Designing a circuit apparatus with multiple propagation speeds of signals

Abstract

Designing a circuit apparatus involves determining locations and lengths of routing paths for signals, routing paths of a first length range being located in a first layer, and routing paths of a second length range being located in a second layer; determining propagation speeds for the signals to propagate through the routing paths within a propagation time range; and selecting dielectric materials for the layers in accordance with the determined propagation speeds for the routing paths.

1 . A method for designing a circuit apparatus having a plurality of layers and a plurality of conductors disposed within the layers for conducting a plurality of signals, comprising: 
 determining locations and lengths of routing paths for the signals, routing paths of a first length range being located in a first one of the layers, and routing paths of a second length range being located in a second one of the layers;    determining propagation speeds for the signals to propagate through the routing paths within a propagation time range; and    selecting dielectric materials for the layers in accordance with the determined propagation speeds for the routing paths.    
   
   
       2 . A method as defined in  claim 1  wherein the circuit apparatus comprises a printed circuit board.  
   
   
       3 . A method for designing a circuit apparatus having at least first and second layers and at least first and second conductors disposed within the first and second layers, respectively, for conducting at least first and second signals, respectively, comprising: 
 determining a minimum length for each of the conductors, the first conductor being longer than the second conductor;    determining a propagation time for the first and second signals to propagate through the first and second conductors and whether the propagation time for each signal is within a time constraint; and    upon determining that the propagation times for the signals are not within the time constraint, selecting first and second dielectric materials having different characteristic propagation speeds for the first and second layers, respectively, the characteristic propagation speed of the first dielectric material being faster than the characteristic propagation speed of the second dielectric material.    
   
   
       4 . A method as defined in  claim 3 , further comprising: 
 selecting the first and second dielectric materials to minimize a difference between a ratio of the length of$-the first conductor to the length of the second conductor and a ratio of the characteristic propagation speed of the first dielectric material to the characteristic propagation speed of the second dielectric material.    
   
   
       5 . A method for designing a circuit apparatus having a plurality of layers and a plurality of conductors disposed within the layers for conducting a plurality of signals according to time constraints, comprising: 
 selecting dielectric materials having different characteristic propagation speeds for the layers;    determining a ratio between the characteristic propagation speeds of the dielectric materials of two of the layers; and    determining a range of allowable lengths of the conductors disposed in the two layers depending on the ratio between the characteristic propagation speeds of the dielectric materials of the two layers and on the time constraints.