Backplane databus utilizing directional couplers

• US 5,365,205 A
• Filed: 05/20/1993
• Issued: 11/15/1994
• Est. Priority Date: 05/20/1993
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Wong, Larry K.
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): GAMBINO, DARUIS
• Application Number:
  US08/064,282
• Time in Patent Office: 544 Days
• Field of Search: 333/109, 333/116, 375/7
• US Class Current: 333/109
• CPC Class Codes: G06F 13/4077 Precharging or discharging

Abstract

A backplane databus and bussing method provide multidrop signal distribution using capacitive and inductive coupling of a main signal. A main signal loop on the backplane has a plurality of coupling loops coupled thereto for a respective length L_C. The main signal, typically a NRZ trapezoidal shaped waveform is coupled into the coupling loops as a bipolar signal. The main signal loop is terminated by a resistor having a resistance equal to the characteristic impedance of the track forming the main signal loop. Similarly, the coupling loops are terminated at a far end by resistors whose impedance is equal to the characteristic of the track forming the coupling loop. The near end of the loop is connected to a receiver having a matching input impedance.

Claims

1. A backplane databus comprising:

a plurality of modules, each having first, second and third edges, first and second substantially parallel conductive tracks between the first and second edges for carrying a main signal, a third conductive track forming a loop running from the third edge, paralleling the first substantially parallel conductive track for a coupling length L_c and returning to the third edge, and first, second and third connectors affixed to the first, second, and third edges respectively, the first and second connectors electrically connected to respective ends of the first and second substantially parallel conductive tracks, the third connector electrically connected to the third conductive track;

a pair of end modules, each having fourth and fifth edges, a fourth conductive track forming a u-shape from the fourth edge back to the fourth edge, a fifth conductive track forming a loop running from the fifth edge, paralleling the fourth conductive track for a coupling length L_c and returning to the fifth edge and fourth and fifth connectors affixed to the fourth and fifth edges respectively, the fourth connector electrically connected to the fourth conductive track, the fifth connector electrically connected to the fifth conductive track; and

an intermediate module having sixth, seventh and eighth edges, sixth, seventh, and eighth conductive tracks, the sixth and seventh conductive tracks each forming an L-shape from the eighth edge to the sixth and seventh edges, respectively, an eight conductive track between the sixth and seventh edges and sixth, seventh and eighth connectors affixed to the sixth, seventh and eighth edges, respectively, and electrically connected to the sixth and eighth conductive tracks, and seventh and eighth conductive tracks and sixth and seventh conductive tracks, respectively, the intermediate, plurality and end modules being interconnected thereby to form a continuous main conductive track including the sixth conductive track, a portion of the plurality of first conductive tracks, a fourth conductive track, a like portion of the plurality of second conductive tracks, the eighth conductive track, the remainder of the plurality of second conductive tracks, a fourth conductive track, the remainder of the plurality of first conductive tracks, and the seventh conductive track.

2. A backplane databus as claimed in claim 1 wherein the plurality of modules are formed on the printed circuit board.

3. A backplane databus as claimed in claim 2 wherein the printed circuit board includes pads for connection to the pins of the connectors.

4. A backplane databus as claimed in claim 3 wherein the first conductive track lies between the pads for each connector for the plurality of circuit cards.

5. A backplane databus as claimed in claim 4 wherein the third conductive track parallels the first conductive track between the pads for each connector for the plurality of circuit cards and loops away from the first conductive track and back to respective pads at each end of the third conductive track.