Adam Narbudowicz

Dual-Band Omnidirectional Circularly Polarized Antenna

A dual-band omnidirectional circularly polarized antenna is proposed. The antenna comprises back-to-back microstrip patches fed by a coplanar waveguide. A very low frequency ratio of 1.182 has been achieved, which can be easily tuned by adjusting four lumped capacitors incorporated into the antenna. An analysis of the omnidirectional circular polarization mechanism as well the dual band operation is provided and confirmed by numerical and experimental data. Key parameters to tune the resonant frequencies and the axial ratio have been identified. The prototype antenna provides omnidirectional circular polarization in one plane with cross polar isolation better than 12 dB for both frequency bands.

Dual Circularly-Polarized Patch Antenna Using Even and Odd Feed-Line Modes

This communication proposes a new patch antenna with dual circularly polarized capability at 2.575 GHz. The design exploits the even and odd modes in a coplanar waveguide transmission line and enables simultaneous right- and left-handed circular polarization, with two individual excitation ports. A patch antenna is fed by multimode transmission line and the advantages and disadvantages are discussed. A prototyped antenna realized up to 20 dB isolation between ports with S21 <; -10 dB bandwidth of 87 MHz. Realized gains for the two modes of operation are 5.77 and 7.23 dBic. The proposed structure is compact and easy to manufacture.

Bidirectional circularly polarized microstrip antenna for GPS applications

A bidirectional circularly polarised (CP) antenna for 1.575 GHz GPS L1 band is presented. The antenna consists of two back-to-back coupled patches and is fed directly by 50Ω Coplanar Waveguide (CPW). It is compact and relatively easy to manufacture compared to other antennas with similar properties. The bidirectional CP pattern is achieved by proper adjustment of patch dimensions as well as feed parameters. A study of the key parameter is provided.

Switchless Reconfigurable Antenna With 360° Steering

A novel reconfigurable antenna capable of rotating a bidirectional pattern by 360° in azimuth is proposed. The antenna has two ports, no aperture switching components, and offers a more compact solution than an array. It provides a reconfigurable pattern in the band 2.525-2.595 GHz and a fixed omnidirectional pattern from 2.235 to 2.725 GHz. The measured gains for four investigated configurations are between 2.1 and 3.1 dBi with total efficiencies between 80% and 89%. The antenna is intended to operate with software defined radio [digital beamforming or multiple-input-multiple-output (MIMO)], where the potential of pattern generation using the dual-port antenna can be fully exploited. It offers multiuser pattern reconfiguration at low cost within a limited volume.

Circularly Polarized terminal antennas for emerging wireless systems

Several types of omni-directional Circularly Polarized (CP) antennas are presented, which are employed by three different types of feedlines: Coplanar Waveguide (CPW) fed, Microstrip fed, and Differential-fed, to achieve omni-directional CP performances. The Dual-frequency Omni-directional CP antenna is proposed by using slot and inductor embedded into radiated patches. These omnidirectional CP antennas have potential application on GPS, WLAN and RFID systems.

Shaping the axial-ratio footprint of crossed-dipole antennas

A method is proposed to adaptively change the axial-ratio beam of simple circularly-polarized antennas. It is shown, that by varying the phase shift between two orthogonal elements the axial-ratio beam shape can be dynamically adjusted. This allows control of the direction of minimum axial-ratio and the ability to increase or decrease the beamwidth in one of two planes. The method is intended for satellite navigation systems: it can improve the rejection of reflected signals in varying propagation conditions (e.g. urban canyons), while using simple and low-cost circularly-polarized antennas.

Omnidirectional circularly polarized patch antenna with post manufacture characteristic refinement

We propose an omnidirectional circularly polarised planar microstrip patch antenna, in which both impedance bandwidth and circular polarization properties can be adjusted after antenna manufacture. This is done by appropriately tuning four adjustable capacitors, incorporated into the patches. To demonstrate the properties, the proposed antenna is tuned to the GPS L1 band and then re-tuned for Beidou/Galileo E2 band by only changing capacitors values. Design guidelines for such retuning are provided.

Vivaldi array for generation of UWB circular polarization

A two antenna array is proposed for generating circular polarization for an ultra-wideband system. It consists of two orthogonal antipodal vivaldi antennas and a feed network which provides the appropriate phase and amplitude over the band of interest. The proposed structure is low cost and easy to manufacture, offering an axial-ratio bandwidth of 74%.

Reconfigurable Axial Ratio in Compact GNSS Antennas

A new adaptive technique for steering the direction of minimum axial ratio (AR) (<;1 dB) toward the reflected or jamming signal is proposed for global navigation satellite systems antennas. It relies on simple, low cost commercially available circularly polarized antenna elements without influencing their gain. Its performance is demonstrated using two different antenna geometries, with five different configurations. The measurements agree well with simulation and theoretical calculations. The technique allows a combined 1-dB AR beamwidth of up to 83°.

Low-Cost Multimode Patch Antenna for Dual MIMO and Enhanced Localization Use

This communication proposes a simple, low-cost multimode patch antenna combining good multi-in multi-out (MIMO) performance with precise angle of arrival (AoA) estimation. The AoA is based on the monopulse antenna concept; however, unlike in radar applications, the necessity for complex circuitry is replaced by the intrinsic properties of even and odd resonant patch modes. This capability is advantageous for future “Internet of Things” antennas, embedded into low-cost and size-constrained devices. The envelope correlation coefficient, measured in an anechoic chamber, is below 1.5%, ensuring good MIMO performance. An exemplary addition to localization algorithm exploiting antenna properties is demonstrated.