GB893082A - Improvements in or relating to travelling wave amplifiers - Google Patents

Abstract

893,082. Parametric amplifiers. WESTERN ELECTRIC CO. Inc. March 20, 1959 [March 26, 1958], No. 9701/59. Addition to 850,036. [Class 40 (9)]. The constants of the travelling wave parametric amplifier described in the parent Specification are arranged so that amplification takes place when the frequency S of the signal applied by generator 5, Fig. 1, to line 1 is greater than the frequency P of the pumping wave applied by generator 9 to line 3. In effect, the modulation product (S - P) produced by the non-linear coupling inductors 8 is amplified, the pumping, signalling and idling frequencies being related by the equation P=(S-P)+(2P-S) the line 2 being arranged to support the idling frequency (2P - S). The amplified signal (S - P) may then be demodulated by the pumping frequency P to produce an amplified version of S. As in the parent Specification the variable coupling reactors may be capacitors. By using a number of idling frequencies the signal frequency may be made much greater than the pumping frequency. The signalling frequency S, the pumping frequency P and idling frequencies Q, I1, I2, &c. must satisfy the relations and the phase constants must satisfy the relations A reactance tube or a reverse biased P - N junction semi-conductor diode may be used as a variable capacitance. In a modification, the pumping wave may be transmitted by generator 79 along a circular waveguide 73, Fig. 3. Pairs of conductors 71a, 71b and 72a, 72b provide paths for the signal and idler waves, the signal being generated at 75. The waves are coupled by a body 70 of ferrite material wedged in the guide. The idler conductors 72a, 72b are supported by the ferrite material and the signal conductors are supported by foam plastic material 74. A filter 76a stops either the idler wave S - P or the signal S. Magnetic poles N, S on opposite sides of the waveguide bias the ferrite. Filters may be used to stop unwanted modulation products. The pumping wave may be fed back from the output to the input to avoid waste. Specification 839,596 also is referred to.