Constellation Diagrams; Displaying A Constellation Diagram - Tektronix 11801C User Manual

Displaying a
Constellation
Diagram
11801C User Manual

Constellation Diagrams

A constellation diagram is the result of displaying one data signal against
another in an XY format, resulting in a matrix display of the various signal
levels.This section provides general instructions to help you display a
constellation diagram on the 11801C.
You will need the following equipment:
H A two channel sampling head or two single channel sampling heads
H 3 SMA cables
H A static protection wrist strap
To display a constellation diagram perform the following steps:
Step 1: Press the UTILITY button, touch Initialize in the Utility1 major
menu, and then touch Initialize in the Verify Initialize pop up menu.
Step 2: Put on the wrist strap and ensure that it is connected to the
antistatic connector on the front panel of the 11801C.
Step 3: Connect a cable from signal source 1 (often called the I"
signal) to Channel 1 (for simplicity, we assume you are using a two
channel sampling head).
Step 4: Connect another cable, of the same length, from signal source
2 (often called the Q" signal) to Channel 2.
Step 5: Connect the third cable from your trigger source to the TRIG
GER INPUT connector on the front panel. Be sure not to exceed the
maximum input voltage shown below each of the trigger inputs.
Step 6: Press the TRIGGER button. Touch the Source selector in the
Trigger major menu. Touch External Direct.Touch Exit to remove the
pop up menu.
Step 7: Turn on Channel 2 by pressing the select channel button next to
the input connector.
Step 8: Turn on Channel 1 by pressing the select channel button next to
the input connector.
Step 9: To acquire a constellation diagram, you need to sample the
data on both channels at a point where it is stable (this is, not transition
ing between states). See Figure 3 11.
3 25