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Gain and phase measurement using AD8302 IC

Question asked by anushaas on Sep 16, 2015
Latest reply on Nov 18, 2015 by jdobler


I am using an AD8302 RF/IF Gain Phase detector to measure the gain and phase of two input signals within a varying frequency range of 1Hz to 1MHz. It is mentioned in the application note AN-691 that the IC need to be used in the following configuration to enable its use in low frequency applications:


I gave a +5V supply to the IC and used CC = 10uF ,CFLT = 1uF. Also R1= R2 was chosen as 51.9 Ohm.

The input signals were VINA = VF1 and VINB =VF2 as shown in the following circuit:


As per the datasheet of AD8302,the gain and phase measurements are related to the voltage outputs as:


where VCP =900 mV,RFISLP = 600 mV/decade and RFIQ = 10mV/degree at low frequencies.

I acquired a Bode plot of the same circuit using the Bode analyser of NI ELVIS II+ and also obtained the Gain in dB and Phase in degrees using the above equations from the AD8302 output voltages.

The measurements are graphically represented as below:



Can anyone please suggest ways to improve the performance of AD8302 in the frequency range of 1Hz to 1MHz and there by reduce the error in the gain and phase measurements?