STEL-1209/CE Intel, STEL-1209/CE Datasheet - Page 12

• Manufacturer Part Number: STEL-1209/CE
• Description: BPSK/QPSK/16 QAM Burst Modulator Assembly
• Manufacturer: Intel

Guard Time
The minimum guard time required between each burst
is 2 symbols. The maximum guard time available is
given by Guard Time (max) = 16383 - Packet Length -
Preamble. The default guard time is 526 symbols which
equals the sum of 14 preamble and 512 data symbols.
This will burst on and off at a 50% duty cycle.
In conjunction with the STEL-9244 burst receiver, a 50%
duty cycle makes it easy to test BER performance.
MODULATOR OUTPUT
There are three Frequency Code Word registers in the
STEL-1109.
indicated by the selected button (default is labeled A
located just beneath the label “NCO Frequency (Hz)”).
The content of the three Frequency Code Words are
shown through the three boxes below the three buttons.
Their content are modifiable but it will only take effect
after the Enter key is pressed.
Attenuation Step
This controls the attenuator on the STEL-1209 board in
1 dB steps, from 0 to 15 dB.
Freeze NCO SIN output
This button collapses the constellation onto the I axis. It
can be used in BPSK mode to rotate the constellation by
45°.
Invert Spectrum
The output of the I- and Q-channel adder block in the
STEL-1109 normally provides an output of the form
Icos(wt) + Qsin(wt). By selecting the Invert Spectrum
button this will be changed to -Icos(wt) + Qsin(wt).
This interchanges the upper and lower sidebands of the
signal, thereby inverting the spectrum.
MODULATION FORMAT
Modulation Type
Four buttons are provided to allow selection of any one
of four modulation types; 16QAM, QPSK, BPSK, and
continuous waveform (CW).
Modulation Mode
Three modulation modes for each modulation type
(expect CW) are provided; Continuous, Burst Auto
repeat, and Burst Qty. To transmit a fixed number of
bursts, the desired number can be specified in the box
provided below the Burst Qty button. The <Enter> key
sends the specified number of bursts each time it is
pressed but only when the Burst Qty box is the active
box. When other parameters are edited, the Enter key
STEL-1209
The active Frequency Code Word is
12
will not cause another burst cycle. For example, if the
Burst Qty box has a value of 5, changing the preamble
value to 2 and pressing the Enter key does not cause the
Burst Controller to fire 5 bursts with 2 preamble
symbols. Instead, the cursor has to re-select the Burst
Qty box and the Enter key must be pressed again.
DATA AND TIMING
Preamble Source
The user has a choice of preamble sources. A specific
pattern for the preamble can be pre-stored in internal
SRAM or taken from J1 (external data source). Default
preamble bit pattern is 11 11 11 00 00 11 00 00 00 00 00
00 00 00.
Data Source
Likewise, data can be stored in internal SRAM or taken
from external data source (J1). The STEL-1209 also has
capability to generate two types of pseudo random
codes; [10,3] and [23,18] that can be used in place of the
data.
Data Clock Source
The STEL-1209 can be configured to be self sufficient in
terms of clock signals. In this state, the on-board 102.4
MHz crystal oscillator generates the master clock and
all other clocks are derived from it. This state is called
the master mode. It is also possible to configure the
STEL-1209 board into slave mode in which an external
continuous bit rate clock must be applied to J6 (EXT
TCLK). This feature is useful in applications where
data must be synchronized to an external reference
clock. Select External TCLK if this is warranted by the
application.
Bit and Symbol Mapping
16QAM modulation requires all internal resources to
map its constellation. In QPSK or BPSK, less constel-
lation is needed and it is therefore possible to map these
constellations (QPSK and BPSK’s) to those vacated by
the 16QAM constellation. Some amount of gain could
thus be gained by the QPSK or the BPSK modulation.
CONFIGURE
This button which is located at the lower right hand
corner of the main screen can be used to do an overall
loading of all the registers with values as presented by
the GUI software.
RESET 1209
This button resets the STEL-1209 board by software
command.