bluuebunny/crossref_metadata_2025 huggingface dataset:
Fournier's Gangrene: From Diagnosis to Reconstruction
Authors: Rafik Amine , Taqafi Samira , Diouri Mounia , Bahechar Naima , Chlihi Abdessamad , Halfya Ayoub , Elmourtaji Khalid , Rabii Redouane , Meziane Fethi
Published: April 2019

Fournier gangrene (FG) is an acute and potentially fatal infection of the scrotum, perineum, and abdominal wall. It is characterized by necrotizing fasciitis with loss of subcutaneous tissue and skin. Although originally thought to be an idiopathic process, FG has been shown to have a predilection for patients with diabetes as well as long-term alcohol misuse; however, it can also affect patients with non‐obvious immune compromise. Twenty patients were admitted to our hospital with the diagnosis of Fournier gangrene, between 1 January 2011 to January 2013.

The epidemiological characteristics, evolution and treatment modalities were reviewed. Early surgical debridement of necrotic tissues and antibiotics are fundamental in the treatment of FG. Scrotal reconstruction with skin grafts or flaps is fundamental to improve the quality of life and provides social reinsertion.
Sexual Assault of Nigerian Female Adolescents: A Review of the Trend and Effects
Authors: Eyong E. M. , Emechebe C. I.
Published: April 2019

Introduction: Adolescent sexual assault is a huge public health problem with physical, reproductive health and psycho-social consequences.

Methods: A literature review was carried out on its prevalence, forms, risk factors and effects using multiple databases, namely MEDLINE, Web of Science Core Collection, and Google Scholar Google search. Additional information was from medical textbooks and journals.

Results: The estimated prevalence of sexual aggression among adolescents varied widely in different studies in Nigeria, ranging from 6 to 74%. Broad variation may be due to different incident reporting rates at multiple locations.

Conclusion: The solution to this problem involves the mobilization and active co-operation of all stakeholders in the society such as parents, guardians, teachers, non-governmental organizations, religious leaders, political leaders and government. Sex education should be given at home, school and other settings to both males and from other formal sources.
Double Perforated Kissing Ulcers of Duodenum: A Brief Report
Authors: Triantafyllou Tania , Nikolaos Kokoroskos , Joanna Papailiou , Dimitrios Linardoutsos , Georgios Zografos , Dimitrios Theodorou
Published: April 2019

Helicobactor pylori infection has been associated with peptic ulcer disease and is currently treated with proton pump inhibitors (PPIs), which have reduced the complications of the disease. Perforation of either a gastric or duodenal ulcer is rarely treated with surgery. We report the case of double-perforated synchronous duodenal ulcers, which is an extremely infrequent condition. To our knowledge, no English case reports have yet been published. Therefore, awareness of the physician in the field of diagnosis and treatment of this peptic ulcer is required. We report the case of a 46-year-old male patient who presented with acute abdominal pain at the emergency surgical department of our hospital. According to patient history, smoking, alcohol consumption, and frequent postprandial abdominal pain were noted. A physical examination revealed a rigid abdomen and tachycardia, and the temperature was 37.8°C. Laboratory testing showed increased levels of leukocytes, and free subdiaphragmatic air was found in the chest X-ray. Due to rapid deterioration of his clinical condition, the patient underwent urgent surgery. An explorative laparotomy showed 2 perforated kissing ulcers at the first segment of the duodenum, in the anterior and posterior walls. A peripheral gastrectomy was performed. Postoperative follow-up did not result in any complications. In regard to this case we present, simultaneous perforation of two synchronous duodenal ulcers is an uncommon but possible incident of which the clinician should be aware. To our knowledge, this is the first case published in the literature.
Analysis of Mutational Spectra in Metastatic Colorectal Carcinoma: KRAS as an Indicator of Oxaliplatin-Based Chemotherapy
Authors: Chang Chu-Cheng , Lin Jen-Kou , Lin Tzu-Chen , Chen Wei-Shone , Jiang Jeng-Kai , Yang Shung-Haur , Wang Huann-Sheng , Lan Yuan-Tzu , Lin Chun-Chi , Chang Shih-Ching
Published: April 2019

Objective:

Mutation spectra in colorectal cancer with metastasis and its response to chemotherapy.

Summary of Background Data:

No molecular markers are available for selecting the optimal chemotherapeutic regimen (irinotecan or oxaliplatin) for metastatic colorectal cancer (mCRC).

Methods:

We enrolled 161 mCRC patients who underwent surgery for their primary tumors at Taipei Veterans General Hospital from 2004 to 2010. The prevalence of gene mutations was measured and correlated with responses to different cytotoxic agents.

Results:

We detected 1,836 mutations in 12 genes. KRAS mutants affected 44.3% of the tumors. The rate of good response was insignificantly higher for patients with KRAS mutant tumors who received oxaliplatin-based chemotherapy compared with patients with KRAS wild-type tumors (65.6% versus 47.0%; P = 0.15). For patients who received irinotecan-based chemotherapy, the rate of good response was similar in patients with wild-type (55.0%; n = 11) and those with KRAS mutant tumors (54.5%; n = 12; P = 1). In patients with KRAS mutant tumors treated with an oxaliplatin-based regimen, the overall survival was 38.5 months (95% CI: 26.6–50.5 months), which was insignificantly better than that for patients treated with an irinotecan-based regimen (30.4 months; 95% CI: 15.8–45.1 months; P = 0.206).

Conclusions:

Our data could not come to the conclusion that patient with KRAS mutation mCRC may have better response with oxaliplatin-based first-line chemotherapy. Further study is needed to confirm the relationship between gene mutation and chemotherapy response.
Rectal Cancer With Distally Spreading Intramural Metastasis: A Case Report and Review of the Literature
Authors: Yanagisawa Kiminori , Takahashi Hidekazu , Miyoshi Norikatsu , Haraguchi Naotsugu , Nishimura Junichi , Hata Taishi , Matsuda Chu , Yamamoto Hirofumi , Mizushima Tsunekazu , Doki Yuichiro , Mori Masaki
Published: April 2019

Introduction:

Intramural metastasis (IM) is common in esophageal cancer, and it is an important factor in determining the resection area and tumor malignancy. However, IM is rare in rectal cancer; therefore, little is known about IM in rectal cancer, and the clinical significance remains unclear.

Case Presentation:

We describe a case of rectal cancer with distally spreading IM. A 58-year-old man consulted a primary care physician, with a chief complaint of constipation; tests revealed a high carcinoembryonic antigen value. A colonoscopy revealed a type 2, advanced rectal tumor, which covered two-thirds of the circumference of the upper rectum. In addition, 3 protruding lesions were observed under the normal mucosa on the anal side of the primary tumor. A laparoscopic low anterior resection was performed. Pathologic findings showed that the primary tumor was a moderate-to-well-differentiated adenocarcinoma with a cribriform structure. The 3 lesions on the anal side found under normal mucosa were separate from the primary tumor, but morphologically similar to the primary adenocarcinoma; therefore, these were diagnosed as IMs. Based on a review of previous case reports, rectal carcinomas were often accompanied by vascular invasions and lymph-node metastases. Moreover, in rectal cancer, tumors with IMs often show vascular invasion. Therefore, we assumed that IM could be a marker of poor prognosis.

Conclusion:

This study revealed that, in surgery, detection of a distally spreading IM is an important finding for determining the optimal surgical resection margin.
FINANCIAL KNOWLEDGE, FINANCIAL WELLBEING, AND ONLINE SHOPPING ADDICTION AMONG YOUNG INDONESIANS
Authors: Tanoto Sherly , Evelyn Evelyn
Published: April 2019

With the recent booming of e–commerce business in Indonesia, it is essential to conduct further studies on online shopping behavior of Indonesians. Past studies on online shopping addiction emphasize only psychological factors and overlook financial factors. To fill this research gap, this study aims to examine the association and effect of financial knowledge and financial wellbeing on online shopping addiction. The Bergen Shopping Addiction Scale (BSAS) was adopted to assess online shopping addiction whilst financial knowledge and financial wellbeing scales from Australian Unity were used to measure the other two research variables. Data was collected through an online survey of 230 young Indonesians. To analyze the data, Pearson correlation and multiple regression techniques were implemented. Outcomes of this study revealed that most respondents had medium and high levels of financial knowledge and financial wellbeing. Interestingly, addictive respondents showed high financial knowledge and financial wellbeing. Financial knowledge and financial wellbeing were positively related to online shopping addiction. Financial wellbeing was a better predictor because it might be possible that individuals with positive feelings on their financial conditions were more comfortable in increasing their online spending behavior. The results of this study provide insights for future studies and e–commerce owners.Keywords: Online shopping addiction, financial knowledge, financial wellbeing.
APOLOGY AND COMPENSATION STRATEGY ON CUSTOMER FORGIVENESS AND NEGATIVE WORD OF MOUTH
Authors: Bakar Resekiani Mas , Hidayati Nurul , Giffani Inastuti Retno
Published: April 2019

The service provider could not totally guarantee the service process without any failure at all. This study aims to measure the influence of service recovery strategy towards customer forgiveness and negative word-of-mouth (WOM) as the effect of service failure. The service recovery strategy is performed in three types of vignette: apology, compensation, and apology-compensation. Vignette was given to 94 participants who have encountered service of airline. The result of ANOVA shows that apology compensation achieves the highest score relates to forgiveness. The interesting result of this study shows that even the customers forgive the service provider due to the service failure they did, this cannot diminish the intention of negative WOM. This study offers an implication to the company in order to pay attention regarding the compensation and the spread of negative WOM to the other customers
CLUSTER ANALYSIS OF FINANCIAL BEHAVIORS AND PREFERENCES AMONG THE BOTTOM OF THE PYRAMID GROUP
Authors: Saraswati Dewi , Kusumaningrum Dian
Published: April 2019

This study investigates the financial behavior and preferences of the bottom of the pyramid (BOP) group, and thus, contributes to the financial inclusion demand-side literature. A survey of 100 households was conducted. A cluster analysis was used to analyze the data and portray the characteristics of the BOP. Further analysis was conducted using chi-square and ANOVA tests. The results reveal three sub-groups within the BOP which consists of the very low, low, and medium. Financial behaviors are found to be indifferent among the sub-groups, except for savings allocations and financial planning. Households with a better economic condition are found to have a higher attention to use banking services. The financial literacy category indicates different attitudes in conducting long-term financial planning and service preferences. This result implies that financial literacy and adequate financial products are beneficial towards the financial inclusion of the BOP group.
LIFESTYLE AND CONSUMER PREFERENCES IN CHOOSING LOCAL OR FOREIGN BRANDS: A STUDY OF CONSUMER BEHAVIOR IN SURAKARTA – INDONESIA
Authors: Haryanto Budhi , Febrianto Awang , Cahyono Edi
Published: April 2019

This study discusses the relationship between lifestyle and individual preferences in choosing local or foreign brands. The sample consisted of 250 people, taken randomly through surveys in several public places in Surakarta - Indonesia, including the department stores, traditional markets, or other public areas, where many people were there and were willing to become research participants. Fur­thermore, the collected data is processed using factor analysis to reduce lifestyle dimensions, and logistic regression analysis is used to explain the relationship between lifestyle dimensions and pre­ferences in choosing a local brand or foreign brand, in this case represented by Wong Solo Grilled Chicken (WSGC) or Kentucky Fried Chicken (KFC).The test results indicate 13 dimensions of lifestyle, and only 5 dimensions are significantly related to brand preference: (1) individuals who have a fashion consciousness lifestyle tend to choose KFC rather than WSGC, (2) individuals with health consciousness lifestyles tend to choose WSGC rather than KFC, (3) individuals with leadership lifestyles tend choosing KFC rather than WSGC, (4) individuals with attentiveness lifestyle tend to choose WSGC rather than KFC, and (5) individuals with extroversion lifestyles tend to choose KFC rather than WSGC. This study also discusses the implications of studies related to the contribution of theory, practitioners, and possibilities for future studies
THE VIEWS OF THE TOURISM VILLAGE MANAGERS ON THE GREEN EVENT CONCEPT IN BALI
Authors: Dwiatmadja Christantius , Astawa I Putu , Sukawati Tjokorda Gde Raka
Published: April 2019

Green event remains an issue under debate in the effort to support sustainable tourism today, because the result of the previous research has not found a standard model for the implementation of the green event concept. This research describes the views of the village tourism managers on the green event model developed by the Bali State Polytechnic. Green events are developed on the basis of two aspects: green and cultural aspects. Data were collected through questionnaires sent by email and by post to village tourism managers. There are a hundred tourist villages planned to be developed in Bali and all are made research samples. The collected data were analyzed by using descriptive statistics. The results of the study indicate that the understanding of green aspects includes green foods, waste management, natural materials, and ecosystem is averagedly quite good. The result of the analysis from the cultural aspect is very good, meaning that the culture practised  by the community gives a strong impetus to keep the environment sustainable so that the harmonious relationship with nature, humans, and God is maintained through the activities in Tourism Villages. Other results indicate that an understanding related to the ecosystem, the green food, and the waste management needs a special attention to further improve understanding. Green event as an alternative product in supporting the tourist village is very much expected by the managers that will further be synergized with the existing culture. The combination of both green event and existing culture is quite unique and will constantly keep the concept of sustainable tourism. These findings give a contribution to the theory of green tourism or sustainable tourism which is built upon the event and based on the blend of modern and traditional concepts. Keywords: green event,  sustainable tourism,  tourism village, culture
ANALISIS IDENTITAS MEREK, LOYALITAS MEREK, CITRA MEREK, DAN KEPERCAYAAN MEREK TOYOTA
Authors: Zebuah Ade Jermawinsyah
Published: April 2019

Consumer needs in vehicles is increasing, it triggers any car companies to create great brand identity in order to gain brand trust from consumen. Perception of brand from consumen is affect to gain brand trust which is have great deal to brand loyalty. This research is aiming to analyze the influence of brand identity on brand loyalty with brand image and brand trust as an intervening variable. This research will be done by distributing 100 questionnairs to the respondents who have buy or used Toyota. Analysis techniques that will be used is quantitative analysis with Smart-PLS method. Research shows that brand identity influences brand image, but has no influences to brand trust, brand image influences brand trust. Also brand image and brand trust influences loyalty of Toyota’s brand.
PENGARUH STORE LAYOUT DAN FOOD QUALITY TERHADAP MINAT BELI ULANG DAN CUSTOMER SATISFACTION PADA READY TO EAT BAKERY
Authors: Pambudi Amadea Rahma
Published: April 2019

Penelitian membahas pengaruh dari store layout dan food quality terhadap minat beli ulang dengan memper­timbangkan faktor customer satisfaction (Fulfillment, Pleasure, Ambivalance) pada ready to eat bakery Surabaya. Sampel penelitian ini berjumlah 100 responden pelanggan ready to eat bakery Surabaya. Hasil penelitian ini menunjukan bahwa store layout (X1) dengan dimensi alokasi luas ruangan yang tepat (X1.1) tidak berpengaruh signifikan terhadap customer satisfaction (Y), food quality (X2) dengan dimensi presentation (X2.2) berpengaruh secara positif dan signifikan terhadap customer satisfaction (Y), dan customer satisfaction(Y)dengan dimensi pleasure (Y1.2) berpengaruh secara positif dan signifikan terhadapminat beli ulang (Z) dengan dimensi minat transaksional (Z1.1).
BRAND IMAGE, CUSTOMER SATISFACTION DAN CUSTOMER LOYALTY JARINGAN SUPERMARKET SUPERINDO DI SURABAYA
Authors: Semuel Hatane , Wibisono Julian
Published: April 2019

Penelitian ini untuk mengetahui pengaruh Brand Image pada Kepuasan Pelanggan dan Loyalitas Pelanggan pada Supermarket  Superindo di Surabaya. Unit analisis adalah pelanggan Supermarket  Superindo. Penelitian menggunakan 100 responden pelanggan dengan umur lebih besar atau sama dengan 18 tahun, dan pernah berbelanja dalam tiga bulan terakhir pada salah satu supermarket Superindo di Surabaya. Sampel dipilih dengan metode non probability sampling melalui online dengan menggunakan google form.  Analisis data menggunakan Partial Least Squares (PLS). Hasil penelitian menunjukkan bahwa Citra Merek berpengaruh positif secara langsung kepada Loyalitas Pelanggan, juga Citra Merek berpengaruh terhadap Kepuasan Pelanggan. Selanjutnya Kepuasan Pelanggan berpengaruh positif terhadap Loyalitas Pelanggan, serta penelitian ini membuktikan juga bahwa Kepuasan Pelanggan dapat merupakan mediasi antara pengaruh Citra Merek terhadap Loyalitas Pelanggan
PENGARUH KUALITAS PELAYANAN DAN KEPUASAN NASABAH TERHADAP LOYALITAS NASABAH PT. BANK INDEX LAMPUNG
Authors: Octavia Ria
Published: April 2019

Tujuan dari penelitian ini adalah untuk mengetahui pengaruh kualitas pelayanan terhadap loyalitas nasabah, kualitas pelayanan terhadap kepuasan nasabah, kepuasan nasabah terhadap loyalitas. Dalam penelitian ini mengukur dampak kualitas pelayanan terhadap loyalitas secara langsung. Penelitian ini merupakan penelitian konfirmatori yaitu penelitian yang bertujuan untuk mengetahui apakah ada hubungan antara variabel yang telah dikembangkan dari penelitian sebelumnya dengan fakta atau kejadian aktual di lapangan. Populasi target dalam penelitian ini adalah pelanggan PT. Indeks Bank Kantor Cabang Lampung. Sampel diambil 150 orang dengan menggunakan teknik purposive sampling. Alat analisis yang digunakan untuk menguji hipotesis ini menggunakan analisis dalam Structural Equation Model. Hasil penelitian ini menunjukkan bahwa kualitas pelayanan berpengaruh terhadap kepuasan nasabah, kualitas pelayanan tidak berpengaruh langsung terhadap loyalitas nasabah, dan kepuasan nasabah berpengaruh terhadap loyalitas nasabah
Dual‐ and Multi‐Frequency Microstrip Antennas
Authors: Lee K.F. , Luk K.M. , Shum Y.H.
Published: November 2024

A number of techniques for dual‐band or multiband operation of microstrip antennas are available in the literature. This article introduces the operation principles and design guidelines of several popular methods, including the multimode‐operated patch, stub‐loaded patch, slot‐loaded patch, stacked patch, and coplanar patch antenna. Their relative performances are compared both theoretically and experimentally. One important purpose of the article is to provide physical insight to readers for further development of multiband microstrip antennas, which are attractive for modern wireless applications.
Microstrip Antennas, Broadband
Authors: Luk K. M. , Mak C. L. , Chair R. , Wong H. , Lee K. F.
Published: November 2024

With <1% in bandwidth, the first microstrip patch antenna has limited applications, mainly for defense purposes. With tremendous effort dedicated to the bandwidth enhancement of microstrip antennas, they are now becoming the most popular antennas selected for modern wireless communications. This article collects different approaches for enhancing the bandwidth of microstrip antennas, including the stacked‐patch, U‐slot patch, and L‐probe coupling techniques. Emphasis is placed on the L‐probe technique, which is demonstrated to be attractive for the development of wideband dual‐polarized patch antennas, and wideband miniature patch antennas for state‐of‐the‐art mobile communications. Throughout the article, design guidelines and principles of operation for most of the designs are highlighted.
Photonic Bandgap (PBG)
Authors: Martínez Alejandro , Griol Amadeu , Sanchis Pablo , Martí Javier
Published: November 2024

Photonic bandgap materials are expected to play an important role in the near future mainly because of their potential capability to provide extremely compact optical circuits. A large variety of applications have been proposed and demonstrated in both the microwave and optical regimes. In this way, the microwave regime has become a useful instrument to experimentally demonstrate applications initially proposed for the optical domain, thanks to the scaling properties of the Maxwell equations and the easier and cheaper fabrication and testing capabilities of the fabricated structures compared to their optical counterparts. This can be illustrated by the fact that the first photonic bandgap structures were developed to work at microwave frequencies. Photonic bandgap structures have also attracted interest for microwave applications in themselves, and several proposals of electromagnetic bandgap techniques and circuits aimed at improving the properties of current microwave and millimeter‐wave devices have been reported.

The concept of photonic bandgap is so wide that it becomes unapproachable to summarize all the knowledge related to this field in a few pages. Thus, although a general vision of the field is offered to the reader, we have focused our efforts on passive microwave components and devices that make use of the principles of photonic bandgap.

We start this chapter with a brief historical introduction and a description of photonic bandgap fundamentals. Then, we first summarize some typical functionalities employed in passive optical devices (waveguides, directional couplers, Y junctions, and interferometers), which are tested at microwave frequencies by using a photonic bandgap structure based on alumina rods. The obtained results allow us to visualize a near‐future implementation of the proposed devices using photonic bandgap technology in the optical domain. In a second step, we show how the photonic bandgap concept can be applied to a very extended microwave technology, specifically microstrip technology, and describe and experimentally demonstrate some applications such as novel filter structures and harmonic suppression in microstrip bandpass filters based on coupled rings. Finally, a brief summary of the application of photonic bandgap structures in the optical regime is drawn.
Television and FM Broadcasting Antennas
Authors: Bendov O.
Published: November 2024

Antennas for television and FM broadcasting are usually installed on tall towers to maximize the service area. A high‐power transmitter feeds the broadcast antenna to provide “passable” picture and sound at distances approaching 70 m. In the UHF range (TV channels 14 to 69), the transmitter's peak power could be as high as 280kW. In the VHF range (TV channels 2 to 13 and FM), a transmitter's peak power of 70kW is not unusual. In addition to high power‐handling capability, broadcast antennas must continue to perform under severe weather conditions, such as ice storms and hurricane winds. Antennas, especially for television broadcasting, must be designed to accept and radiate all of the power delivered by the transmitter. Antennas for digital television must be designed to meet more stringent specifications than those for antennas for analog television.
Oscillator Design
Authors: Mathis Wolfgang , Russer Peter
Published: November 2024

The behavior of electronic oscillators can be studied completely only if nonlinear circuit models are utilized. In this article the main fundamental aspects of analytical as well as numerical methods for analyzing oscillatory circuits are reviewed. First, electronic oscillators are modeled as nonlinear dynamical systems and analytical perturbation methods and bifurcation theory (e.g., Andronov–Hopf bifurcation) are used to analyze sinusoidal as well as relaxation oscillators. Then the theory of noise in oscillatory circuits is discussed. In the second part of the article state‐of‐the‐art methods for the numerical analysis of deterministic and noisy oscillators are presented. In almost all sections original results of the authors are included. The methods are illustrated by means of a few examples.
Frequency Modulation
Authors: Fertig L. B. , Mc Clellan J. H.
Published: November 2024

In this article, concepts relating to instantaneous frequency, along with algorithms for its computation, are reviewed. First, several means by which instantaneous frequency is commonly defined are discussed, and the relationships between instantaneous frequency and time–frequency distributions are explored. Next, several measures of performance commonly used to evaluate instantaneous frequency algorithms, such as the Cramer–Rao lower bound, are examined. Finally, a number of algorithms that have been suggested for IFE are summarized. Despite the relative maturity of frequency modulation in the field of radiocommunications, the field of IFE is a growing one, and one in which research is still quite active.
Local Area Networks (LAN)
Authors: Evans Joseph B.
Published: November 2024

Local Area Networks (LANs) are data communications networks within offices, homes, or areas as large as campuses. LANs are based on physical technologies ranging from copper wiring and optical fiber to radio systems. There are a number of commonly used and emerging LAN technologies that offer the opportunity to connect computers and all manner of devices such as sensors and instruments to increasingly pervasive networks.
Volterra Modeling in Analog, RF and Microwave Engineering
Authors: Steer Michael B. , Gharaibeh Khaled M.
Published: November 2024

Volterra techniques are used in radiofrequency (RF) and Microwave engineering primarily in modeling the inputoutput characteristics of nonlinear circuits and systems that operate with limited bandwidth signals. Volterra models capture frequency‐dependent effects within the band. Two forms of the Volterra model exist; one being in the time‐domain invoking Volterra kernels in what is in effect a multidimensional convolution; and the other being a frequency‐domain form with what are called Volterra nonlinear transfer function akin to the transfer functions of linear circuits but, of course, extended to handle nonlinearities.
Ge‐Si Alloys and Devices
Authors: Russer Peter , Luy Johann-Friedrich
Published: November 2024

The silicon–germanium heterojunction bipolar transistor enabled the breakthrough of siliconbased MMIC (monolithic millimeter‐wave integrated circuit) technology [1,6]. Amplifiers and tunable oscillators or with maximum operation frequencies beyond 80GHz become feasible.

Silicon as a substrate for millimeter‐wave monolithically integrated circuits was suggested in 1981 by RCA [22]. Since 1986 in the field of silicon monolithic millimeter‐wave integrated circuits (SIMMWICs) there have been research activities at the former AEG‐Telefunken Research Institute (now DaimlerChrysler Research Center) and at the Technische Universitat¨ München [23–29].

Monolithic integrated millimeterwave circuits based on silicon and SiGe will give new options for millimeter‐wave sensor and communication applications.
III–V Semiconductors
Authors: Snowden Christopher M.
Published: November 2024

This article provides a broad introduction to III–V semiconductors as a background to device and circuit technologies that use these materials. The reader is introduced to theoretical and practical concepts for this range of alloy semiconductors. The physical and chemical properties and behavior of these materials are discussed. Methods of growing epitaxial layers and fabricating microwave and RF devices are presented. A brief summary of the microwave applications of III–V semiconductors is included together with an overview of the state‐of‐the‐art performance.
Radar Remote Sensing
Authors: van Zyl Jakob J. , Kim Yunjin
Published: November 2024

In this article, we present the basic principles of how remote sensing radars work. These include SARs (synthetic aperture radar), scatterometers, altimeters, sounders, cloud radars, and rain radars. Radars are active sensors; they provide their own illumination and therefore can be operated during day or night. An additional advantage of particularly lower‐frequency radars is their ability to penetrate clouds, rain, tree canopies, and even dry soil surfaces. We start the discussion by defining the basic concepts of resolution, the radar equation, signal fading, and the geometric distortions associated with the radar imaging geometry. We also include a description of advanced SAR techniques (polarimetry, interferometry, and polarimetric interferometry) and their applications. We complete the chapter by briefly examining nonimaging radars such as scatterometers, altimeters, radar sounders, and meteorological radars. An extensive list of references is provided for each radar for readers who need an in‐depth description of a particular radar.
Buried Object Detection
Authors: Türk Ahmet Serdar , Hocaoglu Ali Köksal
Published: November 2024

The subsurface detection and identification of the buried geologic and synthetic (human‐produced) structures is currently an important research area. The scope of the problem is very complex and covers a wide range in applications. One area of the research includes the detection of a large metallic gas pipe buried in a deep or small plastic mine laid just beneath the ground. The size, geometry, constitution and depth of the target object and the characteristics of the medium (wet soil, sand, etc.) can be considered as the principal parameters for the detector designs. In this article, different sensor technologies based mainly on electromagnetic, acoustics, infrared, or chemical theories are discussed.
Multiple‐Access Schemes
Authors: Sidi Moshe
Published: November 2024

Multiple access schemes are natural not only in communication systems but also in many other systems such as computer systems, storage facilities, or servers of any kind, where resources are shared by a number of nodes. In this article we address mainly shared communication channels.

The goal of this article is to survey typical examples of multiple access schemes. These examples include TDMA, FDMA, Aloha, polling, and tree‐based schemes. The allocated space for the topic of multiple access schemes in the encyclopedia (which is yet another shared resource) is just too tiny to include all the ingenious multiple access schemes that have been designed by researchers over the years.
Radio‐Frequency Identification Systems (RFID)
Authors: Hayashi Hitoshi
Published: November 2024

Radiofrequency identification system (RFIDs) can provide an automatic means of collecting identification data for people, animals, and objects. Furthermore, with the advent of Internet systems, RFID systems are expected to further expand into new ubiquitous applications. In this article, we present a brief introduction to RFID systems.
Measurement of Near Fields Using a Modulated Scatterer
Authors: Gardiol Fred
Published: November 2024

In the close vicinity of an electronic device or of an antenna, the electric and magnetic fields often exhibit a complex behavior, and a good knowledge of the resulting field pattern would be a most valuable asset for many practical applications. But when one inserts a probe antenna connected to a receiver, close to the the device, one modifies the filed, because metal locally short‐circuits the tangential electric field components.

The modulated scatterer technique provides an indirect approach to determine field components, by introducing a small “scatterer” that does not perturb as much as a receiving probe would. The signal returned by the scatterer is very small, and to detect it one “modulates” the scatterer and then uses coherent detection. The amplitude and the phase of the field components are then determined.
Wavelength Meter
Authors: Guy Martin , Latrasse Christine , Villeneuve Bernard , Têtu Michel , Tremblay Pierre
Published: November 2024

Wavelength meters are instruments designed to measure the wavelength of an electromagnetic wave. Electromagnetic waves are the classic way to represent modifications of the space surrounding a moving electrically charged body. Time‐varying electric and magnetic fields are produced and can be sensed.Wavelength is a well‐established parameter when considering a monochromatic (single‐frequency) plane wave propagating in vacuum. It is the distance between two planes, measured along the direction of propagation of energy, where the phase and its derivatives have the same values.
Active Filters: Overview of Active Filter Structures
Authors: Billonnet Laurent , Jarry Bernard
Published: November 2024

This article is dedicated to an overview of existing active‐filter structures. We first talk about the different families of filters. We evaluate different ways of classifying microwave active filters (MAFs) and show that two main categories can be finally considered. For the first category, we describe, from a general point of view, various compensation techniques and detail more specifically filters based on the use of gyrators and negative‐impedance converters (NICs). In this step, we emphasize different problems that must be faced by RF and microwave designers in comparison to low‐frequency classical designs. The second category is based on filters resulting from the application, in the microwave domain, of methods and concepts used primarily at low frequency. As an example, this section sums up the different ways of considering and implementing recursive and transversal (R&T) filters for the microwave purpose.
Active Filters: Tools and Techniques for Active Filter Design
Authors: Billonnet Laurent , Jarry Bernard , Barelaud Bruno
Published: November 2024

In this article, we first discuss the use of CAD tools for microwave and RF filter design. We emphasize that, without any strong microwave design background and experience, optimization tools unavoidably lead to nonreproducible solutions. We then show the necessary implementation of analytical procedures to set and verify some essential characteristics of low‐noise active devices, with the examples of electrical stability criteria and noise performance calculation, prediction, and optimization. Section 2 deals with the description of tools and techniques for filter improvements. We begin with an extended consideration of compensation techniques based on response selectivity and circuit dimensions improvement. The technique is illustrated with the design of a one‐pole interdigital filter and a two‐pole coplanar filter whose response and size have been improved using this approach. We then generalise the principle to the active‐impedance profile (AIP ) technique, which is illustrated with the application to multistandard and pseudomultipole filters. Finally, novel approaches and new technologies for new microwave and RF communications needs are detailed. We confront GaAs processes to silicon‐based technologies in terms of processes themselves, and in terms of CAD tools, component implementation, compactness, relative size, and cost with two basic circuit examples. Migration to silicon‐based processes also involves novel implementation approaches, including differential circuits. This last approach is illustrated with experimental results.
Analytical and Adaptive Modeling of Nonlinear High Power Amplifiers
Authors: Ibnkahla Mohamed
Published: November 2024

High‐power amplifiers are used in modern communication systems for their high‐power efficiency. However, these amplifiers have generally nonlinear characteristics, leading to signal distortion and adjacent channel interference. We review the most popular analytical models for these nonlinear characteristics. A special focus is given to adaptive models—mainly neural network approaches—which have emerged as efficient tools for the modeling, identification, and characterization of nonlinear amplifiers.
Coplanar Stripline Transitions
Authors: Simons Rainee N.
Published: November 2024

RF and microwave circuit components can be realized with input/output ports using either balanced or unbalanced planar transmission lines. Interconnections between these components will require a balun or a transition to transform an unbalanced port to a balanced port. This article presents several baluns or transitions, that are of either the Marchand or double‐Y type.
Ferrite Circulators
Authors: Yung E. K. N. , Wang D. X. , Chen R. S.
Published: November 2024

The circulator is one of the elementary building blocks in radiofrequency and microwave circuits. It is used extensively in making basic devices for communications and radar systems. The latter are often used in broadband and high‐power rating systems at microwave and millimeter‐wave frequencies. It is, however, seldom found in consumer products because some of its functions can be performed by simpler and cheaper alternatives. However, interest in circulators has been revitalized with the emergence of mobile communications in recent years. As more and more users are accustomed to the freedom provided by cellular phones, communication without the constraint of an attached wire is considered as natural as breathing air. In addressing the ever‐increasing public demands, numerous wireless systems have been launched and more are coming. The most notable ones are wireless local‐area network, wireless local subscriber loops, and other high‐bit‐rate yet low‐error‐rate systems of data transmission. For these systems, the overlooked circulator enjoys a competitive edge as most active switches could not deliver the needed power rating and bandwidth at a reasonable price, especially those in the ultra high frequency band and beyond.
Hybrids and Couplers
Authors: Bhartia Prakash , Pramanick Protap
Published: November 2024

Hybrids and couplers are common components used in most microwave integrated circuits. This article deals with the fundamental theory of these devices together with their applications. In addition, design aspects of hybrids and couplers together with characteristics such as losses and improvement in directivity are discussed.
Low Noise Amplifiers
Authors: Nair Vijay
Published: November 2024

This article discusses the noise theory of silicon and GaAs devices and its application in microwave amplifiers. Discussions of small‐signal equivalent circuits, amplifier gain and stability criteria, gain, and noise figure circles are included. Narrowband and broadband amplifier design procedures and specific considerations are also explained. Low‐noise amplifier (LNA) design techniques and some LNA examples are also presented.
Microwave Ferroelectric Devices
Authors: Patel D. P. , Pond J. M. , Rao J. B. L.
Published: November 2024

Control of reactance in microwave circuits, devices, and systems is a common method by which the response of a microwave circuit such as a filter, resonator, or phase shifter can be tuned. Devices based on a class of voltagedependent non‐linear dielectrics known as ferroelectrics provide an alternative to semiconductor varactor diodes and ferrimagnetic components, which are the most common devices of this type.

This article describes microwave devices that exploit the variation of the ferroelectric's permittivity with applied DC electric field. The main feature of these “tunable” microwave devices is the change of their capacitance, impedance, or phase velocity. We will describe varactors, oscillators, tunable filters, and phase shifting devices.
Microwave Limiters
Authors: Kaul Roger
Published: November 2024

A microwave limiter is designed to allow low‐power signals to pass through it, while attenuating high‐power signals. Stated another way, microwave limiters are powerdependent attenuators that prevent intense microwave energy from interfering with susceptible microwave components in the latter stages of a cascade.

Many microwave limiter technologies have been investigated since the midtwentieth century. The solid‐state limiter, which was first designed using the varactor diode, today employs the Si pin (or PIN) diode because of the pins lower capacitance per unit area resulting in better thermal characteristics, in addition to the fact that it requires no external power supply. Also a MESFET‐based, MMIC‐compatible microwave limiter is being developed for integration with the low‐noise amplifiers common in MMIC designs. Furthermore, although gaseous limiters are widely used in high‐power radars as receiver protectors, ferrite limiters have not found the same wide use.
Slow Wave Structures
Authors: Wu Ke
Published: November 2024

The slow wave is a particular type of wave propagation, usually of the guided‐wave type, and it is described mostly in the frequency‐domain. Slow‐wave structures are wave‐guides or transmission lines in which the wave travels with a phase velocity equal to or less than a certain predesignated velocity of wave propagation. In other words, the slow wave should be interpreted relative to its fast‐wave counterpart compared with a velocity of reference, such as the speed of light in a hollow metallic waveguide. In this description, the slow‐ and fast‐wave‐guiding properties are simply characterized by a popular technical term called the effective permittivity, which may involve the effect of permeability if the relative permeability is not equal to one, even though the concept of a separate effective permeability is valid.
Stripline Components
Authors: Barrio-Garrido R. M. , Salazar-Palma M. , Sarkar T. K. , Adve R. S.
Published: November 2024

The fast spread of wireless and high‐speed communications brings the need for providing inexpensive and compact microwave circuits at very high frequencies. A promising approach is the development of the modern multilevel or three‐dimensional monolithic microwave integrated circuits (MMIC), printed circuit boards (PCB), and the new technologies for integration of millimeter‐wave systems like low‐temperature cofire ceramics (LTCC). In such environments, stripline‐like components play a key role and focus a great interest nowadays, because multilayer, embedded transmission line (ETL) based on stripline configurations originates from the three‐dimensional packages. Moreover, stripline is one of the preferred transmission lines in most of this environments because, among other advantages, radiation and dispersion are negligible and ground planes provide effective shielding. For example, in antenna feeding, stripline has probed to be a compact and effective solution. In filter applications, suspended striplines are extensively used by engineers because of their low unloaded Q‐factor. However, the multiconductor and multilayer structures present some complications derived from the shorting posts or via holes, spurious modes that result in crosstalk and losses, complex geometries, and so on. In many cases, it is necessary to find new design solutions to avoid parallel‐plate mode coupling, but full‐wave analysis becomes a complicated task. In this article, these issues are exposed, and both classic stripline components and new multilayer structures are presented. We discuss some design considerations, advantages and drawbacks, classic and new devices, and modern solutions recently reported for old and new necessities of the design and analysis of stripline configurations.
Waveguides
Authors: Vorst André Vander
Published: November 2024

In the electromagnetic spectrum, microwaves are the waves whose wavelengths are comparable to ordinary laboratory dimensions. Furthermore, smooth surfaces of good conductors form very perfect reflectors for them. As a consequence, an electromagnetic wave in a reflecting pipe is reflected back and forth from wall to wall, so that it can travel to large distances with small attenuation. Hence we have “waveguides” as transmission lines, dealing with electromagnetic fields in the inside of hollow regions, rather than outside wires for more conventional electric applications, or waves in free space as in optics, and the propagating electromagnetic field is confined to the finite region of the guide by reflecting walls. The present article reviews the basic theory and the different geometries used in the various applications of such hollow waveguides. It also reviews specific recent (as of 2003) developments, such as theoretical advances, waveguides with arbitrary cross section, and ridged and grooved waveguides.
Spaceborne Radar
Authors: Kwok Ronald , Yueh Simon H. , Fu Lee-Lueng
Published: November 2024

Here, we review three different applications of active microwave remote sensing that have contributed geophysical measurements on a scale and accuracy that surpass what could be accomplished with airborne or in situ observations. These are synthetic aperture radar interferometry, scatterometry, and altimetry. For each of these areas, we describe the measurement principle, the current technology, the applications, and give a brief look into the future.
Very High Frequency Range
Authors: Campbell Richard L.
Published: November 2024

The Very High Frequency (VHF) range extends from 30MHz to 300 MHz, which means that when a VHF sine‐wave signal is observed on an oscilloscope, the trace completes from 30 to 300 million cycles each second. The wavelength and frequency of VHF signals has a profound impact on the hardware we build to use these frequencies. The 30 to 300MHz frequency range has been popular since radio engineers first discovered how to reliably generate and amplify VHF signals during the 1930s. The VHF range has significant advantages for some common applications over higher and lower frequency ranges.
Dielectric Resonator Oscillators
Authors: Fusco Vincent F. , Dearn Andrew
Published: November 2024

A dielectric resonator (DR) can be used to form the stabilizing element in an oscillator. Dielectric resonator oscillators (DROs) are characterized by the following properties: high‐frequency stability, high efficiency, and low manufacturing cost. They also can be made to provide good temperature stability.

Two‐ and three‐terminal active devices exhibit phase noise characteristics at microwave frequencies. Oscillators constructed using these devices can have their phase noise behavior improved by the addition of a DR element.
Schottky Barrier Diodes and Their Applications
Authors: Davis W. Alan
Published: November 2024

Although times have changed, the Schottky barrier diode remains an important component in many systems because of its unique features.

The discussion will first focus on the origin of the energy bands and their relationship to the Fermi level. The simple theory is later modified by the barrier‐lowering effect and the presence of surface states. The reverse bias depletion capacitance and, subsequently, the forward current characteristics are determined. Equivalent circuit models are discussed that are useful for circuit design. Finally, some comments are made about recent progress in wide bandgap Schottky barrier diodes. The applications sections emphasize mixer design, as this seems to be the predominant use of Schottky devices.