Digitally Controlled NMR RF PIN Diode Attenuator
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
A digitally controlled PIN diode attenuator is disclosed which provides for accurate computer control of nuclear magnetic resonance (NMR) RF power. As shown in the figure, control voltage signal +Vin (provided by a computer) is transmitted to an inverting unity gain amplifier which produces an inverted output voltage signal -Vo, and to a non-inverting unity gain amplifier which produces a non-inverted output voltage signal +Vo. That is, signal +Vo has the same polarity as input control signal +Vin. Inverted signal -Vo is provided across current limiting resistor R1, and non-inverted signal +Vo is provided across current- limiting resistor R2. Inductor L1 follows resistor R1 to block RF current while offering virtually no opposition to direct current I1.