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Parasitic effects significantly interfere with systematic model‐parameter extraction, making linear fitting of spiral inductors challenging when the number of turns exceeds 6, as seen in existing works. Based on the single‐π model, we propose a parameter‐extraction technique using an additional three ladder R–L ladder network in series to more accurately predict skin and proximity effects. Compared to the latest enhanced π‐circuit model, our proposed model with parameter‐extraction technique in multi‐laps inductors accurately predicts the characteristics of series inductance (Leff) and quality factor (Q) across the self‐resonant frequency, especially at the peak. This model could be used directly for the model of the on‐chip inductor in both academic and industrial fields. [ABSTRACT FROM AUTHOR]

A new input–output matching structure is presented in this article. The proposed method is used to realize a wideband high‐efficiency power amplifier. By combining the design of input–output matching network with a band‐pass filter, the fundamental and harmonic impedances are transformed to high efficiency region. In this case, a continuous Class‐F PA with wide bandwidth and high efficiency is obtained. Meanwhile, the bias circuit is also integrated in the matching network to simplify the wideband PA topology. After experimental verification, the fabricated PA has a measured drain efficiency of 62.2%–76.5% in the range of 1.35–2.8 GHz, with an output power of 39.1–42 dBm. [ABSTRACT FROM AUTHOR]

A high gain D‐band hybrid integrated on‐chip antenna (OCA) based on a low‐cost printed circuit board (PCB) packaging technology is analyzed and designed in a standard 40‐nm CMOS process in this paper. The proposed OCA is a hybrid structure of a slotted patch OCA with off‐chip PCB ground and off‐chip dielectric resonator (DR). The proposed OCA exhibits a simulated gain of 3.5 dBi and 53% radiation efficiency at 150 GHz. The simulated impedance bandwidth is 20 GHz. The radiation performance and impedance bandwidth of the OCA are observably improved with the proposed techniques. The proposed OCA occupies 0.52 × 0.56 mm2, and addresses the highly desirable yet challenging overall design of future low‐cost integrated millimeter‐wave (mm‐Wave) and terahertz (THz) systems, which hit the mark on cost and compatibility. [ABSTRACT FROM AUTHOR]

Traditional radome adversely influences the antenna performance besides protecting the antenna from the outside environment. In this work, one co‐design of a millimeter‐wave antenna and radome using parasitic patches is presented, featuring a low profile and high gain. First, the basic influence of radome on patch antenna is investigated on a transparent and low‐loss material cyclic olefin copolymer. Then, the electromagnetic interaction between the patches and the antenna is investigated in detail to reduce the adverse effect of field reflection and phase delay. One prototype of the co‐designed radome and antenna was fabricated for demonstration. The measured results show that the entire profile of the co‐designed radome and antenna is significantly reduced from traditional 0.5–0.2 λg and the gain is enhanced by 2.4 dB. [ABSTRACT FROM AUTHOR]

One high efficiency second harmonic tuned (2HT) power amplifier (PA) with a compact multi‐harmonic tuning network is presented. The proposed design method can drive the third harmonic impedance to short‐circuit condition to achieve an ideal 2HT PA operation. Then the second harmonic impedance is controlled to proper position to improve the PA efficiency. Meanwhile, the fundamental impedance is also transferred to 50 Ω load by making the most of this tuning network. Consequently, the proposed output network can be designed to a compact size and is suitable for high frequency PA applications. For demonstration, a PA using Cree CGH40010 GaN high‐electron‐mobility transistor is designed and fabricated at 3.5 GHz. The measured results show that the PA achieves peak power added efficiency of 72.8%, output power of 41.3 dBm and drain efficiency of 80.2% at 3.3 GHz. [ABSTRACT FROM AUTHOR]

A differential magnetic field probe based on a balanced filter is proposed to improve electric field suppression. The probe comprises a rectangular metal loop for detection and a balanced filter transmission. Three 1/4λ stepped impedance transmission lines are designed between the detective part and balanced filter for impedance matching. The balanced filter can suppress the common mode signals generated by a normal electric field but has little influence on the differential signals detected by a tangential magnetic field thus, the electric field suppression of the magnetic probe can be enhanced. The measurement results show that the working frequency of the proposed magnetic probe ranges from 10 to 20 GHz, and the electric field suppression ratio is over 35 dB from 10 to 15 GHz. [ABSTRACT FROM AUTHOR]

Two wideband bandstop filters (BSFs) for single and dual-band are proposed and then extended to reflectionless BSFs based on the analysis from input impedance/admittance perspective. Also, topologies of higher-number-stopband input-reflectionless BSF are provided to broaden the design scope. Open/shorted coupled lines are adopted to obtain multi transmission zeros and desired stopband bandwidth by adjusting the even-/odd-mode impedance of coupled lines. Resistor-loaded coupled lines are connected with Port 1 to absorb unwanted signals and obtain input-reflectionless behavior. For validation of the proposed theory analysis, BSFs with corresponding absorptive prototypes are constructed and measured. [ABSTRACT FROM AUTHOR]

A kite‐shaped low‐band (LB) element loaded with mushroom‐shaped structure is proposed. The element has a bandpass characteristic for the electromagnetic wave within the frequency range of 3.4–3.8 GHz and can reduce the influence on the high‐band (HB) antenna in the dual‐band coaperture antenna. The LB elements operating in the 0.698–0.96 GHz frequency band are embedded in the massive multiple input, multiple output (MIMO) antenna. One prototype of the coaperture antenna is fabricated for demonstration. The measured results show that the pattern distortion of most of the antenna ports of the HB antenna is very small after adding the LB antenna. The maximum gain deviation of the traffic beam scanning within the range of ±60° is less than 0.57 dB, indicating that the LB element can effectively suppress scattering and is suitable for multiband coaperture base‐station antenna. [ABSTRACT FROM AUTHOR]

This paper investigates a wideband omnidirectional antenna that possesses 124.7% of fractional bandwidth. The antenna's two crescent‐shaped radiating patches and their ultrawideband matching structures are printed on two laminates that are crossly placed vertically over the ground plane. Simulation shows that the structure on a single laminate radiates an "8"‐shaped pattern on the horizontal plane. The cross formation of the two printed laminates generates an omnidirectional radiation pattern by superimposing two "8"‐shaped patterns perpendicularly. The proposed antenna is fabricated and measured for demonstration. The measured results agree well with the simulation, indicating the omnidirectional antenna works from 1.38 to 5.95 GHz with a return loss of −10 dB. Simulation and measurement also show the gain variation on the xoy plane is 2 dB in the band of interest, which is small if the ultrawide bandwidth is considered. The above features make the proposed antenna a promising candidate for applications in the digital cellular system (DCS1800), long‐term evolution (LTE2300/2600), wireless local area network (WLAN2400), and IEEE 802.11p. [ABSTRACT FROM AUTHOR]

In this letter, a wideband low noise amplifier (LNA) using noise‐canceling topology and gm‐boosting technique is proposed. The noise‐canceling topology is used in the common gate (CG) amplifier to achieved better noise figure (NF) and wideband input matching. Meanwhile, the requirement of the input transconductance can be obviously decreased due to the application of gm‐boosting technique, which effectively alleviate the trade‐off between power consumption and voltage gain. The 3‐dB bandwidth of the LNA is from 2.1 to 4.1 GHz, covering widely used 5 G wireless communication frequency bands (n1, n7, n38, n41, n66, and n78 bands). The proposed LNA shows a flat and low measured NF of 3.3–3.6 dB within the operating bandwidth, while the peak power gain is 18.7 dB. The power consumption of this circuit is 16 mW with 1.2 V supply voltage, and the core area of the circuit is 0.066 mm2 with only one inductor for the whole chip. [ABSTRACT FROM AUTHOR]

This letter investigates the coupling between two parallel‐placed polytetrafluoroethylene (PTFE) dielectric waveguides over the frequency band from 90 to 110 GHz. The coupling is considered under different working frequencies, coupling spacings, coupling lengths, and polarizations. Simulations and measurements are carried out, and the results indicate the coupling can be significantly reduced by increasing the operating frequency and coupling spacing and adopting vertical polarization (VP) for a specific coupling length. In particular, the simulated and measured results with a 9‐mm coupling distance under two polarization states can be kept under −30 dB for 50‐ and 100‐mm coupling lengths, leading to negligible interference. In the practical arrangement of PTFE dielectric waveguides working at the other frequencies, one can follow the same rule to reduce the coupling between waveguides and thus avoid interference. [ABSTRACT FROM AUTHOR]

A novel windmill‐shaped metasurface (MTS) structure is firstly presented and applied to realise broadband antennas with stable radiation patterns. Different from conventional square MTS structure, the proposed windmill‐shaped MTS structure is formed by etching several triangular sawtooth slots instead of rectangular slots on the radiating square patch. Through the characteristic mode analysis, it can be found that the proposed MTS structure exhibits a much stable broadside radiation within a large bandwidth of 45.9%. Besides, the tapered edges resulted from the sawtooth slots can be regarded as smoother transitions, which would bring a better impedance matching. Based on above analysis, two antennas with different aperture sizes using the proposed windmill‐shaped MTS are well designed accordingly. Both antennas demonstrate the capability to achieve large impedance bandwidths over 40% and stable radiations (2‐dB gain bandwidth >33%). Compared with the conventional MTS‐based antenna, these proposed antennas improve the bandwidth and radiation performances effectively, showing great promises for modern wireless communication systems. [ABSTRACT FROM AUTHOR]

A lightweight wideband honeycomb absorber is theoretically and experimentally investigated. The proposed absorber is constructed of aramid paper, which contains carbon fibers to absorb partially the incident electromagnetic wave. Graded silver paste circuits are also printed on aramid paper to improve the impedance matching properties and, thus, achieve wideband absorption performance. An absorber sample was fabricated and measured to verify the design strategies. The designed absorber has a fractional absorption bandwidth of 133% from 3.6–18 GHz, with a thickness of 0.19λL at the lowest frequency. The total weight of the absorber is 18.2 g, with a density of 28.4 kg/ m 3 . [ABSTRACT FROM AUTHOR]

This Letter reports a millimeter-wave low-loss on-chip metamaterial based on a concept of a non-periodic composite right-/left-handed (CRLH) transmission line (TL). Compared with a classic periodic unit cell, a non-periodic CRLH TL is proposed to obtain higher transmittance and better reflectivity. First, based on the CRLH TL theory, the LC values of the periodic transmission line were calculated. Second, Ti factors were derived using Chebyshev low-pass filter prototypes and the bandpass transformation theory. Third, these values were then used to calculate the factors of the non-periodic structure, which was eventually implemented using lumped elements. By analyzing the dispersion property, the proposed non-periodic CRLH metamaterial features both right-handed (forward wave) and left-handed (backward wave) propagating modes, which accounts for its wide bandwidth. For demonstration, a gallium arsenide-based integrated passive device process is adopted. As its main advantages, the fabricated metamaterial shows a high and flat transmission with minimum insertion loss of 0.68 dB at 30.2 GHz, and a low reflectivity better than −10 dB from 14 to 51 GHz of which the fraction bandwidth is over 120%. [ABSTRACT FROM AUTHOR]

A novel 24 GHz circularly polarised metasurface rectenna for wireless power transmission is designed in this study. Based on experimental measurements and retro‐simulation, an effective approach is proposed to extract the parasitic parameters of a Schottky diode. A highly efficient millimetre wave rectifier with a measured efficiency of 63% is constructed based on the exact equivalent circuit parameters of a diode. A circularly polarised metasurface antenna is adopted as the receiving antenna, and the gain is enhanced by introducing metal vias around the metasurface. The antenna and the rectifier are connected directly via a microstrip line. Measurements show that the metasurface antenna has a gain of 11.3 dBic and an axial ratio of 2.5 dB at 24 GHz. The measured conversion efficiency of the rectenna reaches 63% at 300 Ω load when the input power is 15.2 dBm. The rectenna has the advantages of low profile, which can be conformal to the electrical equipment. [ABSTRACT FROM AUTHOR]

With the fast development of next-generation wireless communication and radar sensing, the millimeter-wave frequency band is becoming more and more important due to its rich spectrum, wide bandwidth, and ability to support the miniaturization of antennas and circuits , , ,. High-performance, low-loss, and low-cost millimeter-wave circuits and modules are the key elements for wireless front-end systems. For planar transmission lines, such as microstrip lines and coplanar waveguides, they are very easy to integrate with other circuits for low-cost and low-profile physical designs. However, the high insertion loss and radiation loss from planar transmission lines limit their applications at the millimeter-waveband. As for rectangular and cylindrical waveguides, their main application is in the areas of low loss and high power handling, but their 3D structure is difficult to integrate with other planar passive and active circuits. The substrate-integrated waveguide (SIW) is a better way to merge the advantages of planar transmission lines and rectangular waveguides, but it still suffers from dielectric losses at the millimeter-wave frequency range. [ABSTRACT FROM AUTHOR]

What is the impression of the word she when it comes to your mind? Smart or sensitive? Humble or helpful? Excellent or emotional? How can we build a more gender-inclusive society in the field of science and technology by benefitting from the contributions of women? To address these topics, a special session of Women in Microwaves (WiM) and Wireless was held on the afternoon of 14 August 2022 in Harbin, China, along with the 2022 IEEE Microwave Theory and Technology Society’s IWS2022, one conference among the 2022 China Microwave Week. The special session was organized by the MTT-S WiM subcommittee. More than 30 people attended this event in person or virtually, including graduate students and male and female scientists in the area of microwave technology (). [ABSTRACT FROM AUTHOR]

This brief presents a three-stage wideband power amplifier (PA) monolithic microwave integrated circuit (MMIC) using 100 nm GaN-on-Si process. A synthesized matching strategy is introduced to achieve high efficiency and improve gain flatness over a wide operation bandwidth. For demonstration, one monolithic microwave integrated circuit (MMIC) PA working from 24 to 29 GHz is designed, which covers the typical 5G millimeter-wave (mm-wave) bands. The measured output power reaches 30 dBm and the measured power added efficiency (PAE) exceeds 27.6% over the frequency range of 24 to 29 GHz. Meanwhile, the peak PAE of 40.6% and the peak power of 31.3 dBm are obtained at 27.5 GHz. Besides, the PA shows a measured gain of 18.7 to 21.2 dB from 25 to 30.5 GHz, with gain flatness of ±1.26dB. [ABSTRACT FROM AUTHOR]

In this article, a millimeter‐wave frequency‐reconfigurable metasurface antenna by electrically controlling vanadium dioxide (VO2) is proposed and studied. As a phase change material, VO2 is an insulator at room temperature but can turn into high conductivity metallic state when activated by continuous direct current (DC) voltage. By integrating the VO2 film between two simple rectangle metasurface cells, a frequency‐reconfigurable paired metasurface structure (FRPMS) is achieved. The FRPMS can be considered as one unit when VO2 film is activated to metallic state while as two independent cells when VO2 film is in insulating state. In this way, the FRPMS can operate, respectively at 28 and 38 GHz with independent tunability. Moreover, a coplanar and staggered DC bias circuit with little effect on radiation is designed to switch the operating modes of VO2 easily. The antenna is fed by a stepped waveguide with ridges through a loop slot, which is suitable for dual‐band feeding with large frequency ratio. One prototype is fabricated and measured for demonstration. When the VO2 film is in metallic state, the measured working band covers from 28.5 to 29.6 GHz with the maximum gain of about 7.1 dBi. When cooled down to insulating state, the antenna can work in a higher band from 36.7 to 38.3 GHz with the maximum gain of about 7.9 dBi. Due to the advantages of simple structure, high gain and easy tuning, the antenna can be expected to use in mmW wireless communication. [ABSTRACT FROM AUTHOR]

In this letter, a novel broadband compact circularly polarized antenna is proposed, which consists of a novel 4 × 4 cross‐layer metasurface (MS) structure and a slanted slot fed through microstrip line. The cross‐layer MS structure is formed by loading several cross‐layer stacked patches along one dimension of traditional square MS structure, and these stacked patches are located below the gaps of the original square patches directly. Compared with traditional square MS structure, the proposed cross‐layer MS structure can be viewed as one polarization‐dependent MS, exhibiting different reflection features in two orthogonal dimensions. Then, by properly tailoring the phase difference of the polarization‐dependent MS structure between the two orthogonal dimensions and combining it with a slanted coupling slot, two degenerate modes can be generated and then a wideband circular polarization radiation can be realized. Furthermore, the proposed antenna has a much compact aperture size of 0.41λ0 × 0.41λ0 due to the cross‐layer stacked patches, which can also enlarge the total capacitance by introducing extra cross‐layer capacitances. Finally, measured results show that the −10 dB impedance bandwidth of the proposed antenna is 39.6% (5.82 ~ 8.69 GHz), and 3‐dB axial ratio bandwidth is 26.3% (6.51 ~ 8.48 GHz) with a peak gain of 5.81 dBi. The simulated and measured results are in good agreement to verify the good performance of the proposed antenna. [ABSTRACT FROM AUTHOR]

A novel bandwidth enhancement method using loading multiple parasitic structures to realize broadband miniaturized antenna is proposed. Based on the proposed strategies, one miniaturized wideband dual-polarized dipole antenna covering LTE/CDMA/GSM bands (690–960 MHz) for base-station application is designed. The antenna consists of two folded bowtie-shaped dipoles fed with a pair of crossed baluns, and is further loaded on a ceramic block with high permittivity ($\varepsilon$) for miniaturization. A parasitical square loop is loaded for bandwidth enhancement at a lower frequency. In addition, four split rings with a small square loop are firstly adopted for antenna resonance tuning, the impedance bandwidth is thus improved effectively. The antenna size is only $0.18\,\times \,0.18\,\times \, 0.22\,\,\lambda _{0}$ at the center frequency. The measured result of the fabricated prototype exhibits a relatively large operation bandwidth of 32.73% (VSWR < 1.6) with stable radiation patterns and relatively flat broadside gains. Moreover, to verify the feasibility of the proposed miniaturized antenna element in the base-station application, an array of $2\,\times \, 4$ is further designed. The measured results of the array indicate isolation over 20 dB with an impedance bandwidth of 32%. Due to the good performance and compact feature, the proposed miniaturized broadband antenna element can find large application potential in multiband wireless communication base stations. [ABSTRACT FROM AUTHOR]

A novel coupling-cancellation method by loading planar path is proposed and applied in the millimeter-wave phased array for wide-angle scanning. By employing the improved decoupling stubs with weak radiation first, an extra introduced wideband equal-magnitude and anti-phase path is generated to cancel the inherent coupling path. The principle of the proposed method is investigated by the equivalent circuits and the full-wave simulation. Based on this method, a high-isolation 1-D phased array using low-temperature-cofired ceramic (LTCC) process is designed and fabricated. The planar paths are placed symmetrically between the subarrays and its radiation polarization is coincident with the antenna elements, resulting in high isolation and enhanced boresight radiation null-fill of subarrays. The measured isolation is below 20 dB within the relative bandwidth of 16.7% and the maximum scanning angle is ±60°. Moreover, the proposed method can be expectedly extended to large-scale arrays. [ABSTRACT FROM AUTHOR]

This article applies the generalized multimode S‐parameters to multiport antennas and radio frequency (RF) components for CAD applications. Consider the special case of impedance matching which could significantly simplify the multimode representation on port and remove the requirement on calculating port impedance. N single‐ended ports of a network are regarded as one generalized multimode port, supporting N orthonormal modes represented by N orthonormal basis vectors, respectively. By doing this, in antenna and RF component designs, one can only focus on specific modes interested, while ignore others. A multiport network's characteristics could be represented and understood in a much simpler manner because fewer but more intuitive physical quantities are considered. Therefore, this can significantly simplify the analysis, design, and optimization of multiport networks. For better illustration, several examples, including branch‐line coupler, mixed‐mode case, sequential rotation feeding antenna, and monopulse feed are analyzed and designed. Complicated analyses in network design using the single‐ended S‐parameters, including matching, amplitude and phase unbalance, could be converted into much simpler ones from the generalized multimode perspective. [ABSTRACT FROM AUTHOR]

This communication presents a millimeter-wave wideband dual-polarized low-temperature cofired ceramics (LTCC) antenna array based on metasurfaces (MSs) for beam-scanning applications. Benefiting from the wideband and large-freedom property of MS-based structures, a novel ±45° dual-polarized wideband MS-based antenna (MSA) element with high isolation is designed. The antenna element is fed by two orthogonal striplines on different layers, through a crosslike dog-bone slot and a narrow slot, respectively, to realize the two polarizations. The feeding structure consists of slot–stripline–slot–stripline from top to bottom and is specially designed to improve the polarization isolation of the antenna element. The proposed MSA element is compactly arranged with a small distance ($ < 0.5\lambda$) to construct a 4 $\times $ 4 array integrated in an LTCC package, where via walls with metal ring strips are loaded between adjacent elements to reduce the gain fluctuation. Consequently, the array can achieve a good beam-scanning capability over a wide band of 19.5% with a maximum scanning angle up to ±55° and a small gain variation of less than 3 dB. Meanwhile, the active $S$ parameters almost always remain below −10 dB, enabling good impedance matching when scanning at all angles. With these features, the proposed design has potential for application in 5G base-station systems. [ABSTRACT FROM AUTHOR]

This article presents a Ka-band switchable filtering power combiner monolithic microwave integrated circuit (MMIC), which unifies the functionalities of the switch, bandpass filter, and power combiner. For effective integration, a codesign approach is proposed by sharing the switchable resonant units and coupling matrix based impedance matching technique. Moreover, this approach offers great design freedom to realize arbitrary bandwidth and power ratios. For good return loss, the input external quality factor (Qe) is ensured as half of output Qe based on even-mode analysis. By analyzing the odd-mode circuit, the complex isolation element is introduced to improve the isolation between input ports. For demonstration, one prototype is implemented using a 100-nm GaN-on-Si process. Over 18-dB return loss, 1.7-dB minimum insertion loss (excluding 3-dB power ratio), >22 dB input–input isolation, and over 47-dB off-state isolation can be observed throughout 24–32 GHz. Besides, the proposed MMIC shows good linearity with a measured IP1dB of over 30 dBm within the passband, while the die size is 0.81 mm2. [ABSTRACT FROM AUTHOR]

An ultrawideband dual-polarized antenna for fifth generation (5G) customer premise equipment is investigated and designed in a compact environment by using a double-loop-dipole structure and a co-planar-slot feeding concept. First, the existing design of dual-polarized octagonal loop dipoles is introduced at first. Then, a novel double-loop-dipole structure and co-planar-slot feeding are proposed and demonstrated in detail from the current distribution and physical structure sides. Finally, the proposed antenna is designed, fabricated, and measured. The measured results present that the proposed antenna has a wide bandwidth of 86% from 2.2 to 5.5 GHz with the VSWR less than 1.8, high polarization isolation of 25 dB, and stable radiation patterns over the desired frequencies of 2.3–5.2 GHz. It is worth mentioning that the proposed ideas can effectively aid in impedance bandwidth improvement without adding additional cost for sub-6G 5G applications. [ABSTRACT FROM AUTHOR]

The serpentine delay line (SDL) is commonly used as one kind of typical true time delay lines (TDLs) with periodic strong reflection points (SRPs). However, the Hilbert fractal curve delay lines (HFCDLs), with the same circuit area and the same spacing between the adjacent segment lines, are proven to have quite different SRPs with improved performance. An analytic analysis model is used to investigate the SRPs of the two-order and three-order HFCDLs, respectively, in which the structure symmetry is fully considered to make the relevant adjacent structure equivalent to a pair of parallel dual lines. Thus, the accumulated far-end crosstalk (FEXT) is derived in the HFCDLs, and the implicit periodic SRPs are revealed. Furthermore, the iterated two-order and three-order HFCDLs are investigated to validate the analysis model. Subsequently, the periodically loaded transmission line (PLTL) with and without strategic discontinuous structured guard lines (DSGLs) is, respectively, utilized in the three-order and two-order HFCDLs, and thus, the proposed structures possess better wideband cancelation of the FEXT accordingly. In the ultrawideband (UWB) range of dc–51 GHz, the typical return loss (RL) is less than 20 dB for the proposed two-order HFCDL and less than 15 dB for the proposed three-order HFCDL. Meanwhile, the fluctuations are eliminated in the group delay (GD) for the proposed two-order HFCDL. For the proposed three-order HFCDL, the delay fluctuations are observed at the high end of the UWB due to the enhanced near-end crosstalk (NEXT), while the delay fluctuations less than 72.2 ps are still obtained in the range of dc–35 GHz. [ABSTRACT FROM AUTHOR]

Novel designs of paper-based bandstop frequency-selective surfaces (FSSs) are presented in this article. The characteristics of the paper-based honeycomb structure are investigated first. One folded dipole resonator with first-order bandstop response is analyzed and further printed on the sidewalls of the honeycomb structure accordingly. A second-order response with two cascade FSSs is proposed with controllable bandwidth by the coupling coefficient of the resonators with the aid of the equivalent circuit model. Two paper-based FSS samples were fabricated and measured to demonstrate the validity of the proposed design strategies. Benefiting from the merits of lightweight and strong mechanical properties, the proposed paper-based FSS is a potential candidate for application in radar systems and aircraft. [ABSTRACT FROM AUTHOR]

A low-profile and shared aperture dual-polarized (DP) omnidirectional antenna by reusing the structure of an annular quasi-dipole array is presented. The proposed antenna consists of a center-fed circular patch antenna, an annular quasi-dipole array, a wideband one-to-four power divider integrated with the center-fed circular patch antenna, and two annular strips. The center-fed circular patch antenna is utilized as the driven element for the vertically polarized (VP) radiation. The annular quasi-dipole array fed by the one-to-four power divider produces horizontally polarized (HP) radiation. Simultaneously, it also acts as the VP director to improve VP gain and bandwidth. Besides, the two annular strips enhance the HP omni-directivity and gain. In this way, the VP and HP share the same aperture to improve the profile utilization rate effectively. Due to the symmetry of the basic antenna structure, stable DP donut patterns are obtained within the entire operating bandwidth. For demonstration, a 4.1–5.0 GHz prototype is designed, fabricated, and measured. Under a low profile of $0.13\lambda _{0}$ , the prototype realizes a −10 dB overlapped bandwidth of 20%, high port isolation of above 35 dB, and stable DP donut patterns with horizontal gain larger than 1.8 dBi. [ABSTRACT FROM AUTHOR]

A planar bidirectional circularly polarized (CP) antenna using orthogonal magnetic dipoles (OMDs) without an extra phase shift line is proposed in this work. It consists of a rectangular microstrip magnetic dipole antenna (MMDA) and a loop radiator with two arms directly connected to the open edge of MMDA. The working principle is revealed by the equivalent sources model to provide a clear physical insight at first. The theoretical investigations imply that by controlling the width and the feed locations of the loop antenna on the aperture, the phase and magnitude for CP radiation can be realized in both endfire and backfire directions without introducing an additional phase shift line structure. For demonstration, one antenna prototype is designed and fabricated. The experimental results indicate that an overlapping bandwidth of 5.91% from 2.30 to 2.44 GHz is attained. Compared with the counterpart using OMDs, the proposed antenna exhibits a low design complexity and improved gains of 3.56/1.83 dBic in the endfire/backfire directions. [ABSTRACT FROM AUTHOR]

In this study, a three‐dimensional bandpass frequency selective surface (FSS) with a new fabrication technology is proposed and designed based on slotlines. The proposed FSS consists of silver paste circuits printed on aramid paper, and is vertically and horizontally arranged to form a periodic array in honeycomb structure. To better understand the design principle of the proposed FSS, the equivalent circuit model (ECM), single‐polarized structure, and dual‐polarized structure are presented and analyzed, respectively. The proposed FSS exhibits a passband at 4.1 GHz with a fractional bandwidth of 71.5% at x‐polarization and 66.2% at y‐polarization with reflectivity less than −10 dB. Moreover, the reflection and transmission coefficients have relative stable properties up to 30° for the oblique incidence. Then, the proposed structure is fabricated and measured to verify the design strategies. The measured and simulated results have reasonable agreement under a large variation of incident angles. [ABSTRACT FROM AUTHOR]

This communication presents a new multiband multiarray (MBMA) scattering suppression antenna configuration for a dual-band and dual-polarized antenna array with reduced radiation distortion. The proposed antenna array configuration consists of a low-band (LB) antenna element working in the 690–960 MHz band and four high-band (HB) antenna elements working in the 1.7–2.7 GHz band. The LB antenna introduces U-shape structures to the radiation element to neutralize HB scattering currents. On the other hand, the HB antenna involves an LC resonant structure between its radiation arm and feeding balun to suppress LB scattering currents. An antenna array using the proposed LB and HB elements is designed to achieve MBMA functions. Experimental results show that the radiation distortions in both LB and HB bands are improved significantly. The VSWR of less than 1.5, the isolation of more than 25 dB, and the symmetrical radiation pattern are obtained in both bands. [ABSTRACT FROM AUTHOR]

In this brief, two wideband bandpass filters using a novel double-row staggered double-sided quasi-SSPPs transmission line are proposed. By loading U-shaped cells symmetrically, a transmission zero can be introduced into the original operating frequency band, which forms a high out-of-band suppression wideband bandpass filter. The structure can draw an analogy with double-sided parallel stripline, and the equivalent circuit model of microstrip line can be constructed to assist analysis and design. The passband selectivity can be further improved when the number of U-shaped cells is increased from 3 to 5. The measured result of 3-dB fractional bandwidth is 18.9 % (frequency 11.4 GHz), and the in-band return loss is greater than 10.2 dB. In addition, the out-of-band suppression is greater than 20 dB in the lower stopband (from 6.18 GHz to 10.12 GHz) and the upper stopband (from 12.78 GHz to 19 GHz). [ABSTRACT FROM AUTHOR]

An simplified vector-sum phase shifter (VSPS) topology is proposed in this article. The proposed VSPS topology employs only one 90° coupler to perform as both an I/Q generator and a vector summer. Compared with the literaturally reported VSPS, the proposed VSPS features a simpler topology and improved noise figure (NF) performance. Moreover, active baluns based on the self-calibration technique are employed to provide antiphase signals and improve the gain performance of the VSPS. For demonstration, a 24–30-GHz VSPS based on the proposed topology is implemented in the 65-nm CMOS process, exhibiting 3.5° rms phase error and 0.9-dB rms gain error. The average gain of the implemented VSPS is as high as 9 dB at the central frequency of 27 GHz. The NF ranges from 4.8 to 9 dB from 24 to 30 GHz, and the core chip size is $0.36\times0.59$ mm2. [ABSTRACT FROM AUTHOR]

A novel low-profile wideband dual-circularly polarized metasurface antenna based on a traveling-wave sequential feeding mechanism is proposed. It consists of 4 × 4 rectangle metasurface cells and is excited by a simple two-port traveling-wave feeding network, which includes four rotated Z-shaped slots etched on the ground and a ring feeding line, to provide stable sequential phases of 0°, 90°, 180°, 270° for realizing dual-circular polarizations. By changing the width of four Z-shaped slots, the equal amplitude of two orthogonal electric fields can be achieved and good right- and left-handed circular polarization (RHCP, LHCP) can be realized accordingly in a wideband. Moreover, a metasurface is utilized as a radiator to improve the impedance bandwidth (IMBW) as well as radiation performance. For demonstration, one prototype with an overall size of 0.88λ0 × 0.88λ0 × 0.06λ0 centered at 5.3 GHz is fabricated and measured. The measured results show that the proposed low-profile antenna realizes a large 10-dB IMBW of 38.4% (4.33–6.39 GHz) and 46.6% (6.17–6.70 GHz), 3-dB axial-ratio bandwidth of 38.4% and 39.3%, respectively, for RHCP and LHCP states. In addition, the polarization isolation is over 12 dB in the entire band of interest. [ABSTRACT FROM AUTHOR]

One dual‐band high‐efficiency power amplifier (PA) based on a D‐CRLH structure is presented. The D‐CRLH cell is employed to realize one dual‐band second harmonic trapping for the two operation frequency bands. Based on above design strategy, high PA efficiency at two frequency bands can be achieved by transferring the fundamental and second harmonic impedances to appropriate positions on the Smith chart. For demonstration, one prototype is designed at 2.3 and 3.5 GHz by using the proposed design strategy. The results indicate one peak output power of 40 and 40.8 dBm at the measured frequency of 2.2 and 3.2 GHz, respectively, while the maximum power‐added efficiencies (PAE) are 73.9% and 64% at the two frequencies. [ABSTRACT FROM AUTHOR]

A novel decoupling method by utilizing one $1\times2$ subarray to provide a pair of phase-reversed coupling paths for coupling energy cancellation is proposed. The newly proposed decoupling approach is implemented by symmetrically loading several U-type, I-type, and cross strips around the antennas to change the original couplings, so that two elements in the $1\times2$ subarray can form a pair of phase-reversed coupling paths into adjacent element in different subarray for coupling cancellation. Then, the couplings from the subarray to adjacent element are effectively suppressed, thus the isolations between different subarrays of the array are promoted. Moreover, the method can be also applied in improving the isolation between different polarizations in the same subarray. In addition, these strips not only have little influence on radiation characteristics of the antenna array, but also can be etched on the antenna layer without extra profile and process. For demonstration, one dual- polarized patch antenna array based on the new decoupling mechanism is designed. The results indicate that all the isolations between the subarrays of the proposed dual-polarized antenna array can achieve a very high level of over 25 dB in an operation band of 3.4–3.6 GHz. Compared with other decoupling methods, the proposed method can simultaneously improve complex multiple-port isolations among different subarrays and different polarizations to realize a very high isolation with less impact on antenna radiation. Due to above features, the proposed decoupling mechanism is expected to find potential applications in 5G dual-polarized multiple-input–multiple-output (MIMO) antenna array. [ABSTRACT FROM AUTHOR]

Low-profile shared-structure dual-polarized (DP) Yagi–Uda antennas are proposed, which are formed by three kinds of basic components, namely DP driven element, DP director, and DP reflector. An open-cavity dipole is utilized as the DP driven element to generate DP endfire radiations. The quarter-wave resonance mode for vertical polarization (VP) and half-wave dipole resonance mode for horizontal polarization (HP) are excited by differential feeding structures in the DP driven element. The open-cavity element is adopted as the DP director or reflector to enhance endfire gain. For the proposed design, two polarization radiators are integrated into one structure, realizing structure sharing, and thus a low profile. Three-element (Ant. 1) and seven-element (Ant. 2) antennas with a profile of 0.1 λ0 are designed, fabricated, and measured. The measured overlapped bandwidth of the Ant. 1 is from 4.11 to 4.83 GHz (16%) with ports isolation higher than 30 dB, and the measured VP and HP gains are from 5 to 6 dBi and 5 to 7 dBi, respectively. The Ant. 2 further increases the DP endfire gain by 2–3 dBi at the overlapped bandwidth of 16.3%. [ABSTRACT FROM AUTHOR]

In this letter, we review the microwave ablation (MWA) under pulsed wave (PW) mode and perform the experiments by using a dual-frequency antenna. Parameters such as frequency (915 MHz or 2450 MHz), excitation power (40 W or 60 W), duty cycle (40%–60%), cycle (10 ms–100 s), and durations (5 min or 10) min are variably combined in different experimental schemes for investigation. Based on the results of these experiments, which use our super compact dual-frequency antenna and egg white as a reference tissue environment, it can be seen that PW MWA may reduce backward heating and increase ablation roundness to 0.964 (compared to a traditional continuous wave (CW) ablation roundness of 0.5). For further verification of these results and for comparison, a single-frequency antenna is also used under PW mode and the achieved ablation roundness is 0.91, which is also greater than that of 0.55 under CW mode. PW MWA can thus be considered as an effective candidate for tissue ablation during the treatment of tumors. [ABSTRACT FROM AUTHOR]

The novel folded substrate-integrated waveguide (FSIW) is 50% narrower than the substrate-integrated waveguide, but both have similar propagation characteristics. This paper derives the analytical formulas of propagation and cutoff characteristics of the FSIW, as well as the formulas to calculate the width and gap of the central metal septum. Very good agreements ( Index Terms--Folded substrate-integrated waveguide (FSIW), ridged waveguide, substrate-integrated waveguide (SIW).

This article presents a novel broadband dual-polarized filtering patch antenna array using low-temperature cofired ceramic (LTCC) process for 5G millimeter-wave (mmW) applications. The filtering antenna element is implemented using a ± 45° polarized patch antenna fed by two pairs of differential L-type probes. An additional square ring and open strips are connected to each probe, resulting in radiation nulls and realizing the lower/upper stopband rejection level over 24 dB with skirt selectivity. The cross coupling among these structures not only introduces filtering responses, but also contributes to broadening the passband of 24.25–29.5 GHz covering 5G n257/n258/n261 bands. The antenna performance is validated by equivalent circuits based on transmission line models, which reveals clearly the principles of filtering antenna step by step and provides guidelines for further designs. The proposed filtering antenna element is expanded to a $4\times 4$ filtering antenna array with shunt-fed feeding networks. The spacing between elements is $0.48~\lambda _{0}$. The measured results demonstrate that the array performs good filtering characters including high stopband rejection, high selectivity, and wide upper stopband up to 40 GHz, where the antenna efficiency (considering radiations from all the directions) is less than 5%. In addition, the differential feeds provide symmetric radiation patterns with low cross-polarized counterparts. Compared with other reported works, the proposed filtering antenna/array has excellent performances of wideband, high stopband rejection and wide upper stopband for potential 5G mmW applications. [ABSTRACT FROM AUTHOR]

The fabrication process of an advanced transparent cyclic olefin copolymer (COC)‐based laminate is introduced, along with the laser cutting technology for circuit pattern. Then, a three‐way Gysel divider with an equal power‐dividing ratio is reviewed, designed and measured, based on the proposed COC‐based laminate. The measured results are compared to those from a similar three‐way Gysel divider based on traditional RT/duroid 5880 laminate, from which we can see that COC‐based laminate has the advantage of lower loss, with other advantages such as low cost, easy realization, high‐precision, and even the transparency. This laminate can be an excellent candidate for a substrate at microwave or millimeter‐wave circuits. [ABSTRACT FROM AUTHOR]