Radial EBG cell layout for GPS patch antennas

Abstract

A novel radial layout for mushroom-like electromagnetic-bandgap (EBG) cells surrounding a printed circularly-polarised patch antenna is proposed. Two radial EBG configurations surrounding a circular patch are compared to a reference patch on a conventional ground plane of the same dimension. The radial shape and displacement of the EBG cells around the patch offers improvements in terms of gain and axial-ratio compared to the reference antenna and is more suitable for circular geometries compared to conventional Cartesian layouts. In particular, the distance between the patch and the surrounding EBG cells is independent of the cell period, which can be arbitrarily chosen and the overall layout offers footprint reduction. parameter is critical for impedance matching and gain optimisation which in a conventional Cartesian layout is constrained by the EBG cell period and the antenna radius. Thus, the radial layout offers an extra degree of freedom, which is valuable to the antenna designer. The radial layout is also geometrically more suitable for circular patches and circular groundplanes with a resulting reduction of the overall footprint compared to conventional Cartesian layouts. Configurations investigated:The reference antenna is a circular patch antenna fed by four 50 Ω coaxial probes with a relative phase delay of 90° to excite RHCP and shorted by a central pin to suppress higher-order modes. The patch radius is R p = 17 mm and the probes are located 7 mm from the centre. A Taconic CER10 substrate of dimension 110 mm × 110 mm × 1.58 mm is used for all antennas. The initial EBG structure used is the well-known mushroom-like Sievenpiper square cell Cartesian array [7]. In order to achieve a bandgap across the GPS L1 band, the period p = w + l of the structure was chosen to be 20.4 mm (where w = 3 mm is the separation between adjacent cells and l = 17.4 mm is the square dimension), so that the overall area of the cell surface is A = 302.76 mm 2 . The diameter of the grounding vias is 1.3 mm. The dispersion diagram for this structure (Figure 1) shows the bandgap to be from 1.41 GHz to 1.75 GHz. This Cartesian array was reshaped into adjacent truncated wedge-shaped sectors to match the rotationally symmetric layout of the circular patch antenna. The area of 302.76 mm 2 was maintained which is independent of the radius of the patch antenna and the order of the ring to which the cell belongs, and the spacing between cells was w=3 mm. Two different configurations of EBG cell layouts were evaluated and compared to the reference antenna. They are an 8-sector dual-ring and a 16-sector single-ring radial arrangement as shown in Figure 2. A 1.3 mm diameter grounding via was centred in each radial cell. Table 1 lists the geometric parameters.Results: All antennas were well matched (> 10dB RL) in the GPS L1 band and the radiation properties were measured. The measured boresight gain for the reference patch was 3.9 dBic. Although a minor gain enhancement was found for the dual-ring configuration compared to the reference, ...

Electromagnetic band-gap structured printed antennas: A feature-oriented survey

“…Further, in this section, several EBG structured printed antennas for gain enhancement are reviewed based on the mechanism by placing EBG below the patch and around the patch as described above. Yang et al have significantly enhanced the gain of MSA with the use of a PBG material made of planar arrays of rectangular blocks of dielectric layers.…”

“…Mushroom like EBG with stacked patch antenna proposed has been demonstrated to increase gain, back lobe suppression, directivity and beam width increment operating at a frequency of 5.4 GHz. Several mushroom‐like EBG structures have also been proposed for improving gains of printed antennas, and the UC‐PBG cells have also been used with aperture coupled fed patch antennas for gain enhancement …”

State-of-the-art of Metamaterials: Characterization, Realization and Applications

“…Electromagnetic BandGap (EBG) cells distributed around the antenna have been used to increase the gain performance on sub-optimum ground plane by reducing the effects of surface waves. Ruvio and Ammann proposed a radial EBG-cell layout (Ruvio, Bao & Ammann, 2009)as an alternative to conventional Cartesian solutions to enable more flexible design and better circular polarization features (Fig. 2).…”

EBG Metamaterial Ground Plane for Mitigation of Multipath Signals in GNSS Antenna

“…Construction of so called vertical choke ring allows reducing size and weight somehow [5]. But more compact and lower weight construction of multipath mitigating ground plane can be obtained using high impedance structures [6][7][8][9], including radial [10], and semitransparent [11]. High impedance ground planes are formed by coupled resonant elements and are frequency selective electromagnetic band gap (EBG) structures.…”

“…It is shown, that implementation of such a ground plane in the GNSS antenna module construction allows achieving a multiband multipath mitigation without spoiling the antenna element radiation pattern and phase center stability unlike other GNSS antenna ground plane constructions [7][8][9][10][11][12][13].…”