Broadband Millimeter-Wave In-Phase and Out-of-Phase Waveguide Dividers with High Isolation

In this paper, two novel broadband in-phase and out-of-phase waveguide power dividers with high isolation are presented. Based on the substrate-integrated waveguide (SIW) divider and SIW-to-waveguide transition circuit, two kinds of E-plane waveguide dividers have been implemented. Due to the features of in-phase and out-of-phase performances, the proposed waveguide dividers can provide much more flexibilities than that of conventional E-plane waveguide T-junction. A broadband phase and amplitude performances are achieved across the whole Ka-band owing to the wideband characteristic of the SIW divider and transition circuits. To minimize the size and loss of the divider, a compact and low-loss SIW-to-waveguide transition circuit has been developed using the antisymmetric tapered probes. Two prototypes of the Ka-band waveguide dividers, including the in-phase and out-of-phase types, have been fabricated and measured. Measured results show that the isolation, input return loss, output return loss, amplitude imbalance, and phase imbalance of the in-phase divider are better than 15.5, 13.1, 10.8, 0.4 dB, and 3.5⁰, while those of the out-of-phase divider are better than 15.0, 13.4, 10.4, 0.5 dB, and 3.6⁰, respectively, over the frequency range from 26.5 to 40 GHz. The measured results agree well with the simulated ones. Considering their wide bandwidth, high isolation, good port matching performance, and compact configuration, the two types of waveguide dividers can be good candidates for broadband applications in millimeter-wave waveguide systems.     

UWB Bandpass Filter Using Microstrip-to-CPW Transition With Broadband Balun

A novel ultra-wideband bandpass filter (BPF) is presented using a back-to-back microstrip-to-coplanar waveguide (CPW) transition employed as the broadband balun structure in this letter. The proposed BPF is based on the electromagnetic coupling between open-circuited microstrip line and short-circuited CPW. The equivalent circuit of half of the filter is used to calculate the input impedance. The broadband microstip-to-CPW transition is designed at the center frequency of 6.85 GHz. The simulated and measured results are shown in this letter.     

Feed for dual-band printed dipole antenna

A dual-band printed dipole antenna is proposed for WLAN applications in the 2.4 and 5.2 GHz bands. A spur line was etched on the arms of the printed dipole to achieve the dual-band operation. The printed dipole antenna with a simplified matching network is proposed. The novel simplified feed structure consists of a pair of parallel metal strips printed on the opposite sides of the dielectric substrate and connected to a 50 /spl Omega/ microstrip line with a truncated ground plane. This feeding network does not require additional transition devices, such as a T-junction, power divider, tuning stub or microstrip-to-coplanar stripline balun.     

Design of a Compact UWB Out-of-Phase Power Divider

The design of a compact out-of-phase uniplanar power divider operating over an ultra wide frequency band is presented. To achieve an out-of-phase signal division over a large frequency range, a T-junction formed by a slotline and a microstrip line accompanied by wideband microstrip to slotline transitions is employed. The simulated and experimental results of the developed divider show a low insertion loss and good return loss performance of the three ports across the band 3.1-10.6 GHz     

相消型介质参数变化测试传感器

为测量化学溶液由于温度、浓度等外在因素的变化而导致介电常数的微弱变化,设计了相消型介电常数微小变化测量传感器。该传感器依据幅度相同、相位相反的2路信号相消的原理进行设计。该装置主要包括1个同相威尔金森功分器和1个180o反相功分器,2个功分器用2条槽线相连形成2条支路,分别是参考支路与测量支路,待测物与参考物分别放在2条支路上。通过测量2条支路相消的情况来反映待测物与参考物之间介电常数的差异。仿真结果表明,与常规共面波导测量方法相比,该传感器在观测材料参数变化方面,其传输参数的幅值灵敏度提高了18 dB以上。     

CPW无空气桥功分器设计及其在阵列天线中的应用

针对传统微带圆极化阵列天线存在带宽较窄、尺寸较大等问题,提出一种新颖的基于共面波导(CPW)槽线转换结构的无空气桥功分器,并基于此功分器设计了一款紧凑型高定向性圆极化阵列天线。设计的共面波导功分器利用共面波导奇模式方法实现了能量分配,不需使用空气桥结构及四分之一波长匹配线,因此尺寸更加紧凑,结构更加简单。利用此功分器设计的圆极化阵列天线剖面厚度仅为1 mm,轴比带宽为4.14%,阻抗带宽为7.03%;在5.8 GHz时,实测增益为8.412 dBi,在保证低剖面、小尺寸的同时,可提供足够的工作带宽以及天线增益。     

Three-way out-of-phase power divider

For the first time, a novel three-way out-of-phase power divider designed based on the double-sided parallel-strip line (DSPSL), is proposed. The outputs provide one in-phase port and two out-of-phase, which are largely insensitive to frequency variations over a broad bandwidth. The total length of the circuit is half a wavelength. The design procedure of the power divider is given. Experimental results show that the power divider can achieve good matching, high isolation, balanced amplitude, and an approximately constant phase difference from 1 to 2.6 GHz.     

定向超宽带平面天线阵列设计

设计了一种超宽带（ultra-wideband, UWB）定向平面天线二元阵列。两个圆形单极子天线单元通过T 型功分馈电网络组成二元阵。天线在-10dB 以下回波损耗从2.98～10.96GHz,绝对阻抗带宽为7.98GHz,倍频程为3.68。天线增益在3GHz,6GHz 和9GHz 时,分别为3.54dB,5.03dB 和5.67dB。天线最终尺寸为28.4×67 mm2, 厚度为1mm。有效 实现了方向图定向性,可用于远距离地面宽带通信系统。     

Analysis and applications of a new CPW-slotline transition

A novel broad-band coplanar waveguide (CPW) to slotline transition and several new CPW passive circuits based on this transition are proposed and analyzed in this paper. This transition utilizes CPW-slotline mode-conversion to convert CPW-mode field to slotline-mode field, and the transition bandwidth is broadened by the use of air-bridges. The transition consists of three parts, including a uniform CPW, phase shifter, and slotline. The phase shifter converts the CPW mode to slotline mode and the bandwidth of the transition is broadened due to the modes “bounce back-and-forth” in between the air-bridge and slotline. This new transition is used to realize three CPW passive circuits, including a CPW-fed Vivaldi antenna, CPW power divider, and side-coupled CPW-slotline coupler. The finite-difference time-domain method is employed to analyze those circuits, and good agreements are obtained with measured results     

Ultra-wideband (from DC to 110 GHz) CPW to CPS transition

A new ultra-wideband, low-loss and small-size coplanar waveguide (CPW) to coplanar strip (CPS) transition which can be used from DC to 110 GHz is presented. The proposed transition connects CPW with CPS by the reformed air-bridge. Two ground planes of CPW are tied at their ends by a line and the centre of the line is connected to the ground strip of CPS by another line. Owing to the symmetry of the proposed structure, the currents of two ground planes of CPW are combined with the same phase and transferred to the ground strip of CPS. With height of 3 μm, the signal line of CPW passes over two connecting lines and is connected to the signal strip of CPS. For the back-to-back transition structure, insertion loss <1 dB and return loss >15 dB are obtained from 0.5 to 110 GHz     

A Metamaterial T-Junction Power Divider

A metamaterial based compact microstrip T-junction power divider working at 10GHz is proposed. The metamaterial unit cell consists of microstrip gaps and via holes whose behavior is equivalent to the combination of series capacitors and shunt inductors respectively, that is, a dual transmission line (high-pass) configuration. By adjusting the parameters of these structures, the characteristics of the Metamaterial-medium can be set to achieve a desired phase shift. To validate the design, a T-junction power divider is fabricated and measured. A 70% reduction of the length of the impedance transformer, without significant performance degradation, has been achieved     

Compact Ultra-Wideband Bandpass Filters Using Composite Microstrip–Coplanar-Waveguide Structure

Compact ultra-wideband bandpass filters are proposed based on the composite microstrip–coplanar-waveguide (CPW) structure. In this study, the microstrip–CPW transitions and the CPW shorted stubs are adopted as quasi-lumped-circuit elements for realizing a three-pole high-pass filter prototype. By introducing a cross-coupled capacitance between input and output ports of this high-pass filter and suitably designing the transition stretch stubs, a compact three-pole ultra-wideband bandpass filter is implemented with two transmission zeros located close to the passband edges. To further improve the selectivity, two microstrip shorted stubs are added to implement a five-pole ultra-wideband bandpass filter with good out-of-band response. Being developed from the quasi-lumped elements, and not from the transmission lines, the proposed ultra-wideband filters have sizes more compact than those of the published wideband filters. The proposed ultra-wideband filters have the merits of compact size, flat group delay, good insertion/return loss, and good selectivity. Agreement between simulated and measured responses of these filters is demonstrated.     

Fully integrated unequal Wilkinson power divider with EBG CPW

In this paper, a CPW with electromagnetic bandgap (EBG CPW) is newly proposed for designing a transmission line with high impedance. After designing, fabricating, and evaluating the characteristic impedance of the proposed EBG CPW transmission line, it will be applied to an integrated unequal Wilkinson power divider. In the EM simulation, the EBG-CPW transmission line with 10 /spl mu/m in line width has the same characteristic impedance as a CPW with a line width of 2.5 /spl mu/m. The insertion and return losses of the fabricated power divider with a power ratio of 1 to 3 are less than -0.7 dB and -15 dB, respectively. It also has excellent isolation characteristics with more than -20 dB. The experimental results are good agreement with the simulation.     

A Broadband Substrate Integrated Waveguide (SIW) Planar Balun

A broadband planar balun is presented in this work that makes use of a substrate integrated waveguide (SIW) technique using a printed circuit board process. The proposed balun structure is able to operate at millimeter wave frequencies and it does not require any tight line coupling sections as frequently used in monolithic microwave integrated circuit balun design. In addition, this balun can be integrated with other planar topologies including nonplanar circuits made of the same substrate for achieving high efficiency. This balun structure consists of a 3 dB SIW power divider and microstrip lines that are placed on both sides of the substrate at balanced ports to obtain an 180deg phase shift. The concept is validated by simulations and measurements. Our measured results suggest that a 10 dB return loss at unbalanced port can easily be achieved across a 42% bandwidth from 19 to 29 GHz. Measured amplitude and phase imbalance between two balanced ports are within 1 dB and plusmn5deg, respectively.     

Ultra-wideband (UWB) power divider with filtering response using shorted-end coupled lines and open/short-circuit slotlines

A novel ultra-wideband (UWB) power divider with bandpass-filtering frequency response has been presented. The shorted-end coupled lines and the open/short-circuit slotlines are introduced to this presented power divider. An isolation resistor R is located across the slotline for improving the isolation between the output ports of the power divider. Based on even and odd mode analysis, an analytical model of the presented power divider structure has also been proposed. An UWB power divider with passband response has been designed, fabricated, and measured. The measured results verify the predicted attractive features. It can be seen that the presented UWB power divider can not only divide/combine the power of microwave signals, but also reject unwanted frequency signals to better regulate the UWB performance.     

Balancing networks for symmetric antennas .I. Classification and fundamental operation

Emphasis has been placed on the quality of a metrology antenna system that allows it to be represented accurately using analytical or numerical models. Central to this capability is the efficacy of the balancing networks, sometimes referred to as balanced to unbalanced transformers (baluns). In this paper, we classify three fundamental types of baluns and show that all three can be derived from the 180/spl deg/, four-port hybrid network. Balanced antennas driven from coaxial feed lines and operated in the presence of an asymmetric scatterer present an intrinsically unbalanced load to the balun. We show that in such situations the current balun is the only appropriate balun to employ. For numerous antenna metrology applications, in particular, site attenuation measurements, 180/spl deg/, four-port hybrid networks have been employed as baluns. Network relations are derived relating the so-called voltage and current baluns to the 180/spl deg/, four-port hybrid network. It is shown that, in addition to acting as a 0/spl deg/ or 180/spl deg/ power divider, the hybrid network can serve as either a voltage or a current balun depending on the termination at the isolated port. In contrast to the traditional approach, it is shown that when using a 180/spl deg/ hybrid as a balun, the isolated port should be terminated in such a way that the hybrid behaves as a current balun as opposed to a 180/spl deg/ power divider. This will yield experimental results that can be more readily reconciled with models.     

An input-impedance-based circuit model for coplanar waveguide-to-slotline T-junction

In this paper, an analytical input impedance formula is presented to characterize the coplanar waveguide (CPW)-to-slotline T-junction. Based on this impedance formula, one may establish a new circuit model for the T-junction, which may describe both the discontinuity effect and the mode conversion effect between even and odd CPW modes. This circuit model is validated by measurement and is then applied to design the back-to-back CPW-to-slotline and CPW-to-coplanar stripline transition structures.     

Broadband Via-Free Microstrip Balun Using Metamaterial Transmission Lines

A novel metamaterial broadband microstrip balun design is proposed. The broadband balun consists of a pair of identical metamaterial transmission lines. In the odd mode, a virtual ground is formed between the symmetric plane. The odd mode is allowed while the even mode is rejected. No vias are required to realize the shunt inductors of the metamaterial lines, and no power divider is used. Baluns with good performance can be achieved. In this letter, two baluns are fabricated and measured. For the balun with seven units, the output amplitude difference is less than 0.7 dB, and the differential phase is 181deg plusmn 3deg from 1.6 to 3.6 GHz, while the input return loss is greater than 10 dB.     

180/spl deg/out-of-phase power divider based on double-sided parallel striplines

A novel 180deg out-of-phase power divider based on double-sided parallel striplines (DSPSL) is proposed. The proposed power divider has a relative bandwidth of about 100%. The 180deg out-of-phase characteristic between the two output ports is frequency independent, which is suitable for various applications of wide bandwidth. In addition, the characteristic impedance of the transmission lines for the input and output is 50 Omega, and it allows easy integration with other microwave components. The proposed power divider has been demonstrated and verified. The experimental results are presented and show good performance     

一个微波小型化超宽带高功率分配网络

为了实现微波功率分配领域对超宽带和高功率的双重应用需求,本文呈现了一个小型化超宽带高功率的悬置带线四路功率分配网络。它采用了一种超宽带功率分配结构,避免了传统Wilkinson电路带宽限制,并结合了低阻抗集成传输线的高功率容量的特点,具有小型化、超宽带、高功率、低插损的特点。仿真设计结果表明：在2-18GHz频段内,该结构的插入损耗小于0.6dB,回波损耗优于9.5dB（在2.75-18GHz内回波损耗优于15dB）,端口幅度差小于0.1dB,相位差小于1度。