Broad-band single-patch circularly polarized microstrip antennawith dual capacitively coupled feeds

New design of a circular microstrip antenna with dual capacitively coupled feeds for broad-band circular polarization radiation is presented. The dual feeds are with a small top-loaded disk and are connected to a Wilkinson power divider with a 90° phase shift between its two output feedlines. The radiating circular patch, printed on a thin substrate, is supported by nonconducting posts on a conducting ground plane and is excited capacitively through the dual feeds. With a distance less than 10% times the center operating wavelength between the circular patch and the ground plane, the present proposed antenna can provide an impedance bandwidth (VSWR ⩽2) of about 49% and a 3-dB axial-ratio bandwidth of about 35%. The antenna gain bandwidth, defined to be within 1-dB gain variation in the axial-ratio bandwidth, is as large as 28%, with the antenna gain level at about 7.0 dBi     

Wideband circular patch antenna operated at TM01 mode

The characteristics of a circular patch microstrip antenna with a top-loaded monopole feed are investigated. Air is used as the dielectric substrate. The distance between the radiating patch and ground plane is ~0.15λ₀. The patch is excited in the TM₀₁ mode. An impedance bandwidth (SWR<2) of 50% and an average gain of 5dBi are obtained     

Novel Broadband Circularly Polarized Cavity-Backed Aperture Antenna With Traveling Wave Excitation

A novel broadband circularly polarized aperture antenna is presented that uses traveling-wave excitation as the design concept. The antenna configuration consists of a circular radiating aperture, a backed cavity, and an equiangular tapered strip outer-fed by a microstrip transmission line. Operating with a traveling wave excitation, the proposed antenna contains inherent broadband characteristics in terms of the impedance, axial ratio, and gain performances. The presented antenna is comprehensively investigated, including the working principles, design consideration, and parametric studies. In addition, the research interests are extended to a 2$,times,$ 2 antenna array. Promising results from the experimental 2$,times,$2 array are achieved, including the 10-dB return loss bandwidth of 70%, the 3-dB axial ratio bandwidth of 50%, and the half-power (3-dB) gain bandwidth of 40% with a maximum gain about 11 dBi. The measured and simulated results are well complied with each other.      

U-slot circular patch antennas with L-probe feeding

Experimental results for U-slot circular patch antennas with L-probe feeding are presented. Using a foam layer of thickness ~0.1λ₀ as a supported substrate, an impedance bandwidth of 38% (SWR⩽2) and a gain of 6.8 dBi have been achieved. The far-field radiation patterns are stable across the passband     

L-probe proximity-fed short-circuited patch antennas

Experimental results for L-probe proximity-fed short-circuited quarter-wavelength patch antennas are presented. Using a foam layer of thickness ~0.1λ₀, as a supported substrate, an impedance bandwidth of 39% and a gain of >7.0 dBi have been obtained. The far field patterns are stable across the passband     

New Half-Hemispherical Dielectric Resonator Antenna for Broadband Monopole-Type Radiation

A new half-hemispherical dielectric resonator antenna (h-HDRA) is proposed and a two-element h-HDRA configuration is employed to design a broadband monopole-type radiator. Two half sections of a hemispherical DRA are employed to enhance the impedance bandwidth by introducing an additional resonant mode. Since the new geometry of an h-HDRA is studied here for the first time, it is characterized using simulation and experimental studies. Two closely spaced resonant modes, which in a two-element h-HDRA generate monopole-type radiation are investigated. Results for both the single and two-element h-HDRAs are presented. As much as 35% impedance bandwidth (S₁₁<-10dB) with more than 5 dBi peak gain, 99.08% efficiency and monopole-type radiation pattern has been demonstrated using a prototype occupying a compact volume measuring 0.48lambda₀ by 0.2lambda₀ approximately, lambda₀ being the wave length corresponding to the center of the impedance bandwidth     

Broadband U-shaped dielectric resonator antenna with elliptical patch feed

A dielectric resonator antenna formed by a U-shaped dielectric resonator and a conformal elliptical patch feed is proposed for wideband communication applications. Simulated results agree well with measured ones, showing good performance in terms of bandwidth and radiation patterns. The measured impedance bandwidth of S₁₁ < -10 dB is about 72%, covering the frequency range 3.82-8.12 GHz. It has a gain of 4.3-7.6 dBi over the whole operating band with a ground size of about 1.2 lambda₀ times 1.2 lambda₀, lambda₀ being the central operating frequency.     

A monofilar spiral antenna and its array above a groundplane-formation of a circularly polarized tilted fan beam

A monofilar spiral antenna is analyzed in the presence of a conducting plane reflector, using the method of moments. The circumference of the spiral antenna is chosen to be 2.3 wavelengths. A tilted beam of circular polarization is realized by superposing the fields from two active regions. The gain of the tilted beam is approximately 8 dB. The frequency bandwidths for 1-dB gain drop and 3-dB axial ratio criterions are 12% and 23%, respectively. An array consisting of the four monofilar spiral antennas is also analyzed, where the array element spacing is chosen to be 0.8 wavelength at a design frequency f₀. The input impedances of the four spirals are almost the same as the impedance of the single monofilar spiral antenna at f₀. The array radiates a tilted fan beam with a gain increase of approximately 6 dB from the gain of the single spiral antenna at f₀. The frequency bandwidth for a 3-dB axial ratio criterion is almost the same as that of the single spiral antenna     

A circular patch antenna for radio LAN's

A TM₀₂-mode circular patch antenna for the application of radio LANs is reported. An experimental prototype operating at 5.2 GHz is designed and tested. The antenna pattern is omnidirectional in azimuth and has a notch in the normal direction. A 3.3% bandwidth of VSWR ⩽2 and 4.2-dB antenna gain were measured. Experimental results agree well with theoretical predictions     

A broad-band rectangular patch antenna with a pair of wide slits

A new broad-band design of a probe-fed rectangular patch antenna with a pair of wide slits is proposed and experimentally studied. The proposed design is with an air substrate, and experimental results show that, simply by inserting a pair of wide slits at one of the radiating edges of the rectangular patch, good impedance matching over a wide bandwidth can easily be achieved for the proposed antenna. With an air substrate of thickness about 8% of the wavelength of the center operating frequency, the proposed antenna can have an impedance bandwidth of about 24%. For frequencies within the impedance bandwidth, good radiation characteristics are also observed, with a peak antenna gain of about 7.2 dBi     

Analysis, design, and optimization of InGaP-GaAs HBTmatched-impedance wide-band amplifiers with multiple feedback loops

The realization of matched impedance wide-band amplifiers fabricated by InGaP-GaAs heterojunction bipolar transistor (HBT) process is reported. The technique of multiple feedback loops was used to achieve terminal impedance matching and wide bandwidth simultaneously. The experimental results showed that a small signal gain of 16 dB and a 3-dB bandwidth of 11.6 GHz with in-band input/output return loss less than -10 dB were obtained. These values agreed well with those predicted from the analytic expressions that we derived for voltage gain, transimpedance gain, bandwidth, and input and output impedances. A general method for the determination of frequency responses of input/output return losses (or S₁₁, S₂₂) from the poles of voltage gain was proposed. The intrinsic overdamped characteristic of this amplifier was proved and emitter capacitive peaking was used to remedy this problem. The tradeoff between the input impedance matching and bandwidth was also found     

一种新型高增益宽带圆极化天线阵列的设计

分析了一种具有高增益的宽带圆极化天线。每一个单元都是双面印刷偶极子,为了展宽带宽,采用了宽频带90°巴伦作为馈电网络用于给偶极子阵列馈电。在此基础上,制作了一个2×3 元小型圆极化平面阵,为了压缩尺寸,将馈电网络位于介质板的底层,该天线最高增益可以达到14.2dBi,并可以获得64%（VSWR<2）的阻抗带宽和54.5%（AR<3） 的轴比带宽。     

A Dual-Polarized Magneto-Electric Dipole With Dielectric Loading

A plusmn45^degdual-polarized magneto-electric dipole loaded with dielectric substrate is presented. This antenna is composed of shorted-circuited patches and planar dipoles and is fed by four Gamma-shaped probes. The height of a prototype antenna operated at 1.9 GHz is only 24 mm (0.15lambda_o). A wide impedance bandwidth of 24.9% is achieved. The average gain is about 8.2 dBi and the isolation between the two ports is higher than 29 dB over the operating bandwidth. It is demonstrated that the antenna performance can be improved by adding metallic side walls.     

On the Differentially Fed Rectangular Dielectric Resonator Antenna

A differentially fed rectangular dielectric resonator antenna (DRA) is studied using the finite-difference time-domain (FDTD) method. The fundamental TE₁₁₁ mode of the rectangular DRA is excited at 2.4 GHz, with a 10-dB differential impedance bandwidth (|S_dd11| < -10 dB) of ~10.4%. To verify the theory, measurements were carried out, and reasonable agreement between theory and experiment is obtained. The effects of the magnitude and phase imbalances on the DRA impedance and radiation pattern are investigated.     

On a Broadband Elevated Suspended-Plate Antenna with Consistent Gain

A design concept for elevating suspended-plate radiators is presented in this paper. The proposed antenna comprises two radiators connected by a folded feeding structure. The folded structure suppresses the occurrence of higher-order modes when the height of the antenna is elevated beyond 10% of the free-space wavelength, lambda₀ . The broadband radiating mechanism is explained. Both the simulation and measurement results show that a consistent gain of 7.2 dBi to 8.5 dBi is achieved over a frequency range of 2.3 GHz to 3.6 GHz, namely within a 44% impedance bandwidth for |S₁₁|< -10 dB. The concept is used to design two cost-effective broadband antennas covering both WLAN and WiMAX operations.     

A curved spiral antenna above a conducting cylinder

A curved spiral antenna above a finite hollow conducting cylinder is analyzed using the method of moments. The effects of cylinder length 2H and cylinder radius r_cy on the radiation characteristics of the spiral are evaluated. As 2H increases, the cross-polarization component of the radiation field in the broadside direction decreases to a constant value (approximately -18 dB). When 2H is greater than one wavelength (λ₀), the input impedance of the spiral above a cylinder of radius r_cy=0.25 λ₀ is almost constant (250-j20 Ω) with a gain of approximately 7 dB. The spiral above a cylinder of (2H, r_cy)=(2.7 λ₀, 0.25 λ₀) shows a 3-dB axial ratio bandwidth of approximately 23%, which is wider than a flat spiral antenna above a flat ground plane of infinite extent     

Shorting strap tunable single feed dual-band PIFA

RF switches are integrated to the shorting straps of a single feed dual-band planar inverted-F antenna (PIFA) to make a tunable PIFA. The L-band switch yields 0.45-dB insertion loss (IL) and 10-dB isolation bandwidth (BW) of 40% at 1.5 GHz. The tunable PIFA yields 39% impedance BW at 900-MHz band and 7.8% BW at 2000-MHz band. The measured radiation patterns are nearly omni-directional and yield a gain of -7.8 dBi at 652 MHz and 4.3 dBi at 2104 MHz.     

A proposal of broad-bandwidth vertical-cavity laser amplifier

We propose a generic vertical-cavity amplifier (VCA) using a coupled-cavity design to broaden the bandwidth. Calculations are made for cavities with GaAs-AlAs and GaAs-Al_xO₂ distributed Bragg reflectors (DBR). We found that at reasonable pumping levels the VCA increased the bandwidth by 85% (GaAs-AlAs) to 500% (GaAs-Al_xO₂) as compared to a simple two-mirror structure similar to vertical-cavity surface-emitting lasers. In particular, the GaAs-AlAs VCA shows a bandwidth of 2 nm at 6-dB signal gain, while the GaAs-Al_xO₂ VCA demonstrates a 5-nm bandwidth at 6-dB signal gain with no ripple at required single-pass power gain of ~2-2.5%. Furthermore, as large as 30-nm bandwidth in a lossless bandpass filter can be obtained     

高增益高效率的Fabry-Perot谐振腔天线研究

提出了一种采用非均匀频率选择表面（frequency selective surface, FSS）盖板以及非均匀电磁带隙（electromagnetic band gap, EBG）结构反射地板的高增益Fabry-Perot（F-P）谐振腔天线. 基于漏波理论模型,针对大口径F-P谐振腔天线设计非均匀的FSS盖板和EBG反射地板,控制衰减常数α和相位常数β,改善了口径场上幅度相位分布的均匀性,并抑制了非谐振频率时天线辐射性能的恶化,实现高增益和高口径效率的同时,保证了天线的工作带宽. 所提出的圆形F-P谐振腔天线直径为6.6λ₀,仿真增益为24.6 dBi,口径效率达67.9%,阻抗带宽为4.1%,3 dB增益带宽为3.7%;实测增益为23.9 dBi,口径效率达56.9%. 由于对口径场均匀性的设计,该天线克服了传统F-P谐振腔天线的口径效率和增益间的相互限制.     

Compact multielement Marconi-Franklin type printed antennas for millimeter wireless systems

Two novel Marconi-Franklin type printed antenna arrays, each consisting of three radiating elements arranged in a cascade configuration, are investigated. Both antennas are printed on a single high permittivity dielectric substrate and fed by SMA connectors, although coplanar waveguide (CPW) feed could easily be applied to further allow easier integration into an RF chip module. Two constructed prototypes, suitable for local-multipoint-distribution service operation in the 26-GHz band (25.5-26.5 GHz), are demonstrated. The constructed prototypes show an impedance bandwidth of about 1 GHz and a maximum gain of more than 5 dBi, with small variations (<1.8 dBi), is obtained across the achieved impedance bandwidth. Details of theoretical and experimental results showing impedance and radiation characteristics for both prototype antennas are given and discussed.