H-Plane Tee

We have studied microwave engineering an essential branch of electronics that involves the use of different devices. In this article, we will study one such device which is H-Plane Tee. H-Plane Tee is a junction which is formed by joining two waveguides together. We will study the H-Plane Tee by looking at its properties and structure. It is advised that the students already go through E-Plane Tee to have a basic understanding of tees.

We will also see how an H-plane Tee operates. In addition to this, we will study the H-Plane Tee Circuit Model and its use in various feed systems. We will study the advantages, disadvantages, and applications of H-Plane Tee. The article will conclude with frequently asked questions that users can refer to.

What is an H-plane Tee?

An H-plane Tee also known as a waveguide Tee is a device that connects a simple waveguide to a rectangular waveguide. Note that this waveguide already has two ports. The figure given below represents a basic H-plane Tee.

H-plane Tee

In an H-plane Tee, the axis of the side arm is parallel to the Magnetic Field (H) of the collinear arms which is a critical property of this device. From the diagram, we can say that the H-plane Tee is a 3-port device, the two ports are of the rectangular waveguide and the third port is due to the side arm.

Properties of H-Plane Tee

We will use S-parameters or scattering parameters to understand the properties of H-Plane tee which is used for devices working on microwave frequencies. Since H-Plane Tee is a 3 port device, we can generate a 3⨯3 scattering matrix to represent the properties of H-Plane Tee.

Note that, S_ij depicts the relation between the i^th and the j^th port of the Tee.

Let there be a matrix S

S= [S₁₁ S₁₂ S₁₃ ]

. [S₂₁ S₂₂ S₂₃ ]

[S₃₁ S₃₂ S₃₃] Eq 1

In an H-Plane matrix, the output at ports 1 and 2 when input is fed at port 3 is same due to symmetry therefore, we can say that

S₁₃=S₂₃ Eq 2

Since port 3 is perfectly matched to the junction, we can say by the properties of the matched junction that

S₃₃=0 Eq 3

From the symmetric property S_ij=S_ji so

S₁₂=S₂₁ S₂₃=S₃₂ S₁₃=S₃₁ Eq 4

From the equations obtained above, we can rewrite the matrix S as

S= [S₁₁ S₁₂ S₁₃ ]

[S₁₂ S₂₂ S₁₃ ]

[S₁₃ S₁₃ 0] Eq 5

In this matrix, we have 4 unknowns. Now from the unitary property of lossless medium,

[S][S]*=[I]

Therefore [S₁₁ S₁₂ S₁₃ ] [S₁₁* S₁₂* S₁₃*] = [1 0 0]

[S₁₂ S₂₂ S₁₃ ] [S₁₂* S₂₂* S₁₃* ] = [0 1 0]

[S₁₃ S₁₃ 0 ] [S₁₃* S₁₃* 0 ] = [0 0 1]

On multiplying the matrix and equating the terms, we get

S₁₁S₁₁*+ S₁₂S₁₂*+S₁₃S₁₃*=1

∴ |S₁₁|²+ |S₁₂|²+ |S₁₃|²=1 Eq 6

Similarly

∴ |S₁₂|²+ |S₂₂|²+ |S₁₃|²=1 Eq 7

∴ |S₁₃|²+|S₁₃|² = 1 Eq 8

∴ S₁₃S₁₁*- S₁₃S₁₂*=0 Eq 9

Now, we will equate the equations to derive relations

2|S₁₃|² =1

∴ S₁₃ =1/ √2

From eq 9

S₁₁= -S₁₂ Eq 12

Using eq 10,11,12 in eq 6

|S₁₁|²+ |S₁₁|²+ 1/2 =1

∴ |S₁₁|=1/2

Therefore |S₁₂|=-1/2 and |S₂₂|=1/2

The final scattering matrix after substitution is

[S]= [ 1/2 -1/2 1/√2 ]

[ -1/2 1/2 1/√2 ]

[1/√2 1/√2 0 ]

This is known as the scattering matrix of H-plane Tee which is used to study the properties of H-plane Tee.

H-Plane Tee Structure

Given below is the structure of the H-Plane Tee

Structure of H-Plane Tee

An H-Plane Tee consists of one rectangular waveguide having two ports known as port 1 and port- 2, The waveguide which is connected to the original waveguide installs another port called port-3. There are mainly two parts in H-Plane Tee

Side Arm: The new arm due to the additional waveguide is called the side arm or the H arm. It has a 3rd port i.e. port 3 on it. This arm has axis parallel to magnetic field of side collinear arms.

Collinear Arms: As the name suggests, these arms lie on the same line , on either side of rectangular waveguide. Port 1 and Port 2 lie on this arm. It is called collinear because both the ports lie on the same line i.e. these ports are collinear.

H-Plane Tee Operation

Let us now understand how the H-Plane tee operates with the help of a diagram.

H-Plane Tee

Based on the properties of waveguide, we have studied that it is useful for dealing with electromagnetic waves that use microwave frequencies. In an H-plane Tee, the junction is a combination of a waveguide which is attached perpendicular to two parallel waveguide

• The design of the H-plane Tee is such that it consists of a horizontal waveguide with a perpendicular waveguide attached to form a ‘T’ shape. This shape allows to combine and divide various input signals.
• When two input signals are sent through the two ports of H-plane Tee, then they can be successfully combined by the tee with minimum energy loss to obtain the final energy signal through the third port.
• In another case, if the input is fed at any one port then the H-Plane Tee will perform the task of splitting this input wave equally at the junction and thus two waves of equal magnitude with equal phase will be given as output from other two ports.

H-Plane Tee Circuit Model

Here is a circuit to illustrate the H-Plane Tee in a circuit

H-Plane Tee

The simplest circuit model of H-plane tee consists of three ports, one port is input port, second port is output port and third port is a coupled port. Let us see how this circuit works:

• The electromagnetic wave enters the port 1 of the h-plane tee. After this the input energy of the signal is divided depending on the coupling coefficients of the tee.
• One part of input signal energy is sent to the branch waveguide (port 3) and rest of the energy is sent to the output port (port 2). Note that these two signals are independent and the tee ensures no coupling between them.
• The tee is then further integrated into the circuit using devices like attenuators, phase shifters, or filters depending on our requirement from the tee. It is necessary to ensure that the tee works optimally and generates the required output.

H-Plane Tee in Antenna Feed Systems

One major applications of H-Plane Tee is its use in antenna Feed Systems where it serves different purposes. Let us study them

• The H-plane tee is used as a power splitter in Antenna Feed Systems. Since it is capable of splitting the input power efficiently into two parts, therefore it is used to feed the antenna elements.
• The H-plane tee is used to balance the feeding of networks. Balanced feed as the name suggests represents a feed that is balanced due to equal and opposite current. This is done to minimize any noise.
• The H-plane tee is used to control the phase of the antenna feed system. S-Plane Tee is a device used to distribute the incoming wave in different directions, it allows to control the phase developed across the antenna elements.
• The H-plane tee is used to isolate the elements of antenna. The element isolation allows to prevent any unwanted coupling between the elements. This is necessary to enhance the performance of the antenna.

H-Plane Tee in Network Analyzers

Network analyzers can be described as electrical instruments that are used to study the electrical characteristics of various components and networks. let us see how we can use H-Plane Tee to enhance the overall performance of Network Analyzers

• The H-plane tee is used for setting the calibration standard of various devices. This is necessary to ensure that the measurements being made are free of errors and it gives us a standard to which the characteristics of network analyzer can be matched.
• The H-plane tee is used for impedance matching purposes in network analyzer. This generally involves using H-plane tee to match the impedance of device to the characteristic impedance of transmission line.
• The H-plane tee is used for measuring the S parameters in network analyzers. By positioning the device at the different ports of the tee, we can measure the parameter values of S₁₁, S₁₂ and more.

Overall, using H-plane Tee in network analyzers can enhance the accuracy and therefore the performance.

Advantages of H-Plane Tee

Let us see some advantages of the H-Plane Tee

• H-Plane Tee serves two purposes in a single device. It can be used as tee and a waveguide, making it an ideal choice for combining and splitting the signal power. This is a major requirement when dealing with microwave signals.
• One major advantage of the H-Plane Tee is the low-cross coupling between the arms. By minimizing the coupling between any two arms, it can minimize the insertion loss.
• The H-plane tee when designed carefully can operate over large range of frequencies making them a good choice for large number of applications over wide frequency range.
• The simple and compact design of the H-Plane Tee is useful since it allows easy integration of this tee in microwave circuits with cost-effective methods.
• H-plane tees are versatile since they can be used for different appliances that work in the microwave range. These applications are covered in the later section.

Disadvantages of H-Plane Tee

Let us see some disadvantages of the H-Plane Tee

• H-Plane Tee can provide isolation to a large extent but it can’t provide perfect isolation. In practical scenarios, some extent of isolation is always present degrading the performance.
• The management of tee in high-power appliances can be a difficult task. High-power appliance have certain restrictions and the design of the tee complicates with it.
• Certain devices in which size is the major issue might not be able to integrate H-plane tee since the diemensions of tee can be large considering the appliances.
• H-Plane Tee is a frequency dependent device meaning it can operate only in a certain range. In the case of ranges outside the desired range, the Tee might suffer from significant damage which can cause permanent loss of the device.
• The H-plane tee is sensitive to certain disturbances. Any mechanical disturbance like vibrations, fields etc can affect the performance of the tee for the worse.

Applications of H-Plane Tee

Let us see some applications of H-Plane Tee

• H-Plane Tee is commonly used as power dividers for frequencies ranging around microwave range. It can combine or split signals of microwave frequencies.
• H-Plane Tees are used to form antenna-feeding networks. Here, they are used for distribution of signal to multiple array elements by controlling the output signal.
• The H-plane tee is widely to make directional couplers. This is necessary since it helps to monitor a signal using coupling and without affecting the original signal.
• H-Plane Tees are employed in making more efficient devices like magic Tee which is a hybrid Tee made of E-Plane Tee and H-Plane Tee.
• The H-plane tee is used in satellite communication where they are specifically employed in ground stations to combine and divide the signal depending on the requirement.

Conclusion

We have seen how H-Plane Tee is one of the major components used in electronics engineering for different purposes. H-plane tee is specially used for splitting or combining the incoming waves with minimum loss of original signal. We have studied how H-Plane Tee operates and serves different purposes. In addition to this, we also saw how it works in a circuit.

The following section of the article talked about the application of H-Plane Tee in Antenna Feed Systems and various other network analyzers. The H-Plane Tee has advantages as well as some limitations like a insertion loss. Readers are advised to refer to the frequently asked questions to ensure better clarity of concept.

H-Plane Tee – FAQs

Why is H-Plane Tee called Shunt Tee?

The H-Plane Tee is called shunt Tee because of its configuration. The axis of the side arm is parallel to the magnetic field giving it the name “shunt” Tee.

What is the difference between E-Plane and H-Plane Tee?

The main difference between E-Plane and H-Plane Tee is the difference in their design . In E-plane tee, the electric field vector is parallel to the plane of the junction, and in H-plane tee, the magnetic field vector is parallel to the plane of the junction.

What is a hybrid Tee and how is made?

A hybrid Tee is a four-port junction. It is a combination of E-Plane Tee and H-Plane Tee and provides combined features of the two Tees.