Instrumentation & Measurement Magazine 25-7 - 44

A computer running
automated software in
LabVIEWTM
controls the
measurement setup over
the IEEE-488 bus. The
software performs the necessary
calculations and
displays functions as explained
previously.
Results
Fig. 7. TM verification program flow.
Characterization was carried
out on DUT using the
equipment mentioned
above. Parametric data
acquired using the ATS
software system generates
the relevant results. The
primary attributes of ATS,
namely parameter uncertainty
and specification,
govern the overall measurement
time. Estimation
of computation of measurement
time is provided
as follows for essential
parameters.
Fig. 8. Hardware experimental setup.
in-house developed SINE as explained previously. The SMC +
Phase Reference calibration was already done at the beginning
of the measurement. The connecting cables were calibrated
using a signal generator, and a power meter and appropriate
offsets were added during data processing to remove the response
characteristics of the setup.
For accurate measurement of group delay characteristics
of DUT, SMC phase reference measurement provides a coherent
phase relationship from one frequency to the next in
each sweep. However, the phase measurement of the first data
point is random from sweep to sweep. All of the phase data
in the sweep is normalized against a single point that has the
best signal-to-noise ratio and results in less jitter. This is applicable
during both measurement and the calibration sweeps.
Accurate noise figure calculation is done by solving noise parameter
equations by measuring noise power coming out of
DUT at each impedance and frequency sweep. All other parametric
measurements are based on swept techniques of VNA.
44
Frequency Response:
Measurement time for
frequency response is governed
by the gain slope
(amplitude response over
1 MHz or 1 kHz bandwidth,
specified by dB/MHz or
dB/kHz). To compensate
for uplink path loss and
correct estimation of gain
slope of DUT having sinusoidal pattern in particular bandwidth,
frequency response correction (flatness correction) data
is uploaded in the stimulus generator over the required frequency
band. Hence, 1001 points are chosen.
Noise Floor: Noise floor is used to estimate mismatch error,
the effect of radiation/conductive coupling and conformity
of path from uplink to downlink. The measurement provides
small-signal frequency response/ gain slope characteristics of
the DUT. The resolution bandwidth of the spectrum analyzer
governs the sweep time. Hence, RBW of 300 kHz is selected to
ensure at least three points/1 MHz bandwidth.
Noise Figure: The noise figure is measured by performing noise
source ON or OFF and measuring noise bandwidth (dBm/Hz)
using the spectrum analyzer's marker-to-noise function mode.
This mode requires enabling the average detector and corresponding
amplitude correction due to deviation from the
IEEE Instrumentation & Measurement Magazine
October 2022
Instrumentation & Measurement Magazine 25-7

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