Open access peer-reviewed chapter

# Introductory Chapter: Ultra-Wideband Technologies

By Albert Sabban

Submitted: April 8th 2021Reviewed: April 12th 2021Published: July 28th 2021

DOI: 10.5772/intechopen.97675

## 1. Introduction

Minimization of the size, cost, and weight of the UWB RF modules and antennas is achieved by employing MMIC, MIC and MEMS technologies. However, integration of MIC, MMIC and MEMS components and modules raise technical challenges such as efficiency, accuracy, and tight tolerances. Design consideration and tolerances that can be ignored at low narrow band frequencies cannot be neglected in the design of UWB integrated RF modules. Advanced RF design software, such as ADS, CST, HFSS and AWR, should be used to achieve accurate design of UWB microwave communication devices in mm-wave frequencies. Accurate design of microwave modules and antennas is a must in development of UWB systems. It is an impossible mission to tune microwave devices in the production line.

Design of wideband UWB RF modules, filters and antennas are presented in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]. Wideband RF technologies such as MIC, MIMIC and MEMS are presented in [1, 2, 3, 4, 5, 6, 7]. Wide band RF modules are crucial in the development of Direction finding, DF, systems. A fully integrated 10–40 GHz superheterodyne receiver frontend using a 40–46 GHz IF is presented in [8].

Wideband RF technologies are used to develop wideband RF modules such as frontends, active antennas and receiving and transmitting channels as presented in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15].

Communication and radar industry in mm wave are currently in continuous growth. The demand for wide bandwidth makes the Ka-band attractive for future commercial communication and radar industry. ADS, HFSS, AWR, and CST are system and electromagnetic software used to develop wideband RF systems, modules, and antennas, as presented in [16, 17, 18, 19].

## 2. MIC and MMIC microwave and MM wave technologies

Compact low cost UWB systems may be developed and manufactured only by using miniature MMIC and MIC components.

### 2.1 MIC-microwave integrated circuits devices

Communication RF devices and systems consist usually of connectorized modules (such us Mixers, Amplifiers, Filters, and circulators) connected by cables. Connectorized devices are not compact and have big volume. They suffer from high losses and high weight. Volume, weight, and losses may be reduced by using Microwave Integrated Circuits, MIC technology. Figure 1 presents a MIC Transceiver. MIC devices, standard MIC and miniature HMIC are well known types of MIC devices. Hybrid Microwave Integrated Circuit is named as HMIC device. In MIC design active and passive components are soldered or bonded to the dielectric substrate.

The capacitors, resistors and other passive elements are produced by using thin or thick film technology. A single level metallization for conductors and transmission lines is used in Standard MIC technology. Multilevel process in which passive elements such as inductors, resistors, capacitors, and passive attenuators are batch deposited on the substrate in Miniature HMIC technology. Active components such as mixers, amplifiers and diodes are soldered or bonded on the substrate.

### 2.2 MMIC- monolithic microwave integrated circuits

MMIC are circuits in which passive and active elements are generated on the same dielectric substrate, as presented in Figure 2, by using a deposition scheme as epitaxy, ion implantation, sputtering, evaporation, and diffusion. The layout of the MMIC chip in Figure 2 consists passive and active elements such as resistors, capacitors, inductors and FET, Field Effect Transistor.

#### 2.2.1 MMIC design features

MMIC components cannot be tuned. Accurate design is crucial in the design of MMIC circuits. Accurate design may be achieved by using 3D electromagnetic software such as ADS and HFSS.

### Table 4.

MMIC COST.

MMIC Applications

• Ka band satellite communication.

• 60GHz wireless communication.

• Imaging in security

• Gbit WLAN

## 3. MEMS technology

Micro-Electro-Mechanical Systems (MEMS) technology integrate sensors, actuators, mechanical elements, and electronics on the same silicon substrate using micro-fabrication technology. MEMS modules replace connectorized devices, actuators, sensors, and antennas with micron scale similar devices that can be produced in mass production by a production process using integrated circuits and photolithography technology. MEMS devices reduce size, cost, weight, and power consumption while improving properties, production cost and yield, volume, and functionality significantly. The dimensions of MEMS modules may vary from several millimeters to around one micron. MEMS modules may vary from very simple structures to structures with moving elements. There are complex MEMS electromechanical systems with several moving elements controlled by integrated microelectronics. During the last thirty years MEMS designers, developers and researchers have produced an extremely large number of MEMS sensors for several sensing applications. For example, pressure sensing, heartbeat, temperature sensing, inertial forces, chemical species, magnetic fields, radiation detection and movement detection. Usually, these MEMS sensors have better performances exceeding those of conventional sensors and devices. The electronics components are produced using IC process. The micromechanical components are produced by using compatible “micromachining” processes. These processes, by using masks, etch away parts of the silicon wafer or add new structural layers to form the electromechanical and mechanical modules.

The real potential of MEMS may be fulfilled when these miniaturized sensors, actuators, and other components can all be merged onto a common silicon substrate along with integrated circuits, microelectronic ICs. The electronic components are fabricated using integrated circuit (IC) process sequences (such as CMOS, Bipolar, or BICMOS processes). The micromechanical components are fabricated using compatible “micromachining” processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices.

### 3.1 MEMS technology features and advantages

• Insertion loss lower than <0.1 dB

• Isolation lower than -50 dB

• High Linearity compared to conventional devices

• High Q compared to conventional devices

• Low volume and compact

• High power handling compared to conventional devices

• Low power consumption compared to conventional devices

• Low-cost and high-volume production compared to conventional devices

### 3.2 MEMS technology process

Bulk micromachiningproduces mechanical structures in the silicon substrate by using etching masks. Bulk micro-machined module is shown in Figure 8.

Surface Micromachiningproduce mechanical structures above the substrate surface by using sacrificial layer. Surface micro-machined module is presented in Figure 9. In Bulk micromachining technology silicon is machined using etching processes. Surface micromachining uses layers deposition on the substrate to produce a structural layer.

Surface micromachining process does not depend on the substrate used. It can be part of other production processes that modify the substrate. For example, fabrication of MEMS on a substrate with embedded control devices, in which MEMS process is integrated with integrated circuit technology.

This process is used to manufacture a wide spectrum of MEMS modules for several applications. Bulk micromachining is a subtractive fabrication process, that converts the substrate, into the mechanical parts of the MEMS module. MEMS modules can be designed by using electromagnetic software such as ADS, HFSS, and CST. The design outcomes layers masks, layout that are used to produce the MEMS module. MEMS production process is shown in Figure 10. In Figure 11 the block diagram of a MEMS bolometer coupled antenna array is presented. Packaging of MEMS modules may be more complicated. However, higher devices are easier to produce when compared to surface micromachining. Applications of RF MEMS technology:

• Tunable microwave MEMS passive elements such as inductors and filters

• MEMS Switching matrix with low loss

• MEMS antenna arrays coupled to bolometer for detection arrays

• MEMS 90GHz Detection Arrays

### 3.3 MEMS components

MEMS components are categorized in one of several applications. Such as:

1. MEMS The goal of MEMS sensorsis to sense changes and interact with the environments. MEMS sensors include sensors that detect change in temperature, sensors that detect chemical changes, movement sensors, optical sensors, radiation sensors and inertia sensors. MEMS sensors are useful due to their low-cost and small volume.

2. Microwave MEMSare modules used to transmit microwave signals, to switch or to filter RF signals. Microwave MEMSinclude tunable capacitors, switches, filters, antennas, and phase shifters.

3. Optical MEMSare compact modules that amplify, direct, reflect, and filter light such as optical reflectors and switches.

4. Thermal or electrostatic actuators provide power to other components or devices.

5. Biological MEMSare modules that, interact with biological tissue. These modules interact with biological cells, medical reagents, proteins, and other biological tissues. These devices may be employed for drug delivery or other medical missions.

6. Microfluidic MEMSare low-cost modules that interact with fluid environments. Modules such as pumps and valves. Devices that move, mix, and eject and are compact.

## 4. Computer aided design, CAD, commercial software

In the last decade, several electromagnetic commercial software was developed, see [16, 17, 18, 19]. The most popular software that are used in the design and development of wearable systems and antennas will be presented in this section.

### 4.1 High frequency structure simulator, HFSS, software

ANSYS HFSS RF simulation software is a full wave electromagnetic software. HFSS is used to simulate RF modules and antennas [17]. For example, printed antennas, waveguides and other transmission lines, connectors, antenna arrays, phased arrays, microwave devices, digital circuits, filters, MIC and MMIC packages and other RF devices. ANSYS HFSS is used to develop RF, high-speed RF systems, seekers, radar systems, microwave devices, RF satellites modules, internet of things (IoT) products and other high-speed microwave and digital devices. For more information see, https://www.ansys.com/products/electronics/ansys-hfss.

HFSS employs several solvers to give the RF engineer deep insight into all the 3D electromagnetic problems. Through integration with ANSYS thermal, structural and fluid dynamics tools, HFSS provides a multi-physics analysis of RF products, ensuring their thermal and structural reliability. The ANSYS HFSS simulation suite consists of a comprehensive set of solvers to address diverse electromagnetic problems. Its automatic adaptive mesh refinement lets the designer to focus on the design instead of spending time determining and creating the best mesh.

#### 4.1.1 HFSS electromagnetic solvers

ANSYS HFSS employs full wave 3D finite element method, momentum (MoM) analysis and the SBR ultra-large-scale asymptotic method of shooting and bouncing rays with advanced diffraction and creeping wave physics for enhanced accuracy (SBR+). The ANSYS HFSS software package has the following solvers to solve RF problems:

HFSS Solvers

• Solver in the frequency domain

• Solver in the time domain

• Solver using integral equations

• Solver that uses hybrid technologies

HFSS SBR+

• Solver that uses physical optics

• Solver that uses shooting and bouncing Ray

• Solver that uses physical theory of diffraction

• Solver that uses Creeping Wave

• Solver that uses uniform theory of diffraction

Each HFSS may solve a specific module, environment, RF devices or application.

HFSS RF Solver Features

• Communication system link budget calculations

• Wireless propagation solver

• Microwave and antennas solver

• Automated diagnostics simulation

• Microwave component libraries

• Multi-fidelity RF models

• Coupling models and analysis

Types of Circuit Simulation

• Linear circuit analysis

• DC circuit analysis and simulation

• Transient circuit analysis and simulation

• RF system multitone harmonic balance analysis

ADSis an electronic design automation software system. It offers complete design integration to designers of products such as cellular and portable phones, pagers, wireless networks, and radar and satellite communications systems [16].

ADS support communication system and RF design engineers to develop all types of RF designs, from RF and microwave modules and printed antennas to integrated MMICs for communication, medical, IOT and aerospace defense applications.

With a complete set of simulation technologies ranging from frequency and time domain circuit simulation to electromagnetic field simulation. ADS let designers fully characterize and optimize designs. Such as Harmonic Balance, Circuit Envelope, Transient Convolution, Ptolemy, X-parameter, Momentum, and 3D EM simulators (including both FEM and FDTD solvers).

ADS Simulation and Design Major Features

• Development and design of communication and RF systems

• Analysis results presentation, S parameters data and plots

• S-parameters simulation, DC, and small signal AC simulation

• Simulation of RF devices, modules, and systems

• Yield statistical simulation including components tolerances simulation to get accurate design

• Optimization of component parameters to get accurate design and high yield

• Development and design of several types of filters

• Development and design of passive devices, S-parameters simulation

• Developer of customized design guides

• ADS software libraries such as microwave component and systems, passive and active components

• Design and development of MIC and MMIC modules

• Design tools- Schematic graphical friendly user interface. Circuit schematic entry and simulation setup.

• Computation results presentation– Display graphically and tables of analysis results.

Simulators

• Frequency-domain linear RF modules simulator.

• Optimization simulation, Yield simulation, Yield Optimization, experiments design, and Presentation of Statistical yield histograms.

• Electromagnetic Momentum Simulator- Electromagnetic Momentum, EM, Simulator is a frequency domain simulation CAD tool. EM combines layout editing tools with electromagnetic simulation and S-parameters simulation to get accurate RF design. EM analysis suite includes schematic tools, simulation results presentation, EM simulator, and multilayer layout editor.

• Microwave and Communication System Simulation– Modular analysis of microwave and communication systems. Analysis of each unit and component in the system.

• Models of Passive Components- Models for capacitors, inductors, transformers, couplers, conductors, vias, and crystals.

• Models for Multilayer Design- Coupled lines models for multilayer modules such as MIC PCB, MMIC modules, and devices packaging.

• Models for Active Microwave Devices– Amplifiers, modulators and demodulators, mixers, and switches.

• Design Guide for Passive Devices- Simulation and optimization of microstrip circuits such as couplers, branch-line couples, dividers, coupled line filters, microstrip matching circuits and lumped-element circuits.

• Passive Filters Simulator- Simulation and optimization of passive filters.

#### 4.2.1 FEM simulator

The FEM simulator has afull-wave three dimensions electromagnetic simulation capabilities, based on the Finite Element Method (FEM). The RF-Pro User Interface (UI), that comes with this FEM element, makes setting up RF circuit co-simulation in Advanced Design System (ADS) fast with no errors for the design of multi-technology RF modules that integrate RFIC, MMIC, package and PCB. It also automates the extraction of nets and components for EM simulation without modifying the layout. The FEM simulator enable to simulate 3D structures such as connectors, wire-bonds and packaging with circuit and system components. It is important especially for RF module designs where 3D interconnects and packaging must be simulated along with the circuit. For more details see in, https://www.keysight.com/en/pc-1297113/advanced-design-system-ads?nid=-34346.0&cc=IL&lc=eng.

The frequency domain simulation can be used in the Electromagnetic Professional (EM-Pro) software, in the 3D EM platform and in ADS.

### 4.3 CST software

CST is a 3Delectromagnetic simulationsoftware for developing, designing, analyzing, and optimizing RF components and systems [18]. Information about CST is presented in, https://www.3ds.com/products-services/simulia/products/cst-studio-suite/.

CST Electromagnetic field solvers gives engineers the flexibility to RF systems that consists of many components and modules. CST SIMULA software allows electromagnetic simulation to accompany the design process from the earliest design stages to the final development milestone. CST EM analysis include design of couplers, dividers, antennas, filters, MEMS, electromagnetic compatibility simulation (EMC/EMI), simulation near human body, and thermal effects in transmitters. SAM a System Assembly and Modeling tool provides simple environment simulation software RF systems. The SAM suite may be employed for simulating, analyzing, and optimizing RF devices that consists of several components. The simulation products are physical quantities such as voltages, currents, fields, and S-parameters. SAM helps designers to compare the results of different solvers within one analysis project and perform post-processing simulation. For example, using the results of electromagnetic simulation to analyze thermal effects, then structural thermal effects, and other EM simulation to analyze detuning. This analysis process helps to reduce the calculation effort required to analyze a complex device accurately. The CST software is a 3D modeling schematic layout tool, with electromagnetic solvers and post-processing simulations.

CST Solvers

• Transient solver

• TLM solver

• Frequency domain solver

• Eigenmode solver

• Resonant solver

• Integral Equation Solver

• Asymptotic Solver

CST Products

• CST EM analysis is used to design several RF devices and systems. Such as couplers, dividers, antennas, filters, MEMS, electromagnetic compatibility simulation (EMC/EMI), simulation near human body, SAR problems, and thermal effects in transmitters.

• CST Simulation products include static, stationary, high and low frequency analysis of RF systems, and components with movement of charged particles.

• CST software is used to analyze multilayer structures, transmission lines, EMC design, small antennas, antenna arrays, packaging, LTCC devices, inductors, capacitors, waveguide devices, actuators, plasma sources, optical devices, sensors, recording units, and electromagnetic brakes.

### 4.4 Microwave office, AWR

Microwave Office design suite provides a flexible RF/microwave design tool [19].

Built on AWR high-frequency design platform with its open design environment and advanced unified data model. AWR operates with Visual System Simulator, VSS, system design, AXIEM and Analyst EM simulation software. The NI AWR Design suite provide a complete microwave devices solver, system solver, and EM simulation.

Microwave Office AXIEMelectromagnetic (EM) software is an EM analysis.

The AXIEM product was developed specifically for three-dimensional (3D) planar applications such as RF PCBs and modules, LTCC, MMIC, and RFIC designs.

The APLAC simulator offers multi-level analyses which includes:

• DC operation point

• Linear frequency domain

• Time domain

• Harmonic balance

• Phase noise

• Linear/non-linear noise including AC noise contributors, temperature

• Yield predictions and optimization

AWR provide accurate simulation tool and offers RF devices analysis and optimization. AWR provides a linear and nonlinear time and frequency domain simulation needed to characterize and optimize RF modules. AWR major features are listed below.

• Microwave and Communication System Simulation– Modular analysis of microwave and communication systems. Analysis of each unit and component in the system.

• Models of Passive Components- Models for capacitors, inductors, transformers, couplers, conductors, and SMT components.

• Models for Multilayer Design- Multilayer modules such as MIC PCB, MMIC modules, and devices packaging.

• Active Microwave Devices Simulation– Linear and nonlinear simulation, Amplifiers, modulators and demodulators, mixers, and switches.

• Passive DevicesSimulation - Simulation and optimization of microstrip circuits such as couplers, branch-line couples, dividers, coupled line filters, microstrip matching circuits and lumped-element circuits.

• Passive Filters Simulator- Simulation and optimization of passive filters.

AWR Capabilities– The AWR user interface provides project management and design tools for RF devices. The designers can build a device layout model from the software component library. The library supports tuning and optimization simulation.

• Computation results presentation– Display graphically and tables of analysis results.

Simulation APLAC– This robust harmonic-balance (HB) simulator provides linear and nonlinear circuit analysis with powerful multi-rate HB, transient-assisted HB, and time variant (circuit envelope) analysis, supporting large-scale and highly nonlinear RF/microwave circuits.

Planar EM– AXIEM provides accurate characterization, simulation, optimization of passive devices, planar transmission lines, printed antennas, and printed arrays.

3D EM– 3D finite element solver provides fast and accurate electromagnetic analysis of multilayer elements such as vias and bonds. The high frequency full wave analysis helps in developing RF modules from the beginning of the design up to the final electromagnetic verification.

AWR for MMIC Modules Design

• Linear and nonlinear MMIC Modules design with frequency-domain and time-domain simulation.

• MMIC module layout and production files and masks, GDSII export.

• MMIC module electromagnetic simulation and optimization from layout or schematic using commercial electromagnetic solvers.

• MMIC module design and layout rule check versus schematic.

## 5. Ultra-wideband compact integrated modules

UWB integrated modules of 18 to 40GHz Direction Finding system are shown in Figures 12 and 13. A photo of a compact UWB frontend is shown in Figure 12. The frontend module consists of a limiter and a wideband 18 to 40GHz LNA. The low noise amplifier LMA406 is A Filtronic MMIC LNA. The LNA gain is around 11 ± 1 dB with 4 ± 0.5 dB noise figure and 13 ± 1 dBm saturated output power. The LNA dimensions are 1.45 × 1.1 × 0.1 mm. A wide band PHEMT MMIC SPDT is used, AMMC-2008. The SPDT losses are lower than 2 dB. The isolation between the SPDT input port to the output ports is lower than -25 dB. The SPDT dimensions are 1 × 0.7 × 0.1 mm. The frontend electrical characteristics was evaluated by using ADS software.

Figure 13 presents a photo of the compact Switched Filter Bank SFB unit. The SFB Module consists of three side coupled microstrip filters. Each filter consists of nine sections. The filters are printed on a 5mil alumina substrate. A one to two dB attenuators connect the filters input and output ports to wide band MMIC switches. The attenuators are used to adjust each channel losses to the average required level. The module losses are adjusted to be higher in the low frequencies and lower in the high frequencies. AWR and ADS software were used to optimize the filter dimensions and structure. The SFB losses at high frequencies are around 9 dB and at the low frequencies the losses are around 10.5 dB.

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Albert Sabban (July 28th 2021). Introductory Chapter: Ultra-Wideband Technologies, Innovations in Ultra-Wideband Technologies, Albert Sabban, IntechOpen, DOI: 10.5772/intechopen.97675. Available from:

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