Synchronous frequency domain measurements for the extraction of X-parameters in digital to analog transmitters

Abstract

This paper presents an extraction procedure for behavioral model approximation of digital transmitters. A first explanation on how to extract X-parameters for a digital to analog device will be done, followed by a procedure for phase synchronization measurements. Finally, a real measurement example will be performed.Index Terms -Analog signal, digital signal, mixed-signal instrumentation, software defined radio.

Synchronous Oversampled Measurements for the Extraction of Mixed-Signal Behavioral Models in Digital to Analog Integrated Transmitters

“…The proposed method extends the one presented in [2], and continues to use X-parameters as the modeling approach. However, contrary to what was done before, in this work the clock (CLK) port of the DAIT is also included in the model.…”

“…In order to assure this, the frequency resolution of both signals is forced to be the same, resulting in (2), (2) where and stand for the acquired number of points from the RTO and from the DUT, respectively.…”

“…In the way it was done in [2], the reference signal used here will be the CLK, and the normalization instant will also be 90 of the CLK signal, at point A (see Fig. 3).…”

“…3). The entire synchronization process is similar to [2], the main difference is that now the CLK signal will have a frequency times lower than the sampling frequency of the analog sampling receiver. Thus, the CLK signal can be read directly, as is shown in Fig.…”

“…Such a requirement changes the way synchronization can be employed successfully since the assumption made in [2] of an equal sampling rate in both the analog receiver and DAIT is no longer valid. Thus, a synchronization and correction strategy that suits the extraction of such models is proposed and an assessment of the extracted model is performed.…”