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Gas permeability is an important parameter in the determination of the pore structure characteristics of loess, especially in engineering fields such as earthwork and landfill cover treatment. With an improved ZC-2015 air permeameter, the air permeability (ka) testing under different water contents (w), dry densities (ρd) and wetting paths was conducted on remolded Q3 Malan loess from the Chanhe River area in Xi’an, Shaanxi, China. The results indicate that the ka of the remolded loess decreased rapidly as ρd increased and exhibited a relatively complex pattern as w increased. When w was less than the plastic limit (wp) and ρd was relatively low (1.35 g·cm−3, 1.45 g·cm−3), ka decreased as we increased. When ρd reached a certain value (1.50 g·cm−3, 1.65 g·cm−3), the ka-we curve exhibited a notable turning point. When ρd continued to increase 1.70 g·cm−3, ka decreased as we increased. The results of microscopic analysis, suggested that under the action of different water content and compaction, levels of aggregates and pore structures were formed. A Poulsen model was used to predict the ka and the test results were in relatively coincident with the calculation results, demonstrating that the Poulsen model is applicable.

One kind of interembedded metasurface (MS) structure is proposed and applied to realize miniaturized wideband MS antennas (MSA). Different from conventional MSA, the proposed interembedded MSs are formed by etching slots on the radiating patch with various sawtooth schemes rather than rectangular gaps. Consequently, the resonance frequency of MSA can be decreased due to introducing those interdigital-like capacitances, while obvious miniaturization can be realized accordingly. By optimizing the parameters of the sawtooth radiating slots, a miniaturized antenna using cross-shaped interembedded MS is proposed, achieving an impedance bandwidth of 35.08% and a high gain of about 8.25 dBi with a compact overall size of $0.66\lambda _{0} \times 0.66\lambda _{0}$ . Moreover, one further miniaturized antenna using modified cross-shaped interembedded MS is also presented, realizing a larger impedance bandwidth of 41.35% and a high gain of about 6.62 dBi with a smaller aperture of $0.48\lambda _{0} \times 0.48\lambda _{0}$ . Compared with conventional MSA, 42% overall size reduction and larger bandwidth can be obtained. The design approach may provide a feasible solution to realize compact MSAs with the unique advantages of large bandwidth, low profile, low cost, and easy fabrication. Due to above good features, the proposed antenna can be a promising candidate for applications in modern wideband wireless communication systems.

One high-efficiency power amplifier (PA) with a novel multiharmonic tuning (HT) network is presented. The second and third harmonic impedances are simultaneously controlled with a simple offset double-sided parallel strip line (DSPSL)-based output-matching network. Based on the above strategy, high PA efficiency can be achieved by mapping the fundamental and harmonic impedances to the optimum positions, while PA linearity can be improved through third harmonic suppression. The offset DSPSL is used to realize the transmission lines with extremely high impedance ratio in the multiharmonic trapping circuit. For demonstration, a PA using Cree CGH40010 GaN HEMT is designed with up to third harmonic control. The fabricated PA achieves peak power-added efficiency (PAE) and drain efficiency (DE) of 78.2% and 82.3%, respectively, while delivering 39.2-dBm output power at 1.8 GHz. Besides, the output third-order intercept point (OIP3) of the PA has an improvement of 3 dB.

A 9.8–30.1 GHz CMOS low-noise amplifier (LNA) with a 3.2-dB minimum noise figure (NF) is presented. At the architecture level, a topology based on common-gate (CG) cascading with a common-source (CS) amplifier is proposed for simultaneous wideband input matching and relatively high gain. At the circuit level, multiple techniques are proposed to improve LNA performance. First, in the CG stage, loading effect is properly used instead of the conventional feedback technique, to enable simultaneous impedance and noise matching. Second, based on in-depth theoretical analysis, the inductor- and transformer-based gm-boosting techniques are employed for the CG and CS stages, respectively, to enhance the gain and reduce power consumption. Third, the floating-body method, which was originally proposed to lower NF in CS amplifiers, is adopted in the CG stage to further reduce NF. Fabricated in a 65-nm CMOS technology, the LNA chip occupies an area of only 0.2 mm2 and measures a maximum power gain of 10.9 dB with −3 dB bandwidth from 9.8 to 30.1 GHz. The NF exhibits a minimum value of 3.2 dB at 15 GHz and is below 5.7 dB across the entire bandwidth. The LNA consumes 15.6 mW from a 1.2-V supply.

A differentially-fed dual-polarized filtering patch antenna with no extra filtering circuits involved is proposed. The filtering response is realized by symmetrically loading four short strips and a long cross-type strip, and a square ring slot to insert radiation zeros on the dual-polarized antenna element. The short and long strips can generate two transmission zeros at lower and upper band edges, respectively, leading to a sharp skirt selectivity. In addition, the long cross-type strip and the square ring slot can respectively introduce an extra resonance close to the original one, broadening the impedance bandwidth. Also, the equivalent circuit is presented to show that the two zeros can be brought by the two equivalent series resonant circuits extracted from the short/long strips resulting in the bandpass response. We may note that the proposed filtering structure owns the merits of simple, compact and complete symmetry, thus it can be well integrated with the dual- polarized antenna. Consequently, a compact and high-gain dual- polarized filtering antenna with good stopband suppression, low cross-polarization level and symmetrical radiation patterns is obtained. It can achieve an impedance bandwidth about 15% and a maximum gain of 8.4 dBi. The simulated cross-polarization level is below −40 dB, and the measured one is lower than −22 dB. Moreover, the upper stopband can be up to 2.6 ${f} _{0}$ ( ${f} _{0}$ is the center frequency of the antenna), where the stopband radiations from all the directions can be suppressed and the measured suppression ratio can reach 90%.

Aiming at high and wideband output isolation, a new topology of filtering power divider based on complex isolation impedance and surface wave mitigation techniques is proposed. Different from previously published filtering power dividers using pure resistor, an analytical design method by using complex impedance is proposed in this article. To formula the complex impedance, the LC equivalent circuit model is introduced, and the closed-form derivation is given accordingly. Based on the calculated impedance, high isolation can be theoretically realized in circuit level. However, the output isolation is limited below 20 dB in practical EM simulations. To solve this issue, the filtering power divider is further investigated in field level. To reduce the crosstalk between adjacent filtering channels, the surface wave mitigation techniques are investigated. Accordingly, a 16-dB enhancement of output isolation is realized, without sacrificing other filtering specifications. For experimental verification, a filtering power divider is designed, fabricated, and measured. A significant size reduction and 36-dB output isolation with over 500% isolation bandwidth can be observed, verifying the validity of the proposed design method.

An annular array antenna is proposed in this letter. The proposed low-profile antenna produces an enhanced gain with omnidirectional vertically polarized radiation patterns. Center-fed via-shorted circular patch antenna with omnidirectional radiation pattern can be low profile and wide bandwidth but suffers from tilted beam leading to a low gain in the azimuth plane. To improve the azimuth gain, instead of the traditional way of increasing the profile, a low-profile omnidirectional director is exploited, which is basically a passive magnetic dipole consisting of an annular side-coupling open-cavity. Several directors cooperating with the driven element form the proposed antenna, whose working principle is similar to the Yagi–Uda antenna. A prototype with a low profile of 0.11 ${\lambda _0}$ is designed and fabricated. Measured results show that the prototype can realize −10-dB impedance bandwidth of 13% (4.72–5.42 GHz) and gain of 3.72 dBi at 5.34 GHz with good omnidirectivity. Compared with that of the driven element only, the omnidirectional azimuth gain is significantly improved within the bandwidth, with the maximum gain being enhanced from −4.2 to 3.72 dBi at 5.34 GHz. The proposed antenna is designed for a portable 5G sub-6 GHz wireless channel measurement application.

In this article, a flexible cooling method based on microchannels in polydimethylsiloxane (PDMS) substrate is proposed, for those flexible and conformal circuits or systems. The proposed microchannels with various widths, depths, and quantities were designed and simulated in the software of STAR-CCM+, for performance investigation and prediction of the heat dissipation. The fabricated PDMS with microchannels was surface treated before attaching to an RF power amplifier circuits. By using an infrared thermal imager, the time–temperature curves and heat distribution of the circuit were measured and recorded, under the different cooling conditions of flow rates and microchannels. The main advantages of the proposed cooling concept are the convenience of fabrication, conformality, and flexibility, which indicates that the proposed concept is potentially to be an excellent candidate for cooling solution, to the particular applications of flexible or conformal circuits.

A novel high-performance wideband balanced bandpass filter based on transversal signal-interference techniques is proposed in this article. Two signal-propagation paths consisted of coupled lines structure are used to realize two transmission zeros for the differential mode passband. Folding coupled lines are used to reduce the size of the balanced filter, and the source–load cross-coupling lines can generate additional transmission zeros to suppress the common mode signal. To validate the design, a prototype with center frequency at 2.2 GHz for long-term evolution (LTE)-band with 3-dB fractional bandwidths of 65.4% for the differential mode is designed and fabricated.

A half-air-filled substrate-integrated groove-gap waveguide is proposed for millimeter-wave and terahertz applications. The waveguide is constructed by a ball grid array using a flip-chip technique without metallic vias with lightweight and low profile. The possible leakage perpendicular to the groove is prevented by solder balls as modeled by an equivalent circuit. Besides, an inline transition between the proposed waveguide and a microstrip line is proposed, fabricated, and measured. The design concept and working mechanism are explained. Good agreement between simulation and measurement is observed. The simulation shows that the proposed waveguide can cover the entire ${W}$ -band (70–118 GHz), and the measurement demonstrates that the proposed transition can operate at 90–98.8 GHz.

This letter presents a dual-band antenna with a large frequency ratio of 11.7 (2.4 GHz/28 GHz) by integrating an mm-wave Fabry-Perot cavity (FPC) antenna into a sub-6 GHz patch antenna. The patch with periodic slots functions as both the 2.4 GHz radiator and the partially reflective surface (PRS) of the 28 GHz FPC antenna. By properly tuning the length of the periodic slot, the PRS's reflection can be easily adjusted. As the periodic slot's length and width operating at 28 GHz are much smaller than the wavelength at 2.4 GHz, periodic slot operating at 28 GHz have little impact on the radiation of the patch. Furthermore, because of the Fabry-Perot resonance, the antenna can have a peak gain reaching 15 dBi at 28 GHz band with an easy feeding structure. For demonstration, a prototype is fabricated and experimentally verified. Note that the frequency ratio is not limited to the proposed design (11.7 for demonstration). It can be easily adjusted based on the same principle.

In this article, permittivity measurement based on open resonator technology is reviewed, and then, the hemispherical open resonator with an enlarged aperture on the curved mirror is proposed for high-frequency applications. A numerical compensate method based on frequency deviation is first proposed in detail for permittivity correction. To verify our idea, an open resonator is designed and fabricated over the frequency from 26 to 40 GHz, and some materials with known characteristics are measured based on proposed technology. The complex permittivity measurement of two transparent materials, polydimethylsiloxane (PDMS) and cyclic olefin copolymer (COC), are studied at 260 GHz. Measured results are compared with previous ones, and the discussion is provided, which shows that the proposed method probably is an efficient way for complex permittivity measurement at high frequency up to terahertz.

Fifth-generation (5G) communication techniques are growing in popularity, and 5G will become the commercial operation standard for mainland China in 2020 [1]. As the next-generation mobile communication network, 5G will not only greatly improve communication efficiency; it will also change the way people live and work. The 5G communication system contains the millimeter-wave and sub-6-GHz bands. For the sub-6-GHz band, circuits are becoming ever more compact and multifunction; thus, electromagnetic interference and multicoupling problems will greatly affect the entire system's performance [2]-[4]. In response, balanced circuits with higher immunity to environmental noises [5]-[8], lower electromagnetic interference [9]-[11], and better dynamic range [12]-[15] have attracted increasing attention in the past few years, and a large number of balanced circuits are being conceived [16], [17]. Currently, all feature differential-mode input and output terminals, so they cannot be connected directly to single-ended circuits. Balanced filters, antennas, and power dividers that can be cointegrated with balanced active circuits are required for the development of fully balanced transmitter and receiver RF chains, such as the balanced power dividers that can be connected to a Doherty power amplifier in a balanced system. In this case, balancing is only necessary at the input and output stages. It is expected that the transistor stage is still a single-ended structure, where only two amplifier devices are needed [18].

This study proposes a compact structure of the three-way Gysel power divider with arbitrary power dividing ratio, which has a significant difference from existing N-way ones with a common node in the centre of the circuit. First, existing equations are reviewed, and new analytical closed-form equations are derived according to the proposed structure. The frequency bandwidths, affected by the parameters of isolation networks are investigated in detail and optimised for performance balance. For verification, the proposed three-way Gysel power dividers are calculated, optimised and fabricated at the centre frequency of 3.5 GHz with different dividing ratios of 1:1:1 and 1:2:3, respectively. Moreover, the equations are derived to design the N-way Gysel power divider.

Double-polarized dual-band absorptive frequency-selective transmission structure (AFST) is presented, which has two passbands within a wide absorption band . Equivalent circuit models (ECMs) are presented to assist the structure design efficiently. Based on the verified ECMs, practical AFSTs are then constructed accordingly. One single-band AFST is first designed, which is realized by introducing slot and cross-frame slot (CFS) resonators in the lossy and lossless layers of one broadband absorber, respectively. As a result, one passband is achieved, while the absorption at both sides is maintained. Furthermore, by using multiple slots and CFS resonators with different resonant frequencies, two transmission poles are, respectively, achieved at 3.5 GHz and 4.9 GHz, and the dual-bandpass performance is achieved. Under normal incidence, the operating frequency bands (reflection

Compact dual-band diplexers with single-ended and balanced ports based on quad-mode dielectric resonators (DRs) are proposed in this article. Two pairs of orthogonal degenerate modes are employed not only to form four frequency channels but also to achieve high isolation of dual-band diplexer. Quad-mode field distributions and couplings with input and output probes are analyzed in detail to realize dual-band diplexer characteristics. Due to the couplings of straight probes and sharing of common input and output quad-mode DRs, multiport junctions in conventional designs are saved, and the number of resonators is remarkably reduced. Therefore, miniaturized sizes are obtained in both single-ended and balanced designs. For verification, Sub-6-GHz dual-band diplexers with single-ended and balanced ports are fabricated and measured. With only two cuboid DRs and three sets of probes, low losses in all four bands and isolations that better than 34 dB are achieved in both two designs. Moreover, the common-mode (CM) suppression of the balanced diplexer is better than 50 dB. The exhibited high in- and out-of-band performance of the diplexers demonstrates the proposed method.

A compact low-profile ultrawideband circularly polarized (CP) metasurface antenna (MSA) array is presented in this letter. The array consists of 2 × 2 sequentially rotated symmetric MSA elements and a wideband four-way feeding network providing stable phases of 0°, 90°, 180°, and 270°. By using the constructed feeding network and MSA element, the CP array can achieve an ultrawideband CP performance with a low profile of 0.05λ L . The measured results show that the proposed MSA array achieves the 10 dB impedance bandwidth of 97.2%, 3 dB axial ratio bandwidth of 83.2%, and 3 dB gain variation bandwidth of 73.8%. Compared with the other designs in published literatures, the proposed CP MSA array owns the advantages of low profile with a simple structure and good CP performance without any air gap, thus indicating a promising candidate in compact wideband wireless systems.

In this article, the design method for absorptive balanced rat-race couplers with reconfigurable power-dividing ratio is proposed for the first time. First, the differential-mode (DM) and common-mode (CM) port equivalent impedances of the eight-port balanced network is derived by the even–odd mode method under the mixed-mode isolation and matching conditions. The power-dividing ratio is tuned by changing the admittance ratio of the network components, which greatly extends the amplitude imbalance bandwidth. Then, a nonabsorptive reconfigurable balanced rat-race coupler that consists of transmission lines with adjustable characteristic impedance is proposed. Furthermore, based on the derived DM and CM port equivalent impedances, an absorptive network is designed. Finally, the absorptive reconfigurable balanced rat-race coupler is achieved by attaching the absorptive network at the balanced ports of the designed nonabsorptive reconfigurable balanced rat-race coupler. For verification, the 2-GHz nonabsorptive and absorptive reconfigurable balanced rat-race couplers are designed and measured. The measured results agree well with the simulations. For the nonabsorptive coupler, the measured power-dividing ratio is tuned from −8.5 to 8.9 dB, while the 15-dB DM matching and isolation bandwidth is greater than 370 MHz. For the absorptive coupler, the measured power-dividing ratio is tuned from −8.3 to 9.0 dB, while the 15-dB DM matching and isolation bandwidth and 15-dB CM matching bandwidth are greater than 450 and 1150 MHz, respectively. The measured 0.5-dB amplitude imbalance bandwidths of the nonabsorptive and absorptive couplers are 6%–14.5% and 7%–15.6%, respectively.

This brief presents a synthesis method to design compact low temperature co-fired ceramic (LTCC) filtering balun with harmonic suppression. To achieve wide upper stopband, the design equations are driven based on the schematic. Benefiting from the three-port synthesis method and the flexible 3-D layout on LTCC technology, the coupling matrices at the second and third harmonics are manipulated to achieve the harmonics suppression without extra circuits. Meanwhile, the coupling elements of the passband can keep their desired values. A LTCC filtering balun is designed and implemented for demonstration. A 20 dB stopband rejection from $1.2{f} _{0}$ to $4.1{f} _{0}$ is observed. Good agreement between simulated and measured results verifies that the proposed method is suitable and the LTCC technology is reliable for wide stopband filtering balun designs.

This article proposes a design methodology of dual-band outphasing power amplifier (OPA) based on two noncommensurate transmission lines (NCTLs). The devised NCTLs are used to replace the imperative reactance compensation and impedance matching networks in a conventional design. In virtue of this, the overall complexity of the combiner can be greatly reduced without sacrificing the load modulation effect. To support operations at two distinct frequencies, the conceptual NCTLs are further realized using two dual-band stub-loaded transmission lines. Comprehensive theoretical analysis is given to describe the proposed scheme and to illustrate how the electrical parameters of essential elements are determined. As a proof of concept, an OPA prototype operating at 2.6 and 3.5 GHz is fabricated. The implemented PA based on two 10-W GaN high electron mobility transistor (HEMTs) achieves 44.8 and 44.2-dBm maximum output power, and 74.5% and 62.1% peak drain efficiencies under continuous wave excitation at these two independent frequencies. At 6-dB output back-off points, the corresponding efficiencies reach 63.8% and 54.9%, respectively.

This article presents a simple design of a coaxial dual-band cavity filter and diplexer using stub-loaded resonators (SLRs). Based on the resonance characteristics of a coaxial SLR, the first two resonant frequencies can be tuned over a wide range by adjusting their structural parameters. Controllable external quality factors can be acquired by using the modified tapping structure for the two designated passbands. A coupling window and a coupling pin are proposed to obtain the expected coupling coefficients in the two bands. To demonstrate this concept, a third-order dual-band bandpass filter and an eight-pole diplexer are designed and fabricated. The measured results agree well with the full-wave simulation results.

This brief presents compact low temperature co-fired ceramic (LTCC) bandstop filters (BSFs) using internal coupled lines. The inband transmission zeros pair (TZP) is generated by introducing internal coupling. According to the guidelines obtained by theoretical analysis, the bandwidth could be flexibly controlled. Furthermore, the roll off and the passband performance can be improved. To demonstrate the proposed method, LTCC BSFs with narrow and wide stopbands are implemented and measured. The broadside couplings on LTCC multilayers technology are employed to realize the internal couplings and the TZPs. The good consistency of the simulated and measured results supports that the proposed method is suitable not only for the narrow- but also for the wide-band BSF designs.

This letter presents a dual-band, dual-polarized antenna array arrangement for low grating lobe base-station antenna applications. The presented array arrangement uses two different lower band elements to achieve a 2.5-time element spacing array scheme, in which lower band elements spacing is 2.5 times of upper band elements spacing. With this arrangement, both the lower and upper band element spacing can be reduced, leading to a better grating lobe performance. To verify the idea, an antenna array operating at two bands, namely, 690–960 and 1690–2690 MHz, is presented. For 690–960 MHz array, two different radiation elements are designed, each of them has two pairs of bent dipoles for dual-polarization operation. The smaller lower band element is embedded with one upper band element. Meanwhile, the larger one is embedded with two upper band elements. An array consisting of five lower band elements and 12 upper band elements is fabricated and tested. Measured results show that the array has a good performance with return loss larger than 15 dB, ports isolation better than 28 dB. Besides, the grating lobe value is better than –12 dB at tilt angle 12° for both upper and lower band, which is a significant improvement over its former counterparts.

This article presents a wideband ±45° dual-polarized six-element antenna array with stable radiation pattern for base-station applications. Each element consists of four folded dipoles, a parasitic patch, and a convex-shaped reflector. To generate ±45° dual-polarized radiation pattern, the four close-in folded dipoles are arranged uniformly in a square shape and excited simultaneously by two integrated baluns. The parasitic patch is placed above the folded dipoles to enhance the impedance bandwidth for reaching 64.7% (VSWR < 1.5 within 1.4–2.77 GHz), while the reflector is designed in a convex shape to stabilize the horizontal radiation pattern. To further optimize the horizontally 3 dB beamwidth in the whole frequency band, six antenna elements are divided into three element pairs. Each element pair consists of two antenna elements which are misaligned in the horizontal plane. Using this method, the 3 dB beamwidth is stabilized within the range of 65.7° ± 3.2°. The impedance bandwidth is measured to be 64.8% (1.39–2.76 GHz) for VSWR < 1.5. Port-to-port isolation of 27 dB and side-lobe level better than 16 dB are obtained. These results make the proposed design attractive in wideband base-station applications.

A half-power beamwidth (HPBW) extended patch antenna with harmonic suppression is proposed in this article. The antenna consists of one driven patch and two parasitic patches. The parasitic patches are placed parallel to the two adjacent edges of a driven patch. By introducing four sets of shorting pins near the outer edges of the patches, surface currents on the patches flow through the pins to the edges of the ground plane periodically, making those edges radiate as electrical dipole elements. Huygens’-like radiation with extended HPBW and low back-lobe level is formed by the interaction of dipole and patch-like radiation sources. On the other hand, the resonance at the second harmonic frequency is suppressed, and resonances at higher order modes are shifted away from the third harmonic frequency because of the joint effect of introducing shorting pins and coupling between patches. The mechanism of the antenna is analyzed. A verifying prototype is implemented. In the measurement, the antenna operates at 5.23 GHz. HPBWs of 135°/132° are found, while front-to-back ratios of 13.5/13.3 dB are achieved in the XoZ / YoZ -plane. Resonances at the second and third harmonic frequencies are successfully suppressed.

As a natural foundation and fill material for construction in loess areas, there exists a significant impact on the stability of the engineering construction due to the permeation characteristics of the eolic sediment Malan loess. In this study, a series of air permeability tests were conducted for intact loess and remolded loess by using an improved air permeameter. We determined the influence of the water content, wetting and drying, dry density on the air permeability ka, and the use of microstructure models, scanning electron microscope (SEM) micrographs, and 3D super depth of field microscope micrographs to elucidate the microscopic mechanism of the air permeation. The results show that the air permeability ka of the remolded loess increased with the initial water content of remolding loess at dry density of ρd ≦ 1.6 g/cm3 increase, which is because of the formation of aggregates, and menisci water effect in loess; however, at dry density of ρd > 1.6 g/cm3, the air permeability started to decrease. The ka reduced remarkably as the water content of the intact and remolded loess increased during wetting process, and the air permeability during the drying process was always higher than the air permeability in the wetting process at the same water content. With the increase in the dry density, the air permeability of the remolded loess decreased; from a microstructural perspective, large and round pores tend to be small and elongated and irregular pores at high dry density. This paper will contribute to elucidating air permeability characteristics of loess and reducing the permeation risk in stability of the engineering construction in the Loess Plateau.

This paper presents a millimeter-wave (mm-wave) on-chip coupler with tunable power dividing ratios and constant phase response. Composed by two coupled lines, two capacitors and two series-connected varactors, the proposed tunable coupler offers broadband frequency responses for 5G applications. Theoretical analysis for wideband operation is provided. For demonstration, a millimeter-wave tunable coupler is implemented in a standard 0.13-$\mu \text{m}$ SiGe (Bi) CMOS technology and measured through an on-wafer probing system. From 24 to 38 GHz, the proposed tunable coupler shows a power-dividing ratio ranged from 0 to 6.5 dB, while maintaining an in-band return loss of better than 10 dB and output isolation of 20 dB, simultaneously. The phase imbalance is better than ±2.5° with a measured insertion loss of 1.3 dB across the entire tuning range. To the authors' best knowledge, this is the first time that an on-chip coupler with tunable power-dividing ratios is reported operating at mm-wave bands for, particularly, 5G applications.

Filtering baluns are proposed based on the hybrid cavity-microstrip structures in this article. The cavity acts as the resonator to obtain the filtering response. In the meanwhile, the microstrip feeding networks are used to excite multiple modes and achieve the balun characteristics simultaneously. The coupling mechanism between the slots and the cavities is utilized to analyze the single- and dual-band filtering baluns. Therefore, by combining the benefits of the cavities and the microstrip lines, multifunctional filtering baluns are realized. Besides, to reduce the volume and insertion loss further, a filtering balun based on the dielectric cavity-microstrip structure is presented and designed. It possesses high selectivity passband response, magnitude imbalance of 0.075 dB, and phase difference of 180° ± 0.2°. It is much smaller than that fed by the waveguide. On the other hand, it is easy to integrate with other components and robust in structure compared to that fed by the probe. Thus, the proposed hybrid structure not only maintains the high performance of the cavity but also has the flexibility of the planar circuit.

Li-Hua Zhu,1,* Jun Yao,2,* Ting Wu,3 Yan Wang,1 Chen-Wei Wang,1 Chun-Quan Xue,1 Li-Guang Wu,1 Xing-Wen Fan,4 Chao-Yang Wu1 1Department of Radiation Oncology, The People’s Hospital Affiliated to Jiangsu University, Zhenjiang, Jiangsu Province 212003, People’s Republic of China; 2Department of Gastroenterology, The People’s Hospital Affiliated to Jiangsu University, Zhenjiang, Jiangsu Province 212003, People’s Republic of China; 3Department of Pathology, The People’s Hospital Affiliated to Jiangsu University, Zhenjiang, Jiangsu Province 212003, People’s Republic of China; 4Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, People’s Republic of China*These authors contributed equally to this workCorrespondence: Chao-Yang WuDepartment of Radiation Oncology, The People’s Hospital Affiliated to Jiangsu University, Dianli Road 8 In, Zhenjiang, Jiangsu Province 212003, People’s Republic of ChinaTel +86 511 88915041Email wuchaoyang9@163.comXing-Wen FanDepartment of Radiation Oncology, Shanghai Cancer Center, Fudan University, 270 Dong’an Road, Shanghai 200032, People’s Republic of ChinaTel +86 136 51669687Email wenxingfan@126.comPurpose: Endoscopic submucosal dissection (ESD) is a widely performed procedure for esophageal carcinoma when the depth of invasion reaches the epithelium and lamina propria. However, ESD for esophageal carcinoma with depth of invasion exceeding the muscularis mucosa is controversial. This study aimed to evaluate the long-term outcomes of ESD for T1N0M0 (tumor invading the mucosa and submucosa [T1], no regional lymph node metastasis [N0], no distant metastasis [M0]) esophageal cancer.Patients and Methods: Esophageal cancer was evaluated via pathology and computed tomography (CT) in consecutive patients with negative margin and without additional therapy. A total of 84 patients were included. The mean follow-up time was 42 (range, 9– 99) months.Results: No recurrence and metastasis were detected in the M1 and M2 group. The 5-year locoregional recurrence rate and distant metastasis rate were 4.2% and 5.6% for the M3 group and were 0% and 1.4% for the SM group, respectively. The 3- and 5-year overall survival were 94.4% (M1+M2 group, 95.0%; M3 group, 95.0%; SM group, 92.9%) and 80.9% (M1+M2 group, 95.0%; M3 group, 95.0%; SM group, 92.9%).Meanwhile, the 3- and 5-year disease-specific survival rates were 100% (M1+M2 group, 100%; M3 group, 100%; SM group, 100%) and 90.8% (M1+M2 group, 100%; M3 group, 90.0%; SM group, 85.7%). The major complications were postoperative strictures, most of which were grade 1– 2. In total, two (4.8%) and one (1.2%) patient developed grade 3 and 5 late esophageal strictures, respectively.Conclusion: ESD complete resection yields low recurrence and metastasis rates in early esophageal cancer (T1N0M0). Thus, additional treatment is not necessary, and a watch and wait strategy may be reasonable.Keywords: esophageal carcinoma, endoscopic therapy, endoscopic submucosal resection, recurrence and metastasis

Novel designs of planar aperture antenna (PAA) arrays are proposed in this article, which achieve dual-polarized and high-gain performances in the 60 GHz unlicensed band. In order to achieve high gain, the original PAA is expanded to its two-dimensional array form, and the two linear polarizations share the same apertures. The two polarizations are realized by using orthogonal coupling slots excited by substrate-integrated waveguide (SIW) power dividers below. Two array prototypes with $8 \times 8$ and $16 \times 16$ radiation cells are designed and manufactured based on low-temperature co-fired ceramic (LTCC) technology for ease of integration. The simulated results show that the two antennas have −10 dB impedance bandwidth and 3 dB gain bandwidth of 57.5–65 and 57–64 GHz, respectively, with stable, no-squint, and symmetrical beams in band, which is verified by measurements. Compared with other reported high-gain and dual-polarized millimeter-wave antennas, the proposed antennas feature a low-profile, simple structure while keeping high aperture efficiency. The proposed antennas are very suitable for integration and are promising in 60 GHz short-range communication applications.

© 1963-2012 IEEE. This communication presents a low-profile wideband and high-gain patch antenna array using low-temperature cofired ceramics (LTCCs) fabrication technique for 60 GHz applications. A coupled feeding scheme is adopted so that the antenna achieves wide impedance bandwidth that covers the entire 60 GHz license-free band with a height of only 0.384 mm (four tape layers). The shorting via connecting the upper patch and ground achieves the function of a virtual ac ground plane of differential feeding. This enables the antenna element to achieve good radiation performances, including stable gain (variation less than 1 dB) and a symmetrical beam with low cross-polarization over the entire frequency band. The performances of the antenna element are comparable to that of the differential-driven patch antenna while the complex differential feeding network is not required. Furthermore, the proposed antenna element with simple and easy-to-integrate geometry is successfully extended to a $4 \times 4$ antenna array using a substrate integrated waveguide (SIW)-based feeding network. The measured results show that the impedance bandwidth of the array covers the 60 GHz license-free band. The maximum gain can reach 16.7 dBi and the radiation performances are very stable over the operating frequency band.

The concept of compact waveguide window based on the low-loss cyclic olefin copolymer (COC) is proposed in this letter, which considers the characteristics of broadband performance, transparency, sufficient mechanical strength, and simple mechanical process, by simply integrating the machined bipyramids-type COC dielectrics into the modified waveguide. To verify our idea, two waveguide windows consisting of internal dielectrics and external fixtures are designed and fabricated. The two types of waveguide windows are measured along with two strain rectangular waveguides at the Ka -band with the return loss better than 18.5 dB over the related frequency range of 42.8% and better than 20 dB over the related frequency range of 49%, respectively. The measured results show the advantages of the proposed concept, which is an excellent candidate for broadband application at a millimeter-wave frequency or higher.

© The Institution of Engineering and Technology 2019. In this study, an ultra-compact meandered grounding resonator is proposed to design two millimetre wave bandpass filters (BPFs) in a standard 0.13-μm silicon-germanium (Bi)-complementary metal oxide semiconductor (CMOS) technology. The fundamental second-order prototype, namely BPF-I, consists of a pair of proposed resonators and a pair of grounded metalinsulator- metal (MIM) capacitors. To better understand the principle of the second-order BPF-I, an equivalent LC-circuit model and theoretical analysis method are presented in this study. Based on BPF-I, the second-order BPF-II is proposed by adding the additional two pairs of MIM capacitors to improve the frequency selectivity, by means of introducing a transmission zero at lower stopband. Finally, both of the two second-order BPFs are fabricated. The measured results show a good agreement with the full-wave simulation results. The insertion loss of the first BPF-I is 1.79 dB at the centre frequency of 46.6 GHz, and the fractional bandwidth is up to 96.5%. The second BPF-II has a centre frequency at 46.8 GHz with a fractional bandwidth of 94.1%. The minimum insertion loss is 2.08 dB and the lower stopband attenuation is up to 42.7 dB. Moreover, the die sizes of the two compact BPFs, excluding the test pads, are only 0.0197 mm2 (0.104 × 0.190 mm2).

Dielectric waveguides have potential as transmission lines in subterahertz (sub-THz) applications due to their low-loss. A new application of a rectangular dielectric waveguide (RDW) for a THz superconducting receiver system for radio astronomy is investigated and demonstrated for the first time. The RDW can be used to transmit sub-THz local oscillator (LO) signals into the cryostat for driving the superconductor insulator superconductor mixer, with very low heat transfer. A series of RDWs with different lengths are fabricated. The measured average attenuation constants of the RDW are 0.034 and 0.069 dB/mm at 3.4 and 300 K measurement environments over 240–300 GHz, respectively. The double-sideband system noise temperature of the receiver system is also measured. With this LO signal feeding system, there is only 0.69 mW thermal transfer power from the 300 to the 3.4 K cold stage. Compared to traditional pumping signal feeding schemes, such as the horn-to-horn structure and beam splitter method, this approach outperforms the traditional schemes in terms of feeding flexibility, insertion loss, and thermal isolation for the cryostat. The proposed RDW can be widely applied to superconducting receivers for radio astronomy in the future.