Calculating the Sensitivity of an ASK Receiver

Abstract: The sensitivity of RFIC Amplitude Shift Keying (ASK) or On-off Keying (OOK) receivers is an important specification for designers of Remote Keyless Entry (RKE) systems, Tire Pressure Monitoring (TPM) systems, Home Automation systems, and other applications. These receivers typically operate at 315MHz or 433MHz, but the results apply to almost any carrier frequency.

It is important for the users and designers of RFICs to know the theoretical limit of these receivers so that they can determine if their design improvements are fully successful.

This application note describes a step-by-step method to predict the sensitivity of an ASK receiver, given a system noise figure, IF bandwidth, and Baseband bandwidth.

The results show that the logarithmic amplitude detection in the Received Signal Strength Indicator (RSSI) amplifier decreases the output Signal to Noise Ratio (SNR) for low input SNRs (threshold effect) and that the sensitivity increases as the square root of the IF to Baseband bandwidth ratio.\t