O'Reilly logo

RF and Microwave Wireless Systems by Kai Chang

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

CHAPTER SIX

Transmitter and Oscillator Systems

6.1   TRANSMITTER PARAMETERS

A transmitter is an important subsystem in a wireless system. In any active wireless system, a signal will be generated and transmitted through an antenna. The signal’s generating system is called a transmitter. The specifications for a transmitter depend on the applications. For long-distance transmission, high power and low noise are important. For space or battery operating systems, high efficiency is essential. For communication systems, low noise and good stability are required. A transmitter can be combined with a receiver to form a transceiver. In this case, a duplexer is used to separate the transmitting and receiving signals. The duplexer could be a switch, a circulator, or a diplexer, as described in Chapter 4.

A transmitter generally consists of an oscillator, a modulator, an upconverter, filters, and power amplifiers. A simple transmitter could have only an oscillator, and a complicated one would include a phase-locked oscillator or synthesizer and the above components. Figure 6.1 shows a typical transmitter block diagram. The information will modulate the oscillator through AM, FM, phase modulation (PM), or digital modulation. The output signal could be unconverted to a higher frequency. The power amplifiers are used to increase the output power before it is transmitted by an antenna. To have a low phase noise, the oscillator or local oscillator can be phase locked to a low-frequency crystal ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required