RANDOMLY PHASE CODED ANTENNA TECHNIQUE FOR SEARCH RADAR

• US 3,680,100 A
• Filed: 12/15/1970
• Issued: 07/25/1972
• Est. Priority Date: 12/15/1970
• Status: Expired due to Term

• Current Assignee: Hermann H. Woerrlein
• Original Assignee: Hermann H. Woerrlein
• Inventors: Woerrlein, Hermann H.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/098,248
• Time in Patent Office: 588 Days
• Field of Search: 343/10,11R,16R,18E,1SA,1CL
• US Class Current: 342/13
• CPC Class Codes: G01S 13/106 using transmission of pulses having some particular characteristics G01S13/12, G01S13/22, G01S13/24, G01S13/26, G01S13/28 and G01S13/30 take precedence
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 2013/0281 LPI, Low Probability of Intercept radar
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H01Q 3/40 with phasing matrix

Abstract

A search radar having an array antenna wherein the individual antenna array elements are energized by random phases having a beam forming matrix to sense direction dependent phase codes in the antenna far field, which phase codes are in turn used in correlation processing in the radar receiver for the purpose of obtaining angular resolution and radar sensitivity.

Claims

1. A method of detecting a target by radar, comprising the steps of:

energizing a plurality of antenna elements so that each element radiates energy at substantially the same frequency as the other of said plurality of elements but at a phase which is controlled by a random or pseudo random process, said plurality of antenna elements thereby producing a total far field radiation pattern which is randomly changing, in time and in space, and which is substantially free of predominate lobes;

synthesizing a multiplicity of signals which are representative of the directionally phase coded complex far field radiated by said plurality of antenna elements;

receiving energy reflected by one or more targets in said far field radiated pattern and resolving the return from said targets at certain angles from all other returns by correlation processing, namely by correlating the received signals with the multiplicity of synthesized signals whereby a successful correlation of reflected signals with synthesized signals is indicative of the presence and direction of said targets in said far field pattern.

2. A '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar systEm comprising:

antenna means for radiating energy to form a far field pattern that is directionally phase coded and randomly changing, in time and in space, and which is substantially free of predominate lobes;

beam forming matrix means connected to said antenna means and having a plurality of outputs and functioning to produce signals at said plurality of outputs which are alternately representative of said radiated complex far field, the signals of individual outputs of said plurality of outputs being related to different directions from said antenna means and range resolution and correlation processing means connected to each of said plurality of outputs and functioning to provide a signal informative of the presence, range, and angular coordinates of a target when correlation occurs between the signals representative of the radiated far field pattern and of the received radar signal.

3. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 2 wherein said radiated energy is varied in pulse repetition frequency and also because said far field pattern is substantially free of predominate lobes, the personnel on said targets are more likely to regard said '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar surveillance as being noise or jamming.

4. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 2 wherein said range resolution and correlation processing means includes a switching means, a storage device having a multiplicity of output taps and a multiplicity of correlation mixers connected to said multiplicity of output taps, said switching means being controlled to connect each of said plurality of outputs to said storage device when said antenna means is radiating energy and to connect each of said plurality of outputs to said multiplicity of correlation mixers when said antenna means is not radiating energy.

5. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 4 wherein said antenna means includes a plurality of array antenna elements, each element of which is connected through a transmit-receive (TR) means to a source of energy.

6. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 5 wherein said TR means has an output which is connected to said beam forming matrix means and functions to connect said antenna elements to said beam forming matrix when said antenna is not radiating energy and to pass to said beam forming matrix a small portion of the energy passing through said TR means when said antenna is radiating energy.

7. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 6 which further includes signal processing means which are connected to the outputs of said multiplicity of correlation mixers and functions to improve the signal-to-noise ratio of said signal informative of the presence, range, and angular coordinates of a target.

8. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 7 which further includes a display and record section connected to said signal processing means.

9. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 8 wherein said beam forming matrix means includes a Butler beam forming matrix.

10. A '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar system comprising:

antenna means for radiating energy to form a far field pattern that is directionally phase coded and randomly changing, in time and in space, and which is substantially free of predominate lobes;

beam forming matrix means connected to said antenna means and functioning to sense the directionally phased coding of said far field pattern;

range resolution and correlation processing means connected to said beam forming matrix means and functioning to provide range resolution by sensing the time when correlation occurs, and to provide angular resolution due to the multiplicity of correlation processing channels implemented for different directions.

11. The '"'"''"'"''"'"''"'"'silent'"'"''"'"''"'"''"'"' radar of claim 10 and further including a display section means connected to said range resolution and correlation processing means and functioning to present a display representative of said provided directional and range resolutions.