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Introduction to Passive Devices (Power Divider, Coupler)
Date: 2024-06-13    View: 283

Passive devices are divided into linear devices and nonlinear devices.

Linear passive devices are also classified as reciprocal and non-reciprocal.

The linear reciprocity element only transforms the microwave signal without changing the frequency characteristic, and satisfies the reciprocity principle.

Usually we refer to passive devices are linear reciprocal components.

1. Power Divider

A power divider is a device that divides the energy of one output signal into two or more outputs. It's essentially an impedance converter.

Can the power divider be reversed to replace the combiner?

When used as a synthesizer, it not only needs high isolation, low standing wave ratio, but also focuses on the requirement to withstand high power.

Considering that the output ports of the commonly used cavity power splitter do not match, large standing wave; Because of the low power resistance of the microstrip power splitter, we do not recommend using the power splitter to replace the combiner.

2. Introduction to the Coupler

The coupler is a device that distributes the energy of the input signal through the coupling of electric field and magnetic field, part of which becomes the output of the coupling end, and the remaining part becomes the output end to complete the power distribution. The power distribution of the coupler is unequal.

3. Directional Coupler

Directional couplers are commonly used to sample the specified flow direction of microwave signals, the main purpose is to separate and isolate the signal, or conversely mix different signals, in the absence of internal load, directional couplers are often a four-port network.

4. Cavity Coupler

Features: Bearing high power, low loss performance.

The filling medium inside the cavity is air, and in the transmission process, the media dissipation caused by the air medium is much lower.

The coupled wire strip is generally made of a conductor with good electrical conductivity (such as silver plating on the copper surface), and the conductor loss is basically negligible. Large volume, fast heat dissipation, withstand high power.

5.3dB Bridge Description

The 3dB bridge coupler is a kind of directional coupler.

When used as a power synthesizer, the two input signals are connected to each other's isolated ports, while the coupled output and through output ports are reciprocal. If it is used as two outputs, without considering the loss, the sum of the input signal power is equally divided between the two output outlets. When used as a single-port output, the other output must be connected to match the power load to absorb the output power of the port, otherwise it will seriously affect the transmission characteristics of the system, and at the same time, it also brings additional 3dB loss, which will affect the cost and reliability of its active part for the system application.

Mainly used in the same frequency band between different carriers application. Due to the discreteness of the circuit and processing assembly, the isolation degree of the input port of the bridge coupler is relatively low, and it is not recommended to be used in the application of the combination between different frequency bands.

To sum up, in the application of different frequency combination, in addition to the phase current carrier frequency in the same frequency band (such as the phase current carrier frequency in the GSM downlink band) can only use 3dB bridge and not apply to the duplex/multiplex router, it is recommended that the duplex/multiplex router be preferred in use to improve the performance indicators of the system and increase reliability.

6. Combiner Overview

Function: Synthesize multiple signals into one signal output

Classification: Classified according to the actual co-circuit frequency band

Combiner VS Bridge VS Power Divider

Combiner: for the frequency selection combiner, in the filtered multiplexing mode, can achieve more than two signal synthesis, can achieve high isolation synthesis, mainly used in different frequency bands of the combiner, can provide the least interference between different systems.

3dB bridge: For the same frequency combination, only two signal synthesis can be achieved, the isolation is low, and two equal amplitude output can be achieved.

Power splitter (synthesizer) : for the same frequency, can achieve multiple synthesis, low isolation, can only provide one output.

Kete Microwave Electronics Co., Ltd. specializes in designing and manufacturing state of the art RF/Microwave passive components solution. The primary products lines include ferrite components (RF Isolator, RF Circulator), High Power Resistive Components (RF Resistor, Coaxial Fixed Attenuators & Termination), Feedthrough Capacitor (EMI RF Filter), Microwave Power Divider and RF Filter.

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