Showing papers in "IEEE Microwave Magazine in 2010"

Chipless RFID: Bar Code of the Future

Abstract: Radio-frequency identification (RFID) is a wireless data capturing technique that utilizes radio frequency (RF) waves for automatic identification of objects. RFID relies on RF waves for data transmission between the data carrying device, called the RFID tag, and the interrogator.

60 GHz Wireless: Up Close and Personal

Abstract: To meet the needs of next-generation high-data-rate applications, 60 GHz wireless networks must deliver Gb/s data rates and reliability at a low cost. In this article, we surveyed several ongoing challenges, including the design of cost-efficient and low-loss on-chip and in-package antennas and antenna arrays, the characterization of CMOS processes at millimeter-wave frequencies, the discovery of efficient modulation techniques that are suitable for the unique hardware impairments and frequency selective channel characteristics at millimeter-wave frequencies, and the creation of MAC protocols that more effectively coordinate 60 GHz networks with directional antennas. Solving these problems not only provides for wireless video streaming and interconnect replacement, but also moves printed and magnetic media such as books and hard drives to a lower cost, higher reliability semiconductor form factor with wireless connectivity between and within devices.

Smart Modeling of Microwave Devices

Abstract: Modeling and computer-aided design (CAD) techniques are essential for microwave design, especially with the drive towards first-pass design success. We have described neural networks for microwave modeling and design. Neural networks are suitable when modeling a required relationship for which analytical formulas are hard to derive, or for which the computational effort is too high. This relationship can be either of the IO relationship of the overall model (straight neural network model), the output-input relationship (inverse model), a relationship between existing model and desired data (neuro-SM), or relationship of a subpart of the overall model (knowledge based neural network). Neural networks are fast to evaluate, and the neural network formulas are easy to implement into microwave CAD. The simplicity of adding input neurons or hidden neurons makes neural network flexible in handling functions of different dimensions and of different degree of nonlinearity. We have also demonstrated that neural networks are helpful in developing parametric or scalable models for passive and active microwave devices.

The Six-Port in Modern Society

Abstract: Modern wireless sensing and communication systems are often based on high bandwidth and high carrier frequencies. In the range beyond 100 GHz, common receiver architectures, like active homodyne or heterodyne receivers, have an issue with the amplification needed for mixing. Also, high bandwidth is a problem for these systems. In this context, the six-port receiver is a good alternative, just as well as for lowvolume markets. The six-port concept is based on the additive superposition of the two RF input signals using four different relative phases leading to constructive or destructive interaction. The resulting signals are directly downconverted to baseband by diode circuits operated in detector or mixing mode. The complexvalued information can be easily reconstructed from the four baseband voltages. Historic evolution leads from the reflectometer approach for an alternative vector network analyzer to receivers for sensing and communications. A recent topic is the technology gap in automotive workshops for adjusting the long-range radar sensor of a car. Here, the six-port concept as alignment tool is a good choice, because of its excellent phase resolution. Currently, the integration of the six-port receiver on a MMIC for frequencies beyond 100 GHz is the focus of current work and will be intensified in the future. Will the six-port concept replace common active homodyne and heterodyne receivers? No, but it is a serious alternative for millimeter-wave frequencies and ultrahigh-bandwidth applications in wireless sensing and communication systems. This modern concept can tap new markets for both wireless sensors and sensor networks.

Wireless Implants

Abstract: In vivo wireless biomedical microsystems fueled by the continued scaling of electronic components and the development of new micro sensors and micropackaging technologies is rapidly changing the landscape of the electronics and medical industry. These devices can be used for a myriad of monitoring, diagnostic, therapeutic, and interventional applications that range from the well known cardiac pacemakers and defibrillators to emerging applications in visual prosthesis, brain computer interfaces (BCIs), and embedded monitoring of a variety of medical useful variables such as oxygen, glucose, pH level, pressure, and core temperature. This article presents a brief overview of design considerations for implementing wireless power and data interfaces for in vivo biomedical devices. Examples of emerging implantable and ingestible wireless biomedical devices are discussed.

The Linearity-Efficiency Compromise

Abstract: This article attempts to improve the average efficiency and linearize the work-horse of RF power amplification- the class-B (or class AB) PA-relying, for example, on predistortion, dynamic load modulation or ET. Nevertheless, whenever higher efficiencies are desired, the current-mode class-B PA must be replaced by switchedmode PAs (for example, class-E or class-F), completely modifying the paradigm of RF amplification. In fact, as these are saturated circuits, they cannot respond to excitations of variable amplitude; and thus the original signal envelope must be restored by operating the PA as an AM modulator via dynamic supply adaptation. A good example of this is the EER arrangement.

Graphene for Microwaves

Abstract: Graphene nanoelectronics is an emerging area of research. The 2010 Nobel Prize for physics was awarded to A. Geim and K. Novoselov for the discovery of graphene and its unexpected physical properties, paving the way for many new applications in the area of nanoelectronics, nanooptics, and solid state physics. The most-studied microwave device is the graphene transistor, which, in only three years, has reached a cutoff frequency of 100 GHz. As consequence of this impressive development, the prediction that a 0.5-1 THz graphene FET transistor will soon be demonstrated is quite realistic. Moreover, graphene multipliers and other microwave graphene devices are expected to follow the graphene FET development dynamics and reach 100 GHz in few years.

Ultrawideband Filter Technologies

Abstract: This article presents an introduction of recently developed techniques for the design and implementation of UWB bandpass filters, including single-layer and multilayer technologies. Several techniques using single-layer technology were reported on, including the MMR technique, the hybrid microstrip/CPW technique, the optimum short-circuited-stub technique, the cascaded highpass/lowpass filter technique and techniques that use EBG-loaded structures.

Greater Than the Sum of Its Parts

Abstract: Most RF systems are based on a self-design approach, in which the components are conceived independently from one another, based on budget specifications and following a pre-assigned common 50-? impedance interface. This approach requires the design of separate components with their own shielding package, related size constraints, and 50-? terminals. When these components are then combined on the system assembling, they require many interconnecting matching and transition circuits.

Advanced Doherty Architecture

Abstract: For modulated signals with a high peak-to-average power ratio (PAPR), the transmitter has to be operated with its average output power backed off for an acceptable linearity at the expense of low efficiency. To achieve high efficiency and high linearity at the same time, both an efficiency enhancement technique and a linearization technique should be utilized. A powerful and reliable linearization technique, digital predistortion (DPD), is currently the most favored method for the linearization of base-station amplifiers [1]-[3]. Possible efficiency enhancement techniques are the hybrid envelope elimination and restoration/envelope tracking technique (H-EER/ET) and the Do-herty technique.

Modeling GaN: Powerful but Challenging

Abstract: As GaN technology has developed, first in research laboratories and more recently in multiple commercial device manufacturers, the demand for improved nonlinear models has grown alongside the device process improvements. The need for improved models for GaN is twofold: first, GaN devices have unique nuances in behavior to be addressed; second, there is a desire for improved accuracy to take full advantage of the performance wins to be gained by GaN HEMT performance in the areas of high efficiency and high-power operation.

Designing and Testing Software-Defined Radios

Abstract: This article reviews the main parts of a software-defined radio (SDR) to emphasize several possible implementations of both receivers and transmitters. We describe solutions for testing and characterizing these types of devices. SDRs typically operate in both the analog and the digital domains, thus mixed-domain instrumentation is necessary to carry out testing. We first give a short overview of several architectures for SDR receiver front ends. Then, several possible architectures for transmitter front ends are described. We discuss methods that can be used to improve amplifier efficiency. Instrumentation currently available in the commercial market that allows the characterization of such types of transceivers is presented.

Efficiently Amplified

Abstract: Modern wireless communication systems have evolved to support increasing numbers of subscribers and provide higher data rate services within the limited frequency resources. As part of this evolution, many transmitted signals in the new standards, such as WCDMA, long term evolution (LTE), and worldwide interoperability for microwave access (WiMAX), now utilize a high peak-to-average power ratio (PAPR) caused by complex modulation schemes, generating the rapid change in the magnitude of signal. In particular, the PAPRs of the signals exceed 9 dB at 0.01% level of complementary cumulative distribution function. Use of high PAPR signals result in the power amplifier (PA) operating at a large enough back-off to satisfy the stringent linearity requirement. However, in this region, efficiency of the PA is very low. To bolster low efficiency in the back-off region, various efficiency boosting techniques have been considered over time.

Siliconization of 60 GHz

Abstract: Silicon-based RF and microwave technology has had a dramatic impact on the world of wireless technology. We can now access voice/data and entertainment in virtually every corner of the globe - with everything from short range Bluetooth and WiFi networks to cellular and satellite networks - to meet different range and throughput requirements. A laptop computer without wireless capability is unthinkable today, whereas, ten years ago, these technologies were in their infancy.What do the next ten years hold? What gaps in wireless technology exist even today? Perhaps the most obvious missing link is between the various devices that we carry with us, such as cellular phones or personal digital assistants (or smart phones if you prefer), digital cameras, music and video players (such as the ubiquitous iPod), laptops, and peripherals such as external hard drives and monitors. The case of the mobile smart phone is particularly important since the existing wireless connectivity is either too slow and power hungry (Bluetooth) or designed and optimized for longer ranges (WiFi). What is missing is a wireless universal connectivity that can support high data rates demanded by large data rate multimedia applications. Wireless technology has been conspicuously absent from MP3 music players (such as Apple's iPod), which are ideal candidates for downloading music and video. While ultrawideband (UWB) technology using the 3-0 GHz band promised to fulfill these needs, it fell short in many ways, and, today, most of the start-up companies pursuing UWB have folded.

Analyzing LINC Systems

Abstract: In this article, an analysis of LINC PA efficiency and linearity is observed. The use of two highly efficient PAs operated with constant envelope signals in the LINC transmitter does not in and of itself guarantee that the overall efficiency of the LINC amplifier will be high. It's shown that the use of matched combiner gives good linearity but the efficiency is decreased when the peak-to-average of signal increases. The same isolation between the two amplifiers is what gives the high linearity at the output. To avoid the efficiency losses in the matched combiner, the lossless Chireix-outphasing combiner has been presented. The nonisolating combiner presents time-varying impedances to the output of RF amplifier of each branch as the phase difference between the branches increases, thus significantly improving the LINC average efficiency. Impedance mismatching between the amplifiers and outphasing combiner have been explicitly taken into account. Closed-form expressions for the voltages at the output of the combiner, the instantaneous impedance seen by each amplifier, as well as the instantaneous efficiencyof the combiner, have been developed and presented. It has been shown that the new voltage expressions are consistent with the nonlinearity behavior of the Chireix combiner/thus demonstrating that the combining structure is a source of nonlinearity. To validate this approach many types of signals are considered as CDMA WCDMA and OFDMA (QPSKA, 16-QAM, 64-QAM) signals. Other sources of distortion such as imbalances between two branches are presented and how to compensate this imbalance is proposed. In light of the results obtained, the use of the Chireixoutphasing combiner with saturated nonlinear amplifiers to reach the objective of both high-efficiency and high-linearity amplification does not seem possible. The potential use of phase predistortion to reach this objective remains to be investigated.

Flipping the CMOS Switch

Abstract: As CMOS technology is scaled down and adopted for many RF and millimeter-wave radio systems, design of T/R switches in CMOS has received considerable attention. Many T/R switches designed in 0.5 ?m 65 nm CMOS processes have been reported. Table 4 summarizes these T/R switches. Some of them have become great candidates for WLAN and UWB radios. However, none of them met the requirements of mobile cellular and WPAN 60-GHz radios. CMOS device innovations and novel ideas such as artificial dielectric strips and bandgap structures may provide a comprehensive solution to the challenges of design of T/R switches for mobile cellular and 60-GHz radios.

NVNA versus LSNA: enemies or friends?

Abstract: The NVNA and the LSNA are powerful instruments which allow to measure the full nonlinear behavior of microwave devices. They are super-oscilloscopes which are able to measure absolute time domain waveforms. Both instruments are based on a different measurement principle: the mixer-based architecture of the NVNA and the sampler based architecture of the LSNA. They both have their advantages and disadvantages. By using these nonlinear measurement instruments, one is able to gain a good insight into the nonlinear behavior of a system. Combining good measurements with good insight, results in good nonlinear modeling.

Interpreting Transistor Noise

Abstract: The simple noise models of field effect and bipolar transistors reviewed in this article are quite useful in engineering practice, as illustrated by measured and modeled results. The exact and approximate expressions for the noise parameters of FETs and bipolar transistors reveal certain common noise properties and some general noise properties of both devices. The usefulness of these expressions in interpreting the dependence of measured noise parameters on frequency, bias, and temperature and, consequently, in checking of consistency of measured data has been demonstrated.

Integrated Adjustable Phase Shifters

Abstract: When examining a monthly bank account statement, it is not only the number below the bottom line that matters. Whether that number has a minus or plus in front of it is crucial. For many technical problems, the sign matters as well. In circuits, we can change the sign by means of phase shifters. Moreover, by using phase shifters, intermediate states between the signs (including complex values) can be set in circuits. Hence, phase shifters play an important role in electrical engineering. Unfortunately, this article does not give direct insights to change the sign of your bank statement. However, it aims to give a comprehensive overview of tunable phase shifters for radio frequency (RF) applications including cookbooklike design guidelines and performance comparisons. The focus of this article is put on phase shifters fully integrated in a chip.

The Roots, Rules, and Rise of RFID

Abstract: This article has offered a brief excerpt of the basic requirements and current development trends in (passive) RFID systems in different application areas. Even after reaching a sophisticated state of development, RFID technology is still dependent on sufficient acceptance at the market. Conventional bar code systems lack programmability, have low storage capability, and need a line-of-sight connection to the reader. If the fall in prices for low-cost tags continues, barcodes could be largely replaced in some years. In this case, additional features like positioning or sensing will become even more attractive for commercial and industrial application fields.

Progress in Simulator-Based Tuning—The Art of Tuning Space Mapping [Application Notes]

Abstract: We discuss tuning space mapping (port-tuning) techniques that can significantly reduce time and effort for design closure. We elaborate on various possible approaches. We distinguish between Type 1 and Type 0 embedding to indicate how tuning elements may be introduced into EM simulations to form suitable tuning models or surrogates. We optimize and update such surrogates iteratively to predict good EM designs. We illustrate the techniques using a simple bandstop filter and demonstrate their power using more complex filter design examples. Finally, we discuss from a physics point of view the possible locations of cuts, the effects of the cutting and reconnection, and we compare models that employ internal cuts with models that consider combinations of submodels.

Nanoelectronics in Radio-Frequency Technology

Abstract: In this article we have attempted to give an overview of the impact of nanoelectronics on RF technology. Today the development of nanoelectronics is highly market driven since the push for progress requires tremendous investments. The continuous technological progress in CMOS technology, following Moore's law and the extensions more and more than certainly offers large room for progress, however, saturation already appears on the horizon. Long-term research and development in direction of novel materials, novel technologies, and novel device concepts is of great importance to maintain the competitiveness of electronics industry. Novel devices based on novel materials and novel technologies will be required to go beyond Moore. Even circuit and system paradigms will change. The next 20 years of development of nanoelectronics will be extremely challenging and will be decisive for the fate of the global players in the field. Although the reflow of investment can be expected only over a long period of time a strong engagement in research and development will be mandatory.

Integrated Test for Silicon Front Ends

Abstract: Silicon-based technologies have enabled the monolithic integration of transceiver circuits with operational frequencies up into the millimeter-wave regime. While high integration relaxes the requirements on RF chip-to-chip interconnects and external circuitry, it imposes serious challenges upon the traceability of failure mechanisms and functional errors of the individual building blocks that comprise the front-end. Additionally, expensive external measurement equipment in combination with complex, error-prone, and time-consuming calibration procedures, necessitates the development of on-chip test modules. It has been shown that a variety of built-in test schemes are currently the topic of research for both the mixed-signal and microwave domain. Solutions for the individual building blocks that will enable direct verification of performance parameters have been presented throughout this article. Current RF transceiver architectures will require a mixture of both paradigms for successful implementation of integrated test strategies. It is the authors' belief that the application of such concepts is a must for future integrated transceiver systems to meet the stringent requirements of time-to-market and low-cost of mass market consumer products.

Nanoelectronics-Based Integrate Antennas

Abstract: Nanoelectronics is the gateway to a variety of novel electronic devices and systems with substantially new properties. It enables the development of nanoscale electronic devices, covering radio frequencies in the terahertz range and beyond up to optical frequencies. The on-chip integration of antennas opens new vistas for novel devices and integrated systems for sensing, detection, wireless communications, and energy harvesting applications. However, the requirements of antenna integration into the chip architecture are different from those of circuit integration. Nanoelectronic technologies strike a compromise between these requirements.

Thermal Noise and Noise Measurements—A 2010 Update

Abstract: We have presented a close look at effects of order hf/kT in noise measurements and in the definition of noise quantities-noise temperature, noise figure, etc. Given the perennial push to higher frequency, lower noise, and smaller uncertainty, such effects are becoming significant in an increasing number of applications, and especially in radio astronomy where the noise temperature of a modern receiver can be within a factor of a few of the quantum limit. In particular, we have discussed issues arising from the definition of noise temperature and the treatment of contributions from vacuum fluctuations. There is more than one correct way to deal with these effects, but it is important to be consistent in one's approach and not to mix methods.

Speed It Up

Abstract: GPUs are cost-effective solutions for hardware acceleration of the FDTD algorithm. The acceleration of FDTD on GPUs has made the algorithm more available and affordable with endless possible applications. Hardware acceleration has brought the power of supercomputing to the desktop.

Keeping Time with Maxwell's Equations

Abstract: Introducing a commercial FETD solver breaks new ground in EM field simulation. Based on the DGTD method, it allows unstructured geometry-conforming meshes to be used for the first time in transient EM field simulation. Since the underlying method doesn't require the solution of a large matrix equation, its computer memory usage is modest. Simulation speed is optimized without compromising accuracy or stability by introducing an innovative local timestepping procedure. In this procedure, small time steps are taken only where needed in small mesh elements while appropriately larger time steps are used in larger mesh elements. Furthermore, a local implicit time-stepping algorithm is employed with selected elements to further improve simulation speed. DGTD is a competitive alternative to traditional FDTD-based methods to solving Maxwell's equations in the time domain. The applications presented here include the electromagnetic pulse susceptibility of the differential lines in a laptop computer, the radar signature of a landmine under undulating ground,the TDR of a bent flex circuit, and the return loss of a connector. All of these examples involve complicated/ curved geometries where the flexibility of the unstructured meshes used in DGTD provides powerful advantages over simulation by conventional brickshaped FDTD and FIT meshes.

Microwave Noise and FET Devices

Abstract: In this article, a short presentation of available FET technologies (GaAs MESFET, ΠI-V HEMT, and silicon CMOS) has been presented. Why minimum NF is suitable to benchmark different low-noise technologies has been discussed. Following this, basic concepts related to thermal noise in FETs and the reason why such technologies feature outstanding low-noise performance was illustrated/ and a short survey of minimum NF evolution has been presented. InP HEMT technology undoubtedly constitutes the best low-noise technology (especially to address applications in W or G Band). The noise performance of silicon MOSFET technology/ which is widely used in many applications because of its low cost, does not outperform that of GaAs pHEMT technology/ unless channel engineering is performed.

GaN Comes of Age

Abstract: GaN is now providing solid-state power amplifiers of higher efficiency, bandwidth, and power density than could be achieved only a few years ago. Novel circuit topologies combined with GaN's high-voltage capabilities and linearization are allowing GaN high-power amplifiers to simultaneously achieve both linearity and record high efficiency. GaN high-power amplifiers have been produced with more than 100 W of power over multioctave bandwidths and with PAEs of more than 60%. Narrower-band high-power amplifiers have been produced with PAEs of more than 90%.

Nanoscale Devices for Large-Scale Applications

Abstract: In this article, the authors review the progress toward carbon nanotube based electronics and consider the implications for application of nanotubes in analogue RF devices and RF system applications as well as recent prospects in printed electronics, especially printed RFID tags. The author also points out that nanowire devices are also starting to show similar performance in the RF domain, with similar manufacturing challenges.