Senior Project 2005 Electrical Engineering

1. Senior Project 2005 Electrical Engineering Wireless Earphones Avionne Maurice & Jacqueline Suarez Prof. Hedrick & Prof. Hassib Why Wireless earphones? Project Description Wanted to develop a device which hasn’t been explored thoroughly in the wireless field • Wireless earphones are lightweight ear-clip stereo headphones made by Maxell. • The earphones will be used in conjunction with a portable audio player. • Increased range of listening. Receiver (front) Block Diagram Implementation Receiver (back) A CD player was used for the input signal. The audio signal was then received by the FMST-100 stereo transmitter. Within the FMST-100 stereo transmitter the signal is amplified and modulated by the BA1404 IC chip. The signal is then transmitted and received using the antennas. Inside the TDA7000 FM Radio Receiver chip, the signal is demodulated and amplified so it can be heard with the wireless earphones. Project Description Suppression of unwanted signals at 40 dB FM modulation Battery Life of Receiver: 25 hours Battery Life of Transmitter: 25 hours Receiver: Ear-clip size Transmission Range: 200 ft Based on this picture, the side bands follow the FCC requirements. This means the carrier frequency can only travel between -75 to +75 KHz. It is the requirement for two adjacent radio stations on the FM bandwidth. This validates that the suppression of unwanted signals is at 40 dB. Each box has a separation of 10 dB and since the signal is 4 boxes away from the unwanted signal, there is a 40 dB separation.