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

A Fully-Integrated Reconfigurable Dual-Band Transceiver for Short Range Wireless Communications in 180 nm CMOS

© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.A fully-integrated reconfigurable dual-band (760-960 MHz and 2.4-2.5 GHz) transceiver (TRX) for short range wireless communications is presented. The TRX consists of two individually-optimized RF front-ends for each band and one shared power-scalable analog baseband. The sub-GHz receiver has achieved the maximum 75 dBc 3rd-order harmonic rejection ratio (HRR3) by inserting a Q-enhanced notch filtering RF amplifier (RFA). In 2.4 GHz band, a single-ended-to-differential RFA with gain/phase imbalance compensation is proposed in the receiver. A ΣΔ fractional-N PLL frequency synthesizer with two switchable Class-C VCOs is employed to provide the LOs. Moreover, the integrated multi-mode PAs achieve the output P1dB (OP1dB) of 16.3 dBm and 14.1 dBm with both 25% PAE for sub-GHz and 2.4 GHz bands, respectively. A power-control loop is proposed to detect the input signal PAPR in real-time and flexibly reconfigure the PA's operation modes to enhance the back-off efficiency. With this proposed technique, the PAE of the sub-GHz PA is improved by x3.24 and x1.41 at 9 dB and 3 dB back-off powers, respectively, and the PAE of the 2.4 GHz PA is improved by x2.17 at 6 dB back-off power. The presented transceiver has achieved comparable or even better performance in terms of noise figure, HRR, OP1dB and power efficiency compared with the state-of-the-art.Peer reviewe

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

Design of millimeter-wave bandpass filters with broad bandwidth in Si-based technology

In this paper, a novel design approach is proposed for on-chip bandpass filter (BPF) design with improved passband flatness and stopband suppression. The proposed approach simply uses a combination of meander-line structures with metal-insulator-metal (MIM) capacitors. To demonstrate the insight of this approach, a simplified equivalent LC-circuit model is used for theoretical analysis. Using the analyzed results as a guideline along with a full-wave electromagnetic (EM) simulator, two BPFs are designed and implemented in a standard 0.13-μm (Bi)-CMOS technology. The measured results show that good agreements between EM simulated and measured results are achieved. For the first BPF, the return loss is better than 10 dB from 13.5 to 32 GHz, which indicates a fractional bandwidth (FBW) of more than 78%. In addition, the minimum insertion loss of 2.3 dB is achieved within the frequency range from 17 to 27 GHz and the in-band magnitude ripple is less than 0.1 dB. The chip size of this design, excluding the pads, is 0.148 mm 2 . To demonstrate a miniaturized design, a second design example is given. The return loss is better than 10 dB from 17.3 to 35.9 GHz, which indicates an FBW of more than 70%. In addition, the minimum insertion loss of 2.6 dB is achieved within the frequency range from 21.4 to 27.7 GHz and the in-band magnitude ripple is less than 0.1 dB. The chip size of the second design, excluding the pads, is only 0.066 mm 2 .Peer reviewe

Parasitic Strip Loaded Dual Band Notch Circular Monopole Antenna with Defected Ground Structure

In this article a parasitic strip loaded monopole antennas are designed to notch dual and triple bands. The designed models are constructed on one side of the substrate material and on the other end defected ground structures are implemented. The basic antenna comprises a tuning stub and a ground plane with tapered shape slot as DGS. Another model is constructed with circular monopole radiating element on front side and similar kind of ground structure used in the basic rectangular tuning stub antenna. To create notched bands with tuning stubs, two symmetrical parasitic slits are placed inside the slot of the ground plane. The basic model is of the rectangular stub notching triple band and the circular tuning stub antenna notching dual band. Dual band notched circular tuning stub antenna is prototyped on FR4 substrate and measured results from vector network analyzer are compared with simulation results of HFSS for validation

Dual Mode Suspended Substrate Stripline (SSS) Filter

Evolution of wireless communication systems towards high flexibility, low cost and high efficiency leads to tremendous activity in the area of microwave filters. In an RF front-end of a cellular radio base station, signals are being transmitted and received simultaneously. In the receive band, there are chances of intermodulation products from the power amplifier being fed to the receiver,thus the transmit filter must have a very high level of signal rejection. Furthermore, the transmit filter must also have low passband insertion loss since it impacts the power transmitted and the overall transmit system efficiency. Recently, filters with dual-mode operation were being investigated due to their ability to produce two degenerate modes using a single physical structure; therefore, the size and cost of the filter can be reduced without compromising any figure-of-merits. A dual mode suspended substrate stripline filter is presented in this thesis. These filters enable achieving low insertion loss, high Q, high selectivity and good spurious response. Initially, a dual mode ring resonator structure is investigated using suspended substrate stripline technology. This technology is used due to its advantages which are comparable to microstrip or any other planar transmission lines. The HFSS three dimensional finite element method (FEM) is used to evaluate the resonant frequency, quality factor and the first harmonics.A second order suspended substrate stripline filter was designed with capacitive coupled input and output feeding method. The input and output feed were positioned 90 degree from each other while a notch was used in this filter to couple two degenerate modes which also control the bandwidth of the filter. A high performance Generalized Chebychev filter was designed to meet the stringent electrical requirement in the RF front-end of a cellular radio base station. With this fourth order filter, four finite frequency transmission zeros were achieved due to phase cancellation between two paths which results in high selectivity filter response. Metal tuning screws were added to improve any practical imperfections. Finally an asymmetrical Generalized Chebychev filter was designed with real frequency transmission zeros positioned on one side of the passband. With this design, the aim of achieving higher selectivity filter response above the passband was demonstrated

Novel miniature microwave quasi-elliptical function bandpass filters with wideband harmonic suppression

Filters are integral components in all wireless communication systems, and their function is to permit predefined band of frequencies into the system and reject all other signals. The ever-growing demand in the use of the radio frequency (RF) spectrum for new applications has resulted in the need for high performance microwave filters with strict requirements on both inband and out-of-band characteristics. High selectivity, high rejection, low loss and extremely wide spurious-free performance are required for both transmitter and receiver channels. In addition, these devices need to be highly compact, easy to integrate within transceivers and should be amenable to low cost manufacturing. High selectivity is essential to enable the guard band between adjacent channels to be reduced thus improving the efficiency of the RF spectrum and hence increasing the capacity of the system. A low insertion-loss, high return-loss and small group-delay in the passband are necessary to minimize signal degradation. A wide stopband is necessary to suppress spurious passbands outside the filter’s bandwidth that may allow spurious emissions from modulation process (harmonic, parasitic, intermodulation and frequency conversion products) and interfere with other systems. The EMC Directive 89/336/EEC mandates that all electronic equipment must comply with the applicable EN specification for EMI. This thesis presents the research work that has resulted in the development of innovative and compact microstrip bandpass filters that fulfil the above stringent requirements for wireless communication systems. In fact, the proposed highly compact planar microstrip filters provide an alternative solution for existing and next generation of wireless communications systems. In particular, the proposed filters exhibit a low-loss and quasi-elliptic function response that is normally only possible with filter designs using waveguides and high temperature superconductors. The selectivity of the filters has been improved by inserting a pair of transmission zeros between the passband edges, and implementing notched rejection bands in the filter’s frequency response to widen its stopband performance. The filter structures have been analysed theoretically and modelled by using Keysight Technologies’ Advanced Design System (ADS™) and Momentum® software. The dissertation is essentially composed of four main sections. In the first section, several compact and quasi-elliptic function bandpass filter structures are proposed and theoretically analysed. Selectivity and stopband performance of these filters is enhanced by loading the input and output feed-lines with inductive stubs that introduce transmission zeros at specified frequencies in the filter’s frequency response. This technique is shown to provide a sharp 3-dB roll-off and steep selectivity skirt with high out-of-band rejection over a wide frequency span. In addition, the 3-dB fractional bandwidth of the filters is shown to be controllable by manipulating the filter’s geometric parameters. Traditional microwave bandpass filters are designed using quarter-wavelength distributed transmission-line resonators that are either end-coupled or side-coupled. The sharpness of the filter response is determined by the number of resonators employed which degrades the filter’s passband loss performance. This results in a filter with a significantly larger footprint which precludes miniaturization. To circumvent these drawbacks the second section describes the development of a novel and compact wideband bandpass filter with the desired characteristics. The quasi-elliptic function filter comprises open-loop resonators that are coupled to each other using a stub loaded resonator. The proposed filter is shown to achieve a wideband 3-dB fractional bandwidth of 23% with much better loss performance, sharp skirt selectivity and very wide rejection bandwidth. The third section describes the investigation of novel ultra-wideband (UWB) microstrip bandpass filter designs. Parametric study enabled the optimization of the filter’s performance which was verified through practical measurements. The proposed filters meet the stringent characteristics required by modern communications systems, i.e. the filters are highly compact and miniature even when fabricated on a low dielectric constant substrate, possess a sharp quasi-elliptic function bandpass response with low passband insertion-loss, and ultra-wide stopband performance. With the rapid development of multi-band operation in modern and next generation wireless communication systems, there is a great demand for single frequency discriminating devices that can operate over multiple frequency bands to facilitate miniaturization. These multi-band bandpass filters need to be physically small, have low insertion-loss, high return-loss, and excellent selectivity. In the fourth section two miniature microstrip dual-band and triple-band bandpass filter designs are explored. A detailed parametric study was conducted to fully understand how the geometric parameters of the filters affected their performance. The optimized filters were fabricated and measured to validate their performance

Design and Implementation of Super Wide Band Triple Band-Notched MIMO Antennas

In this article, a triple band-notched super-wideband (SWB) monopole antenna is designed and manufactured. The measured working frequency band (out of the filters working band) ranges from 2.5 to 20 GHz. A single radiating element is utilized to analyze and implement various MIMO antennas, with isolation between the antenna ports higher than 15 dB. Two parallel-fed elements SWB MIMO antenna and four parallel-fed elements SWB MIMO antennas are presented. Metallic barriers with different shapes are used to improve the isolation among ports from a low unacceptable value of 12 dB to a value higher than 20 dB within most of the working frequency band. S-parameters of the presented SWB MIMO antennas experimentally shows that antennas perform well up to 20 GHz, which is the highest frequency supported by the available Vector Network Analyzer used in the S parameters measurements. Satisfactory performance is observed up to 50 GHz by computer simulations using the CST softwar