Semi-active phased array antenna

• US 5,027,125 A
• Filed: 08/16/1989
• Issued: 06/25/1991
• Est. Priority Date: 08/16/1989
• Status: Expired due to Fees

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Tang, Raymond
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Hellner, Mark
• Application Number:
  US07/394,467
• Time in Patent Office: 678 Days
• Field of Search: 342/368, 342/374, 330/289
• US Class Current: 342/368
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
• CPC Class Codes: H01Q 3/34 by electrical means active lenses or reflecting arrays H01Q3/46

Abstract

A module disposed at each radiating element of a phased array antenna, the module having a limiter, a low-noise amplifier and a phase shifter. One embodiment includes a DPDT switch to permit use of a common phase shifter on transmit and receive. On transmit, the DPDT switch is thrown in a position that connects the phase shifter directly to the radiating element. On receive, the DPDT switch is thrown in a position that connects the radiating element through the limiter and low noise amplifier and then to the phase shifter. Another embodiment uses a four-port circulator in place of the DPDT switch, and uses separate phase shifters for transmit and receive. A semi-active module for a constrained feed array uses both a DPDT switch and a circulator and uses a common transmit/receive phase shifter. A semi-active module for a space-fed array uses two DPDT switches, a single phase-shifter and limiter/low-noise amplifier and two antenna elements; one of receive, and one for retransmit. Another module employs a four-port circulator, separate transmit and receive phase shifters, and separate transmit and receive beamforming networks. In a monopulse radar transmitter, a module using a four-port circulator and a separate receive diode phase shifter, limiter and low-noise amplifier is used with a receive monopulse feed, transmit ferrite phase shifters and a transmit series feed.

Claims

1. A semi-active phased array antenna having individual semi-active modules disposed adjacent individual antenna elements for selectively interconnecting the antenna elements with a single transmit/receive feed line in a first mode on transmit and in a second mode on receive, said modules comprising:

a receive circuit internal to said module including a limiter and a low noise amplifier;

a phase shifter disposed within said module;

a single transmit/receive feed line connected to one end of said phase shifter; and

switch means in said module connected to the other end of said phase shifter and connected to its associated antenna element and arranged to selectively switch between said first and second modes, said switch means connecting its associated antenna element to said feed line by way of said phase shifter on transmit, said switch means connecting its associated antenna element to said feed line by way of said receive circuit and said phase shifter on receive;

whereby said phase shifter is included in the circuit from said antenna element to said transmit/receive feed line both on transmit and receive, and whereby said limiter and said low noise amplifier are bypassed on transmit.

2. The semi-active module of claim 1 in which said switch means comprises a DPDT switch.

3. The semi-active module of claim 1 in which said switch means comprises a ferrite circulator.

4. The semi-active module of claim 1 in which said switch means comprises an arrangement including a DPDT switch and a ferrite circulator.

5. The semi-active phased array antenna of claim 1 further comprising a plurality of ferrite circulator duplexers coupled to the transmit/receive feed line of each of said modules.

6. The semi-active phased array antenna of claim 5 further comprising a plurality of high-power transmitter amplifiers.

7. A semi-active phased array antenna having individual semi-active modules disposed adjacent individual antenna elements, said semi-active modules comprising:

a receive circuit internal to said module including a limiter and a low noise amplifier and a receive phase shifter, said receive phase shifter having an output connected to a receive beamforming network;

a transmit phase shifter having an input connected to a feed and an output;

switch means in said module comprising a four-port circulator, said four-port circulator being directly connected to the output of said transmit phase shifter and arranged to selectively switch between said receive circuit in a receive mode and said transmit phase shifter in a transmit mode, said four-port circulator coupling its associated antenna element to said feed by way of said transmit phase shifter on transmit, said four-port circulator coupling its associated antenna element to said receive beamforming network by way of said receive circuit on receive.

8. The semi-active phased array antenna of claim 7 wherein the feed comprises a transmit beamforming network.

9. The semi-active phased array antenna of claim 7 wherein said receive beamforming network comprises a monopulse feed and said feed comprises a transmit series feed having a ferrite phase shifter.

20. The semi-active phased array antenna of claim 7 wherein the feed comprises a subarray feed.

23. The semi-active phased array antenna of claim 7 wherein the feed comprises a transmit beamforming network.

24. The semi-active phased array antenna of claim 7 wherein said receive beamforming network comprises a monopulse feed and said feed comprises a transmit series feed having a ferrite phase shifter.

10. A semi-active phased array antenna, including antenna elements and associated phase shifters adapted to provide high power in transmit mode and low noise figure in receive mode comprising:

a plurality of high-power transmitter amplifiers;

a plurality of duplexers, each duplexer being associated with a subarray of said antenna elements for switching each individual subarray from an individual one of said high-power transmitter amplifiers to a signal receive terminal;

a plurality of receive paths, including limiters and low noise amplifiers; and

a plurality of T/R switches having a transmit state and a receive state, said switches being coupled to said antenna elements, to said phase shifters, and to said receive paths such that in the receive state, said antenna elements are coupled to said receive terminal via a receive path, a phase shifter and a duplexer, and in the transmit state, said antenna elements are coupled directly to a high-power transmitter amplifier via a phase shifter and a duplexer.

11. The semi-active phased array antenna of claim 10 in which said T/R switches are double-pole-double-throw switches.

12. The semi-active phased array antenna of claim 11 in which said double-pole-double-throw switch has a first switch pole connected to one of said antenna elements, said first switch pole being adapted for switching from a first switch terminal to a second switch terminal, said double-pole-double-throw switch having a second switch pole for switching from said second switch terminal to said first switch terminal;

said receive path having the input of said limiter connected to the first switch terminal of said first switch pole, said receive path having the output of the low-noise amplifier connected to said second switch pole, said second switch terminal being connected to one terminal of said phase shifter, the other terminal of said phase shifter being connected to its associated duplexer.

13. The semi-active phase array antenna of claim 12 in which said duplexers comprise ferrite circulators.

14. A semi-active phased array antenna using four-port circulators to provide high power in transmit mode and low noise figure in receive mode, said semi-active phased array antenna comprising:

a plurality of four-port circulators;

a plurality of transmit phase shifters having an output connected to a first port of said circulators;

a plurality of antenna elements connected to a second port of said circulators;

a plurality of receiver limiters having an input connected to a third port of said circulators;

a plurality of matched load terminations connected to a fourth port of said circulators;

a plurality of low-noise amplifiers having an input connected to the output of said limiters;

a plurality of receive phase shifters connected to the output of said amplifiers;

a receive beamforming network connected to the output of each of said receive phase shifters for combining the output received signals into a received beam;

a plurality of high-power transmitter amplifiers; and

a plurality of subarray feeds, each being connected to an individual one of said transmitter amplifiers, and each of said subarray feeds being connected to the input of different groups of said transmit phase shifters.

15. The semi-active phased array antenna of claim 14 in which said four-port circulators comprise three three-port circulators connected together to function as a four-port circulator.

16. The semi-active phased array antenna of claim 14 in which said high-power transmitter amplifiers comprise traveling wave tube amplifiers.

17. The semi-active phased array antenna of claim 14 in which said high-power transmitter amplifiers comprise high-power solid state amplifiers.

18. Apparatus for coupling an antenna element of a constrained feed phased array antenna to a transmit/receive feed while providing enhanced isolation between transmit and receive, said apparatus comprising:

a semi-active module having a transmit/receive input/output terminal, and having an antenna element input/output terminal;

a double-pole-double-throw switch disposed in said module and having a first switch pole connected to said antenna element input/output terminal, said first switch pole being adapted for switching from a first switch terminal to a second switch terminal;

said double-pole-double-throw switch having a second switch pole for switching from said second switch terminal to said first switch terminal;

a receiver limiter disposed in said module and having an input connected to said second switch terminal;

a receiver low noise amplifier disposed in said module and having an input connected to the output of said limiter;

a three-port ferrite circulator disposed in said module and having a first port connected to said second switch pole, said circulator having a second port connected to the output of said amplifier;

a matched load termination disposed in said module and connected to a third port of said circulator; and

a phase shifter disposed in said module and connected from said first switch terminal to said transmit/receive input/output terminal,

whereby an operative semi-active phased array antenna is formed by coupling a plurality of said antenna elements to a transmit/receive feed through a plurality of said semi-active modules.

19. A semi-active module arrangement for a space-fed antenna array comprising:

a semi-active module having first and second antenna element terminals;

first and second DPDT switches disposed in said module, each having a first switch pole for switching from a first switch terminal to a second switch terminal, and each having a second switch pole for switching from said second switch terminal to said first switch terminal;

said first DPDT switch having its first switch pole connected to said first antenna element terminal;

said second DPDT switch having its first switch pole connected to said second antenna element terminal;

a phase shifter disposed in said module and being connected between the second switch terminal of said first DPDT switch and the first switch terminal of said second DPDT switch;

a receiver limiter disposed in said module and having an input connected to the second switch terminal of said second DPDT switch; and

a receiver low noise amplifier disposed in said module and having an input connected to the output of said limiter, and having its output connected to the second switch pole of said first DPDT switch;

the second switch pole of said second DPDT switch being connected to the first switch terminal of said first DPDT switch;

whereby a signal entering said second antenna element terminal is switched to pass through said limiter, said amplifier and said phase shifter and is conducted to said first antenna element terminal.

21. A semi-active phased array antenna having individual semi-active modules disposed adjacent individual antenna elements, said semi-active modules comprising:

a receive circuit internal to said module including a limiter and a low noise amplifier and a receive phase shifter, said receive phase shifter having an output connected to a receive beamforming network, wherein said receive beamforming network comprises a monopulse feed and said feed comprises a transmit series feed having a ferrite phase shifter;

a transmit phase shifter having an input connected to a feed;

switch means in said module comprising a four-port circulator, said four-port circulator connected to said transmit phase shifter and arranged to selectively switch between said receive circuit in a receive mode and said transmit phase shifter in a transmit mode, said four-port circulator coupling its associated antenna element to said feed by way of said transmit phase shifter on transmit, said four-port circulator coupling its associated antenna element to said receive beamforming network by way of said receive circuit on receive.

22. The semi-active phased array antenna of claim 21 wherein the feed comprises a subarray feed.