Built-in RFIC inter-modulation testing using sub-sampled monobit kernel function

The inter-modulation testing of radio frequency (RF) integrated circuits usually requires full-blown fast Fourier transform (FFT) engines for frequency domain characterization. Thus, the built-in inter-modulation testing is prohibited due to the excessive computation to be conducted on-chip. This paper proposes a novel spectrum evaluating algorithm which subsamples the signal with sampling frequency adjusted according to the frequency point to be evaluated. The kernel functions for Fourier transform calculation at this point are all monobit (+1 or -1) to allow the evaluation of its frequency response with significant reduction in computation. The circuit architecture using this algorithm is proposed and an example of third-order inter-modulation (IM3) evaluation of a 2.4GHz low noise amplifier (LNA) is shown. Simulation results reveal maximum 0.6% IM3 tone amplitude estimation error of the proposed algorithm using 10-bit 100Ms/s analog to digital converter (ADC).