Narrow band notch filter with extended passband

• US 5,157,362 A
• Filed: 03/27/1990
• Issued: 10/20/1992
• Est. Priority Date: 06/14/1988
• Status: Expired due to Term

• Current Assignee: Andrew F. Tresness
• Original Assignee: Andrew F. Tresness
• Inventors: Zelenz, Martin L.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/500,111
• Time in Patent Office: 938 Days
• Field of Search: 333/167, 333/168, 333/169, 333/170, 333/171, 333/174, 333/175, 333/12, 333/176, 455/1, 455/286, 455/339
• US Class Current: 333/175
• CPC Class Codes: H03H 7/06 including resistors H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence
• CPC Class Codes: H03H 7/1708 Comprising bridging elements, i.e. elements in a series path without own reference to ground and spanning branching nodes of another series path H03H7/07 takes precedence
• CPC Class Codes: H03H 7/1725 Element to ground being common to different shunt paths, i.e. Y-structure
• CPC Class Codes: H03H 7/1758 Series LC in shunt or branch path H03H7/1791 takes precedence
• CPC Class Codes: H03H 7/1766 Parallel LC in series path H03H7/1783 takes precedence
• CPC Class Codes: H03H 7/1783 Combined LC in series path
• CPC Class Codes: H03H 7/1791 Combined LC in shunt or branch path

Abstract

A notch filter having increased pass band characteristics is provided by insertion of an inductor between a normally-grounded capacitor and ground, the capacitor being connected to an inductive-capacitive filter network. By this construction, the equivalent capacitor of the high-frequency equivalent circuit is not connected directly to ground, but rather has the inductor interposed between it and ground. This significantly increases the pass band of the circuit.

Claims

1. In a wide band notch filter of the type used to remove cable television frequencies in a pass band above 55 MHz and comprising an input, an output, a network in series with said input and output, said network comprising inductive and capacitive elements operatively coupled to each other, and resonant circuit means formed by a capacitor and inductor in parallel with each other and coupled between said network and ground, the improvement comprising inductive means between said resonant circuit means and ground, the value of said inductive means being such that the high frequency equivalent circuit of said filter resembles an all pass filter and extends said pass band of said filter to at least 600 MHz.

2. A wide band notch filter according to claim 1 wherein the value of said inductive means is such that the high frequency equivalent of said filter resembles a type III all pass filter.