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Simulation of Antennas: Understanding EM Waves and Designing Miniaturized Antennas

Task 1

This course work aims at practical simulation to understand the principle of Antenna. Laboratory sessions will cover concepts of EM waves in different antennas.

This assessment satisfies the following learning outcomes as specified in your module guide.

Work with information that may be incomplete or uncertain to devise solutions for electromagnetism problems and critically evaluate the effect of this on the design. (D3p)

 

Critically evaluate the contexts in which engineering knowledge can be applied, e.g. operations and management, application and development of technology, etc. (EP1p)

This course work represents 40% of the total assessment for the module.

A single hollow waveguide can conduct two kinds of electromagnetic waves: transversal magnetic (TM) or transversal electric (TE) waves.

Waveguides may be bent in several ways that do not cause reflections. Waveguides having gradual bend is known as an E bend as it distorts the E fields. The E bend must have a radius greater than two wavelengths to prevent reflections.

Another common bend is the gradual H bend and it called because the H fields are distorted when a waveguide is bent in this manner. The radius of the bend must be greater than two wavelengths to prevent reflections.

A sharp bend in either dimension may be used if it meets certain requirements. The reflections that occur at the 45-degree bends cancel each other, leaving the fields as though no reflections have occurred.

Examine a TE wave that has no electric field component in the direction of propagation. Select the frequency and waveguide dimension so that TE10 is the single propagating mode. In that mode the electric field has only one nonzero component—a sinusoidal with two nodes, one at each of the walls of the waveguide.

Model a H-bend that computes the electromagnetic fields and transmission characteristics of a 90° bend for 0.08 radius and a cutoff frequency of 3.7 GHz.

(15 marks)

 

Obtain S-parameter plot and Smith plot to give the quantitative measure of how much of the wave is transmitted and reflected at different frequencies of the H-bend model created.

(15 marks)

Antennas are essential components in mobile devices and are required to fit in the limited space allowed by industrial specifications. To fulfill this requirement, a planar inverted-F antenna (PIFA) is common and a popular choice for miniaturized antennas in cellular phones. The PIFA design can be tuned and extended to cover multiple frequency bands from cellular phones, Wi-Fi and Bluetooth.

The antenna is tuned only for the Advanced Wireless Services (AWS) band downlink frequency range. The impedance matching properties of the antenna are calculated in terms of S-parameters and the far-field radiation pattern is simulated. The AWS band downlink frequency range is from 2.11 GHz to 2.155 GHz. At this frequency range, the metal part of the antenna can be modeled using perfect electric conductor (PEC) boundaries. The losses on the metal surfaces are negligible because of the high conductivity of the copper.

A lumped port with a reference impedance of 50 ? is used to excite the antenna and evaluate the input impedance. The lumped port is assigned between two metallic boundaries: the ground plane of the FR4 board and a vertical feeding strip. Another strip shorted to the ground plane is added adjacent to the feeding strip for impedance matching. The distance ?, the impedance matching gap, plays an important role for matching the antenna to the reference impedance.

Design a antenna to make the resonant frequency of the antenna close to 1.575 GHz to provide high receiving efficiency as much as possible. The gain of the antenna should be between -3dB to 0dB. Install the antenna in prefabricated mobile phone casing to left of the casing with a dielectric constant of 2.1 in addition the outer shell of the casing is simulated with Polytetrafluoroethylene (PTFE).

Generate the E-field norm on the xy-plane where the height of the plane is adjusted to visualize the plot on the top surface of the PIFA to resemble the field distribution of a quarter-wave monopole antenna.

(15 marks)

 

The polar-formatted far-field radiation pattern of the antenna and the azimuthal radiation pattern should not be omni-directional and the antenna gain on the xyplane has to vary from ?6 dBi to 2 dBi.

(15 marks)

 

Using S-parameter plot and Smith plot show S11measurements indicating that at a 1.575GHz is below -10 dB with reflected power of 5% to have an antenna input impedance matched to the 50 ? reference impedance.

(20 marks)

 

Show using 3D the maximum radiation far-field radiation pattern of the antenna.

(20 marks)

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