Consideraciones de diseño de adaptación activa para antenas cargadas con circuitos non-Foster

In this paper the use of the NDF is proposed as a general method suitable for analysing any oscillator topology. The most important advantage of this method is that it provides an unique procedure to analyse any oscillator. It also makes possible the phase noise optimization in the linear design phase for any oscillator. An additional advantage of this method is that it does not require any proviso verification as all classic methods need. The use of the NDF method is illustrated with the design of two examples. These two oscillators are manufactured and the simulation results are compared with the measurements showing good agreement. These results confirm the excellent possibilities of the proposed method for low noise oscillators design

Sensitivity analysis for active matched antennas with non-foster elements

During the last years many researchers have been working on the active matching or on non-Foster matching networks for one- and two-port electrically small antennas (ESAs). A new parameter on the sensitivity of the two-port electrically small antenna when loaded with a non-F oster network is presented. This sensitivity analysis will allow us to choose what kind of antennas can be properly matched with non-Foster networks and their position in order to optimi ze the performance of the design. Then, a typical high Q two-port antenna will be harder to match over a broad bandwidth, since |S21| is very small and only agrees with |S11| over very small frequency bands, yielding very large sensitivity values. However, for these two-port antennas, if high levels of coupling can be engineered for a high Q multiple-port antenna, the return and insertion losses can be similar over larger bandwidths and, hence, the sensitivity can be kept low over larger bandwidths, enabling broader impedance matched bandwidths to be achieved, even for highly resonant antennas

Antena de Parche Monopolar de Doble Frecuencia

A dual-frequency patch antenna with monopolar radiation patterns at both working frequencies is presented in this paper. The antenna design is based on a conventional patch with two concentric short-circuited conditions with a separating gap between them. Both shorting conditions are implemented with vias between the patch and the ground plane. These conditions impose two modes with a uniform electric field distribution both in phase and amplitude at the edge of the patch antenna. These modes result in a monopolar radiation pattern at two different frequencies. The working frequencies can be arbitrary set and depend on the patch dimensions and the location of the shorting vias. Two feeding strategies have been studied: a single coaxial probe which excites both monopolar modes and a different coaxial probe for each mode. A two-port design working at 2.6 GHz and 4.8 GHz is presented, obtaining the desired monopolar radiation pattern at both frequencies. High isolation between the feeding ports is achieved

On the performance of negative impedance converters (NICs) to achieve active metametrials

One of the main drawbacks when designing microwave circuits or antennas based on metamaterial particles is its inherent low bandwidth and not very good efficiency. An attempt to overcome this problem is based on using negative impedance converters (NICs). Although the use of NICs have been proposed as a solution to increase the bandwidth of electrically small antennas, they suffer from many problems such as stability performance, bias and the maximum frequency that can be achieved. In addition, the application of NICs has been restricted to low frequency applications in order to avoid the previous problems. This paper makes a study on the performance of NICs for active metamaterial applications. The main contributions of the present paper is that it takes into account the non-linear equivalent circuit of the NICs to find out its performance for active metamaterial applications. From that study it can be concluded that NICs can work up to a few GHz

Meander dipole antenna to increase CW THz photomixing emitted power

The success in conquering the terahertz (THz) gap is subject to some facts such as maximizing the emitted power. Traditionally resonant antenna designs for continuous-wave (CW) THz photomixing include a RF choke to compensate the capacitive part of the photomixer and an antenna with a very high input impedance at its resonance to match the low value of the photomixer conductance. This communication considers that the antenna itself can provide this large impedance margin needed to directly match the photomixer, so that the RF choke can be avoided. The meander antenna constitutes an excellent candidate to achieve that goal based on the Active Integrated Antenna concept to improve both matching and radiation efficiencies. The main objective is to maximize the total efficiency and, as a consequence, the THz emitted power. A prototype working at 1.05 THz is designed and manufactured and results show a 6 dB output power improvement when compared with a conventional log-periodic antenna.This work was supported by Consolider CSD 2008–00068. The work of J. Montero-de-Paz was supported by the Spanish Education Minister under the program FPU (AP2009–4679) . The work of E. Ugarte-Muñoz was supported by the Spanish Economy Minister under the program FPI (BES2010–037676).Publicad

Broadband active differential array for the mid-frequency SKA band

This paper presents the design and characterization process of an active array demonstrator for the mid-frequency range (i.e., 300 MHz-1000 MHz) of the future Square Kilometre Array (SKA) radio telescope. This demonstrator, called FIDA3 (FG-IGN: Fundación General Instituto Geográfico Nacional - Differential Active Antenna Array), is part of the Spanish contribution for the SKA project. The main advantages provided by this design include the use of a dielectric-free structure, and the use of a fully-differential receiver in which differential low-noise amplifiers (LNAs) are directly connected to the balanced tapered-slot antennas (TSAs). First, the radiating structure and the differential low-noise amplifiers were separately designed and measured, obtaining good results (antenna elements with low voltage standing-wave ratios, array scanning capabilities up to 45°, and noise temperatures better than 52 K with low-noise amplifiers at room temperature). The potential problems due to the differential nature of the proposed solution are discussed, so some effective methods to overcome such limitations are proposed. Second, the complete active antenna array receiving system was assembled, and a 1 m2 active antenna array tile was characterized

New device for continuous-wave THz emission: large area emitter

We discuss two different approaches to overcome the power limitations of CW THz generation imposed to conventional photomixers. The increase in power achievable by using arrays of AEs is studied. Then ?large area emitters? are proposed as an alternate approach to overcome the power limitations. In this antenna-free new scheme of photomixing, the THz radiation originates directly from the acceleration of photo-induced charge carriers generated within a large semiconductor area. The quasi-continuous distribution of emitting elements corresponds to a high-density array and results in particularly favorable radiation profiles

From arrays of THz antennas to large-area emitters

Arrays of coherently driven photomixers with antenna (antenna emitter arrays, AEAs) have been evaluated as a possibility to overcome the power limitations of individual conventional photomixers with antenna (?antenna emitters?, AEs) for the generation of continuous-wave (CW) THz radiation. In this paper, ?large area emitters? (LAEs) are proposed as an alternative approach, and compared with AEAs. In this antenna-free new scheme of photomixing, the THz radiation originates directly from the acceleration of photo-induced charge carriers generated within a large semiconductor area. The quasi-continuous distribution of emitting elements corresponds to a high-density array and results in favorable radiation profiles without side lobes. Moreover, the achievable THz power is expected to outnumber even large AEAs. Last not least, the technological challenge of fabricating LAEs appears to be significantly less demanding

Sistema de enfoque basado en dos espejos elípticos y un espejo plano rotatorio para un radar a 300 GHz

A focusing system for a 300 GHz radar with two target distances (5m and 10m) is proposed, having 1cm resolution in both cases. The focusing system is based on a gaussian telescope scheme and it has been designed using gaussian beam quasi-optical propagation theory with a homemade Matlab analysis tool. It has been translated into a real focusing system based on two elliptical mirrors and a plane mirror in order to have scanning capabilities and validated using the commercial antenna software GRAS