Santa Maria, CA, United States

Microwave Applications Group
Santa Maria, CA, United States
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Chirakkal S.,Microwave Applications Group | Haldar D.,Microwave Applications Group | Misra A.,Microwave Applications Group
Progress In Electromagnetics Research M | Year: 2017

In this paper we compare, using ISRO’s RISAT-1 FRS-1 mode Compact Polarimetric (CL-Pol) data, two widely used hybrid polarimetric decomposition techniques, m − δ and m − χ decompositions, with regard to classification accuracy for various agricultural crops of north and west India. We show that the classification based on the m − χ decomposition results in better crop separability in general. But the crop stage and existence of orientating structures in the crops affects the efficacy of decomposition; a fact vividly brought out in this paper. Theoretical insights into the effectiveness of these decomposition techniques for different crop geometry are brought forth. We also compare the classification accuracy subsequent to polarimetric speckle filtering vis-a-vis spatial multilooking (downsampling). We show that usage of an appropriate polarimetric filter tends to produce comparable accuracy for most of the agricultural classes, as that of multilook case, without degrading spatial resolution. This work showcases a custom implementation of Stokes parameter based decomposition as well as POLSAR filter based on refined Lee algorithm, written in C and tailored to RISAT-1. © 2017, Electromagnetics Academy. All rights reserved.

Muller A.A.,Microwave Applications Group | Sanabria-Codesal E.,Polytechnic University of Valencia | Lucyszyn S.,Imperial College London
IEEE Access | Year: 2016

Matrix inversion is routinely performed in computational engineering, with coupling matrix filter synthesis considered here as just one of many example applications. When calculating the elements of the inverse of a matrix, the determinants of the submatrices are evaluated. The recent mathematical proof of the Desnanot-Jacobi (also known as the 'Lewis Carol') identity shows how the determinant of an N+2 order square matrix can be directly computed from the determinants of the N+1 order principal submatrices and N order core submatrix. For the first time, this identity is applied directly to an electrical engineering problem, simplifying N+2 order coupled matrix filter synthesis (general case, which includes lossy and asymmetrical filters). With the general two-port network theory, we prove the simplification using the Desnanot-Jacobi identity and show that the N+2 coupling matrix can be directly extracted from the zeros of the admittance parameters (given by N+1 order determinants) and poles of the impedance parameters (given by the N order core matrix determinant). The results show that it is possible to decrease the computational complexity (by eliminating redundancy), reduce the associated cost function (by using less iterations), and under certain circumstances obtain different equivalent solutions. Nevertheless, the method also proves its practical usefulness under constrained optimizations when the user desires specific coupling matrix topologies and constrained coefficient values (e.g, purely real/imaginary/positive/negative). This can lead to a direct coupling matrix constrained configuration where other similar methods fail (using the same optimization algorithms). © 2013 IEEE.

Muller A.A.,Microwave Applications Group | Moldoveanu A.,Polytechnic University of Bucharest | Asavei V.,Polytechnic University of Bucharest | Sanabria-Codesal E.,Polytechnic University of Valencia | Favennec J.F.,French National Center for Scientific Research
IEEE MTT-S International Microwave Symposium Digest | Year: 2016

The paper introduces the concept of hyperbolic reflections in order to complement the hyperbolic rotation matrices used in the lossy coupling matrix filter synthesis. A complex transversal coupling matrix representing a lossy filter is chosen and it is seen how by applying a succession of similarity transformations based also on hyperbolic reflections one obtains different results than by using hyperbolic rotations which are nowadays used in the coupling matrix reconfiguration. Finally a lossy symmetrical filter is designed and simulated based on a folded coupling matrix by shifting the losses into the first and last resonators of the filter. © 2016 IEEE.

Peng Y.,Microwave Applications Group | Farid Rahman B.M.,Microwave Applications Group | Wang X.,Microwave Applications Group | Wang G.,Microwave Applications Group
Journal of Applied Physics | Year: 2014

Perspective magneto-dielectric materials with high permeability are potential substrates to miniaturize the patch antenna without deteriorating its performance. Besides its high permeability at high frequency, patterned Permalloy (Py) also presents tunable permeability by applying DC current. A performance enhanced miniaturized and electrically tunable patch antenna with patterned Py thin film is first presented and developed in this paper. To suppress the magnetic loss, the Py thin film layer is consisted of an array of 2 μm × 2 μm square Py patterns between the copper patch antenna and dielectric substrate. The DC current could be applied directly on Py patterns through the copper strip lines beneath the Py patterns along the length of patch antenna. The copper strip lines are specially designed with the same width of Py patterns and the thickness much less than the skin depth at the operating frequency, which can reduce their deteriorating effects to the performance of antenna. The structure of the antenna is presented and simulated with high frequency structure simulator. The results show that compared with non-magnetic antenna, the performance of Py thin film based antenna is improved with 50% bandwidth increase from 4 MHz to 8 MHz and 1.2 dB gain enhancement from 1.16 dB to 2.36 dB. The resonant frequency of the antenna could be continuously tuned from 937 MHz to 911 MHz with the permeability of Py thin film changing from 1750 to 1 900 by applying the DC current. © 2014 AIP Publishing LLC.

Farid Rahman B.M.,Microwave Applications Group | Divan R.,Argonne National Laboratory | Zhang H.,Intel Corporation | Rosenmann D.,Argonne National Laboratory | And 3 more authors.
Journal of Applied Physics | Year: 2014

A tunable noise suppressor at gigahertz frequency using sub-micrometer patterned Permalloy (Py) loaded coplanar waveguide transmission line is presented. The transmission line consists of 100 nm thick Py patterns on top of 0.9 μm thick gold lines. Measured results show that the stop band frequency of the noise suppressor is changed from 4.8 GHz to 6 GHz depending on the aspect ratios of Py patterns. Variation of the gap in between Py patterns changed the stop band frequency from 4 GHz to 6 GHz. Furthermore, a novel way of tuning the stop band frequency of the noise suppressor by using an external direct current is reported. By applying 150 mA direct current along the transmission line, the frequency is changed from 6 GHz to 4.3 GHz. The measured results of 1.5% pass band loss, 2°transmitted signal phase distortion, and 3 dB extra return loss of the designed noise suppressor are demonstrated. Noise suppression frequency and the magnitude of signal attenuation can be further improved by increasing the thickness of Py or using multi-layer Py. © 2014 AIP Publishing LLC.

Farid Rahman B.M.,Microwave Applications Group | Divan R.,Argonne National Laboratory | Zhang H.,Intel Corporation | Rosenmann D.,Argonne National Laboratory | And 3 more authors.
Journal of Applied Physics | Year: 2014

Slow wave elements are promising structures to design compact RF (radio frequency) and mmwave components. This paper reports a comparative study on different types of coplanar wave-guide (CPW) slow wave structures (SWS). New techniques including the use of defected ground structure and the different signal conductor shape have been implemented to achieve higher slow wave effect with comparative loss. Results show that over 42% and 35% reduction in length is reported in the expense of only 0.3dB and 0.1dB insertion loss, respectively, which can end up with 66% and 58% area reduction for the design of a branch line coupler. Implementation of the sub micrometer patterned Permalloy (Py) thin film on top of the simple SWS has been demonstrated for the first time to increase the slow wave effect. Comparing with the traditional slow wave structure, with 100nm thick Py patterns, the inductance per unit length of the SWS has been increased from 879nH/m to 963nH/m. The slow wave effect of the designed structure is also tunable by applied DC current. Measured results have shown that the phase shift can be changed from 94°to 90.5°by applying 150mA DC current. This provides a solution in designing RF passive components which can work in multiple frequency bands. © 2014 AIP Publishing LLC.

Pujara D.,Nirma University | Chakrabarty S.,Microwave Applications Group
IETE Journal of Research | Year: 2012

This paper presents the design and the experimental results of a dual-mode rectangular-matched feed. This type of feed cancels the unwanted high cross-polarization generated by the offset parabolic reflector antenna. In order to design this feed, higher order TE 11 mode has been added in correct amplitude and phase with the fundamental TE 01 mode in a rectangular structure. The proposed feed was then used as a primary feed to illuminate a linearly polarized offset parabolic reflector antenna. Through experimental results, it is verified that such a feed suppresses the undesired high cross-polarization introduced by the offset geometry of an offset reflector antenna. This kind of feed is very much suitable for monopulse tracking radar. Copyright © 2012 by the IETE.

Muller A.A.,Microwave Applications Group | Favennec J.-F.,French National Center for Scientific Research | Sanabria-Codesal E.,Polytechnic University of Valencia
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2016

The paper introduces the concept of reflection matrices in the coupling matrix filter reconfiguration. It is shown that reflection matrices are complementary to rotation matrices a useful concept that can be used alternatively to rotation matrices in the similarity transformations that are applied in order to transform the coupling matrix to a suitable form. A cross-coupled filter example is given where both concepts are used. © IEEE.

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 1.13M | Year: 2010

The development of capabilities that allow significant removal or reduction of high Global Warming Potential (GWP) Green House Gases (GHG) in the environment is paramount to ensure human health and welfare. The objective of this effort is to develop critical components and technologies that will significantly reduce the need for GHG on the Airborne Warning and Control System (AWACS). In Phase I, Microwave Applications Group (MAG) determined that stress levels in two critical AWACS components – as currently configured – require the use of Sulphur Hexafluoride (SF6) – known to be a GHG. Therefore, the focus of Phase II is to develop replacement configurations of these components such that the use of SF6 is not required. That hardware will then be tested to ensure compliance with AWACS requirements. BENEFIT: Concepts leading to hardware configurations – which are proven in this effort to operate successfully without a GHG – will lead to development of replacement components in military and commercial applications. These applications include radar systems, linear accelerators, and other electrical and radio frequency system requirements.

Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 69.98K | Year: 2010

Phased array systems provide significantly greater data collection capabilities, expanded uses and higher reliability as they reduce or eliminate the need for rotating systems. The major hurdle for widespread usage of phased array systems has been the costs associated with not only developing these systems but also the recurring cost of fabrication and operation. This project investigates a disruptive technology by applying multi-ferroic materials to fabricate rf components for these applications. Although ferrites have historically been the choice for low insertion loss reciprocal and non-reciprocal devices, they are difficult to realize in small geometries and their switching time is excessive. Alternatively, active components are extremely costly and require tremendous power to account for adaptive gain concepts. This project develops an alternative that usurps the best of both constructions. In phase I this project will investigate test results of suitable multi-ferroic devices and evaluate the phase shifter and its required dc magnetic field bias to determine if it can achieve the specifications and evaluate manufacturing concepts to determine achievable methods of fabricating multi-ferroic based planar technology. The goal of phase II of this project is to deliver multiple multi-ferroic phase shifters whose performance parameters bridge the gap between these two technologies by providing the smaller size and faster switching of active components and the simpler control and lower insertion loss of ferrite in a miniaturized package.

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