# Ppt on varactor diode modulator

##### FREQUENCY MODULATION(FM )

Carson’s Rule. Sketch the frequency spectrum for (a), with actual amplitudes. Example 3.4 For an FM modulator with a modulation index m=1, a modulating signal Vm(t)=Vm sin(2π1000t), and an unmodulated carrier Vc(t) = 10sin(2π500kt), determine/deviation Disadvantage: the carrier frequency tends to drift and must be stabilized. example circuit: Reactance modulator Varactor diode Generation of FM (cont’d) ii) Indirect method: Frequency-up conversion. Two ways: Heterodyne method Multiplication method One most popular/

##### ANGLE MODULATION CHAPTER 3. ANGLE MODULATION Part 1 Introduction.

oscillation frequency has linear dependence on applied voltage. ii) Advantage: large frequency deviation iii) Disadvantage: the carrier frequency tends to drift and must be stabilized. iv) example circuit: i) Reactance modulator ii) Varactor diode Generation of FM (cont’d) ii) Indirect method: i. Frequency-up conversion. ii. Two ways: a. Heterodyne method b. Multiplication method iii. One most popular indirect method is the/

##### ANGLE MODULATION CHAPTER 3. ANGLE MODULATION Part 1 Introduction.

oscillation frequency has linear dependence on applied voltage. ii) Advantage: large frequency deviation iii) Disadvantage: the carrier frequency tends to drift and must be stabilized. iv) example circuit: i) Reactance modulator ii) Varactor diode Generation of FM (cont’d) ii) Indirect method: i. Frequency-up conversion. ii. Two ways: a. Heterodyne method b. Multiplication method iii. One most popular indirect method is the/

##### 1 Chapter 2 Continuous-Wave Modulation 2.1 Introduction.

) 9 Costas Receiver I-channel and Q-channel are coupled together to form a negative feedback system to maintain synchronization The phase control signal ceases with modulation. (multiplier + very narrow band LF) 10 Quadrature-Carrier Multiplexing (or QAM) Two DSB-SC signals occupy the same channel bandwidth, where pilot signal/ universal curve of Figure 2.26 overestimates it by 20 percent. 32 Generation of FM signals Frequency Multiplier Varactor diode VCO FM modulator 32-1 Crosby Direct FM Transmitter 32-2

##### HARP-B Local Oscillator

although a buffered version of the Gunn bias voltage is available from the Gunn Driver (#8c) 2. Multiplier o Varactor-diode based frequency tripler o Input power tuning is mechanical (backshort adjustment via o Output power tuning is mechanical (backshort/ waveguide controls signal attenuation. o Bias drive current should switch to new setting very rapidly o Available status: Modulator bias current 6. YIG oscillator o Computer controlled frequency synthesizer. o YIG means Yttrium-Iron-Garnet resonator o /

##### Principles of Electronic Communication Systems. Chapter 6 FM Circuits.

the dielectric and, therefore the amount of capacitance. All diodes exhibit variable capacitance. Varactors are designed to optimize this characteristic. 6-1: Frequency Modulators Figure 6-2: Schematic symbols of a varactor diode. 6-1: Frequency Modulators Figure 6-4: A direct-frequency-modulated carrier oscillator using a varactor diode. 6-1: Frequency Modulators Varactor Modulator In Figure 6-4, the capacitance of varactor diode D 1 and L 1 form the parallel tuned/

##### Principles of Electronic Communication Systems

the dielectric and, therefore the amount of capacitance. All diodes exhibit variable capacitance. Varactors are designed to optimize this characteristic. 6-1: Frequency Modulators Figure 6-2: Schematic symbols of a varactor diode. 6-1: Frequency Modulators Figure 6-4: A direct-frequency-modulated carrier oscillator using a varactor diode. 6-1: Frequency Modulators Varactor Modulator In Figure 6-4, the capacitance of varactor diode D1 and L1 form the parallel tuned circuit of/

##### McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All rights reserved. Principles of Electronic Communication Systems FM Circuits.

LC oscillators.  The frequency of a crystal oscillator can be varied by changing the value of capacitance in series or parallel with the crystal.  By making the series capacitance a varactor diode, frequency modulation can be achieved.  The modulating signal is applied to the varactor diode which changes the oscillator frequency. McGraw-Hill © 2008 The McGraw-Hill Companies, Inc. All rights reserved. 6-1: Frequency/

##### Principles of Electronic Communication Systems

the dielectric material. The width of the depletion layer determines the width of the dielectric and, therefore the amount of capacitance. All diodes exhibit variable capacitance. Varactors are designed to optimize this characteristic. Varactor Diode Schematic Symbol Varactor Modulator Circuit Varactor Modulator The capacitance of varactor diode D1 and L1 form the parallel tuned circuit of the oscillator. The value of C1 is made very large so its reactance is/

##### © 2008 The McGraw-Hill Companies 1 Principles of Electronic Communication Systems Third Edition Louis E. Frenzel, Jr.

capacitance.  Schottky diodes are widely used in balanced modulators and mixers.  They are also used as fast switches at microwave frequencies. © 2008 The McGraw-Hill Companies 62 16-4: Microwave Semiconductor Diodes Figure 16-36: Hot carrier or Schottky diode. © 2008 The McGraw-Hill Companies 63 16-4: Microwave Semiconductor Diodes Frequency-Multiplier Diodes  Microwave diodes designed primarily for frequency- multiplier service include:  Varactor diodes  Step-recovery diodes © 2008 The/

##### Principles of Electronic Communication Systems

sometimes referred to as hot carrier diodes. Like the point-contact diode, the Schottky diode is extremely small and therefore has a tiny junction capacitance. Schottky diodes are widely used in balanced modulators and mixers. They are also used as fast switches at microwave frequencies. Schottky Diode Frequency-Multiplier Diodes Microwave diodes designed primarily for frequency-multiplier service include: Varactor diodes Step-recovery diodes Varactor Diodes A varactor diode is basically a voltage variable/

##### LECTURE ON AM/FM TRANSMITTER

Methods Punjab Edusat Society DIRECT FM In direct FM generation the frequency of the carrier is changed directly in proportion with the modulating signal amplitude. Types of Direct FM Reactance modulator Varactor diode modulator Punjab Edusat Society DIRECT FM These methods use a varactor diode or a reactance transistor for presenting a variable reactance across the frequency determining circuit of an oscillator. Punjab Edusat Society DIRECT FM/

##### Indirect optical control of microwave circuits and antennas Amit S. Nagra ECE Dept. University of California Santa Barbara.

OVC Key features of the Optically Variable Capacitor (OVC) PV array controls reverse bias voltage across a varactor diode Varactor junction capacitance can be controlled optically No external bias required RF block resistor keeps PV array out of/ of the Transient Response of the Monolithic OVC Pulse Generator Laser Driver Semiconductor Laser Diode DUT Digitizing Oscilloscope Active Probes Modulated Light Output Voltage Intensity modulated light (square wave) used as input to the OVC Rise and fall times /

##### Government Engineering College, Godhra SUBJECT : Audio and Video System GEC GODHRA.

Methods of FM Generation DIRECT FM GEC GODHRA In direct FM generation the frequency of the carrier is changed directly in proportion with the modulating signal amplitude. Types of Direct FM Reactance modulator Varactor diode modulator DIRECT FM These methods use a varactor diode or a reactance transistor for presenting a variable reactance across the frequency determining circuit of an oscillator. GEC GODHRA DIRECT FM GEC GODHRA/

##### Communication Theory (EC 2252)

. (1) Direct FM: Carrier frequency is directly varied by the message through voltage-controlled oscillator. Eg: Varactor diode modulator. (2) Indirect FM: Generate NBFM first, then NBFM is frequency multiplied for targeted Δf. Eg: Armstrong modulator FM Varactor Modulator The Operation of the Varactor Modulator The info signal is applied to the base of the input transistor and appears amplified and inverted at the collector. This low freq/

##### 1 Communication Theory (EC 2252) Prof.J.B.Bhattacharjee K.Senthil Kumar ECE Department Rajalakshmi Engineering College www.Vidyarthiplus.com.

.   (1) Direct FM: Carrier frequency is directly varied by the message through voltage-controlled oscillator. Eg: Varactor diode modulator.   (2) Indirect FM: Generate NBFM first, then NBFM is frequency multiplied for targeted Δf. Eg: Armstrong modulator 64 FM FM Varactor Modulator The Operation of the Varactor Modulator   The info signal is applied to the base of the input transistor and appears amplified and inverted at the collector.   This/

##### For further information, see the Courseware Product License Agreement.

of Vcontrol should be stable. Requirement 4: The circuit has to be properly shielded from electromagnetic interference from other modules. Requirement 5: Use low noise components in the construction of the oscillator, e.g. small resistance values, low/ Symposium, 1985. T. Lee, A. Hajimiri, “The design of low noise oscillators”, Kluwer, 1999. More on Varactor Extra The varactor diode is basically a PN junction optimized for its linear junction capacitance. It is always operated in the reverse-biased mode to/

##### Voltage Controlled Oscillators 1 High Speed Electronic Circuits April 27, 2016 By:Abanoub Mamdouh Andrew FahimRamez Mamdouh Michael SamirMounir BaselMohamed.

region width Increasing the voltage 6 Varactors 7 8 Varactor Diodes types Different varactor diodes, have different values and parameters of PN junction. Abrupt varactors and hyper-abrupt varactors have different properties as detailed below. Different doping profiles could be applied to the PN junction of the varactor diode, to achieve certain C-V relations. Varactor diode Abrupt varactors Hyperabrupt varactors Varactors 9 Abrupt Diodes For an abrupt varactor diode the doping concentration is held constant/

##### Heng Chan; Mohawk College

Metal Electrode Applications: detectors, mixers, and switches. Heng Chan; Mohawk College Varactor Diode Varactors operate under reverse-bias conditions. Cj Co Circuit Symbol V Junction Capacitance Characteristic Varactors operate under reverse-bias conditions. The junction capacitance is: where Vb =/ Broadcast-quality composite video or picturephone Wideband data IF carrier is typically 70 MHz Low-index frequency modulation is used Common microwave frequencies used: 2-, 4-, 6-, 12-, and 14-GHz bands. Heng/

##### R. F. Systems EE731 H. Chan; Mohawk College.

Applications: detectors, mixers, and switches. H. Chan; Mohawk College Junction Capacitance Characteristic Varactor Diode Cj Co Circuit Symbol V Junction Capacitance Characteristic Varactors operate under reverse-bias conditions. The junction capacitance is: where Vb = barrier potential /= period of oscillation H. Chan; Mohawk College Reflex Klystron Operation Electron beam is velocity modulated when passing though gridded gap of the cavity. Repeller decelerates and turns back electrons thus causing/

##### Microwave Engineering/Active Microwave Devices 9-13 September 2006 1 Semiconductor Microwave Devices Major Applications Substrate Material Frequency Limitation.

Frequency mixing Voltage Controlled Oscillator Harmonic generation Voltage tuned filter Switching Frequency conversion Modulation Harmonic generation Limiting Parametric amplificationDetection A microwave diode is much more than just a two-element device which has limited /RF efficiency of 1 to 4%. Microwave Engineering/Active Microwave Devices 9-13 September 2006 19 Varactor Tuned Gunn Oscillators Circuits Microwave Engineering/Active Microwave Devices 9-13 September 2006 20 Microwave Engineering/

##### 1 Microwave Semiconductor Devices Major Applications Substrate Material Frequency Limitation Device Transmitters AmplifiersSi, GaAs, InP< 300 GHzIMPATT.

multiplication Frequency mixing Voltage Controlled Oscillator Harmonic generation Voltage tuned filter Switching Frequency conversion Modulation Harmonic generation Limiting Parametric amplificationDetection A microwave diode is much more than just a two-element device which has limited capabilities./ power combiner. Gunn oscillators exhibit very low dc-to-RF efficiency of 1 to 4%. 19 Varactor Tuned Gunn Oscillators Circuits 20 21 IMPATT Devices and Circuits IMPact Ionization Transit Time IMPATT devices can /

##### 九十八學年第一學期 科目：電子學（一） 班級：電機二甲、電機二乙 授課教師：章國揚 林正平 九十八學年第一學期 科目：電子學（一） 班級：電機二甲、電機二乙 授課教師：章國揚 林正平.

modulation, and switching. In reverse bias it exhibits a nearly constant capacitance. Other Diode Types The step-recovery diode is also used for fast switching applications. This is achieved by reduced doping at the junction. Other Diode Types The tunnel diode/ There are other diode types used for specific RF purposes such as varactor diodes (variable capacitance), Schottky diodes (high speed switching), and PIN diodes (microwave attenuation and switching). Summary   Light emitting diodes (LED) emit either/

##### MVE MURI 99 Kick-off MeetingR. Barker, Technical Monitor Started 1 May 99 October 1999 High Power Millimeter Wave Grid Array Sources* A novel, broadband.

savings in size, weight and cost as compared to conventional coupled-cavity TWT sources. Eventual systems could also employ the Millimeter Wave Power Module (MMPM), with an 18-40 GHz bandwidth, currently under development. * This work has been supported by the US AFOSR under / Frequency doubler grid arrays using Schottky varactors fabricated by Martin- Marietta have been tested. C min = 15 fF, C max = 60 fF resulting in C max /C min = 4 R s = R diode + R strip = 6 Ω MVE MURI 99 Kick-off MeetingR. Barker, /

##### MURI Teleconference 5/28/04 Electrical Engineering Department University of California, Los Angeles Professor Tatsuo Itoh.

 Biasing DC magnetic field  NOT practical  Waveguide configuration R. E. Horn, et. al, “Electronic modulated beam steerable silicon waveguide array antenna,” IEEE Tran. Microwave Theory Tech. H. Maheri, et. al, “Experimental /the varactor diode’s voltages  Series and Shunt Varactors  Fairly constant characteristic impedance  Additional degree of freedom for wider scanning range  Reverse biasing to Varactors  Anodes of varactors : GND  Cathodes of varactors: Biasing  Series and Shunt Varactors /

##### Amateur Extra Licensing Class Presented by W5YI Arlington, Texas Components in Your New Rig.

ELEMENT 4 Groupings Rules & Regs Skywaves & Contesting Outer Space Comms Visuals & Video Modes Digital Excitement with Computers & Radios Modulate Your Transmitters Amps & Power Supplies Receivers with Great Filters Amateur Radio Extra Class Element 4 Course Presentation  ELEMENT 4 Groupings Oscillate/ voltage applied to its terminals varies? A.Tunnel diode B.Varactor diode C.Silicon-controlled rectifier D.Zener diode E6B06 In Figure E6-3, what is the schematic symbol for a varactor diode? A.8 B.6 C.2 D.1 /

##### Chapter 16 Other Two-Terminal Devices

with no reverse bias applied n = 1/2 for alloy and 1/3 for diffused junctions VT = maximum reverse bias voltage VR = applied reverse bias voltage 5 Varactor Diode Applications FM modulator Automatic-frequency-control devices Adjustable bandpass filters Parametric amplifiers 6 Power Diodes Power diodes used in high-power and high-temperature applications, such as power rectifier circuits, must be rated for power Power/

##### Oscillators Communication Circuits Prof. M. Kamarei.

noise ●Supply and Common-Mode Rejection –Single-ended forms are more sensitive –Noise may coupled to VCO control line and modulates carrier ●Output Signal Purity –Jitter –Phase Noise M. Kamarei, Spring 2009 Oscillators67 Mathematical Model of VCOs ●Consider two waveforms/, though, the n side of the diode is “dirty” due to the large well capacitance and substrate connection resistance. M. Kamarei, Spring 2009 Oscillators75 Varactor Tuned Diff Osc. ●By reversing the diode connection, the “dirty” side of the/

##### John R. Vig Consultant. Most of this Tutorial was prepared while the author was employed by the US Army Communications-Electronics Research, Development.

signal) -- Doppler shifted signal from target Phase noise of the local oscillator modulates (decorrelates) the clutter signal, generates higher frequency clutter components, and thereby degrades/in the resonator package and the oscillator circuitry. Induced ac voltages can affect varactors, AGC circuits and power supplies. Typical frequency change of a "good" / atomic energy levels are populated by optical pumping with a laser diode. This method provides superior utilization of Cs atoms, and provides/

##### Quartz Crystal Resonators and Oscillators

signal) --› Doppler shifted signal from target Phase noise of the local oscillator modulates (decorrelates) the clutter signal, generates higher frequency clutter components, and thereby degrades/materials in the resonator package and the oscillator circuitry. Induced ac voltages can affect varactors, AGC circuits and power supplies. Typical frequency change of a "good" quartz/atomic energy levels are populated by optical pumping with a laser diode. This method provides superior utilization of Cs atoms, and /

##### SUBELEMENT E7 PRACTICAL CIRCUITS [8 Exam Questions - 8 Groups] Practical Circuits1.

used as a stable reference voltage in a linear voltage regulator? A. A Zener diode B. A tunnel diode C. An SCR D. A varactor diode 117Practical Circuits E7D03 What device is typically used as a stable reference voltage in a linear voltage/C. It provides improved resolution of low-frequency signals within a comparable time period D. It can directly measure the modulation index of an FM transmitter 200Practical Circuits E7G Active filters and op-amps active audio filters; characteristics; basic circuit design;/

##### Amateur Extra License Class

ability to amplify. The following slides describe only some of the devices & techniques used. Amplifiers VHF, UHF, and Microwave Amplifiers. Klystrons. Velocity modulation. Amplifiers VHF, UHF, and Microwave Amplifiers. Parametric amplifiers. Invented by amateur radio operators. Uses variable reactance (varactor diode) to “pump” input signal. Used for very low noise receive pre-amplifiers at microwave frequencies & above. Amplifiers VHF, UHF, and Microwave Amplifiers/

##### John R. Vig US Army Communications-Electronics Research, Development & Engineering Center Fort Monmouth, NJ, USA Approved for public release.

signal) --› Doppler shifted signal from target Phase noise of the local oscillator modulates (decorrelates) the clutter signal, generates higher frequency clutter components, and thereby degrades/in the resonator package and the oscillator circuitry. Induced ac voltages can affect varactors, AGC circuits and power supplies. Typical frequency change of a "good" / atomic energy levels are populated by optical pumping with a laser diode. This method provides superior utilization of Cs atoms, and provides/

##### John R. Vig US Army Communications-Electronics Research, Development & Engineering Center Fort Monmouth, NJ, USA Approved for public release.

signal) --› Doppler shifted signal from target Phase noise of the local oscillator modulates (decorrelates) the clutter signal, generates higher frequency clutter components, and thereby degrades/in the resonator package and the oscillator circuitry. Induced ac voltages can affect varactors, AGC circuits and power supplies. Typical frequency change of a "good" / atomic energy levels are populated by optical pumping with a laser diode. This method provides superior utilization of Cs atoms, and provides/

##### Amateur Extra License Class

not rectify. When properly biased, exhibits negative resistance. Once used for oscillators & amplifiers at microwave frequencies. Semiconductor Devices Diodes Varactor Diodes (VariCap). Operates with reverse bias. Varying voltage varies junction capacitance. A few picofarads to >100 pF. Used for variable-frequency oscillators & for FM modulators. Semiconductor Devices Diodes PIN Diodes. 3rd layer of undoped (intrinsic) material. Forward resistance varies with forward bias voltage. More voltage  lower/

##### PN Junction Devices. Electromagnetic Waves  Induction  A changing magnetic field causes an induced electric field  A changing electric field causes.

300 m  Antenna should be ¼ wavelength for useful transfer of information The Electromagnetic Spectrum Modulation  Amplitude Modulation (AM) Amplitude is periodically changed. Information can be sent at a relatively slow rate, /Diodes  Rectifier Diode  Used in power supplies  Signal Diode  Used in switches, detectors, mixers, etc.  Zener Diode  Voltage regulation – operated reverse bias in the avalanche region  Reference Diode  Used like zener for voltage regulation Types of DiodesVaractor Diode/

##### Amateur Extra License Class Chapter 5 Components and Building Blocks.

. When properly biased, exhibits negative resistance. OBSOLETE -- Once used for oscillators & amplifiers at microwave frequencies. Semiconductor Devices Diodes Varactor Diodes (VariCap). Operates with reverse bias. Varying voltage varies junction capacitance. A few picofarads to >100 pF. Used for variable-frequency oscillators & for FM modulators. Semiconductor Devices Diodes PIN Diodes. 3 rd layer of undoped (intrinsic) material. Forward resistance varies with forward bias voltage. More voltage  lower/

##### SUBELEMENT E6 CIRCUIT COMPONENTS [6 Exam Questions - 6 Groups] Circuit Components1.

Varactor diode B. Tunnel diode C. Silicon-controlled rectifier D. Zener diode 46Circuit Components E6B04 What type of semiconductor device is designed for use as a voltage-controlled capacitor? A. Varactor diode B. Tunnel diode C. Silicon-controlled rectifier D. Zener diode 47Circuit Components E6B05 What characteristic of a PIN diode/optocoupler? A. A lens and a photomultiplier B. A frequency modulated helium-neon laser C. An amplitude modulated helium-neon laser D. An LED and a phototransistor 157Circuit /

##### Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. MALVINO & BATES SEVENTH EDITION Electronic PRINCIPLES.

diode Varactor Other diodes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Zener diode/diode voltage regulator This circuit will regulate when the Thevenin voltage facing the zener diode/diode/ diode /diode/diodes/diode/diode A special diode/diodes eliminate tails at high frequencies. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Varactor diode/diode/diode applications Laser: CD players, communications Step-recovery: Frequency/

##### Chapter 3 Problems ECET 214 Prof. Park NJIT.

an advantage of a synchronous detection? a. Low distortion b. Eliminate diagonal clipping c. Greater ability to follow fast-modulated signals d. Ability to produce gain Problem 2 The mixer is often referred to as: a. RF amplifier b. oscillator generator c. second detector d. first detector Problem 3 Varactor diodes are used for tuning by: a. capacitance adjustment through a reverse bias/

##### INSTRUCTOR SHRI A.V.PADHYA DURATION 08 WEEK Week No. Lesson No. Name of lessonRemark 1 1Electrical safety and artificial respiration. 2General electrical.

specifications 20Special device – UJT, FET, SCR & ICs. 21Rectifiers – Half wave, Full wave & Bridge. SKILL FOR TRAINEE IN MODULE - 3 WEEK NO SKIL NO. DESCRIPTION 01 Familiar with Electrical safety and artificial respiration, General hand tools, Fundamental units and /.C DIODE TYPES RACTIFIER DIODE ZENER DIODE LIGHT EMITTING DIODE (L.E.D) DETECTOR DIODE STEEK DIODE VARACTOR DIODE LIQUID CRYSTAL DIODE (L.C.D) PHOTO DIODE TUNNEL DIODE CONSTRUCTION DIODE IS A CONNECTION OF P & N TYPE SEMI CONDUCTORS. DIODE HAS /

##### MVE MURI 99 Kick-off Meeting R. Barker, Technical Monitor Started 1 May 99 October 1999 UC Davis Millimeter Wave Vacuum/ Solid-State Hybrid Technologies.

1999 Nonlinear Delay Lines The line has a Bragg cutoff frequency given by: The equivalent circuit of a varactor diode periodically loaded Coplanar Waveguide (CPW) line is shown below: MVE MURI 99 Kick-off Meeting R. Barker/center spacing, 2  m gate aperture diameter, 2  m tip height. BoBo Microwave Circuitry Collector Gated Field Emission Cathode Modulated Laser Beam Anode  Field emission does not require heating filament.  Optical gating avoids capacitive effect associated with electrical gating./

##### MOS-AK, San Francisco, Dec. 13, 2008 1 The HiSIM Family of Compact-Models for Integrated Devices H. J. Mattausch, N. Sadachika, M. Miyake, H. Kikuchihara,

Silicon-On-Insulator (SOI) MOSFET 5.Double-Gate MOSFET 6.MOS Varactor 7.High-Voltage Devices High-Voltage MOSFET Insulated Gate Bipolar Transistor (/ Channel: impurity pile-up pocket implant Poly-Depletion: Quantum-Mechanical: Channel-Length Modulation: Narrow-Channel: Temperature Dependency: thermal voltage bandgap n i phonon scattering maximum velocity/ Currents: substrate current gate current GIDL current Source/Drain Resistances: Junction Diode: currents capacitances MOS-AK, San Francisco, Dec. 13, 2008 9/

##### 5.1 Introduction 5.2 Equilibrium condition 5.2.1 Contact potential

diffusion length, the excess carrier injection for large forward currents can increase the conductivity of the region significantly This type of conductivity modulation, which reduces the forward resistance R, can be very useful for high-current devices On the other hand, a short, / Time Variation of Stored Charges 5.5.2 Reverse Recovery Transient 5.5.3 Switching Diodes 5.5.4 Capacitance of p-n Junctions 5.5.5 The varactor Diode 5.6 Deviations from the Simple Theory 5.6.1 Effect of Contact Potential on /

##### Chapter 4 Components & Circuits (Part 2)

capacitance allows operation at VHF & UHF. Lower forward voltage drop. Active Components Semiconductor Components Diodes & Rectifiers Diode Types Varactor Diodes (VariCap). Operates with reverse bias. Varying voltage varies junction capacitance. Used for variable-frequency oscillators & for FM modulators. Active Components Semiconductor Components Diodes & Rectifiers Diode Types Zener diode. Operates with reverse bias. Operates at avalanche (breakdown) voltage. Designed to withstand avalanche current/

##### Microwave Effects and Chaos in 21st Century Analog & Digital Electronics V. Granatstein, S. Anlage, T. Antonsen, Y. Carmel, N. Goldsman, A. Iliadis, J.

or damage by inducing chaotic behavior in circuits. This is expanded upon in the following slides. The Resistor-Inductor-Diode Circuit Varactor diode (capacitance depends on voltage) Approximate equation for charge flowing in the circuit: As the amplitude of the drive (V/ of generic dynamic random access memory (DRAM) RF was injected directly into its 33MHz clock input. The DRAM module was modified to include a capacitance coupler and was installed in a personal computer running a memory-checking program. /

##### Resistance is proportional to the length and inversely proportional to the cross sectional area of the material Where, is defined as resistivity, in Ohm-meter.

V is the applied voltage T is temp. in degrees K Reverse voltage Capacitance Diode voltage Current Negative coefficient of resistance Varacter Tunnel Varactor exploits the depletion layer in terms of a parallel plate capacitor, whose capacitance is / junction is inversely proportional to the width of the depletion layer. The varactors useful for designing VCO, FM modulators and demodulators and tuning circuits. In the tunnel diode, the current through the device decreases as the voltage increases within a/

##### Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 1.1 Engineering Systems  Introduction  Systems  Electrical and Electronic.

OHT 1.82 Signals and Data Transmission  Introduction  Analogue Signals  Digital Signals  Signal Properties  System Limitations  Modulation  Demodulation  Multiplexing  Distortion and Noise Chapter 5 Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT / Storey: Electrical & Electronic Systems © Pearson Education Limited 2004 OHT 1.540  Varactor diodes –a reversed-biased diode has two conducting regions separated by an insulating depletion region –this structure resembles a /

##### Principles of Electronic Communication Systems

used as a mixer. One of the most widely used types of mixer is the simple diode modulator. 9-3: Frequency Conversion Mixer and Converter Circuits: Diode Mixer The input signal is applied to the primary winding of the transformer. The signal is/ mixers, two local oscillators, a limiter, a quadrature detector, and squelch circuits. The first local oscillator has a built-in varactor that allows it to be controlled by an external frequency synthesizer. 9-7: Receivers and Transceivers Figure 9-45: The Motorola /

##### Generation of FM Two methods of FM generation: A. Direct method: i) straight forward, requires a VCO whose oscillation frequency has linear dependence.

on applied voltage. ii) Advantage: large frequency deviation iii) Disadvantage: the carrier frequency tends to drift and must be stabilized. iv) Example circuits: 1) Reactance modulator 2) Varactor diode 1) Reactance modulator Generation of FM (cont’d) 2) Varactor diode modulator Generation of FM (cont’d) B) Indirect method: Armstrong modulator by using frequency-up conversion that involves 2 methods : a. Heterodyne method b. Multiplication method Wideband Armstrong/