A low-profile aperture-coupled microstrip patch antenna (MPA) using the TM10 and TM30 resonant modes to enhance the impedance bandwidth is proposed in this paper. Based on the cavity model for a square MPA, the TM10 and TM30 modes as well as both higher odd-order and even-order modes between them can be characterized. In order to combine the dual radiative resonant modes for a wide impedance bandwidth, a rectangular radiating patch with an aperture-coupled feeder is employed and theoretically investigated at first, aiming to demonstrate that all of the undesired modes between them can be removed effectively. After that, by loading the shorting pins properly underneath the patch, the resonant frequency of TM10 mode is shown to progressively turn up with slight effect on that of TM30 mode. As a result, these two radiative modes can be allocated in proximity to each other, resulting in a wide impedance bandwidth with a stable radiation pattern and the same far-field polarization. Moreover, the principal parameters of the MPA have been extensively studied in order to investigate the sensitivity in input impedance of the aperture-fed patch antenna. Finally, the proposed antenna is fabricated and measured. Simulated and measured results are found in good agreement with each other and illustrate that the antenna achieves a wide impedance bandwidth of about 15.2% in fraction or 2.32-2.70 GHz under |S ₁₁ | <; -10 dB, while keeping a low profile property with the height of 0.032 free-space wavelength. Besides, a stable gain varied from 3 to 6.8 dBi within the whole operating band is also obtained.

A new gain-enhanced patch antenna with loading of shorting pins is proposed in this paper. Four metallic pins are symmetrically placed in the two diagonals of a square patch resonator to electrically short the patch and ground plane. These shorting pins tremendously perturb the field distribution beneath the patch due to their shunt inductive effect. As these four pins are moved outward along the two orthogonal diagonals away from the center, their influence on the field distribution over the patch is strengthened to gradually raise its dominant mode, i.e., TM010 mode, resonant frequency as the pin-to-pin spacing is enlarged. At a fixed resonant frequency, the overall area of this proposed patch antenna with four pins results to be increased. As such, its radiation directivity or gain gets to be enhanced due to the enlarged antenna area. After extensive analysis is executed, two square patch antennas with and without loaded pins are designed and fabricated. The simulated and measured results agree with each other, and they have evidently demonstrated that the radiation directivity can be enhanced up to 11.0 dBi, or about 2.9 dB increment, by virtue of the proposed approach.

A single-fed microstrip patch antenna (MPA) with loading of shorting pins for high-gain circularly polarized (CP) radiation is proposed in this paper. Two sets of metallic pins are symmetrically placed along the two orthogonal diagonals of a square patch radiator at first. Due to the shunt inductive effect brought by these shorting pins, the resonant frequency of the dominant mode in this MPA is progressively tuned up so as to enlarge the electrical size of this pin-loaded patch resonator and to enhance its radiation directivity. After the optimal loading position is investigated for maximum directivity of linear polarization, one pair of the inner pins is slightly shifted in an offset to properly separate the two degenerate modes, so that the CP radiation can be excited. Moreover, upon request, either left-handed or right-handed circular polarization can be obtained by means of different position-offset scheme of the inner pins along the diagonals. After extensive analysis is executed, two equal-size CP MPAs with and without shorting pins are fabricated and tested. Simulated and measured results show good agreement and demonstrate that the CP directivity is enhanced from 8.0 (conventional MPA) to 10.8 dBic, indicating a 2.8-dB increment by means of the proposed approach.

A co-design of a wideband circularly polarized (CP) patch antenna is proposed in this paper. The patch antenna is seamlessly integrated with two bandpass filter networks consisting of one and two λ/2 resonators, respectively, which are designed to excite two orthogonal modes with equal magnitude and quadrature phase over a widened bandwidth. In co-design of this filtering antenna, the patch antenna is equivalently treated as the last-stage resonator and the output port of the filter network. In analysis of its far field, axial ratio (AR) of CP wave is mapped to its magnitude and phase responses. By simultaneously synthesizing the magnitude ratio and phase difference of the two filter networks' transmission coefficients to vary around 1° and 90°, respectively, wideband AR response with three minima is realized. Based on this design method and the theoretically derived results, a CP patch antenna prototype with a height of 0.028λ ₀ is fabricated and measured. It is experimentally demonstrated that around 8.8%, bandwidth can be achieved with VSWR <; 2, AR <; 3 dB, and 3 dB gain variation.

Pin-loaded circularly polarized (CP) patch antennas with wide 3-dB axial ratio beamwidth (ARBW) are proposed in this paper. The ARBW of a CP patch antenna is mainly dependent on its electrical width at a frequency, while the patch size at resonance is fully controlled by the shunt inductive load. First of all, four shorting pins are introduced along the diagonals of the dual-fed square patch, so as to exhibit that the 3-dB ARBW can be significantly extended if the shorting position and pin radius are properly chosen. Next, the two degenerate modes in a single-fed CP patch antenna are slightly separated in resonant frequencies by loading another pair of shorting pins along the central line of the patch, so as to excite CP radiation. After extensive analysis is executed, two patch antennas with and without shorting pins are fabricated and measured. Simulated and measured results show good agreement, and both of them demonstrate that the 3-dB ARBW is tremendously improved from 50° to 140° or gets nearly 90° increment by means of the proposed method.

A compact circularly-polarized patch antenna with wide axial-ratio beamwidth (ARBW) operating at dual bands compatible for GPS satellite navigation application is proposed in this paper. The antenna consists of two stacked patches, which account for GPS L1 band (1575 ± 2 MHz) and L2 band (1228 ± 2 MHz). To realize significant size miniaturization, four pillars are introduced and strongly coupled to the lower patch. To adjust the beamwidth response of the far-field components, the antenna is backed by a modified metallic cavity, which in turn widen the 3-dB axial ratio beamwidth (ARBW) at two operating bands effectively Finally, the proposed design with excellent performance is realized in a size of 0.368 λ0 (diameter) and 0.105 λ0 (height). Simulated and measured results show that the ARBWs at L1 and L2 bands are as wide as 173° and 133°, respectively. For practical application, its satisfactory GPS signal receiving capability is also verified by outdoor positioning test.