Depending on the type of application the phase detectors are chosen in the digital pll. The 14bit reference counter r counter allows selectable refin frequencies at the pfd input. Simulation of a software phaselocked loop for typical. A complete phaselocked loop pll can be implemented if the synthesizer oscillator vco. Frequently asked questions about phase detectors an41001. The basic phase detector method is shown in figure 16. A tutorial approach to analog phase by angsuman roy yg locked. This example generates a frequencysweep test signal, mixes in some. There are a number of different types of phase detectors pd.
Traditionally, a phase detector is created by taking a product of the input cosine wave with a. There is a software pll with a hardware phase detector. This is because a digital phase detector has a nearly infinite pullin range in comparison to an xor detector. A pll consists of a phase detector, a lowpass filter, a variable frequency oscillator, and a divider figure 1. Clock and data recoverystructures and types of cdrsthe cdr. Simple and efficient algorithm to detect frequency and. Keywords digital pll, frequency detection, orthogonality, phaselocked loop, synchronization. Modeling and simulating an alldigital phase locked loop. A tutorial approach to analog phase by angsuman roy yg.
This phase detector counts the number of highfrequency clock periods. Mayaram a new frequency detector, which allows for a fast frequency lock of phase locked loops plls, is presented. How does a vlf metal detector distinguish between different metals. I need an algorithm to detect frequency and phase of a pure sine signal. You can just have a timer, capture the times of the reference and feedback edges, and figure out the phase frequency in software. A novel threephase software phaselocked university of. Moreover, it helps filter out noise and irrelevant frequency components generated in the phase error detector. A novel phase frequency detector for a high frequency pll. Design of an efficient phase frequency detector for a.
A pll locked to a stable reference can generate a stable high frequency oscillator. Since the vcovcm produces a frequency proportional to its input voltage, any time variant signal appearing on the control signal will frequency modulate the vcovcm. Software phase locked loop design using c2000 microcontrollers for single phase grid connected inverter comparing the closed loop phase transfer function to a generic second order system transfer function, which is given as. A phase detector or phase comparator is a frequency mixer, analog multiplier or logic circuit that generates a voltage. The phase detector produces a voltage proportional to the phase difference between the signals. A classic or linear pll uses a mixer as a phase detector. Phasefrequency detector pfd includes a highspeed edgetriggered detector with internal charge pump independent vco, pfd powerdown mode thin smalloutline package 14 terminal compatible pin assignment to tlc2932, tlc2933 description the tlc2934, a mixed signal ic designed for phaselockedloop pll systems, is composed of a. Frequency detector for fast frequency lock of digital plls v. As will be described in section ii, the speed of the conventional. It uses the feedback divider that already exists in a pll to determine the frequency difference. You will see later that the loop filter bandwidth has an effect on the capture range. The frequency of the input signal changes between 0 and 100 hz. Mch12140, mck12140 phasefrequency detector description the mchk12140 is a phase frequency.
The goal of the phase detector is to create a signal that is proportional to how far the pll needs to be made faster or slowed down. Practically phase detector are not sensitive to frequency if compare incoming signals from same source. We will discuss the details of phase detectors and loop filters as we. The difference between digital phase and frequency detector. That phase frequency detector is a hybrid of two designs, one of which has good phase synchronizing properties the xor type and the other of which has good frequency synchronizing properties the counter type. As line notching, voltage unbalance, line dips, phase loss and frequency variations are common conditions faced by equipment interfacing with electric utility, the. Figure 1 classical active loop filter topology for a voltage phase detector the modern phase frequency detector with charge pump and its advantages the phase frequency detector with charge pump combination offers several advantages over the voltage charge pump and has all but replaced it. The nominal lock point with an xor phase detector is also at the 90 static phase shift point. I am simulating a software pll intended to lock to mains, which here is 50hz. Used to synchronize the phase of two signals, the phase locked loop pll is employed in a wide array of electronics, including microprocessors and communications devices such as radios, televisions, and mobile phones. Phase detector difference of input and feedback clock phase often built from phase frequency detector pfd 22. Slope detection gives inferior distortion and noise rejection compared to the following dedicated fm detectors that are normally used.
This is a nonlinear device whose output contains the phase difference between the two oscillating input signals. Plls and dlls cmos vlsi designcmos vlsi design 4th ed. This block is most appropriate when the input is a narrowband signal. Fast frequency acquisition phasefrequency detectors for.
The function of the loop filter is to convert the output signal of phase frequency detector to control voltage and also to filter out any high frequency noise introduced by the pfd. The sampling phase detector spd module is a hybrid circuit providing a fast step recovery diode, coupling capacitors and a low barrier schottky pair. Api technologies line of phase frequency detectors perform frequency measurement of an rf pulse and output data in as little as 15 ns. Phase and frequency analyze plls and dlls in term of phase. A phase detector or phase comparator is a frequency mixer, analog multiplier or logic circuit that generates a voltage signal which represents the difference in phase between two signal inputs. The two frequencies cause the phase difference to be a beat behavior. Since the vcovcm produces a frequency proportional to its input voltage, any time variant signal. 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. The ability to integrate our own high performance broadband channelizers, high q filters and low loss detectors allows them to provide stable outputs over temperature, a more. As name told us phase detectors are sensitive to the phase difference between two signals on input similary frequency detectors are sensitive to the frequency difference on its input. Phase detectors when looking at a signal affected by low level noise or spurious modulation with a spectrum analyzer, it is difficult and sometimes impossible to determine unequivocally if the observed sidebands are caused by amplitude modulation am or phase or frequency modulation pm or fm. They are physically similar, but each type of product is specified on its data sheets in accordance with its principal application. Henry young, alex tong, ahmed allam implementation of phasefrequency detector.
Adf4002 frequency synthesizer is used to implement local oscillators in the upconversion and downconversion sections of wireless receivers and transmitters. Note that the frequency is relative to an unspecified sample rate, so the maximum is \\pi\ and the minimum is \\pi\. The mch12140 or k12140 is a phase frequency detector intended for phase locked loop applications which require a minimum amount of phase and frequency difference at lock. Phase detectorfrequency synthesizer data sheet adf4002. Advanced design significantly reduces the dead zone of the detector. The value of the signal gets captured with a frequency of 20 khz so i get 20000 values per second this is given and cannot be changed.
Phase frequency detector pfd figure 2 shows a popular implementation of a phase frequency detector pfd, basically consisting of two dtype flip flops. Phase shift is the difference in timing between the transmitter coils frequency and the frequency of the target object. This voltage upon filtering is used as the control signal for the vcovcm vcm. The phase detector, filter, and vcovcm compose the feed forward path with the feedback path containing the programmable divider. Among minicircuits products, what is the difference between a phase detector and a doublebalanced mixer dbm.
In this section we will evaluate a typical software pll with medium. Study and implementation of phase frequency detector and. Phase shift provides vlfbased metal detectors with a capability called discrimination. Implement phaselocked loop to recover phase of input. The output of the vco, f osc, is fed back to the phase frequency detector input for comparison which in turn controls the vco oscillating frequency to minimize the phase difference. Frequency detector for fast frequency lock of digital plls d. The 567 tone decoder is perhaps most famous phase locked loop pll chip. The problem is, as usual, in selecting a good phase detector. A phase detector is a nonlinear device whose output represents the phase difference between the two oscillating input signals. Fast frequency acquisition phasefrequency detectors for gsampless phaselocked loops mozhgan mansuri, dean liu, and chihkong ken yang abstract this paper describes two techniques for designing phasefrequency detectors pfds with higher operating frequencies periods of less than 8 the delay of a fanout4 inverter. Mt086 phase frequency detector pfd figure 2 shows a popular implementation of a phase frequency detector pfd, basically consisting of two dtype flip flops.
The phase detector is based around two d type flip flops and an nand gate, although there are a number of slightly different variants. This type of phase frequency detector is widely used in many circuits because of its performance and ease of design and use. Our study is focused on designing phase frequency detector design. This yields a dc component that is proportional but not linear with the phase difference and a component at a frequency that is twice the input frequency.
The mc100ep40 is a threestate phase frequency detector intended for phase locked loop applications which require a minimum amount of phase and frequency difference at lock. Mathworks is the leading developer of mathematical computing software for engineers. This phase detector includes a filter function defined by the impulse function of the averaging circuitry. A phase frequency detector pfd is an asynchronous circuit originally made of four flipflops i. This phase detector counts the number of high frequency clock periods. Because of this, its common to sweep the plls frequency all over the range where you expect to find a signal until you get a lock, and then stop sweeping. You can replicate a three state phase frequency detector of the sort that you find in many synthesizer chips and pll chips like the cd4046. Extended linear phase detector characteristic of a software pll. Phasefrequency detector that compares phase and frequency. For the clock and data recovery, xor gate is used as the phase detector. Therefore, both frequency and phase are made the same, i. The ability to integrate our own high performance broadband channelizers, high q filters and low loss detectors allows them to provide stable outputs over temperature, a more tolerable rf match for the filter and improved signal to noise ratio. Error detector composed of a phase frequency detector.
Most of the phase detectors have advantage that their low frequency response. These useful building blocks are implemented when designing phase locked loop synthesizers for microwave radios for point to point, military, satellite and sonet applications. Clock and data recoverystructures and types of cdrsthe cdr phase and frequency detector pfd. With analog devices acquisition of hittite microwave corporation came several new phase frequency detector products. A phase locked loop or phase lock loop pll is a control system that generates an output signal whose phase is related to the phase of an input signal. Simple and efficient algorithm to detect frequency and phase. The schottky pair is used as a sampling circuit turned on by the fast step from the step recovery diode, or in the frequency domain, the schottkys act as a mixer to mix the harmonic of the srd. Phase locked loop pll in a software defined radio sdr. Hardware and software powerdown mode 104 mhz phase detector applications clock conditioning clock generation if lo generation general description the adf4002 frequency synthesizer is used to implement local oscillators in the upconversion and downconversion sections of wireless receivers and transmitters. Multirate clock and data recovery circuit with a multi. A phase detector output pulse is generated in proportion to that phase difference. Tlc2932 pll building block w analog voltagecontrolled. Phase frequency detector that compares phase and frequency between two signals. The golfed version above is reduced from a much more readable example of a software phase locked loop in c that i wrote today, which does do lock detection but does not sweep.
If the frequency of input a is less than that at input b, the. Specifically designed to help synthesizer designers select the best hittite divider, phase frequency detector and vco for their pll circuit. Unlike an analogue mixer phase detector, the xor version is independent of input amplitude and constant over a. Do you have an example or link to a good reference for a software based product detector. Another form of detector is said to be phasefrequency sensitive. Lecture 080 all digital phase lock loops adpll reference 2 outline. Stable oscillator topologies donstable oscillator topologies dont scale well to high t scale well to high frequencies. A chargepump pll with digital phasefrequency detector in simulink. The program initially sets the parameters for the simulation, including the carrier phase and frequency offsets, the phaselocked loop filter specifications, and the number of samples to run. The branch voltage of the loop filter is used as input to the vco. For proper operation, the input edge rate of the r and v inputs should be less than 5 ns. It consists of a low noise digital phase frequency detector pfd, a precision charge pump, a programmable reference divider, and programmable n divider. A digital phase frequency detector pfd determines whether a positive or negative current is pumped into the filter. A phase frequency detector compares the phase of the vco output frequency, fosc, with the phase of a reference signal frequency, fref.
Generating a highfrequency clock increases the difficulty of the design of the pfds, particularly for systems with a high input clock frequency and minimum frequency multiplication. The phasefrequency detector pfd the pfd can detect both the phase and frequency difference between v 1 and v 2. Adapters amplifiers attenuators bias tees cables couplers dc blocks equalizers filters frequency mixers frequency multipliers impedance matching pads limiters modulatorsdemodulators oscillators phase detectors phase shifters power detectors power splitterscombiners 90180 hybrids rf chokes switches synthesizers terminations transformers. Software pll design using c2000 mcus single phase grid. This pulse is smoothed by passing it through a loop filter.
A pll on the other hand is the simplest computer that actually runs so much of the world as a fundamental component of intelligent electronic circuits. What could be the best use for the phase and the frequency information in the pll. It uses the feedback divider that already exists in a pll to determine the frequency. It is an essential element of the phaselocked loop pll. The block diagram of a phasefrequency detector pfd is shown in fig. When used in conjunction with high performance vco such as the mc100el1648, a high bandwidth pll can be realized.
A loop filter is used to get rid of the second component. 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. The phase locked loop pll block is a feedback control system that automatically adjusts the phase of a locally generated signal to match the phase of an input signal. Phase lead corresponds to a negative frequency output and thus vco frequency decreases whereas phase lag corresponds to a positive current. Since most metals vary in both inductance and resistance, a vlf metal detector examines the amount of phase shift, using a pair of electronic circuits called phase demodulators, and compares it with the average for a particular type of metal. Lowpower lowjitter onchip clock generation a dissertation submitted in partial satisfaction of the requirements for the degree doctor of philosophy in electrical engineering by mozhgan mansuri 2003.
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