# Finding Ratio of Lowest Cutoff Frequencies for Waveguide - Quick Question

• rabbit44
In summary, the conversation is regarding finding the ratio of the lowest TM cutoff frequency to the lowest TE cutoff frequency in a rectangular waveguide. The person has derived the general form of the cutoff frequency and has noticed that taking TE10 and TM11 gives the correct answer. They are wondering why TM10 cannot be taken and are asking for clarification on the components of the electric field along the axis of the waveguide for TM10 and TM01.

## Homework Statement

I have to find the ratio of the lowest TM cutoff frequency to the lowest TE cutoff frequency.

## The Attempt at a Solution

I have derived the general form of the cutoff frequency (which seems to be the same for both). I get the right answer if I take TE10 and TM11; but why is this? I know why you can't have TE00 or TM00, but why can't TM take TM10?

Thanks

What shape waveguide is this in reference to?

Assuming you are talking about a rectangular waveguide, what happens to the component of the electric field along the axis of the waveguide for TM10 and TM01? What does that make all the other components? Are those really TM modes?

## 1. What is a waveguide?

A waveguide is a structure that is used to guide and transmit electromagnetic waves, such as radio waves, microwaves, and light. It is typically made of a hollow metal tube or dielectric material and is used in various devices, such as antennas, radar systems, and optical fibers.

## 2. How does a waveguide work?

A waveguide works by confining and directing electromagnetic waves along its length. This is achieved by reflecting the waves off the inner walls of the waveguide, which act as mirrors, while also minimizing energy loss through absorption.

## 3. What are the advantages of using a waveguide?

The main advantage of using a waveguide is that it allows for the transmission of electromagnetic waves with minimal energy loss. This is particularly useful for high-frequency signals that cannot be efficiently transmitted through traditional wires. Additionally, waveguides are also compact, lightweight, and have a high power handling capacity.

## 4. Can a waveguide be used for all types of electromagnetic waves?

No, waveguides are designed to work with specific frequency ranges and are not suitable for all types of electromagnetic waves. For example, a waveguide designed for microwaves will not work with visible light. Different types of waveguides are used for different frequency ranges.

## 5. Are there any limitations to using a waveguide?

Yes, waveguides do have some limitations. One of the main limitations is their size, as they need to be a certain length to efficiently guide certain frequencies. Additionally, waveguides can only transmit one type of polarization, and they can be affected by environmental factors, such as temperature and humidity, which can impact their performance.