Analysis of switching and matching stubs in reconfigurable power divider with SPDT switch function

In this paper, performance analysis of switching and matching stubs was done to a reconfigurable power divider with Single Pole Double Throw (SPDT) switch function. Two designs (Design A and Design B) with different positions of switches and matching stubs were proposed. Rogers RO4350 (er=3.48, h=0.508 mm) was used in this analysis as a substrate material with copper thickness of 0.035 mm. The performance analysis was carried out based on insertion loss, return loss and isolation parameters. The simulated results showed that Design B had a better performance than Design A and was able to work as a reconfigurable power divider with SPDT switch function

Co-design of Reconfigurable and Multifunction Passive RF/Microwave Components

In order to meet the market demands, multi-band communication systems that are able to accommodate different wireless technologies to be compatible with different wireless standards should be investigated and realized. Multifunction and multi-band RF front-end components are promising solutions for reducing the size and enhancing the performance of multi-band communication systems. This dissertation focuses on the design and implementation of different multifunction and tunable microwave components for use in multi-standard, flexible transceiver. For frequency-domain duplexing (FDD) communication systems, in which the uplink and downlink channels are carried on different RF frequencies, a diplexer is an essential component to separate the transmitting and receiving signals from the antenna. Electrically tunable diplexers simplify the architecture of reconfigurable RF-front end. Moreover, in modern communication systems, the crowding of the spectrum and the scaling of electronics can result in higher common-mode interference and even-order non-linearity issues. In this dissertation, three tunable compact SIW-based dual-mode diplexers, with various SE (single-ended) and BAL (balanced) capabilities, are introduced for the first time. The dual-mode operation results in a dependent tuning between the two ports. The presented designs are for SE-SE, SE-BAL, and BAL-BAL. However, based on the presented design concepts, any combination of the diplexer ports can be achieved in terms of supporting the balanced and single-ended system interface. The fabricated diplexers show low insertion loss, high isolation, good tuning range and high common mode rejection. Tunable bandstop filter (BSF) is one of the essential components in the design of RF front-ends that require wide-band operations. A wide-open front-end leaves the receiver vulnerable to jamming by high-power signals. As a result, this type of front-ends requires dynamic isolation of any interfering signal. Realization of such filters in a balanced configuration, as a second function, is an important step in the realization of full-balanced RF front-ends. Balanced (differential) circuits have many important advantages over unbalanced (single-ended) circuits such as immunity to system noise, reduction of transient noise generation and inherent suppression of even-order nonlinearities. All reported balanced filters are bandpass filters that target wide pass-bands and high common-mode rejection. These filters are necessary for wide-band RF front-ends but, as mentioned above, leave the system open to interferers and jammers. In this dissertation, a new differential coupling structure for evanescent-mode cavity resonators is developed, enabling the design of fully-balanced tunable BSF. The proposed filter is tunable from 1.57-3.18 GHz with 102% tuning range. In addition, over the full range, the measured 10-dB fractional bandwidth ranges from 1-2.4%, and the attenuation level is better than 47 dB. Lastly, Substrate Integrated Waveguide (SIW) evanescent-mode cavity resonators (EVA) are employed in the design of RF couplers, quadrature hybrid and rat-race couplers. These couplers are used in the design of numerous RF front-end components such as power amplifiers, balanced mixers, and antenna array feeding networks. Utilizing such resonators (EVA) in the design allows the couplers to have wide spurious-free range, low power consumption, high power handling capability and both tunability and filtering capabilities. The proposed quadrature hybrid coupler can be tuned starting from 1.32–2.22 GHz with a measured insertion loss range from 1.29 to 0.7 dB. The measured reflection and isolation are better than 12 dB and 17 dB, respectively. Moreover, the coupler has a measured spurious free range of 5.1–3fo (lowest–highest frequency). Regarding rat-race coupler, two designs are introduced. The first design is based on a full-mode cavity while the second one is more compact and based on a half-mode cavity. Both designs show more than 70% tuning range, and the isolation is better than 30 dB

A Horst-type Power Divider with Wide Frequency Tuning Range Using Varactors

OAPA This paper presents a novel power divider with a wide frequency tuning range. In our previous work, a pair of capacitors were connected in parallel with the front transmission lines of a Trantanella-type power divider introducing an additional reflection minimum together with the original reflection zero to broaden the bandwidth. In this design, the latter transmission lines are removed. The added capacitors generate a reflection minimum which can be easily controlled by varactors. Thus, the frequency band of the power divider can be flexibly tuned by altering the varactors. Design parameters are carefully chosen to eliminate the effect of the original reflection zero. By doing so, the power divider will have a tunable centre frequency instead of a tunable bandwidth. Theoretical formulas for the characteristic impedances and electrical lengths of the transmission lines of the power divider are derived and analyzed. A power divider has been designed and fabricated to demonstrate the validity of the proposed design. The measured results indicate that the power divider can achieve a frequency tuning range of 0.9-4.2 GHz (fH/fL= 4.67:1), with in-band input and output return losses both better than 22 dB, and an insertion loss of 3.2-4 dB. The measured in-band isolation is better than 15 dB. The power divider has a simple layout and a compact size of 0.2 Ωg ෗ 0.16 Ωg which demonstrates the excellent potential of the proposed power divider for modern communication systems

A Recent Approach towards Fluidic Microstrip Devices and Gas Sensors: A Review

This paper aims to review some of the available tunable devices with emphasis on the techniques employed, fabrications, merits, and demerits of each technique. In the era of fluidic microstrip communication devices, versatility and stability have become key features of microfluidic devices. These fluidic devices allow advanced fabrication techniques such as 3D printing, spraying, or injecting the conductive fluid on the flexible/rigid substrate. Fluidic techniques are used either in the form of loading components, switching, or as the radiating/conducting path of a microwave component such as liquid metals. The major benefits and drawbacks of each technology are also emphasized. In this review, there is a brief discussion of the most widely used microfluidic materials, their novel fabrication/patterning methods

Miniaturised bandpass filters for wireless communications

The wireless industry has seen exceptional development over the past few decades due to years of sustained military and commercial enterprise. While the electromagnetic spectrum is becoming increasingly congested, there is a growing tendency to strive for higher bandwidths, faster throughputs, greater versatility, compatibility and interoperability in current and emerging wireless technologies. Consequently, an increasingly stringent specification is imposed upon the frequency utilization of wireless devices. New challenges are constantly being discovered in the development and realization of RF and microwave filters, which have not only sustained but fuelled microwave filter research over the many years. These developments have encouraged new solutions and techniques for the realization of compact, low loss, highly selective RF and microwave bandpass filters. The theme of this dissertation is the realization of planar compact performance microwave and RF bandpass filters for wireless communication systems. The work may be broadly categorised into three sections as follows. The first section presents a novel compact planar dual-mode resonator with several interesting and attractive features. Generally, planar microwave dual-mode resonators are known to half the filter footprint. However, it is found that the proposed resonator is capable of achieving further size reductions. In addition the resonator inherently possesses a relatively wide stopband as the lowest spurious harmonic resonance is observed at thrice the fundamental frequency. Properties of this resonator, such as these and more are explored in depth to arrive at an accurate electrical equivalent circuit, which is used as the basis for high order filter design. The application of these resonators in the design of bandpass filters is the subject of the second section. A general filter design procedure based on the equivalent circuit is presented to assist the design of all-pole filters. Alternatively, it is shown that generalised Chebyshev filters with enhanced selectivity may be developed with cross coupled resonator topologies. 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 explores the possibility of employing these resonators in the development of frequency tunable bandpass filters. Preference is given to varactor diodes as the tuning element due to the numerous qualities of this device in contrast to other schemes. In particular, interest is paid to center frequency tuned filters with constant bandwidth. Tunable filters constructed with the dual-mode resonator are shown to have a relatively wide tuning range as well as significantly higher linearity in comparison to similar published works. In line with the previous section, experimental verification is presented to support and supplement the discussions

Ultrawideband and Multi-state Reconfigurable Antennas with Sum and Difference Radiation Patterns

Pattern diversity is a term used to describe the operation of several antenna elements working together to produce multiple different radiation patterns with the aim of improving the quality and reliability of a communications system. One useful implementation of pattern diversity considers sum and difference radiation patterns which can be exploited to extend high-gain space coverage and tackle multipath fading. The conventional forms of such pattern diversity antennas are generally working at a single or multiple narrowband frequencies and are designed for specific applications. Hence, generating sum and difference pattern diversity in wide range of frequencies requires the development of new pattern diversity antenna designs. Ultrawideband and frequency reconfigurable designs of pattern diversity antennas are desirable to help reduce the cost and increase the flexibility in applications of pattern diversity antennas. These two types of performances constitute the principal parts of this thesis. The first part of this thesis deals with the challenges of designing ultrawideband Vivaldi antennas with sum and difference radiation patterns. When two Vivaldi antennas are placed next to each other, two mutually exclusive phenomena of grating lobe generation at the highest end of frequency and mutual coupling at the lowest end of frequency will define the bandwidth. Hence, to enhance the bandwidth, the separation between the antenna elements is reduced, which delays the grating lobes generation, and the coupling at lower frequencies is mitigated by introducing an asymmetry in the design of each Vivaldi antenna element. It is shown that this method can be extended to multi-element Vivaldi antennas for higher gain. Next, the bandwidth is further enhanced by adding two vertical metal slabs between the antenna elements improving the isolation at lower frequencies. The proposed antennas use commercially available couplers as feeding networks. As a potential replacement for couplers, an out-of-phase power divider with unequal power division is also proposed. In the second part of this thesis, the pattern diversity function is combined with multistate frequency-reconfigurable filtering functions in a series of novel designs. In the first proposed design, two quasi-Yagi-Uda antennas are used for pattern diversity, while two switchable and reconfigurable bandpass-to-bandstop filters are used to excite the antenna elements. The whole system is excited by an external commercially available rat-race coupler. In a next step, this design is modified to attain wideband, tunable bandpass, and tunable bandstop operations while obviating the need for an external coupler by using three antenna elements excited by a switchable power divider. In another implementation, the filtering functions is extended to dual-band independently tunable bandpass and bandstop to excite wideband antennas. While all the former designs featured E-plane pattern diversity, in another design aiming at increasing space coverage, a switchable patch antennas with sum and difference radiation patterns in both E- and H-plane of the antenna is designed.Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 202

Analysis Of Switching And Matching Stubs In Reconfigurable Power Divider With SPDT Switch Function

In this paper, performance analysis of switching and matching stubs was done to a reconfigurable power divider with Single Pole Double Throw (SPDT) switch function. Two designs (Design A and Design B) with different positions of switches and matching stubs were proposed. Rogers RO4350 (er=3.48, h=0.508 mm) was used in this analysis as a substrate material with copper thickness of 0.035 mm. The performance analysis was carried out based on insertion loss, return loss and isolation parameters. The simulated results showed that Design B had a better performance than Design A and was able to work as a reconfigurable power divider with SPDT switch functio