Optical control of an 8-element Ka-band phased array using a high-speed optoelectronic interconnect

Optical distribution of control signals in electronically steered phased array antennas is being considered. A demonstration experiment is described in which a high speed hybrid GaAs optoelectronic integrated circuit (OEIC) was used to control an eight element phased array antenna. The OEIC, which accepts a serial optical control signal as input and converts it to 16 demultiplexed parallel outputs, was used to control the monolithic GaAs phase shifters of a Ka-band patch panel array antenna. Antenna pattern switching speeds of 2.25 microsec, limited by interface circuitry, were observed

Evolutionary Trends in True Time Delay Line Technologies for Timed Array Radars

Timed array technology is rapidly evolving in multiple areas such as high resolution imaging radar, automotive, medical, high data rate communication applications etc. Timed arrays by utilising True Time Delay (TTD) lines in place of phase shifters mitigate beam squint and pulse dispersion issues associated with wide instantaneous bandwidth arrays. This paper presents on review of evolutionary trends in TTD line architectures starting from coaxial cable to photonic integrated circuit. The paper also reports on critical parameters of TTD lines, their importance and implication in design of typical X-band imaging radar. Comparison of different TTD line architectures in terms of configuration, implementation, merits and demerits are discussed in detail for wideband array application. The paper also brings out the integration aspects of TTD lines as part of T/R modules and proposes suitable design schemes towards performance optimization and realisation of timed arrays

Boundary layer flow and heat transfer over a permeable shrinking sheet with partial slip

The steady, laminar flow of an incompressible viscous fluid over a shrinking permeable sheet is investigated. The governing partial differential equations are transformed into ordinary differential equations using similarity transformation, before being solved numerically by the shooting method. The features of the flow and heat transfer characteristics for different values of the slip parameter and Prandtl number are analyzed and discussed. The results indicate that both the skin friction coefficient and the heat transfer rate at the surface increase as the slip parameter increases

Some Recent Advances in Microwaves A Review

Some recent advances in microwaves such as gyrotron, gyro-TWT, IMPATT, radio camera MIC, etc, which finds applications in defence have been reviewed. Our claim is to brevity, not to profundity in originality

A clinical and molecular characterisation of CRB1-associated maculopathy

To date, over 150 disease-associated variants in CRB1 have been described, resulting in a range of retinal disease phenotypes including Leber congenital amaurosis and retinitis pigmentosa. Despite this, no genotype–phenotype correlations are currently recognised. We performed a retrospective review of electronic patient records to identify patients with macular dystrophy due to bi-allelic variants in CRB1. In total, seven unrelated individuals were identified. The median age at presentation was 21 years, with a median acuity of 0.55 decimalised Snellen units (IQR = 0.43). The follow-up period ranged from 0 to 19 years (median = 2.0 years), with a median final decimalised Snellen acuity of 0.65 (IQR = 0.70). Fundoscopy revealed only a subtly altered foveal reflex, which evolved into a bull’s-eye pattern of outer retinal atrophy. Optical coherence tomography identified structural changes—intraretinal cysts in the early stages of disease, and later outer retinal atrophy. Genetic testing revealed that one rare allele (c.498_506del, p.(Ile167_Gly169del)) was present in all patients, with one patient being homozygous for the variant and six being heterozygous. In trans with this, one variant recurred twice (p.(Cys896Ter)), while the four remaining alleles were each observed once (p.(Pro1381Thr), p.(Ser478ProfsTer24), p.(Cys195Phe) and p.(Arg764Cys)). These findings show that the rare CRB1 variant, c.498_506del, is strongly associated with localised retinal dysfunction. The clinical findings are much milder than those observed with bi-allelic, loss-of-function variants in CRB1, suggesting this in-frame deletion acts as a hypomorphic allele. This is the most prevalent disease-causing CRB1 variant identified in the non-Asian population to date

Configuration study for a 30 GHz monolithic receive array, volume 1

Gregorian, Cassegrain, and single reflector systems were analyzed in configuration studies for communications satellite receive antennas. Parametric design and performance curves were generated. A preliminary design of each reflector/feed system was derived including radiating elements, beam-former network, beamsteering system, and MMIC module architecture. Performance estimates and component requirements were developed for each design. A recommended design was selected for both the scanning beam and the fixed beam case. Detailed design and performance analysis results are presented for the selected Cassegrain configurations. The final design point is characterized in detail and performance measures evaluated in terms of gain, sidelobe level, noise figure, carrier-to-interference ratio, prime power, and beamsteering. The effects of mutual coupling and excitation errors (including phase and amplitude quantization errors) are evaluated. Mechanical assembly drawings are given for the final design point. Thermal design requirements are addressed in the mechanical design

NASA SBIR abstracts of 1990 phase 1 projects

The research objectives of the 280 projects placed under contract in the National Aeronautics and Space Administration (NASA) 1990 Small Business Innovation Research (SBIR) Phase 1 program are described. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses in response to NASA's 1990 SBIR Phase 1 Program Solicitation. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 280, in order of its appearance in the body of the report. The document also includes Appendixes to provide additional information about the SBIR program and permit cross-reference in the 1990 Phase 1 projects by company name, location by state, principal investigator, NASA field center responsible for management of each project, and NASA contract number

A 100-MESFET planar grid oscillator

A 100-MESFET oscillator which gives 21 W of CW effective radiated power (ERP) with a 16-dB directivity and a 20% DC-to-RF conversion efficiency at 5 GHz is presented. The oscillator is a planar grid structure periodically loaded with transistors. The grid radiates and the devices combine quasi-optically and lock to each other. The oscillator can also be quasi-optically injection-locked to an external signal. The planar grid structure is very simple. All of the devices share the same bias, and they can be power and frequency tuned with a mirror behind the grid or dielectric slabs in front of it. An equivalent circuit for an infinite grid predicts the mirror frequency tuning. The planar property of the oscillator offers the possibility of a wafer-scale monolithically integrated source. Thousands of active solid-state devices can potentially be integrated in a high-power source for microwave or millimeter-wave applications

Module, Filter, And Antenna Technology For Millimeter Waves Multi-gigabits Wireless Systems

A method of fabricating an ultra-high frequency module is disclosed. The method includes providing a top layer; drilling the top layer; milling the top layer; providing a bottom; milling the bottom layer to define a bottom layer cavity; aligning the top layer and the bottom layer; and adhering the top layer to the bottom layer. The present invention also includes an ultra-high frequency module operating at ultra-high speeds having a top layer, the top layer defining a top layer cavity; a bottom layer, the bottom layer defining a bottom layer cavity; and an adhesive adhering both the top layer to the bottom layer, wherein the top layer and the bottom layer are formed from a large area panel of a printed circuit board.Georgia Tech Research Corporatio