Patent GB-524549-A (GB)
Title: Improvements in wide-band coupling systems for electric circuits
IPC: H03H7/01
Filed: 1939-04-18
Abstract: 524,549. Impedance networks; valve amplifying circuits. HAZELTINE CORPORATION. April 18, 1939, No. 11718. Convention date, April 22, 1938. [Classes 40 (iii) and 40 (v)] Undesired series inductance associated with resistance, or shunt capacitance associated with conductance, in a television or telephone circuit comprising a source and a load, is complemented by means of a dead-end filter so that maximum admittance or impedance, with constant modulus, may be secured throughout the working range of frequencies. The mathematical theory given for pure series inductance and shunt capacitance in Specification 524,547 is thus extended to take account of the presence of dissipative elements ; and it is found (Fig. 4, not shown) that an approximately constant impedance, with, however, an advantageous peak at the cut-off frequency, can be obtained. Both source and receiver may be connected to terminals 8, Fig. 5a, and may have a shunt capacitance Cn and conductance Gn; these are to be complemented by the filter 10, 11, which is composed of reactances and is dead-ended in a resistance Ro. Either the receiver or the source may be transferred to the terminals 9, Figs. 5b, 5c (not shown) so that they will be separated by a four-terminal portion of the network. Further embodiments using low-pass filters and analogous to those given in Specification 524,547, are described with reference to Figs. 6a to 8c (not shown); and a similar embodiment using a band-pass filter to complement series capacitance and inductance is illustrated in Fig. 9 (not shown). In the amplifier shown in Fig. 10, the valves 20, 21 are coupled by a low-pass filter which is dead-ended at 23<SP>1</SP> and has shunt capacitances 24, 25 which are mainly the inherent capacity of the valves. Valves 21, 22 are coupled by a similar filter calculated to take account also of the grid leak conductance 29. The terminating shunt capacitances of the couplings 23, 26 may be so adjusted that the impedance of one coupling increases while the other decreases to a compensating extent near the cut-off frequency. Fig. 11 (not shown) illustrates a a circuit which takes account of resistance inherent in a transformer primary. Fig. 12 shows a coupling between a push-pull power amplifier 40, 41 and an aerial whose impedance is represented at 42. The midband frequency of the coupling coincides with the frequency to which the aerial is tuned. The shunt capacitance 47 and series inductance and conductance 43, 44, of the aerial, and the capacitance 48 of the valves 40, 41 are complemented by means of a band-pass filter in which the inductances are replaced by equivalent transformers, 49, 51, 52, 53 and a dead-end is provided at 54, 55, 49. Specifications 475,490 and 524,548 also are referred to. The Specification as open to inspection under Sect. 91 describes various combinations of constant k and m-derived sections and halfsections are described with reference to Figs. 10a to 10e (Cancelled) (not shown) for complementing shunt capacitance, and to Fig. 11 (Cancelled) (not shown) for complementing shunt capacitance and inductance in combination. This subject-matter does not appear in the Specification as accepted.