Characterizing Calibration Standards Using One Airline as a Transfer StandardT. Roberts and J. Martens

Anritsu Company, 490 Jarvis Drive, Morgan Hill, CA 95037 US

This paper introduces methods to characterize coaxial calibration

standards using one airline as transfer standard. The methods

discussed lend themselves to computer optimization techniques to

arrive at optimal polynomial coefficients and S-parameter model

representations of calibration standards. The calibration standards

characterized and data presented were from a random sample of K

(2.92 mm), V (1.85 mm) and W (1.00 mm) Vector Network Analyzer

calibration kits manufactured over the past decade. The focus of

this paper is Open, Short and Load (OSL) characterization but can be

expanded to other 1-port calibration standards or kits such as

multiple offset shorts (or opens) as examples. Electrical

performance comparison of characterized fixed terminations to

sliding terminations is also presented.

Abstract Error Vector Reduction Method cont. Error Vector Coupling cont.

Conclusions

Broadband Termination Model cont.

Fig. 3. Error Vector Reduction for Γk and Γk-1 intervals in the

Frequency Domain.

Error Vector Reduction Method

Using one airline, the ripple method is used to extract the

residual errors at a calibrated test port.

Fig. 1. Source Match ripple measurement technique

Fig. 2. Source Match vector addition in the complex plane

The process of optimizing residuals is to reduce the magnitude of

the unwanted error vectors. Reducing the Γcsm error vector is

accomplished by iteratively adjusting the capacitance correction

function C(f) of the Open standard model in Eqn. 2 for each kth

interval.

Γopen(f) = e-j·2·[β(f)·L + atan(ω(f)·C(f)·Zo)][2]

Γshort(f) = -e-j·2·[β(f)·L + atan(ω(f)·Lind(f)/Zo)] [3]

Fig. 5. Corrected Source Match vs. Frequency vs. gender and model

type. V (1.85 mm) connector type.

Broadband Termination Model

A new load model was developed to better approximate the

physical geometry of Anritsu’s 28 series precision broadband coaxial

terminations..

Fig. 7. Cross-sectional view of broadband coaxial termination

• Polynomial and .s1p data models for 1-port calibration standards

can be derived by reducing unwanted residual error vectors.

• Based on very low residual levels obtained, high quality OSL

calibrations with low uncertainty can be achieved using

empirically derived models.

• Corrected Directivity using modeled Terminations, on average,

meets or exceeds that of Sliding Loads.

• The strong impact to Source Match from the applied termination

model indicates the termination model should be derived before

reflect standard models.

Fig. 13. Corrected Directivity vs. Frequency vs. Termination, Female

V (1.85 mm), Fixed Load Point-by-Point model and Sliding Load.

Fig. 14. Corrected Directivity vs. Frequency vs. Termination, Female

V (1.85 mm), Fixed Load Polynomial model and Sliding Load.

Error Vector Coupling

Source Match Coupling is the change in corrected Source Match

with and without the termination model function applied as

expressed in Eqn. 5. Conversely, Directivity Coupling is the change in

corrected Directivity with and without the Open and Short standard

model functions applied as expressed in Eqn. 6.

∆CSM = abs [CSM(Γt ≠ 0) – CSM(Γt = 0)] [5]

∆CD = abs [CD(C(f) ≠ 0, L(f) ≠ 0) – CD(C(f) = 0, L(f) = 0)] [6]

Fig. 22. Source Match Coupling vs. Frequency vs. gender, V (1.85 mm)

Fig. 23. Directivity Coupling vs. Frequency vs. gender, V (1.85 mm)

Fig. 8 Electrical model of broadband coaxial termination