Design Features

 353 results found for Design Features, displaying items 1 - 20

March 2010   [Components]
Tune Out Spurious In Dual-Mode BPFs
Miniature filters are essential for wireless communications systems although they often suffer from limited rejection bandwidths. However, through the use of a modified coupling structure for harmonic suppression, it has been possible to design a dual-mode filter capable of wide rejection bandwidth and 20-dB rejection through 8.5 GHz. A number of dual-mode filters1-4 have been developed based on microstrip square loop...  — Wei Hong , et al.

March 2010   [Components]
Analyze Phase Noise In A Sampled PLL (Part 3)
Some have suggested that PLL noise degrades with frequency because the charge pumps are powered on for longer periods compared to the sampling period and therefore allow more noise to be transferred to the loop filter. In fact, the noise follows exactly what would be expected from FM theory and sampling theory. From FM theory, the noise is expected to increase by 6 dB for every doubling of frequency (20logfs). However, from sampling theory, the noise ...  — Peter Beeson

March 2010   [Components]
Image-Reject Mixer Arms Direct-Conversion Receivers
Mixer linearity is critical to the performance of direct-conversion receivers with low intermediate frequencies (IFs). By biasing a low-IF image-reject mixer designed for a fully duplex system, such as UMTS, it is possible to achieve outstanding linearity even in the presence of large blocking (interference) signals, and even in a UMTS system, where the transmit signal is often the largest blocking signal for the receiver. The mixer is designed for...  — J.G. Gardiner , et al.

March 2010   [Components]
Forecast Rain Effects On Microwave Links
Propagation of electromagnetic (EM) waves through the air is difficult to predict, due to atmospheric effects. Raindrops, for example, can act as scatterers that attenuate and affect the polarization of the propagating EM waves. Scattering theory has treated effects on the far-field regions of receive and transmit antennas in communications links, but not near-field effects. In this first of a two-part article, this analysis examines the nearfield ...  — Dr. John Howard

March 2010   [Communications]
Semiconductors Simplify Direct-Conversion Design
Direct-conversion architectures enable the broadband radios needed to support multimode, multiple standards in third-generation (3G) and fourth-generation (4G) wireless networks. The capability of handling signals from 400 MHz to 4 GHz across the globe has pushed infrastructure and mobile-device developers to seek new levels of performance for the components in those systems. Fortunately, improved silicon germanium (SiGe) and CMOS...  — Cecile Masse

February 2010   [Components]
Low-Power LNA Drops Noise At 2.4 GHz
Low-noise-amplifier (LNA) design requires tradeoffs, often among such goals as noise figure, gain, linearity, and stability. In addition, portable applications call for low power consumption. But through the use of a common- gate (CG) architecture for input impedance matching and reduced power consumption through currentreuse techniques, an RF CMOS LNA was developed with 15.5-dB forward gain and 1.68 dB noise figure at 2.4 GHz. With its excellent...  — Baimei Liu , et al.

February 2010   [Test & Measurement]
Analyze Phase Noise In A Sampled PLL (Part 2)
Phase noise in sampled phase-locked loops (PLLs) can impact the performance of a wide range of commercial and military systems, including communications networks based on phase modulation. As shown last month in the first installment of this three-part series, modeling approaches may differ depending upon whether a PLL is a continuous-time or sampled system, with nonlinear approaches needed for th latter. In this second article installment, it may be...  — Peter Beeson

February 2010   [Components]
Match The Ports Of Differential Devices
Differential or balanced devices are widely used in communications systems for their high immunity to noise. However, they can be difficult to integrate since the widely used S-parameter matching method cannot simply be applied. Fortunately, a generic method derived from the mixed-mode S-parameter concept can be used to match differential devices. It is simple and effective, as will be borne out by verification via four-port vector network analyzer (VNA) and...  — Stephane Wloczysiak

February 2010   [Components]
Optimize Class E Power Amplifiers
Amplifier efficiency is essential not only for mobile devices, but increasingly to conserve power consumption in wireless communications base stations and cell sites. The Class E amplifier in this article produced efficiency of 60 percent from 1.9 to 2.2 GHz using a standard packaged transistor. 1 The techniques used to design and build this amplifier can be employed to design Class E amplifiers at any frequency of interest. The Class E...  — Gayle Collins , et al.

January 2010   [Test & Measurement]
System Performs FM Radio Drive Testing
Commercial automotive AM/ FM radios must perform dependably under a variety of operating conditions. Because designers of these radios employ digital-signal-processing (DSP) algorithms to overcome the effects of reflections, signal multipath, and fading, they often spend weeks in the field analyzing the effects of different signal conditions. A more practical and less time-consuming solution is the use of actual recorded radio signals to simulate the...  — David Brace , et al.

January 2010   [Test & Measurement]
Analyze Phase Noise In A Sampled PLL, Part 1
Phase locked loops (PLLs) have been used for years to stabilize signal sources such as oscillators. In the past, loop bandwidths tended to be small compared to the sampling frequency, but with modern communications systems, requirements for faster switching times mean that this is no longer the case. Narrow-bandwidth PLLs can be effectively modeled and simulated by means of linear analysis, but these same approaches fall short for ...  — Peter Beeson

January 2010   [Components]
Match Loop Antennas Via Mutual Inductance
Loop antennas are widely used in small wireless products, particularly for UHF bands between 300 and 1000 MHz. They are small in size relative to wavelength, independent from a ground plane, and relatively immune to the influence of nearby objects. They are also easily implemented in printedcircuit form with corresponding low cost. But their low radiation resistance makes them difficult to match and subject to low efficiency. They exhibit high...  — Alan Bensky

January 2010   [Components]
Dissect PA Distortion From OFDM Signals
Power-amplifier (PA) distortion must be minimized in any broadcast application to prevent interference with adjacent channels. Distortion can be present in the form of amplifier clipping, intermodulation distortion (IMD), and memory effects. For some communications standards, such as Brazil’s ISDB-T standard, which is based on orthogonal frequency- division-multiplex (OFDM) modulation, excessive phase distortion in the transmit amplifiers...  — Jose De Souza Lima , et al.

December 2009   [Components]
Class F Amplifier Boasts High Efficiency
Pulsed radar systems require high power levels but, increasingly, also demand power amplifiers with high efficiency. To meet those needs at L-band frequencies from 1200 to 1400 MHz, a Class F amplifier was developed with reduced conduction angle to maximize efficiency. The amplifier employs four parallel, internally matched silicon-bipolar transistors in a common-base configuration. They are biased in Class C mode to achieve the high output power levels required by pulsed radar systems....  — Sami Bousnina , et al.

December 2009   [Components]
Triband Cellular Antenna Tackles E-Field Testing
Antennas for wireless applications must handle more bands than ever before, given the growing number of cellular and other wireless standards contained in handsets and base stations. In support of measurements to be performed on cellular base stations, the authors have implemented a printed-circuit dipole antenna on a two-layer RO4350B laminate from Rogers Corp. The compact printed antenna covers cellular bands at 900, 1800, and 2100...  — Dimitris Kolokotronis , et al.

December 2009   [Materials]
Microwave Materials Lay Foundation For PAs
Power-amplifier designers typically create a circuit based on specific active devices for the output stage. While the choice of transistor determines the ultimate performance of an amplifier, printed-circuit-board (PCB) materials can also play a major role in an amplifier design. Selecting optimum substrate materials for an amplifier can improve gain and stability, and enable the maximum output power possible for a design. High-frequency amplifier designers have a wide array...  — John Coonrod

December 2009   [Components]
Examine Antenna Tunability In Implanted Systems
Electronic devices are increasingly being implanted inside the human body to improve medical diagnostic or therapeutic efficacy. Fine tuning these devices requires communications with medical professionals, yet direct communications are problematic due to the locations of these systems within the body. A growing trend has been to communicate with these systems by means of wireless RF transceivers. Care must be taken when designing an antenna for such systems as canonical antenna design methods...  — Mark Lanciault , et al.

November 2009   [Computer-Aided Engineering]
Simulating RF Tuned Stages
Assessing post-production- tuning (PPT) elements should be part of any RF worstcase circuit analysis (WCCA). Unfortunately, PPT elements are often omitted or incorrectly incorporated into an analysis, even though including such tuning elements into a computer-aidedengineering (CAE) model is often a simple task. Correctly accounting for PPT elements depends on the ability to define the PPT procedure and to mathematically define the relationships ...  — Steven M. Sandler

November 2009   [Components]
Examine Balanced Twisted Bifilar Lines
Balanced twisted bifilar transmission lines have broad applications for any circuits in which impedance transformations are required. By using a vector network analyzer (VNA), it is possible to measure the characteristic impedance of these balanced transmission lines in order to design desired impedance transformations. Measurements with a VNA can be made by using a balancedunbalanced (balun) transformer that converts a balanced network to an unbalanced network. In...  — Antonio Alves Ferreira, Jr. , et al.

November 2009   [Computer-Aided Engineering]
Analyze BER Performance Of Wireless FSK Systems
Modern communication systems employ digital modulation for a variety of reasons, including improved immunity to noise and channel impairments as well as enhanced security compared to analog modulation. In addition, advances in very large-scale integration (VLSI) and digital signal processing (DSP) technology have made digital modulation more cost effective than analog transmission systems. Digital transmissions accommodate digital error-control...  — Hamood Shehab Hamid , et al.





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