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RF and Microwave Attenuator:- About, Types, Application, Design:

RF and Microwave attenuators are passive components that are used to reduce the RF amplitude level of a signal in the circuit. There is also an active attenuator are available, which can be used to reduce the signal strength in the circuit.

  • RF and Microwave attenuators are used to protect a circuit from receiving a high RF power signal that the circuit can’t handle to process.

RFMWC- RF and Microwave Community has listed many of the top-rated RF and Microwave attenuators and manufacturers from around the world. You can check the following details in this article to select a suitable RF attenuator for your RF and Microwave project requirements.

  • What is an RF and Microwave Attenuator?
  • Types of RF Attenuator?
  • Applications of RF and Microwave Attenuator?
  • What are specifications need to consider in the selection of an Attenuator?
  • RF and Microwave Attenuator Manufacturers.

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Design and Application

What is an Attenuator and Design concept?

The attenuator is a passive resistive element used to reduce the strength in an RF and Microwave circuit. Mainly there are 5 common design typologies used in microwave attenuator circuits design.

  • The Tee.
  • The Pi.
  • The Bridged Tee.
  • The Reflection Attenuator.
  • The Balanced A.

To design, Tee, Pi, and Bridged Tee attenuator each attenuator circuit require two different value of resistors, while the balanced attenuator and reflection attenuator need only a matched pair of resistors. It will be ideal to use balanced or reflection typologies to design a variable attenuator with control voltage or current.

  • In general, depending on whether the terminations R1 is greater than or less than the system characteristic impedance Z0 there are mainly two variations of the reflection attenuator design are available.
  • The bridged tee design can be considered as a modified version of a pi network, and it is an ideal design that you can use for the variable attenuator, with FETs or with PIN diodes.

Below are the advantages of Bridge Tee design, compared to Pi and Tee  

  • The Bridge Tee design needs only two variable resistors compared to Pi and Tee needs three resistors.
  • The bridged Tee design uses the full range of resisters, resistor values, very from zero to infinity, for both the resistors (R1 and R2). For the pi attenuator, the R1 value never goes below Z0 (50 ohms) hence diodes' useful resistance range will be wasted.
  • At the high value of attenuation, the bridged Tee design has a tendency to match itself to Z0.



dB Attenuation Value   

Power Reduction

3 dB

 Half the power

6 dB

1/4 times of the input power

9 dB

1/8 times of the input power

10 dB

1/16 times of the input power

The attenuation losses tabulated for the signal power loss are theoretical values. In reality, due to imperfection in design, an additional loss will introduce into the attenuator. This loss is called "insertion loss" which need to consider along with the attenuation calculations for system design purpose.

RF and Microwave Attenuator types:

There are mainly 3 types of RF and Microwave attenuators are available for the RF design, There are, Fixed, Variable and Step Attenuators.

  • In addition, to the RF and Microwave attenuator, in RF to Optical circuit for transmitting the RF signal over the optical fibre, Optical attenuators are used in fibre optic communication links to match the optical transmitter and receiver.
  • For High-frequency applications, there are many types of waveguide attenuators are also available.

Fixed Attenuator: 

Fixed attenuators are available in connectorized as well as in the surface mount package. These are mostly passive attenuator that offers a fixed dB of attenuation in the RF circuit design chain. The connectorized attenuator is available with all types of connectors like SMA, N, TNC, etc. These fixed attenuators are available in a series of dB values of attenuation levels.

Variable Attenuators: 

In Variable Attenuators, the attenuation value can be varied using the control voltage or current. These attenuators can be regulated to provide a required attenuation level in the range is designed for. These attenuators are available in connectorized and surface mount packages.

Step Attenuators: 

In step attenuators, the attenuation level can vary in fixed steps. Variation of the attenuation can be done using the current or voltage or by using TTL control logic. These attenuators can set for any particular value in the step of the attenuation range. These Attenuators are usually available in module packages with RF connectors.


One of the prime applications of RF and Microwave attenuators is to control the gain and get a perfect impedance match in an RF circuit.

Eg: If in your circuit you are in need of 1.2:1 maximum VSWR and 10 dB gain. If you have an amplifier in the range of 12 dB gain and a lousy 2.5:1 VSWR on the output. You can use a 2 dB amplifier at the output port of the amplifier, and you can get a gain of 10 dB, and a perfect impedance match.

Some of the common applications of RF and Microwave Attenuators are as follows:-

  • Attenuators are used in broadcasting stations for volume control.
  • Fixed attenuators are used for RF circuits to protect the circuits from damages caused by high voltage / RF power.
  • In laboratories for testing purposes, attenuators are used to reduce the high power signal to low power before feeding to T&M instruments.
  • To improve the impedance matching in RF and Microwave circuits.

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Basics & Selection Feature

Main specifications need to consider in selection.

When selecting an RF and Microwave attenuator for the RF and Microwave circuit design, it is important to know the specifications that you need to consider. Below listed are the key specifications that need to consider in selecting an RF attenuator.


In RF and Microwave circuits, the attenuation level of the attenuator usually varies over the frequency range of interest. It is important to check the attenuation variation response over the entire frequency band of operation. The frequency range of an attenuator shows the frequency over which an attenuator can maintain its electrical characteristic like Attenuation level, Accuracy VSWR, etc.


Attenuation value represents the value of attenuation it can provide over the entire band of operation. We can select an attenuator on the base of the level of attenuation required for the circuit. If you are looking for a fixed attenuator, then the attenuation level in dB needs to consider. If you need to vary the attenuation value, then you need to select the variable attenuator and attenuation range that meet your requirement.

Attenuation Accuracy: 

The attenuation accuracy of an RF and Microwave attenuator indicates the dB level by which the attenuation can vary over the band of operation. Some companies present it as "Attenuation variation". An attenuator with a lower value of attenuation variation over the band needs to select for the RF design.

Power Handling:

Power handling is one of the prime factors that need to consider in the selection of an attenuator. There are different power handling ranges of FR and Microwave attenuators are available in the market. We need to select an RF attenuator, which can handle higher power than the maximum power expected to flow through the attenuator. If the power handling capability of the attenuator is less, there is a chance that the attenuator will get damaged during the operation.


RF and Microwave attenuators are designed to operate with an electrical characteristic impedance of 50 Ohms or 75 ohms. For the normal RF and Microwave application, 50 Ohms attenuator is suitable however, for the specific application like space communication, 75 ohms is quite common. As impedance matching helps to minimize reflections, it is important to select an attenuator that matches the characteristic impedance of the circuity, where it will be used.


RF and Microwave attenuators are one of the prime components of every RFMW circuit. Every designer needs to select the RF Attenuator on the base of their application by meeting all the electrical and mechanical characteristics. Below is the list of top-rated RF and Microwave manufacturers listed with RFMWC, who make the connectorized (packaged) and surface mount RF and Microwave Attenuator.

Thanks & Regards

RFMWC-RF & Microwave Community

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