Class Notes (836,335)
Canada (509,739)
Lecture 8

SFWRENG 4J03 Lecture 8: Lecture 2016-03-29
Premium

6 Pages
36 Views
Unlock Document

Department
Software Engineering
Course
SFWRENG 4J03
Professor
Rong Zheng
Semester
Fall

Description
Lecture 2016-03-29 Author: Kemal Ahmed Instructor: Dr. Gowri Krishnasamy Course: SFWR ENG 4J03 Math objects made using MathType. Table of Contents Spread Spectrum Modulation ......................................................................................................... 1 Baseband..................................................................................................................................... 1 Transmission........................................................................................................................... 2 Receiving................................................................................................................................ 2 Product Modulator.................................................................................................................. 2 Passband...................................................................................................................................... 3 BPSK....................................................................................................................................... 3 Receiver.................................................................................................................................. 3 Channel Output....................................................................................................................... 4 Spread Spectrum Modulation  A type of digital modulation  Spreading the spectrum through Pseudo Noise sequence (PN) code  Despreading is achieved through the same code in R×1  Making the transmitted data appear like noise  Military/security purposes PN Code produced using feedback shift register Types:  Baseband  Passband o Phase Shifting … (PSK): o Frequency Shifting … (FSK): Baseband Transmission: binary data [b(t)] × PN Sequence [c(t)] → O/P m(t) Channel: m(t) + i(t) → r(t) Page 1 of 6 Tb v 1, v 0  r(t) (x) c(t) →0 dt  Decision device, i.e. τ = 0 →0, v 0    v ≠ 0 because you want your signal to appear as noise 1 → +A 0 → –A Integrator is a low-pass filter {bk} → Polar NRZ encoding → b(t) {ck} → Polar NRZ encoding → c(t) digital signal discrete in amplitude & time PN Seq Generated using 3 stage feedback shift register 0011101 time to send an individual binary bit [b ]: number of flip-flops [m]: Bit duration [T ]: c T b NT c N = 2 – 1 = 2 – 1 = 7 Transmission Output of channel [r(t)]: Output of transmission [m(t)]: Interference Signal [i(t)]: m(t) + i(t) → r(t) Receiving r(t) × c(t) → z(t) → bdt v Decision Device, τ = 0 → 1, v 0  0 0, v 0    Product Modulator z(t) = r(t) × c(t) r(t) = m(t) + i(t) = c(t) b(t) + i(t) z(t) = [c(t) b(t) + i(t)] c(t) = c (t) b(t) + i(t) c(t) Page 2 of 6 c(t) = ± 1 2  c (t) = 1  z(t) = b(t) + c(t) i(t) second part removed with LPF because it is high Passband BPSK Passband modulation with BPSK Direct Sequence Spread Spectrum (DSSS): Note: can use any encoding technique! {bk} → Polar NRZ level encoder → b(t) {ck} → Polar NRZ level encoder → c(t) b(t) × c(t) → m(t) m(t) + carrier signal → BPSK Modulator → x(t) Polarity of data sequence, b(t), at time, t + – Polarity of PN + 0 π sequence at time, t – π
More Less

Related notes for SFWRENG 4J03

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit