Other Parts Discussed in Thread: AFE4300
Good evening,
i'm working for the first time on the module in object and i'm encountering difficulties with the calibration procedure for the I/Q mode given in http://www.ti.com/lit/an/sbaa202/sbaa202.pdf. In details, i have performed the following steps:
1) I've short the jumpers J11, J12, J22, J23, J24, J25.
2) From the AFE4300 Device GUI, i have set the board as follow:
3) I've connected the IOUT0 and IOUT1 to the on-board impedance simulator as follows
4) I've set the switch SW3 in order to get 750 Ohm. This is my calibration resistor Rx.
5) From the ADC Capture & Analysis, i've acquired the following I/Q values: I = 0.508 V and Q = -0.110 V
6) I've set the switch SW3 in order to get 1 kOhm. This is my calibration resistor Ry.
7) From the ADC Capture & Analysis, i've acquired the following I/Q values: I = 0.676 V and Q = -0.143 V
8) By adopting the formulas for the magnitude and phase, i've computed the interpolating line passing through the magnitudes of the reference resistors. In particular, i've got a slope of 1460 and an offset of -9.1. The phase of Rx is -12°.
9) As sample network, i've set the on board impedance simulator in order to get a series RC circuit with R = 604 Ohm and C = 400 pF.
7) From the ADC Capture & Analysis, i've acquired the following I/Q values: I = 0.412 V and Q = -0.051 V
8) By inserting these values in the interpolated line equation i get a magnitude of 597 Ohm. The phase computed from the values given in 7) is -7°, and so the corrected phase should be -7°-(-12°) = 5° that is not correct.
In order to check if there was a bug in my procedure, i've used the functionalities of calibration and measurement in the BCM Measurement tab and it gives results quite similar to what i've found independently
Does someone see a bug in my procedure? Thanks