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Design of Radio Frequency Circuits and Systems Emad Hegazi Professor, ECE Communication Circuits Research Group 1 Spring 2014 Spring 2014 RF Systems and Circuits

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How to Contact Me Office hour on Saturday 2 Spring 2014 Spring 2014 RF Systems and Circuits

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Cheating Policy It is very simple! If you cheat you get a BIG FAT ZERO 3 Spring 2014 Spring 2014 RF Systems and Circuits

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Lecture Room Rules Lecture starts ON time exactly If you find the door open, you may walk in without permission If closed, go away. Leave at any point in time without permission and without making up excuses Eating and drinking inside the lecture room is OK. Just don’t eat something crunchy or smelly. 4 Spring 2014 Spring 2014 RF Systems and Circuits

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Content Wireless Communication Review Basic signal analysis needs Noise in Narrow-band systems Distortion impairments Receiver architectures Transmitters Frequency generation RF Circuit blocks (LNAs, Mixers, VCOs, Pas) 5 Spring 2014 Spring 2014 RF Systems and Circuits

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References RF Microelectronics, 2 nd edition, Behzad Razavi, Prentice Hall 2012 Spring 2014 Spring 2014 Design of RF Circuits & Systems 6 Spring 2014 Spring 2014 RF Systems and Circuits

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Important CAD Tools CppSim (FreeWare) Octave as a Matlab clone (open source) Open source 45nm PDK announcements Spring 2014 Spring 2014 Design of RF Circuits & Systems 7 Spring 2014 Spring 2014 RF Systems and Circuits

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What We Cover 8 Spring 2014 Spring 2014 RF Systems and Circuits

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Introduction Course/Knowledge Requirement for being a Circuit Designer Basic Electronics Analog Circuit Design Advanced Analog Circuit Design RF Circuit Data ConvertersHigh Speed IOPower Management Spring 2014 Spring 2014 RF Systems and Circuits 9

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RF Circuits RF Circuits include Low Noise amplifiers, power amplifiers, Mixers, Phase locked loops Spring 2014 Spring 2014 RF Systems and Circuits 10

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Typical Transceiver Architecture Spring 2014 Spring 2014 RF Systems and Circuits 11

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Applications Using RF Transceivers Source: Many Applications, Several Frequency Ranges We need a Standard! Spring 2014 Spring 2014 RF Systems and Circuits 12

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Standards A Standard defines many specifications for the whole system such as: –Sensitivity –Desired BER and Modulation –Blocker distribution and modulation –Maximum transmitted power and power Mask –Range of communications –Frequency Range Source: notes/index.mvp/id/4010http://www.maxim-ic.com/app- notes/index.mvp/id/4010 Spring 2014 Spring 2014 RF Systems and Circuits 13

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Examples of Specifications Spring 2014 Spring 2014 RF Systems and Circuits 14

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Main Wireless Standards Market Name Data Rate RangeCost WiMax15Mb5km$8 3G14Mb10km$6 WiFi54Mb50-100m$4 Bluetooth700kb10m$1 Zigbee250kb30m$4 UWB400Mb5-10m$5 RFID1-200kb m$0.04 Spring 2014 Spring 2014 RF Systems and Circuits 15

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Why Digital Communication Allows information to be “packetized” (can compress information in time and efficiently send as packets through network) Analog modulation requires connections that are continuously available (Inefficient use of radio channel if there is “dead time” in information flow) Allows error correction to be achieved (less sensitivity to radio channel imperfections) Supports a wide variety of information content (voice, text and messages, video can all be represented as digital bit streams) Spring 2014 Spring 2014 RF Systems and Circuits 16

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System Engineering It is the art and science of putting things together. Combines multiple disciplines Should be agnostic to the implementation technology in concept Should take advantage of the technology specifics 17 Spring 2014 Spring 2014 RF Systems and Circuits

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Unrelated Historical Example Konrad Zuse ( ) who invented the world first computer First high level programming language Plankalkül Used vacuum state tubes and mechanical memory First to use binary to do arithmetic. org/wiki/Konrad_Zu sehttp://en.wikipedia. org/wiki/Konrad_Zu se Civil Engineer 18 Spring 2014 Spring 2014 RF Systems and Circuits

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Typical Digital Communication Transceiver In any digital transceiver, the I-Q components must be generated before down-converting the signal to baseband QPSK modulation QPSK de-modulation Spring 2014 Spring 2014 RF Systems and Circuits 19

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Quadrature Modulation The transmission is done using two orthogonal carriers carrying different information but occupying the same frequency band Demodulation must be done in the RX before converting the signal to baseband Spring 2014 Spring 2014 RF Systems and Circuits All transmitted and received signals are REAL. Complex notation is to simplify the analysis 20

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Narrow-band vs Wideband Narrow-band signals are signals for which the BW/fo <<1 Wideband signals are signals for which BW/fo>0.5 Ultra-wide band is a band allocated from 3-10 GHz targeted for: –High data rate transmission –Very low energy emission per Hz Pulsed - UWBOFDM-UWB Spring 2014 Spring 2014 RF Systems and Circuits 21

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Frequency Allocation Chart Spring 2014 Spring 2014 RF Systems and Circuits 22

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Frequency Allocation Chart Spring 2014 Spring 2014 RF Systems and Circuits 23

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RF IC Design Flow Initial Circuit Design Design Specification and Topology Initial Floor Plan Interconnect passive estimation Passive and Interconnect Simulations Redesign the circuit Layout Post-layout Simulation Optimize the performance Fabrication and Measurements Spring 2014 Spring 2014 RF Systems and Circuits 24

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PCB: Is it Important? Source: designs-inc Source: Inspection-and-Measurement.html Spring 2014 Spring 2014 RF Systems and Circuits 25

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Required Knowledge from A RF Designer Communications Analog basics Microwave basics PCB layout basics RF Circuit design: This Course Spring 2014 Spring 2014 RF Systems and Circuits 26

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Course Objective To teach the basic knowledge required for –RF circuit analysis and design using CMOS technology –Transceiver architectures and their specifications –Simulating RF Circuits Specifications Spring 2014 Spring 2014 RF Systems and Circuits 27

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Passives Capacitors Spiral Inductor Main Specifications –Quality Factor –Loss Mechanism Impedance Transformations 28 Spring 2014 Spring 2014 RF Systems and Circuits

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Transceiver Architectures Which architecture should we select? Spring 2014 Spring 2014 RF Systems and Circuits 29

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Basic Building Blocks Low Noise Amplifier Mixer Voltage Controlled Oscillator Power Amplifier AM/FM Modulators PLL (Basic) Spring 2014 Spring 2014 RF Systems and Circuits 30

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31 Wireless Communication Transmitting voice and data using electromagnetic waves in open space Electromagnetic waves Travel at speed of light (c = 3x10 8 m/s) Has a frequency (f) and wavelength ( ) »c = f x Higher frequency means higher energy photons The higher the energy photon the more penetrating the radiation is Spring 2014 Spring 2014 RF Systems and Circuits

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Electromagnetic Spectrum 32 Spring 2014 Spring 2014 RF Systems and Circuits

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33 Wavelength of Some Technologies GSM Phones: –frequency ~= 900 Mhz –wavelength ~= 33cm PCS Phones –frequency ~= 1.8 Ghz –wavelength ~= 17.5 cm Bluetooth: –frequency ~= 2.4Gz –wavelength ~= 12.5cm Spring 2014 Spring 2014 RF Systems and Circuits

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34 Types of Communication Spring 2014 Spring 2014 RF Systems and Circuits

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35 Duplex Communication - FDD Forward Channel and Reverse Channel use different frequency bands Spring 2014 Spring 2014 RF Systems and Circuits

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36 Basics - Propagation Waves behave more like light at higher frequencies Difficulty in passing obstacles More direct paths They behave more like radio at lower frequencies Can pass obstacles Spring 2014 Spring 2014 RF Systems and Circuits

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37 What is Decibel (dB) What is dB (decibel): –A logarithmic unit that is used to describe a ratio. Let say we have two values P1 and P2. The difference (ratio) between them can be expressed in dB and is computed as follows: –10 log (P1/P2) dB Example: transmit power P1 = 100W, received power P2 = 1 W »The difference is 10log(100/1) = 20dB. Spring 2014 Spring 2014 RF Systems and Circuits

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38 dB dB unit can describe very big ratios with numbers of modest size. See some examples: –Tx power = 100W, Received power = 1W »Tx power is 100 times of received power »Difference is 20dB –Tx power = 100W, Received power = 1mW »Tx power is 100,000 times of received power »Difference is 50dB –Tx power = 1000W, Received power = 1mW »Tx power is million times of received power »Difference is 60dB Spring 2014 Spring 2014 RF Systems and Circuits

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39 dBm/ dBW For power differences, dBm is used to denote a power level with respect to 1mW as the reference power level. Let say Tx power of a system is 100W. Question: What is the Tx power in unit of dBm? Answer: –Tx_power(dBm) = 10log(100W/1mW) = 10log(100W/0.001W) = 10log(100,0000) = 50dBm For power differences, dBW is used to denote a power level with respect to 1W as the reference power level. Let say Tx power of a system is 100W. Question: What is the Tx power in unit of dBW? Answer: –Tx_power(dBW) = 10log(100W/1W) = 10log(100) = 20dBW. Spring 2014 Spring 2014 RF Systems and Circuits

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Narrow Band vs. Wideband 40 Spring 2014 Spring 2014 RF Systems and Circuits

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System Theory Implications Linear Nonlinear Time Invariant Time Varying Memory having Memoryless We will be focusing on weakly nonlinear Time Invariant/varying systems 41 Spring 2014 Spring 2014 RF Systems and Circuits

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Linearity The system gives a linearly proportionate responses to different stimuli If Y(t) = f [x(t)] then f [a 1.(x 1 (t) + a 2. x 2 (t)]=a 1 Y 1 (t)+ a 2. Y 2 (t) Can be fully described by its impulse response Can be characterized by their Laplace and Fourier transforms 42 Spring 2014 Spring 2014 RF Systems and Circuits

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Real or Imaginary? Physical signals are all real. Complex representation is a way to simplify signal processing of arrow band RF signals 43 Re {Z} Im {Z} Re {Z}Im {Z} Spring 2014 Spring 2014 RF Systems and Circuits

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THE WIRELESS ENVIRONMENT 44 Spring 2014 Spring 2014 RF Systems and Circuits

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Functions of the Rx Limit bandwidth to the desired service band (selectivity) Knock-down interference(linearity) Provide gain to weak signals. Bring signal to baseband (Time Variance) Provide highest SNR 45 Spring 2014 Spring 2014 RF Systems and Circuits

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Performance Indicators BER is the main performance indicator for a given modulation type. Higher SNR means more ability to detect the signal 46 Spring 2014 Spring 2014 RF Systems and Circuits

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Receiver SNR 47 Impedance Matching SNR max SNR min Spring 2014 Spring 2014 RF Systems and Circuits

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Sensitivity Adjacent Channel Interference Co-Channel Interference Desired Channel Adjacent Channel MHz GMSK spectrum 48 Spring 2014 Spring 2014 RF Systems and Circuits

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Sensitivity Receiver Thermal Noise Receiver Added Noise Desired Signal 49 Minimum detectable signal given the type of modulation and BER required Spring 2014 Spring 2014 RF Systems and Circuits

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Sensitivity ERP = +50 dBm Power to Antenna: +40 dBm TX. Antenna Gain: +10 dB Frequency: 10 GHz Bandwidth: 100MHz Rcvr. Antenna Gain: +60 dB Transmitter: ERP Path Losses Rcvr. Ant. Gain Power to Receiver Receiver: Noise 290K Noise in 100 MHz BW Receiver N.F. Total noise on channel Margin: 4 dB + 50 dBm -190 dB 60 dB -80 dBm dBm/Hz + 80 dB +10 dB -84 dBm Path Losses: 200 dB + 50 What the Rx adds to ambient noise SNR = +4 dB Spring 2014 Spring 2014 RF Systems and Circuits

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Selectivity Ch 1 Ch 2 Ch n Ch 3 RF Filter freq f RF Ch 1 Ch 2 Ch n Ch 3 freq f IF IF Filter freq f LO 51 Spring 2014 Spring 2014 RF Systems and Circuits

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Selectivity RF Filter IF Filter IF filter rejection at the adjacent channel LO spurious in IF bandwidth Phase noise of LO Receiver Added Noise Receiver Thermal Noise 52 Spring 2014 Spring 2014 RF Systems and Circuits

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Nonlinear System Representation Fourier transform is not applicable so F(.) means function Taylor series is suited for representing nonlinear memory-less systems. Assume a scenario where you have being the desired signal (typically weak) and are two interfering signals (typically strong) 53 Spring 2014 Spring 2014 RF Systems and Circuits

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Nonlinear System Representation Here is the output of the system: 54 Spring 2014 Spring 2014 RF Systems and Circuits

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Nonlinearity Artifacts Assuming a 3-tone input Depending on the relative weights of the inputs, different characteristics can be evaluated 55 Spring 2014 Spring 2014 RF Systems and Circuits

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Gain Compression In the presence of a blocker Gain is reduced due to nonlinearity This impacts the weak desired Signal. Typically specified by the 1 dB Compression point 56 Spring 2014 Spring 2014 RF Systems and Circuits

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1 dB Compression Point 57 Spring 2014 Spring 2014 RF Systems and Circuits

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Inter-modulation Nonlinearity generates product terms 58 Spring 2014 Spring 2014 RF Systems and Circuits

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Some of the Ugly Results Bear in mind that RF circuits are typically frequency-selective Bad news for wideband receivers! 59 Spring 2014 Spring 2014 RF Systems and Circuits

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Inter-modulation Products The product of importance depends largely on receiver architecture and frequency plan 60 Spring 2014 Spring 2014 RF Systems and Circuits

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Quantifying Inter- modulation Distortion: Intercept Points 61 Spring 2014 Spring 2014 RF Systems and Circuits

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3 rd Order Distrotion 62 Spring 2014 Spring 2014 RF Systems and Circuits

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IP3 63 PP P=2X X X X= P/2 Spring 2014 Spring 2014 RF Systems and Circuits

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Two Tone Test 64 Spring 2014 Spring 2014 RF Systems and Circuits

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Calculating IP3 65 Spring 2014 Spring 2014 RF Systems and Circuits

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IP2 Distortion grows faster than fundamental. In the case of 2 nd order distortion, it grows 2x faster as input power is increased. 67 PP Spring 2014 Spring 2014 RF Systems and Circuits

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IP2 68 Spring 2014 Spring 2014 RF Systems and Circuits

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Blocking/Desesitization 69 Spring 2014 Spring 2014 RF Systems and Circuits

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Nonlinearity in Cscaded Systems 70 Spring 2014 Spring 2014 RF Systems and Circuits

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Example: Two-stage IP3 71 Spring 2014 Spring 2014 RF Systems and Circuits

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Example: Two-stage IP3 72 Spring 2014 Spring 2014 RF Systems and Circuits Note that 3 is much more Impactful than 3

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IP3 of a Cascaded Rx 73 Spring 2014 Spring 2014 RF Systems and Circuits

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IPn 74 Spring 2014 Spring 2014 RF Systems and Circuits

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Noise in Receivers Receiver “noise level” directly limits sensitivity Receiver sensitivity = minimum input power that the receiver can detect Noise figure of cascaded stages –Noise figure of RF receivers from antenna to ADC output –Noise figure of passive networks –Noise figure of ADCs Patrick Yue Spring 2014 Spring 2014 RF Systems and Circuits 75

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Receiver Noise Transducer noise is boosted by the input- referred noise of the receiver. Antenna impedance is set to 50 Two input noise sources are correlated. 76 Spring 2014 Spring 2014 RF Systems and Circuits

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Conjugate Matching For maximum power transfer Antenna Receiver 77 Spring 2014 Spring 2014 RF Systems and Circuits

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Noise Figure of Two-Port Network Noise Figure= 10 * log (Noise Factor) [dB] Noise Temperature = T n = T ref * (F at T n – 1) [K] (T ref = 290 K) => F at T n = 1 + T n / T ref Patrick Yue Spring 2014 Spring 2014 RF Systems and Circuits 78

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Noise in Two-Port Networks The noise of a two-port network can be modeled by a series noise voltage source and a shunt current source at the input of a noiseless network. (Input-Referred Noise Representation of Two-Port Network) With both voltage and current noise sources present, the total input-referred noise becomes independent of the source impedance (Rs) –For Rs= 0, I n has not effect and all the noise is represented by V n –For Rs= infinity, V n has not effect and all the noise is represented by I n –For other Rs values, both V n and I n contribute the total input-referred noise Patrick Yue Spring 2014 Spring 2014 RF Systems and Circuits 79

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Noise Figure of Cascaded Stages Patrick Yue Spring 2014 Spring 2014 RF Systems and Circuits 80

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Cascaded Noise Figure In a line-up of receiver stages, use Friis equation G i is the power gain Says that the noise factor ‘F’ is more influenced by earlier stages Spring 2014 Spring 2014 RF Systems and Circuits 81

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Noise Factor of a Passive Network Spring 2014 Spring 2014 RF Systems and Circuits 82

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Noise Figure Calculation of BPF Followed by LNA Spring 2014 Spring 2014 RF Systems and Circuits 83

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LTI Systems 84 Spring 2014 Spring 2014 RF Systems and Circuits

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Frequency Response of LTI systems 85 Spring 2014 Spring 2014 RF Systems and Circuits

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