METHOD AND APPARATUS FOR PROVIDING RADIO FREQUENCY PHOTONIC FILTERING

• US 20130202305A1
• Filed: 02/02/2012
• Published: 08/08/2013
• Est. Priority Date: 02/02/2012
• Status: Active Grant

• Current Assignee: The United States Government As Represented By The Secretary Of The Army
• Original Assignee: The United States Government As Represented By The Secretary Of The Army
• Inventors: Zhou, Weimin
• Granted Patent: US 9,097,790 B2
• Time in Patent Office: Days
• US Class Current: 398/115
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: H04B 2210/006 Devices for generating or processing an RF signal by optical means

Abstract

A method and apparatus for providing RF-photonic filtering link. Specifically, one embodiment is an apparatus comprising a radio frequency (RF)-photonic filter for filtering an RF signal, where the RF-photonic filter comprises a loop comprising an electro-optical modulator, an optical fiber, a photo detector. Another embodiment is a method of operating an RF-photonic filter comprising applying a reference signal to the RF-photonic filter; selecting a reference frequency for the RF-photonic filter upon the RF-photonic filter locking to the reference frequency, disconnecting the reference signal; and applying an RF input signal to the RF-photonic filter to lock the RF input signal to the RF-photonic filter.

Claims

1. An apparatus comprising:

a RF-photonic filter for filtering an RF signal, wherein the RF-photonic filter comprises a loop comprising an electro-optical modulator, an optical fiber, at least two photo detectors, a tunable phase shifter, and frequency/phase locking circuit.

2. The apparatus of claim 1 wherein the RF-photonic filter further comprises:

a reference lock module in the frequency/phase locking circuit for tuning and locking the filter to a reference signal; and

a signal lock module for locking the filter to the RF signal.

3. The apparatus of claim 2 wherein the reference lock module comprises a phase locked loop circuit for resonating the filter at a reference frequency.

4. The apparatus of claim 2 wherein a frequency of the reference signal and the frequency of the RF signal are substantially similar.

5. The apparatus of claim 1 wherein the optical fiber has a predetermined length to establish a particular Q for the filter.

6. The apparatus of claim 1 wherein the loop comprises a fiber splitter providing a second RF output to enable remote processing of the input signal after passing through the filter.

7. The apparatus of claim 1 wherein the loop supports a single RF mode.

8. The apparatus of claim 1 wherein the loop comprises an RF combiner for combining the RF input signal with a filtered RF input signal.

9. A method of operating an RF-photonic filter comprising:

applying a reference signal, using a tunable RF signal source, to the RF-photonic filter;

selecting a reference frequency for the RF-photonic filter;

upon the RF-photonic filter locking to the reference frequency, disconnecting the reference signal; and

applying an RF input signal to the RF-photonic filter to lock the RF Input signal to the RF-photonic filter.

10. The method of claim 9 wherein selecting comprises tuning the RF-photonic filter to a particular operating frequency.

11. A radio frequency signal processing system comprising:

an RF-photonic filter for filtering an RF signal, where the RF-photonic filter has a loop comprising an electro-optical modulator, an optical fiber, a photo detector;

a frequency converter, coupled to the RF-photonic filter, for converting the RF signal after filtering to an intermediate frequency signal;

a signal processor, coupled to the frequency converter, for extracting information from the intermediate frequency signal.

12. The system of claim 11 wherein the RF-photonic filter further comprises a fiber splitter to couple an optical representation of an RF signal to a second photo detector via an optical cable.

13. The system of claim 12 wherein the second photo detector converts the optical signal to a second RF signal for remotely transporting the RF signal.