Page 19 - SPECTRUM.pdf

Department of Electronics and Communication Engineering, Nirma University

Finally, the aspect of mutual coupling reduction has been addressed by the use of different defected ground
structures. Mutual coupling reduction is the most essential factor for the use of antennas in multiple-input

multiple-output (MIMO) applications. Four DRA array designs with novel DGS structures have been proposed. In
the first two designs namely, fractal Tree- and stacked fractal Maltese Cross-shaped DRA array, periodic defected
ground structure (PDGS) of C-shape has been incorporated to achieve mutual coupling reduction (< -15 dB).

Elliptical-shaped DGS is used to reduce mutual coupling in the Triangular Prism-shaped fractal DRA array (third
design). The fourth design is a Surya Yantra-shaped fractal DRA array with rectangular loop-shaped DGS for
better isolation between DR elements. In all, ten novel designs have been proposed along with their detailed

study.
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Title of Thesis: Design and Development of Higher Order Subharmonic Mixers

ABSTRACT: Microwave mixers are inevitable modules in any RF sub-system.
Enabling frequency translation, mixers have always played a pivotal role in
venturing into the higher frequency domain. Progressive development in

Monolithic Microwave Integrated Circuit (MMIC) technology has enabled the
realization of highly condensed and complex core chip RF modules covering
THz technology via the realisation of high-frequency mixers employing Schottky

diodes. Likewise, the mixing phenomenon has advanced from fundamental
Shailendra Singh (12EXTPHDE86))
mixing to sub-harmonic mixing wherein higher order of lower frequency Local
Oscillator (LO) frequency is utilized advantageously making the circuitry compact and avoiding the need for

generating higher LO frequencies. This research work involves investigation wherein three novel findings have
evolved as an outcome of the research; formulating spurious frequency determination, simplifying fundamental I-Q
mixer and realizing 6X Sub-harmonic IQ mixer using improved idlers. The findings are briefly described below:
1. Formulae for Determining Heterodyne System Spurious Frequencies that Coincide with Desired Output

Frequency: Till date, no direct formulae have been reported for determination of the lowest order coinciding
spurious.
2. Proposal and Demonstration of a Simplified Design Topology for I-Q mixers: Conventional I-Q Mixers utilize

hybrids, vias, cross over or wire-bonds for realization. The proposed design is based on a unique
arrangement of six RF power dividers and avoids complex structures like hybrids or vias.
3. Design and Realization of a 6X Sub-harmonic IQ MMIC using Improved Lumped Component Microwave Multi-
Frequency Idler: Two design methodologies for the realisation of compact and improved microwave lumped

component multi-frequency idlers for monolithic integrated circuits have been proposed and using this a 6X
Sub-harmonic IQ MMIC Mixer has been designed.

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