Hi all, We have a problem at work where one of our engineers needs to measure the start-up chirp in an oscillator destined for a GPS application.
We are looking for ppb level frequency resolution with sample periods around 10 - 20us (yes, that's us, not ms!). The chirp is all over well inside 1ms. The measurement is on a 40MHz oscillator, which is mixed down to about 198kHz to improve resolution. We can count the down-converted frequency in a conventional manner with no problem. The problem is of course that at 198kHz the period is ~5us so even an interpolating counter will struggle. Preliminary tests with a Pendulum CNT90 counter give results that deviate +/- 16Hz when the gate time is reduced to 10us. We are using GPIB to capture multiple repeated samples, and trigger the counter when the oscillator is powered up. We also have an Agilent 53181A counter available. Any suggestions (a) how to make the measurement; (b) what is causing the counter result to degrade in this way? Thanks, Murray Greenman ZL1BPU _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
