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 ...<inline-formula> <tex-math notation="LaTeX">\lambda </tex-math></inline-formula>/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 <inline-formula> <tex-math notation="LaTeX">0.028\lambda _{0} </tex-math></inline-formula> 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.
A square patch antenna operating under TM 03 mode is proposed in this paper to realize gain enhancement, sidelobe reduction, and adjustable beamwidth by reshaping the surface current distribution on ...the patch resonator. On the one hand, by introducing transverse slots along the central line of patch, the medial part of out-of-phase longitudinal current is interrupted to circulate with little radiation. In this way, the patch serves as a full-wave dipole rather than a <inline-formula> <tex-math notation="LaTeX">3\lambda </tex-math></inline-formula>/2 one, and thus, the sidelobe level (SLL) in the E-plane is substantially reduced. On the other hand, the slots are installed in proximity to the nonradiative edges and at the patch center, respectively, to arouse distinctive effect on the current densities across the width of patch. Consequently, the beamwidth in the H-plane can be freely adjusted by different configurations of these slots. At last, a square patch antenna with three cascaded slots loaded along the central line is designed, fabricated, and tested. The simulated and measured results show that the directivity of a single proposed patch antenna can achieve as high as 13.3 dB with the SLL reduced to about −20 dB.
A wideband circularly polarized (CP) patch antenna with enhanced axial ratio (AR) bandwidth via co-design of feeding network is proposed in this paper. One <inline-formula> <tex-math ...notation="LaTeX">\pmb \lambda/4 </tex-math></inline-formula> resonator and one <inline-formula> <tex-math notation="LaTeX">\pmb \lambda/2 </tex-math></inline-formula> resonator are introduced and coupled in proximity to two orthogonal points of a square patch radiator to excite two orthogonal modes. These two resonators not only function as impedance matching elements to achieve equal magnitude of two orthogonal modes in a wide frequency band but also provide the required 90° phase difference. In this way, two minima in the AR response appear, resulting in extended AR bandwidth. The wideband design of the antenna is carried out based on the equivalent circuit model, where the patch radiator is treated as a conductance, inductance, and capacitance parallel resonator. In particular, the feeding network and the patch are jointly considered as a three-port network for synthesis design. By mapping the radiated far field to the magnitude and phase on the radiation conductance in the circuit model, the AR response of the antenna becomes predictable in a straightforward manner. Measured results experimentally demonstrate that the 3-dB AR bandwidth of our proposed CP patch antenna is 2.7 times that of the traditional one fed with two 90° offset lines.
A single-layer microstrip-fed patch antenna with capabilities of both bandwidth enhancement and harmonic suppression is proposed. For this purpose, a pair of λ/4 microstrip-line resonators is ...introduced and coupled in proximity to a rectangular patch. The wideband property can be obtained by making effective use of the two resonances introduced by the radiating patch and nonradiating λ/4 resonators. Different from other reported dual-resonance patch antennas, the proposed antenna does not require the electrically thick substrate, so it has attractive low-profile property. Thanks to the good features of λ/4 resonators and capacitive feeding scheme, harmonic radiating modes of the patch antenna can be significantly suppressed as highly demanded in modern highly integrated communication systems. The working principle, equivalent circuit, and design procedure are extensively described. Finally, a prototype antenna operating at 4.9 GHz is designed and fabricated. The measured results show that its bandwidth is 2.7 times wider than that of the traditional insert-fed patch counterpart, and the harmful spurious radiation from other higher order radiating modes has been effectively suppressed.
This paper proposes an all‐metal wideband circularly polarized (CP) single‐patch antenna based on TM11 mode. The conventional square patch is divided into four small square patch units by loading ...metal shorting walls under the two vertical centerlines. The shorting walls are windowed to facilitate coupling between the adjacent units. When the TM11 mode is excited, the coupling windows not only distribute energy but also provide the 90° phase difference required for CP radiation. An additional feeding network is not required, and its profile is less than 0.05λ0 (λ0 is the free space wavelength at the center frequency). Three minima in the axial ratio (AR) response are present. The results show that right‐hand circularly polarized (RHCP) radiation is achieved. The measured 3 dB AR bandwidth is 6.9%, ranging from 1.52 to 1.62 GHz, and the RHCP realized peak gain is 7.72 dBic. An all‐metal construction suitable for satellite communication systems is designed that has superior performance in harsh space environments.
An all‐metal wideband circularly polarized (CP) single‐patch antenna based on TM11 mode is proposed. The proposed design is primarily derived from the conventional square patch antenna, with the introduction of windowed shorting metal walls. These walls divide the patch into four parts, and the coupling window can alter the surface current distribution of each part to achieve CP radiation.
A quad-mode dual-band dual-sense circularly polarized (CP) single patch antenna is proposed. The four boresight radiating modes are obtained by simply loading a stub and U-slot on the patch. The ...characteristic mode analysis (CMA) is utilized to reveal the operational principles of the patch. The control over the antenna's frequency ratio and the sense of circular polarization is achieved by independently manipulating the different modes. This is accomplished by altering the dimensions of the patch, U-slot, and the stub. To further validate the effectiveness of the proposed design method, a patch antenna prototype has been designed and fabricated for experimental validation. In both bands, left-hand circular polarization and right-hand circular polarization were obtained separately. The measured impedance bandwidths in the low and high bands are 12.7% and 13%, respectively, corresponding to a 3 dB axial ratio (AR) bandwidths of 2.47% (3.2-3.28 GHz) and 1.17% (4.26-4.31 GHz).
In this article, a fundamental method based on mutual conductance elimination is proposed for the ultimate decoupling of closely spaced antenna pairs. First, the mutual coupling between radiators is ...characterized by lossy J/K inverters, and the analysis with circuit models shows that the traditional lumped loading method can only suppress the mutual susceptance. Particularly, the decoupling will not be ultimate unless the mutual conductance is further eliminated, which requires equal modal conductance of the odd and even modes of the antenna pair. After that, a method based on antenna-shape modification is proposed, and three types of antennas are designed with characteristic mode analysis (CMA). As for the single-band and wideband patch antenna pairs, by changing the patch shape into a parallelogram and adjusting the patch angle, the modal conductance of the odd and even modes are regulated to be equal, and the isolation is thus significantly improved when compared with the traditional ones to be loaded with lumped elements. As for the inverted-F antenna (IFA) pair, enhanced isolation is achieved by changing the bending configuration, coupling gap, and ground length of the antenna. Good agreement between simulated and measured results shows that all these antennas have achieved isolation over 20 dB.
In this paper, a new class of wideband phase shifters on multimode resonator is proposed and developed. Compared with its conventional counterparts, these new phase shifters have a few advantageous ...features such as simple structure, intrinsic wideband characteristic, large phase-shift value, and easy adjustment in phase shift. The phase properties of multimode resonator are at first studied to derive the quantitative relationship between the phase slope and their respective resonant frequencies. On the one hand, a prescribed wideband phase shift can be achieved by adjusting the impedance ratio R z of the multimode resonator and the electrical length of the reference line. On the other hand, the wide operating band can be intrinsically obtained over a frequency range covered by multiple resonant frequencies in the multimode resonator. In this context, the transmission-line models of the proposed phase shifters are deduced and synthesized to design these phase shifters with a prescribed phase shift value and return loss within the operating band. Moreover, the synthesized model can be directly mapped into all the physical dimensions, thus allowing for a quick design process. Finally, two 180° wideband phase shifters are designed, fabricated, and tested to verify the proposed design method and predicted frequency responses.
A wideband circularly polarised patch antenna with multi-section λ/4 transmission lines is proposed. The multi-section lines are directly connected to the patch radiator. The feeding circuit and ...patch are on the same layer, which makes it easy for integration. There is no coupling structure, and consequently, the parasitic radiation from the feeding circuit can be minimised. The whole antenna structure is designed according to the traditional filter design theory. Two minima in the axial ratio response come up to achieve wideband characteristic. Finally, the proposed antenna structure and wideband performances are experimentally verified by an antenna prototype.
SIW is considered as an effective rectangular waveguide with periodically loaded vias on its two side walls instead of vertical plates. Effective wave impedances of substrate integrated waveguide ...(SIW) with varied via-to-via spacings are for the first time numerically de-embedded from three-dimensional (3-D) full-wave algorithm by virtue of a short-open-load (SOL) calibration approach. Full-wave simulation is at first conducted to model a finite-cell SIW with two feeding uniform waveguides. Afterwards, three calibration standards are formed and modeled to de-embed the two-port ABCD matrix of the finite-cell SIW section. In addition to propagation constant, effective wave impedance of the SIW can be accurately derived without any prior assumption. After numerical convergence versus unit cells is studied, these parameters are gained to give the complete view on guided-wave characteristics along the SIW.
PDF
