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Gated Power Measurement Description
Last updated: June 20, 2006
What is a Gated Power Measurement?
Gated power measurements provide a graphical representation of the time response of the mobile station average transmitter power during periods when the power is gated on. During power gated transmission, power from the mobile station is delivered in bursts. A measurement mask delineates the boundaries that the signal's amplitude trace must conform to.
A measurement progress report, showing the number of measurements in a multi-measurement, is displayed on the test set's screen in an "n/m" format. The number of measurements completed,
n
, increases from zero to the total number of measurements which need to be made,
m
. The default settings for gated power measurements include multi-measurement on with a 100 measurement count.
Two views of the power versus time graph are available after the test set analyzes measurement data. The two views are:
-
Rise/Fall View
-
Full/Zoom View
Rise/Fall View
The rise (part of Rise/Fall View) trace zooms in on the rising edge of the burst, from -15 uS to +10 uS relative to the beginning of the burst. The beginning of the burst corresponds with the gated-on power control group clock edge.
Traffic channel frames are subdivided into sixteen 1.25 millisecond segments, called power control groups. When the traffic data rate is set to half, quarter, or eighth, the mobile station transmits only during randomly selected power control groups. These are referred to as "gated-on" power control groups.
The fall (part of Rise/Fall) trace zooms in on the falling edge of the burst, from 1237 to 1262 uS after the beginning of the burst.
Full/Zoom View
The full (part of Full/Zoomed) trace encompasses the entire burst with decreased resolution as compared with the rise and fall. This trace spans the time period from -15 uS to 1262 uS relative the beginning of the burst.
The zoom (part of Full/Zoomed) trace details the area selected by the Zoom Position field and highlighted by a vertical bar displayed on the full trace. This vertical bar can be positioned in any one of 14 locations along the entire length of the zoom burst. (The extreme left and right zoom positions equate to the rise and fall views.)
A marker displaying the power level (from +10 to -45 dB) at each time increment is provided for all traces except for the full view. If a gated power measurement fails, the marker will be automatically positioned at the first fail point.
How is a Gated Power Measurement Made?
Each gated power measurement is triggered internally by the test set. During the gated power measurement, a DSP (Digital Signal Processor) samples the signal and returns 5,625 amplitude versus time data points. Data points return power levels, relative to the average power during the middle of the burst, that correspond with time intervals before, during, and after the burst.
The gated power measurement analyzes the rising and falling edges of the burst to determine where the -3 dB points are. Using the -3 dB points to determine the center of the burst, the test set positions the measurement mask (green lines on the display) to align in time with the center of the burst.
Since the middle portion of the burst is compressed in time, the scaling is different when compared to the rising or falling portions. The following formulas can be used to calculate the time associated with each data point from 0 to 5,264 as returned by the
FETCh:GPOWer:TRACe?
command:
Time Association For Data Points 0 through 370
where t1 is the sampling period for each data point, and p is the data point of interest (from 0 to 5,264).
Time Association For Data Points 371 through 4893
where t1 is the sampling period for each data point, and p is the data point of interest (from 0 to 5,264).
Time Association For Data Points 4894 through 5264
where t1 is the sampling period for each data point, and p is the data point of interest (from 0 to 5,264).
Data point 222 corresponds with time 0 on the gated power graph.
On the test set's display, data points are graphed as follows:
Gated Power Measurement Considerations
The following settings are required for the gated power measurement:
-
Operating Mode must be Active Cell
-
System Type must be IS-95 or IS-2000 with Radio Config set to (Fwd1, Rvs1) or (Fwd2, Rvs2)
-
FCH Service Option Setup must be set to SO2 or SO9 (loopback service option)
-
Traffic Data Rate must be set to Eighth.
Gated Power measurements can not be made concurrently with any other measurement, and no other measurement can be made while a gated power measurement is in progress.
The pass/fail result indicates whether or not the trace conformed to the mask.
To make the test run faster, reduce the number of averages (multi-measurement count). The default is 100.
Most failures occur during the rising or falling portions of the burst.
Gated power measurements are expressed in dB, relative to the average of the power levels across the number of 1.25 mS burst specified in the multi-measurement count.
Input Signal Requirements
The gated power measurement meets or exceeds specifications when the following input signal requirements are met:
-
The frequency of the signal being measured must be within the range of 411 MHz to 484 MHz, 804 MHz to 934 MHz, 1.75 GHz to 1.78 GHz, or 1.85 GHz to 1.98 GHz, and be within 100 kHz of the expected frequency.
-
The average power level of the signal at the RF IN/OUT connector must be between -20 dBm to +30 dBm. The test set can autorange to a signal that is within +/- 9 dB of the expected input level (see
RFANalyzer:AUTO:POWer[:SELected]?
).
Key TIA/EIA-98-E Tests Using the Gated Power Measurement
Calibrating the Gated Power Measurement
The gated power measurement is automatically calibrated during a channel power calibration. Follow the channel power calibration schedule and the gated power measurement will be properly calibrated. Refer to
Calibrating the Test Set
for a description of channel power calibration.
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