Sayan Chatterjee

An Investigation of Bandwidth Characteristics of Waveguide-Fed Planar Slot Arrays

Abstract The frequency response of the return loss and radiation pattern performance of waveguide-fed planar slot arrays is investigated as a function of the total admittance of radiating slots in each radiating waveguide and the total impedance of coupling slots in each feed waveguide. End-fed and center-fed planar arrays with different aperture distributions and different amounts of overloading were designed using Elliotts equations. These arrays were analyzed by the method of moments solution for the coupled integral equations for the slot aperture electric field. Results on the bandwidth of radiation pattern and return loss for different amounts of overloading are discussed.

Synthesis of linear array using Taylor distribution and Particle Swarm Optimisation

In this article, non-uniformly excited linear arrays are optimised using Taylor distribution and classical particle swarm optimisation (CPSO) algorithm for obtaining desired equal side lobe level (SLL). Elements of the array are considered to be isotropic in nature with uniform interelement spacing. Excitation amplitudes of each element are taken as optimisation parameters. Taylor distribution defines the range of excitation amplitude in which CPSO algorithm searches for the optimum value of excitation amplitude, with the objective of obtaining desired equal SLL. The proposed method eliminates the initial randomness of defining search space for CPSO algorithm. Comparison with other methods has been made whenever possible. The results reveal that the proposed method can be used to obtain the desired SLL.

Compact K-band distributed RF MEMS phase shifter based on high-speed switched capacitors

A high-speed switched capacitor based distributed MEMS phase shifter has been presented. Miniaturization of the conventional MEMS capacitor dimensions has been done to achieve sub-microsecond switching, lower actuation voltage and a compact structure. Conventional design approach of such high-speed MEMS capacitor based phase shifter employs cascading the capacitors on a linear coplanar transmission line. Compactness of the device is achieved by employing space filling curves like i) Meander line CPW and ii) Modified Hilbert curve CPW. Simulations conducted reveal that the modified Hilbert Curve based phase shifter provides the most compact structure and yields a phase shift of ∼180° at 22GHz (K-band). The modified Hilbert Curve occupies an area of (820×820) µm2 only. Electromechanical simulations indicate that the switched capacitors require an actuation voltage of 14V and a switching time of 220ns.

A 4-bit Asynchronous Binary Search ADC for Low Power, High Speed Applications

In this paper the implementation of a low power high speed 4-bit Binary Search ADC (BS-ADC) is reported using 180 nm CMOS technology. The concept of Threshold Modified Comparator Circuit (TMCC) is introduced as a modification of the latch-based conventional comparators. The reported structure of the ADC occupies an active area of 0.0157 mm2 and consumes 127 μW of average power while operating with an input frequency (fin) of 5 MHZ, and a supply voltage of 1.8Volt. For this proposed architecture, the maximum sampling rate is obtained as 0.2 GSPS. At 0.2 GSPS sampling rate, the Signal to Noise plus Distortion Ratio (SNDR) is found to be 20.84 dB, yielding the Effective Number of Bits (ENOB) as 3.2 bit.

Pattern synthesis of centre fed linear array using Taylor one parameter distribution and restricted search Particle Swarm Optimization

In this article, a new method of pattern synthesis of centre fed, equal distance linear array having single and multiple synthesis objectives has been proposed and statistically investigated. Single objective of reduced side lobe level (SLL) and first null beamwidth (FNBW) has been considered separately. Consequently, multiple objectives of beamwidth and side lobe level have been investigated. Synthesis of linear array for suitable objectives has been investigated on Taylor one parameter distribution with equal progressive phase. Excitation amplitude of each array element is taken as optimization parameter where distribution has been optimized using Particle Swarm Optimization (PSO) for achieving low SLL. Later the same has been incorporated for obtaining suitable FNBW. In our optimization algorithm conventional PSO has been modified with a restricted search PSO (RSPSO) where search space has been predefined within excitation amplitude range. PSO within the defined range searches for optimum excitation amplitude to achieve the desired objectives. In order to illustrate the effectiveness of the proposed RSPSO, simulation results of three significant instances of linear array have been presented for both even and odd number of element. The design results obtained using RSPSO have improved result than those obtained using other state of the art evolutionary algorithms like differential evolution (DE), invasive weeds optimization (IWO) and Conventional particle Swarm optimization (CPSO) in a statistically significant way.

Thermal analysis of cantilever MEMS based Low power microheater array for the selective detection of explosive and toxic gases

A cantilever type microheater array consisting of four individual isolated microheaters on single die has been designed here for MEMS based gas sensor platform using metal oxide semiconductor for different gas detection through a single sensor die for explosive and toxic gas analysis in the underground manhole. A thin SiO2/Si3N4 cantilever of 250µn X 100µn has been designed here for low power consumption and uniform temperature distribution throughout the entire active area. As the microheaters are isolated from each other, different temperatures may be achieved by applying different voltages in different heaters.

Design and Analysis of a Robust, High Speed, Energy Efficient 18 Transistor 1-bit Full Adder Cell, Modified with the Concept of MVT Scheme

Optimization of power and speed is the most crucial issue for any low-voltage, low-power design. In this paper an Energy Efficient, Robust 18 Transistor (18T) 1-bit Full Adder (FA) cell, modified with the concept of Mixed Threshold Voltage (MVT) scheme, is reported. The entire design is done in 45nm technology, and compared to the conventional one, a considerable amount of reduction in the Average Power consumption (Pavg) as well as the Power Delay Product (PDP) has been achieved. For an operating frequency of 500MHz, the Pavg is as low as 9.31×10-8 Watt, whereas the PDP for Sum output is found to be 1.115×10-18 Joule. The analyses have been carried out with help of the simulation runs on SPICE, and that indicate, for the lower Supply Voltages (Vdd), MVT scheme can be a more practical option than the simple dual threshold technique.

Field characterization of an iris excited 10GHz slot radiator

Normalized electric field along the slot length for different depth of iris is studied at 10GHz in this paper. Resonance length is obtained as 15mm for which electric field symmetry is observed. Thick iris-slot combination is studied with reassigned mesh to obtain perturbation of slot field at certain depth of iris. From the slot voltage calculation slot excitation is found to be at 5.3mm depth of iris.

Design of circularly polarized waveguide crossed slotted array antenna at Ka band

Present paper highlights an improvement over the use of conventional cross slot radiator in waveguide broadwall for circular polarization by using a combination of cross slot and inclined slot pair. Accordingly, a circularly polarized travelling wave slotted array antenna at Ka band (38.6GHz) of 20dB gain has been designed and verified in a nonstandard waveguide using the modified cross slot radiator.

Development of window for first Indian gyrotron

Window happens to be the most critical and vulnerable component in high-power gyrotrons. For the first Indian gyrotron window, a face cooled double sapphire disc structure has been decided for delivering 200 kW power at 42 GHz. Development of sapphire machining and techniques for its UHV grade joining to metals are the major achievements so far. Optimisation of electrical and thermal parameters is in progress.