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CP 302 Capstone Project

Presentation on

Submitted To: Dr. Ashwani Sharma (Project Supervisor)

Dr. Hande V. Gopal (Course Instructor)

Presented By: Ajey Singh Bhadauria (2018eeb1133)

Design of Patch Antenna Array for 5G applications

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Antennas are a device which act as a means for generating and receiving Electromagnetic waves through the mechanism of charges undergoing acceleration resulting in a time-varying current.
If the desired specifications for an application are unable to be met using a single antenna element, then Antenna Array is designed utilizing principle of constructive interference of radiations by various individual elements.
The continuously improving communication technology is facilitated by the improving antenna designs.
The upcoming 5G technology aims at higher speed transmission, heavy data traffic requirement, and application in distributed environments.
Some other desired characteristics are:

Compact Size and cost-effective
High Throughput
Large Bandwidth
Large spatial coverage

Introduction

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Patch antenna or Microstrip Antenna (MSA) is a type of antenna which consists of a rectangular metal plate etched over a substrate bounded by the ground plane on the lower end.

Advantages:

Low profile and cost, easy to fabricate, integratable with feed networks on a single substrate

Disadvantages:

Narrow Bandwidth (major disadvantage), low radiation efficiency

Operating frequency governs length of the patch and width controls the input impedance seen at the edge. Increase in width increases Bandwidth of the antenna.
Working: Fringing fields are solely responsible for the radiation. Due to patch length being λ_g/2, they add up in phase to give radiation maxima in broadside direction.
High input impedance is due to low magnitude of current wave at the edge because the voltage and current distribution along the length is much similar to that of an Open circuited transmission line.

Introduction to Patch Antenna

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Patch Antenna Element Design and Results

FR4 Substrate (Relative Permittivity = 4.4)	Thickness = 1.6mm
Quarter Wave Transformer (Z₀ = 110.22 ohms )	Width = 0.53mm, Length = 7.49mm
Patch (Designed for f = 5.8GHz)	Width = 15.739 mm, Length = 11.75mm

Design

Need to improve Impedance Bandwidth and Peak Gain !

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Planar Array design (with straight connecting feedlines)

Interleaved pair of 3 x 2 patch antennas fed in phase through different ports on opposite ends.
Subarrays of series fed linear arrays (consisting of 3 patch antennas each) connected through 100 ohm straight transmission lines are fed using a corporate feed network.
The corporate feed network provides in-phase excitation with equal amplitude.
Connecting feed line lengths are tuned such that all the radiating elements radiate in the same phase in the broadside radiation pattern, thereby having length = . λ/2
The patch is connected to the 100 ohm corporate feedline through a quarter wave transformer (Z₀ = 155.8Ω) to ensure matching
To decrease electromagnetic coupling between patches fed from different ports, the centre to centre distance between consecutive patches along the y-axis was chosen to be λ₀/4 (= 12.33mm).

Feedline connected to source	W = 3.058 mm	L = 7.085 mm
Corporate feedline	W = 0.71 mm	L = 51.72 mm

QWT	W = 0.152 mm	L = 7.085mm
Connecting lines	W = 0.71 mm	L = 12.33 mm
Patch Antenna	W = 15.739 mm	L = 11.75 mm

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Results

There is significant increase in peak gain of the system and the sidelobes have quite less gain in comparison to the major lobe. The radiation efficiency is low due to feedline losses in the corporate feedline configuration.

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Results (after Parametric Sweeps)

Variations in QWT width caused change in resonant frequency and sharp dip was obtained for 0.78mm width.
Variation in either connecting feedline’s width or patch dimensions did not much impact the bandwidth of the array.
Low S21 parameter over the entire frequency range indicates that there is negligible electromagnetic coupling between patches given energy through different feeds.

Orange trace indicates return loss plot after all optimisations.

S₂₁ plot (in dB)

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Planar Array design (with U-shaped connecting feedlines)

The U-shaped connecting line is chosen to reduce inter element spacing, size of the array and provide low Side Lobe Level and improve the bandwidth of the antenna significantly thereby making fast data rate transfer feasible.
The antenna has an improved radiation efficiency although it is still on a lower side which might be attributed to corporate feed losses.
The peak gain of the antenna has slightly reduced but it has come at a trade-off of huge increase in bandwidth.
To further optimise the antenna, we need to find appropriate dimensions of the U shaped connecting line.

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