Debasis Mishra

Design of a frequency agile rat race coupler

A frequency reconfigurable 180° hybrid ring having wide tunability within 1.7 GHz - 3.2 GHz range is presented. Equivalent low-pass structures of transmission lines are used for original circuit modification and capacitors are replaced by varactor diodes for continuous tuning purpose. The proposed circuit can provide equal power division with 0°, 180° phase difference at different operating frequencies by simultaneously tuning six varactors. The circuit is designed on low cost FR-4 substrate and has also compact dimension (0.17λ×0.27λ×0.127λ) at 2.5 GHz, 50% less than conventional configuration.

Biconcave Lens Structured Patch Antenna with Circular Slot for Ku-Band Applications

In this paper, the Rotman Lens structure has been modified and implemented as a patch resulting in a structure similar to biconcave lens. Earlier proposed antenna has been designed to operate at the frequency 15 GHz which lies in the Ku-band. By introducing a circular slot, the bandwidth has been increased which enables the antenna to operate over the entire frequency range of Ku-band of frequency range from 12 to 18 GHz used for satellite communication. FR4 Epoxy material has been chosen as the dielectric material for the substrate having dielectric constant 4.4 and the design and simulation has been done using HFSS software. To get the desired result, the optimization tool of HFSS software has been used by choosing a value for the radius of the circular slot that plays the vital role for bandwidth enhancement. Finally, the S-parameter, VSWR, directivity and gain of the proposed antenna were analyzed from the simulation result.

Wideband multiple phase shift quad feed network for polarization reconfigurable antennas

ABSTRACT Design and analysis of a microwave passive network providing multiple phase difference of 0°, 90°, 180° and 270° within broadband 2.6 GHz to 4.0 GHz is proposed and experimentally verified. The network consists of a wideband microstrip balun, two double coupled line 90° phase shifters and three Wilkinson power dividers. The device has −10 dB impedance bandwidth of 42% and its insertion loss varies from 7.55 dB to 7.86 dB within the band. The measured amplitude and phase imbalance between four output ports are within 0.3 dB and ±6° respectively over the required band. The measured isolation among different output ports of the device are below −15 dB. The broadband multiple phase shifting characteristic with equal amplitude value, simple microstrip design technique make the device suitable for polarization agile antennas and an alternative over existing single phase shifters used in many wireless systems.

Biconvex patch antenna with circular slot for 10 GHz application

In this paper the Rotman Lens structure with some perturbation has been implemented as the patch which resembles the biconvex lens shape. The design of the two arcs of the Rotman lens has been modified with reference to certain equations. The Simulation has been done with the help of HFSS software. To enhance the band width, the circular slot has been implemented in the patch. The substrate of the dimension 80mm×80 mm with the dielectric material FR4 epoxy is taken. The simulation results have been analyzed for the frequency 10GHz which is the solution frequency which lies in the X band (8GHz-12 GHz) which is used for NJFA, satellite communication and military applications. After simulation the parameters like VSWR, S11, Gain and Directivity were found out. The results are in good agreement with the desired value. At last the conclusion was made with a brief perception of the future scope.

Perturbed Elliptical Patch Antenna Design for 50 GHz Application

A beam forming patch antenna is proposed for 50 GHz millimeter wave application for wireless personal area network (WPAN). The design involves some modifications of the geometry of prototype Rotman lens structure. The simulation result using HFSS and CST infers some outcomes like reflection co-efficient, VSWR directivity and surface waves, etc. which can be further improved by optimum choice of size and material.

Frequency reconfigurable monopole antenna loaded with dielectric resonator

A frequency reconfigurable antenna using two monopoles integrated on a single ground plane is proposed. One of the monopoles is loaded with ring shaped dielectric resonator for wide-band performance along with frequency agility. The antenna is excited by a switching network consisting of a low loss GaAs SPDT switch for independent operation at different frequencies of 4.53 GHz and 4.82 GHz. Different modes are excited in the DRA for switching conditions of the monopoles which result 23% and 29% of impedance bandwidth, confirming the bandwidth varying characteristic of the antenna. The antenna exhibits stable monopole type omnidirectional radiation pattern with realized gain varying from 1.1 dB-4.6 dB throughout the band which makes suitable for many C-band wireless applications.

Frequency reconfigurable hourglass shaped microstrip antenna

A compact hourglass shaped microstrip antenna having frequency reconfiguring ability from 2.362 GHz to 2.525 GHz range is proposed. A varactor diode is used in the gap between the two segments of ground plane in order to achieve frequency agility. By varying the capacitance of the varactor diode, six operating frequencies 2.395 GHz, 2.435 GHz, 2.445 GHz, 2.455 GHz, 2.47 GHz and 2.495 GHz are achieved with impedance bandwidth of 2.92%, 2.42%, 2.46%, 2.40%, 2.45%, 2.45% and 2.44% respectively. The antenna exhibits stable omnidirectional radiation patterns with realized gain varying from 2.55 dB-1.05 dB for all the bands. These features make the antenna suitable for different wireless application standards like Wi-Fi (2.412 GHz-2.483 GHz), Bluetooth (2.402 GHz-2.48 GHz), WiMax (2.3 GHz-2.4 GHz) etc. The proposed antenna has compact dimensions of 0.44λ×0.25λ×0.013λ at 2.4 GHz frequency which is suitable for many handheld devices.