R. Schildberg

CYLINDRICAL: an effective CAD package for designing probe-fed rectangular microstrip antennas conformed onto cylindrical structures

This paper presents a computer-aided design tool named CYLINDRICAL. The algorithm utilizes the cavity model to design and analyze linearly and circularly polarized probe-fed rectangular microstrip antennas conformed onto cylindrical structures. A brief description of the program is given. CYLINDRICAL was used to design a circularly polarized antenna to operate in the L1 band of GPS. Validation was further done with the Ansoft HFSS package. It was shown that the antenna dimensions given by the design algorithm of CYLINDRICAL needed to be only slightly changed in order to obtain an optimized circularly polarized radiator according to the HFSS software. The tool is also very suitable for teaching graduate courses on microstrip antennas.

Low-cost Yagi-Uda monopole array

The Yagi-Uda antenna - invented in 1926 by H. Yagi and S. Uda at Tohoku University [1] in Japan, but first published in English only in 1928 [2] - has been extensively used as an end-fire antenna since then. Instead of the cylindrical antenna elements from the original work, radiators of small overall dimensions are presently achieved by means of other topologies, such as printed dipoles. Recently, a novel uniplanar quasi-Yagi design, combining both the compactness of resonant-type antennas and the broadband characteristics of traveling-wave radiators, was presented [3-4]. A current potential application of Yagi-Uda antennas is in GPRS (General Packet Radio Service), a packet-based data service over the existing GSM network. In general, the operation of mobile terminals requires antennas with omnidirectional radiation patterns; however, in case the mobile terminal is far removed from the base station, a directional antenna must be used [5]. In this paper, a new Yagi-Uda antenna topology, made up of printed monopoles, is proposed. The goal is achieving a compact, low cost, efficient radiator for GPRS applications.

Analysis and Design of Rectangular Microstrip Antennas for Educational Purposes

This paper discusses how the transmission-line model can be used in an introductory course on antennas for the analysis and design of thin rectangular microstrip antennas. As a result of adaptations made to the model, the antennas electrical parameters are shown to agree very well with experimental data and with simulations performed using commercial software. This new approach proves suitable for undergraduate courses.

New considerations in the design of low-cost probe-fed truncated corner microstrip antennas for GPS applications

Antennas produce circularly polarized waves when two orthogonal field components with equal amplitude but in phase quadrature are radiated. Probe-fed microstrip patches, classified as resonator-type antennas, are able of satisfying these requirements [1]. Nowadays, design procedure for truncated corner square patches and also for the almost square radiators is available in the literature, for instance in [2, 3]. Following this procedure, antennas with excellent axial-ratio (AR) in the operating frequency can be synthesized. Unfortunately, their input impedances are inherently inductive, mainly if thick substrates are used. A useful method of compensating for the inductance is to etch a capacitive gap on the patch, concentric (or not) with the feed probe [4, 5]. In this paper, instead of applying this standard method, a new approach is used to design truncated corner patches, printed on thick substrates. The purpose is to get the best axial-ratio and return loss at the same frequency.

Low-cost truncated corner microstrip antenna for GPS application

This paper reported a step-to-step procedure to design a low-cost FR4 GPS TCMA radiator. In order to reach the GPS specifications, in particular an acceptable value for the radiation efficiency, a thick substrate had to be used. As expected, this procedure improved the radiation efficiency but produced an input impedance that is more inductive, making difficult the antenna matching. To overcome this problem, new capacitive fractal gap geometry was designed. Experimental and simulated results indicate that it is possible to manufacture microstrip antennas with substrates having high loss tangent (like FR4) without severe degradation of their electrical performance, especially the radiation efficiency

Design of probe-fed circularly-polarized rectangular-patch thick microstrip antenna revisited

Circularly polarized (CP) microstrip antennas are largely employed in GPS receivers. Consequently, the international antenna community has devoted much effort to the theoretical and experimental research on this kind of radiator [1], overcoming many of its inherent limitations [2]. However, in spite of these efforts, the technique used to compensate for the probe inductance, when a coaxial probe is used to feed an electrically thick (a known practical way to increase bandwidth [1]-[3]) microstrip antenna, still relies on the expertise of the designer [4]-[5]. To overcome this limitation, an efficient technique for designing probe-fed CP rectangular-patch electrically thick microstrip antenna without any external network is proposed.

An Effective Strategy for Designing Probe-fed Linearly-polarized Thick Microstrip Arrays with Symmetrical Return Loss Bandwidth

Abstract— A new strategy for designing probe-fed linearly-polarized thick microstrip antennas is proposed in this work. Symmetrical return loss bandwidth is obtained by designing the patch to operate at the zero input reactance condition (Xin = 0). Applications for a single microstrip element and a linear array of suspended ones are presented. Experimental and simulated results validate the proposed strategy.

Design of probe-fed truncated corner microstrip antennas for Globalstar system

The mobile personal communications are the last generation of satellite communication. Several operators like Globalstar, among others, offer services of global cover. This system provides voice, facsimile, paging, and data transmission to subscribers using LEO (Low Earth Orbit) satellites, in a well-known Walter delta type constellation. Helical structures can be used as antennas on mobile terminals, particularly on cars or trucks, but they tend to be bulky. On the other hand, microstrip antennas are widely used in mobile communication systems, radar systems, and aerospace applications because of their low weight, low profile, and ease manufacturing. For instance, a dual-band patch antenna printed on 3.2 mm thick FR4 material and designed to satisfy both the frequency ranges of the Iridium and Globalstar systems is reported. However, the antenna radiation efficiency which is certainly low is not mentioned. Moreover, its input impedance is overall inductive due to the probe impedance. In this paper, two truncated corner patches printed on CuClad 250 GX microwave laminate, designed to operate as receiving (Rx) and transmitting (Tx) antennas on mobile terminals of Globalstar system, are presented. The design includes a new procedure to compensate the reactive inductance of the antenna input impedance.

Fabrication of low-cost spherical-circular antennas for educational purposes

Planar microstrip antennas are customary components in modern communication systems, being the subject of a variety of analytical and numerical methods developed for their investigation. On the other hand, when conformed onto spherical structures, antenna analysis and fabrication become both challenging [1], even in the classroom environment where production is not a concern. Hence, in this paper, a low-cost procedure for fabricating a spherical-circular antenna prototype that can be effectively utilized by students in advanced classes is discussed. The prototypes electromagnetic characteristics can first be quickly estimated using the LAP (Laboratory of Antennas and Propagation)-developed CAD [2] resulting in minimal optimization time with the HFSS software [3].