This circuit uses low-cost IN4148 diodes and exhibits about 1.5 dB insertion loss from 10 to 1000 MHz w
ith a few volts of negative bias. D3 conducts and D1/D2 are cut off, which results in 30 to 50 dB isolation. When a few volts of positive bias are applied, Dl and D2 are biased on and D3 is cut off. This circuit should be useful in applications where a low-cost RF switch is necessary.