# [HFSS] Design of a T-junction magic tee with four ports

2021-10-14 04:37:23

## Experiment 1: Design of a T-junction magic tee with four ports

Record microwave operation , Starts from me

### Part 1: Introduction.

A T-junction magic tee (or waveguide hybrid junction) is a kind of 180∘180^{\circ}180 hybrid junction used in microwave systems. It is a 4-port waveguide structure that behaves as an electric field 3dB3dB3dB coupler, which is a combination of E-plane and H-plane tees.

In our daily life, magic Tee is widely used in the field of microwave engineering and communication engineering. It can always used as a duplexer or a mixer. Moreover, it can be used as a microwave bridge or a discriminator etc. In short, it is significantly important to learn about the interior structure of a magic tee and understand its basic principles.

In this lab we will focus on the design of a magic tee model using HFSS. We will also analyze 3​ different cases of operating a Magic Tee. We will both give a rectangular plot of S-parameter and a field overlay plot for each case.

### Part 2: Schematic & Model in this experiment.

#### 2.1 Schematic:

Schematic in this lab is shown in the Fig.1 below. There are 444 ports for this schematic:

• Port 1- Sum Port ("∑\sum")
• Port 2- Co-linear
• Port 3 - Co-linear
• Port 4 - Difference Port ("Δ\DeltaΔ")
Fig.1 Schematic in this lab

#### 2.2 Model：

According to the given data, we can draw a model below:

Fig.2 Magic Tee Model

Three views for this model:

Fig.3 Three Views

### Part 3: Result & Analysis.

#### 3.0 Three cases.

Since these four ports could all be used as inputs, there are 3 cases of operating a Magic Tee:

• Case 1: Set Port 1 ("∑\sum") as a source.
• Case 2: Set Port 4 ("Δ\DeltaΔ") as a source.
• Case 3: Set Port 2,3 as sources.
• (a) The magnitudes of signals excited on the Port 2 and Port 3 are equal;

• (b) The magnitudes of signals excited on the Port 2 and Port 3 are not equal;

#### 3.1 Set Port 1 ("∑\sum∑") as a source.

Rectangular Plot Of S-Parameter:

Fig.4 Rectangular Plot Of S-Parameter for Case 1

field overlay plot:

Fig.5 Field Overlay Plot For Case 1

Analysis:

If the input is applied to Port 1, this signal will split equally into two components at Ports 2 and 3, and the Port 4 will be isolated. No outputs come from Port 4.

#### 3.2 Set Port 4 ("Δ\DeltaΔ") as a source.

Rectangular Plot Of S-Parameter:

Fig.6 Rectangular Plot Of S-Parameter for Case 2

field overlay plot:

Fig.7 Field Overlay Plot For Case 2

Analysis:

If the input is applied to Port 4, this signal will split equally into two components at Ports 2 and 3, and the Port 1 will be isolated. No outputs come from Port 1.

#### 3.3 Set Port 2,3 as sources.

• (a) The magnitudes of signals excited on the Port 2 and Port 3 are equal:

Rectangular Plot Of S-Parameter:

Fig.8 Rectangular Plot Of S-Parameter for Case 3 (a)

field overlay plot:

Fig.9 Field Overlay Plot For Case 3 (a)

Analysis:

If equivalent inputs are applied at Ports 2 and 3, the Magic Tee will work as a combiner, the sum of Ports 2 and 3 will be formed at Port 1, the difference of Ports 2 and 3 will be formed at Port 4 which is zero indicating that no outputs come from Port 4.

• (b) The magnitudes of signals excited on the Port 2 and Port 3 are not equal:

Magnitude of signals excited at Ports 2 and 3 in this situation:

Fig.10 Parameters Set For This Situation

Rectangular Plot Of S-Parameter:

Fig.11 Rectangular Plot Of S-Parameter for Case 3 (b)

field overlay plot:

Fig.12 Field Overlay Plot For Case 3 (b)

Analysis:

If different-valued inputs are applied at Ports 2 and 3, the Magic Tee will work as a combiner, the sum of Ports 2 and 3 will be formed at Port 1, the difference of Ports 2 and 3 will be formed at Port 4 .

### Part 4: Summary.

• If the input is applied at Port 1, the signal split equally to Ports 2 and 3, and no outputs come from Port 1;
• If the input is applied at Port 4, the signal split equally to Ports 2 and 3, and no outputs come from Port 4;
• If equivalent inputs applied at Ports 2 and 3, the sum will be formed at Port 1, and the difference (zero) will be formed at Port 4;

Fig.13 A Magic Tee Junction with Four Ports

### Part 4: Experience.

• Using ANSYS Electronics Desktop to model for the first time is quite struggling but also interesting;