US 5,510,799 AGranted

Method and apparatus for digital signal processing

AssigneeMMS Space Systems Limited

InventorAlexander W. Wishart

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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.

Claims16

Dependent claims

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.

13 more elements

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.

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.

Dependencies are inferred from the claim text.