Patent GB-911334-A (GB)
Title: Improvements in or relating to parametric amplifier arrangements
IPC: H03F7/04
Filed: 1960-09-16
Abstract: 911,334. Parametric amplifiers. TELEFUNKEN G.m.b.H. Sept. 19, 1960 [Sept. 19, 1959], No. 31935/60. Class 40 (9). A parametric amplifier comprises filters and hybrid junctions to separate the pump, signal and idler frequencies. The variable reactance may be inductive or capacitative. In the embodiment described the reactance is a negatively-biased semiconductor diode. Amplifier stages may be connected in series or in parallel. Transformers and terminating impedances are indicated throughout by the reference letters T and Z. Single-stage amplifeer (Figs. 1, 2).- A signal at frequency # 1  is fed to a diode D over line L 1  and low-pass filter TP. The pumping frequency fp is fed to the diode D from source PX through parallel paths including filters F 1 , F 2 , hybrid junctions B 2 , B 1  and a high-pass filter HP which passes the pumping frequency fp and the idler frequency f 2 , but not the signal frequency f 1 . The idler frequeney f 2  is reflected by filters F 1  which are staggered by #<SP>2</SP>/4 so that they combine in the fourth line L 2  of the hybrid B 1 . If the output is required at frequency # 2 , line L 2  is terminated without reflection by a ferrite isolator J, a filter F 2  (accepting f 2 ) and a terminating impedance Z. If the output is required at frequency f 1 , the isolator is replaced by the characteristic impedance Z of the line L 2  and the output at frequency f 1  is taken from line L 1 <SP>1</SP> associated with a timing device T 1 <SP>1</SP>. In a practical form, Fig. 2, the line L 1  is a coaxial line and the tuning device T 1  is a further line L 12  tuned by a sliding piston S 1 . Two annular condensers constitute the tuning device Tp. The line L 2 p is a waveguide with a narrow face b and a broad face at right-angles thereto. This guide is closed and tuned by a piston S 2 . The diode D is connected between the wall of the guide and the low-pass filter TP. Each of the hybrid junctions B 1 , B 2  is in the form of a magic T. The fourth arm of each magic T is perpendicular to the drawing plane but is turned down into the plane for the purpose of illustration. Diaphragms B and tuning members A constitute the filters F 1 . Parallel stages (Fig. 3).-Two diodes in assemblies P<SP>1</SP>, P<SP>11</SP> corresponding to assembly P of Fig. 1 are fed with signal frequency f 1  from terminal 1 and hybrid junction B 11 . Each diode is also fed with pumping frequency fp from a common source PX via hybrid junction arrange. ments B<SP>1</SP> 1 , B<SP>1</SP> 2  and B<SP>11</SP> 1 , B<SP>11</SP> 2 . An output at signal frequency may be taken from line L<SP>1</SP> 1 . The two lines L 2 <SP>1</SP>, L 2 <SP>11</SP> feed a common hybrid junction B 22  to give an output at the idler frequency f 2  on terminals 2, 2<SP>1</SP>. Quarter-wave loops are included when necessary to keep the waves in phase. Series stages.-Two arrangements like the arrangement shown in Fig. 3 may be connected as shown in outline in Fig. 4. Thus the amplified output at signal frequency f 1  on terminal 1a<SP>1</SP> is the input for the second amplifier giving an output on terminal 1b<SP>1</SP>. The Specification describes other arrangements using two or more amplifier stages, each stage being based on Fig. 1.