Tektronix WFM700 Series, Service Manual

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Theory of Operation
WFM700 Series Waveform Monitors Service Manual
1- 3
The Input module is comprised of two circuit boards, a Mezzanine board and an
Input board.
The Mezzanine board provides two terminating serial inputs, each supporting
either SD (SMPTE 259M) or HD (SMPTE 292M) SDI signals. A mux selects
between the two inputs and sends the signal to an eye pattern sampler block and
a serial receiver block (equalizing the signal). The eye pattern sampler block
implements a 3 GHz equivalent-time sampler to allow viewing the input eye
pattern. The equalized SD or HD signal and the eye pattern data samples are sent
to the Input board.
On the Input board, an SD or HD serial-to-parallel block provides clock recovery
and serial-to-parallel conversion of the selected input. An FPGA block multi-
plexes between the eye sampler output and serial receiver block output (depend-
ing on instrument mode), implements any needed waveform conditioning (such
as ancillary data extraction), and outputs the parallel signal (20 bits for HD
mode, 10 bits for SD mode) to the Real-Time Display (RTD) board. The FPGA
block also extracts up to eight channels of audio signal which is put on the audio
bus for future use.
A DAC block creates a picture monitor signal which is output through the VGA
PIX MON connector and the component video connectors (PIX G/Y, PIX B/Pb,
PIX R/Pr) on the Reference Module.
External Connectors
H
INPUT A. Digital input for signal to be monitored. For WFM700HD, this
can only accept 1.485 Gb/s and 1.4835 Gb/s High Definition serial video.
For the WFM700A and WFM700M, this input can accept HD and 270 Mb/s
Standard Definition video. This is a 75
8
terminating input.
H
INPUT B. Digital input for signal to be monitored. For WFM700HD, this
can only accept 1.485 Gb/s and 1.4835 Gb/s High Definition serial video.
For the WFM700A and WFM700M, this input can accept HD and 270 Mb/s
Standard Definition video. This is a 75
8
terminating input.
H
SD PIX MON. This output is a copy of the PIX G/Y, B/Pb, R/Pr pix mon
output, but in reclocked SD serial digital format. It is operational only for
SD input formats.
H
SERIAL OUT. Provides an equalized and buffered version of the selected
signal input (Video Input A or B).
H
JITTER OUT. (WFM700M only) Provides a 75
8
output signal from the
jitter demodulator. This signal is only valid when the instrument is in Jitter
mode. Any signal present on this output at other times is not a calibrated
jitter signal.
Input Module