David Canete-Rebenaque

Design of Bandpass Transversal Filters Employing a Novel Hybrid Structure

A novel structure for the implementation of compact transversal bandpass filters is proposed in this paper. This new proposal consists of a hybrid structure, based on the combination of two different technologies: the waveguide and microstrip. It is shown that the novel hybrid microwave filter is able to implement both a second- and third-order filtering function with up to two or three transmission zeros, respectively. In this way, a practical implementation of a fully canonical transversal filter with a third degree response is for the first time directly achieved. In addition, the way to control the positions of transmission zeros with the new technology is treated in this paper. It is shown that symmetric or asymmetric responses and also filtering functions with a complex pair of transmission zeros can be easily obtained. To demonstrate the validity of this novel structure, several implementation examples are presented. A prototype has been designed, manufactured, and successfully tested, showing the practical validity of the new structure.

Printed-circuit leaky-wave antenna with pointing and illumination flexibility

A novel leaky-wave antenna, based on a periodic set of slots printed on a rectangular dielectric waveguide is conceived in this work. The antenna presents the ability to independently control the aperture illumination and the pointing direction, by only modifying the photoetched printed-circuit layout. The working mechanism is described using a leaky-mode dispersion analysis, and cosine-tapered designs are performed at 50 GHz. The radiation patterns are obtained using HFSS analysis to check the reduction of sidelobes levels, and the capacity to tune the pointing direction over a wide range of elevation angles.

Design of Dual-Bandpass Hybrid Waveguide–Microstrip Microwave Filters

A simple dual-bandpass filtering structure is proposed. The filter is implemented by means of a new hybrid waveguide-microstrip technology. The novelty of the structure is that it combines two standard printed microstrip coupled line resonators, with a resonance of the base waveguide cavity, to implement a dual-band operation. Important aspects about the filter design, useful for practical applications are treated. This includes a study on the maximum coupling that can be achieved to the cavity resonance, and guidelines to control the positions of the two passbands and the transmission zeros. Besides, an example has been designed, manufactured and tested. The measurements on the fabricated prototype have confirmed the validity of the new structure to perform dual-band operation.

Design of a Bandpass Transversal Filter Employing a Novel Hybrid Waveguide-Printed Structure

This paper introduces a novel hybrid structure to implement a bandpass transversal filter based on the combination of two well known technologies. The structure combines for the first time the waveguide and the microstrip technologies for the design of transversal filters with maximum selectivity. By combining these technologies, very compact structures are obtained to implement the so called modified doublet. One of the resonators of the doublet is formed with the TM111 mode of a waveguide cavity, while the second resonator is implemented using a standard printed line microstrip resonator. It is shown that all the parameters of the N + 2 coupling matrix can be controlled by means of the dimensions of the proposed structure. Results validate the novel structure, and show how a second order filtering function of a specific coupling matrix can be easily synthesized.

Novel and simple technique to control the polarization in stub-loaded leaky-wave antennas

Leaky-wave antennas (LWAs) are commonly used to synthesize narrow-beam frequency-scanning radiation patterns by means of a single line-source. By properly controlling the leaky-mode propagation constant, one can flexibly design the pointing direction and the sidelobes distribution. Many studies have been performed in the last years to conceive LWAs that also have polarization flexibility, and particularly to obtain circular polarization. For this purpose, periodic arrays of slots or strips have been added to a host waveguide to induce radiation in the desired polarization. In all these LWA designs, the polarization was controlled by choosing the orientation and dimensions of the periodic perturbations. Normally, complicated orthogonal arrangements of the periodic arrays are needed to obtain circular polarization. In addition, radial waveguides and microstrip lines have also been proposed to obtain vertical and horizontal polarization at the same time, and eventually achieve a circularly polarized main beam. In this contribution, we present a totally original mechanism that allows to control the polarization of the radiated fields in stub- loaded LWAs. The proposed mechanism does not need the introduction of periodic perturbations orthogonally arranged, neither the modification of the host waveguide to obtain a radial shape. As it will be shown, a uniform LWA can be used to excite and control the horizontal and vertical components of the radiated fields.

Use of ground planes within the spatial images technique: Application to the analysis of rectangular multilayered shielded enclosures

The use of ground planes is proposed inside the spatial images technique in order to calculate the multilayered shielded Greens functions for rectangular enclosures. The positions of the ground planes are dynamically located, covering two walls of the cavity, as a function of the source position. Spatial mirror images, related to the ground planes, are used to perfectly impose the boundary conditions along these cavity walls. This completely removes the problems associated to the singular behavior of the source when it is placed close to a wall or a corner, improving numerical stability. In addition, the method leads to a very efficient computation (about 15 times faster than the original approach), due to the reduced number of non-mirror images that must be effectively computed. A multi-band filter in hybrid waveguide-microstrip technology is analyzed with the new method, showing excellent agreement with measured data.

Simple and accurate transverse equivalent network to model radiation from hybrid leaky-wave antennas with control of the polarization

A novel technique to control the polarization in stub-loaded leaky-wave antennas was first proposed in [1], and lately studied in more detail in [2]. The cross section of the antenna, based on hybrid waveguide-planar technology [3], is shown in Fig.1-a. In [1,2], it was shown how this technology allows to obtain horizontal, vertical, elliptical and circular polarizations. However, the designs presented in [1,2] were performed using three dimensional electromagnetic simulations obtained from commercial finite element solver (HFSS). These designs were also validated with experiments in [2]. In this paper we present a novel transverse equivalent network (TEN) to analyze in a more efficient way the behavior of the proposed leaky-wave antenna (LWA).

Reducing the beam squint in scanned leaky-wave antennas using coupled SIW cavities

The systematic design of broadband, directive, scanned planar leaky-wave antennas using coupled-cavity substrate integrated waveguide technology is reported in this work. The design methodology is based on the optimization of the corresponding transverse resonance phase equation, so that a constant scanning angle condition is satisfied for a wide frequency band. This design process is validated with full-wave simulations of a 4th order-cavity optimized design. A 3dB scanned pattern bandwidth of 1.5GHz with 10dBi directivity at a central frequency of 15GHz (10% fractional bandwidth), is reported for 30° elevation scanning angle. This is a much higher bandwidth than conventional 1.7% bandwidth associated to the same type of antenna with a single SIW cavity.

Development of a small Radio Telescope at the Technical University of Cartagena: A duty with our students and society

An initiative carried out at the Technical University of Cartagena (UPCT, Spain) to encourage students and promote the interest for Scientific and Engineering Culture between society is presented in this contribution. For this purpose, a medium-term (4 years) project based on the design, fabrication, testing and setup of a small Radio Telescope system has been carried out. The main novelty is that this project is entirely being done by students of last courses of our Telecommunication Engineering Faculty, under the supervision of four lecturers.

Novel Broadside Trisection Filters Employing Nonresonating Nodes

This work presents novel filter topologies implemented in microstrip technology. The topologies combine printed line resonators with non resonating nodes (NRN) to implement transmission zeros in a very flexible way. Depending on the number of resonators and NRN, the filtering response exhibits a single transmission zero either below or above the passband, or two transmission zeros, one at each side of the passband. Several examples are designed and validated, using the new proposed structures.