Telecommunication Circuits and Technology
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Ariel Moss EE 254 Project 6 12/6/13 Project 6: Oscillator Circuits The
Ariel Moss EE 254 Project 6 12/6/13 Project 6: Oscillator Circuits The purpose of this experiment was to design two oscillator circuits: a Wien-Bridge oscillator at 3 kHz oscillation and a Hartley Oscillator using a BJT at 5 kHz oscillation. The first oscillator designed was a Wien-Bridge oscillator (Figure 1). Before designing the circuit, some background information was collected. An input signal sent to the non-inverting terminal with a parallel and series RC configuration as well as two resistors connected in inverting circuit types to achieve gain. The circuit works because the RC network is connected to the positive feedback part of the amplifier, and has a zero phase shift at a frequency. At the oscillation frequency, the voltages applied to both the inputs will be in phase, which causes the positive and negative feedback to cancel out. This causes the signal to oscillate. To calculate the time constant given the cutoff frequency, Calculation 1 was used. The capacitor was chosen to be 0.1µF, which left the input, series, and parallel resistors to be 530Ω and the output resistor to be 1.06 kHz. The signal was then simulated in PSPICE, and after adjusting the output resistor to 1.07Ω, the circuit produced a desired simulation with time spacing of .000335 seconds, which was very close to the calculated time spacing. (Figures 2-3 and Calculations 2-3). R2 1.07k 10Vdc V1 R1 LM741 4 2 V- 1 - OS1 530 6 OUT 0 3 5 + 7 OS2 U1 V+ V2 10Vdc Cs Rs 0.1u 530 Cp Rp 0.1u 530 0 Figure 2: Wien-Bridge Oscillator built in PSPICE Ariel Moss EE 254 Project 6 12/6/13 Figure 3: Simulation of circuit Next the circuit was built and tested. -
Chapter 19 - the Oscillator
Chapter 19 - The Oscillator The Electronics Curse “Your amplifiers will oscillate, your oscillators won't!” Question, What is an Oscillator? A Pendulum is an Oscillator... “Oscillators are circuits that are used to generate A.C. signals. Although mechanical methods, like alternators, can be used to generate low frequency A.C. signals, such as the 50 Hz mains, electronic circuits are the most practical way of generating signals at radio frequencies.” Comment: Hmm, wasn't always. In the time of Marconi, generators were used to generate a frequency to transmit. We are talking about kiloWatts of power! e.g. Grimeton L.F. Transmitter. Oscillators are widely used in both transmitters and receivers. In transmitters they are used to generate the radio frequency signal that will ultimately be applied to the antenna, causing it to transmit. In receivers, oscillators are widely used in conjunction with mixers (a circuit that will be covered in a later module) to change the frequency of the received radio signal. Principal of Operation The diagram below is a ‘block diagram’ showing a typical oscillator. Block diagrams differ from the circuit diagrams that we have used so far in that they do not show every component in the circuit individually. Instead they show complete functional blocks – for example, amplifiers and filters – as just one symbol in the diagram. They are useful because they allow us to get a high level overview of how a circuit or system functions without having to show every individual component. The Barkhausen Criterion [That's NOT ‘dog box’ in German!] Comment: In electronics, the Barkhausen stability criterion is a mathematical condition to determine when a linear electronic circuit will oscillate. -
Analysis of BJT Colpitts Oscillators - Empirical and Mathematical Methods for Predicting Behavior Nicholas Jon Stave Marquette University
Marquette University e-Publications@Marquette Master's Theses (2009 -) Dissertations, Theses, and Professional Projects Analysis of BJT Colpitts Oscillators - Empirical and Mathematical Methods for Predicting Behavior Nicholas Jon Stave Marquette University Recommended Citation Stave, Nicholas Jon, "Analysis of BJT Colpitts sO cillators - Empirical and Mathematical Methods for Predicting Behavior" (2019). Master's Theses (2009 -). 554. https://epublications.marquette.edu/theses_open/554 ANALYSIS OF BJT COLPITTS OSCILLATORS – EMPIRICAL AND MATHEMATICAL METHODS FOR PREDICTING BEHAVIOR by Nicholas J. Stave, B.Sc. A Thesis submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for the Degree of Master of Science Milwaukee, Wisconsin August 2019 ABSTRACT ANALYSIS OF BJT COLPITTS OSCILLATORS – EMPIRICAL AND MATHEMATICAL METHODS FOR PREDICTING BEHAVIOR Nicholas J. Stave, B.Sc. Marquette University, 2019 Oscillator circuits perform two fundamental roles in wireless communication – the local oscillator for frequency shifting and the voltage-controlled oscillator for modulation and detection. The Colpitts oscillator is a common topology used for these applications. Because the oscillator must function as a component of a larger system, the ability to predict and control its output characteristics is necessary. Textbooks treating the circuit often omit analysis of output voltage amplitude and output resistance and the literature on the topic often focuses on gigahertz-frequency chip-based applications. Without extensive component and parasitics information, it is often difficult to make simulation software predictions agree with experimental oscillator results. The oscillator studied in this thesis is the bipolar junction Colpitts oscillator in the common-base configuration and the analysis is primarily experimental. The characteristics considered are output voltage amplitude, output resistance, and sinusoidal purity of the waveform. -
AM Transmitters
Chapter 4: AM Transmitters Chapter 4 Objectives At the conclusion of this chapter, the reader will be able to: • Draw a block diagram of a high or low-level AM transmitter, giving typical signals at each point in the circuit. • Discuss the relative advantages and disadvantages of high and low-level AM transmitters. • Identify an RF oscillator configuration, pointing out the components that control its frequency. • Describe the physical construction of a quartz crystal. • Calculate the series and parallel resonant frequencies of a quartz crystal, given manufacturer's data. • Identify the resonance modes of a quartz crystal in typical RF oscillator circuits. • Describe the operating characteristics of an RF amplifier circuit, given its schematic diagram. • Explain the operation of modulator circuits. • Identify the functional blocks (amplifiers, oscillators, etc) in a schematic diagram. • List measurement procedures used with AM transmitters. • Develop a plan for troubleshooting a transmitter. In Chapter 3 we studied the theory of amplitude modulation, but we never actually built an AM transmitter. To construct a working transmitter (or receiver), a knowledge of RF circuit principles is necessary. A complete transmitter consists of many different stages and hundreds of electronic components. When beginning technicians see the schematic diagram of a "real" electronic system for the first time, they're overwhelmed. A schematic contains much valuable information. But to the novice, it's a swirling mass of resistors, capacitors, coils, transistors, and IC chips, all connected in a massive web of wires! How can anyone understand this? All electronic systems, no matter how complex, are built from functional blocks or stages. -
Oscillator Design
Oscillator Design •Introduction –What makes an oscillator? •Types of oscillators –Fixed frequency or voltage controlled oscillator –LC resonator –Ring Oscillator –Crystal resonator •Design of oscillators –Frequency control, stability –Amplitude limits –Buffered output –isolation –Bias circuits –Voltage control –Phase noise 1 Oscillator Requirements •Power source •Frequency-determining components •Active device to provide gain •Positive feedback LC Oscillator fr = 1/ 2p LC Hartley Crystal Colpitts Clapp RC Wien-Bridge Ring 2 Feedback Model for oscillators x A(jw) i xo A (jw) = A f 1 - A(jω)×b(jω) x = x + x d i f Barkhausen criteria x f A( jw)× b ( jω) =1 β Barkhausen’scriteria is necessary but not sufficient. If the phase shift around the loop is equal to 360o at zero frequency and the loop gain is sufficient, the circuit latches up rather than oscillate. To stabilize the frequency, a frequency-selective network is added and is named as resonator. Automatic level control needed to stabilize magnitude 3 General amplitude control •One thought is to detect oscillator amplitude, and then adjust Gm so that it equals a desired value •By using feedback, we can precisely achieve GmRp= 1 •Issues •Complex, requires power, and adds noise 4 Leveraging Amplifier Nonlinearity as Feedback •Practical trans-conductance amplifiers have saturating characteristics –Harmonics created, but filtered out by resonator –Our interest is in the relationship between the input and the fundamental of the output •As input amplitude is increased –Effective gain from input -
Lec#12: Sine Wave Oscillators
Integrated Technical Education Cluster Banna - At AlAmeeria © Ahmad El J-601-1448 Electronic Principals Lecture #12 Sine wave oscillators Instructor: Dr. Ahmad El-Banna 2015 January Banna Agenda - © Ahmad El Introduction Feedback Oscillators Oscillators with RC Feedback Circuits 1448 Lec#12 , Jan, 2015 Oscillators with LC Feedback Circuits - 601 - J Crystal-Controlled Oscillators 2 INTRODUCTION 3 J-601-1448 , Lec#12 , Jan 2015 © Ahmad El-Banna Banna Introduction - • An oscillator is a circuit that produces a periodic waveform on its output with only the dc supply voltage as an input. © Ahmad El • The output voltage can be either sinusoidal or non sinusoidal, depending on the type of oscillator. • Two major classifications for oscillators are feedback oscillators and relaxation oscillators. o an oscillator converts electrical energy from the dc power supply to periodic waveforms. 1448 Lec#12 , Jan, 2015 - 601 - J 4 FEEDBACK OSCILLATORS FEEDBACK 5 J-601-1448 , Lec#12 , Jan 2015 © Ahmad El-Banna Banna Positive feedback - • Positive feedback is characterized by the condition wherein a portion of the output voltage of an amplifier is fed © Ahmad El back to the input with no net phase shift, resulting in a reinforcement of the output signal. Basic elements of a feedback oscillator. 1448 Lec#12 , Jan, 2015 - 601 - J 6 Banna Conditions for Oscillation - • Two conditions: © Ahmad El 1. The phase shift around the feedback loop must be effectively 0°. 2. The voltage gain, Acl around the closed feedback loop (loop gain) must equal 1 (unity). 1448 Lec#12 , Jan, 2015 - 601 - J 7 Banna Start-Up Conditions - • For oscillation to begin, the voltage gain around the positive feedback loop must be greater than 1 so that the amplitude of the output can build up to a desired level. -
TRANSIENT STABILITY of the WIEN BRIDGE OSCILLATOR I
TRANSIENT STABILITY OF THE WIEN BRIDGE OSCILLATOR i TRANSIENT STABILITY OF THE WIEN BRIDGE OSCILLATOR by RICHARD PRESCOTT SKILLEN, B. Eng. A Thesis Submitted ··to the Faculty of Graduate Studies in Partial Fulfilment of the Requirements for the Degree Master of Engineering McMaster University May 1964 ii MASTER OF ENGINEERING McMASTER UNIVERSITY (Electrical Engineering) Hamilton, Ontario TITLE: Transient Stability of the Wien Bridge Oscillator AUTHOR: Richard Prescott Skillen, B. Eng., (McMaster University) NUMBER OF PAGES: 105 SCOPE AND CONTENTS: In many Resistance-Capacitance Oscillators the oscillation amplitude is controlled by the use of a temperature-dependent resistor incorporated in the negative feedback loop. The use of thermistors and tungsten lamps is discussed and an approximate analysis is presented for the behaviour of the tungsten lamp. The result is applied in an analysis of the familiar Wien Bridge Oscillator both for the presence of a linear circuit and a cubic nonlinearity. The linear analysis leads to a highly unstable transient response which is uncommon to most oscillators. The inclusion of the slight cubic nonlinearity, however, leads to a result which is in close agreement to the observed response. ACKNOWLEDGEMENTS: The author wishes to express his appreciation to his supervisor, Dr. A.S. Gladwin, Chairman of the Department of Electrical Engineering for his time and assistance during the research work and preparation of the thesis. The author would also like to thank Dr. Gladwin and all his other undergraduate professors for encouragement and instruction in the field of circuit theor.y. Acknowledgement is also made for the generous financial support of the thesis project by the Defence Research Board·under grant No. -
Unit I - Feedback Amplifiers Part - a 1
EC6401 Electronic Circuits II Department of ECE 2014-2015 UNIT I - FEEDBACK AMPLIFIERS PART - A 1. Define positive and negative feedback? Ans: Positive feedback: If the feedback voltage (or current) is so applied as to increase the input voltage (i.e. it is in phase with it), then it is called positive feedback. Negative feedback: If the feedback voltage (or current) is so applied as to reduce the input voltage (i.e. it is 180out of phase with it), then it is called negative feedback. 2. What are the advantages of negative feedback? Ans: The advantages of negative feedback are higher fidelity and stabilized gain, increased bandwidth, less distortion and reduced noise and input & output impedances can be modified as desired. 3. List four basic types of feedback? Ans: (1) Voltage series feedback (2) Voltage shunt feedback (3) Current series feedback and (4) Current shunt feedback. 4. Negative feedback is preferred to other methods of modifying Amplifier characteristics. Why? Ans: Negative feedback is preferred to other methods of modifying Amplifier Characteristics because it has the following advantages of reduction in distortion, stability in gain, increased bandwidth etc. 5. State the condition in (1+A) which a feedback amplifier must satisfy in order to be stable. Ans: The two important and necessary conditions are (1) The feedback must be positive, (2) Feedback factor must be unity i.e. A = 1 6. What is meant by phase and gain margin? Ans: Phase Margin: It is defined as 1800 minus the magnitude of the Aat the frequency at which A is unity. If he phase margin is negative the system is stable otherwise unstable. -
Oscillator Circuits
Oscillator Circuits 1 II. Oscillator Operation For self-sustaining oscillations: • the feedback signal must positive • the overall gain must be equal to one (unity gain) 2 If the feedback signal is not positive or the gain is less than one, then the oscillations will dampen out. If the overall gain is greater than one, then the oscillator will eventually saturate. 3 Types of Oscillator Circuits A. Phase-Shift Oscillator B. Wien Bridge Oscillator C. Tuned Oscillator Circuits D. Crystal Oscillators E. Unijunction Oscillator 4 A. Phase-Shift Oscillator 1 Frequency of the oscillator: f0 = (the frequency where the phase shift is 180º) 2πRC 6 Feedback gain β = 1/[1 – 5α2 –j (6α – α3) ] where α = 1/(2πfRC) Feedback gain at the frequency of the oscillator β = 1 / 29 The amplifier must supply enough gain to compensate for losses. The overall gain must be unity. Thus the gain of the amplifier stage must be greater than 1/β, i.e. A > 29 The RC networks provide the necessary phase shift for a positive feedback. They also determine the frequency of oscillation. 5 Example of a Phase-Shift Oscillator FET Phase-Shift Oscillator 6 Example 1 7 BJT Phase-Shift Oscillator R′ = R − hie RC R h fe > 23 + 29 + 4 R RC 8 Phase-shift oscillator using op-amp 9 B. Wien Bridge Oscillator Vi Vd −Vb Z2 R4 1 1 β = = = − = − R3 R1 C2 V V Z + Z R + R Z R β = 0 ⇒ = + o a 1 2 3 4 1 + 1 3 + 1 R4 R2 C1 Z2 R4 Z2 Z1 , i.e., should have zero phase at the oscillation frequency When R1 = R2 = R and C1 = C2 = C then Z + Z Z 1 2 2 1 R 1 f = , and 3 ≥ 2 So frequency of oscillation is f = 0 0 2πRC R4 2π ()R1C1R2C2 10 Example 2 Calculate the resonant frequency of the Wien bridge oscillator shown above 1 1 f0 = = = 3120.7 Hz 2πRC 2 π(51×103 )(1×10−9 ) 11 C. -
A 20 Mv Colpitts Oscillator Powered by a Thermoelectric Generator
A 20 mV Colpitts Oscillator powered by a thermoelectric generator Fernando Rangel de Sousa∗, Marcio Bender Machado∗†, Carlos Galup-Montoro ∗ ∗Integrated Circuits Laboratory-LCI Federal University of Santa Catarina-UFSC Florianopolis-SC, Brazil, Tel.: +55-48-3721-7640 Email:[email protected] † Sul-Rio-Grandense Federal Institute Charqueadas-RS, Brazil Email:[email protected] Abstract—In this paper, we present a MOSFET-based Colpitts of around 13 mV , only seven milivolts far from the voltage oscillator based on a “zero-threshold” transistor operating at a supply value for which the circuit sustained oscillations at 130 supply voltage below 20 mV. The circuit was carefully analyzed mV(peak-to-peak)/97 kHz. Moreover, the circuit was powered and expressions relating the start-up conditions and the voltage supply, as well as the oscillation frequency were developed. by a thermoelectric generator which supplied a DC voltage of Measurement results obtained on a discrete prototype confirmed around 22 mV when it was installed on the arm of a person the low-voltage operation of the oscillator, which sustained in a 24oC room. oscillations of 130 mV (peak-to-peak) at 97 kHz when the voltage supply was 19.8 mV. The circuit was also powered from a II. COLPITTS OSCILLATOR thermoelectric generator (TEG) connected to a persons arm in a room with temperature of 24oC room. Under these conditions, A Colpitts oscillator can be broken in two main blocks : i) the TEG supplied 22 mV and the circuit operated as expected. a potentially unstable one-port and ii) a load network, as it is shown in Fig. -
A Study of Phase Noise in Colpitts and LC-Tank CMOS Oscillators
Downloaded from orbit.dtu.dk on: Oct 02, 2021 A study of phase noise in colpitts and LC-tank CMOS oscillators Andreani, Pietro; Wang, Xiaoyan; Vandi, Luca; Fard, A. Published in: I E E E Journal of Solid State Circuits Link to article, DOI: 10.1109/JSSC.2005.845991 Publication date: 2005 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Andreani, P., Wang, X., Vandi, L., & Fard, A. (2005). A study of phase noise in colpitts and LC-tank CMOS oscillators. I E E E Journal of Solid State Circuits, 40(5), 1107-1118. https://doi.org/10.1109/JSSC.2005.845991 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 40, NO. 5, MAY 2005 1107 A Study of Phase Noise in Colpitts and LC-Tank CMOS Oscillators Pietro Andreani, Member, IEEE, Xiaoyan Wang, Luca Vandi, and Ali Fard Abstract—This paper presents a study of phase noise in CMOS phase noise itself. -
Ultra Low Power RC Oscillator for System Wake-Up Using Highly
Ultra Low Power RC Oscillator for System wake-up using highly precise Auto-Calibration Technique Joonhyung, Lim#1, Kwangmook, Lee#2, Koonsik, Cho#3 # Ubiquitous Conversion Team, Samsung Electro-Mechanics, Suwon, Gyunggi-Do, Korea, 443-743 [email protected], [email protected], [email protected] Abstract— An ultra low power RC oscillator for system wake-up A. The design of RC oscillator is implemented using 0.18um CMOS process. The modern mobile systems need system clock which consumes low power and thus saves limited battery power in order to wake up from sleep-mode. A RC oscillator operates in the subthreshold region to reduce current consumption. The output frequency of RC oscillator is very weakly dependent on process and temperature variation using auto-calibration. This RC oscillator is featured as follows: the current consumption is 0.2 ㎂; the supply voltage is 1.8V; the output frequency is 31.25 KHz with 1.52(Relative 3σ)% accuracy after calibration; it has only 0.4%/℃ temperature coefficient; its size is 190 um x 80 um exclude bonding pad. I. INTRODUCTION Many applications, such as PDA, mobile communication devices need to operate with low power consumption and low supply voltage to fulfil the requirement of long-term operation. For such System-on-Chips (SoCs), embedded a system wake up circuit is necessary [1]. Several analogue and digital blocks such as clock generator, timer and SRAM for retention must be activated to wake system up from a sleep-mode. Especially, a clock generator, which is the heart of digital circuits, will output unknown waveform of clock and the system will enter Fig.