Silicon photonics receive phased array sensors
High-performance ultra-wideband Phased Array Sensors (PAS) are disclosed, which have unique capabilities, enabled through photonic integrated circuits and novel optical architectures. Unique capabilities for a Receive PAS are provided by wafer scale photonic integration including heterogeneous integration of III-V materials and ultra-low-loss silicon nitride waveguides, combining key component technologies into complex PIC devices. Novel aspects include optical multiplexing combining wavelength division multiplexing and/or a novel extension to array photodetectors providing the capability to combine many RF photonic signals with very low loss. The architecture also includes optical down-conversion, as well as digital signal processing to improve the linearity of the system. Simultaneous multi-channel beamforming is achieved through optical power splitting of optical signals to create multiple exact replicas of the signals that are then processed independently.
1. A channelizer system, comprising:
an array of N antenna receiving elements, where N≥1, that receive a free space radio frequency (RF) signal; the RF signal being a mixture of RF signals coming from all directions;
wherein each of the receiving elements converts the received RF signal into an antenna element electrical signal;
a single photonic integrated circuit (PIC), including:
N optical modulators configured to receive optical carriers from N lasers, the N modulators modulate the optical carriers with the antenna element electrical signal received from a corresponding one of the antenna elements;
wherein all output optical signals from the N modulators pass through a series of Y tunable filters; each filter in the series of tunable filters selects a frequency band for down-conversion, and passes a remaining modulated signal along to a next filter in the series of tunable filters;
wherein a signal from each of the filters passes through a corresponding time delay (TD) element, each of the TD elements imparting an individual time delay;
wherein the TD elements are followed by amplitude controllers that apply individual attenuations; each output of each of the amplitude controllers is combined in one of a set of Y couplers with a local oscillator signal from one of a set of Y local oscillators (LOs);
wherein output signals from each of the set of LOs pass through a phase and amplitude control device prior to entering the one of the set of Y couplers;
wherein, via a digital signal processor, all filters, bands, time delays, phase delays, and attenuations are selected to collectively provide from the free space RF signal only a RF signal band with chosen beam forming parameters; and
wherein output optical signals from one of the set of Y couplers, and corresponding couplers from all other N antenna receiving elements, are combined in a combiner comprising at least one photodetector, said combiner outputting a single electrical output, the amplitude and phase of which comprise information about the RF signal band with chosen beam forming parameters received by the N antenna receiving elements.
2. The system of claim 1 , wherein the tunable filters are tunable in a center frequency.
3. The system of claim 1 , wherein the tunable filters are tunable in a bandwidth.
4. The system of claim 1 , wherein the tunable filters are tunable in a center frequency and a bandwidth.
5. The system of claim 1 , wherein the number of tunable filters, Y, is one;
and wherein via a digital signal processor the tunable filter and corresponding local oscillator frequency are tuned within a bandwidth of the system.
6. The system of claim 1 , wherein the number of tunable filters, Y, is greater than one;
and wherein via a digital signal processor the tunable filters and corresponding local oscillator frequencies are tuned within a bandwidth of the system.
7. The system of claim 1 , wherein the number of filters, Y, is equal to a system bandwidth divided by a filter bandwidth, and the filters and associated local oscillators are fixed in frequency and not tunable, each filter selecting a different frequency band for down-conversion.
8. The system of claim 1 , wherein different LOs for each of the N antenna receiving elements comprise a local oscillator laser, said local oscillator laser being frequency-locked to a corresponding one of the N lasers.
9. The system of claim 1 , further comprising N splitters receiving the optical carriers from the N lasers thus forming N signal channels plus N·Y local oscillator channels; each of the N optical modulators receiving optical inputs in each signal channel;
further comprising N·Y different local oscillator modulators receiving optical inputs in the LO channels;
wherein each of the N·Y different local oscillator modulators modulate the optical carrier in the local oscillator channel with a local oscillator RF signal.
10. The system of claim 9 , where optical power levels after the N splitters are increased through inclusion of a semiconductor optical amplifier (SOA) before a corresponding modulator.
11. The system of claim 1 , wherein the beam forming parameters include a direction defined by polar and azimuthal receiving angles.
12. The system of claim 11 , wherein the beam forming parameters include a selected angular spread of the received RF signal.
13. The system of claim 1 , wherein the beam forming parameters include a selected angular spread of the received RF signal.
14. The system of claim 1 , wherein the output signals from the N modulators and N LO modulators are each split into M identical copies of the output signals and LO signals using an optical power splitter, wherein M≥2, the M copies being used to simultaneously provide M independent RF output signals, each RF output signal having independently chosen beam forming parameters by selecting appropriate time delays and attenuations.
15. The system of claim 1 , wherein the combiner is an array of photodetectors.
16. The system of claim 15 , wherein the array of photodetectors forms a line of groups of photodetectors; each group including 2 or more photodetectors directly connected to each other; and each group being connected to a next group via an inductor to create an artificial transmission line; forming a Group Array Photodetector Combiner (GAPC) device.
17. The system of claim 1 , wherein each of the N lasers generates radiation with a wavelength, λ N , being different from wavelengths of all other lasers; and the combiner comprises one or more wavelength division multiplexing (WDM) combiners; the WDM combiner being followed by a Group Array Photodetector Combiner (GAPC) device; the GAPC device combining outputs of multiple WDM combiners.
18. The system of claim 1 , wherein each of the N lasers have different wavelengths, and the combiner is a wavelength division multiplexer followed by a single balanced photodetector.
19. The system of claim 1 , wherein the system has an antenna with a single receiving element, where N=1.
20. The system of claim 1 , wherein the system has an array of N input RF signals, where N≥1; the RF signals being a mixture of RF signals coming from all directions; the N modulators modulate the optical carriers with the corresponding N input RF signals.