Multiple Order Dual-Band Active Ring Filters with Composite Right/Left Handed Cells

In this paper, a novel dual-band active filter topology is presented. The non-linear phase response of a composite right/left-handed cell is used to achieve the desired dual-band performance. Additionally, the proposed structure based on coupled ring resonators yields a very compact solution in which high-order implementations can be easily obtained by cascading multiple rings. The theoretical principles of this type of filters are analyzed in detail. Finally, three prototypes based on first-, second- and third-order structures validate the feasibility of this type of filters. Good agreement between simulations and measurements has been achieved

Noise Figure Measurement of Differential Amplifiers Using non-Ideal Baluns

This paper analyzes the noise and gain measurement of microwave differential amplifiers using two passive baluns. A general model of the baluns is considered, including potential losses and phase/amplitude unbalances. This analysis allows de-embedding the actual gain and noise performance of the isolated amplifier by using single-ended measurements of the cascaded system and baluns. Finally, measured results from two amplifier prototypes are used to validate the theoretical principles

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

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

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

Amorphous topological matter: theory and experiment

Topological phases of matter are ubiquitous in crystals, but less is known about their existence in amorphous systems, that lack long-range order. In this perspective, we review the recent progress made on theoretically defining amorphous topological phases and the new phenomenology that they can open. We revisit key experiments suggesting that amorphous topological phases exist in both solid-state and synthetic amorphous systems. We finish by discussing the open questions in the field, that promises to significantly enlarge the set of materials and synthetic systems benefiting from the robustness of topological matter.Comment: This is an extended version of the article accepted in EP

Dipolos impresos multifrecuencia cargados con partículas metamateriales

Multi-frequency printed dipoles based on antipodal printed dipoles loaded with metamaterial particles are presented. Split Ring Resonators (SRRs) are used as metamaterial particles in order to obtain fully printed and planar antennas. First, a simplified model of these antennas is developed. This model is based on a printed dipole loaded with the equivalent circuit of the SRRs. This model shows that the working frequencies are very close to the self-resonant frequencies of the dipole and the SRRs. Moreover, a dualfrequency printed dipole is designed, manufactured and measured. This dipole works simultaneously at 1.32 GHz and 2.82 GHz. Finally, the previous idea is extended to increase the bandwidth of the dual-band dipoles and develop multifrequency printed dipoles (printed dipoles which work simultaneously at three or more frequencies). This is made by using SRRs with different dimensions