Conformal microstrip antennas and microstrip phased arrays

A new class of antennas using microstrips to form the feed networks and radiators is presented in this communication. These antennas have four distinct advantages: 1) cost, 2) performance, 3) ease of installation, and 4) the low profile conformal design. The application of these antennas is limited to small bandwidths. Phased arrays using these techniques are also discussed.     

Circular-waveguide-fed microstrip patch antennas

A microstrip patch antenna fed by a circular waveguide is presented. The microstrip patch built on a foam substrate is laid on the flange of the circular waveguide's open mouth. The waveguide feeds the patch by coupling energy to the patch through a narrow slot underneath the patch. Two operating frequency bands were observed and the characteristics of the antenna were measured.     

Rigorous analysis of microstrip phased array antennas using a new FDTD method

A finite-difference time-domain (FDTD) algorithm for radiating antennas that involve multiple, phased excitation sources is presented. The algorithm has the potential to analyse phased array antennas in the time domain. The authors apply it to a two-element microstrip antenna (MSA) phased array on a finite substrate, and compare the results as gained with an existing method and experiments.<>     

A modular approach for the design of microstrip array antennas

A method for the design of medium gain (15-25 dB) microstrip array antennas is described. A modular approach is utilized in which a given antenna is used as a building block for higher gain antennas. A series ofX-band antennas were built in this way, and the results seem to validate the usefulness of the method.     

Polarization reconfigurable microstrip phased array

In this paper, the design and the experimental validation of a polarization reconfigurable microstrip phased array is presented. The reconfigurability between the right-handed (RHCP) and left-handed (LHCP) circular polarization is achieved using electronic switches (PIN diodes) combined with truncated corners microstrip radiators. In the design, special attention was given to the matter of reducing back lobe radiation effects using the concept of asymmetric positioning of the radiators with respect to the ground plane. Afterward, the main lobe axial ratio behavior for several beam steering and side lobe level conditions are investigated. Finally, the polarization reconfigurability is achieved and the design is validated through the good agreement between theoretical and experimental results.     

Cross polarization of microstrip patch antennas

The cross-polarization level of circular and rectangular patches is evaluated by finding the peak value angles. The peak value is strongly dependent on substrate dielectric constant, varying roughly as1/epsilon. Aspect ratio of a rectangular patch has little effect on peak values or location. Patch thickness also has little effect; results are limited to thin patches as surface waves are not included.     

Optically fed aperture-coupled microstrip patch antennas

Several techniques are presented for feeding microstrip antennas with RF-modulated lightwave signals via an optical fiber. Lightwave-to-RF conversion is performed in a module containing a photodiode, RF circuitry, and a microstrip antenna element. Three different transmitting configurations at microwave frequencies were designed and tested: passive matching, matching with amplification, and an injection-locked oscillator. In each case, the only connections to the antenna modules were an optical fiber and DC bias lines     

Broadband microstrip patch antennas for MMICs

A broadband microstrip patch antenna well suited for monolithic microwave integrated circuits (MMICs) is presented. The antenna exhibits a measured bandwidth of 35%, low surface wave loss, a high front-to-back ratio, and is fabricated directly on the MMIC substrate material. The predicted and measured input impedances are given along with the measured radiation performance     

Mutual coupling between microstrip patch antennas

A theoretical approach to the mutual coupling phenomenon between microstrip patch antennas of arbitrary geometry and alignment is presented. The theory employs an equivalent magnetic wall model for each single radiator, a series expansion in resonant modes in connection with a reaction concept treatment of antenna interaction. Good agreement of theoretical and experimental data is observed in a wide frequency range for various element spacings.     

FDTD analysis of phased array antennas

This work presents a new application of the finite-difference time-domain (FDTD) method to the generalized analysis of phased array antennas. The generality of the FDTD method brings important advantages to the phased array antenna analysis problem, allowing the modeling of complex conductor and dielectric geometries with relative ease. Additionally, a new broad-band FDTD periodic boundary condition is developed which allows the array problem to be simplified to a periodic unit cell computational domain. This hybrid frequency/time-domain periodic boundary condition enables solution of the periodic phased array problem for arbitrary scan conditions in a broadband fashion. The new method is applied to waveguide and stacked microstrip antenna arrays and the numerical results are compared to experimental or analytic solutions, demonstrating the validity and utility of this method     

Dual-beam array of microstrip leaky-wave antennas

The authors present a small series-fed array of microstrip leaky wave antennas (LWAs) operating at 6.85 GHz and showing a narrow dual-beam pattern (17°×22°). The excitation is provided by a slotted coplanar waveguide. This type of antenna could be used as a radar sensor in Janus systems for contactless measurements of velocity and distance     

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.     

Design of wide-band aperture-stacked patch microstrip antennas

A variation of the aperture-coupled stacked patch microstrip antenna is presented, which greatly enhances its bandwidth. Bandwidths of up to one octave have been achieved. The impedance behavior of this antenna is compared with that of other wide-band microstrip radiators. Matching techniques for the antenna are presented and their relative merits discussed. The effects of varying several key physical parameters of the antenna are investigated, lending some insight into its wide-band operation. Variations on the design such as incorporation of additional patches are also discussed     

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     

Coplanar waveguide feed for microstrip patch antennas

A coplanar waveguide (CPW) loop is shown to be an effective low VSWR feed for microstrip antennas. The low VSWR transition between the CPW and the antenna is obtained without the use of a matching circuit, and it is relatively insensitive to the position of the antenna and the feed.<>     

Custom modes for microstrip phased array analysis

Custom modes for the patch current in an infinite microstrip phased array are derived. Compared to the set of subdomain basis functions normally used for arbitrarily shaped patches these `Fourier modes' reduce the number of unknowns by one to two orders of magnitude. This should make them particularly useful for the analysis of finite arrays     

Bandwidth enhancement of microstrip patch antennas using coupledlines

A novel single-layer rectangular patch antenna using a coupled line feed is described. This coupled line matching technique increases the bandwidth of the patch antenna by a factor of more than 2.5 as compared to the normal edge-fed patch with the same geometrical dimension     

Multiport network approach for modeling the mutual coupling effectsin microstrip patch antennas and arrays

A method is described for representing the mutual coupling between edges of a microstrip patch (or the edges of two different patches in an array) in form of a mutual admittance matrix. Coefficients of the mutual admittance matrix are evaluated by modelling the edge fields by equivalent magnetic current line sources. The formulation is an extension of the multiport network modeling of microstrip patches and the segmentation method of analysis. Results are found to be in good agreement with the measured data on mutual coupling available in the literature. Relative contributions of various edges of rectangular patches to the mutual coupling are discussed     

Finite phased arrays of rectangular microstrip patches

Finite phased arrays of rectangular microstrip patch antennas are analyzed. Reflection coefficient magnitudes, element patterns and efficiency (based on power lost to surface waves) are calculated for various sized arrays on substrates of practical interest and are compared with previous infinite array solutions. Measured element patterns and mutual coupling data for a small array are presented and compared with calculations.