Coplanar waveguide coupler

class qultra.CPW_coupler(nodes, gap, cpw, l)[source]

Bases: object

Represents a 4-node CPW (coplanar waveguide) coupler.

This class initializes a CPW coupler component with its node connections, gaps, individual CPWs, and physical length. It also computes the capacitance and inductance matrices upon initialization.

Node ordering (top wiev)

1----------2

3----------4

The diagrams below illustrate the widths and gaps of the CPW coupler, both in the case without a central ground plane (1) and in the case with a ground plane between the CPW lines (2).

GND                                           GND
    |       |        |      |        |        |
    |       |        |      |        |        |
    |       |________|      |________|        |
      gap0    cpw0     gap1    cpw1    gap2

GND                                                             GND
    |       |        |      |      |        |       |       |
    |       |        |      |      |        |       |       |
    |       |________|      |______|        |_______|       |
      gap0    cpw0     gap1    cpw1   gap2    cpw2    gap3

Parameters:

nodes (list of int) – List of 4 nodes to which the coupler is connected. Must have length 4.
gap (list of float) – List of gaps between CPWs [um].
cpw (list) – List of CPW segments’ width [um]
l (float) – Physical length of the coupler [m].

C

Capacitance matrix computed from the CPW configuration.

Type:: ndarray

L

Inductance matrix computed from the CPW configuration.

Type:: ndarray

Raises:: ValueError – If nodes does not contain exactly 4 elements, or if gap does not have length equal to len(cpw) + 1.

Y(z)[source]

Construct the complex admittance matrix of a cpw coupler

Parameters:: z (complex) – Complex variable (complex frequency)
Returns:: Y_matrix – complex admittance matrix
Return type:: numpy array

current(V, z, x)[source]

Calculate the current in a CPW coupler given the voltage node values.

Parameters:

V (complex array) – Voltage at nodes.
z (complex) – Complex variable (complex frequency).
x (float) – Position along the CPW coupler.

Returns:

I – Calculated current at position x.

Return type:

complex

inductive_energy(V, z)[source]

Calculate the inductive energy stored in a CPW.

Parameters:

V (complex array) – Voltage at nodes.
z (complex) – Complex variable (complex frequency).

Returns:

E – Inductive energy stored in the CPW.

Return type:

complex