Digital Signal Processing Reference
In-Depth Information
Time domain
FFT
Freq. domain
An te nn a
Mix ing
IF filter
C o n tro l
Oszi lator
Rectifier
LP filter
Time domain
Frequency domain
7,5
5,0
2,5
0,0
-2,5
-5,0
-7,5
4
3
2
1
0
-1
-2
-3
-4
0,15
0,10
0,05
0,00
-0,05
-0,10
-0,15
0,150
0,125
0,100
0,075
0,050
0,025
0,000
0,09
0,08
0,07
0,06
0,05
0,04
0,03
0,02
0,01
0,00
0,20
0,15
0,10
0,05
0,00
0,15
0,11
0,07
0,04
0,00
0,02
0,02
0,01
0,01
0,00
0,02
0,02
0,01
0,01
0,00
0,02
0,02
0,01
0,01
0,00
525
575
625
675
725
775
250000
500000
750000
1000000
us
Hz
Illustration 168:
Simulation of an AM tuner for the medium wave range
For the sake of simplicity a noise signal is used as an aerial signal, which contains all the frequencies, that
is in the medium wave range from 300 to 3000 kHz (according to CCIR). Using a hand regulator the oscil-
lator frequency can be selected in such a way that the “desired station” lies exactly in the conducting state
region of the IF filter (blackbox). This IF filter is the ingenious bandpass filter from Illustration 166. The
IF filter lies at 465 kHz and a wider filter was selected for the purposes of clearer Illustration. The lowpass
filter also exceeds the actual LF width of an AM receiver.
Surprisingly, the high frequency range can also be simulated by means of DASYLab. The axes are
completely correctly scaled. In this domain real signals can be inputted and outputted by means of very
expensive A/D and D/A cards. .Real time operations - as with a normal radio receiver - can at the moment
hardly be realised.
