Application of Residue Sampling to RF/AMS Device Testing

This paper describes the application of our previously proposed residue sampling circuit to RF/Analog Mixed-Signal (AMS) device testing. The residue sampling circuit provides high-frequency signal estimation using multiple low-frequency sampling circuits following an analog Hilbert filter and ADCs; the sampling frequencies are relatively prime. It is based on aliasing phenomena in the frequency domain for waveform sampling and the residue number theory. A high frequency cosine wave is provided as an input signal. Cosine and sine signals with the same frequency are generated by an analog Hilbert filter and are fed into sampling circuits with different (relatively prime) low sampling frequencies. Their analog outputs are analog-to-digital converted and complex FFT is performed on both. Since the high frequency signal is sampled with low frequency clocks, aliasing (spectrum folding) occurs. However, each aliased frequency is different because each sampling clock frequency is different in the sampling circuits. Based on the Chinese remainder theorem, this difference allows the input frequency to be estimated. High frequency resolution can be achieved over long time periods and large numbers of FFT points. We consider here applications to RF/AMS device testing; (i) two tone testing for high frequency narrow band devices, (ii) wireless communication device testing such as LTE, Bluetooth and (iii) wideband analog filter frequency characteristics testing. These considerations are supported by simulations.