I couldnt figure out how you thought you had a 90 phase shift between the two signals. Introduction phase shifters have wide spread applications, in particular, 90 phase shifters are used in wireless communication for single side band generation, iq modulation and image rejection. Simultaneously, more systems are designed where both i and q signals are being directly converted to digital signals, and then a quadrature phase shift is applied. Clock and data recovery for serial digital communication plus a tutorial on bangbang phase lockedloops rick walker hewlettpackard company palo alto, california. Oscillators university of california, santa barbara. So i wanna know how to implement the same on fpga, i. Vhdl 4 bit shifter rotator structural design using components. They are used in a variety of applications, including rf pa linearizationrf distortion, amplitude and phase modulation, variable attenuators, and fiber optics. The entity declaration defines the circuits external interface and the architecture defines its internal implementation. Applications include controlling the relative phase of each element in a phase array antenna in a radar or steerable communications link and in cancelation loops used in high linearity amplifiers.
The input test signals data and carrier are interfaced to the cpld and fpgas board from agilent function generator e8408a. Simple barrel shifter figure below shows the barrel shifter. Direct digital synthesis dds sine wave generation, phase accumulator cordic algorithm digital filters linear timeinvariant finite impulse response fir, distributed. Fpga based sinecosine encoder to digital converter using deltasigma technology dipl.
Phase shifter fundamentals phase shifters are a critical component in many rf and microwave systems. It is implemented using 27tap symmetric finite impulse response fir filter. This is due to the fact that you cant know what state the flops will be in when powered up unless there is a reset circuit. Consequently the output is solely a function of the current inputs. Later, we will study circuits having a stored internal state, i.
Digital implementation of phase locked loop on fpga. Fpga implementation of pi2 bpsk and pi4 qpsk for ieee. There will be a slight phase shift that will move the total phase around the loop off the peak of the resonator. The textbook covers the constructs of the vhdl programming language with a large number of implementable examples.
Here the dds uses lookup table to generate the sinusoids. It presents the basic concepts in organized and progressive phases. Phased array antenna processing on reconfigurable hardware. This phase term is composed of the accumulation, at a sample period of ts, of two frequency terms, f c and f m, and a phase term, o m the additions involved in its computation are signed modulo. Merrimac offers an extensive line of manual, elec tronic, digital and precision phase shifters for both. Xilinx xapp462 using digital clock managers dcms in spartan. There are many modulation techniques, which are classified according to the type of modulation employed. The effect is minimized by making c2 large and re large. A pll is a feedback control system that automatically adjusts the phase of a locally generated signal to match the phase of an input signal. An introduction to vhdl overview dinesh sharma microelectronics group, ee department iit bombay, mumbai august 2008 dinesh sharma vhdl. In this case, the circuit shifts the input vector either 0 or 1 position to the left. The digital control interface allows to control the phasegain.
In a block diagram or abridged schematic, we often show. Vhdl includes facilities for describing logical structure and function of digital systems at a number of levels of abstraction, from system level down to the gate level. Analog phase shifters provide a continuously variable phase, most often controlled by a voltage. The design and manufacture of high performance, broadband phase shifters, frequency translators and iq modulators have made general microwave the undisputed leader for these devices. I wanna produce a constant phase shift of 120 degree at ghz. It is intended, among other things, as a modeling langua ge for specification and simulation. I think of simple digital phase modulation as discrete changes in phase. Objectives to design a binary phase shift keying modulator bpsk by using vhdl and its implementation in a fpga. Method modulator design all analogue or hybrid analogue digital qpsk modulators work with phase shift carrier angle. The phase shift unit shifts the phase of all nine dcm clock output signals by a fixed fraction of the input clock period.
Coordinate rotation digital computer cordic is an efficient and versatile algorithm that can implement a phase shift without using multipliers. Vhdl provides standard shift functions, which should be used, instead of the home build that even looks wrong. So based on this the code with process can be updated to. Is there any possible ic for it probably the answer is no i am not sure. Xilinx xapp462 using digital clock managers dcms in spartan3. Shift register are the registers which are used to shift the stored bit in one or both directions. The phase shift unit also provides a digital interface for the fpga application to dynamically. Ashenden vhdl examples 1 vhdl examples for synthesis by dr.
I could phase shift a clock by 90 degrees and then xor the original clock and the 90 degree phase shifted clock, to get effectively 2x my original clock. One thing to note on the digital phase splitter, the two flops must be resettable or you cant guarantee what phase relationship will be between the two outputs. Improvement of rf vector modulator performance by feed. In previous chapters, some simple designs were introduces e. The purpose of this tutorial is to describe the modeling language vhdl. Vhdl tutorial for beginners this tutorial is intended for beginners who wish to learn vhdl. Digital in the case of phase shifters means twostate devices, where the states have different insertion phases at microwave frequencies. Digital iq modulation phase shift keying constellations lecture 9 analog and digital iq modulation.
The dds digital architecture eliminates the need for the manual system. How to measure phase difference of two signals of the same. So, what is the future of quadrature phase generation. Vhdl programming code is used to generate qpsk digital signal. A 32bit barrel shifter, then, has thirtytwo 32input multiplexors. Phase shifting a clock by 90 degrees without using any. Oh yeah, i dont understand why the else conditions are not valid. Representing the filter coefficients by csd eliminates the need for multipliers and the filter is implemented using shifters and adderssubtractors. Design examples fpga designs with vhdl documentation. Direct digital synthesis dds is a technique for using digital data processing blocks as a means to generate a frequency and phase tunable output signal referenced to a fixedfrequency precision clock source.
Your else conditions are not really valid vhdl because its outside the event area, but since you only assigned the signal to itself the synthesizer would ignore. Note that vhdl shift infix operators before vhdl 2008 are known to give unexpected results, so use the functions instead. Abstract the report is based on the digital implementation of phase locked loop on fpga, the report covers the steps taken for implementing the proposed phase locked loop architecture on the fpga. Apr 07, 2019 for instance, 32bit nco with a 12bit phase word results in phase truncation spurs of no more than 72dbc regardless of the tuning word chosen. Schottky diodes are also used as variable elements in analog phase shifters, but. Uses a feedback shift register to randomize data reversing process at receiver restores original data. In the last section a tutorial is introduced where the reader can learn how to. The multiplexer is used to transmit the corresponding phase shifted carrier signal depending upon the data. The fixed phase shift value is set at design time and loaded into the dcm during fpga configuration. Product specification introduction the xilinx logicore ip direct digital synthesizer dds compiler core implements high performance, optimized phase generation and phase to sinusoid circuits with axi4stream compliant interfaces. Vhdl programming for sequential circuits this chapter explains how to do vhdl programming for sequential circuits.
Designing digital circuits using vhdl 8 its important to understand the distinction between the entity declaration and the architecture. Field programmable gate array fpga for digital pro cessing. Like any hardware description language, it is used for many purposes. Xilinx xapp462 using digital clock managers dcms in. The control function is the relationship be tween the voltage or digital control value rela tive to the phase shift produced. Analog devices digital phase shifters change the phase of rf, microwave, or millimeter wave signals while providing no amplitude change. In essence, the reference clock frequency is divided down in a dds. To achieve the abovementioned integration between vhdl and digital design, the following steps are taken. You will understand here, what is qpsk, why it is called as qpsk, how the qpsk is different from other digital. A barrel shifter is more easily implemented as a mux whose select is the number of positions you wish to shift. Digital electronics part i combinational and sequential logic. Phase or frequency shifter using a hilbert transformer neil. However, it is difficult to implement a phase shifter into a wide band model.
This is a set of notes i put together for my computer architecture clas s in 1990. Digital implementation of 90 phase shifters is in high demand as many of the digital. Low level rf system for the european spallation sources bilbao linac. How to measure phase difference of two signals of the same frequency in an fpga. Direct digital synthesis dds is a method of producing an analog waveformusually a sine waveby generating a timevarying signal in digital form and then performing a digitaltoanalog conversion. Binary phase shift keying bpsk modulation iit kanpur. Phase shifters and iq modulators admiral microwaves.
The effect of integrator is to allow the transmitted digital signal to keep hitting. When shift 1, the lsb bit filled with 0 and when shift 0, then outp inp. Phase shifting a clock by 90 degrees without using any built in clock managers. The problem that im facing is that there is some kind of restriction to the for loop that i have to put a constant as sentinel value. Phase shifters and iq modulators general microwave corporation has been a leader in the. Complete data sheet for the correct specified value. Signals and channels a signal is some form of energy light, voltage, etc varies with time onoff, highlow, etc.
Jun 19, 2015 the design in these labs was first developed in vhdl you can check the final vhdl version in the link below as well as intructions on how to set up the waveshare development board to get started. A simple digital vhdl qpsk modulator designed using cpld. Any digital modulation scheme uses a finite number of distinct signals to represent digital data. This block represents an important part of the decimation filter block, for a particular powermeter integrated. A signal is pulse code modulated to convert its analog information into a binary sequence, i. It should be noted that shifting the random number so that it overlaps the abit word is. Vhdl code for shift register can be categorised in serial in serial out shift register, serial in parallel out shift register, parallel in parallel out shift register and parallel in serial out shift. Veriloga and their simulation in the cadence analog design environment. Further it can be used as parallel to serial converter or serial to parallel converter. Can be continuous or discrete we assume it is periodic with a fixed frequency a channel is a physical medium that conveys energy any real channel will distort the input signal as it does so how it distorts the signal depends on the signal and the. So, it is the time to see an example of vhdl implementation of a digital sinusoidal generator. Abstractan architecture of the digital phase shift circuit implemented as a programmable delay line pdl is presented in this paper. Varactor analog phase shifters can achieve a large amount of phase shift and high speed and require fewer diodes than digital phase shifters, but at the cost of decreased accuracy, relatively narrow bandwidth, and low input power levels less than 1 w.
For instance, say i have two 150 mhz signals internal to the fpga that are synchronous to each other, but they are offset by some constant phase difference, how would i be able to measure this. Vhdl online a collection of vhdl related internet resources. Direct digital synthesis dds sine wave generation, phase accumulator. These samples are fed into a dynamic pll with phase shift in the fpga. Im trying to implement this on a digilent basys 2 board. While books on vhdl give limited emphasis to digital design concepts, and books on digital design discuss vhdl only brie. Vhdl andverilog ieee standard based as hardware structures language described 6, 7, 14, 15. This article is available in pdf format for easy printing. Jul 28, 2011 in this article, we present an efficient way of implementing 90 phase shifter using hilbert transformer with canonic signed digit csd coefficients in fpga. The output of a pcm will resemble a binary sequence. Students had a project in which they had to model a.
I read a few articles tutorials and they have very nice diagrams of antenna arrays and how the antennas interact to behind each antenna is the key piece. In this chapter various examples are added, which can be used to implement or emulate a system on the fpga board. Methods for rf conversion to digital i in phase and q. Unless, of course, you can stand the n clocks of latency to actually rotate the data in the shifter. One further consideration is the phase shift caused by the parallel combination of c2 and re 1gm. This concise and interesting book provides a detailed approach to fpgabased digital circuit and system design using vhdl. Nco ip core generates numerically controlled oscillators ncos. Of them all, the digital modulation technique used is pulse code modulation pcm.
Fpga based sinecosine encoder to digital converter using. A technical tutorial on digital signal synthesis analog devices. Chang from korea 2 vhdl examples and microprocessor models from uk 3 lots of examples pdf doc both on vhdl and verilog from. Binary phase shift keying is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference carrier signal. Clock and data recovery for serial digital communication. I am trying to use xilinx tools to define and simulate an 8bit shifter in vhdl that can shift or rotate left or right by 0,1,2 or 3 bit positions.
Tutorials, examples, code for beginners in digital design. Simple vhdl implementation following code will output a binary ramp or sequential values from a lookup table at a frequency proportional to the value in the phase. The algorithms that have been developed are a digital phase shifter in order to. The phase shift unit also provides a digital interface for the fpga application to dynamically advance or retard the current shift value by 1256 th of the clock period. Introduction hardware description language hd is used to model digital circuils using codes. A conceptual diagram of a phase shifter is shown in figure 1, where the bold lines indicate. Can anyone show me what the vhdl code should look like. Clock input to dynamic phase shifter, clocked on rising edge. Design units in vhdl object and data types entity architecture component con. Vhdl programming for sequential circuits tutorialspoint.
Efficient implementation of 90 phase shifter in fpga. So, pick the length of cable you need to produce a delay that corresponds to the correct phase shift at the frequency in question. I have a 32 bit barrel shifter using behavior architecture. Certainly ic processes will improve, making higher frequency digital phase splitters more available at higher frequencies. Romanofsky national aeronautics and space administration glenn research center cleveland, ohio 445 introduction while there are a myriad of applications for microwave phase shifters in instrumentation and. This video lecture discusses complete basics of quadrature phase shift keying qpsk. The input signals to the phase shift unit are psincdec, psen, and psclk. Department of electrical and computer engineering university.
Fpga implementation of pi2 bpsk and pi4 qpsk for ieee 802. In digital rf system designs the quadrature signal processing involves. How to implement a sinusoidal dds in vhdl surfvhdl. Phase shifter design research study and verification of. In this section, shift register is implemented which can be used for shifting data in both direction. To learn to establish communications with peripherals, in this case the dac ltc 2624. Vhdl files required for this example are listed below. Lecture 12 digital modulation techniques part 1 nptelhrd. May 01, 2014 vhdl code for shift register can be categorised in serial in serial out shift register, serial in parallel out shift register, parallel in parallel out shift register and parallel in serial out shift register. Design units in vhdl object and data types part i vhdl design units 1 design units in vhdl entity architecture. Direct digital synthesis dds for idiots like me other names are. Implementation of phase shifter using cordic on fpga for. Phase shift keying qpsk modulator applied for implantable telemetry applications as demonstrated.
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