Definition
Insertion loss is the reduction in signal power caused by inserting the selected switch path into the RF chain. It is expressed in dB and includes conductor, contact, connector and dielectric losses.
Why small losses matter
A fraction of a decibel can be important ahead of a low-noise receiver, in a high-power transmit path or in a long cascaded network. Multiple switches, cables and adapters add to the total link loss.
Frequency dependence
Insertion loss typically rises as frequency increases. Compare the maximum specified loss in each frequency band with the system link budget rather than relying on a low-frequency value.
Receiver impact
Loss placed before a low-noise amplifier directly degrades the effective noise performance of the receive chain. This makes low insertion loss particularly valuable in sensitive front ends.
Transmitter impact
In a transmit chain, insertion loss reduces delivered RF power and causes some power to be dissipated as heat. At high power, connector quality, contact resistance and thermal design become important.
Measurement
Insertion loss is commonly characterized with a vector network analyzer after suitable calibration. Production measurements should use stable cables, correct connector torque and a repeatable reference plane.
Key takeaway
Insertion loss belongs in the complete RF link budget and becomes especially important ahead of sensitive receivers.