Digital Frequency Synthesis DemysTIfied:

This text deals with emerging modern digital techniques used to

generate and modulate sine wav e s. These waveforms are used in

almost all radio applicaTIons, communicaTIons, radar, digital comm

u n i c a t i o n s, electronic imaging, and more. Such tech n i q u e s

either build the waveform from the “ground up” digitally (i.e., generate

all the signal parameters such as phase, frequency, and

amplitude digitally) and deal with the very fundamental nature of

the waveform and its features (direct digital synthesis) or are part

of the digital heart of modern p h a s e - l o cked loop (P L L) synthesize

r s. This might seem, and is indeed, a common and known subject.

Sine waves are truly natural waveforms and trigonometric funcTIons

that are well known and have been researched for a long

t i m e. Furthermore, frequency synthesis is quite a mature technology

with extensive literature and comprehensive coverage in

the professional meetings. Why another text on the subject? What

is new besides application-specific integrated circuit (A S I C) technologies

and silicon densities, geometry, and integration?

While the above statements are true, there is a continuous evolution

in the tech n o l o g y. The generation of accurate wav e f o r m s

p l ays a crucial role in almost all electronic equipment, from radar

to home entertainment equipment, so the importance of the subject

is cl e a r. Clearly, the most important reason for the utilization

of the now extremely popular PLL synthesizers in consumer elec-

tronics and other very popular applications at extremely low cost

(and the popularization of frequency synthesis from consumer

products all the way to complex requirements) is the advance of

digital technology; integrated, high densities; and low-cost silicon

single-PLL chips and ASICs. However, parallel to the advance of

traditional PLL synthesis, there emerged other synthesis techn

iques, mainly digital in nature, direct digital synthesis (D D S)

and fractional-N PLL synthesis. Thus, the classical PLL synthesizer

is now being supplemented with a sizable element of digital

technology and digital signal processing (DSP). Indeed the application

of DSP techniques to frequency synthesis is still at an early

stage.