Patent ID: 11888520
Assignee: RAYTHEON BBN TECHNOLOGIES CORP.
Field: Telecommunications (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 18:
19. A photonic radio frequency (RF) signal correlator comprising:
a photonic integrated circuit (PIC) comprising:
a first optical waveguide configured to receive a laser light signal from a continuous wave (CW) laser source modulated with a first radio frequency signal to form a first RF modulated optical signal S1(t), wherein t is time;
a first 1 to M optical splitter having an input coupled to the first optical waveguide and M outputs, the first 1 to M optical splitter configured to receive S1(t) at the input and divide the signal S1(t) to provide a signal S1′(t) at the M outputs to form M first RF modulated optical signals S1′(t), wherein each of the M first RF modulated optical signal signals S1′(t) have substantially equal power, wherein M is a positive integer greater than 1;
M discrete optical delay lines coupled to the M outputs of the first 1-to-M optical splitter, wherein the M discrete optical delay lines each provide a separate delay from 0×Δτ to (M−1) Δτ respectively to provide M different delayed first RF modulated optical signals S1′(t), S1′(t−Δτ), . . . S1′(t−(M−1) Δτ), where 1/Δτ is more than twice a bandwidth of the first RF signal;
a second optical waveguide configured to receive a laser light signal of the CW laser source modulated with a second radio frequency signal to form a second RF modulated optical signal S2(t);
a second 1-to-M optical splitter having an input coupled to the second optical waveguide and M outputs, the second 1 to M optical splitter configured to receive the modulated optical signal S2(t) at the input and divide the signal S2(t) to provide a signal S2′(t) at the M outputs to form M second RF modulated optical signals, wherein each of the M second RF modulated optical signal signals S2′(t) have substantially equal power;
M optical balanced couplers of index m having a first input, second input, first output and second output, where m=0 to M−1, the Mth optical balanced coupler configured to receive and combine the mth different delayed first RF modulated optical signal S1′(t−mΔτ) and one of the m second RF modulated signal S2′(t) to output m first coupled RF modulated optical signals and m second coupled RF modulated optical signals; and
M balanced photodetectors coupled to the M optical balanced couplers, wherein the Mth balanced photodetector is configured to receive the mth first coupled RF modulated optical signal and the mth second coupled RF modulated optical signal from the Mth optical balanced coupler and output M signals proportional to a correlation integrated weight coefficient; and

a processor electrically coupled to the output of the M balanced photodetectors, the processor configured to receive and sum the M electrical signals to output a frequency domain correlated signal of the first RF signal and the second RF signal.