TX Dynamic Power Measurement Description

Last updated: June 20, 2006

How is a TX Dynamic Power Measurement Made?

The TX dynamic power measurement is a series of channel power measurements in Very Fast speed (see Measurement Speed ), one at each step of the power sequence. It provides a fast power calibration method that covers the typical 90dB (from -60dBm to +30dBm) dynamic range of a CDMA mobile station (MS). It's available in the Active Cell and the IS-2000 Test operating modes (see Selecting an Operating Mode ).

Before starting the TX dynamic power measurement, you must set your MS in a test mode to control the MS to transmit a power sequence with successive down steps of fixed size and duration. You also must set the test set's receiver using manual control, with the power set to match the initial transmit power of the MS's power sequence, and with the frequency set to match the MS's transmit frequency (see Receiver Control ).

An example MS output power sequence for TX Dynamic Power Measurement is shown in the figure below.

MS Output Power Profile for TX Dynamic Power Measurement

The TX dynamic power measurement is firstly triggered by an RF rise impulse (a positive change in power from 20 dB below the initial transmit power) from the MS.

To ensure that the measurements always sample the stable portions of the data record, the test set measures the MS's initial transmit power (step 0) at 6 ms, or 16 ms, or 36 ms after receiving the RF rise trigger (corresponding to the Power Step Time set to 20ms, 40ms or 80ms).Then the test set retunes the expected power range of receiver based on the power measured in the prior step and the Power Step Size setting so that the test set can measure those mobile stations, which do not transmit the power sequence as expected, without aborting the measurement. Each subsequent channel power is automatically measured every 20, 40, or 80 ms (depending on the Power Step Time setting). The test set expects the MS to hold its power constant during each power step. After the measurement is completed, the test set returns all measured results.

Operating Considerations

Don't change any test set settings until the measurement is complete since it may cause the measurement to abort due to the missed trigger.
Don't start the power control transient transmission (see Starting the Reverse CLPC Transient ) when the TX dynamic power measurement is running. Otherwise, the measurement will be closed and its operation is aborted. Moreover, the TX dynamic power measurement will not be able to start (become initiated) while the transient transmission is in progress.
The TX dynamic power measurement is not available in a multi-measurement mode.
The TX dynamic power measurement is expected to only be used when Call Connection status is Idle since the MS must be in a test mode, otherwise it may not produce meaningful results.
The TX dynamic power measurement does not run concurrently with any other measurements. When TX dynamic power measurement is initiated, any other measurements running are closed and a message is displayed to indicate the close. Likewise, when any other measurements are initiated, the TX dynamic power measurement running is closed and a message is displayed.

TX Dynamic Power Measurement Parameters

Power Step Size
Sets the power change that the test set expects the MS to transmit between steps. It should match the value of the power step size of the MS's test mode

GPIB Command: SETup:CTDPower:STEP[:LEVel]
Number of Power Steps
Sets the number of power steps that the test set expects the MS to transmit. It should match the value of the number of power steps of the MS's test mode. The actual measurement steps will be the number of this setting plus one.

GPIB Command: SETup:CTDPower:STEP:COUNt
Power Step Time
Sets the period (in milliseconds) that the test set will wait to trigger the power measurement for the next step. It determines the successive trigger for the measurement. You must set the MS to hold each step power constant for this amount of time.

GPIB Command: SETup:CTDPower:STEP:TIME
Timeout Time/State - (see Timeouts ).

TX Dynamic Power Measurement Results

Integrity Indicator
GPIB Command: Integrity Indicator
Power Results
The TX dynamic power measurement result is displayed in both a tabular and a bar graph format. See X Dynamic Power Measurement Display .

GPIB Command: FETCh:CTDPower[:ALL]?

X Dynamic Power Measurement Display

Graphical Display

The graphical display shows the measurement result for each step with a graphical "Bar". The x-axis graph represents the number of the power steps and y-axis represents the absolute power of the measurement step in units of dBm/1.23 MH. Up to 100 steps of the measurement results can be displayed on the graph. The view window can be adjusted to include a view of the entire 100 power step range, or reduced to include only the measurement steps of particular interest by the Graph Control softkeys (see Measuring TX Dynamic Power ).

NOTE

The number of displayed bars equals Number of Power Steps plus one. For example, when Number of Power Steps is set to 3, the display shows 4 yellow bars in one measurement.

Marker ( F1 ) - sets a marker position across the current span of the graph. The measurement result that corresponds with the marker position is highlighted in the table below the graphical display. This setting also controls the table scrolling.
Start Step ( F3 ) - sets the first measurement step displayed on the graph. It is used to adjust the view window together with the Span ( F4 ).
Span ( F4 ) - sets the number of measurement steps displayed on the graph. It is used to adjust the view window together with the Start Step ( F3 ).
Default Scale ( F5 ) - sets the Graph Marker, Start Step, and Span to their default values.

Tabular Display

A table below the graphical display lists the absolute power of each step measurement in units of dBm/1.23 MHz. The table has the capacity to display 40 steps of measurement results. To scroll through the table adjust the setting in Marker field.

Input Signal Requirements

The TX dynamic power measurement meets specifications when the following input signal requirements are met:

The frequency of the signal being measured must be within the range of 412 MHz to 483 MHz, 800 MHz to 960 MHz, or 1.7 GHz to 2.0 GHz, and be within 100 kHz of the expected frequency.
The signal level into the test set's RF IN/OUT connector must be between -61 dBm to +37 dBm. The test set can autorange to a signal that is within +/- 9 dB of the expected input level (see RFANalyzer:AUTO:POWer[:SELected]? ).

Calibrating the TX Dynamic Power Measurement

The TX dynamic power measurement is automatically calibrated during a channel power calibration. Follow the channel power calibration schedule and the TX dynamic power measurement will be properly calibrated. Refer to Calibrating the Test Set for a description of channel power calibration.