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The radio frequency characteristics and design parameters for microstrip disk antenna elements and planar arrays are presented. Two C-band model arrays (an 8 element linear and an 8 by 8 planar) were designed, fabricated, and tested to demonstrate the technique of using microstrip elements for array applications. These arrays were designed with a cosine amplitude distribution.
The paper presents a combined numerical and empirical approach to the analysis of microstrip antennas over a wide range of frequencies. The method involves representing the antenna by a fine wire grid immersed in a dielectric medium and then using Richmond's reaction formulation (1974) to evaluate the piecewise sinusoidal currents on the grid segments. The calculated results are then modified to account for the finite dielectric discontinuity. The method is applied to round and square microstrip antennas.
The calculation of currents induced by a plane wave normally incident upon an infinite strip embedded in a grounded dielectric slab is used to infer the resonant width (or frequency) of rectangular microstrip antennas. By placing the strip inside the dielectric, the effect of a dielectric cover of the same material as the substrate can be included in the calculation of resonant frequency. A comparison with measured results indicated agreement of 1 percent or better for rectangular microstrip antennas constructed on Teflon-fiberglass substrate.
Microstrip construction compact for mobile applications. Circularly polarized microstrip antenna made of concentric cylindrical layers of conductive and dielectric materials. Coaxial cable feedlines connected to horizontal and vertical subelements from inside. Vertical subelement acts as ground for horizontal subelement.
Current and future microstrip antenna technology development for Spaceborne Synthetic Aperture Radars (SAR) are summarized. Some of the electrical and mechanical characteristics of previously and presently developed microstrip SAR antennas are shown. The SEASAT, the SIR-A and presently the SIR-B antennas are all designed for operation at L-band with approximately 22 MHz of bandwidth. The antennas have linear polarization with minimum of 20 dB of polarization purity. Both the SEASAT and SIR-A antennas were designed for a fixed pointing angle of 20.5 deg and 47 deg, respectively. However, the SIR-B has the added feature of mechanical beam steering in elevation (range). With the exception of different mechanical characteristics, it is concluded that present spaceborne SAR antennas have only single frequency and single polarization performance. The lack of large spaceborne antennas operating at the higher degree of fabrication tolerance required for a given performance; and larger feed and radiating element losses.
A number of impedance transitions and interconnections to a microstrip were designed and investigated. The double-step discontinuity on a microstrip was studied in detail, and a procedure was developed to design these structures. Their response was determined by making measurements in both the frequency and time domains in a consistent and repeatable manner. The time-domain presentation of the data was the most useful feature of the measuring system. All undesirable signal components were filtered out through the use of gating functions. Theoretically computed results were verified experimentally.
Problem of obtaining very-broadband frequency response resolved with buried-dielectric-microstrip matching network incorporated into infraredwaveguide structure. Waveguide modulator structure represents state-of-the-art of integrated optical devices: Has three-dimensional shape to accommodate three quarter-wavelength-transformers for microwave impendance matching at both input and output terminals. Microwave network, along with microstrip line designed with aid of computer, integrated with optical waveguide and used to tune line-selectable CO2 laser that provides total tuning range of 30 GHz in two sidebands.
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.
RHCP, Right-Handed, Circularly Polarized Microstrip Antenna program, aids in design of rectangular microstrip-antenna element, given desired frequency of operation and characteristics of substrate. Begins design calculations on basis of square element with linear polarization. Effective dielectric constant and changes in electrical length due to fringing at edges of radiating element taken into account. Coaxial feed inset with 50 ohms input impedance. Placement of feed such that two orthonormal modes produced in antenna cavity, right- or left-handed circular polarization obtained. Written in FORTRAN 77.
A conceptual design for a microstrip phased array with monolithic microwave integrated circuit (MMIC) amplitude and phase controls is described. The MMIC devices used are 20 GHz variable power amplifiers and variable phase shifters recently developed by NASA contractors for applications in future Ka band advanced satellite communication antenna systems. The proposed design concept is for a general NxN element array of rectangular lattice geometry. Subarray excitation is incorporated in the MMIC phased array design to reduce the complexity of the beam forming network and the number of MMIC components required. The proposed design concept takes into consideration the RF characteristics and actual phyical dimensions of the MMIC devices. Also, solutions to spatial constraints and interconnections associated with currently available packaging designs are discussed. Finally, the design of the microstrip radiating elements and their radiation characteristics are examined.
An L-band circularly polarized microstrip array antenna with relatively wide bandwidth has been developed. The array has seven subarrays which form a single cluster as part of a large overlapping cluster reflector feed array. Each of the seven subarrays consists of four uniquely arranged linearly polarized microstrip elements. A 7.5 percent impedance (VSWR less than 1.5) as well as axial ratio (less than 1 dB) bandwidths have been achieved by employing a relatively thick honeycomb substrate with special impedance matching feed probes.
The gain of a single microstrip patch and a two-layer parasitic array is measured using the image method under mismatched conditions. This method produces accurate results, even in the case of low-gain microstrip antennas. The advantages of this method over the gain comparison technique are discussed.
An experimental study of gain enhancement in microstrip antennas using identical parasitic patch directors is reported. The results indicate that, with two overlying parasitic directors, the gain of a rectangular microstrip antenna is enhanced from 4.7 dB to 10.6 dB, while the 3 dB beamwidth is reduced from 103 deg to 30 deg for the E-plane and from 70 deg to 35 deg for the H-plane. The three-layer electromagnetically coupled patch antenna exhibits similar antenna characteristics to those of the Yagi array, with over 120 dB gain and with about 1 percent bandwidth.
In this report, a thorough analytical procedure is developed for evaluating the frequency-dependent loss characteristics and effective permittivity of microstrip lines. The technique is based on the measured reflection coefficient of microstrip resonator pairs. Experimental data, including quality factor Q, effective relative permittivity, and fringing for 50-omega lines on gallium arsenide (GaAs) from 26.5 to 40.0 GHz are presented. The effects of an imperfect open circuit, coupling losses, and loading of the resonant frequency are considered. A cosine-tapered ridge-guide text fixture is described. It was found to be well suited to the device characterization.
Developmental class of antennas based on combination of microstrip-patch and Yagi-array concepts. Mutual coupling between microstrip elements, ordinarily considered nuisance, used to advantage. Applicable to both linearly and circularly polarized antennas. Use of fewer driven elements results in less complexity and reduced loss of power in associated transmission lines and other coupling and power-distributing circuitry. Applications include antennas on land vehicles, television receiving antennas, and conformal antennas on aircraft.
The dyadic Green's function for a current embedded in a grounded dielectric slab is used to analyze microstrip lines at millimeter wave frequencies. The dyadic Green's function accounts accurately for fringing fields and dielectric cover over the microstrip line. Using Rumsey's reaction concept, an expression for the characteristic impedance is obtained. The numerical results are compared with other reported results.
The high T sub c superconducting microstrip line and coplanar waveguide are compared in terms of the loss characteristics and the design aspects. The quality factor Q values for each structure are compared in respect to the same characteristic impedance with the comparable dimensions of the center conductor of the coplanar waveguide and the strip of the microstrip line. Also, the advantages and disadvantages for each structure are discussed in respect to passive microwave circuit applications.
The measurement of cryogenic antennas poses unique logistical problems since the antenna under test must be embedded in a cooling chamber. A method of measuring the performance of cryogenic microstrip antennas using a closed cycle gas cooled refrigerator in a far field range is described. Antenna patterns showing the performance of gold and superconducting Ka-band microstrip antennas at various temperatures are presented.