1 / 13

Variable Low Power FM Transmitter for use with Portable Audio Player

Variable Low Power FM Transmitter for use with Portable Audio Player. Communication Electronics – Dr. Pao-Lo Liu TA – Mr. Saurav Bandyopadhyay Jason Burgess Kee Soon Lim Terry Hudson. Objectives & Goals.

abie
Download Presentation

Variable Low Power FM Transmitter for use with Portable Audio Player

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. Variable Low Power FM Transmitter for use with Portable Audio Player Communication Electronics – Dr. Pao-Lo Liu TA – Mr. Saurav Bandyopadhyay Jason Burgess Kee Soon Lim Terry Hudson

  2. Objectives & Goals • The device will function as a portable wireless FM transmitter with an input from the mini jack of a portable audio device. • The device will adhere to Title 47 of the Code of Federal Regulations (Part 15, subpart C), which states, “the power limit for unlicensed FM transmissions is a signal strength of 250 microvolts per meter, measured 3 meters from the transmitting antenna”

  3. Design Specifications • Transmitter’s frequency range: 88-107Mhz • Effective Transmitter distance: 2-5 meters • Frequency Response: 10khz • Easily Portable • Variable Transmitted Frequency

  4. Final Design Fig 1. The schematic of the final design.

  5. Bread boarded Circuit The Pre-emphasis circuit The amplifier circuit The oscillator circuit Fig 2. Picture of the bread boarded circuit.

  6. Operation and Analysis *The analysis was conducted with use of a Clarion DXZ735MP receiver, the specs are listed below. • FM frequency response 30-15kHz +0.0, -2.1 dB • SNR 74.4 dB mono, 71.2dB stereo • All measurements taken at 89.1 MHz carrier frequency.

  7. Operation and Analysis Fig 3. Output at 100 Hz Fig 4. Output at 30 Hz

  8. SNR • To measure the SNR an audio analysis file was acquired of a 1kHz sine wave. • The peak to peak voltage of a 1kHz sine wave was measured against the no signal noise level at different volumes of the input. Fig 5. SNR data SNR=20 log (Vs/Vn)

  9. Effective Transmitter Distance • The same 1kHz sine wave was used as the input. • The output was measure by the receiver with three foot whip antenna attached. • A simple 18 in. long 20 gauge wire was used as the transmitter antenna. • The effective transmission distance was determined to be the straight line, antenna to antenna distance at which an attenuation of 3dB occurred. • The lab measurement was 6.4m (21 feet)

  10. Frequency Response Figure 6- The output from the transmitter with the pre-emphasis. The –3 dB points are 85Hz, 14.5 kHz. The bandwidth is then 14kHz. Fig 6. Figure 7- The output from the transmitter with out the pre-emphasis. The –3 dB points are 80 Hz, 9.3 kHz. The bandwidth is then 9.2 kHz. Fig 7.

  11. Possible Improvements • Soldering to a printed circuit board • Making use of a better antenna • Indicating transmission frequency on dial • Indicating transmission frequency using 7 segment LED displays.

  12. Time Line

  13. Thank YouAny Questions? REFERENCES [1] http://sound.westhost.com/project54.htm [2] Electronic Communications Systems 5th ed., Tomasi, Wayne, Prentice Hall, 2003

More Related