Lecture Radio Communication Circuits: Chapter 7&8 - Đỗ Hồng Tuấn

Lecture "Radio Communication Circuits: Chapter 7&8" presents the following contents: Analog Modulation Circuits (Amplitude Modulation, Frequency Modulation, Phase Modulation), Digital Modulation Circuits (ASK, FSK, PSK, QPSK, M-ary PSK DPSK, M-ary QAM). Invite you to consult.
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Lecture Radio Communication Circuits: Chapter 7&8 - Đỗ Hồng Tuấn Chapter 7: Analog ModulatorsDept. of Telecomm. Eng. CSD2012Faculty of EEE 1 DHT, HCMUT References[1] J. J. Carr, RF Components and Circuits, Newnes, 2002. Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 2 DHT, HCMUT Analog Modulation Amplitude Modulation:  Standard amplitude modulation (AM) with carrier.  Suppressed-carrier double-sideband modulation (DSB).  Single-sideband modulation (SSB).  Vestige-sideband modulation (VSB). Frequency Modulation Phase Modulation Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 3 DHT, HCMUT Standard AM (1) AM signal and spectra: The AM signal is: where µ is positive constant called AM modulation index, x(t) is message, Accosωct is carrier signal. Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 4 DHT, HCMUT Standard AM (2)Message spectrum with bandwidth W:AM spectrum: AM bandwidth is 2W Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 5 DHT, HCMUT Standard AM (3)AM transmitted power:where Pc represents unmodulated carrier power:and Psb represents power per sideband:where Sx is average message power.If fc >>W and µ ≤ 1, then the message can be extracted from xc(t) by asimple envelope detector. Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 6 DHT, HCMUT Standard AM (4) Product modulator for AM:  Using Multiplier: Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 7 DHT, HCMUT Standard AM (5)  Using square-law element:Dept. of Telecomm. Eng. CSD2012Faculty of EEE 8 DHT, HCMUT Standard AM (6) We assumed that the nonlinear element approximates the square law transfer curve: Thus, with  High-level modulation using class C amplifier:Dept. of Telecomm. Eng. CSD2012Faculty of EEE 9 DHT, HCMUT Standard AM (7) AM demodulation:  Synchronous detection (coherent detection): The oscillator of demodulator is exactly synchronized (both phase and frequency) with the carrier. Using PLL for carrier synchronization. Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 10 DHT, HCMUT Standard AM (8)  Envelop detection:Dept. of Telecomm. Eng. CSD2012Faculty of EEE 11 DHT, HCMUT (Suppressed-Carrier) DSB (1) DSB signal and spectra: The wasted carrier power in AM can be eliminated by setting µ = 1 and suppressing the carrier-frequency component. The resulting DSB signal is: Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 12 DHT, HCMUT (Suppressed-Carrier) DSB (2)DSB transmitted power: Product DSB modulator:  Balanced modulator: Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 13 DHT, HCMUT (Suppressed-Carrier) DSB (3)  Ring modulator:Dept. of Telecomm. Eng. CSD2012Faculty of EEE 14 DHT, HCMUT (Suppressed-Carrier) DSB (4) DSB demodulator:  Synchronous detection (coherent detection): As AM demodulator. Required carrier synchronization.  Envelope reconstruction (for suppressed carrier modulation): Required carrier synchronization. Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 15 DHT, HCMUT (Suppressed-Carrier) DSB (5)  Using pilot carrier:Dept. of Telecomm. Eng. CSD2012Faculty of EEE 16 DHT, HCMUT (Suppressed-Carrier) SSB (1) SSB signals and spectra: SSB bandwidth and power: Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 17 DHT, HCMUT (Suppressed-Carrier) SSB (2) SSB modulator:  Based on DSB and filter: Two-step SSB modulator: Dept. of Telecomm. Eng. CSD2012 Faculty of EEE 18 DHT, HCMUT (Suppressed-Carrier) SSB (3)  Phase-shift method: HQ(f): 90o phase shifterDept. of Telecomm. Eng. CSD2012Faculty of EEE 19 DHT, HCMUT (Suppressed-Carrier) SSB (4)  Weaver method:Dept. of Telecomm. Eng. CSD2012Faculty of EEE 20 DHT, HCMUT