High Return Loss Research Articles

Design and analysis of a modified rectangular-shaped lowpass filter based on LC equivalent circuit

In this paper, a new compact microstrip lowpass filter (LPF) with a sharp roll off and wide stopband is presented. The structure is composed of a defected rectangular-shaped resonator and a rectangular shape resonator as a suppressing cell. All resonators and their additional components are analyzed based on their LC equivalent circuits, and the role of each section and its equivalent circuit are described. The LPF with 3 dB cutoff frequency at 1.44 GHz has advantages such as low insertion loss and high return loss. Based on the measurement results, the proposed LPF has a sharp transition band that is 0.22 GHz from −3 to −20 dB. On the other hand, the measured value of the group delay in the whole passband is only 47 ns, which is one of the essential advantages of this filter. The designed LPF has been simulated, fabricated and, measured. There is a proper agreement between simulation and measured results.

Influence of α- and β-W phases on performance of SMR devices

Solidly mounted resonators (SMRs) rely on high-quality Bragg reflectors, for which tungsten has been used as the high acoustic impedance layer. It is unclear about the effects of tungsten phases on the acoustic performance of SMRs. In this study, high-quality flat layers of different phase structures of W (α-W and β-W) are obtained by changing the post-growth annealing temperature and magnetron sputtering parameters. Our results show that the α-W has higher Young's modulus and acoustic impedance (205 GPa and 63 kg/m2s) than β-W (170 GPa and 57 kg/m2s). These small differences result in amplified difference in acoustic performance of Bragg reflectors using tungsten (W) as their high-impedance layer. Our tests show that the SMR of α-W Bragg reflector has a higher return loss (18.4 dB) at around 2.75 GHz and higher quality factor (687) than that of β-W Bragg reflector (9.2 dB and 228, respectively).

A very compact microstrip diplexer fabrication with superior performance for broadband wireless applications

AbstractThis study presents a planar dual‐channel bandpass microstrip diplexer based on a novel structure. It has the very compact size of 0.0081 λ g2 (95.7 mm2) fabricated on 0.787 mm dielectric substrate height. Due to the use of close microstrip sections, several coupling capacitors are created. These capacitors can increase the degree of freedom for controlling the diplexer performance while it is optimized easily. Accordingly, the designed diplexer has a high performance in terms of wide fractional bandwidths, attenuated harmonics, flat channels, high return losses and low insertion losses. The wide fractional bandwidths (FBWs%) of 34.3% at the first channel and 38.6% at the second channel make the proposed diplexer appropriate for the broadband applications. The resonance frequencies are located at f1 = 1.6 GHz for the L‐band and f2 = 3 GHz for WiMAX applications. The maximum harmonic level is less than −20 dB for the frequencies up to 6.5 GHz (4f1). The maximum group delays are <1.26 ns at the first passband and 0.56 ns at the second passband. The proposed diplexer is fabricated and measured for verification. The comparison shows that both measured and simulated results are in a reasonable agreement.

A Compact Dual-Mode Bandpass Filter with High Out-of-Band Suppression Using a Stub-Loaded Resonator Based on the GaAs IPD Process

In this letter, a compact dual-mode bandpass filter (BPF) with an ultra-wide stopband that employs two folded open-loop resonators (FOLRs) and stub-loaded resonators (SLRs) is proposed. The dual-mode resonators are optimized by loading two SLRs onto the folded open-loop resonators, and this process is analyzed using the dual-mode theory. To miniaturize the device size and increase chip performance, the proposed BPF is fabricated by a III–V compound semiconductor-fabrication process using a high-performance GaAs substrate based on the integration passivation device (IPD) fabrication process. A compact dual-mode BPF with low insertion loss and high return loss is designed and fabricated. Two extra transmission zeros (TZs) located in the high-frequency range increase the wide stopband, and the two TZs near the passband result in a higher selectivity. A resonant frequency centered at 7.45 GHz with an insertion loss of −1.21 dB and a measured return loss of higher than −23.53 dB and 3 dB fractional bandwidths of 5.8% are achieved. The stopband can be suppressed up to 20 GHz owing to the two tunable TZs resulting in higher selectivity and wideband rejection. The size of the filter was drastically optimized using a simplified architecture of two FOLRs and SLRs.

STRUCTURAL AND ELECTRICAL PERFORMANCE OF MoO3/Li/MoO3 FILMS DESIGNED AS MICROWAVE RESONATORS

In this work, the effect of the insertion of lithium slabs of thicknesses of 50 nm between stacked layers of MoO3 is considered. Stacked layers of MoO3 comprising lithium slabs are prepared by the thermal evaporation technique onto Au substrates under vacuum pressure of 10-5 mbar. The effects of Li slabs are explored by the X-ray diffraction, scanning electron microscopy, current-voltage characteristics and impedance spectroscopy techniques in the frequency domain of 0.01-1.80 GHz. While the presence of Li slabs did not alter the amorphous nature of structure, it forced the growth of rod-like grains of diameters of 100-160 nm and lengths of 1.5 𝜇𝑚. Electrically, the presence of Li in the samples enhanced the rectifying properties of the devices and force reverse to forward current ratios larger than 60 times. Li slabs also controlled the negative capacitance effect and resonance –antiresonance regions in the Au/MoO3/MoO3/C stacked layers. While the Au/MoO3/MoO3/C devices displayed high conductance and low impedance values in the studied frequency domain, the Au/MoO3/Li/MOO3/C devices exhibited low conductance and high impedance mode in the frequency domain of 0.01-0.59 GHz. It is also found that the presence of Li slabs improved the performance of the devices through driving it to exhibit lower reflection coefficient and high return loss values near 0.80 GHz. The features of the devices nominate them for use as RF-Microwave traps or resonators.

A multiband antenna for biomedical telemetry and treatments

This paper presents the design of a tri-band adhesive antenna for biomedical telemetry. Since human body is lossy in nature, the signal transmitted from an implantable medical device is usually very weak. The adhesive antenna acts like a repeater which increases the strength of the signal. This allows the signal to be sent effectively to the base station. The antenna is designed to resonate at 375 MHz, 2.525 GHz and 5.625 GHz. The measurement results show that the antenna has 10 dB impedance bandwidths of 400 MHz (175 – 575 MHz), 950 MHz (2.125 – 3.075 GHz) and 1.5 GHz (5.125 – 6.625 GHz) to cover the MICS, ISM and IEEE 802.11 WLAN bands, respectively. The proposed antenna is printed on a flexible Rogers RT/duroid 5880 epoxy substrate with a volume of 70 mm × 80 mm × 1 mm. The simulated and measured performance of the antenna confirms its omnidirectional radiation patterns and dual-band operation with high return losses.

A High-Isolation Eight-Way Power Combiner

A high-isolation eight-way power combiner is proposed in this article that is constructed by cascading three stages of power combiners in series. Its high isolation and low return loss are realized by means of lumped isolators, an isolated side network, and a resistive septum. The eight-way power combiner is basically a 17-port mode network, consisting of eight input ports, eight matching ports, and one output port. The mode network matrix cascade computation clearly reveals the working mechanism. Based on the designed 17-port network, an eight-way power combiner is realized with eight matching ports connected to loads. The measurements agree well with the simulations. From 7.8 to 10.2 GHz, the return loss at the input ports is greater than 19 dB, the return loss at the output port is greater than 18 dB, the isolation is at least 19 dB, and the insertion loss is less than 0.4 dB. The proposed eight-way power combiner has the merits of high isolation, low return loss, low insertion loss, high power capacity, and ease of integration, with great potential for integration into high-power amplifiers.

Design and Fabrication of a Planar Inverted-F Antenna (PIFA) for LEO Satellite Application

The paper is mainly emphasizes on the microstrip patch antenna design for satellite applications. The specific objective of this study is to solve the research problem on finding the simple and compact design for small satellite application in real world. A new design of a Planar Inverted-F Antenna (PIFA) with the two height of 12mm and 10mm are proposed for low Earth orbit (LEO) applications in S band. The antenna is a single form antenna with the coaxial probe fed is used. CST Microwave Studio student version was used for the simulation of the antenna and matching design parameters. The antennas are obtained an efficient high return loss -18.426dB and -18.169dB at S11, the return loss bandwidth of 471MHz and 466MHz. The radiation pattern results are analyzed beam width angle 85.1° and 95.1°. Moreover, the peak directivity gain results 4.7dBi and 4.79dBi, the absolute E-filed radiation effect are also presented. The actual measurement results for S11 parameter of return loss -13.54dB and -14.2dB, return loss bandwidth of 510MHz and 425MHz are also fabricated with the comparison of simulation and fabrication process of PIFA antenna characteristics. The measurement of the return loss (S11) and return loss bandwidth were almost identical with the simulation.

Design and Simulation of Slot Dimensions in Aperture Coupled Hemispherical Dielectric Resonator Antenna

Aperture coupled novel shaped Hemispherical Dielectric Resonator Antenna (HDRA ) and the various dimensions of slots are designed and analyzed by hfss software. The dielectric constant of dielectric hemisphere is € =9.8 and the substrate of dielectric constant is 2.96. aperture coupled novel shaped Hemispherical Dielectric Resonator Antenna (HDRA ) parameters are presented in this paper.. The effects of changing the slot length , slot width and position of slot on the antenna parameters and are presented in this paper, which are used for directive gain applications. As the change of slot dimension , it is observed that at the resonant frequency, it gives high gain and high negative return loss

A Compact $Q$ -Band Rectangular Waveguide Thermal Isolator

We present a new waveguide thermal isolator, based on a simple gap in a standard rectangular waveguide, developed for the $Q$ -band cryogenic receiver of the Sardinia Radio Telescope. The proposed component is very compact and consists of a single module, including both the horizontal and vertical polarization channels and the noise injection channel. The electromagnetic and thermal characteristics of this isolator have been fully investigated. High return loss and low insertion loss are obtained solely by a proper selection of the waveguide wall thickness, thus resulting in a very simple design, easily scalable in the whole microwave range. High robustness to misalignment and excellent thermal performance are achieved. A prototype of the proposed isolator has been manufactured and tested at room temperature, showing a very good agreement with predicted performance.

High-Performance Ultra-Compact Dual-Band Bandpass Filter for Global System for Mobile Communication-850/Global System for Mobile Communication-1900 Applications

This work presents a novel microstrip dual-band bandpass filter (BPF) using meandros spirals and patch cells, which is proposed for the first time by this work. It occupies a very compact size of 0.0017 λg2. The proposed filter is designed to operate at Fo1=0.85 GHz and Fo2=1.85 GHz for GSM-850/GSM-1900 applications. In addition to the small size, it has several advantages in terms of wide fractional bandwidths (FBW), low insertion losses and high return losses at both channels. The simulated insertion losses at the lower and upper passbands are 0.05 dB and 0.1 dB, respectively. Another advantage of the proposed BPF of this work is the attenuated harmonics, where it is able to suppress 1st, 2nd, 3rd and 4th harmonics (4.11 Fo1) with -20 dB maximum harmonic level.

A novel compact CPW tunable stop band filter using a new Z-DGS-resonator for microwave applications

The paper presents a novel very compact CPW bandstop filter. The designed structure consists of one unit of new Z-DGS resonator, placed on top layer of ground plane between the input and output this structure, which is excited by 50 ohm coplanar line. The designed filter can be used in X-Band applications as the band stop can be shifted to any other desired frequency by tuning the length of the Z-DGS. The proposed filter topology has as benefits good performances in terms of wide stop-band rejection, low insertion loss, high return loss, simple design and more small size (17.908 × 10 mm2) compared to other previous works those reported in literature. The stop-band width is from 3.96GHz to 6.21GHz, exhibits a 22,25 dB rejection bandwidth of 45% with high selectivity characteristic at the center frequency of 5.05 GHz.

Optimized planar terahertz Yagi-Uda antenna using hybrid GSA-PSO optimization algorithm

In this paper, a planar Yagi-Uda antenna design for Terahertz applications is presented and optimized. The lengths of Yagi-Uda antenna elements beside the spaces between directors’ elements are optimized seeking for obtaining high gain and minimum return loss simultaneously at 300 GHz. Thus, the directivity enhancement enables to overcome the high atmospheric attenuation influence that faces the high frequency range and limit its communication capabilities, and the return loss minimization enables to minimize the return loss to improve the impedance matching besides, reducing the mismatching losses. The Gravitational Search Optimization Algorithm with Particle Swarm Optimization algorithm (GSA-PSO) as a hybrid technique is applied on the antenna elements using an offline link between MATLAB program and Ansoft HFSS simulation program. To show the convergence capability of the GSA-PSO, the results are compared with those obtained by other algorithms such as gradient local algorithm and genetic global algorithm (GA). The optimized antenna showed high gain of 15.84 dB with a return loss of -45.27 dB compared to 15.4 dB and -15.6 dB for the conventional counterpart design, and with gain of 15.8 dB, and return loss of -21 dB for the genetic algorithm, and finally with 15.75 dB, and -28 dB for the gradient algorithm. Furthermore, the GSA-PSO algorithm improves the search capability by 30%, compared with the GA algorithm.

A Research on Microstrip Ultrawide Band Filters using Defected Ground Structure Techniques

In this paper, microstrip ultra-wideband (UWB) filters using various defected ground structures are studied. Miniature microstrip filters employed in transceiver of modern wireless communication systems play vital role in controlling and regulating frequency response. DGS techniques are etched in ground plane to design compact microstrip based low pass, high pass, bandpass and band reject filters used in modern wireless systems. Various modified and hybrid defected ground structure techniques are employed to achieve high return loss, low insertion loss, ultra compactness, good selectivity and linearity in filters. Study reveals that the proper selection and incorporation of DGS techniques while designing microstrip ultra wideband filter optimizes the various vital parameters which enhances its performance and practicability for various modern wireless communication applications.

Superior impedance matching of THz antennas with high temperature superconducting Josephson junctions

A bow-tie antenna with a step-edge Josephson junction as the detection element, located at the center of the antenna, was investigated. The performance of these detection systems is highly sensitive to impedance mismatch between the antenna and the Josephson junction. Impedance matching optimization was performed using advance microwave simulations. Based on simulations results a bow-tie antenna system was implemented and analyzed. Following our experimental results, in the presence of a 200 GHz RF signal, and further simulations, we developed an improved structure where the junction is placed between the ends of two matching strips rather than in center of the antenna. This configuration was analyzed for two antenna structures: bow-tie and planar wire dipole. We found that the dimensions of the matching strips affect both detection magnitude and frequency of return loss dip, and that reflection is extremely sensitive to the junction length. The reflectivity obtained for an antenna without a matching unit was around −14 dB while for an antenna with a matching unit return loss up to −35 dB was derived. Simulation results also showed a high directivity of the antenna, with high radiation gain and low return loss. By varying antenna and junction dimensions, we derived an optimal design in the range of 200–280 GHz.

A 53–67 GHz Low-Noise Mixer-First Receiver Front-End in 65-nm CMOS

In this paper, we present a mixer-first receiver front-end suitable for millimeter wave (mm-wave) applications. The proposed architecture includes a modified single-balanced mixer core with an on-chip balun in order to provide a differential output from an injected single-ended local oscillator signal. The mm-wave active balun incorporates a cascode cross-coupled structure to achieve a high voltage gain with low amplitude and phase imbalance. The inter-stage inductors are utilized to increase the mixer conversion gain (CG). Moreover, by manipulating the transistor body effect in the transconductance stage, the CG and noise figure of the mixer are further improved. The mixer also achieves a high input return loss which makes it suitable for the mixer-first receivers. As a proof-of-concept, a 53–67 GHz mixer with a center intermediate-frequency of 20 GHz is designed and implemented in a 65-nm CMOS process. The mixer achieves a measured peak conversion gain of 12.1 dB and a 1-dB compression point of −5 dBm. Furthermore, the fabricated mixer achieves a minimum double-sideband (DSB) noise figure of 6.5 dB over its bandwidth. The whole chip consumes 11.5 mW from a 1-V supply and excluding the pads occupies 0.27 mm2 of silicon area.

Circuit Modeling of 3-D Cells to Design Versatile Full-Metal Polarizers

An original mechanism is here proposed to achieve polarization conversion from linear to circular with the use of full-metal polarizing screens. Such screens are self-supported and conceived from the periodic arrangement of 3-D unit cells. They are built from sections of rectangular waveguides operating below the cutoff frequency and loaded with slotted discontinuities. The polarizer operates in transmission mode; the discontinuities are responsible for both its high return losses and the conversion of the impinging linear polarization to circular. Two types of 3-D cells are presented, and both of them are analyzed and designed through equivalent circuit models (CMs). These models have been thoroughly built in order to capture all the phenomena underlying the discontinuities’ behavior. The characterization of the first cell is fully done analytically, whereas the second cell needs reduced help from a full-wave solver. Furthermore, the CMs allow simple design guidelines to be identified for this type of polarizer. Two designs are performed operating in Ka-band, proving that an extension of the operation bandwidth (axial ratio and $S_{11}$ ) to 11% is possible by employing the second cell.

Electromagnetic Properties and Absorption Evaluation of Processed Carbonyl Iron and MWCNT at PANI Nanocomposites in the <inline-formula> <tex-math notation="LaTeX">$X$ </tex-math> </inline-formula>-Band

Composites loaded with various carbonyl iron-based (CI) materials are fabricated and characterized with regards to their electromagnetic properties and absorption in the X-band (8–12 GHz). The combination of inclusion CI particles and multiwalled carbon nanotubes (MWCNT) is also explored. To this effect, CI micropowder has been successively processed to get the form of flaked, porous, and nanosized TiO2-coated particles, whereas MWCNT has been coated with polyaniline (PANI). The processed fillers were primarily characterized to verify their structural consistency and large variations in the microstructure. The static magnetic properties of the CI-based powders have been analyzed via the vibrating sample magnetometry. Finally, complex dielectric permittivity and magnetic permeability spectra along with the return loss (RL) maps of composites loaded with the powders under study have been extensively investigated. Among the studied samples, the multicomponent composite with core-shell-structured CI-TiO2 and MWCNT-PANI exhibits the maximum magnetic and dielectric losses, which yields high RL peaks (>20 dB) tuned within the X-band for layer thickness from 2.5 to 3.5 mm. Particularly for thickness from 2.85 to 3 mm, this quarter-wavelength absorber displays the broadband operation potential as RL values larger than 10 dB can be achieved throughout the X-band.

Circular sectoral waveguide TM01 to TE11 mode converter

AbstractA high power microwave (HPM) TM01 to TE11 mode converter using circular sectoral waveguide (CSWG) is analyzed in this article. The design is simulated and validated by the measurements. The conversion efficiency is more than 90% over the frequency range 2.97‐3.02 GHz, Along with more than 99% of the input power is radiated at 3 GHz. The proposed all metal CSWG mode converter is of low weight, linear in design and HPM sustainable, having high return loss and good conversion efficiency.

A compact lowpass filter with ultra-high figure-of-merit for integrating with Class-F/F−1 power amplifiers

This Paper presents a microstrip lowpass filter (LPF) with compact size, and ultra-wide stopband. The structure consists of a semi-circular shaped resonator (SCSR) and circular patches as the suppressing cell. The proposed LPF has a − 3 dB cutoff frequency at 1.53 GHz. It also has suitable performances such as an extended stopband width from 1.62 to 19.1 GHz (with the attenuation level of more than − 20 dB), ultra-sharp transition-band of 0.09 GHz (from − 3 to − 20 dB). Low insertion loss, high return loss and flat group delay in the region of the passband are very significant properties of this LPF. A proper agreement between the simulation and measurement results has been achieved after the fabrication and testing. Proposed LPF has an ultra-high figure-of-merit (FOM) of 126168, showing its strong efficiency. Forasmuch as harmonic control circuits (HCCs) play a key role in designing Class-F/F−1 power amplifiers (PAs); the asymmetric high performance LPFs can be used at the input and output of these PAs in the HCC section. Therefore, the proposed LPF can be suggested for this application.