How do I perform a failure mode effects and criticality analysis for an RF subsystem?

A Failure Mode, Effects, and Criticality Analysis (FMECA) is a systematic engineering methodology for identifying potential failure modes in an RF subsystem, assessing their effects on system operation, and prioritizing them by criticality: (1) Process steps: step 1: define the system and its functional blocks. Break the RF subsystem into its constituent elements: PA, LNA, filters, mixers, LO, power supply, antenna, cables, connectors, etc. Step 2: identify failure modes for each element. For each component, list all possible failure modes: open circuit, short circuit, parametric degradation (gain drop, NF increase, frequency shift), intermittent operation, and excessive leakage or PIM. Step 3: determine the effect of each failure mode. Local effect: what happens to the component itself? Next-higher effect: what happens to the subsystem containing the component? End effect: what happens to the overall system or mission? Example: PA output transistor fails short: local effect = PA output drops to zero, next-higher = transmitter output is zero, end effect = radar cannot transmit (mission failure). Step 4: assign severity classification. Category I (Catastrophic): could cause death or system loss. Category II (Critical): could cause mission failure or major damage. Category III (Marginal): degraded performance but mission can continue. Category IV (Minor): no significant impact on performance. Step 5: estimate the failure mode probability. Use component failure rates from MIL-HDBK-217F or manufacturer data. Assign the probability of each failure mode as a fraction of the total component failure rate. Example: an RF transistor has failure rate λ = 500 FIT. 40% of failures are open circuit (200 FIT), 30% are short circuit (150 FIT), 30% are parametric degradation (150 FIT). Step 6: calculate the criticality number. C_n = λ × α × β × t. Where λ = failure rate, α = failure mode ratio (fraction of failures that are this mode), β = conditional probability that the failure causes the end effect (1.0 for certain, 0 for impossible), and t = operating time (hours). Step 7: rank failure modes by criticality and address the highest-criticality items first with design improvements, redundancy, or BIT coverage.