Abstract-In this paper, a novel approach to design multifrequency self-diplexed single patch antennas is proposed. This approach is based on a square microstrip patch antenna loaded with split ring resonators (SRRs). The working frequencies can be arbitrarily chosen and frequency ratios lower than 1.07 have been achieved. In addition self-diplexing characteristics are also achieved between transmitting and receiving ports by including SRRs in the feeding lines. Several prototypes have been manufactured and measured in the X-band showing good performance.
Abstract-In this paper, the most adequate architecture to implement dual frequency amplifiers is shown. Composite Right/Left Hand (CRLH) and Extended Composite Right/Left Hand (ECRLH) transmission lines are studied and evaluated to find the most suitable structure for dual band power amplifiers. As an example, the performance of a class CE amplifier, working in TETRA and GSM frequency bands, is compared with simulations and measurement, showing good agreement.
INTRODUCTIONThe increasing demand for wireless systems requires the use of higher frequency spectrum. Such high frequencies entail two major drawbacks: First, line transmission losses increase significantly. And second, solid state devices present power limitations at radio frequency (RF). Besides, when high RF power is demanded, there are some problems related with conventional system design and implementation, which can be overcome combining several RF devices to achieve the desired level. Another problem arises from the need of multifunction transponders to cope with several services, usually allocated at different frequencies, in the only terminal, being a well known example multiband or even GPS mobile phones. As a result of all these drawbacks, the development and use of multi-frequency highperformance power amplifiers is required. In this paper, TETRA Corresponding author: V. Gonzalez-Posadas (vgonzalz@diac.upm.es).
Abstract-The results of a parametric study and design of an ultra-wideband dual-polarized array of differentially fed Tapered Slot Antenna elements are presented. We examine arrays of bunny-ear antennas and discuss the capabilities and limitations of differential antenna technology. As we focus on radio astronomical applications, the absence of a balancing-feed circuit not only reduces the first-stage noise contribution associated to losses in the feed, but also leads to a cost reduction. Commonmodes are supported by the antenna structure when a third conductor is present, such as a ground plane. We demonstrate that anomalies may occur in the differential-mode scan impedance. Knowledge of both types of scan impedances, differential and common mode, is required to properly design differential LNAs and to achieve optimal receiver sensitivity. A compromise solution is proposed based on the partial suppression of the undesired common-mode currents through a (low loss) balancing-dissipation technique. A fully steerable design up to 45º in both principal planes is achieved.
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