Krzysztof Wincza

Design of Compensated Coupled-Stripline 3-dB Directional Couplers, Phase Shifters, and Magic-T's—Part I: Single-Section Coupled-Line Circuits

The problem of discontinuities in coupled-stripline 3-dB directional couplers, phase shifters, and magic-Ts, regarding the connections of coupled and terminating signal lines, has been comprehensively investigated for the first time. The proposed equivalent circuit of these discontinuities, of which parameters can be computed in a process of fitting curves of the circuit and electromagnetic analyses, has been used for accurate modeling of coupled-stripline circuits. It has been shown that parasitic reactances, which result from connections of signal and coupled lines, severely deteriorate the return losses and the isolation of such circuits, and that these discontinuity effects can be substantially reduced by connecting compensating shunt capacitances to both coupled and signal lines. Results of measurements carried out for various designed and manufactured coupled-line circuits are most promising and prove the efficiency of the proposed compensation technique. This paper describes the technique of capacitive compensation of discontinuity effects in single-section coupled-line circuits

Broadband 4

An innovative approach for realization of broadband 4 times 4 Butler matrices, in which broadband symmetrical multisection 3-dB/90deg directional couplers are used as basic elements, has been presented. A new technique for realization of center crossover together with 45deg phase shifters is proposed where phase correction networks, consisting of a number of coupled-line sections, are applied. The use of the proposed phase correction networks allows to achieve equal-ripple 45deg differential phase characteristics in a wide frequency range. Numerical results for the design of broadband 4 times 4 Butler matrices consisting of multisection symmetrical 3-dB/90deg directional couplers having three, five, seven, and nine coupled-line sections in conjunction with phase correction networks having an appropriate number of coupled-line sections are given in a tabular form. A method of performance improvement for broadband Butler matrices by the combinatory use of directional couplers consisting of different number of coupled-line sections is also proposed. To verify the presented analysis a broadband 4 times 4 Butler matrix consisting of six 3-dB/90deg three-section symmetrical coupled-line directional couplers and two single-section coupled-line phase correction networks has been designed, manufactured, and measured. Results of measurements of the designed Butler matrix fully confirm the validity of the proposed technique of broadband 4 times 4 Butler matrix realization.

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The paper presents an antenna design for use in a nonlinear junction detection device. To achieve wide bandwidth a capacitive feed technique is used in which small probe feed elements are coupled to the radiating patch. In order to minimize the overall antenna size both receiving and transmitting antenna elements have been integrated into one dual-band structure having two separate excitation ports. High isolation between ports is achieved to avoid direct interferences between a transmitter and a receiver. Results of theoretical analysis are presented agree well with the experimental ones.

4 Butler Matrices as a Connection of Symmetrical Multisection Coupled-Line 3-dB Directional Couplers and Phase Correction Networks

In this paper the effect of curvature radius on radiation patterns in multibeam antennas fed by a Butler matrix has been shown. Calculation results taking into account the change of amplitude and phase of the signal received at each radiating element caused by the array curvature for different radii have been presented. A simple compensation technique is studied which allows us to achieve proper radiation patterns by adding phase shifters in outer channels. It is shown that by using this technique we can obtain radiation patterns of conformal antenna arrays which with respect to the side lobes are comparable with planar antenna arrays. Measurement results of a 4times1 conformal antenna array fed by a Butler matrix are presented and agree well with the calculated ones

Dual-band Capacitive Feed Antenna for Nonlinear Junction Detection Device

In this paper we present the design of a broadband series-fed low-cost antenna array operating within 5.5 GHz frequency band. In order to achieve broadband operation a rectangular patch is used in which two different resonant frequencies can be excited. It has been shown that a linear polarization in such a radiating element can be achieved by inserting a rectangular slot.

Influence of Curvature Radius on Radiation Patterns in Multibeam Conformal Antennas

An integrated dual-band dual-polarized antenna element for SAR applications is presented. The antenna operates in L and C bands in which 8% and 7% bandwidths are achieved respectively. In order to ensure wide bandwidth of the radiating elements stacked patches in both frequency ranges are used. The L-band radiating elements (both driven and parasitic patches) have been perforated in such a way that can be integrated with four C-band elements. In order to achieve high isolation between ports exciting orthogonal polarization dual-probe technique has been applied in L-band and orthogonal placement of two coupling slots has been applied in C-band. To allow for further integration within a larger array the feeding network has been designed in multilayer stripline structure. The measured results of the manufactured antenna element are in good agreement with the calculated ones.

Broadband low-cost series-fed antenna array for Wireless LAN applications with corner-coupled patches

Stacked dual-polarized antenna element for SAR applications is presented. The antenna element operates in C-band having 8% bandwidth. In order to achieve high isolation between ports generating orthogonal polarization orthogonal placement of two coupling slots has been applied. To provide additional isolation between vertical and horizontal polarizations the feeding lines generating orthogonal polarizations have been placed on different layers of multilayer stripline structure. Contactless hairpin-type band-pass transition between adjacent stripline layers has been designed and applied within the antenna feeding network to eliminate via interconnections and possible excitation of leaky modes. The measured results of the manufactured antenna element are in good agreement with the calculated ones.

Integrated dual-band dual-polarized antenna element for SAR applications

The range of potential application areas for low profile microstrip antenna elements would certainly increase if it were demonstrated that they are capable of generating high quality circular polarization over very wide elevation angles, and not only in a narrow angle around the main axis of the antenna. This property is of great importance when application decisions are being made. In order to keep an appropriately low profile and weight, the patch feed should be made in the form of printed circuit on a thin piece of dielectric substrate bonded to a much thicker substrate bearing the wide printed lines needed to transmit electromagnetic energy over larger distances, such as those between an RF front-end and the antenna (P. Kabacik et al, IEEE APS Int. Symp., July 2005). The smoothness of printed lines and slots on such thin substrates make this a good approach for applications with wavelengths up to the lower millimeter range (the Ku band).

Dual-polarized stacked C-band antenna element with novel hairpin-type contactless stripline to stripline transition in multilayer integrated structure for SAR applications

The presented antenna is lightweight, has a low profile and provides outstanding parameter values over a wide bandwidth. In particular, such good circular polarization across a broad angular range in the forward hemisphere is of great practical value and has been rarely reported on in the literature for such thin antennas to the best of our knowledge. It should be mentioned that the proposed antenna generates very good circular polarization with a use of a single patch thus, clustering elements to achieve very good circular polarization is unnecessary.

Optimizing circular polarization in broadband lightweight patch antennas

The paper presents the progress of investigations on small lightweight low gain antennas (LGA) for use onboard minisatellites and microsatellites. The LGA primary task is to ensure low rate data exchange in downlink and uplink communication channels with possible omnidirectional coverage, irrespective of the orientation of the spacecraft.