Method and apparatus for digital signal processing

• US 5,510,799 A
• Filed: 06/08/1993
• Issued: 04/23/1996
• Est. Priority Date: 06/09/1992
• Status: Expired due to Fees

• Current Assignee: Eads Astrium Ltd. (Airbus SE)
• Original Assignee: MMS Space Systems Limited (Airbus SE)
• Inventors: Wishart, Alexander W.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): PHAN, DAO LINDA
• Application Number:
  US08/073,144
• Time in Patent Office: 1,050 Days
• Field of Search: 342/196, 342/81, 342/380, 342/383, 342/382
• US Class Current: 342/373
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence

Abstract

A digital signal processing method and apparatus for beam forming utilizes an N-element phased array antenna (1). For transmit side beam forming of an agile beam to be steered in a direction between three adjacent orthogonal beams three copies of complex envelope samples for the required beam signal are generated, separately weighted in amplitude and phase (4) and fed into an N-part inverse FFT processor (3) via three input ports (7a, 7b and 7c) which correspond to the three adjacent orthogonal beams, and inverse Fast Fourier Transformed therein into the required beam as a weighted combination of the three adjacent orthogonal beams for passage to the elements (2) of the phased array antenna (1). For receive side beam detection of an agile beam received from a direction between three adjacent orthogonal beams, baseband complex envelope samples of signals received on each of the N elements (2) of the antenna (1) are input to the DFT processor (3) and discrete transformed into N orthogonal beam signals, the three orthogonal beam signals (5a, 5b and 5c) output from the processor 3 which correspond to the three orthogonal beams are separately weighted in amplitude and phase at (4) and combined into an output signal (10) which is the baseband complex envelope of the required beam signal.

Claims

1. A mehtod for beam forming N orthogonal beams and in addition at least one agile beam, using N-point Fourier Transform processors and an N-element phased array antenna, and for beam detecting said N orthogonal beams and said at least one agile beam, said mehtod comprising steps of:

transmit side beam forming said at least one agile beam using a first set of at least three of N orthogonal beam signals corresponding to three adjacent ones of said N orthogonal beam signals, comprising steps of;

generating a first set of at least three copies of complex envelope samples of an agile beam signal;

separately weighting, in amplitude and phase, each of said first set of at least three copies of said agile beam signal;

feeding said separately weighted copies of said agile beam signal into an N-point Fast Fourier Transform processor via at least three of N input ports thereof corresponding to said first set of at least three of said N orthogonal beam signals;

performing a Fast Fourier Transform process on said N orthogonal beam signals in said N-point Fast Fourier Transform processor so that said N orthogonal beam signals include said at least one agile beam as a weighted combination of said first set of at least three of said N orthogonal beam signals; and

outputting said Fast Fourier transform processed N orthogonal beam signals including said at least one agile beam at N output ports of said first Fast Fourier Transform processor for driving said N-elements of said N-element phased array antenna;

whereby N orthogonal beams and at least one agile beam are formed using N input ports and N output ports of said N-point Fast Fourier Transform processor; and

receive said beam detecting said first agile beam signal, comprising steps of;

inputting N baseband complex envelope samples of signals received respectively on said N-elements of said N-element phased array antenna to an N-point Discrete Fourier Transform processor;

discrete Fourier transforming said N baseband complex envelope samples into said N-orthogonal beam signals;

outputting said N-orthogonal beam signals at corresponding N output ports of said N-point Discrete Fourier Transform processor;

weighting separately, in amplitude and phase, a copy of each of at least three of said N orthogonal beam signals output from said N-point Discrete Fourier Transform processor for each of said at least one agile beam signal received by said N-element phased array antenna; and

combining said at least three separately weighted N-orthogonal beam signals to form said at least one agile beam signal.

2. A mehtod for beam forming N orthogonal beams and in addition at least one agile beam using according to claim 1, wherein:

said N-point Fast Fourier Transform processor and said N-point Discrete Fourier Transform processor are each one selected form a group comprising a digital signal processor and an analog processor.

3. A method for beam forming N orthogonal beams and in addition at least one agile beam according to claim 1 or claim 2, wherein said steps of transmit side beam forming further comprise the steps of:

generating a second set of at least three copies of a second agile beam signal;

separately weighting, in amplitude and phase, each of said second set of at least three copies of said second agile beam signal; and

summing said second set of at least three copies of said second agile beam signal onto corresponding at least three input ports of said N-point Fast Fourier Transform processor.

4. A method for beam forming N orthogonal beam signals and in addition at least one agile beam signal according to claim 1, wherein:

complex envelope samples of said first set of at least three of said N orthogonal beams are multiplexed directly onto an appropriate at least three of said N input ports of said N-point Fast Fourier Transform processor.

5. A mehtod for beam forming N orthogonal beam signals and in addition at least one agile beam signal according to claim 1, wherein said steps of receive side beam detecting comprise the further step of:

generating a copy of each of said first set of at least three of said N orthogonal beam signals output from said N-point Discrete Fourier Transform processor before said step of weighting separately.

6. A digital signal processing apparatus for transmit side beam forming N orthogonal beams and in addition an agile beam, using an N-point Fourier Transform and an N-element phased array antenna, said apparatus comprising:

means for separately weighting, in amplitude and phase, each of at least three copies of complex envelope samples of at least three of N orthogonal beam signals corresponding to adjacent ones of said N orthogonal beams between which said agile beam is to be steered; and

an N-point Fast Fourier Transform processor having a plurality N of input ports connected respectively to N orthogonal beam signals, and having a plurality N of output ports connectable to respective N-elements of said N-element phased array antenna, said at least three copies of said complex envelope samples being transformed by said N-point Fast Fourier Transform processor into Fast Fourier Transformed samples which are output from respective ones of said plurality N of output ports of said N-point Fast Fourier Transform processor.

7. A digital signal processing apparatus for transmit side beam forming N orthogonal beams and in addition an agile beam according to claim 6, wherein:

said N-point Fast Fourier Transform processor is one selected from a group comprising a digital signal processor and an analog processor.

8. A digital signal processing apparatus for transmit side beam forming N orthogonal beams and in addition an agile beam according to claim 7, further comprising:

means for generating said at least three copies of said complex envelope samples; and

means for summing said at least three separately weighted copies of said complex envelope samples onto corresponding three of said plurality N of input ports of said N-point Fast Fourier Transform processor.

9. A digital signal processing apparatus for transmit side beam forming N orthogonal beams and in addition an agile beam according to claim 6, further comprising

means for summing said at leas three separately weighted copies of said complex envelope samples corresponding to said adjacent ones of said N orthogonal beams onto corresponding ones of said plurality N of input ports of said N-point Fast Fourier Transform processor.

10. A digital signal processing apparatus for receive side beam detection of N orthogonal beams and in addition an agile beam, using an N-point Fourier processor and an N-element phased array antenna, comprising:

an N-point Fast Fourier Transform processor having a plurality N of input ports connected to respective N-elements of said N-element phased array antenna, said N-point Fast Fourier Transform processor Fast Fourier Transforming N orthogonal beam signals corresponding to said N orthogonal beams received by said N-element phased array antenna and outputting said Fast Fourier Transformed N orthogonal beam signals through a corresponding plurality N of output ports of said N-point Fast Fourier Transform processor;

means for separately weighting, in amplitude and phase, at least three of said Fast Fourier Transformed N orthogonal beam signals, so as to detect said agile beam signal from said at least three of said N orthogonal beam signals.

11. A digital signal processing apparatus for transmit side beam forming N orthogonal beams and in addition an agile beam according to claim 10, further comprising:

means for generating a copy of each of said at least three of said N orthogonal beam signals output from said plurality N of output ports of said N-point Fast Fourier Transform processor; and

means for combining said separately weighted copies of each of said at least three of said N orthogonal beam signals into a baseband complex envelope of said agile beam.

12. A digital signal processing apparatus for receive side beam detection of N orthogonal beams and in addition an agile beam according to claim 10, wherein:

said N-point Fast Fourier Transform processor is one selected from a group comprising a digital signal processor and an analog processor.

13. A digital signal processing apparatus for receive side beam detection of N orthogonal beams and in addition an agile beam according to claim 10 or claim 12, further comprising:

means for generating a copy of each of sad at least three adjacent ones of said N orthogonal beam signals; and

means for summing said separately weighted at least three of said Fast Fourier Transformed N orthogonal beam signals into a single output signal forming said agile beam signal.

14. A digital signal processing apparatus for receive side beam detection of N orthogonal beams and in addition an agile beam according to claim 10, further comprising:

means for summing said separately weighted at least three of said Fast Fourier Transformed N orthogonal beam signals into a signal output signal forming said agile beam signal.

15. A method for transmit side beam forming N orthogonal beams and in addition at least one agile beam signal, using an N-point Fast Fourier Transform processor and an N-element phased array antenna, comprising steps of:

generating a first set of at least three copies of said agile beam signal;

separately weighting, in amplitude and phase, each of said first set of at least three copies of said agile beam signal;

feeding said separately weighted first set of at least three copies of said complex envelope samples into said N-point Fast Fourier Transform processor, via at least three input ports thereof corresponding to said first set of at least three adjacent ones of said N orthogonal beam signals;

performing a Fast Fourier Transform process on complex envelope samples of said N orthogonal beam signals; and

outputting said Fast Fourier transform processed and separately weighted copies of said complex envelope samples at N output ports of said Fast Fourier Transform processor for driving respective ones of said N elements of said N-element phased array antenna;

whereby said at least one agile beam and said N orthogonal beams are formed.

16. A method for receive side beam detection of N orthogonal beams and in addition at least one agile beam, using an N-point Fourier Transform processor and an N-element phased array antenna, comprising steps of:

inputting N baseband complex envelope samples of signals received respectively on said N-elements of said N-element phased array antenna to an N-point Discrete Fourier Transform processor;

discrete Fourier transforming said N baseband complex envelope samples into said N-orthogonal beam signals;

outputting said N-orthogonal beams signals at corresponding N output ports of said N-point Discrete Fourier Transform processor;

weighting separately, in amplitude and phase, a copy of each of at least three of said N orthogonal beam signals output from said N-point Discrete Fourier Transform processor for each of said at least one agile beam signal received by said N-element phased array antenna; and

combining said at least three separately weighted N-orthogonal beam signals to form said at least one agile beam signal;

whereby said at least one agile beam and said N orthogonal beams are detected.