Extension of dynamic range of emitter and detector circuits of spread spectrum-based antenna test range

• US 6,184,826 B1
• Filed: 04/20/1999
• Issued: 02/06/2001
• Est. Priority Date: 04/20/1999
• Status: Active Grant

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Boritzki, Daniel L., Killen, William D., Zeitfuss, Michael P., Walley, George M.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/294,940
• Time in Patent Office: 658 Days
• Field of Search: 342/360, 375/146, 375/140
• US Class Current: 342/360
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

An antenna test range uses a direct spread-spectrum based test signal to effectively electronically reject all unwanted signals that may be present in the test range, and thereby allow both main beam and off-axis performance of the antenna to be completely and accurately measured. For increased dynamic range, the test signal comprises a carrier signal that is sequentially modulated with low rate, respectively different, direct spreading PN sequences applied to a cascaded plurality of N mixer stages through successive ones of which the carrier signal is coupled. The plurality of PN spreading sequences are mutually offset in time by a fraction of a chip, and thereby produce, at an output of an Nth mixer stage, a direct sequence spread spectrum carrier signal having its energy spread out over a bandwidth that is N times the spreading bandwidth of an individual one of the PN spreading sequences.

Claims

1. A method for extending the dynamic range of a process for testing one or more characteristics of an antenna, wherein a spread spectrum carrier is emitted as a test signal from a test signal source and is incident upon said antenna, and a replica of a spreading sequence of said spread spectrum test signal is correlated with a signal demodulated from energy received at said antenna, so as to extract energy in said test signal and exclude energy in unwanted signals that may be incident upon said antenna, said extracted test signal energy being processed to derive a measure of said one or more characteristics of said antenna, said method comprising the steps of:

(a) coupling said carrier signal through successive ones of a cascaded arrangement of a plurality of N mixer stages;

(b) applying, to said successive ones of said plurality of N mixer stages, respectively different, relatively low rate, PN spreading sequences, that are mutually offset in time by a fraction of a chip, thereby producing, at an output of an Nth mixer stage of said plurality of N mixer stages, a direct sequence spread spectrum carrier having its energy spread out over a bandwidth that is N times the spreading bandwidth of an individual one of said PN spreading sequences; and

(c) emitting the spread spectrum carrier produced in step (b) as said test signal from said test signal source.

2. A method according to claim 1, wherein step (c) comprises emitting said test signal from said test signal source at a plurality of spaced apart signal source locations having respectively different azimuth and elevation parameters relative to the boresight of said antenna.

3. An antenna test range comprising:

a test signal source, spaced apart from an antenna under test and being operative to emit a test signal that is incident upon said antenna under test, said test signal source including a cascaded arrangement of a plurality of N mixer stages through successive ones of which a carrier signal is coupled, and a direct spreading PN generator that is operative to couple a plurality of different, relatively low rate, PN spreading sequences, that are mutually offset in time by a fraction of a chip, to respective ones of said plurality of N mixer stages, and thereby produce, at an output of an Nth mixer stage of said plurality of N mixer stages, a direct sequence spread spectrum carrier signal as said test signal having its energy spread out over a bandwidth that is N times the spreading bandwidth of an individual one of said PN spreading sequences;

a receiver coupled to said antenna under test, and being operative to demodulate a signal received by said antenna under test, and to correlate a replica of said PN spreading sequences of said test signal with the demodulated signal so as to extract energy in said test signal and exclude energy in unwanted signals that may be incident upon said antenna under test; and

a signal processor, coupled to said receiver, and being operative to process the test signal energy extracted by said receiver and derive a measure of one or more characteristics of said antenna under test.

4. An antenna test range according to claim 3, wherein said test signal source is operative to emit said test signal from a plurality of spaced apart signal source locations having respectively different azimuth and elevation parameters relative to the boresight of said antenna under test.

5. A method of spreading a carrier signal with a direct spreading PN sequence comprising the steps of:

(a) coupling said carrier signal through successive ones of a cascaded arrangement of a plurality of N mixer stages; and

(b) applying, to said successive ones of said plurality of N mixer stages, respectively different, relatively low rate, PN spreading sequences, that are mutually offset in time by a fraction of a chip, thereby producing, at an output of an Nth mixer stage of said plurality of N mixer stages, a direct sequence spread spectrum carrier having its energy spread out over a bandwidth that is N times the spreading bandwidth of an individual one of said PN spreading sequences.

6. A method according to claim 5, further including the steps of:

(c) emitting said direct sequence spread spectrum carrier from an antenna range test signal source located at a plurality of spaced apart signal source locations having respectively different azimuth and elevation parameters relative to the boresight of an antenna; and

(d) receiving and demodulating signals received by said antenna;

(e) correlating a replica of said test signal with signals received and demodulated in step (d), so as to extract energy in said test signal and exclude energy in unwanted signals that may be incident upon said antenna; and

(f) processing test signal energy extracted in step (e) to derive a measure of said one or more characteristics of said antenna.

7. An apparatus for spreading a carrier signal with a direct spreading PN sequence comprising a cascaded plurality of N mixer stages through successive ones of which a carrier signal is coupled, and a direct spreading PN generator that is operative to couple a plurality of different, relatively low rate, PN spreading sequences, that are mutually offset in time by a fraction of a chip, to respective ones of said plurality of N mixer stages, and thereby produce, at an output of an Nth mixer stage of said plurality of N mixer stages, a direct sequence spread spectrum carrier signal having its energy spread out over a bandwidth that is N times the spreading bandwidth of an individual one of said PN spreading sequences.

8. An apparatus according to claim 7, further comprising an antenna range test signal source, spaced apart from an antenna under test and being operative to emit, as a test signal that is incident upon said antenna under test, said direct sequence spread spectrum carrier signal, a receiver coupled to said antenna under test and being operative to demodulate a signal received by said antenna under test, and to correlate a replica of said PN spreading sequences of said test signal with the demodulated signal so as to extract energy in said test signal and exclude energy in unwanted signals that may be incident upon said antenna under test, and a signal processor, coupled to said receiver, and being operative to process the test signal energy extracted by said receiver and derive a measure of one or more characteristics of said antenna under test.

9. An apparatus according to claim 8, wherein said test signal source is operative to emit said test signal from a plurality of spaced apart signal source locations having respectively different azimuth and elevation parameters relative to the boresight of said antenna under test.