1 / 22

Basic Concepts

Basic Concepts. Modulation Purposes of using modulation Demodulation Demodulation vs. Detection The whole picture – transmission system Classification of modulations. „Modulation & Detection”  Zdzisław Papir. φ ( t ). x ( t ). MODULATOR. c ( t ). Definition of Modulation.

clay
Download Presentation

Basic Concepts

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Basic Concepts • Modulation • Purposes of using modulation • Demodulation • Demodulation vs. Detection • The whole picture – transmission system • Classification of modulations „Modulation & Detection” Zdzisław Papir

  2. φ(t) x(t) MODULATOR c(t) Definition of Modulation • Modulation involves three signals: • information carrying signal = modulating signalx(t) • carrierc(t) • modulated signalφ(t) • Modulation is mapping of the information signal into one of the parameters of the carrier. • The output signal is called the modulated signal. „Modulation & Detection” Zdzisław Papir

  3. MODULATOR Amplitude Modulation „Modulation & Detection” Zdzisław Papir

  4. t Amplitude Modulation „Modulation & Detection” Zdzisław Papir

  5. – + Baseband Modulation(Line Code) Transition graph for Miller’s code „Modulation & Detection” Zdzisław Papir

  6. – + 1 0 1 1 0 0 0 0 0 1 1 0 1 Baseband Modulation(Line Code) „Modulation & Detection” Zdzisław Papir

  7. S() Bipolar NRZ code – + Miller’s code Biphase code  Power density spectrum Baseband Modulation(Line Code) „Modulation & Detection” Zdzisław Papir

  8. Spectra of information signals Voice - baseband – up to several kHzs Sound - baseband – up to tens of kHzs Video – baseband up to several MHzs Raw data – baseband up to ...? „Modulation & Detection” Zdzisław Papir

  9. Purposes #1 Access to different parts of the electromagnetic spectrum Microwave - MHzs Sattelite - GHzs Copper plant – baseband up to 10 MHz Fiber – narrow frequency window at THzs „Modulation & Detection” Zdzisław Papir

  10. TRANSMISSIONCHANNEL TRANSMITTER RECEIVER noise Purposes #2 Better noise immunity of transmission SNR modulation detection improvment of the Signal to Noise Ratio (SNR) SNR (modulation & detection) > > SNR (baseband system) „Modulation & Detection” Zdzisław Papir

  11. Frequency (FDM) Time (TDM) Purposes #3 Frequency or Time Division Multiplexof transmission channels „Modulation & Detection” Zdzisław Papir

  12. The free lunch does not exist #1 Access to different parts of the electromagnetic spectrum #2 Better noise immunity of transmission #3 Frequency or Time Division Multiplex of transmission channels #4 SPECTRUM WIDENING • B [Hz] or W [rad/s] – spectrum of the modulated signal • fm [Hz] or ωm [rad/s] – spectrum of the modulating signal spectrum wideningcoefficient „Modulation & Detection” Zdzisław Papir

  13. φ(t) x(t) MODULATOR c(t) Definition of Demodulation Modulation is MAPPING the information signal onto the carrier. Demodulation is STRIPPING the information signal from the carrier. φ(t) x(t) DEMODULATOR c(t) „Modulation & Detection” Zdzisław Papir

  14. Definition of Detection Detection is STRIPPING the information signal from the carrier in a noisy environment. x(t) + noise φ(t) DETECTION c(t) „Modulation & Detection” Zdzisław Papir

  15. TRANSMISSIONCHANNEL TRANSMITTER RECEIVER noise modulation detection The Whole Picture „Modulation & Detection” Zdzisław Papir

  16. Transmitter LPF MOD BPF Modulatedsignal Informationsignal Carrier LPF – Lowpass Filter BPF – Bandpass Filter MOD – Modulator „Modulation & Detection” Zdzisław Papir

  17. Receiver BPF DEMOD LPF Modulatedsignal Informationsignal Carrier LPF – Lowpass Filter BPF – Bandpass Filter MOD – Modulator „Modulation & Detection” Zdzisław Papir

  18. Transmission Channel The common assumption is that the transmission channel disturbes the signal being transmitted withthe Additive White Gaussian Noise. AWGN – Additive White Gaussian Noise „Modulation & Detection” Zdzisław Papir

  19. Transmission System LPF MOD BPF BPF DEMOD LPF „Modulation & Detection” Zdzisław Papir

  20. Transmission System Quality LPF MOD BPF BPF DEMOD LPF „Modulation & Detection” Zdzisław Papir

  21. φ(t) x(t) MODULATOR c(t) Classification of Modulations Digital - Analog Digital - Analog • Analog waveform – sin or cos waveform (A) • Digital waveform – sequence of pulses (D) „Modulation & Detection” Zdzisław Papir

  22. Keying GMSK PSK ASK Classics MSK FSK AM QAM FM SSB Samplingtheorem Line codes NRZ Miller PAM PFM PRS HDB PDM Classification of Modulations carrier A A D informationsignal D „Modulation & Detection” Zdzisław Papir

More Related