As the run length of same bit becomes larger, the quarity of eye-diagram becomes worse. So many encoding specification restricts maximum ren length of samebit. If you wish to add maximum ran length restriction, set the "maximum run length" before press "compute" button. If the "maximum run length" value is set to 0, no restriction will be applied to get worst eye-diagram based on infinite length of random bit pattern.
In this eye-diagram, the worst and best traces and same more better traces will be shown to avoid infinit computing time.
For example, if you have 14.3 ns 50 % rise time cable of actual length and you must use this cable for 163 ns/bit NRZ pulse transmission of AES3 application, you must input "163e-9" for bit width and "14.3e-9" for rise time.
If you can not know the 50 % rise time of actual cable, of acutual cable at any high frequency value, you can estimate the 50 % rise time from a attenuation constant at some frequexncy using following formulae.
T = 0.350 * (alpha*l)^2/f where¡¢ T = estimated 50 % rise time of actual cabel (s) aplpha = attenuation of cable (neper/m) l = length of cable (m)In transmission therory the unit of cable attenuation is the neper/m. If you got the attenuation value of dB/m or dB/feet in field, you must convert to neper/m as wollowing relations.
1 dB = 8.686 neper 1 feet = 0.3048 m 1 dB/feet = 0.03509 neper/m
Though it is not well known, it can be proved that the eye-diagram od well-designed cable is determined by 50 % risetime and bit rate. And this program is based on this fact.