How much bandwidth, size, budget, etc. are we talking here?
Tim
I always struggle with the budget question - it comes down to what exactly can be done like when you go to buy a car with a budget in mind and the see something nearly twice the price that you didn't know existed and is the thing you absolutely must have
Anyway, breaking the system down into its different sections:
RFThis is what I asked about a few weeks ago and you kindly provided an almost perfect fit.
2 x RF power amps delivering +32dBm into a 50ohm load. Frequency = 40+/-1MHz. The inputs come from a DDS generator. The one I use at the moment generates about 1Vpk sine.
Photodetector signalThe output is a broadband signal due to lots of noise in the MHz region. The signal of interest is typical 1-50kHz. The AC component ranges from approx. 1 - 10mV at has a large DC component (>1V). Currently, I pass the signal through an 8-pole Sallen-Key bandpass filter (2kHz/30kHz) with +40dB gain.
Quadrature detectionThe filtered and amplified detector signal is demodulated by two quadrature multiplier ICs and low-pass filtered before going to an ADC sampling typically between 8kHz and 32kHz.
DUT impedance analysisThere's a low frequency square or sine voltage signal from a FeelTech DDS that ranges DC-1kHz and up to 20Vpp connected across the DUT whose impedance ranges from ~500kohm down to ~10ohm. Current is measured with a uCurrent device. Right now, there are six signals fed to the ADC which has to be simultaneous sample-and-hold. The digitized data are transferred via USB in the background to permit real-time analysis.
My primary goal at the moment is miniaturization.