# Why do waveguides have a cutoff frequency?

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## Why do waveguides have a cutoff frequency?

Waveguides will only carry or propagate signals above a certain frequency, known as the cut-off frequency. Below the waveguide cutoff frequency, it is not able to carry the signals. In order to carry signals a waveguide needs to be able to propagate the signals and this is dependent upon the wavelength of the signal.

## What is cut off frequency in rectangular waveguide?

The cut-off frequency is the frequency above which the waveguide offers minimum attenuation to the propagation of the signal. Frequencies below the cut-off frequency are attenuated by the waveguide. The dominant mode in a waveguide is the propagation mode with the lowest cut-off frequency.

## What frequency do waveguides use?

In general, waveguides begin to be useful between around 1 GHz and operate several hundred GHz (beyond that, you are in terahertz region, between the RF and optical parts of the spectrum).

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## Why are waveguides usually used at frequencies of several GHz and higher?

Due to propagation of energy in mostly air or space within the waveguide, it is one of the lowest loss transmission line types and highly preferred for high frequency applications where most other types of transmission structures introduce large losses.

## Why waveguides are not used in low frequency?

For reflection to work, the wavelength of the wave needs to be smaller than the smallest dimension of the waveguide. Otherwise, the wave will diffract i.e it will bend round the edges of the waveguide, where it interfaces with connectors. At low frequencies, this means that the waveguide dimensions must be very large.

## Why waveguides are used at MW frequencies?

In a microwave oven a waveguide transfers power from the magnetron, where waves are formed, to the cooking chamber. In a radar, a waveguide transfers radio frequency energy to and from the antenna, where the impedance needs to be matched for efficient power transmission (see below).

## Why are waveguides used?

Waveguides are used to direct and propagate Electromagnetic waves from one point to another. They are generally used to transmit high frequency waves such as Microwaves, Radio waves, Infrared waves etc. For low frequency waves which are less than 1 MHz, parallel transmission lines or co-axial cables are used.

## Why waveguide is not used for transmission of electromagnetic energy at lower frequency range?

Wave guides conduct microwave energy at lower loss than coaxial cables. Waveguides are practical only for signals of extremely high frequency, where the wavelength approaches the cross-sectional dimensions of the waveguide. Below such frequencies, waveguides are useless as electrical transmission lines.

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## Why the frequencies below 30 MHz can not be used for cellular communication?

The radio frequencies above 30 MHz has the tendency to penetrate the ionosphere making them unsuitable for long distance propagation. So, the range of frequencies from 30 to 300 MHz (also 300 MHz and above), which are placed under the Very High Frequency (VHF) category are mainly used for line-of-sightline-of-sightThe radio horizon is the locus of points at which direct rays from an antenna are tangential to the surface of the Earth. If the Earth were a perfect sphere without an atmosphere, the radio horizon would be a circle.https://en.wikipedia.org › wiki › Line-of-sight_propagationLine-of-sight propagation – Wikipedia communication.

## Why waveguides are preferred at microwave frequencies?

Generally, if the frequency of a signal or a particular band of signals is high, the bandwidth utilization is high as the signal provides more space for other signals to get accumulated. A waveguide is generally preferred in microwave communications.

## What is the wavelength of a wave in a waveguide?

The wavelength in a waveguide is considered as a wavelength in a direction of wave propagation and its dependence on wave frequency is defined as follows: where l0 is a wavelength in a free space at a given frequency and lc stands for the cutoff wavelength for a given waveguide dimensions and waveguide mode.

## How do you find the wavelength of a waveguide?

The corresponding wavelength, called the guide wavelength, is denoted by λg =2π/β .

## What is waveguide cutoff wavelength?

The number of guided modes of a waveguide (for example, an optical fiber) depends on the optical wavelength: the shorter the wavelength, the more modes can be guided. When a particular mode ceases to exist beyond a certain wavelength, that wavelength is called its cut-off wavelength. 