Frequency-shifted feedback cavity used as a phased array antenna controller and carrier interference multiple access spread-spectrum transmitter
View Patent ↗An optical processor for controlling a phased antenna array uses a frequency-shifted feedback cavity (FSFC), which includes a traveling-wave cavity. The FSFC incrementally delays and incrementally frequency shifts optical signals circulating in the traveling-wave cavity. Optical signals coupled out of the FSFC are separated by frequency, hence by delay, and processed to control either or both transmit and receive beam-forming operations. The FSFC provides a receiver with multiple receive signals which have incremental values of frequency. Each frequency corresponds to an incremental time sampling of optical signals input into the FSFC. Transmit signals coupled out of the FSFC have frequency and phase relationships that result in short time-domain pulses when combined. Controlling modulation and frequency of the transmit signals achieves carrier interference multiple access, a new type of spread-spectrum communications.
1. An apparatus comprising:
a multicarrier-signal generator to receive an information-modulated electromagnetic signal and to generate an electromagnetic information-modulated multicarrier signal therefrom, the electromagnetic information-modulated multicarrier signal having a plurality of electromagnetic information-modulated frequency modes, and
a carrier-frequency selector configured to isolate at least one of the electromagnetic information-modulated frequency modes.
2. A method comprising:
accepting at least one modulation signal, and
generating a modulated multicarrier signal having a plurality of frequencies, said generating comprising:
modulating the at least one modulation signal onto a multicarrier signal to obtain a modulated intermediate signal, and
filtering the modulated intermediate signal to obtain at least one of the plurality of frequencies within at least one predetermined frequency band.
3. A method comprising:
generating at least one periodic signal having a plurality of incrementally spaced-in-frequency component signals, at least one spaced-in-frequency component signal being within a desired frequency band, the at least one periodic signal having an amplitude that is a function of an input signal; and
coupling the at least one periodic signal to a communication channel.
4. A method comprising:
generating a plurality of electromagnetic carrier signals having a plurality of frequencies; and
combining the electromagnetic carrier signals to generate a composite signal;
wherein the composite signal has an envelope signal modulating a composite signal carrier signal having a composite carrier frequency that is a function of the plurality of frequencies.
5. The method of claim 4 , wherein each of said electromagnetic carrier signals has an amplitude that is a function of an information signal.
6. The method of claim 4 , wherein the envelope signal is a function of an information signal.
7. The method of claim 4 , wherein the plurality of frequencies are within at least one predefined frequency window, and wherein the electromagnetic carrier signals are modulated by a baseband information signal.
8. The method of claim 4 , wherein said combining comprises:
phase-locking the electromagnetic carrier signals to produce orthogonal interference, wherein the electromagnetic carrier signals constructively add to create an interference information signal having a predetermined pulse width occurring at one or more predetermined time intervals.
9. The method of claim 8 , wherein said phase-locking is controlled by a baseband information signal to modulate the electromagnetic carrier signals.
10. The method of claim 8 , further comprising:
modulating the electromagnetic carrier signals by a baseband information signal using pulse-amplitude modulation applied to the plurality of electromagnetic carrier signals, wherein the pulse-amplitude modulation has a pulse width that is longer than the pulse width of the interference information signal.
11. The method of claim 8 , further comprising:
modulating the electromagnetic carrier signals with respect to a predetermined pseudorandom code signal using phase-shift keying of the electromagnetic carrier signals within a phase-shift key time interval equal to the pulse width of the interference information signal.
12. The method of claim 8 , wherein said generating the plurality of electromagnetic carrier signals comprises:
providing for a plurality of groups of discrete carrier frequencies, each group having a predetermined number of discrete carrier frequencies, a spacing between the discrete carrier frequencies in each of the groups determining a repetition rate of the interference information signal, the number of discrete carrier frequencies in the groups determining the pulse width of interference information signals, each interference information signal comprising a number of sub-pulses determined by spacing between groups of discrete carrier frequencies, and wherein the sub-pulses have sub-pulse widths determined by a number of groups of discrete carrier frequencies.
13. The method of claim 8 , wherein said generating the plurality of electromagnetic carrier signals comprises:
tapering a frequency-versus-amplitude window of a carrier signal amplitude distribution to reduce time-domain sidelobe energy of the interference information signal.
14. The method of claim 4 , wherein the electromagnetic carrier signals comprise one or more broadband continuous-frequency signals.
15. The method of claim 4 , wherein the electromagnetic carrier signals have discrete frequencies.
16. The method of claim 15 , wherein the discrete frequencies are incrementally separated in frequency.
17. The method of claim 4 , wherein the electromagnetic carrier signals have predetermined frequencies to allow for frequency separation of the electromagnetic carrier signals with respect to other carrier signals.
18. The method of claim 4 , wherein said generating the plurality of electromagnetic carrier signals comprises:
frequency-dithering the electromagnetic carrier signals, wherein an amount of frequency dithering is substantially uniform in frequency variation with respect to time.
19. The method of claim 4 , wherein said generating the plurality of electromagnetic carrier signals comprises:
time-offsetting the electromagnetic carrier signals.
20. The method of claim 4 , wherein the electromagnetic carrier signals are optical carrier signals, the method further comprising converting the optical carrier signals to RF carrier signals.
21. A carrier interferometry multiple access (CIMA) transmitter, comprising:
a signal generator to generate a plurality of electromagnetic carrier signals having a plurality of frequencies; and
a combiner to combine the electromagnetic carrier signals to generate a combined signal that includes an envelope signal modulating a combined carrier signal having a combined carrier frequency that is a function of the plurality of frequencies.
22. The CIMA transmitter of claim 21 , wherein each of said electromagnetic carrier signals has an amplitude that is a function of an information signal.
23. The CIMA transmitter of claim 21 , wherein the envelope signal is a function of an information signal.
24. The CIMA transmitter of claim 21 , further comprising:
a transmission unit to transmit combined carrier signal over a communication channel.
25. The CIMA transmitter of claim 24 , wherein the transmission unit comprises:
an antenna array.