RF isolator attenuator

　　function

　　Attenuator is an inverse amplifier. Sometimes in wireless systems, when the signal is too large, an attenuator needs to be introduced to reduce the signal through attenuation. Attenuation is the result of insertion loss. Attenuation and insertion loss are equivalent. Attenuators allow RF engineers to install a known amount of insertion loss in the circuit.

　　type

　　Fixed attenuator

　　Attenuators can be divided into two types: fixed and variable. Fixed attenuators subject signals to a fixed amount of loss, measured in dB. Sometimes a fixed attenuator is called a constant attenuator. A typical fixed attenuator may exhibit a 3dB insertion loss, therefore a 3dB attenuator produces a signal that is half the size of the incoming signal.

　　Voltage variable attenuator

　　Another type of attenuator is called a variable attenuator. Variable attenuators allow RF engineers to control the exact amount of attenuation (insertion loss) at any time by using external controls. There are two different types of variable attenuators: voltage variable attenuators (VVA) and digital attenuators. Both are active devices.

　　The voltage variable attenuator attenuates within a given attenuation range and is controlled by an external control voltage. It is usually used in feedback connections.

　　digital attenuator

　　Another type of variable attenuator is a digital attenuator. Unlike VVA's single input control, digital attenuators have multiple input controls, each with a different attenuation value. The easiest understanding is to think of digital attenuators as a bundle of fixed attenuators, all in a row that can be switched in or out of the circuit at any time.

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