from __future__ import annotations
from itertools import chain
from math import ceil, floor
import gdsfactory as gf
from gdsfactory.component import Component
from gdsfactory.typings import LayerSpec
[docs]
@gf.cell
def interdigital_capacitor(
fingers: int = 4,
finger_length: float | int = 20.0,
finger_gap: float | int = 2.0,
thickness: float | int = 5.0,
layer: LayerSpec = "WG",
) -> Component:
"""Generates an interdigital capacitor with ports on both ends.
See for example Zhu et al., `Accurate circuit model of interdigital
capacitor and its application to design of new uasi-lumped miniaturized
filters with suppression of harmonic resonance`, doi: 10.1109/22.826833.
Note:
``finger_length=0`` effectively provides a plate capacitor.
Args:
fingers: total fingers of the capacitor.
finger_length: length of the probing fingers.
finger_gap: length of gap between the fingers.
thickness: Thickness of fingers and section before the fingers.
layer: spec.
"""
c = Component()
assert fingers >= 1, "Must have at least 1 finger"
width = 2 * thickness + finger_length + finger_gap # total length
height = fingers * thickness + (fingers - 1) * finger_gap # total height
points_1 = [
(0, 0),
(0, height),
(thickness + finger_length, height),
(thickness + finger_length, height - thickness),
(thickness, height - thickness),
*chain.from_iterable(
(
(thickness, height - (2 * i) * (thickness + finger_gap)),
(
thickness + finger_length,
height - (2 * i) * (thickness + finger_gap),
),
(
thickness + finger_length,
height - (2 * i) * (thickness + finger_gap) - thickness,
),
(thickness, height - (2 * i) * (thickness + finger_gap) - thickness),
)
for i in range(ceil(fingers / 2))
),
(thickness, 0),
(0, 0),
]
points_2 = [
(width, 0),
(width, height),
(width - thickness, height),
*chain.from_iterable(
(
(
width - thickness,
height - (1 + 2 * i) * thickness - (1 + 2 * i) * finger_gap,
),
(
width - (thickness + finger_length),
height - (1 + 2 * i) * thickness - (1 + 2 * i) * finger_gap,
),
(
width - (thickness + finger_length),
height - (2 + 2 * i) * thickness - (1 + 2 * i) * finger_gap,
),
(
width - thickness,
height - (2 + 2 * i) * thickness - (1 + 2 * i) * finger_gap,
),
)
for i in range(floor(fingers / 2))
),
(width - thickness, 0),
(width, 0),
]
c.add_polygon(points_1, layer=layer)
c.add_polygon(points_2, layer=layer)
c.add_port(
name="o1",
center=(0, height / 2),
width=thickness,
orientation=180,
layer=layer,
)
c.add_port(
name="o2",
center=(width, height / 2),
width=thickness,
orientation=0,
layer=layer,
)
return c
if __name__ == "__main__":
c = interdigital_capacitor()
c.show(show_ports=True)
