Frequency/phase movement analysis by orthogonal demodulation [mixed signal SOC testing]

In mixed signal system-on-a-chip (SOC) testing, there are many opportunities to measure phase and frequency change of signals. For instance, in a PLL circuit, the lock up time is one of most typical test items. In a read/write channel device for hard disc drives, small pulse shifts for write pre-compensation are tested. Clock jitter is often evaluated in data transmission and storage devices. Since this kind of measurement needs a time stamp measurement, in general, a time interval analyzer (TIA) or a time measurement instrument is applied to do the tests. If the input frequency range of the available TIA is not high enough for the test signal, real-time digitizers having higher sampling rates than the TIA do precise time stamp measurement. The digitized data is processed with an orthogonal demodulation method, and its instantaneous phase/frequency trend is extracted. Swept frequencies, phase-shifted clocks, shifted pulses, shifted edges and clock jitter are analyzed by this method.