TABLE OF CONTENTS Frequency hopping is the periodic changing of the carrier frequency of a transmitted signal. The sequence of carrier frequencies is called the frequency-hopping pattern. The set of M possible carrier frequencies { f 1, f 2, , f M} is called the hopset. The rate at which the carrier frequency changes is called the hop rate. Hopping occurs over a frequency band called the hopping band that includes M frequency channels. Each frequency channel is defined as a spectral region that includes a single carrier frequency of the hopset as its center frequency and has a bandwidth B large enough to include most of the power in a signal pulse with a specific carrier frequency. Figure 3.1 illustrates the frequency channels associated with a particular frequency-hopping pattern. The time interval between hops is called the hop interval. Its duration is called the hop duration and is denoted by T h. The hopping band has bandwidth W ? MB.
Figure 3.2 depicts the general form of a frequency-hopping system. The frequency synthesizers (Section 3.4) produce frequency-hopping patterns determined by the time-varying multilevel sequence specified by the output bits of the code generators. In the transmitter, the data-modulated signal is mixed with the synthesizer output pattern to produce the frequency-hopping signal. If the data modulation is some form of angle modulation ?(t), then the received signal...
