GB901905A - Parametric amplifier - Google Patents

Abstract

901,905. Parametric amplifiers. HUGHES AIRCRAFT CO. Nov. 30, 1960 [Dec. 18, 1959], No. 41221/60. Class 40 (9). A parametric amplifier comprises a coaxial line 22 for carrying the signal energy, which carries a stub tuner 21 for tuning it to resonance at the signal frequency and contains a band-pass filter 41 permitting only signal frequencies to pass; the centre conductor being connected through an aperture of a wall of a rectangular waveguide via a non-linear reactance device 28 to the opposite wall 46; and the rectangular wave-guide, which is fed from the left-hand end with pump frequency, containing a high-pass filter 47. The portion 14 of the wave-guide is tuned to the idler frequency by the plunger 18. With the pump frequency being higher than the signal, frequency, the wave-guide 11 may be constructed to be beyond cut-off with respect to the signal frequency. Hence any adjustments to the wave-guide either in the idler section or on the pump supply side do not affect the signal tuning. The filter 41 prevents the adjustment of the stub tuner 21 from affecting the tuning of the idler and pump circuits. The high-pass filter, which may be a section of reduced width formed by the insertion of a conductive block 47 in the wave-guide 11, prevents any tuning of the pump source from affecting the tuning of the idler circuit. Termination of the coaxial cable at the wave-guide is effected by the non-linear reactance which is a semi-conductor diode acting as a variable capacitance in conjunction with an inductive iris 36. The pump frequency may be conveyed from a standard wave-guide 11 to the operative part of the wave-guide which is of reduced height via a matching portion having a linearly changing height. This concentrates the pump field at the diode and also achieves a measure of broadening of the signal band-width. In an alternative construction the semiconductor diode is mounted in a sleeve of insulating material passing through a hole in the lower wall of the wave-guide. This enables back-bias to be applied to the diode. The broadening of the signal band-width may be further enhanced by providing a broader idler band-width. This may be effected by broadening the end of the idler cavity nearest the plunger 18, making both the broader and narrower portions of this cavity of 90 degrees length at the idler frequency.