Absorptive vs Reflective RF Switch: Key Differences

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

Absorptive RF Switch | Non-Reflective RF Switch

Figure 1: Absorptive RF Switch

Figure 1 depicts a functional diagram along with the pins of the RFSW6124 Absorptive RF switch from RFMD. Let’s understand the workings of an RF switch.

It’s an SPDT (Single Pole Double Throw) switch. This type is considered “non-reflective” because RF ports 1 and 2 (RF1, RF2) are both terminated when in the OFF state. The enable pin allows for an “All OFF State” terminated condition of the switch.

Here are the features of an absorptive RF Switch:

• The switch offers high isolation.
• It offers excellent power handling capability.
• It offers excellent linearity due to a high IIP3 (Third-order Intercept Point).
• It is 3V and 5V logic compatible.
• It can be used for various cellular wireless technologies such as 3G, LTE, WiMAX, etc.

Reflective RF Switch

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

The following table highlights the key comparisons between absorptive and reflective switches used in the RF and Microwave domain.

From the comparison, it’s clear that an absorptive switch can be used in place of a reflective switch, but not vice-versa.