INTRODUCTION
A vacuum-tube or solid-state radio transmitter is essentially a source of a radio-frequency (RF) signal to be transmitted through antenna in different radio systems such as wireless communication, television (TV) and broadcasting, navigation, radar, or satellite, the information format and electrical performance of which should satisfy the corresponding standard requirements. The transmission of radio signals is produced by modulation of different types, with different output power and transmission mode, and in different frequency ranges, from high frequencies to millimeter waves. Transmitters in which the power output is generated directly by the modulated source are considered as possessing high-level modulation systems. In contrast, arrangements in which the modulation takes place at a power level less than the transmitter output are referred to as low-level modulation systems.
Figure I.1 shows the simplified block diagram of a conventional radio transmitter intended to operate at radio and microwave frequencies, which consists of the following: the source of the information signal, which is usually amplified, filtered, or transformed to the intermediate frequency; the local oscillator and frequency multiplier, which establish the stabilized carrier frequency or some multiple of it; the RF modulator or mixer, which combines the signal and carrier frequency components to produce one of the varieties of the RF modulated waves; the power amplifier to deliver the RF ...
