ES368051A1 - Symmetrical polyphase networks utilizing constant reactances - Google Patents

Abstract

A symmetrical polyphase network includes, in each phase, a frequency invarient reactance such that the network responds differently to input signals of negative and positive frequency. Such networks may be employed in N-path commutated circuits or as single sideband modulators. In one embodiment, Fig. 8 (not shown), comprising a two-phase network, the frequency invarient reactances are formed by two port gyrators (G3 . . . G6) having one port connected to each phase. In an alternative form, Fig. 14, the reactances are constituted by fourport networks which transform resistances into reactances (l: j transformers) 1 . . . 4. The circuit may also include negative impedance converters, Fig. 15 (not shown), to change the sign of the reactances. If the capacitors of Fig. 14 are omitted, the circuit of Fig. 14 non- stitutes an N-port gyrator. One form of i:j transformer suitable for a two-phase system, Fig. 9B, is a voltage shift type in which each phase includes a series transistor VT1, VT2, with the collectors of each transistor being connected to the base of the other, one connection being via a third transistor VT3. If impedances Z are connected across each output, impedances jZ will be seen looking into each input. The input and output connections may be reversed, Fig. 10B (not shown). The circuit may also be modified for current shift operation by connecting the input or output terminals to the bases of the series transistors, Figs. 11B, 12B (not shown). For three-phase networks, Fig. 22, 1: h transformers 11A . . . 11D are used, in which h represents a 2#/3 phase shift. Suitable transformer circuits comprise a series transistor in each phase, each having its base electrode connected to the collector of the transistor in an adjacent phase either directly, Figs. 16, 17 (not shown) or via emitter followers, Figs. 18, 20 (not shown). For four-phase operation l:j transformers may be employed which are similar in form to the l: h transformer of the three-phase system, Figs. 25, 26 (not shown). By suitably connecting the four outputs the circuits may be arranged to operate in a voltage or a current shift mode, and may transform by j. A two-phase circuit which attenuates frequencies of one polarity and passes those of the other may be used as a quadrature modulator, Fig. 32. If an input carrier signal V is applied to one input port V 1 , and the other input port V 2 is earthed, then quadrature carriers are obtained at the two output ports V 3 , V 4 . These are then modulated with quadrature modulation signals in 7, 8 and the two modulated signals added to produce a single sideband output.