HSP50215EVAL Datasheet, PDF (8/45 Pages) Intersil Corporation – DSP Modulator Evaluation Board

HSP50215EVAL
(8)16384
(9)48
(0)Returns to main menu
This configures channel four to be a 351Kbps PSK
modulator at 500kHz with a Gaussian White Noise input and
with the RF severely attenuated so as to be effectively
turned off.
Select main menu item (6), save configuration file and enter
the following file name and path: examples/exercise.
Select main menu (7) to compute the register values.
Select main menu (8) to configure the board.
Select submenu item (5) to configure all channels.
Select submenu item (3) to load both the modulator and
Pattern RAM.
When the submenu reappears, the download is complete
and the scope or spectrum analyzer should show a single
CW tone at 500kHz at approximately 0.4Vpp.
Exercise #2: Adjusting the level of the CW Tone
This exercise will demonstrate the technique used in
adjusting the output amplitude of the CW test tone via the
Gain Control signal of the Digital Upconverter. This is but
one technique that can be used to set the level, noting that
scaling the input file can achieve the same result. The
HSP50215 data sheet notes that care must be taken in
setting the signal level at the input to the shaping filter, at the
input to the interpolation filter, at the input to the mixer, and
at the cascade summer. Attention to these points will
eliminate the unwanted limiting or roll-over. The purpose of
this exercise is to introduce the user to a technique for
setting test signal levels.
Go to the main menu. Select Item (1), Modulator Channel 1
Configuration, and enter the following parameters:
(9)9
(0)Returns to main menu
This will reduce the output level by 6dB.
Select main menu (7) to compute the register values.
Select main menu (8) to configure the board.
Select submenu item (1) to configure channel 1.
Select submenu item (1) to load the modulator.
When the submenu reappears, the download is complete
and the scope or spectrum analyzer should show a single
CW tone at 500kHz at with half the amplitude of the signal in
Exercise 1. Note that if we had set the value to 48, the
channel is effectively turned off. Setting the value to 0 is the
maximum output level, but there is the risk that clipping will
occur when other signals are added into the CW tone.
Exercise #3: Modulating the CW Tone with PN Data
This exercise will demonstrate the creation a BPSK signal
using a Random PN sequence as a stimulus. The BPSK
stimulus will write the following values as (I,Q) pairs into the
modulator: (-0.707, -0.707), (+0.707, +0.707). This will
generate a BPSK signal. The purist may wish to edit this file
to have the values (+1,0), (-1,0), but the 45^o phase offset is
not of concern, in general. The purpose of this exercise is to
demonstrate BPSK and provide insight into creating useful
test stimulus files, as well as to learn techniques for quick
test configuration.
Go to the main menu. Select Item (1) and set the following
parameters:
(8)24
(9)3
(0)Returns to main menu
This will return the output level to the original setting.
Select main menu (7) to compute the register values.
Select main menu (8) to configure the board.
Select submenu item (1) to configure channel 1.
Select submenu item (1) to load the modulator.
When the submenu reappears, the download is complete
and the scope or spectrum analyzer should show a filtered,
modulated signal at an output level of approximately 0.4Vpp.
There should be 10 IF cycles per baud and the baud rate is
50kHz. Notice that it was setting item (8) to 24 that sent a PN
sequence to the modulator. The previous value of 1, held the
modulator at CW using an input of either a (-0.707, -0.707)
or (+0.707, +0.707).
Note that if a particular data pattern is required, copying and
editing the PN stimulus file for the number of data samples
that you desire, is a quick way to perform an impulse
response or some other useful test pattern such as 1/0 or
1000. Just remember to use the channel configuration menu
to only select the number of data samples to match the
entries that you have altered in the new file. Also, selecting a
standard PN length (2⁹-1, 2¹⁵-1) allows a commercial Bit
Error Rate Tester to be used in conjunction with this
modulator in evaluation of the communication link.
Notice also, that the various options for configuring the board
are designed to save time during evaluation. If the only
parameters that have changed involve one modulator, then
the quickest configuration update downloads only the
parameters for that modulator. The next quickest update is if
the Pattern RAM and modulator for that single channel are
all that need downloading. You will appreciate this as you
apply the larger stimulus files, like the AWGN files. The
longest download involves updating the modulator and
Pattern RAM files for all channels.
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