GB1103990A - Parametric amplifier - Google Patents

Abstract

1,103,990. Parametric amplifiers. MULLARD Ltd. 10 Feb., 1967, No. 6413/67. Heading H3B. A parametric amplifier uses a Gunn effect element both as the source of pumping frequency and as the variable capacitance element. A degenerate amplifier (fp -fs = fi, where fp = 2fs} is shown in Fig. 2, the Gunn effect element 1 being located in a length of low height waveguide which at one end is terminated by an adjustable shorting piston 5, and at the other end is coupled to a normal height waveguide 6 by an abrupt matching transistion #p/4 long. This normal waveguide is optional and provides a low output monitoring circuit for the pumping frequency. The input and output signals are common to a coaxial line 7 which is matched to a #p/4 transformer line section 8 and a #p/4 inductive section 9. The pump frequency is isolated from the signal circuit by a short-circuit provided by inductive section 9 and a #p/4 annular slot 10, while the widths of the inner and outer conductors of inductive section 9 are so chosen as to provide an inductance of suitable value which resonates with the capacitance of the element 1 at the signal frequency. D.C. energization of the element 1 is effected between the inner conductor of line 7 and a conducting plate 10 of an R.F. shunt which is insulated by an annular spacer 11. A non-degenerate amplifier (fp = fs + fi, where fi > fs) is also described, Fig. 3, a low-pass #8/4 filter section 12 being connected between transformer 8 and the element 1 which shortcircuits the element at the idler frequency and prevents the pumping frequency from passing into the signal line 7. Short-circuited #1/2 line 9<SP>1</SP> is inductive at the signal frequency and tunes the element 1 at the signal frequency. Line 9<SP>1</SP> may be adjustable in length to provide amplifier tuning.