PIN diode switch figures of merit — ON vs OFF performance Which pair best represents the standard performance metrics for a PIN-diode RF switch?

Introduction / Context:
Two headline specifications define the usefulness of an RF switch in front-ends, test systems, and phased arrays: how little loss it introduces when conducting, and how well it blocks signals when nonconducting. PIN-diode switches are no exception—these two metrics capture most application trade-offs.

Given Data / Assumptions:

• Switch types: series, shunt, or series–shunt.
• Bias states: ON (forward-biased conduction) and OFF (reverse-biased isolation).

Concept / Approach:
Insertion loss is measured in the ON state and should be as low as possible. It captures conductor loss, finite R_pi, and layout parasitics. Isolation is measured in the OFF state and should be as high as possible; it reflects the residual coupling via diode capacitance and circuit paths. Together they describe the signal-handling extremes of the switch, while other specs (P1dB, IP3, switching speed) refine selection for a project.

Step-by-Step Solution:

Verification / Alternative check:
Any RF switch datasheet tabulates “Insertion Loss (ON)” and “Isolation (OFF)” across frequency, confirming these as standard metrics.

Why Other Options Are Wrong:

• Insertion loss when OFF or isolation when ON mixes states and has no standard meaning.
• Only insertion loss or only isolation omits a critical half of performance.

Common Pitfalls:
Confusing isolation with return loss; overlooking that isolation is frequency-dependent and may need a shunt element to improve broadband blocking.

Final Answer:
insertion loss when switch is on and isolation loss when switch is off