Alois Holub

A Novel Microstrip Patch Antenna Miniaturization Technique: A Meanderly Folded Shorted-Patch Antenna

A novel microstrip patch antenna miniaturization technique based on multilayer meanderly folded shorted- patch structure is introduced. The technique enables a decrease of the original shorted (quarter-wavelength) patch dimension by the factor l/N where N is a number of vertically placed patch plates above the ground plane while maintaining a quarter wavelength resonant length. The antenna operational principle is explained via both E-field distribution inside the antenna structure and the surface current distribution on the conductive parts of the antenna. Two variants of the miniaturized patches with the footprint dimension approx. ~ lambda0/12 and lambda0/16 are simulated, realized and measured.

Collinear Microstrip Patch Antennas

The original idea of the collinear principle in the antenna design comes from Franklin (Franklin, 1925). He faced the problem of resonant long wire antennas. In principle, the standing wave current distribution on the long straight wire produces n radiation lobes of the same level, depending on the number n of half-wave antenna sections. Employing nonradiating quarter-wave stubs Franklin converted the original out-phase current distribution into an in-phased distribution of currents on collinear segments (represented by solid red arrows in Fig. 1), thus producing only one major radiation beam. A key advantage of such arrangement is represented by the high gain of the antenna with the properties of series antenna array, whereas the simplicity of the single feeding point is maintained. All antenna structures based on this principle are known as collinear arrays (CoA). The latter are composed of in-phase fed radiating elements that lie in the straight line. Their radiation is typically broadside and perpendicular to the axis of collinear elements. Since Franklin’s times many collinear antenna structures have been proposed. The principle representatives of the CoA are described later on.

Impedance Properties and Radiation Efficiency of Electrically Small Double and Triple Split-Ring Antennas for UHF RFID Applications

This letter is targeted at investigation of electrically small planar antennas, formed by double and triple split rings that are intended to serve as tag antennas operated within the European UHF RFID band. An extensive systematic study of possible geometrical configurations demonstrates the range of their achievable input impedances (complex conjugate to typical UHF RFID integrated circuits) in the case that both structures electrically decrease below the limit for electrically small antennas, i.e.,

Planar version of Collinear Microstrip Patch Antenna

ka < 0.5

Electrically small loop surrounded by a “shell” of concentric split rings: Principle and properties

. The advantage of the triple split-ring version over the standard double split-ring one consists in reduction in its electrical size and concurrent maintenance of the required range of input impedances and high radiation efficiency. Samples of both structures were manufactured and measured, and their electrical properties were critically compared.

Branched F-type Antenna Array

The paper presents a planar version of collinear microstrip patch antenna that exhibits further gain enhancement compared to collinear microstrip patch antenna due to the lateral extension of in-phase source current area of radiation element. The principle of operation is similar as in case of collinear wire antennas. The basic idea consists in the use of TM0x mode with geometrical perturbation of radiation motif by inner slot(s) and lateral notches introduced in such a way that they eliminate radiation from even half current wavelengths. Detailed principle of an antenna operation explained via vector surface current distribution, determination of initial antenna dimensions and final optimization in planar simulator IE3D are presented. The prototype of the antenna operating in 2.4 GHz ISM band has been realized and measured.

Enhanced Gain Microstrip Patches Operating on Higher Order Modes

The paper describes a novel electrically small antenna structure and investigates its physical principle and properties. The antenna is formed by small planar loop with a “shell” of three concentric split rings with external electrical dimension ka=0.4. The structure has been designed with complex impedance Zin ∼ 22 + j195 Ω to be utilized as UHF RFID tag antenna. The physical principle is explained via the simulated surface current distribution and several parametrical studies.

Microwave radar sensors for active defense systems

This paper presents new ideas of improvement of planar F-type antennas by parallel array approach. This solution exhibits further gain enhancement compared to classical F-antenna with omnidirectional radiation. The antenna array is obtained by parallel line up of radiating elements. It causes radiation in two directions (forward and backward), which is not useful for practical usage. The reflection plane is applied to prevent backward radiation and to enhance a directivity. The arrays of 1, 2 and 3 elements are presented and compared. The advantage of this type of antenna is its relatively simple implementation.

Vertically meander-folded, shorted-patch antennas

Novel topologies of rectangular microstrip patches providing broadside radiated one point fed radiators with enhanced gain are compared. The principle of the gain enhancement is based on an extension of a source area. Dominant in-phase current distribution on the patch is maintained by using higher order mode and geometrical modification of the patch topology. That is achieved by introducing suitable perturbation elements in the shape of slots and notches. Two principal patch topologies operating on TM21 and TM03 modes are described. A comparison of simulated and measured properties of realized prototypes at 10 GHz band are presented. The results show that gain 12.3 dBi of single patch can be reached.