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HSP50215EVAL

DSP Modulator Evaluation Board

Intersil 

HSP50215EVAL

Exercise #4: CW and a Modulated Signal

This exercise simulates a CW jammer interferer with a signal

of interest. The affect of interference is determined by how

close in frequency the CW is to the desired signal and what

the relative amplitude is to the signal of interest. We will use

the pre-configured channel 1 as the modulated signal and

configure channel 2 to be the interfering CW. The purpose of

this exercise is to introduce the user to simple dual channel

operation.

Go to the main menu. Select Item (2) and set the following

parameters:

(8)1

(9)6

(0)Returns to main menu

This will set channel 2 to CW at 3dB lower than the

modulated signal level and at half the frequency.

Select main menu (7) to compute the register values.

Select main menu (8) to configure the board.

Select submenu item (2) to configure channel 2.

Select submenu item (3) to load both the modulator and

Pattern RAM.

When the submenu reappears, the download is complete.

This particular signal is easier seen on the spectrum

analyzer than the scope. The CW is set at half the frequency

of the modulated signal. By turning one of the signals on and

off you can convince yourself that the desired combination of

signals is present. The power of the four channel modulator

should now be apparent. For signal testing, it is possible to

generate the signal of interest, two adjacent signals, and an

interferer signal. This test configuration is ideal for high

signal to noise, multi-channel applications.

Exercise #5: A Fourier Series Composite Signal

This exercise will demonstrate the use of 3 modulator

channels configured as CW tones. The fundamental will be

set at 12dB attenuation, the second harmonic at 18dB

attenuation and the third harmonic at 24dB attenuation. The

purpose is to introduce the operator to multiple channel

configurations.

Go to the main menu. Select Item (1) and set the following

parameters:

(8)1

(9)18

(0)Returns to main menu

Select Item (2) and set the following parameters:

(8)1

(9)12

(0)Returns to main menu

Select Item (3) and set the following parameters:

(8)1

(9)24

(0)Returns to main menu

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.

The output is the composite of three CW tones related by

harmonics and set at decreasing amplitude. The result is a

cyclical output. Note that the relative start phase of each CW

tone on each channel is determined by the relative time of

the channel configuration load. For example, by

reconfiguring individual channels (modulator only) you can

change the relative phase of the CW’s, changing the Fourier

Series, resulting in a different shape output waveform. You

may also find it interesting to adjust the amplitudes to try and

approximate a square wave. Adding the fourth modulator will

improve the approximation, remembering that these

exercises depend on the configuration returning to the last

one called out, in order for the next exercise to work.

Exercise #6: Generating Additive White Gaussian

Noise (AWGN)

This exercise will demonstrate the use of the “gn” stimulus

files. Noise will be considered alone, at first, then a

modulated signal will be added. The Gaussian Noise

stimulus files were generated with MATLAB® using the code

commands:

a = randn(8192,2);

b = 0.25*[a(:,1)/std(a(:,1)),a(:,2)/std(a(:,2))];

This is a sequence of numbers that are randomly selected in

the range of [-1 to +1], scaled by 0.25 for 4σ limiting,

normalized to set the standard deviation to exactly 0.25. This

baseband signal is input at the sample rate and will be

modulated to the IF set in parameter (1) of the modulator

channel being used for noise generation. As a rule of thumb,

set the AWGN sample rate to either a value that is at least

10 times the data sample rate, or at a value close to the IF

BW, but make it a prime number not an even multiple of the

data sample rate. The other parameter that determines the

randomness of the noise is setting (8), the number of data

samples. Two stimulus files have been created and the file

name includes the number of samples. The pn16k file has

16K data samples and the pn8K has 8K data samples. Since

the noise is averaged over the number of samples, once the

number becomes relatively large, the differences is primarily

9

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