Phaselock techniques are often used to establish coherence. 2. A phaselocked loop can be used as a frequency demodulator, in which service it has superior. Phaselock Techniques, Third Edition is intended for practicingengineers, researchers, and graduate students. This criticallyacclaimed book has. Loading The author, Floyd M. Gardner an influential expert in the area of PLLs, has presented a good reference book that encompasses all.
|Published (Last):||8 September 2010|
|PDF File Size:||13.9 Mb|
|ePub File Size:||18.57 Mb|
|Price:||Free* [*Free Regsitration Required]|
Effects of Phase Noise. Without the inductance, the varactor can only pull the crystal to higher frequencies, where the crystal reactance is inductive.
Phaselock Techniques – Floyd M. Gardner [Book review] | GaussianWaves
Behavior of a modulation-tracking loop cannot be explained nearly so easily. Despite intuitive notions to the contrary, changing any or all of these conditions does not eliminate hangup. The first-order pdf 3. That is the jitter to be expected if one were to measure the phase difference between a clean signal and one corrupted by noise, under conditions of large signal-to-noise ratio.
Noise from any source falls off in the cutoff region, assuring a finite noise-variance contribution from high frequencies. You are currently using the site but have requested a page in the site. For any x less than 2, the integral diverges at high frequencies. Tracking performance is discussed in Chapter 4 and methods of bringing the loop into lock are found in Chapter 5.
The ma- terial that follows deals with practical as- pects of component circuits and with ra- tional procedures for deciding upon phaselocic loop parameters. Phase deg hardner 2M Bode plot of a second-order loop with lag-lead filter.
Twchniques with respect to noise proves to be more subtle. Chapter 6 contains some examples of ripple-reduction tech- niques. Oscillator Phase Noise Oscillator noise — also called short-term instability or phase jitter — is an extensive topic.
Moreover, smaller damping reduces the allowable rate.
When the signal returns, reacquisition by lock-in or pull-in should be very rapid. Thus the filtered output of the quadrature detector provides a useful indication of lock.
This book has been written with the tacit assimiption that an active filter is the norm and that a passive filter is an inferior substitute that one accepts — along with degradation of performance — only for com- pelling reasons.
We let one input to the multipUer consist of a sinusoidal signal plus stationary, gaussian, bandpass noise: As might well be imagined, presence of a phase error increases the propensity to cycle slipping. The ratio of signal power to this value of noise power is our definition 3. Fokker-Planck equations can be written for the true second-order loop, but explicit, exact solutions have been unattainable. A block diagram and pertinent equations are shown in Figure S.
Pull-in Pull-in, particularly in a loop with very narrow bandwidth, is fascinating to watch.
Discrlminator-Alded Frequency AcquisHlon If the input signal-to-noise ratio is large enough, a frequency discrimina- tor can be used in a conventional automatic frequency control loop to bring the VCO frequency close to that of the signal. Richman” has compared filter switching and gain switching and has- phasellock some useful approaches. A phaselocked loop can be used as a frequency demodulator, in which service it has superior performance to a conventional discriminator.
The tuning range of this circuit is very small when high-g crystals are used. However, slew limiting is not symmetri- cal; there is, in effect, some rectification of the beat-note. As an engineering tool, we invoke the concept of crest factor and give it the symbol y.
If the PD output is almost undistorted, then the peak phase error must increase as the inverse sine of the deviation, to a good approximation. The plot starts zero gain on the open-loop poles and terminates infinite gain on the open-loop zeros some gardnr which may be located at infinity. My library Help Advanced Book Search.
We can draw two significant conclusions: Noise bandwidth of the popular high-gain, second-order loop is phasrlock against damping in Figure 3. One of their most important applications is in the reception of the very weak signals from distant spacecraft.
Moreover, the cycIe-sUp predictions are for ideal loops, so no relief can be obtained from improvements in loop compo- nents.
Phaselock Techniques, 3rd Edition
The benefit obtainable from a lead term may be seen in Figure 2. Approximate formulas for piill-in time and for pull-in Umits may be obtained by follovnng a method originated by Richman. Chapter Four Tracking 4. Garrdner, phase of the local oscillator must agree, within a fairly small fraction of a cycle, with the received carrier phase. Moreover, the large integrator gain can be obtained simultaneously with small noise bandwidth, an impossible combi- nation in a first-order phwselock.
The transfer function H s has a well-defined 3-dB bandwidth, which we label wjdg.
There is little pretense involved for high-enough beat frequencies. Insertion of a simple lag filter 2.
Another form of frequency aid is provided by the popular sequential phase-frequency detector described in Chapter 6. These transfer functions may be rewritten as 2.
Phaselodk information is stored in the form garrdner charge in the integrator. Since we have defined spectral density only for stationary processes Appendix vonage-uoniroiiea usciiiaiors Athe phase spectrum of flat frequency noise is not phaselpck properly. Space use of phaselock began with the launching of the first American artificial satellites. Phase detectors are frequently modeled as multipUers, partly for analytical convenience and partly because many practical phase detectors are good approximations to multipliers; see Chapter 6.
Reduction of distortion is a familiar property of feedback loops in general fiiat is shared by the PLL in particular. Accordingly, it is sometimes used in special apphcations. This relation is used later in establishing a definition for signal-to-noise ratio of the phaselock loop. The upper operating frequency of practical relaxation oscillators has been limited to a few tens of megahertz.