Agilent Utilizing TDR and VNA

Frequency dependent effects are becoming more prominent with the increasing
data rates of digital systems. Differential circuit topology is proliferating
throughout design laboratories with the goal of enhancing the data carrying
capable of the physical layer. Simple impedance and delay measurements of
copper transmission lines on backplanes are not sufficient to ensure accurate
analysis of gigabit interconnects. The challenge to push design rules to the
limit now requires the use of concurrent time and frequency domain measure-
ments. This paper will discuss methods to achieve proper measurement
techniques using a time domain reflectometer (TDR) oscilloscope and vector
network analyzer (VNA) to assure accurate models are produced for simulation.
Error correction techniques will be discussed for both time domain and
frequency domain instrumentation. It will be demonstrated that accurate
4-port frequency dependent models can closely simulate performance of
a differential channel.