Quasi-optical planar arrays with FETs and slots

This work describes the design concept and experimental results for prototypes of two-dimensional quasi-optical power-combining arrays. Several different quasi-optical circuits were used to obtain the fundamental data for this study. How to incorporate the antenna input impedance into the active antenna circuit and how to analyze the strong coupling condition with two operating modes are addressed using large-signal analysis. Several circuit configurations are demonstrated, including a single active antenna operating at 9.3 and 24.0 GHz, a six-element linear power-combining array operating at 15.6 GHz, and four-element and sixteen-element two-dimensional power combining arrays operating at 10.4 and 7.8 GHz. Important characteristics such as antenna patterns and tuning ranges are discussed. The prospects for a two-dimensional monolithic quasi-optical power-combining array are discussed     

Experiments on injection locking of active antenna elements foractive phased arrays and spatial power combiners

Two types of active antenna elements have been studied experimentally. One type uses a microstrip antenna with an active device mounted directly on the antenna. The other uses an active device coupled to a microstrip patch antenna through an aperture. Microstrip active antenna elements and two-element arrays have been demonstrated for both types of circuits. Injection locking of the antenna elements has been achieved through space and mutual coupling. The circuit Q factor was calculated based on the locking gain and the locking bandwidth. The power output from two elements has been successfully combined in free space with a combining efficiency of over 90%. For a single active antenna with a Gunn diode mounted directly on the patch, an electronic tuning range exceeding 9% has been achieved by varying the DC bias. The results should have many applications in low-cost active arrays, active transmitters, and spatial power combiners     

Single-feed circularly polarized microstrip ring antenna and arrays

An analysis is presented for a microstrip-feed proximity-coupled ring antenna and a four-element array. Interactions between the embedded microstrip feed and the radiating element(s) are rigorously included. Results demonstrate that circular polarization of both senses can be achieved with a ring antenna with proper design of two inner stubs located at angles of ±45° with respect to the feedline. Theory and experiment demonstrate an axial ratio 3-dB bandwidth of 1% and the voltage standing wave ratio (VSWR) <2 bandwidth of 6.1%. The axial ratio bandwidth is typical for a microstrip antenna with perturbations, while the VSWR bandwidth is larger than for the circular or rectangular patch with perturbations. A mutual coupling study between two elements shows that the axial ratio is less than 2 dB for interelement spacing greater than 0.55λ_eff, while the VSWR <2 for all spacings considered. A comparison between theory and experiment is provided for a 2×2 element array. The benefits of sequentially rotating the antenna elements in an array environment are presented. The axial ratio and VSWR bandwidths are both increased to 6.1% and 18% for a four-element array. A single-element antenna with two orthogonal feeds to provide both senses of polarization is demonstrated. The ring antenna is small (D/λ₀=0.325), the substrate thickness is thin (H/λ₀~0.035), and the microstrip feed produces a completely planar antenna system, which is compatible with microwave and millimeter integrated circuits (MICs), and monolithic microwave integrated circuits (MMICs)     

一种天线馈源用宽带孔径耦合层叠微带贴片阵的设计

介绍了一种宽带孔径耦合层叠微带辐射单元的工作原理,着重分析了该辐射单元主要结构尺寸对其阻抗带宽的影响。该辐射单元阻抗带宽（VSWR≤2：1）在S波段达到了30％以上。作为某抛物反射面天线的馈源,由4个该辐射单元组成四单元微带贴片天线阵后,其性能满足天线系统要求。     

Stacked quasi-elliptical patch array with circular polarisation

A simple stacked subarray antenna with circular polarisation is presented. The antenna is based on a quasi-elliptical patch antenna fed with a 45deg offset microstrip line and a circular patch stacked on top of it via an air substrate. The single-element circularly polarised antenna is sequentially rotated into a four-element synchronous subarray resulting in improvement in antenna performance in terms of impedance bandwidth, gain and axial ratio. The antenna is experimentally verified and the results are reported     

Electronically steerable Yagi-Uda microstrip patch antenna array

This paper describes a dual-frequency circularly polarized electronically steerable microstrip patch antenna array suitable for land-mobile communications. Based on a four-element Yagi-Uda (1928) patch antenna, the four antennas forming the array are located radially from a single square reflector patch on a double-sided printed circuit board. The main lobe of the array covers the elevation angles from 20 to 70° with a peak gain of 8.4 dBi at 1.54 GHz and 11.7 dBi at 1.62 GHz. Full azimuthal coverage is possible by electronically switching between the four elements     

一种寄生阵列宽带圆极化天线的设计

该文设计了一款C波段单馈寄生阵列的宽带圆极化天线。此天线采用紧邻的双层F4B介质基板,通过在方形驱动贴片上开槽及采用寄生阵列的设计实现了圆极化。对天线结构的设计步骤进行说明,研究了各结构对天线阻抗带宽和轴比带宽的影响,并研究了寄生贴片切角长度和驱动贴片上的缝隙宽度对天线轴比和带宽的影响。对天线的圆极化方向图进行了仿真。仿真结果表明,在5.5 GHz时实现了右旋圆极化,最大增益为8.1 dBi。加工并测试了宽带圆极化天线,测试结果与仿真结果基本相符,天线实测的阻抗带宽为1.3 GHz,轴比带宽为1.26 GHz。设计的叠层天线具有结构紧凑,装配简单和轴比带宽大的优点。     

Wideband compact antenna for K-band applications

A compact coupled microwave active antenna is presented. This antenna is proximity fed, and consists of a square radiating element array on a polymer dielectric layer. The compactness of the antenna is obtained through technological optical processes and the parasitic patch phenomenon which increases the bandwidth     

An efficient X-band 16-element spatial combiner of switched-mode power amplifiers

This paper describes the design, implementation, and characterization of a high-efficiency 10-GHz amplifier antenna array for spatial power combining. An average drain efficiency of 70% at 162 W effective isotropic radiated power, or about 1.5 W of transmitted power, is measured for an array of 16 amplifiers consisting of four four-element subarrays. The power-combining efficiency of the 16-element array is above 79%. The active device is a low-cost GaAs MESFET with a maximum available power in class A of 21 dBm. The single class-E power amplifier delivers 20.3 dBm with 67% drain efficiency and 58% power-added efficiency.     

Broadband probe-fed patch antenna with a W-shaped ground plane

A new design of a broadband probe-fed patch antenna with a W-shaped ground plane is presented. The W-shaped ground plane is obtained by bending the conventional planar ground plane into an inverted V-shape, seen in the resonant direction of the patch antenna and then adding proper flanges at the two straight edges of the bent ground plane. The proposed design is applicable to the patch antenna with a planar radiating patch with a thin air substrate. With the use of the proposed W-shaped ground plane, the required probe-pin length in the substrate remains small, although the effective substrate thickness is significantly increased, resulting in a much wider operating bandwidth. Also, by choosing proper dimensions of the W-shaped ground plane, the antenna gain for frequencies over the obtained wide bandwidth is enhanced, compared to the conventional patch antenna with a planar ground plane. In addition, the cross polarization is also reduced for the proposed design and the cross-polarization level (XPL) in the H-plane pattern can even be better than that of a conventional probe-fed patch antenna with a thin air substrate     

CODAR Directional Biases with a Four-Element Antenna Array

Directional biases are shown to exist for a four-element square CODAR receiving array used for coastal current mapping. The sources being sidelobes and mutual coupling (a type of pattern distortion), these nonstatistical biases depend both on the geometry/size of the square array as well as the particular closed-form algorithm employed to estimate bearing. Typical rms errors due to these sources lie between 5-15°. Reconfiguration of the four-element antenna geometry may reduce sidelobe biases when closed-form algorithms are employed, but only at the expense of increased mutual-coupling bias. A least-squares algorithm is given that corrects for pattern distortion, circumventing this shortcoming of closed-form methods; this algorithm can also improve sidelobe biases. Other antenna systems possessing no sidelobes are in use for CODAR that eliminate these sources of error.     

Integrated-antenna push-pull power amplifiers

In this paper, the integrated-antenna concept is applied to push-pull power amplifiers (PAs). In this approach, the antenna serves as an out-of-phase power combiner and tuned load for higher harmonics. This new architecture effectively has a near-zero loss output hybrid, and results in a high-efficiency PA. The first example is a narrow-band push-pull amplifier integrated with a dual-feed patch antenna. At an operating frequency of 2.5 GHz, a maximum measured power-added efficiency (PAE) of 55% is achieved. The second example is a broadband push-pull amplifier integrated with a dual-feed slot antenna amplifier operating at 2.46 GHz which has a peak PAE of 63%, and PAE better than 55% in an 8% bandwidth. Additionally, 48% PAE is achieved with code-division multiple-access modulation and adjacent-channel power ratio better than -42 dBe at a 1.25-MHz offset     

Combination dielectric resonator, power combiner, and antenna

A rectangular dielectric resonator housed in a cutoff parallel-plate waveguide is used both as a radiating element and microwave power combiner. The resonator is excited by using tuned electrically short monopole antennas to induce a longitudinal electric operating mode. The resonator is then used in conjunction with free-running oscillators in order to provide, via mutual injection locking, stable in-phase power combining. Furthermore, the resonator is arranged such that one of its faces radiates a portion of the power-combined signal. Since the resonator is housed in a cutoff waveguide, the cross-polarization radiation from the antenna is suppressed. It was found that, for a single element, a gain in the azimuthal plane of 5 dB could be achieved and, for a two-element array, a gain of 7 dB was obtained with better than -25-dB cross polarization for each case. The oscillator power-combining efficiency for a single-element antenna (two oscillators) was 91%, and the spatial power-combining efficiency for a two-element antenna array, (four oscillators) was found to be 90%. In addition, it is shown that the presence of the dielectric inserts in conjunction with coupled oscillator dynamics provides moderate overall oscillator phase noise improvement     

Stripline-fed printed square spiral slot antenna for circularpolarisation

A novel design for a circularly-polarised printed square spiral slot antenna with a stripline feed is demonstrated. The printed slot antenna consists of a square spiral slot of ~1.25 turns, and a total slot length of approximately one free-space operating wavelength. By carefully trimming both ends of the square spiral slot, circular polarisation (CP) operation with a wide operating bandwidth can easily be achieved. A CP bandwidth of >6% has been obtained     

A quarter-wave U-shaped patch antenna with two unequal arms for wideband and dual-frequency operation

A wideband and dual-frequency quarter-wave U-shaped patch antenna with two unequal arms on FR4 substrate is presented. The U-shaped patch antenna is fed electromagnetically by another coaxially-fed patch on the same layer, which operates at a higher frequency band. In this paper, we first proposed a new technique to obtain two closely staggered resonant modes to achieve a wide impedance bandwidth using two unequal arms of the U-shaped patch for the lower band. For the substrate thickness = 5, 7.5 and 11 mm, the measured bandwidths of the antennas operating around at 900 MHz are 7%, 10%, and 18%, respectively. Then, we modify the coaxially-fed patch so that both bands are wide in bandwidth. The resulting antenna operating at 900 and 1800-MHz bands with the substrate thickness 11 mm has a measured impedance bandwidth of 13.3% and 20 respectively. This thickness corresponds to 0.033 free-space wavelength at 900 MHz. The far-field radiation patterns are stable in the two operating bands. The proposed antenna is simple in structure compared with the regular stacked or coplanar parasitic patch antennas. It is highly suitable for indoor mobile communications.     

EBG结构在35GHz微带阵列天线中应用

分别采用理论计算和实验测试法分析介质基片上钻孔型电磁带隙(EBG)结构的阻带特性,得出了一致结论.依据仿真与测试结果,设计了一种同时抑制TE和TM模的EBG结构,并应用于4单元35GHz微带型阵列天线.测试结果表明:该EBG结构微带阵列天线带宽增加约1倍,增益提高了1.3dBi.     

New wideband high-gain stripline planar array for 12 GHz satellite TV

A new type of stripline planar array has been studied for 12 GHz satellite TV reception. A 16-element experimental antenna (dimensions?98×98×18 mm3), using a stripline corporate feed, presents a 2 : 1 VSWR bandwidth of over 2 GHz and a gain higher than 20.6 dBi in the 11.7?12.5 GHz bandwidth.     

Design of a compact broadband microstrip patch antenna with probe feeding for wireless applications

In this paper the design and development of a compact broadband probe-fed Microstrip patch antenna for bandwidth improvement and antenna size reduction in a single design is proposed. The well-known technique of effective substrate thickness increment is performed to improve the impedance bandwidth, whereas for size reduction the electrical length of the conducting patch has been increased. A compact probe-fed inverted U-shaped microstrip patch antenna with a W-shaped ground plane has been designed and the experimental results are presented.     

Quasi-optical VCOs

Quasi-optical grid voltage controlled oscillators (VCOs) are presented. These VCOs are the first demonstration of a quasi-optical system consisting of several periodic arrays loaded with solid-state devices. A quasi-optical VCO consists of an array of oscillators, a variable capacitance array, and a mirror. The mirror provides feedback for locked power-combining of a large number of MESFET oscillators that load a two-dimensional metal grid on a dielectric substrate. The frequency can be electrically tuned either with gate bias or with another array loaded with varactor diodes. When the varactor bias voltage is changed, the capacitance of the diodes changes, which in turn modulates the frequency of the output power-combined wave. Two types of arrays are presented, one consisting of short dipoles, and the other of bow-tie elements. As expected, the bow-tie VCO has better performance than the dipole VCO, due to its broadband impedance. A 10% tuning bandwidth with less than 2 dB power change was measured in the case of a bow-tie VCO     

Modified rectangular patches for self-oscillating active-antennaapplications

Two modifications to a rectangular-patch antenna, suitable for the integration of active devices, are presented. In the first modification, the impedance inverter was placed in the rectangular opening formed by removing the central part of the patch. This modification allows optimal matching of the active device by changing the position, width, and length of the impedance-line transformer. An oscillating antenna, using this modified patch and a Gunn diode, showed a high EIRP, higher spectral purity, and substantially lower cross-polarization levels, in comparison with the reference active antenna with an unmodified patch. Because of the higher overall Q, this modification is recommended for active-antenna applications with active devices that have a narrower negative-resistance bandwidth. In the second modification, an active device (Gunn diode) was integrated directly into a rectangular opening inside the patch, without the use of a line transformer. This reduced the overall Q of the antenna, thus allowing wide-band frequency tuning by changing the bias voltage. A clear spectrum, with no spurious components of the free-running oscillating antenna, was observed. Radiation patterns in the E and H planes were measured. Low levels of cross-polarization, as for the first modification, were obtained. Injection-locking properties were investigated throughout the tuning range. A relatively wide locking range, with a good locking gain, was achieved. Such a miniaturized wide-band VCO antenna is applicable for integration in injection-locked active arrays, and spatial power combiners