Radiation pattern measurement method for on-wafer mm-wave antenna

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master_Khairkar_Gaurav_2016.pdf (4.67 MB)

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Sähkötekniikan korkeakoulu | Master's thesis
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Date

2016-06-13

Department

Major/Subject

Radio Science and Engineering

Mcode

S3012

Degree programme

EST - Master’s Programme in Radio Science and Engineering (TS2005)

Language

en

Pages

43+8

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Abstract

With the advent of new technology, the manufacture of high-frequency antennas and RFIC's has become feasible. This has led to smaller and smaller antennas in the mm-wave frequency range. The traditional techniques used for antenna characterization may be problematic for small probe-fed antennas. To counter these problems, radiation pattern retrieval (RPR) method has been developed. RPR is dependent on the reflection coefficients obtained from placing a reflective load in the near-field of the antenna. RPR method is implemented using inversion algorithm. Multiple reflections can cause errors in RPR as it considers only the first reflection from reflective load. To address this issue, time gating method is investigated. The purpose of this thesis is to study radiation pattern retrieval for on-wafer antennas, especially to improve RPR method using multiple reflection mitigation, implemented using time gating. To experimentally test this hypothesis, a 4x4 patch array is designed for 77 GHz. A reflective copper strip is placed at 90 mm or 120 mm distance from the antenna. The width of the strip is 30 mm and 60 mm and it is moved in 1.95 mm steps from -39 mm to +39 mm offset positions. A VNA measures the $S_{11}$ at each position which is Fourier transformed into its time domain signal, time gated and then transformed back to the frequency domain. The new $S_{11}$ is used to observe the effects on the radiation pattern. The copper strip configurations with different widths and distance help test the repeatibility of the experiment. Time gating is estimated to remove unwanted reflections, however, inconclusive results suggest the need for exhaustive study of the inversion algorithm and RPR model. More qualitative study of multiple reflection reduction techniques would give a deeper insight in their effect on radiation pattern retrieval.

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Supervisor

Räisänen, Antti

Thesis advisor

Ala-Laurinaho, Juha

Keywords

on-wafer, antenna, mm-wave, antenna meaurements, radiation pattern, time gating

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https://urn.fi/URN:NBN:fi:aalto-201606172536

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[dipl] Sähkötekniikan korkeakoulu / ELEC