Michel Clenet

A New Wideband Circularly Polarized Hybrid Dielectric Resonator Antenna

Dielectric resonator antennas (DRAs) have been targeted in the past two decades as a potential solution for wideband antennas. Although DRAs offer wider frequency band and smaller size than patch antennas, their design to obtain good circular polarization over a wide frequency band can be challenging. In this letter, a new hybrid DRA has been investigated to produce circular polarization over a wide frequency band. The targeted application is to produce a compact antenna for satellite navigation systems. The obtained design was fabricated and measured, showing impedance matching from 1.08 to 1.82 GHz, i.e. over 50% bandwidth. The radiation characteristics of the antennas were also characterized. The achieved gain is over 1.5 dBic, and the axial ratio (AR) is under 1 dB at boresight over the 1.131.63 GHz frequency band. The half-power beamwidth is greater than 75°, and the axial ratio beamwidth (AR < 3 dB) is over 100° .

A Compact Wide-Band Rat-Race Hybrid Using Microstrip Lines

A compact microstrip rat-race hybrid with a 50% bandwidth employing space-filling curves is reported in this letter. The footprint of the proposed design occupies 31% of the area of the conventional similar design. Across the frequency bandwidth, the maximum amplitude unbalance is 0.5 dB, the phase variation is plusmn5deg , the isolation is better than 25 dB and the return loss is greater than 10 dB. Moreover, the circuit is planar, easy to design, and consists of only one layer without requiring plated thru holes, slots or bonding wires.

A Broadband Folded Printed Quadrifilar Helical Antenna Employing a Novel Compact Planar Feeding Circuit

A broadband printed quadrifilar helical antenna employing a novel compact feeding circuit is proposed in this paper. This antenna presents an excellent axial ratio over a wide beamwidth, with a 29% bandwidth. A specific feeding circuit based on an aperture-coupled transition and including two 90° surface mount hybrids has been designed to be integrated with the quadrifilar antenna. Over the bandwidth, the measured reflection coefficient of the antenna fed by the wideband compact circuit has been found to be equal to or lower than -12 dB and the maximum gain varies between 1.5 and 2.7 dBic from 1.18 to 1.58 GHz. The half-power beamwidth is 150°, with an axial ratio below 3 dB over this range. The compactness of the feeding circuit allows small element spacing in array arrangements.

An aperture-coupled circularly polarized stacked microstrip antenna for GPS frequency bands L1, L2, and L5

This paper has investigated the technique of stacking microstrip antennas to achieve dual frequency operation for GPS frequencies L1 and L2/L5. The coupling between the two patches is dependent on the relative size of the patches and also whether the top patch is smaller or larger than the bottom patch. The relative patch sizes must be adjusted for proper impedance match. The design of this antenna was a tedious process and required numerous empirical tunings due to the number of interacting parameters. The designed antenna is currently under fabrication and measured results will be provided during the presentation.

Laminated waveguide as radiating element for array applications

This paper reports on the study of a new antenna as well as a five-element array prototype developed for communications in K-band and suitable for low temperature co-fired ceramic technology. The radiating element is an open waveguide realized in laminated technology. A special coaxial-to-waveguide transition has also been designed as feed port for measuring the prototypes. The element exhibits a 1 GHz bandwidth centered at 20.7 GHz and a 2.7 dBi gain. In an array configuration, mutual coupling between the elements is lower than -18 dB across the bandwidth. The simulated boresight radiation pattern of a five-element array is stable over the bandwidth and the gain reaches 9.2 dBi at 20.7 GHz. The measurements of the radiation pattern for a 20-degree scan angle, as well as the simulation, demonstrate the scanning capability of this array

A Compact Wideband Dielectric Resonator Antenna with a Meandered Slot Ring and Cavity Backing

We design a compact cavity-backed antenna structure where a dielectric resonator (DR) element is surrounded by a meandered circular slot ring to enhance radiation efficiency. The DR for the antenna is cylindrical in shape, and four degenerate HE11δ modes are excited and driven by four, quadrature-fed aperture-coupled slots. Such a compact implementation hybridizes operation of the DR with the miniaturized ring as well as the four aperture-coupled slots for circular polarization. Measured realized gain values are greater than 5 dBic from 1.14 to 1.55 GHz defining a bandwidth of more than 30%. In addition, the half-power and 3-dB axial-ratio beamwidths were measured to be more than 100 ° and 200 °, respectively. The proposed design technique to employ such a secondary meandered slot ring may also be useful to improve antenna gain, bandwidth, and efficiency for other antenna and array structures.

Wideband circularly polarized antenna elements for GPS/GNSS applications developed at DRDC Ottawa

This paper presents several wideband circularly polarized antennas for GPS/GNSS applications that have been developed at Defense Research & Development Canada – Ottawa. Three radiating elements were designed using different technologies. All of them exhibit very good performance in terms of impedance matching, coverage, gain and axial ratio over the entire GNSS frequency band (1.15 GHz to 1.62 GHz). Their characteristics are presented and compared in terms of EM performance and size.

Arrays of 4 circularly polarised aperture-coupled-fed stacked patch antennas for GPS interference mitigation

This paper presents an array antenna composed of 4 identical circularly polarised aperture-coupled-fed stacked patches for mitigation of GPS interference. The individual radiating elements have been designed to cover the three GPS frequency bands L1, L2 and L5, with a good polarisation ratio over the top hemisphere. Two array topologies are considered. The characteristics of the arrays are presented in terms of return loss, mutual coupling, gain and axial ratio. Radiation patterns synthesized for a boresight beam and, as rejection is of interest, for a boresight null, are provided and analyzed. The results give insights on the capability of the array for GPS interference mitigation.

A review of research on GNSS antenna technologies at DRDC Ottawa Research Centre

GPS is currently the main Global Navigation Satellite System. GLONASS, the Russian GNSS, became fully operational few years ago. Other GNSSs will become soon available and a new generation of low cost receivers can take advantage all the systems to improve accuracy or robustness in a challenged environment. Such receivers need performant antennas and RF front-ends. This paper presents a review of research work on GNSS antenna technologies carried out at DRDC Ottawa Research Centre in collaboration with several universities.

A compact cylindrical dielectric resonator antenna for MIMO applications

In this work an eight-port cylindrical dielectric resonator antenna (DRA) is presented for multiple-input and multiple-output (MIMO) systems. Other possible applications include polarization diversity and other phased arrays for wireless communications. The antenna is defined by a cylindrical dielectric resonator with εr = 30. Four HE11δ modes are excited within the DRA by slots which are etched out of the ground plane of the FR-4 substrate onto which the DRA is mounted. Each of these slots are excited by two 50-Ω microstrip transmission lines. This work provides a significant size reduction when compared with previous designs by the authors. In particular, when this work is compared to previous antenna structures which utilize a similar 4-port feeding scheme, a total antenna height and ground plane reduction of 37% and 44% is achieved, respectively. The new eight-port antenna design is also low-profile, compact (90 mm by 90 mm), and offers good radiation performance with a bandwidth of more than 30%.