Basic System Configuration

1. DBM DBM x FM Exciter RF Preamp FM Receiver x Amp/Filter Audio Audio PN Code Generator PN Code Generator Synchro Oscillator Transmitter Receiver Basic System Configuration

2. AFIT BUILT DSSS THEORY OF OPERATION TRANSMITTER So(t) Audio FM Exciter DBM FM Osc BPF X Amp X4 X3 X3 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 38

3. 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 39

4. Theory of Operation(Continued) Power Spectral Density Gb(f) = Tc(sin fTc / fTc)2 Go(f) = PsTc/2{ [sin (f – f0)Tc / (f – f0)Tc]2 + [sin (f + f0)Tc / (f + f0)Tc ]2 }

8. SPECTRAL CHARACTERISTICS Rc = 2.7875 MHz Tc = 0.3587 s N = 255 BW = 5.575 MHz 1/NTc = 10.93 kHz • {Sin (x)/x}2 • Spectral lines – 1/NTc • Null-to-Null BW – 2 * 1/Tc • Number of spectral lines = N 40

10. 41

11. 35

12. FREQUENCY HOPPING CORDLESS TELEPHONE

14. 36

15. Time-Frequency Distribution of FH Radio (a) (b)

16. CORDLESS PHONE WAVEFORMS Base and Handset Unit Handset Unit 44