The slope of the characteristic in either case is kd. L lock range where kv ko kd, the product of the phase detector and vco gains. The xor detector compares well to the analog mixer in that it locks near a 90 phase difference and has a. Osa design of a delayed xor phase detector for an optical.
Detector phase detector reft divt ref2t div2t t t1 1 et xor based pfd tristate pfd figure 3. Exclusive or xor gate based phase detector db6sw kf5obs. Sep 02, 2012 an xor gate based phase detector interprets phase differences greater than 180 as actual phase difference minus 180. Modeling of xor phase detector universitas hasanuddin. To take care of these disadvantages, we implemented the phase frequency detector, which can detect a difference in phase and frequency between the reference and feedback signals. A trilevel resistor dac is also introduced as complementary to the new quantizer, enabling high dr while creating a dynamic power saving mechanism for the proposed design. Digital phase locked loop devon fernandez and sanjeev manandhar december 8, 2003 1. Depending on the phase detector you are using, you will need to add some o. The exclusive or, xor phase detector circuit can provide a very useful simple phase detector for some applications. When the phase detector output voltage is applied through the loop filter to the vco, out max kv. Pdf in this paper the implementation of xor phase detector in 45 nm submicron cmos technology and itscmos design layout using microwind 3. Still in progress to get proper input for arduino, code still the same as last code posted. What are the differences between xor and edge controlled.
The only digital block is the phase detector and the remaining blocks are similar to the. The phase detector measures di erences in phase between the input and the divided output. Theoretically, any mixer with a dc coupled port could be used as a phase detector. Loop filter averages out phase detector output severe cycle slipping causes phase detector to alternate between regions very quicklyaverage value of xor characteristic can be close to zeropll frequency oscillates according to cycle slipping in severe cases, pll will not relock pll has finite frequency lockin range. Then, a 50 ps delay line and relative signaltonoise ratio control at 15 db are produced through theoretical derivation and simulation.
Frequently asked questions about phase detectors an41001. The xor phase detector is simply exclusive or gate. Alexander phase detector characteristic with noise total transfer characteristic is the convolution of the ideal pd transfer characteristic and the noise pdf noise linearizes the phase detector over a phase region corresponding to the peaktopeak jitter 14 lee td j k pp pd 2 td is the transition density. Pdf design, implementation and characterization of xor phase. Furthermore, an xor phase detectors response can have a larger linear range than a sinusoidal detector mixer. The output characteristic of the xor phase detector show repetitions and gain changes. In pll applications, the vco is treated as a linear, timeinvariant system. Average value of pulses is extracted by loop filter. Fractionalinteger n pll basics 7 a phase detector is a digital circuit that generates high levels of transient noise at its frequency of operation, fr. Doesnt depend on the loop filter does depend on dc loop. The exclusive or, xor phase detector circuit can produce a highly functional simple phase detector for some applications.
Unlike an analogue mixer phase detector, the xor version is independent of input amplitude and constant over a. The basic phase detector method is shown in figure 16. This is because an xor gate based phase detector doesnt know which of the two signal was first and which signal is preceding which. Thus, a series of studies is conducted to address this issue. Arduino forum using arduino programming questions phase detector by using bitwise. A versatile building block for micropower digital and analog applications phase comparator i is an exclusiveor network that operates analogously to an overdriven balanced mixer. You should be able to answer this question theoretically and experimentally. This noise is superimposed on the control voltage to the vco and modulates the vco rf output accordingly.
Design of an efficient phase frequency detector for a digital. A phase frequency detector pfd is an asynchronous circuit originally made of four flipflops i. At 90 the xor has a 50% duty cycle squarewave output at twice the frequency of the input. An xor gate based phase detector interprets phase differences greater than 180 as actual phase difference minus 180. This is the frequency range around the free running frequency that the loop can track. To maximize the lock range, the signal and comparatorinput frequencies must have 50% duty cycle.
A tutorial approach to analog phase by angsuman roy yg locked. Monolithically integrated heterodyne optical phase lock loop with rf xor phase detector. Led to a simple pd model large perturbations knock us out of that confined phase rangepd behavior varies depending on the phase range it happens to be in. Practically, however, mixers often display some very nonideal characteristics e. The ad9901 is a digital phasefrequency discriminator capable of directly. Study and implementation of phase frequency detector and. We will discuss the details of phase detectors and loop filters as we proceed. The operations of the exclusive or phase detector is illustrated in figure 6 below. The characteristic of the phase detector is as shown below. Pdf monolithically integrated heterodyne optical phase. Figure 5 illustrates the schematic of an exclusive or phase detector. Analog devices phase frequency detectors offer high performance and ultralow phase noise in a low cost, compact package.
You will see later that the loop filter bandwidth has an effect on the capture range. But, at this point, we will treat the pll as a linear feedback system. One advantage of such a phase detector is that the loop gain is now independent of input signal amplitude. If you are using a type 2 pll, create a schematic with your phase detector.
Recall phase detector characteristic to simplify modeling, we assumed that we always operated in a confined phase range 0 to. A phase detector or phase comparator is a frequency mixer, analog multiplier or logic circuit. Monolithic phaselocked loops for clocking subsystems. The gain of the phase detector is the ratio between vpd and when the phase difference is larger than. When an xor gate phase detector is used in a phase locked loop pll system it generally locks near a 90 phase difference in the middle of the phase detection range. A tutorial approach to analog phase by angsuman roy yg. Among minicircuits products, what is the difference between a phase detector and a doublebalanced mixer dbm. Two sources, at the same frequency and in phase quadrature, are presented to a doublebalanced mixer which, together with a lowpass filter, acts as a phase detector. Monolithically integrated heterodyne optical phase lock loop with rf xor phase detector article pdf available in optics express 1921. Monolithically integrated heterodyne optical phaselock loop with rf xor phase detector article pdf available in optics express 1921. Mixers as phase detectors most systems which require phase information use mixers somewhere in the measurement or comparison of the phase information.
Depending on the type of application the phase detectors are chosen in the digital pll. Vco for pll frequency synthesizer ammattikorkeakoulut. I trying to read power factor that compare the signal input from voltage and current by using bitwise xor. They are physically similar, but each type of product is specified on its data sheets in accordance with its principal application.
Xor phase detector will try tolock on both rising as well as falling edge while the pfd phase frequency detector will lock on eitherrising edge or falling edge of reference signal and feedback. It will be assumed in our modeling effort that the charge pump scales the pfd output by the value icp before the signal is fed into the loop filter. First, a delayed exclusive or gate xor phase detector with multilevel loop compound control is proposed. Phaselocked loops plls with the proposed hybrid phase detector possess the intrinsic advantage of the low timing jitter of plls with a two xor phase detector in lock states and the fast locking process of plls with an improved bangbang phase. Digital pll mixer replaced with xor gate or phase frequency detector pfd. I had pick phase detector diagram, and i just make like it. Figure 5 exclusive or phase detector, modified from ian poole 2. Our devices can significantly improve frequency lock time, and include automatic and configurable lock detect indicators. Phase frequency detector pfd topologies considered here. As shown in the schematic of the pfd dpll in figure 10 and mentioned in the earlier section, this dpll has four parts and they are as follows. This is because a digital phase detector has a nearly infinite pullin range in comparison to an xor detector.
The nominal lock point with an xor phase detector is also at the 90 static phase shift point. Plls and dlls cmos vlsi designcmos vlsi design 4th ed. We will first analyze a pll with a simple phase detector pd first. Phase detector difference of input and feedback clock phase often built from phase frequency detector pfd 22. Phase detector detects phase difference between feedback clock and reference clock the loop filter will filter the phase detector output, thus to characterize phase detector gain, extract average output voltage the k pd factor can change depending on the specific phase detector circuit 4 when used with a impedance filter. For a variety of reasons, it may be desirable to have a loop which does not produce a sinusoidal clock but instead a square wave clock.
Pdf monolithically integrated heterodyne optical phaselock. For the clock and data recovery, xor gate is used as the phase detector. For instance, a phase difference of 270 will be interpreted as 90. What are the differences between xor and edge controlled phase detectors.
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