A systematic design of dual-band, orthogonallypolarized linear-to-circular polarization (LP-to-CP) converters is proposed. This class of polarization converters can transform linearly-polarized waves into right-and left-hand circularlypolarized (RHCP and LHCP) waves in two separate non-adjacent frequency bands. The reported polarizer is made of three cascaded bianisotropic sheet admittances, spaced by two isotropic dielectric slabs. The electromagnetic problem is studied by means of impedance boundary conditions. A transmission-matrix analysis of periodically-loaded transmission-lines is employed in design. An analytic model is developed and closed-form expressions are derived for the frequency response of each sheet admittance. This method avoids the use of multi-parameter optimization procedures. An example of a dual-band, orthogonally-polarized LP-to-CP converter is proposed for satellite communication applications in the K/Ka-band. The polarizer separately performs LP-to-LHCP and LP-to-RHCP conversions over the transmitting and receiving channels of the K/Ka-band. The design is validated with a prototype. Under normal incidence, the polarizer exhibits axial ratios (ARs) lower than 3 dB over the 18-22.2 GHz (∼21%) and 28.7-30.4 GHz (∼6%) bands. The total transmission is above-1 dB within the same two bands. The performance is stable for scanning angles up to ±45 •. For a 45 • angle of incidence, the AR is lower than 3 dB in the bands 17-22 GHz (∼25.6%) and 28.6-30 GHz (∼4.7%) with a total transmission higher than-1.2 dB.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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This paper presents an efficient analysis method for a novel continuous transverse stub (CTS) antenna. As opposed to state-of-the-art CTS antenna designs, the proposed architecture achieves circular polarization using a single CTS array and without any polarization converter. The structure consists of long radiating slots/stubs fed by over-moded parallel-plate waveguides. More precisely, the transverse electromagnetic (TEM) mode and the first transverse electric (TE1) mode of the feeding waveguides are used to generate a circularly-polarized field. The array is analyzed using a spectral mode-matching method. First, the active reflection coefficient of the infinite array is derived in closed form. A windowing approach is then adopted to compute the radiation patterns of finite-size arrays. Numerical results obtained with this method are in excellent agreement with fullwave simulations, carried out with a commercial software. The performance of this class of CTS antennas has been investigated using the developed model. It is theoretically demonstrated that the proposed array can be designed to attain an axial-ratio (AR) lower than 3 dB over a 52.9% relative bandwidth at broadside. Furthermore, the active input reflection coefficient is lower than-10 dB over a 40.8% relative bandwidth when the array steers its main beam at θ0 = 45 •. This solution is an attractive candidate for next generation satellite communication terminals. Index Terms-Continuous transverse stub array, circular polarization, oversized parallel-plate waveguides.

Modern K/Ka-band satellite communications have become increasingly demanding in recent years with regard to the performance of the terminal antenna used in the link. These terminals should be high-gain and broadband, as well as guarantee polarization diversity over a large field-of-view. A lowprofile is also highly desired to integrate the antenna system into a variety of moving platforms such as aircraft and trains. An ultra-low-profile continuous transverse stub array is proposed here to tackle these challenges. The antenna array is realized in printed circuit board technology by adopting a contactless transition between the stacked-up layers without resorting to blind or buried vias. The proposed antenna is wideband (impedance matched within the band 19-31 GHz, i.e., ∼ 50%) and provides multi-beam radiation for polar angles as far as ±22.5 • . The peak value of the gain is 19.7 dBi and the maximum radiation efficiency equals 50%. Furthermore, the antenna array is combined with a dual-band polarization converter. The latter provides orthogonal circular polarization in two non-adjacent bands. The overall antenna system performs right-and left-hand circular polarization within the SatCom down-and up-links in the K/Ka-band, respectively. For each polarization, the axial ratio is below 3 dB over 9.47% and 4.42% fractional bandwidths, respectively.

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