RF Trap for Instrumentation
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18
Field service technicians have been unable to adjust and/or trouble shoot computers in the presence of strong RF fields. This environment can be caused by nearby FM and TV broadcast facilities. These signals are picked up by the oscilloscope probe and often mask the desired signal. The RF trap described is a notch filter that offers approximately 30 dB rejection to the unwanted signal, while causing only minimal distortion to the desired waveform. This permits the use of oscilloscopes to time and trouble shoot products near high power RF sources. J1 and J2 are coax connectors that match the connectors on the probe and oscilloscope, and have their shell connected to the metal case 11. C1 and L1 comprise a series resonant circuit, which exhibits a low impedance at the resonant frequency and a high impedance at all others.