This disclosure includes a four pole bandstop filter coupled to a five pole bandpass filter tuned to an adjacent band to achieve a very steep attenuation curve between the two bands and an increased bandstop width.
A method for making tuned resonance passive electronic filters. The method consists of computing the values of the filter components and then using standard unmatched components that approximate the computed values in conjunction with certain components that are made variable for the purpose of tuning out the unmatched characteristics of the unmatched components. A typical filter may include several poles where each pole includes an unmatched component, such as a capacitor, and a variable component such as an inductor. Adjacent poles may be coupled by unmatched or variable inductors or capacitors. Each pole is tuned for resonance by applying the output of a signal generator to a particular pole, while shorting adjacent poles, and tuning the variable component of that pole for resonance. Resonance may be indicated by a null on an a.c. voltmeter connected to measure pole.
The invention relates to an interference suppression method and circuit for an electrical system, said electrical system comprising a main transformer (2) with a star point (12), phase leg conductors (L1, L2, L3) connected to the transformer (2), a neutral conductor (N) connected to the earth potential (3) and to the star point (12) of the transformer (2), and loads (5) connected between the phase leg conductors (L1, L2, L3) and the neutral conductor (N), said loads being connected to the neutral conductor (N) at connection points (4). In accordance with the invention a bandstop filter (1) tuned at a center frequency 3*f is connected between the star point (12) of the transformer (2) and the connection points (4) of the loads (5).
A communication transmission system includes one or more modulated carrier communication channels in which a receiver has a modified vestigial side band filter for eliminating phase cancellation. Accurate design of the modified vestigial side band filters at the receivers, further reduces susceptibility to frequency drift caused by component aging and component response to environmental changes. The system has particular utility in multiple channel carrier telephone communication systems which utilize limited available band width for providing a maximum number of communication channels over an extended length communication line.
A first filter the group delay of which in the pass band contains a ripple is connected to a second filter so as to cancel the ripple. The second filter has a pass band at least within the pass band of the first filter. The gain of the second filter is reduced gradually from the frequency of the minimum attenuation into the lower and higher frequency regions and the group delay thereof is reduced gradually from the frequency of the minimum attenuation into the lower and higher frequency regions.
By exchanging the position of the input and output resonator means relative to other resonator elements in a mechanical filter, the lengths of the bridging wires used to control the steepness of the bandpass characteristic of the filter can be reduced. Reducing the length of the bridging wires reduces both flexural spurious mode problems and extensional coupling variation problems.
