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Here, a transition technique for converting signals from rectangular waveguide to coupled microstrip lines (CML) is presented, which provides a solution for differential antenna array feeding of automotive radar. The key to the proposed transition structure is to connect the coupling patches together with a short‐bridge structure, thus forming a quasi‐loop structure. Through the short bridge, the radiation efficiency of the antenna is greatly enhanced, and the mode conversion from TE10 of rectangle waveguide to differential mode of coupled microstrip line is realized effectively under the extremely compact size. Finally, the designed transition structure is manufactured and measured. The experimental results show that the back‐to‐back insertion loss is lower than 0.65 dB and the return loss is higher than 16.8 dB in the W‐band (75–110 GHz), which is the best performance and the simplest design among the relevant transition transitions reported so far. [ABSTRACT FROM AUTHOR]

Abstract Here, a transition technique for converting signals from rectangular waveguide to coupled microstrip lines (CML) is presented, which provides a solution for differential antenna array feeding of automotive radar. The key to the proposed transition structure is to connect the coupling patches together with a short‐bridge structure, thus forming a quasi‐loop structure. Through the short bridge, the radiation efficiency of the antenna is greatly enhanced, and the mode conversion from TE10 of rectangle waveguide to differential mode of coupled microstrip line is realized effectively under the extremely compact size. Finally, the designed transition structure is manufactured and measured. The experimental results show that the back‐to‐back insertion loss is lower than 0.65 dB and the return loss is higher than 16.8 dB in the W‐band (75–110 GHz), which is the best performance and the simplest design among the relevant transition transitions reported so far.

This paper introduces a streamlined design that includes a broadband directional coupler, a set of three-port union-T power dividers, and several microstrip transitions. These components leverage substrate-integrated waveguide (SIW) technology, operating across multiple frequency bands and offering equal power distribution in all output ports. The directional coupler, dividers, and transitions underwent a comprehensive design, simulation, and optimization process using CST Microwave Studio. A crucial aspect of the SIW design was the meticulous consideration of transitions necessary to achieve optimal matching between the SIW devices and the connected structure (such as microstrip or SMA connectors). This approach ensured a consistent focus on seamless integration. For validation purposes, the devices were manufactured physically using the RF-5880 substrate, which works with frequencies up to 40 GHz. The experimental results were then compared with simulations conducted in CST Microwave Studio, validating the prototypes. The findings confirmed that the design performs as intended, exhibiting expected behavior and showcasing a notable agreement between the simulation and experimental results. Furthermore, the designs were treated as standard rectangular waveguides, functioning within microwave and millimeter wave frequencies ranging from 8 to 40 GHz. The paper not only outlines these designs but also proposes practical dimensions for SIW technology, offering a tangible guide for the realization of these devices.

Abstract In this study, we present an ultra‐wideband full‐duplex system constituted of a wideband 4‐element Vivaldi array and wideband microstrip‐to‐slotline baluns. The proposed system is characterised by its simplicity, high directivity, and high self‐interference cancellation levels over a wide frequency bandwidth. The system is fabricated using basic printed‐circuit board (PCB) technology and can provide at least 50 dB of self‐interference cancellation over the bandwidth of operation, 4–40 GHz, with an average gain of 7.8 dBi. The system has a size of 8 cm × 8 cm × 9.4 cm and can be used as a high data rate link between two distant wireless nodes. To assess the merits of the proposed system and compare it to other published works, a new figure of merit (FoMWFD) dedicated to wide‐band full‐duplex antenna topologies is introduced in this study.

In this study, we present an ultra‐wideband full‐duplex system constituted of a wideband 4‐element Vivaldi array and wideband microstrip‐to‐slotline baluns. The proposed system is characterised by its simplicity, high directivity, and high self‐interference cancellation levels over a wide frequency bandwidth. The system is fabricated using basic printed‐circuit board (PCB) technology and can provide at least 50 dB of self‐interference cancellation over the bandwidth of operation, 4–40 GHz, with an average gain of 7.8 dBi. The system has a size of 8 cm × 8 cm × 9.4 cm and can be used as a high data rate link between two distant wireless nodes. To assess the merits of the proposed system and compare it to other published works, a new figure of merit (FoMWFD) dedicated to wide‐band full‐duplex antenna topologies is introduced in this study. [ABSTRACT FROM AUTHOR]

Two broadband designs for top‐mount vertical coaxial‐to‐microstrip transitions are proposed. Both feature eccentric structures to facilitate the electromagnetic field transformation between the two transmission lines, which would increase the 1‐dB passband of the transitions. One design is characterized by a through hole next to the strip end of the microstrip line, whereas the other has a circular slot in the ground plane and underneath the strip end. Both are created to improve the vertical connection between the strip end and the center conductor of the coaxial connector. The optimum simulation results of the presented design examples demonstrate nearly 190% and 230% increases in the 1‐dB passband, respectively, compared to the corresponding conventional design. The validity of the simulation results was confirmed experimentally. More simulations indicate that the designs can serve for microstrip lines of different physical properties, and work well for transitions to another popular transmission line, coplanar waveguide. [ABSTRACT FROM AUTHOR]

This Letter presents a non‐galvanic D‐band (110–170 GHz) interconnect realised in embedded wafer level ball grid array (eWLB) packaging technology. The interconnect consists of a patch‐radiator‐based waveguide transition implemented using one of the technology's redistribution layers. The patch radiates to a WR‐6.5 standard waveguide perpendicular to its plane. An electromagnetic band‐gap structure realised by metal patches is used to suppress undesired modes and improve the performance of the transition. The proposed solution is experimentally verified, and measurement results show that the transition exhibits an average insertion loss of 2 dB across the frequency range 122–146 GHz which, to the best of the authors' knowledge, is the lowest reported loss for a D‐band packaging solution in eWLB technology and hence addresses one of the main integration challenges facing millimetre‐wave systems. [ABSTRACT FROM AUTHOR]

A new octave bandwidth high selectivity compact microstrip diplexer working in the band from 10 to 20 GHz is presented, intended to be a part of an electro-optical interferometer covering the whole frequency band. The circuit is based on the combination of hybrid couplers and bandpass filters both on the microstrip technology. The diplexer provides two output frequency bands which cover the 10–14 GHz (relative bandwidth of 33%) and the 16–20 GHz (relative bandwidth of 22%) ranges, respectively, with a stop band in between from 14 to 16 GHz. Measured results show a insertion loss level of 3.3 dB for both output bands and high selectivity performance, exhibiting a rejection level between output bands higher than 20 dB and return loss better than 10 dB in all ports. [ABSTRACT FROM AUTHOR]

A simple but accurate transmission line model for the analysis of microstrip travelling wave antennas based on microstrip lines and right angle bends is described. Radiated far fields from the antenna are calculated using magnetic current on the antenna sidewalls and electric current on the strip surface. Local reflections from the right angle discontinuity are considered in internal field calculations. An equivalent decay constant to accommodate the radiated power from the antenna is introduced which is iteratively computed to improve impedance and radiation characteristics calculated by the model. Total power lost in the line due to this equivalent decay constant is equal to the total power radiated from the antenna. A rampart line antenna having three unit cells is fabricated in the C band and the results from the model are compared with those from full wave MoM simulations and practical measurement with good agreement. This simple yet accurate model would be valuable in computer aided design for optimal microstrip line based antennas with minimal computational resources. [ABSTRACT FROM AUTHOR]

In this article, a broadband microstrip-to-waveguide transition with antisymmetric tapered probe as well as a W-band power divider/combiner using dual proposed antisymmetric tapered probes is presented. Because of tapered microstrip shapes and metallic steps, the proposed transition is proved to be broadband, efficient, and compact. The insertion loss of the transition sample is less than 0.56 dB between 75 GHz and 100 GHz. Under the assistance of the gradually changed waveguide and dual parallel tapered probes, the operating band of the power divider/combiner has been significantly improved, which is adequate to work in the whole W-band. A back-to-back prototype of the divider/combiner is fabricated and measured. The measured insertion loss of the single divider/combiner is less than 0.29 dB between 90 GHz and 100 GHz, and agrees well with the simulations. Because the circuit size is smaller than 8.0 mm × 2.2 mm (Thanks to the excellent performance and compact size), the proposed design can find wide applications in miniaturized MCM/MMIC systems. [ABSTRACT FROM AUTHOR]

A balanced tri-band equal power divider (PD) is proposed based on a balanced stepped-impedance microstrip-slotline transition structure in this paper. Multiband differential-mode (DM) responses can be realized by embedding multiple complementary split-ring resonators (CSRRs) into the slotline resonator. It is found that a high and wideband common-mode (CM) suppression can be achieved. Moreover, the center frequencies of the DM passbands are independent from the CM ones, which significantly simplifies the design procedure. In order to validate its practicalbility, a balanced PD with three DM passbands centred at 1.57, 2.5 and 3.5 GHz is fabricated and a good agreement between the simulated and measured results is observed. To our best knowledge, a balanced tri-band PD is the first ever reported. [ABSTRACT FROM AUTHOR]

This study presents a novel technique for designing an ultra-wideband (UWB) filteringantenna with dual sharp band notches. This design is composed of a modified monopole antenna integrated with resonant structures. The monopole antenna is modified using microstrip transition between the feedline and the patch. In addition, block with a triangle-shaped slot is loaded on each side of the ordinary circular patch to produce wide bandwidth with better return loss and higher frequency skirt selectivity. The resonant structures are constructed using two double split ring resonators (DSRR) loaded above the ground plane of the antenna to produce dual band notches and filter out WiMAX (3.3-3.7GHz) and HiperLAN2 (5.4-5.7GHz) frequencies. The band notch position is controlled by varying the length of the DSRR. The reconfigurability feature is achieved by using two PIN diode switches employed in the two DSRR. The measured results show that the proposed filtering-antenna provides wide impedance bandwidth from 2.58 to 15.5GHz with controllable dual sharp band notches for WiMAX and HiperLAN, peak realized gain of 4.96 dB and omnidirectional radiation pattern. [ABSTRACT FROM AUTHOR]

This paper first presents two types of wideband microstrip-to-microstrip equal ripple vertical transitions designed with the uniform and folded slotline structures, respectively. By solving the characteristic function with differential calculation, the condition for realizing the constant equal ripple frequency response but different bandwidths (BWs) for the proposed transition is determined with resorting to the characteristic impedances of the coupled open-circuited microstrip line and slotline. Then, a vertical transition with the uniform slotline is synthetically analyzed and designed with Chebyshev polynomial function and another similar vertical transition with the same in-band ripple level but different BWs is also comparatively presented. By modifying the normalized impedances of the proposed transition to make the theoretical result close to the simulated one with the initial normalized impedances, the transformer turns ratios of the microstrip-to-slotline intersection is exactly calculated by the impedance ratios between two corresponding sets of normalized impedances. Due to the degraded high-frequency performance caused by the radiation loss of the uniform slotline, two vertical transitions with the folded slotline structure are further analyzed and the related turn ratios are extracted with the proposed approach. To verify the effectiveness on the reduction of radiation loss for the folded slotline structure, a six-pole wideband bandpass filter is presented with high-frequency performance greatly improved. In final, wideband vertical transitions with different slotline structures and a six-pole wideband bandpass filter are synthetically designed, simulated, fabricated, and measured. [ABSTRACT FROM AUTHOR]

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In this letter, a compact ultra-wideband (UWB) bandpass filter based on CPW-to-microstrip transition structure is proposed. Compared with traditional UWB BPF using hybrid structures, the proposed filter has a more sharp selectivity due to a transmission zero located at the lower edge of the passband generated by the combined effect of both CPW-MS-CPW and interdigital coupling line (ICL). Moreover, to further improve its selectivity, the CPW open stubs (CPWOS) are introduced to produce two extra transmission zeros at high frequency. The measured results show that the proposed filter has some good characteristics such as sharp roll-off, compact size (0.54λg x 0.38λg) and a very wide fractional bandwidth of 130%, which is a significant improvement to what has been reported for UWB BPF with similar structures. [ABSTRACT FROM AUTHOR]

A novel Vivaldi rectenna operated at 35 GHz with high millimeter wave to direct current (MMW-to-DC) conversion efficiency is presented and the arrays are investigated. The measured conversion efficiency is 51.6% at 35 GHz and the efficiency higher than 30% is from 33.2 GHz to 36.6 GHz when the input MMW power is 79.4 mW. The receiving Vivaldi antenna loaded with metamaterial units has a high gain of 10.4 dBi at 35 GHz. A SIW- (substrate integrated waveguide-) to-microstrip transition is designed not only to integrate the antenna with the rectifying circuit directly but also to provide the DC bypass for the rectifying circuit. When the power density is 8.7 mW/cm2, the received MMW power of the antenna is 5.6 mW, and the maximum conversion efficiency of the rectenna element is 31.5%. The output DC voltage of the element is nearly the same as that of the parallel array and is about half of the series array. The DC power obtained by the 1 × 2 rectenna arrays is about two times as much as that of the element. The conversion efficiencies of the arrays are very close to that of the element. Large scale arrays could be expended for collecting more DC power. [ABSTRACT FROM AUTHOR]

A planar wideband balun is proposed. The proposed balun consists of a novel slotline T-junction and three microstrip-slotline transitions. Similar to the principle of the E-plane waveguide T-junction, the slotline T-junction acts as a phase inverter. With the microstrip-slotline transition, the device employs microstrip as feedlines. The radiation loss of the slotline is reduced to improve the insertion loss by loading the slotline with a superstrate and adding via holes along the slotline. An experimental balun with a bandwidth of 128% from 2.2GHz to 10 GHz is designed, fabricated, and measured for validation. The measured results have reasonable agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

In this paper, a novel waveguide-to-microstrip transition is developed based on probe coupling. It is designed for millimeter wave applications. The proposed structure is simple and easy to fabricate with good performance. Simulation results show that the return loss is less than -18.9 dB in the entire D-band. [ABSTRACT FROM AUTHOR]

We present the design and characterization of planar mm-wave patch antenna arrays with waveguide-to-microstrip transition using both near- and far-field methods. The arrays were designed for metrological assessment of error sources in antenna measurement. One antenna was designed for the automotive radar frequency range at 77 GHz, while another was designed for the frequency of 94 GHz, which is used, e.g., for imaging radar applications. In addition to the antennas, a simple transition from rectangular waveguide WR-10 to planar microstrip line on Rogers 3003™ substrate has been designed based on probe coupling. For determination of the far-field radiation pattern of the antennas, we compare results from two different measurement methods to simulations. Both a far-field antenna measurement system and a planar near-field scanner with near-to-far-field transformation were used to determine the antenna diagrams. The fabricated antennas achieve a good matching and a good agreement between measured and simulated antenna diagrams. The results also show that the far-field scanner achieves more accurate measurement results with regard to simulations than the nearfield scanner. The far-field antenna scanning system is built for metrological assessment and antenna calibration. The antennas are the first which were designed to be tested with the measurement system. [ABSTRACT FROM AUTHOR]

A compact wideband planar double-sided printed quasi-Yagi antenna is presented. This paper focuses on the feasibility of substituting conventional balun for microstrip-to-slotline transition balun to achieve wider bandwidth and relatively smaller size. The proposed antenna, consisting of a feeding balun, a concave arc-shaped reflector, a modified driver with stacked structure and two directors, is designed and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed antenna can provide an impedance bandwidth of nearly 100% (2.02-6.05 GHz). Additionally, within the impedance bandwidth, the radiation pattern of the proposed antenna has front-to-back (F/B) ratios ranging from 10.1 dB to 19.1 dB, cross-polarization levels in the main radiation direction from 19.8 dB to 36.2 dB and gains from 3.4 dBi to 7.4 dBi. [ABSTRACT FROM AUTHOR]

In this study, a low-loss and compact planar power combiner for solid state power amplifiers (SSPAs) is proposed. It combines eight power amplifier modules with low insertion loss (IL) and high reliability by utilising a novel magic-Tee configuration and E-plane bend along with a suitable microstrip-to-waveguide transition. The fabricated prototype was implemented through automatic milling machines to produce three planar layers that form the final structure. This novel approach enabled precise fabrication, simple assembly of the SSPAs as well as low-cost manufacturing in comparison with existing traditional approaches. This process is suitable for SSPAs operating from 4 to 40 GHz. The combined IL of the implemented combiner network is less than 0.6 dB at Ka-band, 0.5 dB at Ku-band, and 0.4 dB at X-band while exhibiting a 10% fractional bandwidth. [ABSTRACT FROM AUTHOR]

A broadband, compact on‐chip contact pad to microstrip transition for use in silicon (Si) based technologies operating up to 330 GHz has been investigated and fabricated. The pad is designed as a short coplanar waveguide structure to concentrate the electrical field in the narrow gap between signal and ground pads, thus eliminating the need for a substrate shield while preserving low interaction with the lossy silicon substrate. The working principle is confirmed by electromagnetic field simulations using a detailed model of a high‐frequency measurement probe, which allows to investigate the field distribution with a realistic excitation source. The fabricated test structure with two transitions in a back‐to‐back configuration shows excellent broadband properties and insertion loss below 4.2 dB up to 330 GHz, making the proposed structure well suited for millimetre‐wave applications. [ABSTRACT FROM AUTHOR]

A comparative study between via-holed and via-free back-to-back GCPW-MS-GCPW (Grounded Coplanar Waveguide-Microstrip lines) transitions is reported in this paper. According to simulation results, both via-holed and via-free transitions on commercial benzocyclobutene polymer 20 µm film show a bandwidth over 57 GHz. Bandwidth of optimized via-holed transitions increases with the via-hole diameter, up to 75 GHz with 300 μm via-hole diameter. The via-hole free transition achieves experimentally an ultrabroadband from 2 GHz to 78 GHz with an insertion loss of only 0.5 dB thanks to the copper metallization thickness of 2 μm. In addition, these measurement results are in perfect agreement with the simulation results. These via-free and via-holes transitions are very useful and requested in component packaging, on-wafer measurements of microstrip based microwave integrated circuits, and also the interconnections in hybrid circuits including both microstrip and coplanar structures. [ABSTRACT FROM AUTHOR]

ABSTRACT A wideband vertical microstrip-to-micrstrip transition is presented by utilizing the composite microstrip/slotline resonators. With the coupling between two 50-Ω microstrip lines on top and bottom layers, respectively, and a uniform slotline resonator on the common ground plane, a proposed three-pole wideband filtering performance for the signal transmission through different layers can be achieved. To verify the expected results, a vertical transition prototype is simulated, fabricated and measured. Good agreement between the simulation and measurement results is gained. An operating band from 3.51 to 8.25 GHz with maximum insertion loss of 1.5 dB and group delay < 0.4 ns is achieved in measurement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2213-2216, 2015 [ABSTRACT FROM AUTHOR]

The optical illumination of a microstrip gap on a thick semiconductor substrate creates an inhomogeneous electron–hole plasma in the gap region. This allows the study of the propagation mechanism through the plasma region. This paper uses a multilayer plasma model to explain the origin of high losses in such structures. Measured results are shown up to 50 GHz and show good agreement with the simulated multilayer model. The model also allows the estimation of certain key parameters of the plasma, such as carrier density and diffusion length, which are difficult to measure by direct means. The detailed model validation performed here will enable the design of more complex microwave structures based on this architecture. While this paper focuses on monocrystalline silicon as the substrate, the model is easily adaptable to other semiconductor materials such as GaAs. [ABSTRACT FROM AUTHOR]

A compact and simple differential ultra wideband (UWB) equal power divider (PD) with one narrow notch‐band is presented. The proposed PD is based on slotline resonators and balanced stepped‐impedance microstrip‐to‐slotline transition structures. A wide differential‐mode (DM) impedance bandwidth covering from 1.8 to 11.5 GHz can be achieved. Besides, independent common‐mode (CM) responses with a larger bandwidth and higher suppression can be obtained. It is noted that the DM passbands are independent from the CM responses, which significantly simplify the design procedure. In addition, a narrow and sharp DM notched band from 5.8 to 5.9 GHz is generated by adding one pair of quarter‐wavelength short‐circuited stubs next to the microstrip line symmetrically. In order to illustrate the effectiveness of the design, a prototype is fabricated and measured. A good agreement between the simulated and measured results is observed. To the best of authors' knowledge, the proposed balanced UWB PD is the first ever reported. [ABSTRACT FROM AUTHOR]

A filtering power divider (FPD) with high selectivity is presented. Initially, by elaborately introducing two different types of microstrip‐to‐slotline transition structures and a pair of dual‐mode stub‐loaded resonators, dual‐mode bandpass response is attained in this design. Afterwards, the resistor R is utilised to achieve high in‐band isolation between two output ports of the FPD. Moreover, four transmission zeros are generated outside the passband for high selectivity performance. To validate the feasibility of the new approach, a prototype FPD operating at 3.62 GHz (f0) is designed, fabricated and measured. Both simulated and measured results are provided in good agreement indicating that the proposed FPD exhibits a better than 20 dB isolation inside the passband and extended upper stopband up to 10 GHz. [ABSTRACT FROM AUTHOR]

A novel compact ultra‐wideband (UWB) bandpass filter based on vialess vertical coplanar waveguide (CPW)/microstrip transitions is proposed, designed, fabricated and measured. The represented filter consists of two back‐to‐back hybrid microstrip/slotline transitions derived from the microstrip to CPW. Due to this coupling configuration, a smooth UWB passband response with an insertion loss <0.85 dB is achieved. Moreover, two transmission zeros at lower and upper passband edges are introduced to provide sharp selectivity. For verification, a prototype is fabricated and measured. The simulated results are in good agreement with the measured one. [ABSTRACT FROM AUTHOR]

A new wideband transition from microstrip line to substrate integrated waveguide (SIW) is introduced. Unlike most transitions that show reduced return loss over significant parts of a regular waveguide band, the presented configuration achieves return losses better than 30 dB in standard waveguide frequency bands from X to E. The new aspect of this transition is the addition of two vias to the widely used microstrip taper transition. Moreover, the influence of the substrate height is demonstrated. The results in each frequency band are compared with the data for the regular microstrip taper alone. A design formula for the placement of the vias and taper dimensions is presented and demonstrated to provide excellent results. The structures are simulated and optimized with CST Microwave Studio. Measurements performed on a Ku-band back-to-back prototype transition demonstrate a minimum return loss of 26.05 dB and maximum insertion loss of 0.821 dB over the entire Ku-band, thus validating the design approach. [ABSTRACT FROM AUTHOR]

This paper describes the design based on a Multiphysics simulation for a waveguide X-Band Fin Taper (FT) Spatial Power Combiner. The proposed device uses Fin Lines to microstrip transition (FLuS) to convert the energy from a rectangular waveguide (WG) TE10fundamental mode to a microstrip (μS) transmission line (TL) quasi-TEM (q-TEM) mode, in order to be amplified by Solid-State Power Amplifiers. An alteration of the electromagnetic behavior can be produced by the temperature increase and the geometrical displacement induced by the thermal expansion of the structure due to the power dissipation of the MMIC amplifiers. A proper multiphysics model is proposed to select materials and shapes of the probes and their support (carrier), considering the thermo-mechanical operative condition. A virtual prototyping technique is proposed: electric field andS-parameters’ computation in such critical conditions are shown. The proposed study has allowed for the proper thermo-mechanical design for such amplifiers; hence, best materials and technologies have been chosen. [ABSTRACT FROM PUBLISHER]

In this paper a useful, simplex and broadband coaxial-to-microstrip transitions using GCPW, simple pre-transition, are designed and implemented. The GCPW, pre-transition section is utilized to provide a smooth transition from coaxial to microstrip. In this transition the effects of the field and impedance matching with considering possible fabrication errors in total performance are completely analyzed. Experimental results are very close with simulation results. The results of 50 mm length of Microstrip line with back-to-back transitions show that a ultra wideband transition with return loss better than -10 dB and in the worth case, total insertion loss is less than 1 dB up to 30 GHz. These good performances and its simplicity, easy fabrication and good performances make this proposed transition very useful in many applications such as UWB short range Radars up to 30 GHz and make it a very good candidate for higher frequencies. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel design of a balanced wideband power divider (PD) with enhanced common-mode (CM) suppression is proposed. The top and bottom layers of the structure contain tapered microstrip line. Those microstrip lines are coupled via slotline in the ground plane, which is located at the middle layer. With appropriate placement of the slotline, the coupling between the slotline mode and the differential-mode (DM) signals can be maximized, while that between the slotline mode and the CM signals can be minimized. Simulated and measured results show that the proposed PD has equal power division, low insertion loss, and good return loss. In the measurement, the fractional bandwidth of the measured −10 dB (DM) return loss is about 101% (1.82-5.35 GHz), the insertion loss for the DM signals is less than 5 dB, the suppression of the CM signals is higher than 45 dB, and the DM isolation is better than 10 dB over the fractional bandwidth. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:437-442, 2014. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive design protocol for a W-band E-plane waveguide-to-microstrip transition covering all aspects, from the probe design, matching, cut-off cavity size estimations, verification analysis with different 3D EM simulators, and the entire fabrication process, with special emphasis on tolerances and yield with optimized costs. In fact, a complete study of the manufacture yield is done without the need to fabricate a large number of units of the microstrip-to-waveguide transition by taking advantage of the Monte Carlo tools embedded in 3D EM simulators. A simple equivalent circuit model of the transition is proposed and validated to be used in W-band system level simulations. These are requirements to enable massive use of W-band products (i.e., concealed weapons detection, imaging, etc.) with reasonable costs. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:77-91, 2014. [ABSTRACT FROM AUTHOR]

A novel, broadband, vialess, and vertical microstrip-to-microstrip transition is proposed in this paper. The transition consists of two open-circuited microstrip resonators and a U-shaped resonant-slot on the common ground plane. A physics-based equivalent-circuit model is developed for interpreting its working mechanism and facilitating the design process. The transition is analogous to a three-pole resonator filter. Based on the equivalent-circuit model, the coupling coefficients of the physical circuit can be calculated from the group delay information of two segregated electromagnetic models. To effectively control the couplings, a modified configuration is also proposed. A prototype transition is designed using the proposed design formulas. The fabricated circuit is measured to validate the proposed transition and the equivalent-circuit model. Good agreement is obtained between not only the measured and the simulated performance, but also the designed and the extracted-circuit model. In addition to the wide bandwidth, the features of vialess and easy fabrication make the novel transition very attractive for system-on-package applications. [ABSTRACT FROM PUBLISHER]

The design, simulation, and measurement of a complete microstrip line-fed dielectrically guided horn antenna are presented. The proposed antenna achieves similarly high gains as compared to traditional air-filled horn antennas, is simpler than a typical array design, and can easily be fabricated using typical two dimensional substrate machining processes. An H-guide, operating in the fundamental TE00 mode, slowly tapers into a “gapped” H-guide, or dielectrically guided horn, where a large air gap separates the center dielectric and metallic plates. A wideband Bézier shaped microstrip to H-guide transition feeding structure is fabricated using a low loss Rogers 5880 substrate and integrated with the proposed antenna. The fabricated prototype operates from 8 to 16 GHz with a peak gain of approximately 16 dBi. [ABSTRACT FROM PUBLISHER]

The pad pitch of modern radio frequency integrated circuits is in the order of few tens of micrometers. Connecting a large number of high-speed I/Os to the outside world with good signal fidelity at low cost is an extremely challenging task. To cope with this requirement, we need reflection-free transmission lines from an on-chip pad to on-board SMA connectors. Such a transmission line is very hard to design due to the difference in on-chip and on-board feature size and the requirement for extremely large bandwidth. In this paper, we propose the use of narrow tracks close to chip and wide tracks away from the chip. This narrow-to wide transition in width results in impedance discontinuity. A step change in substrate thickness is utilized to cancel the effect of the width discontinuity, thus achieving a reflection-free microstrip. To verify the concept, several microstrips were designed on multilayer FR4 PCB without any additional manufacturing steps. The TDR measurements reveal that the impedance variation is less than 3 Ω for a 50 Ω microstrip and S11 better than –9 dB for the frequency range 1 GHz to 6 GHz when the width changes from 165 μm to 940 μm, and substrate thickness changes from 100 μm to 500 μm. [ABSTRACT FROM AUTHOR]

A broadband printed quadrifilar helical antenna employing a novel compact feeding circuit is proposed in this paper. This antenna presents an excellent axial ratio over a wide beamwidth, with a 29% bandwidth. A specific feeding circuit based on an aperture-coupled transition and including two 90° surface mount hybrids has been designed to be integrated with the quadrifilar antenna. Over the bandwidth, the measured reflection coefficient of the antenna fed by the wideband compact circuit has been found to be equal to or lower than -12 dB and the maximum gain varies between 1.5 and 2.7 dBic from 1.18 to 1.58 GHz. The half-power beamwidth is 150°, with an axial ratio below 3 dB over this range. The compactness of the feeding circuit allows small element spacing in array arrangements. [ABSTRACT FROM AUTHOR]

A broadband out‐of‐phase power divider in a compact structure employing a microstrip technology is presented. The proposed power divider consists of a T‐junction of microstrip to slotline transition at the input ports along with a pair of tightly coupled microstrip lines at the two output ports. The main features of the proposed device are the employment of a dumbbell‐shaped slot terminated with a chip resistor under the tightly coupled lines to improve the isolation between the output ports and shunt open‐ended stubs at the output ports to improve their impedance matching. The overall size of the structure is 30 × 60 mm using the substrate Rogers RO4003C with a dielectric constant of 3.38 and thickness of 0.4 mm. The simulated and experimental results of the developed device show wide bandwidths (120% fractional bandwidth) with isolation >15 dB across the investigated band 1–4 GHz. In addition, the output ports are out‐of‐phase with <1° phase imbalance across the whole frequency band. [ABSTRACT FROM AUTHOR]

In this study, a systematic and simplified design procedure for quasi-Yagi antennas is presented. The design is based on the simple field and impedance matching among antenna components. This new antenna design is possible due to the newly developed ultra-wideband balun. Two types of wideband quasi-Yagi antennas are successfully designed and implemented in Ku- and Ka-band with frequency bandwidths of 53.2% and 29.1%, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2068–2071, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23563 [ABSTRACT FROM AUTHOR]

A millimeter-wave transition from a waveguide to two microstrip lines and the design methodology are proposed. A rectangular patch element in a short-terminated waveguide is analyzed by the cavity model of a patch antenna and the dyadic Green's function of the waveguide. The analysis points out that the rectangular patch element has an optimum width for wideband, which only has the function of the broad wall width of the waveguide. The transition also works as a divider. A numerical investigation of a transition having two microstrip lines validates the analytical model in terms of wideband, and indicates that the distance between the two microstrip lines has an optimum length for suppressing higher order modes. A prototype transition exhibits an insertion loss of 0.5 dB from 76 to 77 GHz, and a bandwidth of 6.9% (5.29 GHz) for the reflection coefficient below -15 dB for the waveguide port. [ABSTRACT FROM AUTHOR]

A design for an optically reconfigurable printed dipole antenna is presented. A wideband coplanar waveguide (CPW) to coplanar stripline (CPS) transition is used to feed the balanced printed dipole. Two silicon photo switches are placed on small gaps in both dipole arms equidistant from the centre feed. Light from two infrared laser diodes channelled through fiber optic cables is applied to the switches. With the gaps in the dipole bridged, the antenna resonates at a lower frequency. Measured return loss results that compare well to the simulated values are also presented, showing a frequency shift of nearly 40%. The change in bore-sight gain along with radiation patterns are also presented. Activating each switch individually results in a near 50° shift in beam s. [ABSTRACT FROM PUBLISHER]

Microstrip conductor loss exhibits complicated behavior that is not generally recognized. Specifically, there are three frequency ranges of interest. At low frequency, current is uniform through the entire cross-section of the line, and the line behaves like a resistor. At medium frequency, the edge singularity forms. In this case, current concentrates on the edge of the line, increasing the resistance. At high frequency, the current splits into two sheets of current, one on top of the line, the other on the bottom of the line. Since microstrip dispersion causes the edge singularity to become larger and current to concentrate on the bottom side as frequency increases, the total resistance increases faster than the normally expected square root of frequency [ABSTRACT FROM PUBLISHER]

A new dual‐mode differential bandpass filter on a squared microstrip ring resonator with a slotline feeding scheme is presented. This filter consists of a microstrip dual‐mode ring resonator, four identical slotlines equally spaced along the ring and two differential‐mode microstrip line to slotline transitions. By perpendicularly installing the slotline between the differential feeding line and the ring resonator, the coupling strength between them can be dramatically increased as desired. More importantly, only the differential modes can propagate along the slotline, so the proposed filter can naturally block the common modes (CMs) from propagation and achieve good CM suppression. To verify the design concept, a filter has been designed and fabricated. Good agreement between simulated and measured results is attained. [ABSTRACT FROM AUTHOR]

ABSTRACT The design of a planar out-of-phase power divider with broadband behavior is presented. The proposed device uses broadside coupled microstrip-slotline-microstrip transitions at the input port and coupled microstrip lines with shunt open-ended stubs at the output ports to extend the impedance matching bandwidth at three ports of the device. Moreover, a dumbbell-shaped slot is located underneath the coupled lines and shunted with a proper chip resistor to improve the isolation between the output ports. The utilized structure is suitable for single layer integration as both the input and output ports are located at the same layer. Following a proper theoretical method based on the even-odd mode approach and slotline design guidelines, a prototype of the presented device aiming to operate across the band 1-3 GHz is designed, built, and tested. The developed device has overall dimensions of 30 mm × 60 mm using the substrate Rogers RO4003 (dielectric constant = 3.38 and thickness = 0.406 mm). While the device can be used for any wideband application, the developed prototype is designed to operate within the band 1-3 GHz, which is used in most microwave-based medical imaging applications. The achieved simulated and experimental results show 100% fractional bandwidth (1.1-3.3 GHz) assuming 15 dB of isolation as the reference. The proposed device has equal power division between the two output ports with less than 0.2 dB amplitude imbalance. Moreover, the phase difference between the signals at the two output ports is 180° ± 1° across the frequency band 1-3.5 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2216-2218, 2015 [ABSTRACT FROM AUTHOR]

In past years, a great number of substrate integrated circuits have been developed. Among these new transmission lines, the substrate integrated waveguide (SIW) has received special attention. Although the quality factor and losses of these new integrated lines are better than the planar circuits, these characteristics are worst than in the case of waveguides, mainly due to the presence of dielectric substrate. To improve the performance of the integrated circuits, a new methodology for manufacturing the empty waveguides, without dielectric substrate, but at the same time completely integrated in a planar substrate, has been recently proposed, resulting in the novel empty SIW (ESIW). A low‐cost and easy to manufacture thru–reflect–line calibration kit for de‐embedding the effect of connectors and transitions when measuring ESIW devices is presented. Results prove the high quality of this calibration kit. [ABSTRACT FROM AUTHOR]

A design method is introduced for microstrip transitions between microstrip lines and parallel plate regions. The radiation impedance of an aperture radiating into a two-dimensional region (i.e., parallel-plate region) is obtained by the FDTD method, and then a multisection matched transition is designed between this aperture and a microstrip line. Numerical study of a sample design has shown that the 20 dB return loss bandwidth is about 40% for a two-section transition. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 81–84, 1999 [ABSTRACT FROM AUTHOR]