MAPUA INSTITUTE OF TECHNOLOGY SCHOOL OF ELECTRICAL, ELECTRONICS AND COMPUTER

ENGINEERING

PROT OT YPE: W i r e l e ss A u d i o a n d V i d e o T r a n s m i tt e r

Fi nal Doc ume nt ati on

Communications 3 Laboratory

Lalim, Maria Leonora DC. Serdon, Mark Zaidy M.

Vergara, Eureka V.

E n g r . F l o r d e l i z a L . V a l i e nt e Professor

I . L e tt e r o f T r a n s m i t t al November 29, 2011

School of EE-ECE-CpE

Mapua Institute of Technology

Muralla St., Intramuros, Manila

Dear Engr. Flordeliza L. Valiente,

In compliance with the fulfillment of the requirements on the course ECE123L, we will be submitting the prototype, "Wireless Audio and Video Transmitter" in accordance with your instructions

This documentation includes information with regards to the prototype's operation and principles. It also includes the project circuit diagram that has been used. It also contains details on how the circuit works, its components, its effective bandwidth of operation and some limitations of the device.

Thank you!

Sincerely yours,

LALIM, Maria Leonora DC.

SERDON, Mark Zaidy M.

VERGARA, Eureka V.

II . Ac k n o w l e d g e m e n t :

First of all, we would like to thank God for giving the ability to accomplish

the task given to us. We would like to thank our professor, Engr. Flordeliza L.

Valiente, for giving us the opportunity to design a wireless audio and video

transmitter antenna and for teaching us the principles regarding the transfer of

information from a transmitter to a receiver through different types of medium. It

gave us the idea on how such a device works and its components. We would also

like to thank Alexan Enterprises for the Home Video Distribution Kit which we

used as a basis in designing our own wireless audio video transmitter. To those

friends and colleague who lends us helping ideas through the process of this

project. Sincerest gratitude to all of you!

III . T h e o r i e s a n d P r i n c i p l e s

A transmission medium can be generally categorized as either guided or

unguided. Guided transmission media are those with some form of conductor

that provides a conduit in which electromagnetic signals can propagate.

Unguided transmission media are wireless systems and do not have physical

conductors. The direction of propagation in an unguided transmission medium

depends on the direction in which the signal was emitted and any obstacles the

signal may encounter while propagating. Signals propagating down an unguided

transmission medium are available to anyone who has a device capable of

receiving them. The most widely used and available unguided transmission

medium is the air or free space. An antenna is a conductor that can act as a

transducer that converts electrical energy into electromagnetic waves ready for

transmission, and electromagnetic waves into electrical energy.

Electromagnetic waves are caused by the interaction between an electrical

current and a magnetic field. Unlike other waves, the energy streams caused by

the interplay of magnetic and electrical forces can travel through empty space.

An RF modulator is a device that takes a baseband input signal and outputs

a radio frequency-modulated signal. This is often a preparation step in

transmitting signals, either across open air via an antenna or transmission to

from a composite video, RGB, YUV or internal source, and generate a PAL

or NTSC broadcast signal that can be fed into a television's aerial/coaxial

connector.

Multi-channel RF modulators are commonly used in home audio/video

distribution. These devices have multiple audio and video inputs and one RF

output. Audio/video outputs from source devices such as a DVD player, VCR, or

DSS receiver are connected to the audio/video inputs on the modulator. The

modulator is then programmed to broadcast the signals on a certain frequency.

That RF broadcast is then received by the connected TV. When the TV is tuned to

the programmed channel, the audio/video signal of the source device is accessed.

I V . S t a n d a r d U s e d

We used the BS-905-2 standard regarding sound and television broadcast

receivers and associated equipments.

V . De s c r i p t i o n , F u n c t i on a n d L i m i t a t i o n s o f t h e P r o j ec t .

The MC1374 is a Television modulator IC that includes an FM audio

modulator, sound carrier oscillator, RF oscillator, and RF dual input modulator. It

is designed to generate a TV signal from audio and video inputs. The MC1374's

wide dynamic range and low distortion audio make it particularly well suited for

applications such as video tape recorders, video disc players, TV games and

subscription decoders.

A 10 V DC supply was used to power the MC1374 IC. The audio and video

input signals must be modulated to develop a signal which can be readily

transmitted using the antenna. The input audio signal must undergo frequency

modulation and amplitude modulation. The video signal will undergo amplitude

modulation only. First, the sound oscillator circuit connected at pins 2 to 3

produces the carrier signal needed to modulate the frequency of the input audio

signal. The frequency of the oscillator input can be varied by adjusting the

capacitances and inductances of the LC tank circuit connected to pins 2 and 3. It

will result to a different resonant frequency which will also change the frequency

of the input signal from the sound carrier oscillator. Pin 14 of the MC1374 is

internally connected to the FM modulator as shown in the pin assignment of the

IC. The audio signal will be modulated to the desired signal frequency for

IC will provide the radio frequency signal to be used for the amplitude modulation

of the input audio and video signals. The amplitude of the carrier produced by this

oscillator is controlled by the components of the LC circuit of the oscillator. The

resistors in the LC tank are used to control the quality factor of the filter circuit.

The transistors circuits connected to pin 9 of the IC are used for vestigial sideband

modulation. To reduce the bandwidth of the video signal to be transmitted,

vestigial sideband modulation will produce a suppressed sideband from the input

video signal that is to be transmitted instead. Finally, the inductors connected to

the antenna are used as loading coils which increases the electrical length of the

antenna and at the same time provide a better match to the characteristic

impedance of the antenna.

The transmitter will only operate at a frequency range of 66 Mhz to 72 Mhz

or the channel 4 of a television. The transmitter should not be placed far from the

receiver for a clear reception of signal.

V I . C i r c u i t D i ag r a m s

Schematic Diagram of the Transmitter

Pin Assignments of the MC1374 C

V III . T a b u l a t e d L i s t o f m a t e r i a l s

Material Quantity PriceResistor

0.25 W ratingg25 pieces

575.00 php

Ceramic Capacitor 50 V ratingg

8 pieces

NPO type Ceramic Capacitor 50 V ratingg

3 pieces

Electrolytic Capacitor 16 V ratingg 3 pieces

Electrolytic Capacitor 20 V ratingg 1 piece

Polystyrene Capacitor 50V Ratingg 2 pieces

3 - 1/2 T X 4 mm Coil 4 piecesAntenna Matching Coil 1 piece

21806/01-8Sound Subcarrier Coil

1 piece

Trimmer Resistor 0.25 W ratingg

1 piece

Trimmer Capacitor 50 V ratingg 2 pieces

MC1374TV Modulator Chip 1 piece

2SC1923NPN RF Transistor 1 piece

MPS6507NPN RF Transistor

1 piece

PN100NPN Transistor

1 piece

1N148Silicon Diode

1 piece

1N5240 7910gZener Diode 1 piece

1N4001Rectifier Diode 4 pieces

Step Down Transformer 1 piecePrinted Circuit Board 1 piece 90.00 php

Total 665.00 php