Teledyne LeCroy QPHY-UWB - Manual (Page 7)

QPHY-UWB Software Option
QPHY-UWB-OM-E Rev C
7
BASIC SETUP FOR CAPTURING UWB PACKET OVER CABLE
Configure the UWB transmitter to be tested to the desired Band group, TFC, and data rate. It will make setup of
the trigger easiest if your transmitter can be put in a mode to continuously send out packets. The trigger can still
be setup even if you can only send out a finite burst of packets or even only 1 packet at a time, but it is a little
more difficult. Cable the antenna output of the transmitter to the input channel of the oscilloscope. Note for
40GS/s sampling rate only channel 2 or 3 can be used. If the UWB radio needs to be transmitting over the air
simultaneously with the capture of the signal, then use an appropriate power splitter to split the signal between
the antenna and the oscilloscope.
Sample Rate and Bandwidth Setup
Set up the oscilloscope sample rate and bandwidth according to the table below. Except for use with band group
1, the oscilloscope should be set to DBI mode on. This is accessible under the Timebase menu. Make sure that
the Timebase mode is set to Fixed sample rate. You do not want this changing while you are making a
measurement.
Band
Group
Oscilloscopes Bandwidth Sample Rate DBI Mode on? Channel
1 SDA760Zi/DDA760Zi/
WP760Zi/SDA6000
SDA9000
SDA11000
SDA13000
6 GHz 20 GS/sec No Any
2 - 3 SDA9000
SDA11000
SDA13000
9 GHz
11 GHz
13 GHz
40 GS/sec Yes 2 or 3
4 - 6 SDA11000
SDA13000
11 GHz
13 GHz
40 GS/sec Yes 2 or 3
Vertical Setup
Start with a vertical sensitivity of 50 mV/div. After you capture the first few packets, set the vertical sensitivity
control to variable and adjust the V/div so the packet amplitude takes up at least 6 vertical divisions, but doesn’t
go off-screen.
Trigger and Timebase Setup
Set trigger to edge trigger with a trigger level of about ½ division (25 mV). Using the trigger delay control, place
the trigger position at about 2 divisions from the left of the screen. The trigger will not trigger precisely at the same
time each sweep, so you need to leave some room on the left of the screen. You also need to insure that there is
at least 200 nsec of inter-packet gap captured before the packet starts in order for the software to recognize the
packet as a complete packet for analysis. Set the time per division to a long enough time to capture the number of
packets you wish to analyze at a single time. Adjust trigger level to give most stable trigger. This may take some
back and forth if your transmitter is not transmitting a continuous stream of packets.
Note: According to the MultiBand OFDM Physical Layer Specification 1.1 (©2005 MultiBand OFDM Alliance and WiMedia
Alliance), EVM is only computed on data symbols. With a Standard preamble, the first data (PSDU, payload) symbol is symbol
43.
Although our software does not require it, you should acquire full packets. The WiMedia PHY Compliance and Interoperability
Test Specification (v1.0, September 1, 2006) says “EVM shall be computed over at least 3 packets with a payload of at least
96 symbols each. If the measured EVM is within 2 dB of the specified EVM maximum in absolute value, abs (measuredEVM -
specEVM) < 2 dB, then the EVM should be re-measured over an average of 10 packets to ensure accuracy of the
measurement”.
Please see the WiMedia PHY Compliance and Interoperability Test Specification for more details.
When you have at least one full packet on the screen, then you can proceed to analyze the packet which is
described starting on page 9.