HP 8530A, Руководство по эксплуатации и программированию, Страница: 92 / 439

Antenna Calibration
Antenna Calibration
Antenna calibration allows measured data to be expressed in dBi (dB relative to an isotropic
radiator). A standard gain antenna with known or dened gain values at specic frequencies is
used as a transfer standard to calibrate the system.
Calibrating with a standard gain antenna corrects for the transmission response errors .
An optional part of antenna calibration is an \isolation calibration." This calibration reduces
crosstalk errors between input channels . The isolation cal requires a high quality RF load as a
calibration standard. The load you need is determined by the connector type and frequency
range of your system.
Important T erms
Cal \Cal" is an abbreviation for \Calibration."
Cal Denition A cal denition is an ASCII le you create using a text editor . It contains
theoretical or measured frequency and gain values for the standard gain
antenna. Y ou can create the le using any computer-based text editor
which can save text in plain ASCII format. The le can then be loaded into
the receiver from a DOS or LIF disc . A cal denition contains up to seven
\antenna denitions ."
Antenna
Denition
The gain data for a specic standard gain antenna is called an \antenna
denition."
Cal Set A nished calibration data le . During the calibration, the standard gain
antenna is measured and its performance is compared to one or more antenna
denitions . Any dierences are stored in an internal \cal set register ." These
dierences are the error coecients which, when subtracted from the
measurement, result in calibrated results . In antenna calibration, the nal
measurement data is expressed in units of antenna gain (dBi). Cal sets can be
stored in internal registers or to disc .
Angle Domain and Frequency Domain Calibrations
If you perform a calibration while in angle domain, the calibration will be at one frequency .
(Angle Domain makes measurements at only one frequency .)
If you perform a calibration while in Frequency Domain, you can calibrate over a range of
frequencies .
Using a Frequency Domain Calibration in Angle Domain.
HP recommends that you calibrate using Frequency Domain, which calibrates over a range of
frequencies . Y ou can then switch to Angle Domain, and pick any of the frequencies from the
Frequency Domain calibration. This gives you instant access to many calibrated frequencies
(one at a time) when in Angle Domain.
Only one limitation applies; the frequency you want to measure (in angle domain) must exist in
the original calibration. The receiver does not interpolate between calibrated frequencies .
Here are the basic steps involved in antenna calibration:
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