I'm attempting to measure the RMS value of a 76 MHz carrier signal. The amplitude should be entirely from random noise, however I'd like to modulate a source of the noise at ~50 kHz thereby changing the RMS value at 50 kHz. The goal is to isolate the modulated source of noise and directly measure it's RMS amplitude. I plan to use a lock-in amplifier to detect the 50 kHz modulation from the boards output.
On page 19 of the data sheet for ADL5511 "Operation below 1 GHz/Envelope Filtering" it appears that I can leave C_fltr1 alone since my 76 MHz is > 32 MHz. However, the output corner frequency of the evaluation board at FLTR4 is ~4 kHz with C_fltr4 = 100 nF. Therefore I plan to change the capacitance to 1 nF which should give me > 100 kHz output bandwidth.
- Is there a better chip/board for my planned measurement?
- Is there a preferred type of capacitor (e.g. ceramic, etc.) that will be the best choice for C_fltr4?
Thanks in advance!