Optoelectronic wide bandwidth photonic beamsteering phased array

• US 5,051,754 A
• Filed: 08/15/1990
• Issued: 09/24/1991
• Est. Priority Date: 08/15/1990
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Newberg, Irwin L.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): SWANN, TOD R
• Application Number:
  US07/567,848
• Time in Patent Office: 405 Days
• Field of Search: 342/368, 342/371, 342/372, 342/373, 342/374, 342/375, 342/377, 342/53, 342/54
• US Class Current: 342/375
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• CPC Class Codes: G01S 7/03 Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
• CPC Class Codes: H01Q 3/2676 Optically controlled phased array

Abstract

A transmit/receive circuit for each of the antenna elements of a radar phased array including an optical fiber true time delay circuit responsive to an electrical RF signal for providing an optical signal having a controlled time delay, an optical fiber for propagating the time delay controlled optical signal, an optical detector circuit responsive to the propagated time delay controlled optical signal for providing a time delay controlled electrical signal, transmit circuitry responsive to the time delay controlled electrical signal for providing to the associated antenna element a transmit signal based on the time delay controlled electrical signal, and receive circuitry responsive to the time delay controlled electrical signal and the signal received by the associated antenna element. A first RF switch selectively couples the time delay controlled electrical signal to the transmit circuit during transmit times, and to the receive circuit during receive times; and a second RF switch couples the associated antenna element to the transmit circuit during transmit times, and to the receive circuit during receive times. The receive circuit further includes analog-to-digital conversion circuitry whose sample timing is controlled so as to provide for the time alignment of the received signal relative to the received signals of the other transmit/receive circuits of the phased array. Alternatively, such time alignment is provided pursuant to processing of the sampled receive signals from the transmit/receive circuits of the phased array.

Claims

1. In a phased array radar system having a radar processor and a plurality of antenna elements, a transmit/receive circuit for each of the antenna elements comprising:

an optical fiber true time delay circuit responsive to an electrical RF signal for providing an optical signal having a controlled time delay relative to the outputs of the optical fiber true time delay circuits of the other transmit/receive circuits in the array;

optical means for propagating said true time delay controlled optical signal;

optical detection means responsive to the propagated true time delay controlled optical signal for providing a true time delay controlled electrical signal;

transmit means responsive to said true time delay controlled electrical signal for providing a transmit signal based on said true time delay controlled electrical signal to the associated antenna element;

receive means responsive to said true time delay controlled electrical signal and the signal received by the associated antenna element for providing a baseband received signal, said true time delay controlled electrical signal being utilized as the local oscillator signal to provide the correct phase for steering the array;

true time delay processing means responsive to said baseband received signal for providing a digital received signal that is properly aligned relative to the digital received signals provided by the receive means of the other transmit/receive circuits of the array;

first switching means for coupling said true time delay controlled electrical signal to said transmit means during transmit times, and to said receive means during receive times; and

second switching means for coupling the associated antenna element to said transmit means during transmit times, and to said receive means during receive times.

2. The transmit/receive circuit of claim 1 wherein said true time delay processing means includes:

analog to digital conversion means for sampling said baseband received signal; and

sample timing control means for controlling the sample timing of said analog to digital conversion means relative to the sample timing of the other transmit/receive circuits in the array.

3. The transmit/receive circuit of claim 2 wherein said sample timing control means comprises a fiber optic true time delay circuit.

4. The transmit/receive circuit of claim 1 wherein said true time delay processing means includes:

analog to digital conversion means for sampling said baseband received signal to provide a sampled receive signal; and

processing means responsive to said sampled receive signal for aligning said sampled receive signal with the sampled receive signals provided by the other transmit/receive circuits of the array.

5. In a phased array radar system having a radar processor and a plurality of antenna elements, a transmit/receive circuit for each of the antenna elements comprising:

an optical fiber true time delay circuit responsive to an electrical RF signal for providing an optical signal having a controlled time delay relative to the outputs of the optical fiber true time delay circuits of the other transmit/receive circuits in the array;

optical means for propagating said true time delay controlled optical signal;

optical detection means responsive to the propagated true time delay controlled optical signal for providing a true time delay controlled electrical signal;

transmit means responsive to said true time delay controlled electrical signal for providing a transmit signal based on said true time delay controlled electrical signal to the associated antenna element;

receive means responsive to said true time delay controlled electrical signal and the signal received by the associated antenna element for providing a baseband received signal, said true time delay controlled electrical signal being utilized as the local oscillator signal to provide the correct phase for steering the array;

analog to digital conversion means responsive to said baseband received signal for providing a digital received signal;

optical means responsive to digital received signal for providing an optical received signal to the radar processor;

first switching means for coupling said true time delay controlled electrical signal to said transmit means during transmit times, and to said receive means during receive times; and

second switching means for coupling the associated antenna element to said transmit means during transmit times, and to said receive means during receive times.

6. The transmit/receive circuit of claim 5 further including sample timing control means for controlling the sample timing of said analog to digital conversion means relative to the sample timing of the other transmit/receive circuits in the array.

7. The transmit/receive circuit of claim 6 wherein said sample timing control means includes a fiber optic true time delay circuit.

8. The transmit/receive circuit of claim 5 further including means responsive to said digital receive signal and to the digital receive signals of the other transmit/receive circuits in the array for providing digital beamforming.

9. In a phased array radar system having a radar processor and a plurality of antenna elements, a transmit/receive circuit for each of the antenna elements comprising:

an optical fiber phase true time delay circuit responsive to an electrical RF signal for providing an optical signal having a controlled time delay relative to the outputs of the optical fiber true time delay circuits of the other transmit/receive circuits in the array;

optical means for propagating said true time delay controlled optical signal;

optical detection means responsive to the propagated true time delay controlled optical signal for providing a true time delay controlled electrical signal;

transmit means responsive to said true time delay controlled electrical signal for providing a transmit signal based on said true time delay controlled electrical signal to the associated antenna element;

receive means responsive to said true time delay controlled electrical signal and the signal received by the associated antenna element for providing a baseband received signal, said true time delay controlled electrical signal being utilized as the local oscillator signal to provide the correct phase for steering the array;

first switching means for coupling said true time delay controlled electrical signal to said transmit means during transmit times, and to said receive means during receive times; and

second switching means for coupling the associated antenna element to said transmit means during transmit times, and to said receive means during receive times.

10. The transmit/receive circuit of claim 9 further including means responsive to said baseband receive signal for providing an optical receive signal to the radar processor.