signal;

generate an output signal by subtracting the cancellation signal from the first signal to substantially remove the interference component from the first signal; and

output the output signal,

wherein:

the interference signal is a pulsed interference signal comprising a series of pulses of interference;

the system is configured to detect when a pulse of interference is received; and

the cancellation circuitry is configured to subtract the cancellation signal from the input signal only during each pulse.

2. The system of claim 1 wherein deriving the cancellation signal comprises generating a cancellation signal based on the second signal and adjusting one or more of:

an amplitude of the cancellation signal to match an amplitude of the interference component of the first signal; or

a phase of the cancellation signal to match a phase of the interference component of the first signal.

3. The system of claim 2 wherein the cancellation circuitry is further configured to:

identify when a source of interference in the first signal changes based on a change to the interference component of the first signal; and

in response to said identification, adjust one or more of:

the amplitude of the cancellation signal to match an updated amplitude of the interference component of the first signal; or

a phase of the cancellation signal to match an updated phase of the interference component of the first signal.

4. The system of claim 1 wherein the second signal is obtained via a second antenna, the second signal comprises a desired component deriving from the desired signal and the system is configured to, in response to the desired component of the first signal falling below one or more of a predefined threshold or a predefined level relative to the desired component of the second signal, output a pulse blanked version of the second signal.

5. The system of claim 1 wherein the first signal is obtained via a first antenna element of the first antenna, the second signal is obtained via a first antenna element of a second antenna, wherein each of the first and second antennas comprises a plurality of antenna elements, and wherein the first antenna element of the first antenna has the same polarisation as the first antenna element of the second antenna.

6. The system of claim 5 wherein the cancellation circuitry is further configured to, for each antenna element in the first antenna:

receive, from the respective antenna element in the first antenna, a corresponding signal comprising an interference component deriving from the interference signal and a desired component deriving from a corresponding desired signal;

receive, from each antenna element in the second antenna that shares the same polarisation as the respective antenna element of the first antenna, a respective signal comprising an interference component deriving from the interference signal;

derive a corresponding cancellation signal for the respective antenna of the first antenna based on the respective signal from each antenna element in the second antenna that shares the same polarisation as the respective antenna element of the first antenna;

generate a corresponding output signal by subtracting the corresponding cancellation signal from the corresponding signal to substantially remove the interference component from the corresponding signal; and

output the corresponding output signal.

7. The system of claim 1 wherein the system is configured to choose the second signal from a set of signals, each comprising a corresponding interference component deriving from the interference signal, wherein the second signal is chosen as the signal from the set of signals that has the strongest interference component.

8. The system of claim 1 wherein the output signal is generated by subtracting the cancellation signal from the first signal in response to a determination that the strength of the interference component of the first signal is greater than a predefined threshold interference strength.

9. The system of claim 1 further comprising a first filter configured to pass the first signal at a first frequency and a second filter configured to pass the second signal at a second frequency that is different to the first frequency.

10. The system of claim 9 wherein the first and second signals are received at the first antenna and passed to the first and second filters.

11. The system of claim 9 wherein the first and second frequencies are different harmonic frequencies of the interference signal.

12. The system of claim 11 wherein the second frequency is a fundamental frequency of the interference signal and the first frequency is a higher harmonic frequency than the fundamental frequency.

13. The system of claim 9 wherein deriving the cancellation signal from the second signal comprises generating a replica interference signal at the first frequency based on the second signal.

14. A method for mitigating interference from an interference signal, the method comprising cancellation circuitry:

receiving a first signal from a first antenna, the first signal comprising an interference component deriving from the interference signal and a desired component deriving from a desired signal;

receiving a second signal comprising an interference component deriving from the interference signal and received at one or more of a different antenna or a different frequency to the first signal, wherein the interference component in the second signal is stronger than the interference component in the first signal;

deriving a cancellation signal from the second signal;

generating an output signal by subtracting the cancellation signal from the input signal to substantially remove the interference component from the first signal; and

outputting the output signal,

wherein:

the interference signal is a pulsed interference signal comprising a series of pulses of interference;

the method further comprises detecting when a pulse of interference is received; and

the cancellation circuitry subtracts the cancellation signal from the input signal only during each pulse.

15. A system for mitigating interference from an interference signal, wherein the system comprises cancellation circuitry configured to:

receive a first signal from a first antenna, the first signal comprising an interference component deriving from the interference signal and a desired component deriving from a desired signal;

receive a second signal comprising an interference component deriving from the interference signal and received at one or more of a different antenna or a different frequency to the first signal, wherein the interference component in the second signal is stronger than the interference component in the first signal;

derive a cancellation signal from the second signal;

generate an output signal by subtracting the cancellation signal from the first signal to substantially remove the interference component from the first signal; and

output the output signal,

wherein the first signal is obtained via a first antenna element of the first antenna, the second signal is obtained via a first antenna element of a second antenna, wherein each of the first and second antennas comprises a plurality of antenna elements, and wherein the first antenna element of the first antenna has the same polarisation as the first antenna element of the second antenna,

wherein the cancellation circuitry is further configured to, for each antenna element in the first antenna:

receive, from the respective antenna element in the first antenna, a corresponding signal comprising an interference component deriving from the interference signal and a desired component deriving from a corresponding desired signal;

receive, from each antenna element in the second antenna that shares the same polarisation as the respective antenna element of the first antenna, a respective signal comprising an interference component deriving from the interference signal;

derive a corresponding cancellation signal for the respective antenna of the first antenna based on the respective signal from each antenna element in the second antenna that shares the same polarisation as the respective antenna element of the first antenna;

generate a corresponding output signal by subtracting the corresponding cancellation signal from the corresponding signal to substantially remove the interference component from the corresponding signal; and

output the corresponding output signal.