Tektronix TDS5032, Manual

Page: 46 / 248

Operating Basics
Receiver Sensitivity Measurement
To improve the performance of the application in a noisy environment, the
USB2.0 high-speed device should respond to IN tokens with NAKs when the
signaling level is at or above the specified level.
The Receiver Sensitivity test requires a high-speed data simulator, such as the
Tektronix DG2040 USB Data Generator or a DTG5000 series instrument, to
transmit IN tokens of varying amplitude. The test requires the unit under test to
be placed in the Test_SE0_NAK mode. The host is then replaced by the data
simulator to continue to transmit IN tokens. The signaling amplitude is presented
to the device under test at a level at or above 150 mV. At these levels, the unit
under test must not be in the squelched mode, responding to IN packets with
NAKs. The amplitude of the signals from data simulator varies less than 100 mV.
The unit under test must be squelched and not respond to IN tokens with NAKs.
This tests the receiver capability of high-speed units (device) to respond to the
particular data pattern generated by the USB2.0 data simulator. The unit under
test responds to the data pattern level above the squelch level (>150 mV) and
should not respond when the data pattern level is below the squelch level
(<100 mV).
The TDSUSB2 application provides the procedural steps to perform this
measurement. It also provides Digital signal generator pattern files. Pattern files
for other Tektronix data simulators are available from
www.tektronix.com .
Figure 12: Results of the Receiver Sensitivity measurement
32 TDSUSB2 Universal Serial Bus Measurement Package