1 / 21

Amplitude Modulated Radio Frequency Transmission System

Amplitude Modulated Radio Frequency Transmission System. Instructor: Dr. Fu By: Megan Myles, David Jackson, and Edwin Wambwa. Introduction.

skyler
Download Presentation

Amplitude Modulated Radio Frequency Transmission System

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. Amplitude Modulated Radio Frequency Transmission System Instructor: Dr. Fu By: Megan Myles, David Jackson, and Edwin Wambwa

  2. Introduction An amplitude modulated radio frequency transmission system consists of a modulator in which a sinusoidal high frequency carrier waveform cos(2πfct) is amplitude modulated (AM) by a lower frequency signal vm(t), containing the information to be transmitted. This is also known as the intelligence signal.

  3. Modulation • There is only one sine wave at a given frequency, so how does the information get carried at a particular frequency? • Modulation = Encoding information on a signal • Analog radio modulation technologies: • FM = Frequency Modulation • AM = Amplitude Modulation • PM = Phase Modulation

  4. AM Modulation

  5. AM/FM Difference • But AM can transmit over longer distances because AM frequencies bounce off ionosphere and diffract around hills and buildings but FM frequencies are absorbed, causing “shadows” • PM is analogous to FM.

  6. Am Modulator/transmitter Tuned Circuit Receiver RF Amplifier Peak or envelope detector Audio Frequency Transistor Amplifier Frequency Spectrum of a AM signal Basic Principles of AM Radio Transmissions

  7. AM Block DiagramProject Plan

  8. LC Tuned Circuit • Inductor = 8.2 µH • Capacitor = .33 µF • Resonant Freq. = 96.75 kHz • Resistor = 1 kOhm

  9. . AM Transmitter Block

  10. Project Schematics • LC resonant frequency = 1Vp-p 96.75117220964837 kHz • Intelligence signal = 5 kHz, -1Vdc offset, 400mVp-p

  11. AM Waveform Key • Yellow- Carrier Signal • Blue- Intelligence Signal • Purple- Transmitter output modulated waveform

  12. AM Frequency Spectrum Key • Cursor 1- Center Frequency 96.75kHz • Cursor 2- Upper Sideband 101.7kHz

  13. Transmitted AM signal 3dB cutoff difference between center and sidebands

  14. AM Receiver Circuit

  15. Peak (Envelope) Detector . • Key • 2πfc > 1/R3C2 > 2πfi • 607905.5438 > 40000 > 31415.92654 • R3 = 2.5 kOhms • C2 = .01 µF

  16. Trouble Shooting • AM envelope disappeared when transmitter was connected to receiver • Used resistors as a simulated test resistance for antenna • Receiver output signal obtained • Used potentiometer to fine tune antenna resistance • Receiver output matched original intelligence input .

  17. Complete System/Recovered Intelligence . • Key • Yellow=carrier Input (1Vp-p, 96.75117220964837kHz) • Blue=intelligence input (400mVp-p, 5kHz, -1Vdc offset) • Purple= amplitude modulated transmitter output (20Vp-p, 96.75117220964837kHz) • Green=receiver output (400mVp-p, 5kHz, 90 degrees out of phasewith original intelligence)

  18. Project costComponents and Parts: $55Some components were acquired from Yomi’s stock pile. Man Hours:Approx 60Hrs .

  19. Challenges . • Sound output after designing a higher gain amplifier circuit (we designed for a single toned sound output). • Signal transmission using aerials instead of hard wiring the circuit. • Implementation of a tuning circuit (AFC) in order to receive an audible signal

  20. Conclusions . The experiment was well understood and gave us a better insight into our understanding of AM and FM. We implemented similar labs throughout the course, but were able to combine methods of radio transmission into a complete transmission system.

  21. Fin .

More Related