| 摘要 |
Sensitivity of a bridge circuit for measuring propagation characteristics of test samples is increased by employing a pulse-echo technique. The bridge includes sample and reference arms having substantially identical characteristics. Each of the bridge arms is arranged so that a single pulse signal is caused to propagate the length of each arm a plurality of times. The pulse signals are periodically sampled and compared to generate a difference signal. In turn, the difference signal is utilized to determine a characteristic of a test sample, for example, attenuation.
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