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A low-profile circularly-polarized sequential rotation fed 4x4 array antenna working in the Ka-band from 27.5 GHz to 31 GHz is presented. The particularity of the antenna lies in its single-layer sequential rotation feed network implemented in a bed of nails using a combination of groove and ridge gap waveguides. The basic radiating element is one slot loaded by a simple coffee-bean-shaped parasitic element on top. Experimental results show an antenna matching below −10 dB in a 13.6% bandwidth and a measured axial ratio below 1.3 dB in the desired band.

© 2021 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., [EN] This letter presents two slotted array antennas working in the Ka-band with switchable circular polarization capability. The first prototype is a series-fed slotted-waveguide linear array composed of ten T-shaped slots. The second antenna is a 2-D array with 2 x 2 T-shaped slots fed by a corporate distribution network. In both cases, a reflection coefficient below -10 dB has been experimentally observed within the targeted frequency band between 29.5 and 30.5 GHz. Good polarization purity is achieved for both polarization senses and in both prototypes. The fundamental contribution of this letter is to propose a simple mechanism to switch the circular polarization sense in a low-cost, low-profile, and high-efficient antenna. The design and experimental results confirm that the solution is suitable for both one- and two-dimensional arrays in the millimeter-wave band.

[EN] Waveguide slot arrays are a widely used solution to attain linearly polarized high-gain antennas. In this article, an all-metal T-shaped radiating element is conceived with the aim to replace the usual rectangular slots and attain circularly polarized arrays, preserving their good properties. The polarization conversion is made possible due to the inclusion of a parasitic arm perpendicular to the main active slot. Due to the fact that this second arm is not directly fed by the waveguide but coupled to the active slot, the T-shaped element can be used in any array originally formed by metallic rectangular slots. The design of resonant shunt arrays has been addressed here for validation purposes. The experimental results of two sample linear arrays at 30 GHz demonstrate the design accuracy and manufacturing reliability, reporting an axial ratio below 2 dB within a bandwidth of 1.9 GHz and a peak efficiency around 98%.

[EN] In this paper, the capabilities of Selective Laser Sintering metal 3D-Printing technology to achieve a lightweight and cost-effective flat panel antenna in the millimeter wave band are studied. Specifically, two identical dual-band 4 x 4 array antennas working in the K and Ka bands have been manufactured; one with Selective Laser Sintering (SLS) and one using computer numerical control (CNC). Measured performance of the SLS antenna prototype is benchmarked with the performance of the previously measured CNC antenna. Experimental results reveal the strengths and weaknesses of this particular low-cost additive manufacturing technique with respect to traditional subtractive manufacturing techniques.

In this communication, a half-mode waveguide based on Gap Waveguide technology for rapid prototyping is presented. A power divider is designed for demostration purposes. The power divider is constructed from two non-contacting metal pieces. The horizontally-polarized power divider is housed in the bottom piece. The height of the groove is about half that which would be required to propagate the fundamental mode. The top cover is a uniform pinned surface that acts as a High Impedance Surface (HIS) over the groove of the bottom plate. The simulated reflection coefficient shows values of less than −15 dB in the bandwidth of interest (28 to 31 GHz). This design stands out for its ease of fabrication and opens a horizon for cheaper and more robust GW designs for mass production.

Waveguide slot arrays are a widely used solution to attain linearly-polarized high-gain antennas. In this paper, an all-metal T-shaped radiating element is conceived with the aim to replace the usual rectangular slots and attain circularly-polarized arrays, preserving their good properties. The polarization conversion is made possible thanks to the inclusion of a parasitic arm perpendicular to the main active slot. Due to the fact that this second arm is not directly fed by the waveguide but coupled to the active slot, the T-shaped element can be used in any array originally formed by metallic rectangular slots. The design of resonant shunt arrays has been addressed here for validation purposes. The experimental results of two sample linear arrays at 30 GHz demonstrate the design accuracy and manufacturing reliability, reporting an axial ratio below 2 dB within a bandwidth of 1.9 GHz and a peak efficiency around 98%.

In this paper, the capabilities of Selective Laser Sintering metal 3D-Printing technology to achieve a lightweight and cost-effective flat panel antenna in the millimeter wave band are studied. Specifically, two identical dual-band 4×4 array antennas working in the K and Ka bands have been manufactured; one with Selective Laser Sintering (SLS) and one using computer numerical control (CNC). Measured performance of the SLS antenna prototype is benchmarked with the performance of the previously measured CNC antenna. Experimental results reveal the strengths and weaknesses of this particular low-cost additive manufacturing technique with respect to traditional subtractive manufacturing techniques.

[EN] In this conference contribution, we present millimeter-wave (mmWave) propagation measurements for an office environment from 25 to 40 GHz and investigate the path loss using the most common empirical models proposed in WINNER-II and adopted by the 3GPP: the single-frequency floating-intercept (FI) model, the single-frequency close-in (CI) free space reference distance model, the multi-frequency alphabeta-gamma (ABG) model and the close-in free space reference distance with frequency path loss exponent (CIF). Both line-ofsight (LOS) and obstructed-LOS (OLOS) propagation conditions have been considered. The mean value of the model parameters, and their 95 % confidence intervals, have been derived using regression and optimization techniques.

[EN] In this work, an analysis of the Rician K-factor in a laboratory environment from 25 to 40 GHz has been carried out. The variation of the estimated K-factor has been assessed in frequency from a channel measurements campaign in both line-of-sight (LOS) and non-LOS (NLOS) conditions. Mean values of the K-factor ranging from 0.48 to 3.43 dB for LOS conditions, and from -5.54 to -0.56 dB for NLOS conditions, have been derived. The results reported here enable us to get insight into the propagation channel characteristics and can be of interest to evaluate the performance of fifth-generation (5G) networks in laboratory environments.

[ES] Se presenta una guia de onda ranurada con polarizacion dual circular y alimentada por una guia de onda Groove Gap (GGW) y que funciona en la banda Ka. Se propone un mecanismo simple para cambiar la polarizacion circular a ¿ derechas por circular a izquierdas, y viceversa. La tapa de la antena tiene dos piezas: una fija y otra deslizante. La pieza fija alberga ranuras en forma de T, y el bloque deslizante se encarga de ajustar el desplazamiento de las ranuras perpendiculares con respecto a las ranuras longitudinales. Los resultados preliminares muestran una relacion axial por debajo de 1.5 dB para ambos ¿ sentidos de polarizacion circular, dentro de un ancho de banda ¿ de 1 GHz centrado en 30 GHz.

[EN] In this contribution, we present a method for estimating the optimal size of moving average filter to ensure a precise separation of small and large scale fading effects. The analysis of small and large scale fading of the Vehicle-to-Vehicle (V2V) measured channel has been performed from narrowband channel measurements carried out in an urban environment at 5.9 GHz. Uniform intervals, where the channel process can be considered stationary, have been identified by comparing the cumulative distribution function (CDF) of the received envelope. A relationship between the length of the uniform intervals and the velocity of vehicles has been found. Moreover, the Rice K factor has been estimated for each one of these intervals. Our results showed that the proposed method is adequate to carry out a small and large scale fading separation. The results obtained make its use interesting to process correctly measured data in vehicular environments.

[EN] A novel fully metallic Ka-band dual circularly polarized antenna array is presented in this contribution. It consists of 64 circular apertures (8x8) and it is implemented in gap waveguide technology. The antenna includes 4 layers, which are completely metallic, leading to a highly efficient performance. The experimental results confirm reflection coefficient values lower than -10 dB from 29 GHz to 31 GHz as well as stable radiation patterns throughout the whole frequency range. Good average axial ratio (AR) of 1.5 dB has been measured in the working band for both polarizations. Measured directivity is 28 dBi and antenna efficiency keeps close to 80%.

Se presenta una guía de onda ranurada con polarización dual circular y alimentada por una guía de onda Groove Gap (GGW) y que funciona en la banda Ka. Se propone un mecanismo simple para cambiar la polarización circular a derechas por circular a izquierdas, y viceversa. La tapa de la antena tiene dos piezas: una fija y otra deslizante. La pieza fija alberga ranuras en forma de T, y el bloque deslizante se encarga de ajustar el desplazamiento de las ranuras perpendiculares con respecto a las ranuras longitudinales. Los resultados preliminares muestran una relación axial por debajo de 1.5 dB para ambos sentidos de polarización circular, dentro de un ancho de banda de 1 GHz centrado en 30 GHz.

A novel fully metallic Ka-band dual circularly polarized antenna array is presented in this contribution. It consists of 64 circular apertures (8x8) and it is implemented in gap waveguide technology. The antenna includes 4 layers, which are completely metallic, leading to a highly efficient performance. The experimental results confirm reflection coefficient values lower than −10 dB from 29 GHz to 31 GHz as well as stable radiation patterns throughout the whole frequency range. Good average axial ratio (AR) of 1.5 dB has been measured in the working band for both polarizations. Measured directivity is 28 dBi and antenna efficiency keeps close to 80%.

[EN] In this paper, we propose a compact topology for high-frequency bandpass filters using coaxial cavities embedded in a bed of nails, including a complete design procedure combining equivalent circuit models and full-wave simulators. The resonance generated around a shortened cylindrical nail of the bed hosting structure is used as the basic element of the proposed filter, which is fed through groove gap waveguides. For design purposes, an equivalent circuit model of the considered resonance is first obtained, and then the coupling levels between resonators are recovered with the distance between adjacent shortened nails. In order to validate the proposed structure and its design procedure, a filter prototype with a bandpass response (centered at 30 GHz and with relative bandwidth of 1.7%) has been designed, manufactured, and measured. Good experimental results, in terms of insertion losses (with a minimum value of 1.6 dB) and return losses (greater than 16.6 dB in the whole passband), have been achieved.

© 2019 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., [EN] This letter presents an 8 x 8 dual-band shared-aperture array antenna operating in K-(19.5-21.5 GHz) and Ka-band (29-31 GHz) using gap waveguide technology. Radiating elements consist of circular apertures located on the top plate of the antenna and excited by two stacked cavities with different diameters for dual-frequency operation. A waffle grid is used on top to increase the effective area of apertures and reduce grating lobes. Each stacked cavity is fed by its appropriate corporate-feeding net-work: The upper feeding layer operates at 20 GHz band, and the lower one at 30 GHz band. As a result, the antenna presents two ports, one for each band, which radiate a directive far-field pattern with linear polarization, orthogonal to each other. Experimental results show impedance and radiation pattern bandwidths larger than 1.5 GHz in both bands.

[EN] This paper describes an 8 x 8 fully metallic high-efficiency dual-polarized array antenna working at the Ka-band, based on the gap waveguide (GW) concept. The radiating element is a circular aperture backed by two stacked cylindrical cavities, which are orthogonally fed to achieve a dual-polarized performance. Both feeding layers consist of a GW corporate network to reach all the cavities backing each radiating element. Cavities are naturally integrated within the bed of nails hosting grooves and ridges for the guiding electromagnetic (EM) field, leading to a low-profile dual-polarized array in the Ka-band. The experimental results present good agreement with simulations. The measured radiation patterns agree well with the simulation and the antenna provides an average gain over 27 dBi within its operating bandwidth (29.5-31 GHz).

This paper reports the design and measurements of two radiating panels (TX / RX) for satellite communications on the move in Ka-band. A multilayer structure, both in the power distribution network and in the circularly-polarized radiating element, is adopted to ensure the demanded bandwidth. These panels provide answers and solve problems for future antennas with similar characteristics.

This letter presents an 8 × 8 dual-band shared-aperture array antenna operating in K-(19.5-21.5 GHz) and Ka-band (29-31 GHz) using gap waveguide technology. Radiating elements consist of circular apertures located on the top plate of the antenna and excited by two stacked cavities with different diameters for dual-frequency operation. A waffle grid is used on top to increase the effective area of apertures and reduce grating lobes. Each stacked cavity is fed by its appropriate corporate-feeding network: The upper feeding layer operates at 20 GHz band, and the lower one at 30 GHz band. As a result, the antenna presents two ports, one for each band, which radiate a directive far-field pattern with linear polarization, orthogonal to each other. Experimental results show impedance and radiation pattern bandwidths larger than 1.5 GHz in both bands.

This paper describes an 8 × 8 fully metallic highefficiency dual-polarized array antenna working at the Ka-band, based on the gap waveguide (GW) concept. The radiating element is a circular aperture backed by two stacked cylindrical cavities, which are orthogonally fed to achieve a dual-polarized performance. Both feeding layers consist of a GW corporate network to reach all the cavities backing each radiating element. Cavities are naturally integrated within the bed of nails hosting grooves and ridges for the guiding electromagnetic (EM) field, leading to a low-profile dual-polarized array in the Ka-band. The experimental results present good agreement with simulations. The measured radiation patterns agree well with the simulation and the antenna provides an average gain over 27 dBi within its operating bandwidth (29.5-31 GHz).

In this paper, we propose a compact topology for high-frequency bandpass filters using coaxial cavities embedded in a bed of nails, including a complete design procedure combining equivalent circuit models and full-wave simulators. The resonance generated around a shortened cylindrical nail of the bed hosting structure is used as the basic element of the proposed filter, which is fed through groove gap waveguides. For design purposes, an equivalent circuit model of the considered resonance is first obtained, and then the coupling levels between resonators are recovered with the distance between adjacent shortened nails. In order to validate the proposed structure and its design procedure, a filter prototype with a bandpass response (centered at 30 GHz and with relative bandwidth of 1.7%) has been designed, manufactured, and measured. Good experimental results, in terms of insertion losses (with a minimum value of 1.6 dB) and return losses (greater than 16.6 dB in the whole passband), have been achieved.

(c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this, [EN] Achieving a functional antenna for mobile satellite communications terminals in Ka-band is probably one of the most challenging tasks in current antenna engineering, particularly bearing in mind they need to be low profile and "affordable." This quest is involving many companies in the field. Our contribution represents one of such efforts. The antenna is based on a slotted waveguide array technology to maximize efficiency and it features a number of novel solutions, going from its robust polarization switching mechanism, to the use of a thin wideband polarizer and the utilization of groove gap waveguides. This communication reports the measured data of a fully functional prototype to validate its novel contributions.

This letter focuses on comparing manufacturing features of three-dimensional (3-D) printing techniques versus conventional computer numerical control (CNC) milling in the context of gap waveguide technology. To this end, a single-layer array antenna has been designed as a demonstrator. The antenna under test, intended for Ka-band, is composed of 8 × 8 radiators fed by a gap-waveguide (GW) corporate network. Two identical prototypes have been manufactured, but each applying a different fabrication technique, i.e., 3-D printing and CNC milling. The experimental results of both antennas are presented, under the same conditions and measurement facilities. The conclusions drawn in this letter provide a valuable assessment of 3-D-printing viability for GW arrays against the conventional milling technique.

Achieving a functional antenna for mobile satellite communications terminals in Ka-band is probably one of the most challenging tasks in current antenna engineering, particularly bearing in mind they need to be low profile and “affordable.” This quest is involving many companies in the field. Our contribution represents one of such efforts. The antenna is based on a slotted waveguide array technology to maximize efficiency and it features a number of novel solutions, going from its robust polarization switching mechanism, to the use of a thin wideband polarizer and the utilization of groove gap waveguides. This communication reports the measured data of a fully functional prototype to validate its novel contributions.

(c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works., [EN] This letter focuses on comparing manufacturing features of three-dimensional (3-D) printing techniques versus conventional computer numerical control (CNC) milling in the context of gap waveguide technology. To this end, a single-layer array antenna has been designed as a demonstrator. The antenna under test, intended for Ka-band, is composed of 8 x 8 radiators fed by a gap-waveguide (GW) corporate network. Two identical prototypes have been manufactured, but each applying a different fabrication technique, i.e., 3-D printing and CNC milling. The experimental results of both antennas are presented, under the same conditions and measurement facilities. The conclusions drawn in this letter provide a valuable assessment of 3-D-printing viability for GW arrays against the conventional milling technique.

A comparative study between groove gap waveguide (GGW) technology and classical H-plane rectangular waveguide (RWG) technology is presented by evaluating their performance in the implementation of a narrow-band filter at the V-band. A filter with the same specifications has been manufactured and measured for each technology. Measured responses are compared and a re-assembling robustness test is carried out. The GGW filter presents a better response and remains completely invariant to the re-assembling process, which is shown to affect notably the RWG filter response. Remarkable low insertion loss of only 1.5 dB (cavities equivalent quality factor higher than 800) is obtained for the GGW filter.