CHAPTER ONE
GENERAL INTRODUCTION
1.1 Introduction
In electronics and telecommunications, a transmitter or radio transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. It is hard to imagine what the modern world would look like without the constant exchange of a huge quantity of information. It is currently disseminated by various means such as newspapers, telephone and the Internet. However, the fastest way, and sometimes the only way, is by radio. This is where the transfer is by electromagnetic waves, traveling at the speed of light. In radio communication, a radio transmitter comprises one side of the link and a radio receiver on the other. No conductor of any kind is needed between them, and that’s how the expression Wireless Link came into being. In the early days of radio engineering the terms Wireless Telegraph and Wireless Telephone were also used, but were quickly replaced with Radio Communication, or just Radio. Radio communication is created by means of electromagnetic waves, of which the existence and features were theoretically described and predicted by James Maxwell, in 1864. First experimental proof of this theory was given by Heinrich Hertz in 1888, ten years after Maxwell’s death. It was already known at that time that electric current exists in oscillatory circuits made of a capacitor of capacity C and coil of inductance L. It was Thomson, back in 1853 that determined the frequency of this arrangement.
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor. The most common wireless technologies use radio. With radio waves distances can be short, such as a few meters for television or as far as thousands or even millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. Somewhat less common methods of achieving wireless communications include the use of other electromagnetic wireless technologies, such as light, magnetic, or electric fields or the use of sound.
Wireless operations permit services, such as long-range communications, that are impossible or impractical to implement with the use of wires. The term is commonly used in the telecommunications industry to refer to telecommunications systems (e.g. radio transmitters and receivers, remote controls etc.) which use some form of energy (e.g. radio waves, acoustic energy, etc.) to transfer information without the use of wires. Information is transferred in this manner over both short and long distances.
1.2Problem statement
Although they’ve been on the shelves of audio and video equipment retailers for quite a few years now, wireless receivers have been conspicuously absent. Building this sort of project, especially if a certain level of quality is needed, is highly technical. At the present time, various manufacturers offer a wide range of IC building blocks for receiver design, including RF amplifiers, mixers, synthesizers, and IF amplifiers/demodulators. However, completely integrated, high-performance receivers are essentially non-existent. One of the main challenges facing complete integration of receiver hardware has been a lack of suitable on-chip RF and IF filtering. Thus, a major portion of this dissertation is focused on the problem of realizing high performance, integrated band pass filters Audio Wireless Receiver system using RX FM AUDIO receiver and TX-FM audio transmitter module from ABACOM Technologies. An additional obstacle to full integration is frequency synthesis. Although many/complete” synthesizer IC offerings can be found, a closer examination reveals that the VCO and tuned circuits for the synthesizer are not included on-chip. This problem is also considered and is shown to be closely related to the realization of band pass filters. Issues surrounding receiver integration are addressed in this dissertation from both a system and a circuit’s perspective. The problem faced is ultimately a circuit’s problem, but the degree to which any given circuit approach is successful must be assessed in the larger context of the host receiver system and its intended function and environment. This introduces an additional dimension to the research a study of system requirements and an assessment of alternative receiver architectures. Indeed, a review of work on integrated receiver design over the past two decades shows that alternative architectures have been extensively applied.
