I want to characterize the frequency inaccuracy of several silicon oscillators over temperature to see which one will work best in my end application. If I populate the oscillator on a bare-board and solder a coaxial pig-tail to the trace/GND will that suffice? Since the oscillator is designed to drive a high-impedance IC clock input, will it be able to drive the low (50Ω) impedance of the spectrum analyzer? Do I need to add some special matching, DC-block, or bypass network? I'd like to introduce the least amount of extra components possible as I'll have to take them into account in my measurements as well.
Testing Oscillator Over Temperature
frequencyfrequency-measurementoscillatortemperaturetest
Best Answer
In this case, you will want to add a buffer chip to be able to drive the 50 Ohm coax and the spectrum analyzer input. The appropriate chip depends on what type of load the oscillator is designed to drive (TTL, CMOS, ...?), the frequency, the available power supply voltages, etc.
Possibly you could use a transformer instead of an IC buffer to impedance-match the cable, but the buffer has the advantage of providing exactly the type of load the oscillator is designed for (an IC input).
Incidentally, if you want to measure the frequency accuracy of your oscillator and not other parameters, a frequency counter will give you a more accurate measurement more quickly than a spectrum analyzer. But it will still likely have a 50 Ohm input unless you're working at very low frequencies (below 1 MHz?).