d15 Modem Integration and Application Developers Guide version draft 0.53 Page 174 of 181
from less obvious sources such as mixed products. The method provides information on how much effort, if
any, needs to occur to resolve desense problems.
This method is useful when connection of the wireless card is not yet facilitated by the platform. This
measurement could be performed without the wireless card present. This method determines the magnitude
of the emissions without extensive test facility requirements.
Figure 31 - Spectrum Analyzer setup
8.
Preparing the Device Under Test
All battery-operated portable devices implement power management. This means devices are shut down in
stages as time elapses. To provide an effective test condition, each product should include a test mode in
software that powers up all non-passive circuitry. In addition, you are advised to deploy a pseudo-random-
based routine that exercises all circuit blocks and peripherals. This ensures that desense testing considers the
worst-case scenario.
PMIT testing can take up to three hours to complete. The device under test (DUT) must remain powered
during the entire test cycle. For this reason, use external power sources to maintain operation during testing
when possible. Typical circuit blocks to power on and exercise include:
•
Display characters and backlighting
•
Interface drivers and power supplies
•
Keyboard scanning
•
Peripheral silicon
•
Mass storage devices and controllers
You can also emulate keyboard or tablet activity. Some devices generate the bulk of their emissions during
user interaction.
9. Performance
Goals
Network coverage is the ultimate goal of emissions control. The allowable emissions levels are a function of
the radio sensitivity and the required network coverage.
Device under test (DUT)
Measurement antenna
Coaxial connection to measurement antenna
Spectrum analyzer
low noise amplifier (LNA)
(Minicircuits ZFL-1000GH)
