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Design, Simulate, and Document Proprietary Wireless Systems
The broad acceptance of standards developed for short range wireless connectivity has been one of the notable features of the semiconductor market in the past few years. These standards include Bluetooth, various flavors of Wi-Fi, ZigBee, and new emerging standards, such as Wibree/Bluetooth ULP and Ultra Wideband. The available wireless standards are not always the best fit for the application’s requirements, however.
Maintaining Public Railways with Lower Cost and Improved Safety
A new, systematic maintenance approach now makes it possible to measure, locate, and fix rail- and tramway defects when they appear. Mature railway-engineering know-how and cutting edge technologies—including Blackfin processors and graphical system design techniques—combine to improve and optimize public transportation. This can result in longer operation lifetimes for rails, improving economy and reliability.
Impedance Measurement Monitors Blood Coagulation
Blood coagulation is a complex process by which clots are formed to end bleeding at an injured site. During heart-bypass surgery, blood is diverted to a heart-lung machine. An anticoagulant is administered during surgery—followed by a rapid reversal. This article describes a coagulation monitor that provides rapid, automated data—aiding patient safety, workflow, and decision making—and leading to improved outcomes.
Fingerprint Sensor and Blackfin Processor Enhance Biometric Identification
The need for effective, efficient security is manifest in today’s world. Individuals must be identified to allow or prohibit access to secure areas—or to enable them to use a computer. Biometric signatures identify individuals by measuring unique physical and behavioral characteristics using: a sensor, feature extraction, pattern matching, and decision making—allowing a user’s claimed identity to be authenticated or rejected.
Noise Figure and
Logarithmic Amplifiers [The Wit and Wisdom of Dr. Leif—6]
Log amps are uniquely equipped as RF measurement elements at frequencies from near-dc up to 12 GHz because of their wide dynamic range, temperature stability, excellent log conformance, and ease of use—with measurements provided directly in decibels. Noise figure is a valuable metric when log amps are used in the signal path, as it indicates the system's ability to extract information in the presence of noise.
Understanding Hot-Swap Controllers: Hot-Swap Circuit Design Example
High-availability systems, such as servers, network switches, redundant-array-of-independent-disk (RAID) storage, and other forms of communications infrastructure must be designed for near-zero downtime throughout their useful life. Components that fail or need updating must be replaced without interrupting the rest of the system. This process, known as hot-swapping or hot-plugging, requires a hot-swap controller.
Discrete- and Integrated Control of Power Amplifiers in Base Stations
In wireless base stations, the power amplifier dominates the performance in terms of power dissipation, linearity, efficiency, and cost. Monitoring and controlling the PA makes it possible to maximize the output power while achieving optimum linearity and efficiency. This article discusses the elements of a monitoring-and-control solution for the PA using discrete components—and describes an integrated solution.
Cooking Inductively: ADI iCoupler Technology Isolates Hob and User Interface
Easy-to-use inductive cooking surfaces (hobs) are significantly safer, without flames or other direct heat sources on the hob. They have better overall performance, including faster heating time, and are gaining acceptance by consumers as they are becoming more affordable. Designing the circuitry that drives the inductive plate to heat metal pots requires an understanding of a wide variety of physical principles and techniques.
Analog/Digital-Converter Clock Optimization: A Test Engineering Perspective
The entire system-clock signal chain must be understood in order to achieve optimal performance from an A/D converter. It can be discouraging to find that a circuit's accuracy is clock-jitter limited, as this problem could have been prevented during the design phase. Decreased clock jitter can be achieved through frequency division, filtering, use of an improved clock source, and proper choice of auxiliary hardware.
High Side Current Sensing: Difference Amplifier vs. Current-Sense Amplifier
Accurate high-side current sensing is necessary in applications such as motor control, solenoid control, and power management. In these applications, monitoring the current on the high side permits improved diagnostic capabilities and maintains the integrity of the ground path by avoiding the introduction of shunt resistance. The sensing circuitry must reject high common-mode voltages, while providing high gain and high accuracy.
Switching-Regulator Insights—Achieving Longer Battery Life in DSP Systems
Step-down dc-to-dc switching regulators efficiently derive a low voltage from a higher voltage, maintaining a constant output despite variations in supply voltage or load current. This article describes an architecture that provides good regulation, high efficiency, and fast response, showing both fixed-voltage operation and a resistor-programmable circuit that provides dynamic voltage scaling in DSP applications.
Faster Open-Loop Gain Measurements (Ask The Applications Engineer—38)
It is often desirable to measure the performance of a feedback network in a particular configuration so as to model the open-loop behavior. But this type of measurement is often challenging due to high gains, small input signals, and long settling times. This article shows you how to characterize the frequency response of the network rapidly and with minimal effort, using available tools and a small amount of special circuitry.
Phase Relations in Active Filters
In applications that use filters, the amplitude response is generally of greater interest than the phase response. When a filter is used inside a process control loop, however, the total phase shift is of concern, since it may affect loop stability. This article looks at first- and second-order filters, comparing phase response as a function of topology, order, and Q. Higher-order filters are treated as cascades of lower-order blocks.
Toward More-Compact Digital Microphones
As electret microphones become smaller, their element capacitance decreases. JFET preamps no longer suffice, as their relatively large input capacitance attenuates the signal from the microphone. Much can be gained by replacing JFET amplifiers with CMOS analog and digital circuitry, including easier gain setting, multiple functional modes, direct digital outputs, enhanced sound quality, and higher noise immunity.
Avoid Common
Problems When Designing Amplifier Circuits
Modern op amps and in-amps provide great benefits to the
designer, and a great many clever, useful, and tempting circuit applications
have been published. But all too often, in one’s haste to assemble a circuit,
some very basic issues are overlooked, leading to the circuit not functioning as
expected—or perhaps at all. This article will discuss a few of the most common
application problems and suggest practical solutions.
The AD9271—A Revolutionary Solution for Portable Ultrasound
Medical ultrasound systems, among the more complex signal processing devices in use today, are used for real-time detection of health problems and general diagnostic procedures. Slower than radar and faster than sonar, ultrasound systems have become increasingly portable, evolving from cart-based systems into palm-sized devices. This article discusses some of the necessary ingredients of compactness.
Reducing Ground Bounce in DC-to-DC Converters—Some Grounding Essentials
Electrical ground looks simple on a schematic, but circuit performance is dictated by the PCB layout. Ground-node analysis is difficult, especially for dc-to-dc converters, such as buck and boost circuits, which pound the ground node with large, fast-changing currents. When ground moves, performance suffers and the system radiates EMI. An understanding of ground noise can provide a sense for reducing the problem.
Low-Dropout Regulators (Ask The Applications Engineer—37)
Voltage regulators provide stable outputs independent of line
voltage, load impedance, temperature, and time. Low-dropout regulators
(LDOs) can maintain regulation with a small difference between supply voltage
and load voltage. This article introduces basic topologies of LDOs, and provides
tips for ensuring stable operation. It also discusses ADI's LDOs, which offer a
flexible approach to maintaining dc- and dynamic stability.
Elements of Motion: 3D Sensors in Intuitive Game Design
Standard video game controllers limit intuitive play,
requiring a player to learn specific control skills. The latest platforms add
motion, enabling games that are both more fun and more intuitive. This article
presents a foundation for using accelerometers in game controllers, including
operating mechanisms, measurement techniques, and specific parameters that
affect gaming performance, price, reliability, verification, and test.
High-Speed Time-Domain Measurements—Practical Tips for Improvement
Making accurate high-speed time domain measurements can be challenging, but a few tips and tricks, coupled with some good old-fashioned commonsense engineering, can help yield quick and accurate results. When choosing a scope and probe for high-speed measurement, first consider: signal amplitude, source impedance, rise time, and bandwidth. The type of probe and length of the ground lead are also important.
The circuitry ahead of a high-performance ADC is critical to achieving desired system performance. The optimal design depends on many factors, including the application, system partition, and ADC architecture. Amplifiers consume power and add noise, whereas transformers consume no power and add negligible noise. On the other hand, amplifiers maintain dc levels, provide easily adjustable gain, and have flatter response.
Multichannel Power-Line Monitoring with Simultaneous-Sampling ADCs
The rapid expansion of the electric power industry has created a worldwide need to reinforce existing transmission and distribution networks and to construct new substations. Advances in microprocessor technology and the increasing cost of support staff are key drivers for power companies to design new automated high-voltage substations using high-accuracy integrated automation systems.
Digital Isolation: A Compact, Low-Cost Solution to Complex Design Problems
New isolation capabilities—including integrated, isolated power and truly bidirectional isolation channels—are greatly simplifying the design of isolated systems. Fueled by a shift from LED-based optocouplers to chip-scale microtransformer technology that is compatible with standard CMOS processes, they fit more functionality into a single package. This article discusses two kinds of devices that embody these advances.
Lens Drivers Focus on Performance in High-Resolution Camera Modules
An Evolution of Resolution is driving the development of cell phone camera modules. Autofocus is now standard in high-resolution cameras, and features such as optical zoom, shutter control, and image stabilization are becoming common. These require the lens to move rapidly. The lens driver powers a motor to move the lens in response to digital signals. This article discusses three types of motors and how to drive them.
Capacitance Sensors for Human Interfaces to Electronic Equipment (Ask The Applications Engineer—35)
Mechanical buttons, switches, and jog wheels have long been used as interfaces between users and machines, but their many drawbacks have led designers to look for more reliable solutions. Capacitive sensors, which can be used in place of buttons, can also add versatility. Available ICs can measure the capacitance of up to 14 sensors, compensate for environmental changes, and provide a digital output.
Fast, Versatile Blackfin Processors Handle Advanced RFID Reader Apps
From inventory control to supermarket checkouts, RFID technology is transforming existing applications and enabling new ones. RFID readers detect tags and read the information they carry. Typically needing a signal processor to interface with ADCs and DACs and a network processor to communicate with servers, they can now use a Blackfin® processor to manage both signal conversion and network connectivity.
Programmable-logic controllers are compact computer-based electronic systems that use digital or analog I/O modules to control machines, processes, and other control modules. PLCs can receive (input) and transmit (output) various types of electrical signals to control and monitor many kinds of electromechanical systems.
Wideband A/D Converter Front-End Design Considerations
A factor often overlooked when using transformers in the front-end circuitry of high-speed A/D converters is that they are never ideal. Any imbalance introduced by the transformer delivers an imperfect signal to the ADC, causing overall performance to be worse than the ADC could otherwise provide. Read about the effects of input imbalances on ADC performance and circuitry that can help achieve better results.
Class D Audio Amplifiers: What, Why, and How
Class D amplifiers, first proposed in 1958, have become increasingly popular in recent years. What are class D amplifiers? How do they compare with other kinds of amplifiers? Why is class D of interest for audio? What is needed to make a good class D audio amplifier? What are the features of ADI's class D amplifier products? Find the answers to all these questions and more by reading this article.
Power Supply Management—Principles, Problems, and Parts
Determining whether a supply voltage is above a threshold or within an operating window—and powering supplies on or off in the correct sequence with respect to each other—is vital for safety, economy, durability, and proper operation of electronic systems. This article discusses how power supply designers are using flexible supply monitoring, sequencing, and adjustment circuits to manage their systems.
Design Your Own VoIP Solution with a Blackfin Processor—Add Enhancements Later
The age of voice-over-Internet-protocol is here, with packetized data streaming over low-cost Internet links. Designers must choose a cost-effective, easy to deploy, scalable platform that can implement a basic VoIP solution, while retaining plenty of capacity for value-added capabilities and services—like video, music, and imaging.
Wireless Short-Range Devices: Designing a Global License-Free System for Frequencies <1 GHz
Short-range radio transmitters can communicate without interfering with other radio equipment. Short-range devices (SRD) provide many different services—including home automation, keyless remote entry, and wireless video—typically using portions of the spectrum that allow license-free operation provided certain conditions are met.
ADC Input Noise: The Good, The Bad, and The Ugly. Is No Noise Good Noise?
All analog-to-digital converters (ADCs) have a certain amount of input-referred noise—modeled as a noise source connected in series with the input of a noise-free ADC. In most cases, less input noise is better; however there are some instances where input noise can actually be helpful in achieving higher resolution. Read this article to learn how some noise can be good noise.
Switching in USB Consumer Applications
The universal serial bus has become a dominant interface for rapidly transferring data between PCs and portable devices such as digital cameras, personal media players and cell phones. CMOS switches can be used for connecting and routing data lines in USB systems. Selecting suitable switches allows designers to enhance existing designs rather than developing new ones, significantly shortening design cycles.
A Reference Design for High-Performance, Low-Cost Weigh Scales
The accuracy required by weigh scales is not initially obvious. Their typical resolution is only 1:3,000 to 1:10,000, so a 12- to 14-bit ADC would seemingly be adequate. A closer examination shows that this is not case, however, and that a 20-bit ADC is really required. This article introduces weigh scale system specifications and design considerations, including noise, dynamic range, offset drift, gain drift, and filtering.
Using Dual-Axis Accelerometers to Protect Hard Disk Drives
The increasing use of hard disk drives in portable equipment has fueled the need to prevent their destruction when a product that contains one is accidentally dropped. This article describes a novel technique that calculates differential acceleration, thus allowing a dual-axis accelerometer to sense an impending collision in time to park the read/write head and protect the head and the platter from damage.
Serial communication buses are used to transmit data over various types of physical networks, with interconnected systems typically separated by long distances. Thus, galvanic isolation is often required to break ground loops, protect the system from high-voltage transients, reduce signal distortion, and to enhance physical safety.
A Practical Guide to High-Speed Printed-Circuit-Board Layout
Despite its critical nature in high-speed circuitry, PCB layout is often one of the last steps in the design process, with sloppy layouts sometimes causing circuit designs that look good “on paper” to render mediocre performance. This article addresses high-speed layout from a practical perspective, discussing topics that can improve circuit performance, reduce design time, and minimize time-consuming revisions.
DDS Controls Waveforms in Test, Measurement, & Communications
Direct Digital Synthesizers can generate frequencies from a few hertz to greater than 400 MHz with less than 1 degree phase resolution. They can quickly hop from one frequency to another—in a phase-continuous manner—without settling anomalies. DDS-based waveform generation is used to locate resonant frequencies in industrial applications and as agile frequency sources in RF communication systems.
The novel application of a phase-locked loop allows one channel of the AD71028 BTSC- (Broadcast Television Standards Committee) encoder to derive the primary channel’s master clock, while the other channel provides the Multichannel Television Sound (MTS) stereo-encoded output for satellite set-top boxes and receivers.
Which ADC Architecture Is Right For Your Application?
Selecting the proper ADC for a particular application can be a formidable task, considering the thousands of available converters. An understanding of three popular architectures—successive-approximation, sigma-delta, and pipelined—and their relationship to the data acquisition, precision measurement, audio, and high speed markets is a useful supplement to selection guides and search engines.
Pushing the State of the Art with Multichannel A/D Converters
The most demanding data-acquisition requirements surpass the performance levels provided by commercially available integrated-circuit ADCs. Innovative solutions that fulfill high-end data-acquisition system needs while awaiting the next performance breakthrough use signal averaging, for increased resolution without loss of speed—and time interleaving, to increase sampling rates without loss of resolution.
Transformer-Coupled Front-End for Wideband A/D Converters
ADCs are being used at ever higher frequencies, making receiver front-end design increasingly important. Many applications are moving to super-Nyquist sampling in order to eliminate a mix-down stage, but amplifier noise will degrade the signal-to-noise ratio at these frequencies. Transformers can be used to replace the amplifier, minimizing noise and providing good high-frequency coupling.
A Smart Modem for Robust Wireless Data Transmission Over ISM Bands
Heavy usage of the license-free 2.4-GHz band—from microwave ovens, Bluetooth, WLAN 802.11b, and cordless phones—has increased interest in the lower-frequency ISM bands. The ADF7020 UHF transceiver and ADSP-BF531 Blackfin processor can implement a smart modem that has the ability to overcome interference from legacy systems and the flexibility required to deal with the lack of established standards.
Enhance Processor Performance in Open-Source Applications
Open-source algorithms are becoming a popular alternative to royalty-based code in embedded processing applications. Each compiler will exploit a given processor’s strengths at the expense of other inefficiencies, so developers must optimize the acquired code for the chosen processor. This article will explore the porting of open-source algorithms for music-, video-, and speech processing to Blackfin processors.
Low-power, fixed-point Blackfin processors now have the performance required to handle signal processing and control functions, while also driving the small liquid-crystal-displays used in many multimedia applications. Their parallel peripheral interface integrates LCD drive capability with high-performance media processing.
Support for the Designer—Improved ADI Website Helps You
If you are an old friend, perhaps you’ve already found that www.analog.com is friendlier than ever. If you are new to our website, Welcome! This article introduces our new Design Center, where you can find tools and utilities such as parametric searches, selection tables, signal chains, models, and Analog Wizards—all intended to help you quickly find and apply the best products for your design.
Designing Memory-Efficient, Real-Time Audio Systems With VisualAudio
Home theater and automotive audio systems continue to increase in complexity. VisualAudio™, a new software tool for designing and developing audio systems, provides a real-time-architecture that is especially well-suited to the challenges of audio product development. This article introduces VisualAudio, describing its framework, audio modules, and application to audio product development.
Wideband CMOS Switches (Ask the Applications Engineer—34)
Wideband CMOS switches are designed to meet the requirements of devices transmitting in the ISM (industrial, scientific, and medical) band (900 MHz and up). Their low insertion loss, high isolation between ports, low distortion, and low current consumption make them ideal for many high frequency applications that require low power consumption and the ability to handle transmitted power up to 16 dBm.
The JPEG 2000 standard defines a new image-coding scheme using state-of-the-art compression techniques based on wavelet technology. Its architecture is useful for many applications, including Internet image distribution, security systems, digital photography, and medical imaging. This article highlights some of its benefits.
All About Direct Digital Synthesis (Ask the Applications Engineer—33)
Direct digital synthesis (DDS) is a method of producing an analog waveform—usually a sine wave—by generating a time-varying signal in digital form and then performing a digital-to-analog conversion. Because operations within DDS devices are primarily digital, they can offer fast switching between output frequencies, fine frequency resolution, and operation over a broad spectrum of frequencies.
Adjustable Cable Equalizer Combines Wideband Differential Receiver with Analog Switches
Category-5 unshielded twisted-pair cable, like any transmission medium, suffers from dispersion and high-frequency signal loss. This article presents an equalizer that compensates Cat‑5 cable at frequencies to 100 MHz and lengths to 1000 feet, making it suitable for KVM networking and high-resolution video transmission.
Capacitive loading of amplifiers reduces bandwidth and slew rate, and introduces a phase lag in the feedback loop that can cause instability. ADI has published a lot of information on dealing with capacitive loading and other stability issues in books, earlier issues of Analog Dialogue, and some design tools. Here's a refresher course.
This article introduces the AD8555, which simplifies bridge measurement systems by integrating a zero-drift instrumentation amplifier with programmable gain, programmable output offset, fault detection, output clamping, and low-pass filtering, thus providing the complete signal conditioning path between a sensor and an ADC.
Current Measurement in Solenoids for Automotive Control Systems
Linear solenoids operate pistons and valves to accurately control fluid pressure or flow in automotive transmissions. Connected in feedback loops and powered by PWM signals, their position can be determined by measuring their current. This article shows several methods of using an AD8200 to measure solenoid current.
Use of Video Technology to Improve Automotive Safety Becomes More Feasible with Blackfin Processors
Processors control almost every function in today's automobiles, including climate control, engine control, and entertainment. Now, the increasing performance-to-cost ratio of signal processors is leading to their use in the safety subsystem. Blackfin media processors can help to make video-based automotive safety a reality.
Why and How to Control Fan Speed for Cooling Electronic Equipment
Compact electrical fans are cheap and have been used for cooling electronic equipment for more than half a century. The technology for controlling these fans has evolved significantly, enabling lower power, quieter systems to be designed. This article suggests some useful approaches to efficient heat removal.
Mixed-Signal Control Circuits Use Microcontroller for Flexibility in Implementing PID Algorithms
Proportional-Integral-Derivative (PID) algorithms are commonly used to provide accurate, stable process control. Systems typically require an ADC to measure the process variable, a DAC to manipulate the physical input, and a digital controller. This article shows how a MicroConverter® can simplify the system implementation.
Closed-Loop Control of Variable Optical Attenuators with Logarithmic Analog Processing
Translinear log-amps simplify VOA absorbance measurements by providing a linear-in-dB relationship between the input photo-current and resulting output voltage, thus eliminating the division and exponentiation processes that would be required with classical architectures using transimpedance amplifiers.
ECG Front-End Design is Simplified with MicroConverter®
This article provides an overview of a traditional analog ECG system, then proposes a simpler circuit that uses a MicroConverter®—a “system on a chip” that combines an A/D converter, microcontroller, and flash memory—to flexibly perform analog-to-digital conversion, digital filtering, and digital amplification.
Fast-Locking, High-Sensitivity Tuned-IF Radio
Receiver Achieved with a
To improve sensitivity and selectivity in modern radios, phase noise and reference spurs must be minimized, and lock time must be reduced. The circuit outlined in this article uses an ADF4107 7-GHz PLL synthesizer in a tuned-IF architecture to improve local oscillator (LO) performance with respect to these parameters.
How to Save Power in Battery Applications Using the Power-Down Mode in an ADC
Minimizing the current drawn by system components can extend battery life—a critical concern in battery-powered applications. Most ADCs provide a power-down mode, but the technique used to place them into the power-down state—and its effectiveness—differ from part to part. This article describes some novel methods.
Advanced Digital Post-Processing Techniques Enhance Performance in Time-Interleaved ADC Systems
This article details the matching requirements for 12- and 14-bit time-interleaved ADC systems, discusses the idea of advanced digital post-processing techniques as an enabling technology, and introduces the AD12400, a device employing the most promising performance to date.
Dynamic Memory Allocation Optimizes Integration of Blackfin® Processor Software
Blackfin’s memory is versatile and easy to use in many applications, but in some applications, such as embedded cell phone systems, memory allocation can be difficult for any embedded processor. This article introduces ADIalloc, a dynamic memory allocation tool designed to deal with this challenge.
Systems with multiple supply voltages have become common, so sequencing and supervision of their supplies has grown in importance. The ADM1060 simplifies this task by providing multiple supply supervisors, sequencing logic, and output drivers, and is easily programmed using an intuitive graphical user interface.
Compact Web-Manufacturing Process Defect Detection System Uses a Camera and ADI Blackfin Processor
One aim of industrial machine vision is to develop electronic systems to replace human vision in industrial quality control. This article describes a new integrated environment—intended for real-time defect detection—that eliminates the need for an external frame grabber and associated host computer peripherals.
Amplifiers as Comparators? (Ask the Applications Engineer--31)
In principle, any high-gain amplifier can be used as a comparator, but as usual, "the devil is in the details". This article helps designers to understand the basic differences between amplifiers and comparators, allowing them to determine when an amplifier can be used to improve precision, reduce cost, or save space.
New iMEMS Angular Rate-Sensing Gyroscope
With full-scale ranges of 150°/s and 300°/s, the new ADXRS150 and ADXRS300 represent a quantum jump in gyro technology. The first commercially available surface-micromachined angular rate sensors with integrated electronics, they are smaller—with lower power consumption, and better immunity to shock and vibration—than any gyros having comparable functionality.
Getting 14-Bit Performance from a 32-Channel 14-Bit String DAC
The AD5532 32-channel, 14-bit voltage output D/A converter can be used in DAC mode or Infinite Sample-and-Hold mode. The DACs have 14-bit monotonicity, but only ±0.39% integral nonlinearity. This article shows how the DACs can be calibrated to provide 14-bit performance.
Glueless, Hot-Swappable CompactFlash™ Interface
CompactFlash cards are used in MP3 players, digital cameras, handheld PCs, and many other electronic devices, and can be used for nonvolatile storage and transfer of music, pictures, and data. This article describes a simple interface between the ADSP-2191M digital signal processor and a CompactFlash card.
High-Speed Op Amp Drives a 16-Bit, 1-MSPS Differential-Input A/D Converter
High-resolution A/D converters usually require input buffer amplifiers because they present both dc- and high-frequency dynamic loads to the source that is driving them. To maintain system accuracy, the settling time, noise, and total harmonic distortion of the driver must be considerably better than that of the ADC itself. This is a significant challenge in systems employing fast 16- or 18-bit successive-approximation ADCs.
Bus Switches for Speed, Safety, and Efficiency: What they are, what you should know about them
Bus switches are characterized by sub-nanosecond propagation delay and fast switching, and are designed for connecting to high-speed digital buses. They are ideally suited for voltage translation, hot swapping, hot plug, bus- or capacitance isolation, and many other applications. The key features that make them suitable for so many different applications include low on-resistance, low capacitance, and low propagation delay.
Detecting Fast RF Bursts Using Log Amps
Monolithic log amps can handle signals with dynamic ranges up to 100 dB, and can respond to RF bursts as short as a few tens of nanoseconds. When demodulating log amps are used to detect fast RF bursts, however, strange tails sometimes appear at the output when the burst shuts off. This article explains the cause of these tails and offers suggestions on how to eliminate them.
Single-Chip Digitally Controlled Data-Acquisition as Core of Reliable DWDM Communication Systems
Optical communication systems use ADCs and DACs in control loops for the thermoelectric cooler (TEC), laser diode driver (LDD), and avalanche-photodiode (APD) monitoring and biasing circuitry. Dedicated control loops are used for driving the pump laser, reading its power level, adjusting the extinction ratio and average power in the transmit laser diode, and maintaining the laser diode at a stable temperature. This article describes a control system that has a MicroConverter™ at its heart.
Dynamic Power Management Optimizes Performance vs. Power in Embedded Applications of Blackfin™ DSPs
Consumer products employing multimedia embedded
processors require complex computational abilities and high clock rates, but
also low power consumption. Performance vs. power must be optimized for the
specific application. A strategic power management approach is achievable with
the inherent dynamic power management capabilities of the Blackfin DSP
family.
Mirrors with Integrated Position-Sense Electronics for Optical-Switching Applications
Signal paths using all-optical switches will be required for 40-Gbit telecommunication systems. ADI's integrated optical micro-electromechanical system (optical iMEMS) technology combines mirrors, high-voltage CMOS for electrostatic deflection, and low-voltage CMOS for on-chip capacitive position-sensing. This technology could drastically lower the cost of all-optical switching systems.
How Ultrasound System Considerations Influence Front-End Component Choice
Medical ultrasound machines are among the most complex signal processing machines in use today, and thus present many trade-offs in implementation due to physics, cost and performance requirements. An overview of the system is presented in order to provide an understanding of the front-end IC functions and desired performance levels, especially for the low-noise amplifier, time-gain control, and A/D converters.
PLL Synthesizers (Ask the Applications Engineer--30)
What is a PLL synthesizer? What are the key performance parameters? How do I choose external components? Why are phase noise and lock time important, and how do I optimize them? Adrian Fox provides answers to these questions, and presents new ADI PLLs and simulation tools.
"No-new-wire" wireline technologies, as well as DSL and cable, require mixed-signal interfacing between transmission medium (power line, cable, twisted pair) and the digital baseband processors and controllers. A new family of mixed-signal front-ends (MxFE™ integrated circuits) provide the compact electronics to bridge this gap flexibly with high performance at low cost (AD9875/AD9876).
Interfacing a Blackfin DSP to High-Speed Converters for Wireless Applications
A new generation of fast, low-power, programmable general-purpose signal processors—ADI's Blackfin™ family—is allowing designers to avoid the costs of custom digital hardware. Soon-to-be-released new family members will enable a wide range of wireless applications. But an early member of the Blackfin family can be applied to outpace existing approaches—even though this DSP does not have a "wireless-ready" interface.
X-Amp™, A New 45-dB, 500-MHz Variable-Gain Amplifier (VGA), Simplifies Adaptive Receiver Designs
The AD8367 is a wideband, variable-gain amplifier with gain (in dB) accurately proportional to the control voltage. An on-chip square-law detector allows it to be used directly in automatic gain control (AGC), to maintain a preset rms output amplitude, irrespective of the input amplitude and waveshape, with a minimum of external components.
SigmaDSP™ Digital Audio Processing
SigmaDSP processors, such as the new AD1954, are fully integrated in both hardware and software to provide low-cost, zero-hassle, fully configurable processing of digital audio signals from sources such as CDs, DVD-Audio, SACD, and MP3, and deliver stereo and subwoofer analog signals via D/A converters with 112-dB signal-to-noise ratio.
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