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Method for an apparatus to measure PWB differential loss using differential pulse TDR

IP.com Disclosure Number: IPCOM000009100D
Publication Date: 2002-Aug-07
Document File: 3 page(s) / 93K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an apparatus to measure printed wiring board (PWB) differential loss using differential pulse time domain reflectometry (TDR). Benefits include improved functionality and improved ease of implementation.

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Method for an apparatus to measure PWB differential loss using differential pulse TDR

Disclosed is a method for an apparatus to measure printed wiring board (PWB) differential loss using differential pulse time domain reflectometry (TDR). Benefits include improved functionality and improved ease of implementation.

Background

              Conventional methods require a vector network analyzer (VNA) to determine PWB line loss. PWB shops are not conventionally equipped or staffed with the engineers to support a VNA process.

              A differential wave traveling down a differential line is the subtraction of two waveforms (see Figure 1). If both sources are exactly in phase, there would be 0V between them. If one source is delayed, a resultant superposition pulse is injected into the pair with a pulse width equal to the delay. If the lines are electrically longer than the pulse and the lines are left open, a pulse is reflected back to the sources with amplitude that is proportional to the loss of the line.

Description

              The disclosed method is an apparatus to measure PWB differential loss using differential pulse time domain reflectometry. The apparatus is comprised of two independent step sources of equal amplitude that are out of phase by some predetermined amount (see Figure 2). The sources are injected into the two nodes of an unterminated differential line on a PWB (see Figure 3). One source is a 400-ps pulse. The second source is the impulse response of an unterminated 9.9‑inch transmission line...