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Concept of Dimensionality

Concept of Dimensionality. Concept of Dimensionality (Cont.). PROCESSING GAIN = P G. Processing gain is the improvement seen by a spread spectrum system in SNR, within the system’s information bandwidth, over the SNR in the transmission channel. P G = B S / B i = R S / R i.

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Concept of Dimensionality

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  1. Concept of Dimensionality

  2. Concept of Dimensionality (Cont.)

  3. PROCESSING GAIN = PG Processing gain is the improvement seen by a spread spectrum system in SNR, within the system’s information bandwidth, over the SNR in the transmission channel. PG = BS / Bi = RS / Ri Typical PG = 20 to 60 dB

  4. JAMMING MARGIN = MG Jamming margin takes into account the requirement for a useful system output SNR and allow for internal losses. MG = GP – [Lsys + (S/N)out ] , dB Where, Lsys = system implementation losses (S/N)out = SNR at information, despread, output

  5. DIGITAL MODULATION TECHNIQUES • Information signals (baseband signals) must be processed before transmission to be compatible with the channel • A baseband signal modulates a high frequency carrier by varying the carrier’s phase, amplitude, or frequency • In digital systems there are 3 basic modulation schemes: • Phase shift keying (PSK) • Amplitude shift keying (ASK) • Frequency shift keying (FSK) • In general modulated signal is of the form: S(t) = A(t) cos [2pfo t + f(t)]

  6. Binary Phase Shift Keying (BPSK)

  7. BPSK Circuit Implementation

  8. Binary Amplitude-Shift Keying (BASK)

  9. Spectrum of BASK • ASK differs from PSK in that ASK has carrier component due to DC value of m(t)

  10. Binary Frequency-Shift Keying (BFSK)

  11. BFSK Power Spectrum

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