Design of probe-fed stacked patches

In this paper, a design strategy to achieve bandwidths in excess of 25% for probe-fed stacked patches is presented. The choice of appropriate dielectric materials for such bandwidths is given and the role of each antenna parameter in controlling the impedance behavior is provided. It has been found that the selection of the substrate below the lower patch plays a major role in producing broad-band responses. A simple design procedure is outlined and this technique is verified experimentally. The findings presented here can be applied to all types of probe-fed stacked patches as well as edge-fed and cavity-backed configurations     

Phased arrays of probe-fed stacked microstrip patches

This paper presents calculated and measured results for infinite phased arrays of probe-fed stacked rectangular and circular microstrip patches. A numerical model is described that is based on a rigorous Green's function/Galerkin solution. In this solution, the connection of one or more vertical probe feeds to each patch is accurately modeled using a special attachment mode basis function, which is derived from the corresponding cavity model solution. Numerical results for both linearly and circularly polarized arrays are obtained. Measured results from a waveguide simulator are also presented and used to validate the numerical model     

Search for high-performance probe-fed stacked patches using optimization

High-performance circular probe-fed stacked patch antenna designs are explored through the use of numerical optimization. New trends are sought to aid understanding and to suggest novel solutions. We describe the optimization technique, present a new design trend relating efficiency and bandwidth to the choice of substrate dielectric, and propose and demonstrate a novel, optimized antenna achieving 33% bandwidth whilst maintaining greater than 80% surface wave efficiency.     

Analysis of stacked microstrip patches with a mixed potentialintegral equation

A method based on the mixed potential integral equation for the analysis of flat microstrip antennas in a double-layer substrate is presented. The method is used to compute the input impedance of a stacked patch configuration. This structure permits a larger bandwidth and may also provide dual-frequency operation. The Green's functions are discussed in detail, and numerical results are obtained for the propagation constant of the dominant surface wave. Theoretical and experimental results are compared for a dual-frequency and a broadband stacked patch antenna. Theoretical results for the input impedance are in good agreement with measurements. The difference between theoretical and experimental results for the resonant frequency is less than 4.5% in all cases     

Transformer coupled stacked FET power amplifiers

The development of high-power linear ultrahigh-frequency amplifiers is made difficult by the low impedance of the devices used in the output stage, which causes matching difficulties and high radio-frequency current levels. A stacked field-effect transistor (FET) configuration is shown to reduce these problems with its increased output impedance and lower current required for a given output power. A linear analysis of the stacked FET configuration is given. Two class A monolithic microwave integrated circuit amplifiers are developed and subjected to one- and two-tone tests to demonstrate the performance of the stacked FET as a power amplifier at 900 MHz     

Electrical loop antenna using stacked patches for 433.92 MHz RFID reader

A novel and compact electrical loop antenna for an RFID reader at 433.92 MHz is proposed. Using modified and stacked patches, in-phase and uniform currents are excited so that an omnidirectional radiation pattern with a /spl phi/-component of the electric field is obtained. The antenna is analysed based on simulated and measured results.     

Wideband aperture coupled stacked patch antenna using thicksubstrates

An aperture coupled stacked patch microstrip antenna is presented which is capable of operating over a bandwidth in excess of 50%. Measured and predicted impedance behaviour and gain over the band are given. Other important factors such as surface wave efficiency and back radiation levels are presented     

Broadband stacked annular ring coupled shorted circular microstripantenna

A novel microstrip antenna consisting of a stacked annular ring coupled to a shorted circular patch is presented. This new geometry offers a large impedance bandwidth, a higher gain and lower cross-polarisation levels in the H- and E-planes. Experimental results are compared with theoretical values     

Analysis of electromagnetically coupled two-layer elliptical microstrip stacked antennas

Theoretical analysis of a coaxially fed, electromagnetically coupled two-layer elliptical microstrip stacked antenna based on circuit theory is presented in which mutual coupling is considered. Consequently, various parameters such as input impedance, VSWR, return loss, bandwidth etc. are investigated as a function of frequency, which shows resonance at 3.0GHz. It is also observed that there exists a critical value of frequency (3.0GHz) below which capacitive coupling is dominant and above which inductive coupling is dominant. The electromagnetic coupling enhances the radiated power which depends directly on the permittivity of the substrate, in spite of the fact that radiated power generally decreases with increasing permittivity of the substrate.     

A broadband aperture-coupled stacked microstrip antenna with both patches notched and offset

This paper proposes a new approach to further improving the bandwidth of a typical aperture-coupled stacked microstrip antenna by cutting triangular notches in the radiating sides of both radiating patches together with offsetting both patches. An antenna applying this new approach is designed, fabricated, and tested. The experimental antenna could achieve a measured impedance bandwidth of about 37.5% for the Voltage Standing Wave Ratio （VSWR） 〈 2 in X-band.     

Investigation of photoresist-specific optical proximity effect

Optical proximity effects arising from individual resist characteristics are investigated. The parameters studied are those used in photoresist exposure and development simulation using the SOLID and Prolith/2 programs. The optical proximity effect is found to be independent of the exposure parameters but greatly affected by the development process and is shown to be a function of the Mack parameter, n, which is related to the resist contrast, γ. Finally, in order to put this effect into perspective with other resist selection criteria, the development parameter, n, is also shown to be related to wall angle and depth-of-focus (DOF).

The results of this investigation will therefore enable the user to select the most appropriate photoresist for a specific application.     

Investigation of increased performance of close series stacked tube axial fans due to inclusion of diffuser element

The increased performance of close series stacked tube axial fans due to the introduction of a diffuser element between the primary and secondary fan is investigated in this paper. Experimental results showed that there was a 15% increase on average in the performance of two stacked Delta AFB0412VHN 40 mm fans across their operating range when a diffuser element was introduced between the two fans. It was also observed that the performance approximately increased by an additional 4% when the space between the diffuser and primary fan was increased from 0.3D_h to 0.5D_h. Numerical simulation of the flow between the primary and secondary fans was used to probe the cause of the increased performance. The area-averaged secondary kinetic energy (SKE) was used in the presented study as an indicator of the swirl decay. The numerical results showed that the introduction of a diffuser element reduced the SKE/SKE_inlet ratio dramatically. It was also found that the SKE/SKE_inlet ratio was further decreased when the distance between the diffuser and primary fan was increased to 0.5D_h, which is consistent with the experimental observation.     

Microstrip antenna array with series-fed `through-element? coupled patches

A new microstrip antenna array with series-fed patches is proposed. To reduce the length of feeding lines the `through-element' feeding technique has been developed. A microstrip patch in which the input feeding line is directly connected and the output line is coupled to a patch is investigated. By adjusting the length of the coupling region an appropriate coupling level is achieved. A 4times1 antenna array operating within the 24 GHz frequency band for radar sensor applications is designed using the proposed feeding technique     

Flat lens antenna concept using aperture coupled microstrip patches

A planar lens antenna based on aperture coupled microstrip patch elements with stripline delay lines is described. Features of this design are discussed, and results for transmission coefficient magnitude against frequency are presented. The background for the development of this lens configuration is discussed in terms of a natural progression from frequency selective surfaces, and the inadequacies of simpler geometries are explained     

A novel high performance stacked LDD RF LDMOSFET

A novel silicon RF lateral double-diffused metal oxide semiconductor field effect transistor (LDMOSFET) structure, using a simple yet effective concept of stacked lightly doped drain (LDD), is proposed. The stacked layers of LDD minimizes the on-state resistance of the transistor due to the n+ doping used in the top LDD layer, and also raises the device breakdown voltage due to the charge compensation in the composite LDD region. Therefore, for the same blocking voltage rating, the stacked LDD structure allows the LDMOSFET to have a higher current handling capability. This in turn causes the transconductance Gm to be higher, leading to higher RF performance for the power device. Measured results show that a 67% improvement in I_dsat and a 16% improvement in forward blocking voltage are obtained. Furthermore, the new device achieves an increase in transconductance of 145% and improves cut-off frequency by 108% at a gate voltage of 10 V     

Analysis of the impact of proximity correction algorithms oncircuit performance

Variation in channel length degrades circuit reliability and yield. A common way to compensate for this problem is to increase the mean channel length, which, unfortunately, degrades circuit performance for digital circuits. One source of channel length variation is lithography, during which the line width is influenced by local layout patterns. It is possible to compensate for this effect by resizing transistor gates appropriately on the mask. However, the effectiveness of the correction is limited by constraints such as the mask correction resolution. To determine how to design a good correction scheme with limited resources, we have developed a method to compare different correction algorithms in terms of their impact on the performance of one of the main functional blocks in a state-of-the-art microprocessor. In particular, to evaluate correction algorithms while avoiding the high cost associated with generating multiple mask sets and fabricating product wafers with each of these mask sets, we present a method for predicting the correction results using simulation. Our methodology involves a DRC-based approach for gate resizing, along with critical path simulation for evaluating circuit performance. In-line CD measurement data were used to measure the impact of the proximity effect on transistor channel length. Electrical test results were used to calibrate the device models for circuit simulation     

Single feed proximity coupled circularly polarized microstripmonofilar Archimedean spiral antenna array

The analysis is presented for a microstrip feed proximity coupled monofilar Archimedean spiral four-element antenna array. Interactions between the microstrip corporate feed and the radiating elements are rigorously included. Results demonstrate that circular polarization can be achieved with proper spiral arm length. Polarization of either sense is controlled by the location of the feedline. The 3-dB axial ratio (AR) and voltage standing wave ratio (VSWR) bandwidths are 9%. The antenna is small (2R/λ₀=0.33) and the interelement spacing is 0.51λ₀. The microstrip feed produces a completely planar antenna system, which is compatible with microwave integrated circuits (MIC) and monolithic microwave integrated circuits (MMIC)     

Investigation of temperature variations on analog/RF and linearity performance of stacked gate GEWE-SiNW MOSFET for improved device reliability

In this paper, reliability issues of Stacked Gate (SG)-Gate Electrode Workfunction Engineered (GEWE)-Silicon Nanowire (SiNW) MOSFET is examined over a wide range of ambient temperatures (200–600 K) and results so obtained are simultaneously compared with conventional SiNW and GEWE-SiNW MOSFET using 3D-technology computer aided design quantum simulation. The results indicate that two temperature compensation points (TCP) are obtained: one for drain current (I_ds) and other for cut-off frequency (f_T) where device Figure Of Merits (FOMs) become independent of temperature, and it is found at 0.65 V in SG-GEWE-SiNW in comparison to other devices, hence will open opportunities for wide range of temperature applications. Furthermore, significant improvement in Analog/RF performance of SG-GWEW-SiNW is observed in terms of I_on/I_off, Subthreshold Swing (SS), device efficiency, f_T, noise conductance and noise figure as temperature reduces. It is also observed that at low temperature SG-GEWE-SiNW unveils highly stable linearity performance owing to reduced distortions. These results explain the improved reliability of SG-GEWE-SiNW at low temperatures over GEWE-SiNW MOSFET.     

Characteristics of aperture coupled microstrip antennas withvarious radiating patches and coupling apertures

A full wave moment method is applied to the analysis of aperture coupled microstrip antennas, in which all components of the electric and equivalent magnetic surface currents are considered. The electric current distributions on the rectangular patch for different coupling aperture positions are presented with their radiation patterns. The effects of the coupling aperture shape and size on the input impedance and radiation performance are also discussed. As an example of new radiators, slotted patches are studied, and it is shown that they can be used to achieve dual-frequency operation