Amplitude Modulation and Demodulation
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Chapter 1 Experiment-8
Chapter 1 Experiment-8 1.1 Single Sideband Suppressed Carrier Mod- ulation 1.1.1 Objective This experiment deals with the basic of Single Side Band Suppressed Carrier (SSB SC) modulation, and demodulation techniques for analog commu- nication.− The student will learn the basic concepts of SSB modulation and using the theoretical knowledge of courses. Upon completion of the experi- ment, the student will: *UnderstandSSB modulation and the difference between SSB and DSB modulation * Learn how to construct SSB modulators * Learn how to construct SSB demodulators * Examine the I Q modulator as SSB modulator. * Possess the necessary tools to evaluate and compare the SSB SC modulation to DSB SC and DSB_TC performance of systems. − − 1.1.2 Prelab Exercise 1.Using Matlab or equivalent mathematics software, show graphically the frequency domain of SSB SC modulated signal (see equation-2) . Which of the sign is given for USB− and which for LSB. 1 2 CHAPTER 1. EXPERIMENT-8 2. Draw a block diagram and explain two method to generate SSB SC signal. − 3. Draw a block diagram and explain two method to demodulate SSB SC signal. − 4. According to the shape of the low pass filter (see appendix-1), choose a carrier frequency and modulation frequency in order to implement LSB SSB modulator, with minimun of 30 dB attenuation of the USB component. 1.1.3 Background Theory SSB Modulation DEFINITION: An upper single sideband (USSB) signal has a zero-valued spectrum for f <fcwhere fc, is the carrier frequency. A lower single| | sideband (LSSB) signal has a zero-valued spectrum for f >fc where fc, is the carrier frequency. -
AM Demodulation(Peak Detect.)
AM Demodulation (peak detect.) Demodulation is about recovering the original signal--Crystal Radio Example Antenna = Long WireFM AM A simple Diode! (envelop of AM Signal) Tuning Demodulation Filter Circuit Circuit (Mechanical) Basically a “tapped” Inductor (L) and variable Capacitor (C) We’ll not spend a lot of time on the AM “crystal radio”, although I love it dearly as a COOL, ultra-minimal piece of electronics-- Imagine, you get radio FREE with no batteries required. But… The things we will look at and actually do a bit in lab is to consider the “peak detector” (I.e. the means for demodulating the AM signal) From a block diagram point of view, the circuit has a tuning component (frequency selective filter) attached to the antenna (basically a wire for the basic X-tal radio). The demodulation consists of a diode (called the “crystal” from the good old days of “Empire of the Air”…movie we’ll watch) and an R-C filter to get rid of the carrier frequency. In the Radio Shack version there is no “C” needed; your ear bones can’t respond to the carrier so they act as “the filter”. The following slide gives a more electronics-oriented view of the circuit… 1 Signal Flow in Crystal Radio-- +V Circuit Level Issues Wire=Antenna -V time Filter: BW •fo set by LC •BW set by RLC fo music “tuning” ground=0V time “KX” “KY” “KZ” frequency +V (only) So, here’s the incoming (modulated) signal and the parallel L-C (so-called “tank” circuit) that is hopefully selective enough (having a high enough “Q”--a term that you’ll soon come to know and love) that “tunes” the radio to the desired frequency. -
Bias Circuits for RF Devices
Bias Circuits for RF Devices Iulian Rosu, YO3DAC / VA3IUL, http://www.qsl.net/va3iul A lot of RF schematics mention: “bias circuit not shown”; when actually one of the most critical yet often overlooked aspects in any RF circuit design is the bias network. The bias network determines the amplifier performance over temperature as well as RF drive. The DC bias condition of the RF transistors is usually established independently of the RF design. Power efficiency, stability, noise, thermal runway, and ease to use are the main concerns when selecting a bias configuration. A transistor amplifier must possess a DC biasing circuit for a couple of reasons. • We would require two separate voltage supplies to furnish the desired class of bias for both the emitter-collector and the emitter-base voltages. • This is in fact still done in certain applications, but biasing was invented so that these separate voltages could be obtained from but a single supply. • Transistors are remarkably temperature sensitive, inviting a condition called thermal runaway. Thermal runaway will rapidly destroy a bipolar transistor, as collector current quickly and uncontrollably increases to damaging levels as the temperature rises, unless the amplifier is temperature stabilized to nullify this effect. Amplifier Bias Classes of Operation Special classes of amplifier bias levels are utilized to achieve different objectives, each with its own distinct advantages and disadvantages. The most prevalent classes of bias operation are Class A, AB, B, and C. All of these classes use circuit components to bias the transistor at a different DC operating current, or “ICQ”. When a BJT does not have an A.C. -
Energy-Detecting Receivers for Wake-Up Radio Applications
Energy-Detecting Receivers for Wake-Up Radio Applications Vivek Mangal Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy under the Executive Committee of the Graduate School of Arts and Sciences COLUMBIA UNIVERSITY 2020 © 2019 Vivek Mangal All Rights Reserved Abstract Energy-Detecting Receivers for Wake-Up Radio Applications Vivek Mangal In an energy-limited wireless sensor node application, the main transceiver for communication has to operate in deep sleep mode when inactive to prolong the node battery lifetime. Wake-up is among the most efficient scheme which uses an always ON low-power receiver called the wake-up receiver to turn ON the main receiver when required. Energy-detecting receivers are the best fit for such low power operations. This thesis discusses the energy-detecting receiver design; challenges; techniques to enhance sensitivity, selectivity; and multi-access operation. Self-mixers instead of the conventional envelope detectors are proposed and proved to be op- timal for signal detection in these energy-detection receivers. A fully integrated wake-up receiver using the self-mixer in 65 nm LP CMOS technology has a sensitivity of −79.1 dBm at 434 MHz. With scaling, time-encoded signal processing leveraging switching speeds have become attractive. Baseband circuits employing time-encoded matched filter and comparator with DC offset compen- sation loop are used to operate the receiver at 420 pW power. Another prototype at 1.016 GHz is sensitive to −74 dBm signal while consuming 470 pW. The proposed architecture has 8 dB better sensitivity at 10 dB lower power consumption across receiver prototypes. -
Adapting Techniques to Improve Efficiency in Radio Frequency
electronics Article Adapting Techniques to Improve Efficiency in Radio Frequency Power Amplifiers for Visible Light Communications Daniel G. Aller 1,* , Diego G. Lamar 1, Juan Rodriguez 2, Pablo F. Miaja 1 , Valentin Francisco Romero 3, Jose Mendiolagoitia 3 and Javier Sebastian 1 1 Power Supplies Group—Electrical Engineering Department of the University of Oviedo, 33204 Gijon, Spain; [email protected] (D.G.L.); [email protected] (P.F.M.); [email protected] (J.S.) 2 Center for Industrial Electronics—Polytechnic University of Madrid, 28006 Madrid, Spain; [email protected] 3 Thyssenkrupp Elevator Innovation Center S A U—Thyssenkrupp AG, 33203 Gijon, Spain; [email protected] (V.F.R.); [email protected] (J.M.) * Correspondence: [email protected]; Tel.: +34-985-182-578 Received: 30 November 2019; Accepted: 3 January 2020; Published: 10 January 2020 Abstract: It is well known that modern wireless communications systems need linear, wide bandwidth, efficient Radio Frequency Power Amplifiers (RFPAs). However, conventional configurations of RFPAs based on Class A, Class B, and Class AB exhibit extremely low efficiencies when they manage signals with a high Peak-to-Average Power Ratio (PAPR). Traditionally, a number of techniques have been proposed either to achieve linearity in the case of efficient Switching-Mode RFPAs or to improve the efficiency of linear RFPAs. There are two categories in the application of aforementioned techniques. First, techniques based on the use of Switching-Mode DC–DC converters with a very-fast-output response (faster than 1 µs). Second, techniques based on the interaction of several RFPAs. The current expansion of these techniques is mainly due to their application in cellphone networks, but they can also be applied in other promising wireless communications systems such as Visible Light Communication (VLC). -
EE426/506 Class Notes 4/23/2015 John Stensby
EE426/506 Class Notes 4/23/2015 John Stensby Chapter 2: Basic Modulation Techniques In most communication systems, the modulated signal has the form xcc (t) A(t)cos[ t (t)], (2-1) where c is known as the carrier frequency, A(t) is the envelope and (t) is the phase. Amplitude A(t) and phase (t) may depend on message m(t). When A(t) depends linearly on the message, and is a constant independent of m, we have linear modulation. When (t) depends on m(t), we have nonlinear modulation. Linear Modulation Double Sideband (DSB) is the first form of linear modulation we will consider. The general form of a DSB signal is x(t)Am(t)cos[tDSB cc0 ], (2-2) where Ac and are constants. For convenience, we will assume that = 0. Figures 2-1a through 2-1c depict a block diagram of a DSB modulator, a sinusoidal message m and the DSB time domain wave form xDSB(t), respectively. Note that every sign change in m(t) results in a ° 180 phase shift in the transmitted signal xDSB(t). DSB is very popular when used to transmit digital data. In this application, m(t) is a digital waveform that switches between +1 and -1 volts. Hence, m(t) switches the phase of the transmitted carrier by radians. For this reason, for a ±1 binary message, the modulation is called phase-shift keying. The Fourier transform of xDSB is A X(j)x(t)M(jj)M(jj)F c , (2-3) DSB DSB2 c c Latest Updates at http://www.ece.uah.edu/courses/ee426/ 2-1 EE426/506 Class Notes 4/23/2015 John Stensby m(t) a) xDSB(t) = Acm(t)cosct Accosct m(t) b) t (t) DSB x c) t Figure 2-1: a) Block diagram of a DSB modulator. -
Signi\L PURITY CONS IDERI\TIONS for FREQUEN<:Y Sn1 Tiles I ZED Llel\DEND EQU I Pr1ent David L. Kel:Na General Instrument
SIGNi\L PURITY CONS IDERI\TIONS FOR FREQUEN<:Y Sn1 TilES I ZED llEl\DEND EQU I Pr1ENT David L. Kel:na General Instrument, Jerrold Division ABSTRACT BASIC OVERVIEW OF THE PLL As cabl~ television system band Before we evoluate the system for wirlths increase and frequency plans pro its noise performance, let us first re liferate, more manufacturers are turning view the b~sic operation of a chase to synth~sized frequency agile head~nd locked loop. A simple phase-locked loop channel converters. Uith this new ap consists of a voltage controlled oscil proach using phased lo~ked loops and dual lator, or VCO, a digital divider, a chase conversion come spurious signals and detector, a reference frequency sour~e, nois~ sources not encountered before in and an integrator or loop filter. Figure crystal controlled channel converters. 1 represents such a system. Important characteristics of these These system components function ~s headend converters including phas~ noise, a s~rvo loop sue~ that when the·vco is spurious sign3ls generated by the compar phase-locked to the reference, the output ison frequ~ncy, and residual frequency frequency and phase of the digital divi a~d phase modulation, are evaluated for der is equal to the frequency and phase their subjective impact on the output of the referenc~. This makes the average signal to the cable. D3ta is presented output of the phase detector zero and, which shows the correlation between sub therefore, the output of the loop filter jective picture degradation and measured remains unchanged. Should a disturbance headend synthesizer noise contribution. -
AN-937 Designing Amplifier Circuits
AN-937 APPLICATION NOTE One Technology Way • P. O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com Designing Amplifier Circuits: How to Avoid Common Problems by Charles Kitchin INTRODUCTION down toward the negative supply. The bias voltage is amplified When compared to assemblies of discrete semiconductors, by the closed-loop dc gain of the amplifier. modern operational amplifiers (op amps) and instrumenta- This process can be lengthy. For example, an amplifier with a tion amplifiers (in-amps) provide great benefits to designers. field effect transistor (FET) input, having a 1 pA bias current, Although there are many published articles on circuit coupled via a 0.1-μF capacitor, has an IC charging rate, I/C, of applications, all too often, in the haste to assemble a circuit, 10–12/10–7 = 10 μV per sec basic issues are overlooked leading to a circuit that does not function as expected. This application note discusses the most or 600 μV per minute. If the gain is 100, the output drifts at common design problems and offers practical solutions. 0.06 V per minute. Therefore, a casual lab test, using an ac- coupled scope, may not detect this problem, and the circuit MISSING DC BIAS CURRENT RETURN PATH may not fail until hours later. It is important to avoid this One of the most common application problems encountered is problem altogether. the failure to provide a dc return path for bias current in ac- +VS coupled op amp or in-amp circuits. -
Amplitude Modulation “AM” with Envelope Detector
Amplitude Modulation “AM” with Envelope Detector Large S/N limit m1< s(t) ≅ sin ωm t ≤ 1 Recei ved = y(t) = Ac [1 + m s( t)] cos ωc t + nc (t)cos ωc t + ns (t)s in ωct j ωct = Re {Y (t)e } slowly varying y, low-pass filtered (envelope) “overmodulation” = distortion (“undermodulation = wasted power) Lec 16b.6-1 2/2/01 T1 Amplitude Modulation “AM” with Envelope Detector Recei ved = y(t) = Ac [1 + m s( t)] cos ωc t + nc (t)cos ωc t + ns (t)s in ωct j ωct = Re {Y (t)e } slowly varying Im {Y (t)} Y(f ) 2W Y(t) ns(t) n(t) R e {Y(t) } f 0 0 fc A [1 + m s(t)] nc(t) N = kT c o 2 Lec 16b.6-2 2/2/01 T2 Amplitude Modulation “AM” with Envelope Detector Im {Y (t)} Y(f ) 2W Y(t) ns(t) n(t) R e {Y(t) } f 0 0 fc A [1 + m s(t)] nc(t) N = kT c o 2 Y(t) ≅ A [1 + m s(t)] + n (t) N c c envelope = detected signal + noise 2 2 2 2 2 Note: 4WNo = nc cos ωc t + ns sin ωc t = nc 222 Sout 222 2 Ac ms (t) ≅ Ac m s (t) nc (t) = Nout 4WNo Lec 16b.6-3 2/2/01 T3 Amplitude Modulation “AM” with Envelope Detector 222 Sout 222 2 Ac ms (t) ≅ Ac m s (t) nc (t) = Nout 4WNo 2 2 A 2 (1 + m s(t)) Sin ( c ) 2 ≅ where Sin = y signal(t) Nin 4WNo 22 ∆ SNi i 1m+ s (t) 11+ 2 Noi se figure FAM = = ≥ = 3 2 ⇒ FAM ≥ 3 2 SNo o 2m 22s 1 provided that Ac >> nc (large S/N limit) Lec 16b.6-4 2/2/01 T4 AM Performance (small S/N limit) Im {Y } φ (t) n A1c [ + m s(t)] n(t) ≅ Ac [1 + m s( t)] cos φn (t) φn (t) R e {}Y Y(t) ≅ n(t) + A cos φ (t) + A m s( t)cos φ (t) c n c n multiplicative noise! Want Sin Nin ≥ 10 for fully i ntel ligibl e AM ⇒ "AM threshold" ( i.e. -
Multi-Frequency Modulation and Control for DC/AC and AC/DC Resonant Converters
University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2018 Multi-Frequency Modulation and Control for DC/AC and AC/DC Resonant Converters Chongwen Zhao University of Tennessee, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Recommended Citation Zhao, Chongwen, "Multi-Frequency Modulation and Control for DC/AC and AC/DC Resonant Converters. " PhD diss., University of Tennessee, 2018. https://trace.tennessee.edu/utk_graddiss/5269 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Chongwen Zhao entitled "Multi-Frequency Modulation and Control for DC/AC and AC/DC Resonant Converters." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Electrical Engineering. Daniel Costinett, Major Professor We have read this dissertation and recommend its acceptance: Fred Wang, Leon M. Tolbert, D. Caleb Rucker Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Multi-Frequency Modulation and Control for DC/AC and AC/DC Resonant Converters A Dissertation Presented for the Doctor of Philosophy Degree University of Tennessee, Knoxville Chongwen Zhao December 2018 To my parents To Junting Guo ii Acknowledgement I would like to acknowledge the support and guidance from faculty members and staff at the University of Tennessee. -
ES442 Lab 6 Frequency Modulation and Demodulation
ES442 Lab#6 ES442 Lab 6 Frequency Modulation and Demodulation Objective 1. Build simple FM demodulator by using frequency discriminator 2. Build simple envelope detector for FM demodulation. 3. Using MATLAB m-file and simulink to implement FM modulation and demodulation. Part List 1uF capacitor (2); 10.0Kohm resistor, 1.0Kohm resistor, Power supply with +/-5V, Scope and frequency analyzer, FM signal Generator. Estimated Time About 90 minutes. Introduction Frequency modulation is a form of modulation, which represents information as variations in the instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct proportion to changes in the amplitude of an input signal. This is shown in Fig. 1. Figure 1, Frequency modulation. The FM-modulated signal has its instantaneous frequency that varies linearly with the amplitude of the message signal. Now we can get the FM-modulation by the following: where Kƒ is the sensitivity factor, and represents the frequency deviation rate as a result of message amplitude change. The instantaneous frequency is: Ver 2. 1 ES442 Lab#6 The maximum deviation of Fc (which represents the max. shift away from Fc in one direction) is: Note that The FM-modulation is implemented by controlling the instantaneous frequency of a voltage-controlled oscillator(VCO). The amplitude of the input signal controls the oscillation frequency of the VCO output signal. In the FM demodulation what we need to recover is the variation of the instantaneous frequency of the carrier, either above or below the center frequency. The detecting device must be constructed so that its output amplitude will vary linearly according to the instantaneous freq. -
Low-Power RFED Wake-Up Receiver Design for Low-Cost Wireless Sensor Network Applications
sensors Article Low-Power RFED Wake-Up Receiver Design for Low-Cost Wireless Sensor Network Applications David Galante-Sempere , Dailos Ramos-Valido, Sunil Lalchand Khemchandani and Javier del Pino * Institute for Applied Microelectronics (IUMA), University of Las Palmas de Gran Canaria (ULPGC), 35017 Las Palmas de Gran Canaria, Spain; [email protected] (D.G.-S.); [email protected] (D.R.-V.); [email protected] (S.L.K.) * Correspondence: [email protected] Received: 28 September 2020; Accepted: 6 November 2020; Published: 10 November 2020 Abstract: The development of wake-up receivers (WuR) has recently received a lot of interest from both academia and industry researchers, primarily because of their major impact on the improvement of the performance of wireless sensor networks (WSNs). In this paper, we present the development of three different radiofrequency envelope detection (RFED) based WuRs operating at the 868 MHz industrial, scientific and medical (ISM) band. These circuits can find application in densely populated WSNs, which are fundamental components of Internet-of-Things (IoT) or Internet-of-Everything (IoE) applications. The aim of this work is to provide circuits with high integrability and a low cost-per-node, so as to facilitate the implementation of sensor nodes in low-cost IoT applications. In order to demonstrate the feasibility of implementing a WuR with commercially available off-chip components, the design of an RFED WuR in a PCB mount is presented. The circuit is validated in a real scenario by testing the WuR in a system with a pattern recognizer (AS3933), an MCU (MSP430G2553 from TI), a transceiver (CC1101 from TI) and a T/R switch (ADG918).