A circulator is a waveguide device with multiple input and output ports with the property that any wave entering the circulator via a particular port will only be able to exit the circulator via the port immediately to its right (for right-handed circulators), or to its left (for left-handed circulators).

The key element inside the circulator is a graphite triangle that acts as a prism refracting the incoming wave to the appropriate output port.

The graphite triangle refracts the incoming wave by shifting its phase, thus D. is the right answer.

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In a waveguide the electrical field lines form along the waveguide whereas the magnetic field lines form accross the waveguide.

A circular resonant cavity acts as a short waveguide, so here too the electrical field lines form along the waveguide and enter the flat surfaces at each end perpendicularly, thus Answer B. is the right answer.

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A ferrite circulator is most commonly used in the duplexer portion of a RADAR system.

The duplexer is a device that allows the sharing of a single antenna between the transmitter and receiver in a RADAR system. It enables the transmission of high-power pulses from the transmitter while providing isolation to protect the receiver from the transmitted energy.

A ferrite circulator is a key component within the duplexer. It utilizes the unique properties of ferrite material to control the flow of RF signals. The ferrite circulator facilitates the separation of the transmitted and received signals, ensuring that the high-power transmitted pulse is directed towards the antenna while allowing the weaker echo signals from the target to be received by the receiver.

The circulator accomplishes this by utilizing the non-reciprocal properties of ferrite material, which allow signals to flow in a specific direction while isolating the other ports. This ensures that the transmitted power is effectively directed towards the antenna and prevents it from reaching the receiver.

Mnemonic: "Duplexer Defender"

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A circulator is a waveguide device with multiple input and output ports with the property that any wave entering the circulator via a particular port will only be able to exit the circulator via the port immediately to its right (for right-handed circulators), or to its left (for left-handed circulators).

The key element inside the circulator is a graphite triangle that acts as a prism refracting the incoming wave to the appropriate output port.

A three-port circulator can thus be used as a duplexer instead of the TR Cell as follows:

For a right-hand circulator, transmitter radar pulses enter the circulator via Port 1 and can only exit to the antenna via Port 2 to its right.

Radar echos received by the antenna enter the circulator via Port 2 and exit the circulator to the receiver via Port 3 on its right.

Transmitter pulses cannot reach the receiver because the receiver is connected to the circulator via a Port 3 and Port 3 is on the left of Port 1, the port the transmitter is connected to, thus the RF will be blocked from passing by the circulator.

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Attenuation = -30dB, Wout = 100mW, Win = ?

dB = 10 log (Wout / Win)

dB / 10 = log (Wout / Win)

10^(dB / 10) = Wout / Win

Win = Wout / 10^(dB / 10)

Win = 0.1W / 10^(-30dB / 10)

Win = 0.1W / 10^(-3B)

Win = 0.1W / 0.001

Win = 100W

Answer B. is the right answer.

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A Duplexer is a “switch” that you can use to connect an antenna to two components.

The Duplexer makes sure the RF generated by the transmitter will only go to the antenna and not the receiver and the signals received by the antenna will only go to the receiver and not the transmitter thus Answer A. is the right answer.

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