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. The phase shift unit also provides a digital interface for the fpga application to dynamically. Design units in vhdl object and data types entity architecture component con. It presents the basic concepts in organized and progressive phases. In essence, the reference clock frequency is divided down in a dds. How to implement a sinusoidal dds in vhdl surfvhdl. Binary phase shift keying bpsk modulation iit kanpur. Analog phase shifters provide a continuously variable phase, most often controlled by a voltage. Direct digital synthesis dds sine wave generation, phase accumulator cordic algorithm digital filters linear timeinvariant finite impulse response fir, distributed. Merrimac offers an extensive line of manual, elec tronic, digital and precision phase shifters for both. 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. Fpga implementation of pi2 bpsk and pi4 qpsk for ieee 802. Vhdl online a collection of vhdl related internet resources.
In previous chapters, some simple designs were introduces e. Digital in the case of phase shifters means twostate devices, where the states have different insertion phases at microwave frequencies. Phase shifters can be controlled using analog signals or digital bits. It should be noted that shifting the random number so that it overlaps the abit word is. 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 textbook covers the constructs of the vhdl programming language with a large number of implementable examples. I think of simple digital phase modulation as discrete changes in phase. To achieve the abovementioned integration between vhdl and digital design, the following steps are taken. So, it is the time to see an example of vhdl implementation of a digital sinusoidal generator. However, it is difficult to implement a phase shifter into a wide band model. A conceptual diagram of a phase shifter is shown in figure 1, where the bold lines indicate. Analog devices digital phase shifters change the phase of rf, microwave, or millimeter wave signals while providing no amplitude change. Improvement of rf vector modulator performance by feed. So, what is the future of quadrature phase generation. A 32bit barrel shifter, then, has thirtytwo 32input multiplexors. Phase or frequency shifter using a hilbert transformer neil. Tutorials, examples, code for beginners in digital design. Vhdl 4 bit shifter rotator structural design using components. Phase shifters and iq modulators general microwave corporation has been a leader in the.
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. You will understand here, what is qpsk, why it is called as qpsk, how the qpsk is different from other digital. Can anyone show me what the vhdl code should look like. Fpga implementation of pi2 bpsk and pi4 qpsk for ieee. 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. Method modulator design all analogue or hybrid analogue digital qpsk modulators work with phase shift carrier angle. 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.
Consequently the output is solely a function of the current inputs. In this chapter various examples are added, which can be used to implement or emulate a system on the fpga board. Veriloga and their simulation in the cadence analog design environment. Complete data sheet for the correct specified value. Phase shifters and iq modulators admiral microwaves. A simple digital vhdl qpsk modulator designed using cpld. Uses a feedback shift register to randomize data reversing process at receiver restores original data. Like any hardware description language, it is used for many purposes. Xilinx xapp462 using digital clock managers dcms in. Later, we will study circuits having a stored internal state, i.
Fpga based sinecosine encoder to digital converter using deltasigma technology dipl. A technical tutorial on digital signal synthesis analog devices. 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. Simple barrel shifter figure below shows the barrel shifter. Signals and channels a signal is some form of energy light, voltage, etc varies with time onoff, highlow, etc. 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. Low level rf system for the european spallation sources bilbao linac. Any digital modulation scheme uses a finite number of distinct signals to represent digital data. Clock and data recovery for serial digital communication.
Clock and data recovery for serial digital communication plus a tutorial on bangbang phase lockedloops rick walker hewlettpackard company palo alto, california. The fixed phase shift value is set at design time and loaded into the dcm during fpga configuration. This article is available in pdf format for easy printing. Students had a project in which they had to model a. To learn to establish communications with peripherals, in this case the dac ltc 2624.
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. Design examples fpga designs with vhdl documentation. Programmable phase shift circuit for an integrated powermeter. Binary phase shift keying is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference carrier signal. Further it can be used as parallel to serial converter or serial to parallel converter.
So based on this the code with process can be updated to. 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. The multiplexer is used to transmit the corresponding phase shifted carrier signal depending upon the data. Vhdl programming for sequential circuits this chapter explains how to do vhdl programming for sequential circuits.
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. Vhdl programming for sequential circuits tutorialspoint. The input signals to the phase shift unit are psincdec, psen, and psclk. 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. Design units in vhdl object and data types part i vhdl design units 1 design units in vhdl entity architecture. Field programmable gate array fpga for digital pro cessing. An introduction to vhdl overview dinesh sharma microelectronics group, ee department iit bombay, mumbai august 2008 dinesh sharma vhdl.
Unless, of course, you can stand the n clocks of latency to actually rotate the data in the shifter. 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. Nco ip core generates numerically controlled oscillators ncos. Digital electronics part i combinational and sequential logic. In the last section a tutorial is introduced where the reader can learn how to. Note that vhdl shift infix operators before vhdl 2008 are known to give unexpected results, so use the functions instead. These samples are fed into a dynamic pll with phase shift in the fpga. Fpgabased pulsedrf phase and amplitude detector at. In this section, shift register is implemented which can be used for shifting data in both direction. The effect of integrator is to allow the transmitted digital signal to keep hitting. Abstractan architecture of the digital phase shift circuit implemented as a programmable delay line pdl is presented in this paper.
Direct digital synthesis dds sine wave generation, phase accumulator. 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. Of them all, the digital modulation technique used is pulse code modulation pcm. The phase shift unit shifts the phase of all nine dcm clock output signals by a fixed fraction of the input clock period. They are used in a variety of applications, including rf pa linearizationrf distortion, amplitude and phase modulation, variable attenuators, and fiber optics. The algorithms that have been developed are a digital phase shifter in order to. This block represents an important part of the decimation filter block, for a particular powermeter integrated. 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. Introduction hardware description language hd is used to model digital circuils using codes. This is a set of notes i put together for my computer architecture clas s in 1990. The digital control interface allows to control the phasegain.
Methods for rf conversion to digital i in phase and q. There are many modulation techniques, which are classified according to the type of modulation employed. Vhdl files required for this example are listed below. Vhdl tutorial for beginners this tutorial is intended for beginners who wish to learn vhdl. 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. How to measure phase difference of two signals of the same. 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. One further consideration is the phase shift caused by the parallel combination of c2 and re 1gm. Direct digital synthesis dds for idiots like me other names are. 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.
Chang from korea 2 vhdl examples and microprocessor models from uk 3 lots of examples pdf doc both on vhdl and verilog from. The entity declaration defines the circuits external interface and the architecture defines its internal implementation. Phase shift keying qpsk modulator applied for implantable telemetry applications as demonstrated. Shift register are the registers which are used to shift the stored bit in one or both directions. 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. 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. Phase shifting a clock by 90 degrees without using any built in clock managers. 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. A signal is pulse code modulated to convert its analog information into a binary sequence, i. In a block diagram or abridged schematic, we often show. Efficient implementation of 90 phase shifter in fpga. Digital implementation of phase locked loop on fpga.
How to measure phase difference of two signals of the same frequency in an fpga. Oh yeah, i dont understand why the else conditions are not valid. Clock input to dynamic phase shifter, clocked on rising edge. It is intended, among other things, as a modeling langua ge for specification and simulation. The effect is minimized by making c2 large and re large. While books on vhdl give limited emphasis to digital design concepts, and books on digital design discuss vhdl only brie. Vhdl programming code is used to generate qpsk digital signal.
I have a 32 bit barrel shifter using behavior architecture. Digital implementation of 90 phase shifters is in high demand as many of the digital. Representing the filter coefficients by csd eliminates the need for multipliers and the filter is implemented using shifters and adderssubtractors. Xilinx xapp462 using digital clock managers dcms in spartan. So, pick the length of cable you need to produce a delay that corresponds to the correct phase shift at the frequency in question. 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. 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. Xilinx xapp462 using digital clock managers dcms in spartan3. I wanna produce a constant phase shift of 120 degree at ghz. Here the dds uses lookup table to generate the sinusoids.
Phase shifter design research study and verification of. This concise and interesting book provides a detailed approach to fpgabased digital circuit and system design using vhdl. Department of electrical and computer engineering university. 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.
Vhdl provides standard shift functions, which should be used, instead of the home build that even looks wrong. Certainly ic processes will improve, making higher frequency digital phase splitters more available at higher frequencies. Coordinate rotation digital computer cordic is an efficient and versatile algorithm that can implement a phase shift without using multipliers. Implementation of phase shifter using cordic on fpga for. Designing digital circuits using vhdl 8 its important to understand the distinction between the entity declaration and the architecture. The output of a pcm will resemble a binary sequence. 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. Schottky diodes are also used as variable elements in analog phase shifters, but. Oscillators university of california, santa barbara. I couldnt figure out how you thought you had a 90 phase shift between the two signals.
Vhdl andverilog ieee standard based as hardware structures language described 6, 7, 14, 15. 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. Phase shifter fundamentals phase shifters are a critical component in many rf and microwave systems. The dds digital architecture eliminates the need for the manual system. The input test signals data and carrier are interfaced to the cpld and fpgas board from agilent function generator e8408a. Objectives to design a binary phase shift keying modulator bpsk by using vhdl and its implementation in a fpga. This video lecture discusses complete basics of quadrature phase shift keying qpsk. Is there any possible ic for it probably the answer is no i am not sure. The purpose of this tutorial is to describe the modeling language vhdl. 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. Digital iq modulation phase shift keying constellations lecture 9 analog and digital iq modulation. 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. In digital rf system designs the quadrature signal processing involves. So i wanna know how to implement the same on fpga, i.
Ashenden vhdl examples 1 vhdl examples for synthesis by dr. There will be a slight phase shift that will move the total phase around the loop off the peak of the resonator. 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. 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. Fpga based sinecosine encoder to digital converter using. This note introduces the student to the design of digital logic circuits, both combinational and sequential, and the design of digital systems in a hierarchical, topdown manner. It is implemented using 27tap symmetric finite impulse response fir filter. Phased array antenna processing on reconfigurable hardware. Im trying to implement this on a digilent basys 2 board. You can also use ncos in all digital phase lockedloops plls for carrier synchronization in communications receivers, or as standalone frequency shift keying fsk or phase shift keying psk modulators.
717 42 1273 11 1119 349 1448 1397 1569 1232 802 896 49 1358 531 1291 888 218 566 1364 1175 628 1186 741 1285 425 86 950 705 731