Abstract:
The accuracy or error of a phase difference measurement
between two
different si nusoidal signals is significantly affected by the noise in them.
Quadrature Demodulation (QD) is one of the methods used for calculating
the phase difference under considerable noise levels especially in discrete
time measurement systems. Even though the a ccuracy of the usual QD
method may be sufficient enough for some environments, in conditions that
involve noise levels that is reasonably larger, higher accuracy is much
desirable. In this paper, an improved QD method to decrease the phase error
and thus i ncrease the accuracy of a phase difference measurement is
proposed and established. The increased accuracy of the measurements are
confirmed by experimental methods using input signals of signal to noise
ratios (SNRs) ranging from 6.00 dB to 30.0 dB. When compared with the
usual QD method, the experimental results for the phase error
measurements have proven that under similar time consumptions, the
proposed method is more accurate by a factor of greater than 2 to 4. Even at
the worst SNR level at 6.00 dB t he proposed method is more accurate by a
factor of greater than 2 and the phase error is no more than 0.1 o for 100
single averaged measurements of the phase differences. At higher SNR
levels the accuracy of proposed method further increased up to a factor of
4.4. The proposed method could be used in discrete time phase
measurement systems with a higher accuracy.
