# This code is part of KQCircuits
# Copyright (C) 2021 IQM Finland Oy
#
# This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
# License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later
# version.
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# (meetiqm.com/iqm-open-source-trademark-policy). IQM welcomes contributions to the code.
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from math import pi, sin, cos, ceil
from kqcircuits.elements.element import Element
from kqcircuits.pya_resolver import pya
from kqcircuits.util.geometry_helper import vector_length_and_direction, round_dpath_width
from kqcircuits.util.parameters import Param, pdt, add_parameters_from
from kqcircuits.elements.waveguide_coplanar_straight import WaveguideCoplanarStraight
[docs]
def arc(r, start, stop, n, mode=1):
"""Returns list of points of an arc
Args:
r: radius
start: begin angle in radians
stop: end angle in radians
n: number of corners in full circle
mode: discretization method, 0=shortcut, 1=match length, other=detour
.. MARKERS_FOR_PNG 0,91 0,100
"""
match mode:
case 0: # shortcut method, where points are on the arc
end_ratio = 1.0
r_scale = lambda _: 1.0
case 1: # matching length method, where combined length of segments equals the analytical length of the arc
end_ratio = 0.7339449 # based on trigonometric calculations and a few degree Taylor series approximation
r_scale = lambda x: 1 + x**2 / 24 + x**4 * 7 / 5760 # approximation for x/2 / sin(x/2) that accepts x=0
case _: # detour method, where segments are tangents on the arc
end_ratio = 0.5
r_scale = lambda x: 1.0 / cos(x / 2)
c_steps = 2 * end_ratio - 1 # nominal constant steps at start and end
n_steps = max(round(abs(stop - start) * n / (2 * pi) - c_steps), ceil(1 - c_steps))
step = (stop - start) / (n_steps + c_steps)
r_corner = r * r_scale(step)
pts = [pya.DPoint(r * cos(start), r * sin(start))]
for i in range(n_steps):
alpha = start + step * (i + end_ratio)
pts.append(pya.DPoint(r_corner * cos(alpha), r_corner * sin(alpha)))
pts.append(pya.DPoint(r * cos(stop), r * sin(stop)))
return pts
[docs]
@add_parameters_from(WaveguideCoplanarStraight, "add_metal", "ground_grid_in_trace")
class WaveguideCoplanarCurved(Element):
"""The PCell declaration of a curved segment of a coplanar waveguide.
Coordinate origin is left at the center of the arc.
"""
alpha = Param(pdt.TypeDouble, "Curve angle (rad)", pi)
length = Param(pdt.TypeDouble, "Actual length", 0, unit="μm", readonly=True)
[docs]
def coerce_parameters_impl(self):
# Update length
self.length = self.r * abs(self.alpha)
[docs]
@staticmethod
def build_geometry(element, trans, alpha):
(
left_inner_arc,
left_outer_arc,
right_inner_arc,
right_outer_arc,
left_protection_arc,
right_protection_arc,
annotation_arc,
) = WaveguideCoplanarCurved.create_curve_arcs(element, alpha)
# Left gap
pts = left_inner_arc + left_outer_arc
shape_1 = pya.DPolygon(pts)
element.cell.shapes(element.get_layer("base_metal_gap_wo_grid")).insert(trans * shape_1)
# Right gap
pts = right_inner_arc + right_outer_arc
shape_2 = pya.DPolygon(pts)
element.cell.shapes(element.get_layer("base_metal_gap_wo_grid")).insert(trans * shape_2)
pts = annotation_arc
shape = round_dpath_width(pya.DPath(pts, element.a), element.layout.dbu)
element.cell.shapes(element.get_layer("waveguide_path")).insert(trans * shape)
if element.add_metal:
shape = pya.DPolygon(left_inner_arc + list(reversed(right_inner_arc)))
element.cell.shapes(element.get_layer("base_metal_addition")).insert(trans * shape)
# Protection layer
if element.ground_grid_in_trace:
element.add_protection(trans * shape_1.sized(1))
element.add_protection(trans * shape_2.sized(1))
else:
# Protection layer
pts = left_protection_arc + right_protection_arc
element.add_protection(trans * pya.DPolygon(pts))
[docs]
def build(self):
WaveguideCoplanarCurved.build_geometry(self, pya.DTrans(), self.alpha)
[docs]
@staticmethod
def create_curve_arcs(elem, angle):
"""Creates arcs of points for a curved waveguide.
Args:
elem: Element from which the waveguide parameters for the arc are taken
angle (double): angle of the curved waveguide
Returns:
A tuple consisting of lists of points, each list representing one of the arcs. (left_gap_inner,
left_gap_outer, right_gap_inner, right_gap_outer, left_protection, right_protection, annotation)
"""
alphastart = 0
alphastop = angle
left_gap_inner = arc(elem.r - elem.a / 2, alphastart, alphastop, elem.n)
left_gap_outer = arc(elem.r - elem.a / 2 - elem.b, alphastop, alphastart, elem.n)
right_gap_inner = arc(elem.r + elem.a / 2, alphastart, alphastop, elem.n)
right_gap_outer = arc(elem.r + elem.a / 2 + elem.b, alphastop, alphastart, elem.n)
left_protection = arc(elem.r - elem.a / 2 - elem.b - elem.margin, alphastart, alphastop, elem.n)
right_protection = arc(elem.r + elem.a / 2 + elem.b + elem.margin, alphastop, alphastart, elem.n)
annotation = arc(elem.r, alphastart, alphastop, elem.n)
return (
left_gap_inner,
left_gap_outer,
right_gap_inner,
right_gap_outer,
left_protection,
right_protection,
annotation,
)
[docs]
@staticmethod
def produce_curve_termination(elem, angle, term_len, trans, face_index=0):
"""Produces termination for a curved waveguide.
The termination consists of a rectangular polygon in the metal gap layer, and grid avoidance around it.
The termination is placed at the position where a curved waveguide with alpha=angle and trans=trans would end.
Args:
elem: Element from which the waveguide parameters for the termination are taken
angle (double): angle of the curved waveguide
term_len (double): termination length, assumed positive
trans (DTrans): transformation applied to the termination
face_index (int): face index of the face in elem where the termination is created
"""
(
left_inner_arc,
left_outer_arc,
right_inner_arc,
right_outer_arc,
left_protection_arc,
right_protection_arc,
_,
) = WaveguideCoplanarCurved.create_curve_arcs(elem, angle)
# direction of the termination box
_, term_dir = vector_length_and_direction(left_outer_arc[0] - left_outer_arc[1])
if term_len > 0:
# metal gap for termination
pts = [
left_inner_arc[-1],
left_outer_arc[0],
left_outer_arc[0] + term_len * term_dir,
right_outer_arc[0] + term_len * term_dir,
right_outer_arc[0],
right_inner_arc[-1],
]
shape = pya.DPolygon(pts)
elem.cell.shapes(elem.layout.layer(elem.face(face_index)["base_metal_gap_wo_grid"])).insert(trans * shape)
# grid avoidance for termination
protection_pts = [
left_protection_arc[-1],
left_protection_arc[-1] + (term_len + elem.margin) * term_dir,
right_protection_arc[0] + (term_len + elem.margin) * term_dir,
right_protection_arc[0],
]
elem.add_protection(trans * pya.DPolygon(protection_pts), face_index)