Calibration for vector network analyzer

Data processing: measuring – calibrating – or testing – Calibration or correction system – Error due to component compatibility

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

Reexamination Certificate

active

06701265

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to vector network analyzers, and more particularly to an improved calibration method for a vector network analyzer.
To obtain accurate results the users of vector network analyzers calibrate the instruments by measuring three known impedance standards, typically a short, an open and a characteristic impedance (Z
0
) load for one-port measurements. For two-port measurements three additional measurements are performed using non-connection and through connections between the ports. Using the measured results of these measurements, the vector network analyzer's systematic errors are mathematically corrected, resulting in excellent measurement accuracy. Measurements consist of many stepped measurements at sequential frequencies that appear to be “swept” when a user is measuring a Device Under Test (DUT). Each measurement point has “calibration” data taken during the calibration routine that are stored and used for correcting that particular measurement point.
The problem is that, while the vector network analyzer gives excellent results, the calibration is done at each exact frequency step used in the measurement. For example if a vector network analyzer has a potential frequency measurement range of 25 MHz to 2500 MHz with 100 kHz frequency steps, then to gather calibration data for each frequency step requires 3×24,751=74,253 calibration measurements without taking multiple measurements for noise reduction. This large number of measurements requires an inordinate amount of time for calibration procedures. So instead the calibration is done over a specified measurement range, such as 500.5 MHz to 1011.5 MHz, which only requires 3×5, 111=15,333 calibration measurements. However anytime that any frequency parameter, such as start frequency, stop frequency, number of frequency points, frequency resolution, etc., is changed by a user, the vector network analyzer must be re-calibrated. Many users do not need measurements of extreme accuracy, and they find re-calibrating the vector network analyzer each time a frequency variable is changed, even slightly, to be very cumbersome and time consuming. Therefore the user has the choice of either operating without calibration at all or of taking the time and effort of having excellent calibration.
Also prior vector network analyzers require low-phase-noise and low-amplitude-noise measurements, particularly for the calibration measurements. If there is any significant noise, as might be the case with low-cost hardware in the vector network analyzer, then many measurements are taken and a large amount of averaging is used to reduce the effect of the noise, adding another multiplier to the number of calibration measurements that need to be taken.
What is needed is a vector network analyzer that provides accuracy as well as ease of operation, even when low-cost hardware is used.
BRIEF SUMMARY OF THE INVENTION
Accordingly the present invention provides an improved calibration method for a vector network analyzer that acquires sparse calibration data across the frequency range of the vector network analyzer, or at least a larger range than a specified measurement frequency range. The sparse calibration data may be obtained by measuring every N
th
frequency step of the vector network analyzer, or by measuring each frequency step of the vector network analyzer and compressing the results. Then for each measurement frequency of the vector network analyzer a correction value is appropriately interpolated from the sparse calibration data to provide calibration error data. The calibration error data is then used to correct the measurement data to provide an accurate result.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.


REFERENCES:
patent: 4215308 (1980-07-01), Kusters
patent: 4746879 (1988-05-01), Ma et al.
patent: 5012181 (1991-04-01), Eccleston
patent: 5578932 (1996-11-01), Adamian
patent: 5587934 (1996-12-01), Oldfield et al.

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Calibration for vector network analyzer does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Calibration for vector network analyzer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Calibration for vector network analyzer will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-3271326

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.