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Advanced Communication Systems – Part 2

Coursework Assignment

Design of microstrip lines, impedance matching networks and antennas for modern communication systems

ASSIGNMENT REQUIREMENT

In this assignment, you are required to perform the design of microstrip lines, matching networks, and array antennas. For tasks 1-2 you should use the simulation software package AWR Microwave Office and specifically the Circuit Schematic Environment. For task 3 you should implement the relevant equations and perform the design in a mathematical software (such as Matlab). The theoretical aspects of the analysis and design procedures have been covered in lectures and can also be found in the relevant textbooks. In all of the tasks described below, you should clearly explain the basic theory used for your design, describe the steps followed and discuss your results.

The design frequency is 3.5 GHz.

You may use a substrate material with parameters chosen from Table 1. Choose a substrate thickness (height) from the list of available values in Table 1.

In all of the tasks you need to present clearly the appropriate results, such as reflection (R) / transmission (T) coefficients, Smith Charts, radiation patterns in the case of the antenna etc.

1. Design a microstrip line that connects two 50 Ohms ports. Present clearly the R/T coefficients (S11 and S21) over a range of frequencies around the central operating frequency of 3.5 GHz. Subsequently, change the impedance of one of the ports to 150 Ohms. Design a microstrip quarter-wave transformer in order to match the microstrip line to the 150 Ohm port. Present clearly the structures that you have designed, the R/T coefficients (S11 and S21) over a range of frequencies around the central operating frequency of 3.5 GHz (20%).

2. (a) Design an LC matching network (using inductors and capacitors) that connects a 50 Ohm port to a load made of a 70 Ohm resistor and a 1pF capacitor in series at 3.5 GHz. (25%)

(b) Design a single shunt stub matching network using short-circuit (s/c) microstrip line sections to match the above load impedance. (25%)

For both of the tasks above, clearly present the solutions for the impedances of the matching network on a Smith Chart. Present clearly the R coefficient (S11) over a range of frequencies around the central operating frequency of 3.5GHz.

3. You are required to design a one-dimensional (1-D) array antenna consisting of 8 antenna elements. Assume that the array elements are omni-directional. The array will be used as part of a base station and must provide good coverage within an angular range from -45 degrees to +45 degrees (at the plane of the array). Determine the phases of the array elements and their distance for all the required array designs that produce enough beams to cover the required angular range. Aim for the minimum number of beams, as this would be a better and less complicated design than producing a large number of beams unnecessarily. Clearly present the radiation patterns of all the array designs. (25%)

Suggest a method for improving (reducing) the sidelobe level in the radiation patterns of the array (without actually implementing the method). (5%)

Hint: For a good coverage please assume that the signal should be at least at half-power of the maximum power, which is normally at the centre of each radiated main beam.

REPORT

The report should be no more than 10 pages long, including figures and appendices. You should include a title page with your full name and student ID number, as well as the module details. You should justify all your answers and calculations, describe your methodology, and interpret and discuss all results. There is no specific template for the report, but please answer each task separately, i.e. first provide a complete answer for Task 1, then for Task 2 and then Task 3.

The report shall be submitted to CANVAS by 5 pm, Friday 19 January 2024.

It is expected that all work will be carried out individually and detected cases of plagiarism will be treated according to the University’s code of practice.

SPECIFICATION TABLE

Table 1