# Worldwide Coverage Mobile Systems for
## 4 Ku-Band Antennas Design Techniques
### Combining Devices for Antenna Arrays  
Grouping a set of antennas, commonly known as antenna array, is a common strategy to increase the overall antenna gain and properly shape the radiation pattern. Array antennas can be implemented while using various basic antenna elements, such as patches, slots, monopoles, dipoles, horns etc. [17, 18]. To meet the requirements regarding gain and radiation/reception pattern, the amplitude and phase of the signals that are fed into each basic element are modified to achieve the expected radiation pattern, including main lobe(s) pointing angle, width (aperture), gain, etc.  
There is an increasing demand for satellite communications with world-wide coverage and spreading the satellite frequency band is requested. The C band use is at the limits and, in consequence, the demand for communications in the Ku band is augmenting progressively because of the possibility of using wider bandwidths. It is also well known that some communication satellites operate simultaneously in both C and Ku bands, offering a better service. In consequence, appropriate design techniques and proper technologies must be developed to operate at the same time at both bands and, specifically, appropriate antennas approaches must be addressed for C and Ku simultaneous communications while analysing the particular disturbances affecting each band [8].  
In [19] the authors propose, introduce and analyse a six-port junction based on the SIW (Substrate Integrated Waveguide) technology. To achieve the design constraints, the authors convert the SIW element into an equivalent waveguide with a rectangular profile in order to apply conventional design techniques for such waveguides. The junction can be applied for different purposes. Based on that simple device, the authors face the design of two SIW basic components: a 3 dB hybrid coupler and a divider. Afterwards, these components are used to design the six-port junction circuit working in the frequency band at 24 GHz. Subsequently, it was implemented and measured to corroborate the results obtained in the simulation phase. It was found that the six-port junction introduced in this paper fits the requirements. This element can be used in the construction of arrays of planar antennas.  
In [11], the authors introduce the design of a \(4\times 4\) Nolen matrix which could be used in the implementation of devices and systems based on multi-layer SIW techniques. This technology could lead to the implementation of a beamforming network topology with compact size factor. Specifically, the authors introduce a new broadband coupler based on two-layers SIW technology. It is worthy to remark the features of the designed device. The coupler shows a wide dynamic range within a considerable bandwidth, i.e., about 12 GHz in the Ku band. Among other beamforming structures where the component could be used (e.g., Butler matrices), the authors propose its use for the implementation of matrices aimed at multiple beamforming. Additionally, the authors introduce the design of a low-losses two-layers waveguide transition based on multiple layers topology SIW technology. The results obtained in this investigation could be extended to larger structures, e.g., a \(4\times 4\) Nolen matrix.  
In [20], the authors analyse the design and implementation of via and aperture transition structures aimed at interconnecting three-dimensional (3-D) integration of substrate integrated waveguides. The methodology used is based on the description of electrical equivalent circuits to develop a parametric analysis to discuss the error met as compared to full-wave simulations. Furthermore, the achieved models for both via and aperture transitions are implemented and measured to validate the results.