Transient Oscillations in Electric Wave-filters

HE electric wave-filter has been very fully discussed with respect to its remarkable steady-state properties. 1 In the present paper it is proposed to give the results of a fairly extensive theoretical study of its behavior in the transient state. This study is of particular interest and importance in connection with the wave-filter, because, as we shall find, its remarkable selective characteristics are peculiarly properties of the steady state and become sharply defined only as the steady state is approached. To this fact, it may be remarked in passing, is to be ascribed the uniform failure of wave-filters to suppress irregular and transient interference, such as "static," in anything like the degree with which they discriminate against steady-state currents outside the transmission range. This limitation is common to all types of selective networks and restricts the amount of protection it is possible to secure from transient or irregular interference. In fact the general conclusions of the present study are applicable to all types of selective circuits. In the present paper the discussion will be principally concerned with the following phases of the general problem. 1. The indicial admittances of a representative set of wave-filters. The indicial admittance, as explained below, is equal to the current, expressed as a time function, in response to a uniform steady e.m.f. of unit value, applied to the network at time ^ = 0. It has been shown in previous papers that a knowledge of the indicial admittance of an invariable network completely determines its behavior, both in the transient and steady state; to all types of applied forces.