Array Phase Shifters: Theory and Technology

Phase shifters are linear one- or two-port devices for adjusting the reflection or insertion carrier phase of a band-limited signal, nominally from 0 to 2 radians. A perfect phase shifter would have: no insertion loss, a voltage standing wave ratio of 1:1, arbitrarily high power handling capability, linear phase-versus-frequency response, an arbitrarily small footprint, radiation immunity, no DC power consumption, and of course be free. Remarkably, real phase shifters can approach some of these idealized attributes. New processing techniques hold promise to significantly reduce manufacturing cost (see "Trends" at the end of this chapter)

Miniaturised and reconfigurable planar filters for ultra-wideband applications

An increasing demand for electromagnetic spectrum has resulted from the emergence of feature-rich and faster throughputs wireless applications. This necessitates the developments of dynamic reconfigurable or multifunctional systems to better exploit the existing spectrum. Future wireless devices will be expected to communicate over several bands with various other devices in order to fine tune the services they provide to the user. Each band may require a separate RF transceiver and such modern wireless multi-band multi-mode communication systems call for high performance, highly integrated compact modules. Since the Federal Communications Commission (FCC) released the unlicensed frequency band 3.1-10.6 GHz for ultra-wideband (UWB) commercial communications, the development race for commercialising UWB technology has seen a dramatic increase around the world. The aim of this research is to develop reconfigurable planar microwave filters for ultrawideband applications. The project investigates some key design issues of reconfigurable filters, which are being observed constantly in the latest development and realisation of microwave filters. Both analytical and numerical methods are performed to construct a realistic and functional design. Two different types of frequency reconfigurability are investigated in this thesis: discrete (e.g. PIN diode, Optical switch) and continuous (e.g. varactor diode). Using the equivalent circuits and considering the direct coupled filter structure in most cases, several topologies with attractive features are developed for future communication systems. The proposed works may be broadly categorised into three sections as follows. The first section explores a square ring shape close loop resonator along with an opencircuited stub in the symmetry plane. To realise a reconfigurable frequency states within the same spectrum, an innovative approach is developed for this case. An optical or photoconductive switch, comprised of a silicon die activated using near infrared light is investigated as a substitute of PIN diode and performances are evaluated to compare the feasibilities. In addition, a in-band interference rejection technique via externally coupled Tshape resonator is shown. However, it is observed that both structures achieve significant size reductions by utilising the inner part of the resonators. To improve the filter selectivity, a convenient design approach generating a pair of transmission zeros between both passband edges and a single zero in the stop band for harmonic suppression is discussed in the second section. Moreover, the development of notched rejection bands are studied and several novel methods to create a single and multiple notched bands employing the square ring shape structure are proposed. On inspection, it is found that the notch structure can be implemented without deteriorating the filter performances. The discussions are supplemented with detailed design examples which are accompanied by theoretical, simulated and experimental results in order to illustrate the filter development process and showcase practical filter performance. The third section reveals a novel highly compact planar dual-mode resonator with sharp rejections characteristics for UWB applications. A bandwidth reconfiguring technique is demonstrated by splitting its even-mode resonance. Filter structure with the dual-mode resonator is shown to have a relatively wide tuning range, significantly low insertion loss and a constant selectivity along with frequency variations in comparison to similar published works. Finally, the earlier dual-mode structure are modified to realise a dual wideband behaviour. A detail analysis with comprehensive design procedures is outlined and a solution for controlling the frequency bandwidths independently according to the application interest is provided. In line with the previous section, experimental verification is presented to support and supplement the discussions

Multi-Functional Self-Oscillating Active Integrated Array Antenna for Next Generation Wireless Communications

佐賀大学博士(工学)学位論文(Thesis)doctoral thesi

A COMPREHENSIVE OVERVIEW OF RECENT DEVELOPMENTS IN RF-MEMS TECHNOLOGY-BASED HIGH-PERFORMANCE PASSIVE COMPONENTS FOR APPLICATIONS IN THE 5G AND FUTURE TELECOMMUNICATIONS SCENARIOS

The goal of this work is to provide an overview about the current development of radio-frequency microelectromechanical systems technology, with special attention towards those passive components bearing significant application potential in the currently developing 5G paradigm. Due to the required capabilities of such communication standard in terms of high data rates, extended allocated spectrum, use of massive MIMO (Multiple-Input-Multiple-Output) systems, beam steering and beam forming, the focus will be on devices like switches, phase shifters, attenuators, filters, and their packaging/integration. For each of the previous topics, several valuable contributions appeared in the last decade, underlining the improvements produced in the state of the art and the chance for RF-MEMS technology to play a prominent role in the actual implementation of the 5G infrastructure

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development

MEMS based radar sensor for automotive collision avoidance

This dissertation presents the architecture of a new MEMS based 77 GHz frequency modulated continuous wave (FMCW) automotive long range radar sensor. The design, modeling, and fabrication of a novel MEMS based TE10 mode Rotman lens. MEMS based Single-pole-triple-throw (SP3T) RF switches and an inset feed type microstrip antenna array that form the core components of the newly developed radar sensor. The novel silicon based Rotman lens exploits the principle of a TE10 mode rectangular waveguide that enabled to realize the lens in silicon using conventional microfabrication technique with a cavity depth of 50 μm and a footprint area to 27 mm x 36.2 mm for 77 GHz operation. The microfabricated Rotman lens replaces the conventional microelectronics based analog or digital beamformers as used in state-of-the-art automotive long range radars to results in a smaller form-factor superior performance less complex low cost radar sensor. The developed Rotman lens has 3 beam ports, 5 array ports, 6 dummy ports and HFSS simulation exhibits better than -2 dB insertion loss and better than -20 dB return loss between the beam ports and the array ports. A MEMS based 77 GHz SP3T cantilever type RF switch with conventional ground connecting bridges (GCB) has been designed, modelled, and fabricated to sequentially switch the FMCW signal among the beam ports of the Rotman lens. A new continuous ground (CG) SP3T switch has been designed and modeled that shows a 4 dB improvement in return loss, 0.5 dB improvement in insertion loss and an isolation improvement of 3.5 dB over the conventional GCB type switch. The fabrication of the CG type switch is in progress. Both the switches have a footprint area of 500 µm x 500 μm. An inset feed type 77 GHz microstrip antenna array has been designed, modelled, and fabricated on a Duroid 5880 substrate using a laser ablation technique. The 12 mm x 35 mm footprint area antenna array consists of 5 sub-arrays with 12 microstrip patches in each of the sub-arrays. HFSS simulation result shows a gain of 18.3 dB, efficiency of 77% and half power beam width of 9°

Compact, Wideband, Low-dispersion, Multi-bit MEMS Phase Shifters

Low-dispersion phase shifters are key components for electrically large phased-array radar and communication systems. Unlike true-time-delay phase shifters with linear dispersion, low-dispersion phase shifters can be designed by switching between right-handed (low-pass) and left-handed (high-pass) states to achieve a constant phase shift over a wide bandwidth. However, the implementation of low-dispersion phase shifters with MEMS switches has been challenging. The designs to date suffer from either high insertion loss or high dispersion. Most important, they all occupy a large area and use a large number of MEMS switches, which negatively impact the yield and reliability, especially in view of the relatively immature RF MEMS technology.This dissertation studies design, implementation, characterization and modeling of novel metamaterial-based low-dispersion multi-bit phase shifters that use single-pole-single-throw MEMS capacitive switches to switch between right-handed and left-handed states for a specified phase shift. Three-dimensional finite-element electromagnetic simulation was used to design the basic unit cells. Each phase shifter unit cell is based on a coplanar slow-wave structure with defected ground and uses two MEMS switches in series and parallel configurations. In this dissertation, for the first time, we enhanced the maximum achievable phase shift of metamaterial-based MEMS phase shifter unit cell from 45° to 180°.Thanks to our novel 180° unit cell design, for the first time, the number of required MEMS switches for multi-bit phase shifter was reduced to two times of bits count such that a 3-bit phase shifter requires only six MEMS switches. For 2-bit and 3-bit phase shifters fabricated on a 600-µm-thick sapphire substrate, a relatively flat phase shift was obtained across the band of 21.5‒24.5 GHz with a root-mean-square phase error of less than 14°. Across the same frequency band, presented 2-bit and 3-bit phase shifters have less than 2.7 dB and 3.4 dB insertion loss, respectively.Accurate modeling and electromagnetic simulations were performed to characterize the insertion loss of the presented phase shifters. The loss is mainly due to replacing gold for copper during fabrication as well as having lossy substrate. Furthermore, there is extra mismatch loss associated with the non-flat membrane as well as radiation loss. This can be further reduced by optimizing the MEMS switch and the coplanar waveguide. The present design principle appears to be sound and can lead to phase shifters with high performance, yield and reliability with low cost for electrically large phased-array antennas

Multi-Port RF MEMS Switches and Switch Matrices

Microwave and millimeter wave switch matrices are essential components in telecommunication systems. These matrices enhance satellite capacity by providing full and flexible interconnectivity between the received and transmitted signals and facilitate optimum utilization of system bandwidth. Waveguide and semiconductor technology are two prominent candidates for the realizing such types of switch matrices. Waveguide switches are dominant in high frequency applications of 100 ? 200 GHz and in high power satellite communication. However, their heavy and bulky profile reinforces the need for a replacement. In some applications, semiconductor switches are an alternative to mechanical waveguide switches and utilize PIN diodes to create the ON and OFF states. Although, these switches are small in size, they exhibit poor RF performance and low power handling. RF MEMS technology is a good candidate to replace the conventional switches and to realize an entire switch matrix. This technology has a great potential to offer superior RF performance with miniaturized dimensions. Because of the advantages of MEMS technology numerous research studies have been devoted to develop RF MEMS switches. However, they are mostly concentrated on Single-Pole Single-Throw (SPST) configurations and very limited work has been performed on MEMS multi-port switches and switch matrices. Here, this research has been dedicated on developing multi-port RF MEMS switches and amenable interconnect networks for switch matrix applications. To explore the topic, three tasks are considered: planar (2D) multi-port RF MEMS switches, 3D multi-port RF MEMS switches, and RF MEMS switch matrix integration. One key objective of this thesis is to investigate novel configurations for planar multi-port (SPNT), C-type, and R-type switches. Such switches represent the basic building blocks of switch matrices operating at microwave frequencies. An in house monolithic fabrication process dedicated to electrostatic multi-port RF MEMS switches is developed and fine tuned. The measurement results exhibit an excellent RF performance verifying the concept. Also, thermally actuated multi-port switches for satellite applications are designed and analyzed. The switch performance at room condition as well as at a very low temperature of 77K degrees (to resemble the harsh environment of satellite applications) is measured and discussed in detail. For the first time, a new category of 3D RF MEMS switches is introduced to the MEMS community. These switches are not only extremely useful for high power applications but also have a great potential for high frequencies and millimetre-waves. The concept is based on the integration of vertically actuated MEMS actuators inside 3D transmission lines such as waveguides and coaxial lines. An SPST and C-type switches based on the integration of rotary thermal and electrostatic actuators are designed and realized. The concept is verified for the frequencies up to 30GHz with measured results. A high power test analysis and measurement data indicates no major change in performance as high as 13W. The monolithic integration of the RF MEMS switch matrix involves the design and optimization of a unique interconnect network which is amenable to the MEMS fabrication process. While the switches and interconnect lines are fabricated on the front side, taking advantage of the back side patterning provides a high isolation for cross over junctions. Two different techniques are adopted to optimize the interconnect network. They are based on vertical three-via interconnects and electromagnetically coupled junctions. The data illustrates that for a return loss of less than -20dB up to 30GHz, an isolation of better than 40dB is obtained. This technique not only eliminates the need for expensive multilayer manufacturing process such as Low Temperature Co-fired Ceramics (LTCC) but also provides a unique approach to fabricate the entire switch matrix monolithically

Design, modeling and fabrication of radio-frequency microelectromechanical switches and coplanar filters

von Anatoliy Batmano