Patent GB-1240188-A (GB)
Title: Electrical netdorks including semiconductor elements
IPC: H03B7/14
Filed: 1968-10-23
Abstract: 1,240,188. Semi-conductor negative resistance elemente. MICROWAVE ASSOCIATES Inc. 23 Oct., 1968 [12 Feb., 1968], No. 50425/68. Heading H1K. [Also in Division H3] A network for operation in a given band comprises at least one semi-conductor element 4 biased to exhibit negative resistance in the given band and biasing means and mounting means having inductance Ld of magnitude such that the range of natural resonance frequencies of the element 4 and biasing and mounting means is different from the given band and the semi-conductor element 4 is less effective as a negative resistance device in the range of the natural resonant frequencies than in the given operating frequency band. The elements may be Read avalanche diode, Gunn effect diode which may be operated in the LSA mode, tunnel discharge PNPN type semi-conductor diodes or transistors providing negative resistance at high frequencies. The natural resonant frequencies of the diodes 4 in Fig. 2 and the inductance Ld of their mountings and biasing are selected to occur about a frequency (fs. Fig. 3, not shown), above the desired operating frequency fo, determined by L T  and C T  of the resonator, such that the diode is near or in the positive resistance region at the natural resonance frequency where oscillations cannot occur. The resonator of Fig. 2 may be constructed as a cavity, Fig. 11, with elements 32, and turned by a screw 40. Alternatively the output from the individual diode circuits could be capacitively coupled to the resonator (Fig. 4, not shown), where the frequency of the undesired modes is below that of the desired mode. Each diode circuit may have two diodes (Fig. 5) capacitively coupled to a resonator 11. Each of the diodes in the above arrangements may be replaced by two or more in series or shunt. The above circuits may be used as oscillators which may be injection locked to an injected signal. Alternatively the circuits may be operated as amplifiers, by injecting the signal to be amplified through a ferrite circulator into the output line 7<SP>1</SP>. The mutual coupling M 3  may be made large to prevent self-oscillation. The circuits of Figs. 2 and 5 may be coupled with a waveguide or transmission line (Figs. 7 and 8, not shown), instead of the resonators. Mounting of elements.-The diode elements 32 (Fig. 9) may be bonded or soldered to metal layers 30 separated by dielectric layers 31 which form the by-pass capacitors such as C 5 , Fig. 2. The block 35 of Fig. 9 may then be arranged within a rectangular cavity (Figs. 10 and 16, not shown), or cavity of Fig. 11, or a cylindrical cavity 48 (Fig. 15). Alternatively the block 35 may be used as the wall of a waveguide or transmission line (Fig. 13, not shown), or may be formed as part of a coaxial transmission line (Fig. 17, not shown). The alternate layers 30.1 of the block 35 may extend beyond the intermediate layers 30.2 to radiate excess heat. The capacitive coupling such as C c  of Fig. 5 may be in the form of capacitive coupling probes 46, Fig. 15 (and Figs. 14 and 16, not shown), which couple the elements to the output, e.g. the cylindrical cavity 48. When using the circuits of (Figs. 7, 8, 13 and 16, not shown), referred to above as transmission line amplifiers to avoid oscillation caused by reflected waves ferrite materials may be inserted into the line which give greater power absorption for one direction of propagation than for the other. Alternatively, ferrite isolators can be inserted between sections of transmission line.