Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Parameter related to the reproduction or fidelity of a...
Reexamination Certificate
1999-09-01
2001-09-18
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Parameter related to the reproduction or fidelity of a...
C324S615000, C324S076190
Reexamination Certificate
active
06292000
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for determining a harmonic phase response of a device, and more particularly, to a method for determining a more accurate harmonic phase response of a device over a dynamic range not limited by the stimulus source harmonic level.
2. Background
Harmonic measurements are of significant importance in many microwave, millimeter wave, and radio frequency (RF) applications including wireless communications. Excessive harmonic generation by components such as amplifiers or other nonlinear components in a communications device can lead to violations of spectrum rules set by the Federal Communications Commission (FCC), failed performance specifications, interference with other channels, or other problems. Harmonic measurements have been made by using a conventional spectrum analyzer, but this approach can be quite slow and the results are of only limited accuracy. Therefore, conventional methods of harmonic measurements using spectrum analyzers may be undesirable in a high throughput manufacturing environment in which both speed and accuracy of harmonic measurements are required.
To satisfy the requirements of speed and accuracy in harmonic measurements in a high throughput manufacturing environment, measurement techniques have been developed by using conventional vector network analyzers. However, a problem associated with conventional non-ratioed techniques for measuring the harmonic responses of a device by using typical vector network analyzers is that the internal signal sources of typical vector network analyzers are usually not very “clean.” The internal signal source of a typical vector network analyzer may generate a source harmonic in the range of −30 dB to −40 dB relative to the source fundamental frequency signal component. Although a source harmonic in the range of −30 dB to −40 dB relative to the source fundamental frequency component may not be regarded as a high harmonic level per se, the presence of such source harmonic can seriously affect the ability to accurately measure the harmonic response of a device. The presence of stimulus source harmonics can seriously limit the dynamic range of the measurements and the accuracy of the measurement results.
Therefore, there is a need for a method for measuring the harmonic response of a device with enhanced accuracy by using a typical vector network analyzer which may contain a source that has harmonics in addition to the source fundamental frequency component during the measurement of the device. Furthermore, there is a need for a method for measuring the harmonic response of a device to a fundamental frequency input with enhanced dynamic range that is not limited in measurement accuracy or dynamic range by the stimulus source harmonics.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method is provided for calibration to eliminate phase errors when correcting measurements of a DUT to account for source harmonics. For phase corrections, a calibration is performed using a reference standard to establish a relationship between the harmonic phase response of the standard and the source fundamental. Calibration is then applied during measurement of a DUT to get the DUT harmonic phase response relative to the source fundamental.
An output from the DUT is composed of two elements, the DUT's harmonic response to a source fundamental, and the DUT's linear response to the harmonic input from the source. The vector sum of the DUT output responses, GHx, includes all composite harmonics from the DUT normally measured directly. Harmonics from the source which are linearly passed by the DUT, GNx, are also readily measured with a VNA. An output harmonic generated by the DUT, Hx, can then be calculated using vector subtraction according to the equation Hx=GHx−GNx. The output harmonic Hx will be free from source harmonic components.
To obtain a magnitude for the output harmonic |Hx′| relative to the source fundamental, the magnitude of Hx is multiplied by a relative source harmonic level. To obtain a magnitude of an output harmonic |Hx″| relative to an output fundamental, the magnitude of Hx is multiplied by a relative source harmonic level and then divided by the magnitude of a linear fundamental gain of the DUT.
To determine the phase for Hx′ and Hx″, a phase reference plane is established using the phase standard, which can be an element such as a shunt diode. When the shunt diode is used as a fundamental phase reference, the second harmonic can be referenced 180° out of phase with respect to the fundamental. The third harmonic can also be referenced 180° out of phase with respect to the fundamental. The offset established by this phase reference is applied to measurements after the calibration to determine phase for Hx′ and Hx″.
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patent: 5631553 (1997-05-01), Bose et al.
patent: 5642039 (1997-06-01), Bradley et al.
patent: 5937006 (1999-08-01), Clark et al.
Kapetanic Peter
Martens Jon
Rangel David
Anritsu Company
Brown Glenn W.
Fliesler Dubb Meyer & Lovejoy LLP
Nguyen Vincent Q.
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