A Four-Decade Bandwidth Hybrid Coupler

A hybrid coupler is a reciprocal radio-frequency building block with four ports. Signal power applied to any port is equally divided between the two adjacent ports, while the remaining port receives none. Hybrid couplers find many uses in RF circuitry. Our specific application is the elaboration of sum and difference of the signals produced by an electrostatic position pick-up in a particle accelerator. Hybrids qualified as 'Wide-Band' commonly span two octaves of frequency, and the best ultra-wideband devices cover about three decades. The hybrid coupler described here has a useful response from 40kHz tosome 400MHz.