  Time-domain reflectometry (TDR) is an established means of measuring
impedance inhomogeneity of a variety of waveguides, providing critical data
necessary to characterize and optimize the performance of high-bandwidth
computational and communication systems. However, TDR systems with both the
high spatial resolution (sub-cm) and voltage resolution (sub-$\muV$) required
to evaluate high-performance waveguides are physically large and often
cost-prohibitive, severely limiting their utility as testing platforms and
greatly limiting their use in characterizing and trouble-shooting fielded
hardware.
  Consequently, there exists a growing technical need for an electronically
simple, portable, and low-cost TDR technology. The receiver of a TDR system
plays a key role in recording reflection waveforms; thus, such a receiver must
have high analog bandwidth, high sampling rate, and high-voltage resolution.
However, these requirements are difficult to meet using low-cost
analog-to-digital converters (ADCs). This article describes a new TDR
architecture, namely, jitter-based APC (JAPC), which obviates the need for
external components based on an alternative concept, analog-to-probability
conversion (APC) that was recently proposed. These results demonstrate that a
fully reconfigurable and highly integrated TDR (iTDR) can be implemented on a
field-programmable gate array (FPGA) chip without using any external circuit
components. Empirical evaluation of the system was conducted using an HDMI
cable as the device under test (DUT), and the resulting impedance inhomogeneity
pattern (IIP) of the DUT was extracted with spatial and voltage resolutions of
5 cm and 80 $\muV$, respectively. These results demonstrate the feasibility of
using the prototypical JAPC-based iTDR for real-world waveguide
characterization applications
