Characteristics of a circular patch microstrip antenna on uniaxially anisotropic substrate

Resonant characteristics of a circular patch microstrip antenna on the uniaxially anisotropic substrate are determined via spectral domain analysis. Green's functions of the structure in Hankel transform domain are determined by using Hertz vector formulation. The variations in the resonant characteristics depending on the replacement of the isotropic substrate with the uniaxially anisotropic one are analyzed for different permittivity tensor element cases. The results of the study indicate that resonant frequency and bandwidth characteristics of the antenna can be considerably changed due to proper selection of substrate anisotropy ratio and other structural parameters. Depending on the arrived results, operational performance of the antenna will be improved in future studies.     

Input impedance of a probe-fed circular microstrip antenna with thick substrate

A method of computing the input impedance for the probe fed circular microstrip antenna with thick dielectric substrate is presented. Utilizing the framework of the cavity model, the fields under the microstrip patch are expanded in a set of modes satisfying the boundary conditions on the eccentrically located probe, as well as on the cavity magnetic wall. A mode-matching technique is used to solve for the electric field at the junction between the cavity and the coaxial feed cable. The reflection coefficient of the transverse electromagnetic (TEM) mode incident in the coaxial cable is determined, from which the input impedance of the antenna is computed. Measured data are presented to verify the theoretical calculations. Results of the computation of various losses for the circular printed antenna as a function of substrate thickness are also included.     

Analysis of a circular microstrip disk antenna with a thick dielectric substrate

The problem of a circular microstrip disk excited by a probe is solved using rigorous analysis. The disk is assumed to have zero thickness, and the current on the probe is taken to be uniform. Using vector Hankel transforms the problem is formulated in terms of vector dual-integral equations, from which the unknown current can be solved for. Due to the singular nature of the current distribution arising from probe excitation, the direct application of Galerkin's basis function expansion method gives a slowly convergent result. Therefore the singular part of the current is removed since the singularity is known a priori. The unknown current to be solved for is then regular and tenable to Galerkin's method of analysis. It is shown that this analysis agrees with the single-mode approximation when the dielectric substrate layer is thin, and that it deviates from the single-mode approximation when the substrate layer is thick. Excellent agreement of both the computed real and imaginary parts of the input impedance with experimental data is noted. The radiation patterns and the current distributions on the disk are also-presented.     

Tunable circular patch antennas

A method to control the resonant or operating frequencies of circular patch antennas has been investigated experimentally and theoretically. It consists of the placement of passive metallic or tuning posts at approximate locations within the input region of the antenna. Comparison of measured and analytical results seems to establish the validity of a theoretical model proposed to determine the input performance of such circular patch antennas.     

Aperture-coupled patch antenna on UC-PBG substrate

The recently developed uniplanar compact photonic bandgap (UC-PBG) substrate is successfully used to reduce surface-wave losses for an aperture-coupled fed patch antenna on a thick high dielectric-constant substrate. The surface-wave dispersion diagram of the UC-PBG substrate has been numerically computed for two different substrate thickness (25 and 50 mil) and found to have a complete stopband in the frequency range of 10.9-13.5 and 11.4-12.8 GHz, respectively. The thicker substrate is then used to enhance broadside gain of a patch antenna working in the stopband at 12 GHz. Computed results and measured data show that, due to effective surface-wave suppression, the antenna mounted on the UC-PBG substrate has over 3-dB higher gain in the broadside direction than the same antenna etched on a grounded dielectric slab with same thickness and dielectric constant. Cross-polarization level remains 13 dB down the co-polar component level for both E- and H-planes     

Green's function calculations on circular microstrip patch antennas

Green's function calculations have been applied to solve the radiation problem of circular microstrip patch antennas. The patch is fed by either a microstrip line or a coax line to be approximated as delta-function-like sources. The resultant Galerkin elements involve only one-fold Sommerfeld-type integrals. The resonant frequency, impedance, and far-field pattern have thus been calculated, which compared nicely with measurements     

Radiation modes in circular patch antennas

We have formulated exact solutions of the normal modes in the microstrip patch antenna possessing circular geometry. The theory makes use of a new Green's function in conjunction with current potential analysis. The calculations demonstrate that the magnetic wall confinement boundary conditions as formulated in past theories hold approximately true if the surface wave loss is minimal compared to other losses: dielectric loss, conductor loss, and radiation loss. For practical path antennas the normal modes are not confined locally near the microstrip patch. Rather, they are composed of propagation surface waves which extend far beyond the region containing the patch antenna. We term these normal modes as leaky modes, since they resemble the leaky modes found in dielectric image guides. Measurements by us of the radiation mode frequencies and the intrinsic Q-values of the microstrip patch antennas compared very well with theory     

CPW-fed slot-loop coupled patch antenna on narrow substrate

A coplanar waveguide (CPW) fed rectangular patch antenna excited by a rectangular slot-loop is designed for use in the 2.4 GHz ISM band. The size of the slot-loop is chosen to be as close to that of the patch as possible, and the substrate is cut to be as narrow as possible. Experimental results show that this antenna has a nearly omnidirectional pattern in the H-plane and a bandwidth of ~22% for VSWR<2     

Single feed wideband circular polarised patch antenna

Based on the air gap and stacked patch configuration, a new wideband circular polarised patch antenna is proposed. Significantly increased impedance and axial ratio bandwidths can be achieved without increasing implementation complexity compared with that of existing patch antennas.     

Phased array simulation using circular patch radiators

The circuit properties of a circular patch with center short-circuit pin is investigated in a rectangular grid array. It is found that feed probe direct radiation produces large variations in element-to-element coupling coefficients in theE-plane. For the investigated pairwise arrangement of feed probe positions the additional effect is unsymmetricE-plane coupling with respect to the direction toward the coupled element; this leads to unsymmetricE-plane scanning-induced impedance variation. The principal method of investigation is the small-array method using an8 times 8element array, but two waveguide simulators are used to check the results. It is concluded that the small array calculation provides reliable results for scanning angles greater than60degoff broadside. Active element match is observed to vary from -8.5 dB at broadside to about -20 dB on a60degscanning cone. Finally, a direct measurement of the dissipation losses of the patch radiator is presented using a waveguide simulator as a two-port network. At 5.5 GHz a - 0.3 dB dissipation loss is found.     

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     

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     

Corrugated circular microstrip patch antennas for miniaturisation

New concepts for a corrugated circular microstrip patch antenna (CCMPA), which is moving in the radial direction and works at a frequency of 1.575 GHz (GPS), using linear and circular polarisation for miniaturisation are designed and fabricated. The linearly-polarised antenna has a reduction of 8.08% in patch diameter, a reduction of 21.12% in area and an increase of 1% in bandwidth compared with a circular microstrip patch antenna (CMPA). The radiation patterns of E-and H-plane for a corrugated-type antenna follow the general CMPA and the gain of the linearly-polarised antenna is 6.8 dBd. Also, the circularly-polarised antenna has a gain of 2.8 dBd and an axial ratio of 1.3 dBd at 1.575 GHz     

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     

A modified microstrip circular patch resonator filter

Circular holes are etched off a microstrip disk resonator. This results in a size reduction of 30%. By offsetting the positions of some of these holes, a degenerate orthogonal mode is excited, resulting in a split-mode bandpass filter. This filter can be considered as a lattice-type structure. A filter with a bandwidth of 8% centered at 2.0 GHz was designed. The measured insertion loss is 0.6 dB     

超厚铝基板焊接工艺研究

超厚铝基板是一种特殊印制板,其具有良好的稳定性和导热性,逐渐被应用于军用设备和高科技民品领域。而其良好的导热性给焊接带来了困难,手工焊接在国军标规定的烙铁温度280~320℃限制下,已无法完成焊接。这采用一种新型的加热方式,补偿铝基板在焊接过程中的热损失,通过工艺试验寻找最佳的工艺参数,解决铝基板难以焊接的问题。     

Space-wave efficiency of electrically thick circular microstrip antennas

A new very simple expression is presented for the space-wave efficiency of electrically thick circular microstrip antennas. It is derived from numerical results available in the literature, and is valid for the complete range of relative dielectric constants and the thicknesses of substrates which are normally used. It also provides insight into the fundamental influence of the substrate parameters on the space-wave efficiency of the circular microstrip antennas. The results obtained by using this expression are in conformity with those reported elsewhere.     

厚PTFE陶瓷基板钻孔参数的优化探讨

厚PTFE陶瓷基板是陶瓷粉填充的高频材料,其材料内含有大量陶瓷粉,且有聚四氟乙烯（PTFE）树脂,在钻孔参数设置不当时极易产生孔口披峰、崩孔或铜瘤等问题。结合厚PTFE陶瓷基板板材的特性,从钻孔参数上进行优化试验,以解决此类厚PTFE陶瓷材料的钻孔加工过程中出现的披峰、铜瘤问题。     

Simple modeling of coplanar waveguide on thick dielectric overlossy substrate

We present a simple semi-empirical high-frequency equivalent circuit model to characterize the coplanar waveguide structure, which consists of a relatively thick metal line on very thick polyimide over a lossy substrate such as a Si BiCMOS wafer. Considering the geometric dependence of the conductive loss and the skin effect of the substrate loss, we derive modified models for the equivalent circuit elements. We verify the validity of our model by comparing it with experimental measurements. Our model is simple enough not only to be suitable for efficient circuit simulation but also to be useful for process characterization and design     

Spectral-domain analysis of circular patch frequency selective surfaces

A computationally efficient method is presented for analyzing the scattering from frequency selective surfaces (FSS) comprised of circular metal patches. The formulation is carried out in the spectral domain where the convolution form of the integral equation for the induced current reduces to an algebraic one and the spectral-Galerkin technique is used to solve the resulting equation. Entire-domain basis functions that satisfy the edge condition are introduced to expand the unknown induced current on the metal patches. Calculated results using this procedure show good agreement with data reported by other authors.