1、Modulation and Broadcasting Amplitude Modulation,Basic AM,Modulation Amplitude Spectrum Carrier Sideband Modulation index 0 1?,Waveforms,Base Band and Modulation m = 100% m = 120% Math Real,Spectrum,Double Side Band Full Carrier Spectrum LSB, USB, Carrier,Efficiency,Efficiency in Using Bandwidth? Tw

2、o side bands Efficiency in Using Power? Carrier Side band Information in side band Carrier for synchronization,Variations of AM,Bandwidth Efficiency Single Side Band Vestigial Side Band Power Efficiency Reduced Carrier Suppressed Carrier Complication Circuits: generation, tuning, detection Filter, c

3、arrier recovery, drift,Detection by Nonlinear OperationsRectification Envelope Detector,Circuit RF rectifier Filter RC time constant Simple for high S/N Waveform,Square Law Detection,Square Law Detector Modulation Nonlinearity LF filter Small amplitude and AC coupling,Multiplication Homodyne Detecti

4、on,Baseband Signal Coherent Detection AM modulation Local oscillator Mixer LP filter AC coupling Lower noise,Heterodyne,Incoming RF RF amplifier Bandpass filter Local Oscillator Mixer Nonlinear device or balanced mixer Bandpass filter Signal proportional to local oscillator strength Intermediate Fre

5、quency (AM at 455 kHz) No further tuning,AM Noise Analysis,DSBFC Signal and Noise Signal power: Noise spectral density: Double sideband bandwidth: Total noise power: Intrinsic S/N Coherent Detection In phase noise only S/N,AM Noise Analysis,Envelope Detection Signal Dominant Regime Similar to cohere

6、nt detection Noise Dominant Regime Noise large Signal small with random phase,Lab and Projects,Virtual Laboratory (Search: Amplitude modulation) Matlab project /classes/ee151/Winter01/ Software Radio Simple AM Projects Experiments Agilent 33120 AM modulation MC1496 ,AM Broadcas

7、ting,History Source Audio, 20-20 kHz Carrier Frequency 525 1705 kHz Performance 5 kHz bandwidth 250-500 km range 50 V sensitivity,AM Radio,AM Transmitter,Block Diagram Automatic Level Control m 1,Power AmplifierImpedance Matching,Maximize Power to the Load Impedance Z = V / I Change V I Relation Tra

8、nsformer High current, low voltage Low current, high voltage RLC Networks Frequency dependent impedance,Impedance Matching,MIT Open Courseware Berkeley RLC Pi and T LC Network Calculator Role of Antenna Turning guided electronic signal into radiating wave in free space and vice versa Matching circui

9、t impedance to free space impedance,Commercial AM Radio,Circuit Diagram Tom Wheeler, Electronic Communications for Technicians,Commercial Radio,Circuit Board,AM Receiver,Crucial Components,RF Amplifier High dynamic range Oscillator and Mixer Tuning Loop Antenna LC resonator Intermediate Frequency Am

10、plifiers 455 kHz Tank circuit (double tuner) with flat center band Diode RF Rectifier Envelope detection Automatic Gain Control Strong vs weak stations Audio Amplifier Speaker,Receiver Performance,Sensitivity Fidelity or Bandwidth Dynamic Range Selectivity Adjacent channel Image Rejection IF Spuriou

11、s Response Harmonics Squelch Noises Static noise from transmission media Motor boating noise from drift in frequency,AM Modulators,Modulate oscillator power supply with base band signal. Balanced Mixer Modulate the gain of a linear amplifier with base band signal.,Detection Circuits,Envelope Detecto

12、r RF rectifying diode Filter Heterodyne Circuits Mixer LF,AM Stereo,Two Channels L+R L-R Quadrature Amplitude Modulation Sin, Cos: orthogonal Increase Information Capacity Without Increasing Bandwidth Motorola CQUAM System,HAM,/hamradio.html Spectral analysis of audio signals Anten

13、na projects,Short Wave Radio,Terrestrial Coverage, HAM Regenerative Receiver Project,Modern Application of AM,Advanced Television Systems Committee (ATSC) 8-VSB Digital Signaling ,AM Review,AM Waveform Modulation Index Limit Double Sideband, Full Carrier Variations SSB, RC or SC Vestigial sideband A

14、M Transmitter Impedance matching Efficiency Detection Circuits Coherent detection Envelope detection,Modulation and Broadcasting Angle Modulation,Angle Modulation,General Format Phase Instantaneous Frequency,Phase and Frequency Modulation,Waveform Base band PM FM Constant amplitude No static noise M

15、odulation Index m inversely proportional to fm for FM Spectrum Bessel functions Broader bandwidth Carsons rule: B=2(+fmax),FM Signal,SWCad,FM Modulator Circuits,Varactor Variable Reactance Modulator,FM Detector Circuits,FM Detection Convert frequency deviation to voltage Frequency dependent throughp

16、ut Slope detector Foster-Seeley Discriminator Ratio detector,FM Detector Circuits,Quadrature demodulator PLL LM565,FM Noise,Amplitude Controlled by limiter Driving into saturation Phase Phasor picture Maximum angle deviation White noise,Frequency Error by Phase Noise,Simplified S/N Analysis Signal f

17、requency: 1 kHz Signal amplitude, ES: 10 Frequency deviation: 5 kHz Noise amplitude, EN: 1 (S/N)P: 20 dB Maximum angle deviation: 0.1 rad Noise modulation index, mN: 0.1 Frequency error caused by noise 1 kHz x 0.1 = 100 Hz (S/N)F: 5 kHz/100 Hz = 50; 34 dB in power,FM Noise,Threshold and Capture Effe

18、ct S/N below threshold: poor performance S/N above threshold: improved performance Strong station dominates weak station,FM Noise,Noise in FM system Frequency error: mNfm Larger signal needed at higher frequency Pre-emphasis and de-emphasis High pass and low pass filters,FM Radio,Source Audio, 50-15

19、 kHz Carrier Frequency 88 108 MHz IF 10.7 MHz Performance 15 kHz bandwidth 50-100 km range 10 V sensitivity,FM Radio,Block Diagram,FM Stereo - Frequency Allocation,Sub-Carrier Multiplexing,Stereo Transmitter,Frequency Division Multiplexing 19 kHz Pilot Preemphasis,Stereo Receiver,Practical FM Projec

20、ts,FM Transmitter http:/www.free-electronic- Simple FM Project Regenerative Receiver ,IC-Based FM Radio,Digital Radio,Digital Audio Broadcasting,Eureka Britain: Band III, 174-240 MHz Canada: L-Band, 1452 to 1492MHz Data: 192 kb/s, digital compression iBiquity In band on channel Analog + digital side

21、band Perceptual audio coder SiriusXM Radio,Television,TV Systems,Broadcasting Local station, CATV, satellite Analog Standards NTSC, PAL, SECAM MUSE Digital Standards ATSC DVB-T ISDB-T GB20600-2006,NTSC Signaling,Vertical Scan Lines 525 lines Aspect Ratio 4:3 Frame Rate 30 Hz interlaced 525 lines/fra

22、me x 30 frames/sec = 15.75 kHz Resolution: 0.7-0.75 utilization factor,NTSC Broadcasting,4.75,3.579545,Analog TV Signaling,Composite Video Luminance (brightness) 340 lines Y=0.3R+0.5G+0.11B Chrominance (color); 50-100 lines I=0.6R-0.28G-0.32B Q=0.21R-0.52G+0.31B H Sync V Sync Blanking Color burst,Waveforms,Spectrum,Luminance AM vestigial side band From -0.75 MHz to +4 MHz Chrominance QUAM VSBSC Pilot at 3.58 MHz Sound FM Sub-carrier at 4.5 MHz,TV Receiver Circuits,RF, IF 45 MHz Video Detector Composite Video to RGB Comb filter Audio IF, Audio Detector Sync Separator H Sync V Sync,Block Diag