skrf.calibration.calibration.SDDLWeikle

class skrf.calibration.calibration.SDDLWeikle(measured, ideals, *args, **kwargs)

Short-Delay-Delay-Load (Oneport Calibration), Liu-Weikle formulation.

One-port self-calibration, which contains a known short, a known mismatched load, and two partially-unknown delay shorts. The short can be an offset short with known phase, or a zero-length (flush) short. The load can have an arbitrary impedance, as long as it’s reflective (not perfectly matched) and known exactly. This is especially useful when an ideal load is impractical to fabricate. The delay shorts have unity reflection magnitudes, but unknown phases (unknown electrical lengths).

See __init__() for the correct parameters order.

This class uses the Liu-Weikle formulation, which requires a mismatched load (i.e. non-zero reflection coefficient). Calibration fails if the load is perfectly matched. In the paper, a fully-known radiating open is used as the load standard.

It was originally designed for waveguide calibration with resistance to flange misalignment by Liu-Weikle [1], which was itself a modification of the earlier Sigg-Simon SDDM calibration [2]. In Sigg-Simon’s SDDM, the load must be matched, while Liu-Weikle SDDL only allows a mismatched load.

Note

This algorithm is bandwidth-limited due to phase wrapping, conceptually similar to TRL’s bandwidth limit. Some over-determined multi-line variants allow wideband calibration, but this is not implemented in scikit-rf. If a wideband calibration is required (common for coaxial systems), it’s necessary to manually split measurements to multiple subbands and calibrate each band separately.

Band edges may suffer from increased errors. It’s recommended to test line lengths experimentally via simulations first. Choosing an optimal selection of line lengths that covers the widest bandwidth is a non-trivial optimization problem, with several proposed solutions [3].

References

[1]

Z. Liu and R. M. Weikle, “A reflectometer calibration method resistant to waveguide flange misalignment,” Microwave Theory and Techniques, IEEE Transactions on, vol. 54, no. 6, pp. 2447-2452, Jun. 2006.

[2]

W. Sigg and J. Simon, “Reflectometer calibration using load, short and offset shorts with unknown phase,” Electronics Letters, vol. 27, no. 18, pp. 1650–1651, 1991.

[3]

A. Lewandowski, W. Wiatr, L. J. Opalski and R. Biedrzycki, “Accuracy and Bandwidth Optimization of the Over-Determined Offset-Short Reflectometer Calibration,” in IEEE Transactions on Microwave Theory and Techniques, vol. 63, no. 3, pp. 1076-1089, March 2015, doi: 10.1109/TMTT.2015.2396496.

Attributes

biased_error	Estimate of biased error for overdetermined calibration with multiple connections of each standard.
caled_ntwk_sets	Return a NetworkSet for each caled_ntwk, grouped by their names.
caled_ntwks	List of the corrected calibration standards.
coefs	Dictionary or error coefficients in form of numpy arrays.
coefs_12term	Dictionary of error coefficients for 12-term Model.
coefs_12term_ntwks	Dictionary or error coefficients in form of Network objects.
coefs_3term	Dictionary of error coefficients for One-port Error model.
coefs_3term_ntwks	Dictionary of error coefficients in form of Network objects.
coefs_8term	Dictionary of error coefficients for 8-term (Error-box) Model.
coefs_8term_ntwks	Dictionary of error coefficients in form of Network objects.
coefs_ntwks	Dictionary of error coefficients in form of Network objects.
error_ntwk	The calculated error Network or Network[s].
family
frequency	Frequency object of the calibration.
normalized_directivity	Directivity normalized to the reflection tracking.
nstandards	Number of ideal/measurement pairs in calibration.
output_from_run	Return any output from the run().
residual_ntwk_sets	Returns a NetworkSet for each residual_ntwk, grouped by their names.
residual_ntwks	Dictionary of residual Networks.
total_error	Estimate of total error for overdetermined calibration with multiple connections of each standard.This is the combined effects of both biased and un-biased errors.
unbiased_error	Estimate of unbiased error for overdetermined calibration with multiple connections of each standard.
verify_12term
verify_12term_ntwk

Methods

__init__	Short-Delay-Delay-Load initializer.
apply_cal	Apply correction to a Network.
apply_cal_to_all_in_dir	Apply correction to all touchstone files in a given directory.
apply_cal_to_list	Apply correction to list or dict of Networks.
apply_cal_to_network_set	Apply correction to a NetworkSet.
embed	Embed an ideal response in the estimated error network[s]
from_coefs	Create a calibration from its error coefficients.
from_coefs_ntwks	Create a calibration from its error coefficients.
plot_caled_ntwks	Plot corrected calibration standards.
plot_calibration_errors	Plot biased, unbiased and total error in dB scaled.
plot_residuals	Plot residual networks.
pop	Remove and return tuple of (ideal, measured) at index.
remove_and_cal	Remove a cal standard and correct it, returning correct and ideal.
run	Run the calibration algorithm.
update_coefs	Update current dict of error coefficients.
write	Write the Calibration to disk using write().