Oscillator Design and Computer Simulation (2nd Edition)
This second edition of the number one guide to oscillator design presents a comprehensive, unified approach to oscillator design that can be used with a wide range of active devices and resonator types. Resonator types covered include: LC, crystal, SAW, dielectric resonator, coaxial line, stripline and microstrip. This text covers modern CAD synthesis and analysis techniques and is valuable to experienced engineers as well as to those new to oscillator design. The books topics include: Analysis fundamentals, oscillator fundamentals, limiting and starting, biasing, noise, computer simulation and examples and case studies.
Inspec keywords: microwave oscillators
Other keywords: unified design approach; computer simulation; microwave oscillators; RF oscillators; oscillator design
Subjects: Microwave circuits and devices; Oscillators
 Book DOI: 10.1049/SBEW023E
 Chapter DOI: 10.1049/SBEW023E
 ISBN: 9781884932304
 eISBN: 9781613530863
 Format: PDF

Front Matter
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1 Analysis Fundamentals
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For this section, we assume that networks are linear and time invariant. Time invariant signifies that the network is constant with time. Linear signifies the output is a linear function of the input. Doubling the input driving function doubles the resultant output. The network may be uniquely defined by a set of linear equations relating port voltages and currents.

2 Oscillator Fundamentals
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Two methods of oscillator analysis and design are considered in this book. One method involves the openloop gain and phase response versus frequency. This Bode response and nonlinear effects discussed later predict many aspects of oscillator performance. A second method considers the oscillator as a oneport with a negative real impedance to which a resonator is attached. The loop method provides a more complete and intuitive analysis while the negative resistance method is more suitable for broad tuning oscillators operating above several hundred megahertz.

3 Limiting and Starting
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Thus far, oscillator design has been considered assuming linear operation of the active device. Many aspects of oscillator performance are predicted by these linear design considerations. In this chapter the nonlinear aspects of the design are considered. This allows prediction of most remaining oscillator performance parameters.

4 Noise
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The phase noise performance of oscillators has become increasingly important because communications channels have become closer spaced and more heavily loaded, data transmission systems often require low phase noise, military EW and CCC systems are more sophisticated, and higher frequencies are being used by a variety of systems. Broadband voltagecontrolled oscillators used in electronically tuned PLL applications, which are now common, are inherently noisy.

5 Biasing
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A complete and rigorous description of biasing techniques, including all temperature and leakage effects, for bipolar, JFET, dualgate FET, and hybrid devices, is beyond the scope of this chapter. Except in rare applications, such as calibrated outputlevel oscillators, the bias schemes given here provide a more than adequate degree of bias point definition and stability. An active bipolar bias network is given as the final bias example. Resorting to even this modest level of bias network complexity is seldom required.

6 Computer Techniques
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Historically, the analysis of oscillator circuits involved the selection of a particular topology and then finding symbolic equations for that topology. Once the symbolic equations were found, evaluating which circuit element values satisfied the oscillation criteria required little computational effort. Abundant technical literature exists with symbolic equations for various oscillator structures. This technique was appropriate in a day when numeric tools were the slide rule and paper and pencil. Unfortunately, each time the engineer wishes to investigate a new oscillator topology the symbolic equations must be found. The symbolic approach is efficient for designing oscillators of one type but oppresses exploration of alternative and therefore, perhaps, more optimum structures.

7 Circuits
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In the next four chapters, the oscillator fundamentals discussed previously are applied to the design of a number of specific oscillators. The schematics, analysis of the Bode responses, circuit peculiarities, and performance of these oscillators will be studied.

8 LC Oscillators
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Oscillators using resonators constructed from inductors and capacitors find wide application in electronic systems. LC oscillators are more stable than RC oscillators for both the long and the short term. As a consequence, LC oscillators are almost exclusively used for general oscillator applications above the lowerfrequency limit for which inductors are practical in size. Economic high quality capacitors are available for a wide range of values and seldom affect oscillator design as much as inductors. At low frequencies, the value of inductance required for reasonable reactance becomes large. Cores using magnetic materials help decrease the practical lowerfrequency limit.

9 Distributed Oscillators
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As the operating frequency is increased, oscillator phase noise performance degrades. Oscillators with improved phase noise require higher loaded Q. Higher loaded Q requires higher unloaded Q, and for LC oscillators, this means increased inductor physical size. There is an upper limit on inductor size before distributed selfcapacitance and stray capacitance to ground become a problem. A potential solution to this problem is to use distributed (transmission line) resonators which may be larger and therefore have higher unloaded Q than inductors.

10 SAW Oscillators
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HighQ oscillators up to 200 MHz are built using bulk quartz crystal resonators. For UHF and microwave frequencies, transmission line and cavity oscillators offer higher Q than LC designs, but they are larger. SAW resonators fill the need for small highloadedQ oscillators in the frequency range 200 to 1,200 MHz. Typical unloaded Qs are 6,000 to 12,000.

11 Quartz Crystal Oscillators
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Oscillators using quartz crystal resonators are the epitome of phase noise and stability performance. Marvelously high loaded Q oscillators of small size and low cost are easily designed and built using the quartz crystal. Crystal oscillators were invented in the 1920s[1]. By the 1930s, several designs had been published and patented. Crystal resonator and oscillator development was intense during and after World War 1I. During the 1950s, the art encompassed harmonic operation at VHF frequencies. Today, crystals are a common component of nearly all consumer, commercial, and defense systems.

12 Case Studies
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This chapter utilizes the principles presented earlier to study oscillators from the designer's perspective. For each case we begin with a specification, discuss the design qualitatively and then proceed with the actual design. Each case is an oscillator which satisfies a typical application requirement.

Back Matter
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