Constant impedance transmission line routing network

Details

Inventors: Flora, Laurence P.;
Assignee: Burroughs Corporation (Detroit, MI)
Primary Examiner: Smith; Alfred E.
Assistant Examiner: Wise; Robert E.
Attorney, Agent or Firm: Kozak; Alfred W., Cass; Nathan, Peterson; Kevin R.

A network apparatus whereby a high frequency transmission line may be switched and distributed to any one of a selected number of outputs without disturbing the characteristic impedance or continuity of the transmission line. Transmission strip lines on a printed circuit board connect each of the two outputs of a single pole double-throw reed relay to the single input of a subsequent double-throw relay. The relay switches and the transmission strip lines are parallel to an embedded ground plane within the printed circuit board. Each realy switch is surrounded by an electromagnetic shield which is connected at both its input end and its output end to the ground plane in the most direct fashion. Actuating means are provided proximate to each relay switch for activation purposes. Thus, a switching tree network may be provided whereby the single input line suitable for carrying high frequency signals, including digital signals having high rate rise times and high rate fall times, may be distributed to the relay switching tree to a selected single output of a plurality of outputs without changing the characteristic impedance of the transmission line.

DETAILED DESCRIPTION What is claimed is: 1.
In a system for providing a constant impedance transmission line which is switchable from one input to a plurality of output points, the network comprising: (a) an input signal line having a high side and a low side; (b) first switching means including a movable contact and first and second stationary output contacts, said movable contact connected to said input line and actuatable to connect either one of said first or second stationary output contacts; (c) a first and second output line connected to said first and second stationary output contacts; (d) means to actuate said movable contact of said input line; (e) sealing means encompassing said switching means; (f) a circuit board of insulating layers sandwiching a ground plane connected to said low side at said signal input line; (g) shielding means encompassing said switching means and including connection means to said ground plane; (h) first and second transmission lines connecting the output contacts and output lines of said switching means to an input line of a second and of a third switching means, said first and second transmission lines being of equal cross section and length and running parallel to said ground plane.
2.
The network of claim 1, including: (a) recess means in said circuit board for mounting each of said switching means parallel and adjacent to said ground plane.
3.
The network of claim 1, wherein said shielding means includes: a cylindrical electromagnetic shield having an input end and an output end; a first connection means from said input end to said ground plane; a second connection means from said ouput end to said ground plane.
4.
The network of claim 3, including a subsequent group of switching means having input lines connected from the output lines of prior switching means and wherein the transmission lines, connecting each prior group of switching means to a subsequent group of switching means, are of equal cross section and equal length and form a symmetrical configuration parallel to said ground plane

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