SELECTED RF BLOCKS IN VHDL-AMS
171
Model interface
Figure 7-36. Schematic symbol of AWGN channel
Table 7-29. Model ports
Name Type
Description
P_IN ELECTRICAL
Connection
pin
P_OUT ELECTRICAL
Connection
pin
Table 7-30. Model parameters
Name
Unit
Default value
Description
PS_DBM
dBm
-100.0
Input signal power in dBm
S_TO_N dB
100.0
Signal-to-noise
ratio
FS_NOISE
Hz
1.0e06
Sampling frequency of noise signal
TD
s
0.0
Time delay for input signal
RIN Ohm
50.0 Input
resistance
ROUT Ohm 50.0
Output
resistance
Model implementation
The core of the model is the following digital process that generates time
discrete white Gaussian noise.
process is
variable X1,X2,X: REAL := 0.0;
variable SD1: POSITIVE := 111;
variable SD2: POSITIVE := 333;
begin
UNIFORM(SD1, SD2, X1); -- uniform gives a value 0<x<1
UNIFORM(SD1, SD2, X2); -- defined in ieee.math_real
X:=VN*COS(MATH_2_PI*X1)*SQRT(-2.0*LOG(X2));
S_NOISE<=X;
wait for PERIOD;
end process;
The complete model is included on the CD-ROM that is provided with
this book.
Simulation example
In the simulation example a single-tone of 1 kHz and 30 dBm was fed
to the channel model, which is parameterized with a signal-to-noise ratio of
Summary :
Model parameters Name Unit Default value Description PS_DBM dBm -100.0 Input signal power in dBm S_TO_N dB 100.0 Signal-to-noise ratio FS_NOISE Hz 1.0e06 Sampling frequency of noise signal TD s 0.0 Time delay for input signal RIN Ohm 50.0 Input resistance ROUT Ohm 50.0 Output resistance Model implementation The core of the model is the following digital process that generates time discrete white Gaussian noise.
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