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Absorptive RF Switch vs Reflective RF Switch | Difference between Absorptive RF Switch and Reflective RF Switch

This page compares Absorptive RF Switch vs Reflective RF Switch and mentions difference between Absorptive RF Switch and Reflective RF Switch.

Absorptive RF Switch | Non Reflective RF Switch

Absorptive RF Switch

The figure-1 depicts functional diagram along with pins of RFSW6124 Absorptive RF switch from RFMD. Let us understand working of RF switch. It is SPDT type (Single Pole Double Throw) switch. This non reflective type due to the fact that RF ports 1 and 2 (RF1, RF2) are both terminated in the OFF state condition. The enable pin allows "All OFF State" terminated condition of the switch.

Following are the features of absorptive RF Switch.
• The switch offers high isolation.
• It offers excellent power handling capability.
• It offers excellent linearity due to high IIP3.
• It is 3V and 5V logic compatible switch.
• It can be used for various cellular wireless technologies such as 3G, LTE, WiMAX etc.

Reflective RF Switch

• These switches leave unused port as unterminated.
• In this switch, impedance of port which is OFF is not 50 Ohm and hence will have very high VSWR.
• They are further categorized into reflective open and reflective short types.
• It conducts RF power when diode is reverse biased.
• It reflects RF power when diode is forward biased.
• Due to its reflective property it is known as reflective RF Switch.

Following table mentions comparison between absorptive switch and reflective switch used in RF and Microwave domain.

Features Absorptive RF Switch Reflective RF Switch
VSWR Good i.e. low Poor i.e. high
Impedance when OFF It offers good VSWR on all the ports irrespective of state of the switch i.e. ON or OFF. This is because it incorporates 50 Ohm termination at each output ports in ON/OFF states. It does not offer exact 50 Ohm at the ports during OFF state. This results into higher VSWR.

From the comparison, it is imperative that absorptive switch can be used in place of reflective switch but not vice versa.


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