Dual slot-coupled microstrip antenna for dual frequency operation

A new dual slot-coupled circular antenna for dual frequency or dual polarisation operation is proposed. By optimising the placement of the two slots, high isolation between two ports is achieved. Experimentally, an isolation of more than 35 dB is obtained at L-band.<>     

Dual-polarized slot-coupled planar antenna with wide bandwidth

A new dual-polarized slot-coupled microstrip patch antenna is presented, which can achieve high-isolation, low cross-polarization levels, a wide bandwidth, and low backward radiation levels. The coupling slot is an H-shaped slot. For wide bandwidth and easy integration with active circuits, it uses slot-coupled stacked microstrip patches. The theoretical analysis is based on the finite-difference time-domain (FDTD) method. First, a parametric study on the input impedance of the antenna with a single input port is presented. Based on the results, a dual-polarized microstrip antenna is designed, fabricated, and then measured. The measured return loss exhibits an impedance bandwidth of over 20.9% and the isolation between two polarization ports is better than 36 dB over the bandwidth. The cross-polarization levels in both E and H planes are better than 22 dB. The front-to-back ratio of the antenna radiation pattern is better than 21 dB. Both theoretical and experimental results of return loss, isolation, and radiation patterns are presented and discussed.     

Dual-frequency microstrip antenna with dual circular polarisation

A single-feed dual-frequency microstrip patch antenna that can produce dual circular polarisations (CP) is presented. The microstrip antenna has an annular-ring patch and is excited by an L-shaped microstrip line through the coupling of a ring slot in the ground plane. The occurrence of the dual CP is because the magnetic currents circulating along the ring slot at two specific frequencies have opposite flowing directions. Both simulated and measured results are provided to validate the CP performance of the proposed antenna     

Dual aperture-coupled microstrip antenna for dual or circular polarisation

A new method for radiating dual or circular polarisation with a printed circuit antenna element is described. A square microstrip patch on one substrate is coupled to a pair of microstriplines on another substrate via two orthogonal, rectangular apertures in a common ground plane. Quadrature excitation of the system results in circularly polarised radiation.     

Compact microstrip-T coupled patch antenna for dual polarisation and active antenna applications

A novel way of feeding single-layer microstrip patch antennas using electromagnetically coupled microstrip-T junctions is proposed. The measured isolation and 10 dB bandwidth of an X-band dual polarised antenna are /spl sim/32 dB and 2.1%, respectively, on an /spl epsiv//sub r/ 3.0 substrate. Since both ports of the antenna are electromagnetically coupled, the proposed antenna eliminates the need for capacitors in the RF path for active antenna applications.     

Passive filter for increasing directivity in dual polarisation antenna systems

A novel design for a passive microwave filter is presented. The filter consists of a stacked array of low loss dielectric layers, whose permittivity profile alters in a near sinusoidal manner. The radiation property of the filter is investigated for both co- and crosspolarisation and it is shown that the filter acts as an apodiser and a beam shaper.<>     

Annular slot-coupled dielectric resonator antenna

An annular slot-coupled dielectric resonator antenna is investigated experimentally. As compared with the previous rectangular-slot version, the new configuration offers a much wider bandwidth of 18%. The return loss, radiation patterns, and antenna gain of the configuration have been measured and are discussed     

Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna

A novel coupling scheme to a rectangular dielectric resonator antenna is proposed and investigated. In particular, coupling to the resonator is achieved through a narrow slot at the end of a coplanar waveguide (CPW). The objectives of this design are to maximize the coupling, match the dielectric resonator to the CPW feed line, achieve resonance at the desired frequency, obtain linear polarization with low cross polarization components, and minimize back radiation without using a back conductor. An approximate and quick design approach is given followed by more accurate design and analysis using commercial software. The antenna was fabricated and tested. Measurements match well with simulation results.     

Modal expansion method of analysis for slot-coupled microstrip antenna

A modal field expansion technique together with the Poynting theorem are used to derive the input impedance of a slot-coupled microstrip antenna. The approach leads to easier and lower computational requirements. Predicted values of input impedance are compared with previous theoretical and experimental results.<>     

Slot-coupled microstrip antenna for broadband circular polarisation

Broadband circular polarisation (CP) operation of single-feed slot-coupled microstrip antennas is achieved using an inclined nonlinear coupling slot. This nonlinear slot, end-loaded with two V slots, significantly broadens the CP bandwidth to about 2.1 times that obtained using a simple inclined coupling slot for CP operation. Details of the antenna design are described, and experimental results of the CP performance are presented     

Circular polarisation design of a single-feedequilateral-triangular microstrip antenna

By inserting a narrow slit at the edge of an equilateral-triangular microstrip patch, circular polarisation (CP) radiation can be obtained using a single probe feed. This CP design is easy to implement. Details of the antenna design are described, and experimental results of the axial ratio and radiation pattern are presented and analysed     

Cavity-backed slot-coupled dielectric resonator antenna excited bya narrow strip

The input impedance of the cavity-backed slot-coupled dielectric resonator antenna excited by a slender strip is investigated theoretically and experimentally. The effect of the cavity size and strip length on the input impedance are studied and discussed     

Design of square-ring microstrip antenna for circular polarisation

The design of a square-ring microstrip antenna with circular polarisation (CP) is presented. To compact the antenna size and overcome the high impedance problem, the CP antenna is excited by a coupling strip located inside the square-ring patch. Several prototypes of the square-ring CP antennas with various substrate thickness (0.013-0.09/spl lambda//sub 0/) have been constructed and studied experimentally, and their coupling-strip designs and CP performance are described.     

Dual polarisation of microstrip reflectarray antenna

Dual polarisation of a microstrip reflectarray was demonstrated for the first time. A 16 element array of square microstrip patch antennas operating in the X-band was used to reflect the main beam 20" off broadside in both the E-plane and H-plane     

Dual-frequency planar antenna for handsets

Cellular telephone handsets are now being designed to have dual-mode capabilities. In particular, GSM and DCS1800 modes are used in Europe. And PCS and AMPS modes are used in the USA. A novel planar dualband internal antenna for handsets which operates in the ~0.9 and 1.8 GHz bands is proposed. The dualband antenna has almost the same size as a conventional internal antenna operating in the 0.9 GHz band. Good dual-band operation was obtained for frequency ratios in the range 1.3-2.7     

Compact polarisation selectable radial cavity antenna

The generation of both hands of circular (CP) in addition to vertical and horizontal linear (LP) polarisation from a 6.5 mm-deep radial cavity antenna is demonstrated in the frequency range 8.1-8.6 GHz by incorporating a compact four port coaxially fed polariser, thus removing the need for an orthomode transducer. The polariser is realised using metal post inserts positioned inside a circular waveguide; its length is 59 mm.     

The slot-coupled hemispherical dielectric resonator antenna with a parasitic patch: applications to the circularly polarized antenna and wide-band antenna

The aperture-coupled hemispherical dielectric resonator antenna (DRA) with a parasitic patch is studied rigorously. Using the Green's function approach, integral equations for the unknown patch and slot currents are formulated and solved using the method of moments. The theory is utilized to design a circularly polarized (CP) DRA and a wide-band linearly polarized (LP) DRA. In the former, the CP frequency and axial ratio (AR) can easily be controlled by the patch location and patch size, respectively, with the impedance matched by varying the slot length and microstrip stub length. It is important that the AR will not be affected when the input impedance is tuned, and the CP design is therefore greatly facilitated. For the wide-band LP antenna, a maximum bandwidth of 22% can be obtained, which is much wider than the previous bandwidth of 7.5% with no parasitic patches. Finally, the frequency-tuning characteristics of the proposed antenna are discussed. Since the parasitic patch can be applied to any DRAs, the method will find applications in practical DRA designs.     

Helix antenna with optimised main-beam polarisation

A helical antenna with a high degree of polarisation purity for directions near endfire is described. The antenna structure was optimised by numerical analysis of its polarisation properties. Theoretical and experimental results are presented.     

Reconfigurable microstrip antenna with polarisation diversity

A single probe-fed reconfigurable microstrip patch antenna with symmetric cross slots is proposed. By controlling four pin diodes on the patch slots, the proposed antenna has right hand circular polarisation, left hand circular polarisation or linear polarisation.