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Dual circular polarization (CP) services are growing in popularity in satellite communications applications. Ground terminals with linearly polarized dish antenna feeds routinely achieve high port isolation between polarizations, but dual CP feeds suffer from higher coupling between ports associated with orthogonal polarizations, particularly for planar microstrip antennas used in electronically beamsteered...
This paper investigates the performance of shaped systems with extended sub-reflectors with the goal of maximizing the sensitivity for a given feed pattern. It is shown that an extended sub-reflector may indeed provide improved sensitivity performance, especially if the system is tipped in the feed down configuration. The performance of systems illuminated with feeds with varying tapers is also investigated,...
A limited set of possible optics candidates for the SKA was recently proposed. This paper investigates the sensitivity performance of these offset Gregorian reflectors over tipping angle when illuminated by an ideal feed with varying edge tapers. The results show that feed down tipping together with a sub-reflector extension, that shields the feed from the ground radiation, achieves the best sensitivity...
The sensitivity performance of several primary pattern to aperture field mappings in shaped offset Gregorian reflector systems is investigated. Specific attention is given to high efficiency mappings with low second side-lobe levels, as these are of interest in the design of sensitive radio telescopes where the first side-lobe is imaged in the point spread function. Comparisons are made between the...
The operational Land Imager (OLI) aboard Landsat 8 was launched in February 2013 to continue the Landsat's mission of monitoring earth resources at relatively high spatial resolution. Compared to Landsat heritage sensors, OLI has an additional 443-nm band (termed coastal/aerosol (CA) band), which extends Landsat's potential for mapping/monitoring water quality in coastal/inland waters. In addition,...
In this paper, a pipelined implementation of a Hessenberg-based input balanced realization is derived, which is realized by placing the delay elements in the lower path and the upper path alternately. The proposed pipelined structure is canonical in the sense that no extra delay is needed. For an Nth order filter, the proposed structure requires 5N −1 multipliers, which has two less multipliers than...
A simplified version of a recently developed structure is derived for all-pass filters. The proposed structure possesses 4N non-trivial multipliers and 2N adders used for computing one output sample of an Nth order all-pass filter. It is shown that such a structure yields a roundoff noise gain of 4N, compared with that of (N +1)2 for the classical minimum roundoff noise realizations that have in general...
A fully-differential capacitive touch sensing method is proposed in which common-mode noise currents are symmetrically subtracted at the differential input of the first stage such that it doesn't contribute to dynamic range reduction in the later stages. And, for better sensitivity, the proposed method could accumulate signal charges in continuous time domain, and does not suffer from aliasing issues...
This paper describes a novel approach towards optimal tuning of distributed order fractional PID controller parameters. A distributed order fractional PID controller (DPID) is approximated by a compound fractional controller with multiple fractional differintegrators connected in parallel. Orders of these differintegrators have been equally spaced, with the first one being the classical integrator...
A new frequency-domain algorithm for optimization of PID regulators having a fractional differential compensator connected in series (PIDCα) has been developed. The adjustable parameters of the regulator are: proportional gain k, integral gain ki, relative attenuation factor of PID zeros ζ, zero of the fractional differential compensator -1/τ and fractional power a of the differential compensator...
Output of SRAM memory circuit is very small i.e. in few milli volts. While reading logic 1 sometimes it is read as logic 0. Due to this malfunctioning of circuit, problem of hazards occur. To overcome this problem we use sense amplifiers. The work of sense amplifier is to sense low power signal from bit line of SRAM memory circuit and amplify the small voltage swing to recognizable logic levels so...
It can be difficult to compare the merits of cameras using different sensor technologies using only the specifications typically provided by the manufacturers. The Noise Equivalent Irradiance (NEI) provides a normalized and unique parameter allowing a direct comparison. It is also fairly simple to calculate from the commercial specifications for a given wavelength and exposure time of interest. We...
This paper deals with the main results about LGT crystals and, as far as possible, indicates the comparative aspects with the quartz crystal. We present also the manufacturing process and their differences with a quartz resonator. The passive noise analyses and the drive level effect are presented in the paper as well as the g-sensitivity and the magnetic sensitivity of LGT oscillators. Example of...
The resolution of a magnetic sensor depends on its intrinsic noise, offset instability and the magnetic sensitivity. Both noise and offset can be substantially reduced by the spinning current technique. The effective magnetic sensitivity can be increased by the application of a magnetic flux concentrator. The physical limit of magnetic sensitivity is estimated. Values of sensitivity, noise and offset...
Interferometric gravitational wave detectors are amongst the most sensitive instruments ever built. They are hunting for tiny oscillations in space-time originating from cosmic events such as inspiraling objects or supernova explosions. These detectors are based on Michelson-like interferometers reaching sensitivities for lengths changes of better than 10−18 m/√Hz. Currently, a second generation of...
In this paper we compare two versions of fourth-order band-pass (BP) filter section realized as coupled structure, having negative feedback around two Biquadratic sections in cascade, usually designated as Biquartic section (i.e. it is the fourth-order band-pass section). The frequency response of a filter is subject to vary from the nominal values due to the effects of aging, changing working conditions,...
This paper presents a comparison between fractional order controllers and integer order controllers. The well-known PID is the integer order controller chosen whereas the generalized PID and the CRONE (“Commande Robuste d'Ordre Non Entier” which stands for fractional order robust controller) are the fractional order controllers studied. Another big difference between these controllers is that the...
Analyzing the structure of motor variability is important to understand neural control of movement. Although many previous studies have suggested analysis methods to account for task-relevant variability, it has been revealed that even a simple linear transformation of the coordinate system causes qualitatively different interpretation of the variability analysis. The present study suggests a revised...
A general superdirective beamforming method which is suitable for arbitrary-shape sensor arrays is proposed, and its performance for linear arrays is studied in this paper. Based on Gram-Schmidt orthogonalization, the optimal solutions of superdirectivity are all expressed in closed-form without any approximations. The optimal beampattern and the maximum directivity factor are decomposed into mode-beams...
The scope of this paper is to underline the design issues of MEMS microphones and presents a test case designed using the PolyMUMPs process with an additional back-etch processing step. Both circular and square (simply supported and clamped) diaphragm designs are considered. The effect of the back chamber volume on the microphone sensitivity is also investigated. The finalized design is based on the...
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