Transmission through a two-layer array of loaded slots

The mutual admittance method is used to calculate the transmission through a two layer array of slots. The slot arrays are thin and parallel. The plane wave illumination is at an arbitrary angle in either theE-plane orH-plane. The mutual admittance between two slot antennas, either in the same or different planes, is derived. In this derivation it is assumed that the slots are small enough so that when short-circuited at their terminals the electric field scattered from the slot is negligible. The evaluation of the mutual admittance sums is simplified by the extension to the slot case of certain impedance relationships established previously for a two-layer dipole array. For many applications the two-layer slot array is more desirable than a single-layer array since a wider passband and sharper skirts can be obtained with proper design. The analysis shows, however, that for high incidence angles the dip in the center of the passband may be deeper than for the similar two-layer dipole array.     

有限元\\边界元混合算法分析波导裂缝阵列天线

研究了一种分析波导裂缝阵列天线的方法。将有限元-边界元混合算法（FE-BI）应用于波导裂缝阵列天线的计算中,建立理论分析模型,计算波导裂缝上的等效磁流,进而求解整个天线阵列的远场辐射特性。为了检验这种方法的正确性,将所得的数值计算结果与测试值进行了比较,结果表明：FE-BI法可以作为计算波导裂缝阵列天线的一种有效的方法。     

Circularly polarised printed array antennas composed of strips and slots

This letter presents a new type of circularly polarised micro-strip antenna. It is composed of half-wavelength strip conductors and slots arranged along both sides of a microstrip line. Circular polarisation can easily be obtained with this antenna whether the current distribution on the line is a travelling wave or a standing wave. The experimental verification is also presented.     

MSW applications for phased array antennas

A potential application of MSW technology lies in the area of time delay for future low-sidelobe wide-bandwidth phased array antennas. High-precision MSW electronically tunable analog time-delay units in transmit/receive modules in phased arrays have the potential of greatly enhancing antenna system capabilities, by increasing instantaneous operating bandwidth and decreasing sidelobe levels, over phased array systems using only phase shifters or switched lines for beam steering and control. This paper provides a status report of MSW time delays for such arrays.     

星载Ku波段波导缝隙天线的缝隙特性分析

在星载Ku波段谐振式波导缝隙阵列天线设计中,由于结构空间的限制,采用半高非标准波导。考虑到半高波导中更容易产生高次模影响的特点,以及设计成本和效率问题,将基于有限元法的高频电磁仿真软件Ansoft HFSS与Fortran编程相结合应用于该类天线的设计。采用HFSS研究并描述了宽边纵向辐射缝隙和中心倾斜耦合缝隙的特性,结合Elliott提出的经典平面缝隙阵设计理论,用Fortran编程设计了阵元数为80(8×10)的波导缝隙阵列天线实验件,并用HFSS仿真优化了天线阵整体的性能。对实物天线进行了近场测试,结果表明:天线的E面和H面副瓣电平分别是-29 dB和-27.5 dB,1.3以下驻波带宽为340 MHz,与仿真结果基本吻合。良好的测试结果验证了用HFSS获取缝隙特性曲线的正确性及设计方法的有效性,为后期大型阵列设计提供了一种有效的方法。     

Radiation characteristics of array of crescent slots fed through radial waveguide

An array of annular slots fed through a radial waveguide does not produce axial radiation when excited through a simple coaxial line. One method of producing axial radiation is to make the excitation cos ? dependent. An alternative method of producing axial radiation is presented, where instead of changing the excitation the slot shape is changed, thereby keeping the excitation simple.     

A waveguide transverse slot for array applications

The characteristics of a radiating rectangular transverse slot in a rectangular waveguide have been studied. A moment method solution is used with entire basis expansion and testing functions (Galerkin) including the effect of wall thickness. The results are presented in terms of normalized resistance and reactance versus slot length and frequency. Excellent agreement with a previous pulse basis solution is found, as well as with measured data. An array of resonantly spaced transverse slots radiates large grating lobes. A spatial filter using baffles to suppress the grating lobes is described, suppressed. The effect of the baffles on the transverse slot impedance is analyzed for the case of baffles with infinite height     

A novel array antenna for MSAT applications

The issue of reducing the cost of phased array vehicle antennas through the use of a lens feeding arrangement instead of phase shifters at each element is addressed. In particular, the economic viability of a mobile satellite system (MSAT) is largely dependent on the efficient use of the allocated scarce spectrum and orbit as well as the satellite power. The type of vehicle antenna used will play a critical role in achieving this efficiency. A standard design approach for an electronically steered array uses phase shifters at each element to provide beam steering. A method for reducing the required number of phase shifters by using an R-KR lens feed network is outlined. The authors briefly discuss the phase shifter approach to beam steering, examine various lens feed techniques, and describe the R-KR lens approach. The lens feed network architecture is examined, a computer model for simulation of the array is presented, and the results of analysis of a suggested design for the MSAT application are given. In addition, satellite acquisition and tracking considerations are investigated     

A sectored phased array for DBF applications

In this paper, we present the idea of using switching techniques in phased arrays in order to reduce the size and cost of the RF/IF circuitry on a smart array system with a given number of array elements. The principle is illustrated using a sectored phased array antenna working on the 5.2 GHz industrial, scientific and medical (ISM) band. The antenna is a four-element dipole array, with two active and two parasitic elements. The array uses a reflective 2P4T switch to route the RF signals to consecutive elements of the array and four pin diode SPST switches for short or open circuiting the antenna elements. The performance of the proposed antenna system surpasses the performance of traditional two-port phased array systems and is comparable to that of four-element planar arrays. Simulated results of the antenna performance and beam-forming capabilities are presented.     

Phase conjugator for active retrodirective array applications

A novel phase conjugator for active retrodirective array applications is presented. The circuit provides conversion gain as well as phase conjugating operation by using active devices, and results in a simple and compact design through the use of a common port for RF and IF signals. Measurement results indicate a 3.2 dB conversion gain with an RF-IF isolation of 20 dB. This phase conjugator can be used as a component in a retrodirective array when combined with an antenna     

Dual-polarized array for signal-processing applications in wirelesscommunications

A novel dual-polarized antenna array designed for a spatial division multiple access (SDMA) system working in the 1850-1990-MHz band is designed and built. The antenna is designed to have similar element patterns, and measurements of S-parameters and radiation patterns are presented. The array signal processing performance of the array using all elements and with no compensation for mutual coupling or differences in element patterns is studied through direction-of-arrival (DOA) estimation using total least squares estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT). The results show that the accuracy of the DOA estimates is quite acceptable for wireless communication applications     

Laminated waveguide as radiating element for array applications

This paper reports on the study of a new antenna as well as a five-element array prototype developed for communications in K-band and suitable for low temperature co-fired ceramic technology. The radiating element is an open waveguide realized in laminated technology. A special coaxial-to-waveguide transition has also been designed as feed port for measuring the prototypes. The element exhibits a 1 GHz bandwidth centered at 20.7 GHz and a 2.7 dBi gain. In an array configuration, mutual coupling between the elements is lower than -18 dB across the bandwidth. The simulated boresight radiation pattern of a five-element array is stable over the bandwidth and the gain reaches 9.2 dBi at 20.7 GHz. The measurements of the radiation pattern for a 20-degree scan angle, as well as the simulation, demonstrate the scanning capability of this array.     

Ball grid array reliability assessment for aerospace applications

Reliability of ball grid arrays (BGAs) was evaluated with special emphasis on space applications. This work was performed as part of a consortium led by the Jet Propulsion Laboratory (JPL) to help build the infrastructure necessary for implementing this technology. Nearly 200 test vehicles, each with four package types, were assembled and tested using an experiment design. The most critical variables incorporated in this experiment were package type, board material, surface finish, solder volume, and environmental condition. The packages used for this experiment were commercially available packages with over 250 I/Os including both plastic and ceramic BGA packages.The test vehicles were subjected to thermal and dynamic environments representative of aerospace applications. Two different thermal cycling conditions were used, the JPL cycle ranged from −30°C to 100°C and the Boeing cycle ranged from −55°C to 125°C. The test vehicles were monitored continuously to detect electrical failure and their failure mechanisms were characterized. They were removed periodically for optical inspection, scanning electron microscopy (SEM) evaluation, and cross-sectioning for crack propagation mapping. Data collected from both facilities were analyzed and fitted to distributions using the Weibull distribution and Coffin–Manson relationships for failure projection. This paper will describe experiment results as well as those analyses.     

Adaptive array sensor processing applications for mobile telephonecommunications

The mobile telephone cellular communication system is rapidly being saturated with an increase in subscribers. Although advanced coding and modulation techniques as well as different cell cluster architectures have been implemented, a great increase in the channel capacity is needed, especially in large markets. Adaptive sensor processing has been introduced as a possible remedy to increase the channel capacity by using the directional sensitivity, which leads to a reduction of the interference. Some high-resolution algorithms are evaluated for the direction of arrival (DOA) estimation for a cellular mobile radio environment whose cluster size is varied from K=7, K=4, and K=3; more signals and scattering scenarios that typically arise in urban areas are taken into account. This information is used to beamform toward the signal of interest, resulting in a decrease of the interference. Several signal estimation procedures are evaluated and compared, and it is observed that the DOAs, among other benefits, leads to even higher performance compared with the reference signal method. The computational aspects for the different signal processing, detection and estimation schemes are also discussed     

Wideband single layer microstrip antenna for array applications

A wideband single layer microstrip antenna, fed by two different networks, is presented. A bandwidth of ~15% for SWR<2 is obtained. As its dimensions are the same as those of a conventional 2×2 sub-array, this radiating element can be used in array configuration     

Dual-band dual-polarised microstrip antenna array for SAR applications

A novel dual-band dual-polarised microstrip antenna array for synthetic aperture radar applications with a dual-frequency ratio of about 1:3 is presented. Microstrip dipoles and square patches are used as the radiating elements at S- and X-bands, respectively. The measured bandwidth of VSWR<2 reaches 8.9% and 17% for S- and X-bands, respectively. The measured cross-polarisation levels are <-26 dB for the S-band and <-31 dB for the X-band     

Simplified RF receive frontend architecture for active array applications

A new concept for receive front end circuits is presented, which proposes the use of the low noise amplifier (LNA) in a second role as an amplifier of the local oscillator (LO) signal. Based on this concept, much of the complexity of the active array signal distribution networks (calibration and LO) can be reduced. It is shown that the danger of saturation, intermodulation and noise degradation can be overcome by using an unbalanced active mixer circuit which requires an LO-power level compatible with the limitations of modern LNAs.     

An extremely lightweight fuselage-integrated phased array for airborne applications

A design of a lightweight low volume electronically scanned antenna is described. This antenna, besides being the radiating aperture, serves as a load-sharing fuselage panel in a small weight-sensitive remotely piloted vehicle (RPV). A demonstration array incorporating the microstrip radiating elements, stripline feed circuit, and microstrip-line p-i-n diode phase shifters was assembled to evaluate the electrical characteristics and scanning capabilities of the array. The demonstration array was tested on the antenna range and operated successfully as part of a radar/communication subsystem demonstration. An eight-element lightweight section of the demonstration array was subsequently designed and fabricated in a modern production facility utilizing numerically controlled machines and state-of-the-art printed circuit board etching and plating equipment. Successful operation of this lightweight section sufficiently demonstrated that a lightweight and low volume electronically steerable phase-array antenna can be fabricated and integrated into a structural panel in production quantities.     

Microstructure fibre array for RF photonic signal processing applications

A novel microstructure fibre array (MFA), comprising multiple singlemode fibre waveguides reduced to an overall diameter of approximately 30 /spl mu/m is reported. When used in conjunction with a single photodetector, the array facilitates the efficient and stable electrical summation of a number of RF-modulated optical signals with minimal optical interference effects. The reported MFA has optical insertion loss less than 0.1 dB. An RF filter based on the array exhibits less than 0.4 dB optical insertion loss and excellent temporal stability.     

3.6-GHz eight-antenna MIMO array for mobile terminal applications

This paper studies an eight-antenna multiple input and multiple output (MIMO) array owning a wide bandwidth to cover the 3.6-GHz (3400–3800 MHz) band for modern mobile terminal applications. The developed eight-antenna array consists of two four-antenna sub-arrays having slight different physical dimensions. The antenna elements are all based on the stepped impedance resonator (SIR) structure, which are positioned along the two long borderlines of the ground plane in the mobile terminal. A wider bandwidth can be realized by properly choosing the electrical length ratio and impedance ratio of the SIR structure, and the system performance can be consequently improved. The measured results of the fabricated prototype show that the value of the return loss is larger than 10 dB and the value of the inter-element isolation is more than 11.7 dB within the entire 3.6-GHz band. Furthermore, the envelop correlation coefficient (ECC) between arbitrary two antenna elements is smaller than 0.1 for the developed eight-antenna MIMO array. Design details of the MIMO array as well as the simulated and experimental results will be given and discussed.