1、before measurement, it is necessary to pass high precision the resistance is calibrated;

2、Measure each frame I, Q data first through the calibration formula to calculate the measured resistance value and reactance value, and then calculate the impedance amplitude and phase Angle. Calibration formula is as follows, including 𝐼_𝑅 and 𝑄_𝑅 are 𝑅_𝑅𝐸𝐹 measurements (calibration process obtained average) , 𝑅_𝑅𝐸𝐹 = 1000, 𝐼_𝑅𝑥 and 𝑄_𝑅𝑥 for measurement of the resistance under test, 𝐼_𝐶𝑎𝑙 and 𝑄_𝐶𝑎𝑙 are the real part (resistance value) and imaginary part (reactance value) of the resistance to be measured after calibration.

I_c = (I_R*R_REF)/(I_R² + Q_R²)

Qc = -(Q_R*R_REF)/(I_R² + Q_R²)

Ical = (I_Rx*I_c - Q_Rx*Q_c)

Qcal = (I_Rx*Q_c + Q_Rx*I_c)

The essential complex operation of the calibration formula (where i is the imaginary part of the complex number)：

R_REF * (I_Rx + Q_Rxⁱ) /(I_R + Q_Rⁱ)

To get the above equation, multiply the numerator and denominator by 𝑰_𝑹− 𝑸_𝑹^𝒊.

The amplitude and Phase Angle of the impedance are calculated by the following formula, where Mag and phase are represented by 32-bit signed integer data, and the calculation result is multiplied by 1000 to make the data accuracy to the third decimal place.

Mag = sqrt( I_Cal*I_Cal + Q_Cal*Q_Cal ) * 1000

Phase = (180/Pi)*atan2(Q_Cal, I_Cal) * 1000