Patent ID: 7999624

Claim:
A source of radiation having a circuit for controlling respective output phases of a plurality of VCOs comprising: a first oscillator for providing a reference signal having a phase; at least first and second phase shifters coupled to said first oscillator, said first phase shifter being arranged for phase shifting said reference signal and transmitting a first phase shifted reference signal, and said second phase shifter being arranged for phase shifting said reference signal and transmitting a second phase shifted reference signal; at least first and second phase locked loops, said first phase locked loop having a first VCO for outputting a first signal, and said second phase locked loop having a second VCO for outputting a second signal; wherein said first phase locked loop is coupled to said first phase shifter, and said second phase locked loop is coupled to said second phase shifter; whereby in use said first signal output by said first VCO is phase locked to said first phase shifted reference signal and said second signal output by said second VCO is phase locked to said second phase shifted reference signal; and whereby the phases of said first and second signals are controlled by said first and second phase shifted reference signals to be different from each other.