Showing papers by "Shiban K. Koul published in 2008"

Ka-Band Triangular Patch Antenna on Micromachined High-k Substrate

Abstract: This letter reports a high-performance Ka-band equilateral triangular microstrip patch (ETMP) antenna suspended on a thin dielectric membrane. The membrane is released using a silicon bulk-micromachining technique. A set of closed-form expressions to calculate the resonant frequency of the proposed antenna on the micromachined substrate is also presented. The measured performance of the antenna structure is verified using the finite element method (FEM) based Agilent High Frequency Structure Simulator (version 5.5). The fabricated antenna exhibited a wide -10dB return loss bandwidth of 1.2 GHz at 35.4GHz. The measured antenna cross-polarization level is less than -15dB in both the E- and H-planes.

Studies on ultrawideband filters using stub-loaded circular and triangular resonators

Abstract: Compact UWB bandpass filters using stub-loaded ring and triangular resonators fed with capacitive-ended interdigital coupled lines are proposed. The proposed structures are fed with capacitive-ended interdigital coupled lines. The measured insertion loss for ring resonator filter is 1.0 dB and that for triangular resonator is 2.0 dB with corresponding group delays of 0.6 and 0.3 ns, respectively. These filters show sharp transitions at the edges of the UWB passband and improved out-of-band performance. The simulated and measured results are in good agreement and satisfy the FCC mask for indoor applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2917–2922, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23834

Characteristics of low-k RF MEMS capacitive switches on gallium arsenide substrate

Abstract: This paper details the fabrication and performance of a low-k RF MEMS capacitive switch on gallium arsenide (epsivr =12.9) substrate. The switch is fabricated using GaAs MMIC compatible MEMS specific surface micromachining techniques. The switch posses a movable metallic bridge which pulls down onto a metal/dielectric sandwich to form a capacitive contact. The bridge consists of a proof mass which is supported by meander-type flexures that essentially result in a low effective spring constant of the suspended structure and thus a lower actuation voltage is required to pull the bridge down. The fabricated switch has low insertion loss of 0.5 dB with good isolation of 25.5 dB at 26.5 GHz and the actuation voltage lies in 10-20 V range.

Full wave analysis of non-radiative dielectric waveguide modulator for the determination of electrical equivalent circuit

Abstract: This paper reports the determination of electrical equivalent circuit of ON/OFF modulator in non-radiative dielectric (NRD) guide configurations at Ka-band. Schottky barrier mixer diode is used to realize this modulator and its characteristics are determined experimentally using vector network analyzer. Full wave FEM simulator HFSS is used to determine an equivalent circuit for the mounted diode and modulator in ON and OFF states. This equivalent circuit is used to qualitatively explain the experimental characteristics of modulator.

Triangular Patch UWB Filter with a Band-Notched Characteristic

Abstract: Since the US Federal Communications Commission (FCC) released the unlicensed use of the ultra-wideband (3.1-10.6 GHz) spectrum for indoor and hand-held systems in Feb-2002[1]. Recently, the development of new UWB filters has increased via different methods and structures [2]?[5]. In [2] an initial UWB filter is presented by mounting a microstrip line in a lossy composite substrate to attenuate the signal at high frequencies, and the reported insertion loss is higher than 6.0 dB. In [3] a novel microstrip UWB BPF has been constructed by using a circular ring resonator structure in cascade and the reported insertion loss is 0.58dB in the passband, integration of multiple-mode resonator (MMR) with two coupledlines for the UWB passband [4].