tono/docs/nodes/SMM Analysis.md

SMM Analysis

Scanning Microwave Microscopy analysis: perform 3-point calibration and de-embedding to convert raw S11 reflection coefficient measurements into quantitative tip-sample capacitance and impedance maps. Equivalent to Gwyddion's smm.c and smm_apply.c modules.

Inputs

Name	Type	Required	Description
s11_amplitude	DATA_FIELD	Yes	Measured S11 reflection coefficient amplitude
s11_phase	DATA_FIELD	Yes	Measured S11 reflection coefficient phase (radians)

Outputs

Name	Type	Description
capacitance	DATA_FIELD	Calibrated tip-sample capacitance map (unit: F)
impedance_real	DATA_FIELD	Real part of the de-embedded tip-sample impedance (unit: Ohm)

Controls

Name	Type	Default	Description
frequency	FLOAT	1e9	Microwave excitation frequency in Hz
ref_impedance	FLOAT	50.0	Reference impedance of the transmission line in Ohm
cal_c1	FLOAT	—	First calibration capacitance standard (F)
cal_c2	FLOAT	—	Second calibration capacitance standard (F)
cal_c3	FLOAT	—	Third calibration capacitance standard (F)
cal_s11_1	FLOAT	—	Measured S11 (complex magnitude) at the first calibration standard
cal_s11_2	FLOAT	—	Measured S11 (complex magnitude) at the second calibration standard
cal_s11_3	FLOAT	—	Measured S11 (complex magnitude) at the third calibration standard

Notes

• SMM measures local microwave impedance and capacitance by recording the S11 reflection coefficient of a scanning probe coupled to a vector network analyser (VNA) operating at GHz frequencies.
• The 3-point calibration procedure uses three known capacitance standards to solve for the VNA error terms and correct systematic measurement errors, mapping raw S11 values to the true tip-sample impedance.
• The error model decomposes VNA systematics into three terms: e00 (directivity), e01 (tracking), and e11 (source match). These are determined from the three calibration measurements and then used to de-embed every pixel.
• Calibration capacitances should span the expected measurement range; widely spaced standards yield a better-conditioned error model and more accurate results.
• The phase input must be in radians. If your data is in degrees, convert before connecting to this node.