Hughes Aircraft Company

Hughes Electronics Corporation

Other

Steve I Hsu

Stephen D Taylor

Howard S Nussbaum

William P Posey

Trung T Nguyen

Irwin L Newberg

Paul Sajda

Oleg Brovko

Jeffrey W Berger

Jane Asmuth

Robert A Kosmala

Ricardo Rico, Jr

A system and technique for phased array antenna beam steering for transmitting and receiving without sending the waveform through an actual (physical) time delay when a time varying frequency is used as the waveform. The inventive system is adapted for use with an antenna having an array of radiating elements and includes a plurality of signal sources. Each source is adapted to provide a signal having a predetermined frequency offset signal for an associated radiating element or set of radiating elements. For transmit a plurality of first mixers is provided. Each of the first mixers is coupled to receive an excitation signal as a first input and the output from a respective one of the sources as a second input. The output of each mixer is coupled to a respective subset of the antenna radiating elements. In effect, each of the sources provides a virtual time delay. In a specific embodiment, the virtual time delay source includes a direct digital synthesizer and a digital-to-analog converter connected to receive the output thereof. A second mixer is included in each source for mixing the output of the converter with the output of a supplemental signal source. For receive the process is implemented the same way as for transmit for the range of the desired &ldquo;target&rdquo; return. The output of the second mixer is supplied to a respective one of the first mixers. The invention adjusts the phase and frequency of an RF waveform that is spread out in frequency and time such that each frequency arrives at the radiating elements of a phased array antenna with the phase that will steer the antenna beam in the desired direction. The relative signal phase at each radiating element is made to be independent of the signal carrier frequency and thus the antenna beam pointing is made independent of RF carrier frequency.

Phased array antenna system with virtual time delay beam steering

The invention is a method and system for mosaicing images of the eye to create high resolution, wide-field ophthalmic images for the diagnosis and treatment of eye diseases. The inventive method acquires a first image of the eye, acquires a second image of the eye, and processes the images to produce a mosaic representation. The second image includes a portion of the first image. To guide in acquiring the second image, the method may view the first image while acquiring the second image. The images typically are acquired using either a direct ophthalmoscope or a slitlamp biomicroscope. The method further may convert the images to a digital format. The step of processing includes aligning and merging the images, and conducting real-time processing and non-real-time processing. Real-time processing may include eliminating non-overlapping images, image registration, topology inference, local-to-global alignment, image fusion, signal estimation, and multiresolution blending, while the non-real-time processing may include local alignment, global alignment, image registration, intra-alignment, inter-alignment, signal averaging, and photometric blending.

Mosaicing and enhancement of images for ophthalmic diagnosis and documentation

A phase shifter using digital counters allows extremely accurate phase shifts. In a parallel circuit arrangement of a number of basic phase shift units, which each includes a dual modulus counter and phase control circuitry for controlling the counter modulus, the outputs of several units are combined in parallel. With the divider ratios of all the dividers of the units consisting of roots of pairwise relatively prime numbers, the total number of phase states is equal to the multiplication of its divider ratios.

Digital frequency divider phase shifter

Discrete phase modulation for modulating the transmit and receive radar signal waveforms in order to control distortion. The signal is modulated by discrete phases which change from pulse-to-pulse. A digital frequency division circuit accurately generates the modulation signals, and allows the discrete phases to be generated with precise accuracy. The discrete phase changes can be a quadratic phase progression for target Doppler and range detection.

Discrete phase modulator

A phase shifter that employs digital circuitry to achieve arbitrarily fine phase control of reference signals at frequencies extending to the Gigahertz region. The phase shifter includes a cascade of identical phase shift units that provide progressively finer phase control resolution over a full 360 degree range. The phase precision is set by the number of stages used.

Precision digital phase shifter

A precision digital phase shift element for achieving precise phase shift of an input pulse train signal. The output is a pulse train at a frequency equal to the input signal frequency divided by N, and having N equally spaced phase states. The relative phase state of the output signal is reliably controlled by selective deletion of pulses from the input signal pulse train. The selective deletion can be achieved by selectively gating the input pulse train, or by use of a dual modulus frequency divider circuit.

Precision digital phase shift element

The frequencies of N oscillators are summed to provide a signal generator output signal. Because the phase noise power spectral densities of the oscillators add as power, the frequency summed output exhibits a noise degradation over a single oscillator of only 10 log(N). The signal generator is implemented to assure independence of the oscillator noise contributions, with phase locking the oscillators to a common frequency for ease of spurious signal control.

Ultra low noise frequency generator producing the sum of plural signal

A digital waveform synthesizer, using a direct digital synthesizer and a digital frequency divider. The direct digital synthesizer provides a digitally synthesized input frequency signal. An upconverter and frequency divider circuit upconverts and divides the synthesized input frequency signal to provide an divided synthesized frequency signal. An output upconverter circuit is coupled to the upconverter and divider circuit for providing an upconverted output frequency signal. A reference frequency generator is coupled to the direct digital synthesizer, to the upconverter and divider circuit, and to the output upconverter, for providing clock and frequency reference signals thereto. The waveform generator is coupled to the direct digital synthesizer for commanding a desired waveform. The frequency divider is used to improve the inherently poor spurious signal performance of the direct digital synthesizer. The digital waveform synthesizer provides fast switching, flexible and precisely defined frequency output signals. The digital waveform synthesizer may be used with any signal generator that requires high spectral purity and frequency precision, but requires relatively narrow signal bandwidth.

High spectral purity digital waveform synthesizer

An efficient wideband low noise microwave signal generator for active radars. Separate transmit drive (TD) and receiver local oscillator (LO) signals are generated by use of a single programmable reference generator and two frequency synthesized signals separated in frequency by an offset precisely equal to the transmit drive offset. The frequency synthesized signals are respectively summed and subtracted in frequency with the reference generator signal to obtain signals which may be selected as the TD and LO signals.

Growing community of inventors

Rancho Palos Verdes, CA, United States of America

Steve I Hsu