Why shapes formed by box and path has an error of 0.001um to 0.002um

Comments

• tomas2004

  August 2021 edited August 2021

  Hi Weiling,

  Why don't you use only DPoint, DBox and DPath??? No need to convert taper_l and arm_length to number of DBU equivalents...

   box = DBox.new(-0.5*(arm_length-taper_l), -0.5*(arm_length-taper_l), +0.5*(arm_length-taper_l),+0.5*(arm_length-taper_l))   #Ruby
  

  Now, let's say:

  l1 = 1.447
  l2 = 3.5

  dbu = 0.001

  in microns (DPoint, ...):

  value = 0.5*(l2-l1) = 1.0265

  This value is rounded to the nearest DBU point > (value/dbu).round*dbu = 1.027

  in DBU units (Point, ...):

  l1_dbu = l1/dbu = 1447.0

  l2_dbu = l2/dbu = 3500.0

  value_dbu = 0.5*(l2_dbu-l1_dbu) = 1026.5

  This value is converted to an integer I guess as Point, Box, ... expect integer values > value_dbu.to_i = 1026

  Notice the difference between .to_i and .round:

  value_dbu.to_i = 1026

  value_dbu.round = 1027

  When using Path make sure the width is a multiple of 2*dbu, else the path edges will be off-DBU-grid as well...

  Cheers,

  Tomas
• Weiling_Zheng

  August 2021

  @tomas2004 ，
  Hi, Tomas,
  Thank you very much for your detailed response.
  The method you provide does work. I know little about scripting in klayout. I just followed the way of others in siepic pdk.
  (1)
  Although the method you provide works well, is it wirted by ruby(I see you marked Ruby)?
  Will this make the program unstable when the other parts seems to be written in python?

  class sbend_crossing(pya.PCellDeclarationHelper):
  def init(self):

      # Important: initialize the super class
      super(sbend_crossing, self).__init__()
  

  (2)
  I also find another strange thing.
  I tried to add a structure made up by four arc bend.
  Before, everything works well. When I continue to reduce the length of this structure to 0.6 um, I found that its height is not as expected, it is much smaller, about 0.1um, which could not be caused by dbu.
  Can you see where the problem is?

  

  Normally, it should look like this:
  

      self.param("wg_length", self.TypeDouble, "waveguide length", default=10)
      self.param("taper_l", self.TypeDouble, "The length of S sbend curve", default=1.448)
      self.param("wg_width", self.TypeDouble, "The width of port",default=0.4)
      self.param("taper_w", self.TypeDouble, "The width of centre", default=1.714)
      self.param("arm_length", self.TypeDouble, "The arm length", default=3.5)
      .........
      l1 = self.taper_l / dbu
      l2 = self.wg_length / dbu
      l3 = self.arm_length / dbu
  
      w1 = self.wg_width / dbu
      w2 = self.taper_w / dbu
      .........
      radius=((0.5 * l1) ** 2 + (0.5 * sbend_w) ** 2) / (2 * (0.5 *sbend_w))
      angle=180 * asin((2 * (0.5 *l1) * (0.5 * sbend_w)) / (
                      (0.5 * l1) ** 2 + (0.5 * sbend_w) ** 2)) / pi
      from math import pi, cos, sin
  
      pts=[]
      pts1 = []
      pts2 = []
      pts3= []
      pts4 = []
      from SiEPIC.utils import points_per_circle
      circle_fraction = abs(angle) / 360.0
      # npoints = int(points_per_circle(radius / 1000) * circle_fraction)
      # # npoints = int(200 * circle_fraction)
      # # if npoints == 0 or npoints ==1 :
      # if npoints < 50 :
          # npoints = 1
      npoints = int(self.n * circle_fraction)
      da = 2 * pi / npoints * circle_fraction  # increment, in radians
      i_sum=[]
      for i in range(0,  npoints + 1):
          i_sum = i_sum + [i]
  
          pts1.append(pya.Point.from_dpoint(pya.DPoint(
              (radius * sin(i * da)), (radius * (1 - cos(i * da)))+w1/2)))
          pts3.append(pya.Point.from_dpoint(pya.DPoint(2 * radius * sin(pi * angle / 180) +
                                                       (radius * sin(pi +i * da)),
                                                     -(w1 / 2 - 2 * radius * cos(pi * angle / 180) + (
                                                               radius * (1 - cos(pi + i * da)))) )))
  
      isum1 = i_sum[::-1]
      for i in range(len(isum1)):
          pts2.append(pya.Point.from_dpoint(pya.DPoint(2 * radius * sin(pi * angle / 180) +
                                                      (radius * sin(pi + isum1[i] * da)),
                                                      w1/2-2 * radius * cos(pi * angle / 180) + (
                                                         radius * (1 - cos(pi + isum1[i] * da))))))
          pts4.append(pya.Point.from_dpoint(pya.DPoint(
              (radius * sin(isum1[i] * da)), -(radius * (1 - cos(isum1[i]* da))+ w1 / 2) )))
  
  
      pts = pts1 + pts2 + pts3 + pts4
  
      t9 = Trans(Trans.R0, -l3 - w2 / 2, 0)
      self.cell.shapes(LayerSi).insert(Polygon(pts).transformed(t9))
  
• tomas2004

  August 2021

  Hi Weiling,

  You cannot mix Ruby and Python within a script, but it looks quite similar, just drop the ".new":

  box = DBox.new(-0.5*(arm_length-taper_l), -0.5*(arm_length-taper_l), +0.5*(arm_length-taper_l),+0.5*(arm_length-taper_l))
  

  Check this link: https://www.klayout.de/doc-qt5/programming/python.html

  Cheers,

  Tomas
• Weiling_Zheng

  August 2021

  @tomas2004 ,
  Hi, Tomas,
  Thank you very much for your respond.
  I will check it.

  Best regards!
  Weiling