Basic System Configuration

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Basic System Configuration
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AFIT BUILT DSSS THEORY OF OPERATION
TRANSMITTER
So(t)
Audio
FM Exciter
DBM
FM Osc
BPF
X
Amp
X3
X3
X4
ST1(t)
ST2(t)
12.388 MHz
111.5 MHz
PN Code Gen
Divide by 40
bT(t)
2.7875 MHz
Detailed DSSS System Block Diagram
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AFIT BUILT DSSS THEORY OF OPERATION
RECEIVER
SI(t)
DBM
SR1(t)
SR2(t)
X
FM Receiver
Audio
Preamp
446.0 MHz
bR(t)
PN Code Gen
Divide by 40
Synchronous Oscillator
2.7875 MHz
111.5 MHz
Detailed DSSS System Block Diagram
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Theory of Operation(Continued)

• Power Spectral Density
• Gb(f) Tc(sin fTc / fTc)2
• Go(f) PsTc/2 sin (f f0)Tc / (f f0)Tc2
• sin (f f0)Tc / (f f0)Tc 2

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SPECTRAL CHARACTERISTICS
Rc 2.7875 MHz Tc 0.3587 ?s N 255 BW 5.575
MHz 1/NTc 10.93 kHz

• Sin (x)/x2
• Spectral lines 1/NTc
• Null-to-Null BW 2 1/Tc
• Number of spectral lines N

40
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41
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35
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FREQUENCY HOPPING CORDLESS TELEPHONE
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Time-Frequency Distribution of FH Radio
(a)
(b)
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CORDLESS PHONE WAVEFORMS
Base and Handset Unit
Handset Unit
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