Teledyne LeCroy QPHY-UWB - Manual (Page 17)

QPHY-UWB Software Option
QPHY-UWB-OM-E Rev C
17
Modifying the Symbol Timing Window
In some radios the switching of the carrier may happen a little late causing excessive carrier leakage into the next
symbol out-of-band spectrum. The WiMedia C&I specification allows the FFT gate timing to be offset in order to
minimize such prior symbol carrier leakage. The Start offset adjustment is provided for this purpose. The
Duration adjustment is provided to allow some freedom in troubleshooting possible problems by allowing full
adjustment of the FFT gating.
These controls are disabled when the Use Defaults checkbox is checked. Access the 2 numeric selections by un-
checking the Use Defaults checkbox.
Start Offset
This numerical control lets you modify the point in the gap (between symbols) when the analysis expects the RF
radio transmitter to have switched bands. The default value is 0 ns, which corresponds to the 5
th
sample before
the nominal symbol start at the base sample rate (528 MS/s). The WiMedia PHY Compliance and Interoperability
Test Specification (hereafter referred to as the C&I specification) allows the start value to be varied to find a time
that minimizes local oscillator leakage or other issues, in order to pass the PSD mask and adjacent channel
power ratio (ACPR) tests. The same start position must be used for both tests.
Duration
This is the time interval between each symbol. Default value is 303 ns.
The duration of each symbol plus the gap (between the symbols) is nominally 312.5 ns. The nominal duration of
the symbol without the gap is 242.42 ns (303 ns are 160 baseband sample times).
The C&I specification does not allow the duration to be changed, for C&I testing the duration must be the default
value, 303 ns.
Use Defaults Checkbox
Checking this box forces the Start offset and Duration controls to default values, and makes them read only.
Select this checkbox to force settings to be appropriate for WiMedia compliance testing. Deselect this checkbox to
gain control of the Symbol section (Start offset and Duration dialogs).
Selecting the PSD Test Type
The control labeled Show allows the user to switch the display between the Mask pass/fail test view and the
ACPR values test view.