AD8302 signal amplitude phase detection

AD8302 module

Introduction to AD8302

AD8302 is a monolithic integrated circuit introduced by ADI for measuring the amplitude and phase of RF/IF signals. It can simultaneously measure the amplitude ratio and phase difference between two input signals from low frequency to 2.7GHz. The device integrates two closely matched logarithmic detectors on a single chip, thereby minimizing error sources and associated temperature drift. The device's dynamic range can be extended to 60dB for amplitude measurements and 180 degrees for phase measurements.

Similar product

Chip Features

Comes with 1.8V reference output

Measures magnitude and phase from low frequency to 2.7GHz

Phase measurement 0-180°

Accurate typical to less than 1 degree

Accurate Phase Measurement Scale Factor of 10mV/Degree

Module pin

Working principle of AD8302

Internal block diagram

Working principle

The amplitude and phase measurement principle of AD8302 is mainly based on the logarithmic compression function of the logarithmic amplifier. His mathematical expression is:

VOUT=Vslplog（ Vin / Vz ）

The AD8302 measures the difference in the outputs of two identical log amps driven by signals with similar waveforms but different levels. Since the subtraction in the logarithmic domain corresponds to the division in the linear domain, the output becomes:

VMAG=Vslplog(VINA / VINB)

The output of the last stage of the logarithmic amplifier in the internal block diagram above is a finite signal that is completely within the dynamic range of the input signal. The two finite signals from the matched logarithmic amplifier drive an exclusive-or digital phase detector. With the method of zero point, the extracted phase difference has nothing to do with the original input signal level. The general expression for the phase output is:

VPHS=VΦ[Φ(VINA)-Φ(VINB)]

The above Vin is the input voltage;

Vz is the intercept;

Vslp is the slope;

VMAG is the amplitude discrimination output voltage;

VPHS is the amplitude discrimination output voltage;

VINA is the input signal A;

VINB is the input signal B;

VΦ is the phase frequency;

Φ is the relative phase of the signal;

Ideally, the amplitude ratio and phase difference between AD8302 input signal A and input signal B correspond to the curves of VMAG and VPHS.

experiment

wiring

phase identification

Signal input parameters: sine wave frequency 3M, amplitude 500mV change phase difference

The phase difference between INA and INB input signals is changed to 0°, and the voltage of VPHS measured by the multimeter is 1.804V

(In an ideal state, when the phase difference between INA and INB is 0°, the VPHS output voltage is 1.8V, and the ideal state cannot be achieved due to limited conditions)

The phase difference between INA and INB input signals is changed to 90°, and the voltage of VPHS measured by the multimeter is 0.91V

(In an ideal state, when the phase difference between INA and INB is 90°, the VPHS output voltage is 0.9V, and the ideal state cannot be achieved due to limited conditions)

The phase difference between INA and INB input signals is changed to 180°, and the voltage of VPHS measured by the multimeter is 0.0258V

(In an ideal state, when the phase difference between INA and INB is 0°, the output voltage of VPHS is 0V, and the ideal state cannot be achieved due to limited conditions)

Amplitude

The accuracy of the equipment in this experiment is limited, so only the experiment when the amplitude ratio is 0

In the experiment, INA and INB of AD8302 input two sine waves with an amplitude of 560mV respectively, and the VMAG measured by the multimeter is 0.93V.

(In an ideal state, the amplitude ratio of INA and INB is 0, and the output voltage of VMAG is 0.9V, and the ideal state cannot be achieved due to limited conditions)

The experiment is over.

Experiment summary

Personal experiments cannot rule out hardware errors and limited conditions. The experimental data is slightly different from the ideal curve in the manual. Chip differences will also make the actual measured data different from the ideal curve.