| 摘要 |
A non-linear junction detector (NLJD) apparatus comprises signal processing circuitry 21 housed in a radio frequency (RF) screened enclosure 61 coupled via RF screened cable 14 to a separately disposed search head 15. The search head contains an antenna 1 and filter 3 for a transmitted signal and an antenna 10, 11 and filter 9, 12 for a return signal. The signal processing circuitry generates a first, relatively, low power signal that an amplifier 5 converts to a second, relatively high power signal that is filtered and then transmitted to irradiate a target object. The return signal is received, filtered to extract a harmonic signal and amplified 8, 13 to be passed to the signal processing circuitry to determine the presence of a target object. Incorporating the filtering and possibly amplification components in the search head improves the systems detection sensitivity to NLJ devices, for example by reducing the occurrence of false signals from cables and connectors. |
