A Nonreflective Hybrid Stop-Band Filter (Correspondence)

For operation of parametric amplifiers at low frequencies and at low-impedance levels a parametric diode of very large capacitance is necessary. In general a capacitance which has an impedance of the same order as the source impedance is required, so that for a 600-ohm system at a frequency of 5 kc the static capacitance C/sub 0/ should be C/sub 0//spl tildeoverbar/ 1//spl omega//sub s/R/sub g/ /spl tildeoverbar/0.05 ~f. The capacitance variation with bias should also be large.