Patent ID: 7482812

Claim:
A receiver for a downhole tool, the receiver comprising: a loop antenna including at least a single turn of antenna wire deployed about a tool housing, the loop antenna disposed to receive an electromagnetic wave in a borehole; a tuning network electrically connected in series with the loop antenna such that the loop antenna and the tuning network in combination form a series-resonant circuit that series resonates at a plurality of preselected interrogation frequencies; a transformer having primary and secondary windings, the primary winding electrically connected in series with the loop antenna and the tuning network; and a preamplifier circuit electrically connected to the secondary winding of the transformer, the preamplifier circuit and the transformer disposed to present a load impedance to the tuning network and the loop antenna, the load impedance selected to be sufficiently high to reduce secondary radiation from the loop antenna to below a predetermined value at at least one of the interrogation frequencies.