A novel class of Butler matrix with inherent bandpass filter (BPF) transfer functions is presented in this paper. The Butler matrix is the fundamental network to split and recombine the signal in multi-port power amplifiers, however, to suppress spurious frequencies generated by the amplifiers or to provide nearband rejection in order not to interfere with other transmission/receiving bands separate filtering is often required. Here, the traditional power division and phase distribution of the Butler matrix are included together with filtering selectivity into one single device based only on coupled resonators. An analytical synthesis procedure of the coupling matrix for 2 2 networks is presented here for the first time. The proposed solution has shown significant advantages in terms of size reduction compared to the traditional baseline consisting of a distribution network plus a bank of BPFs. The synthesis and design of a 2 2, 180 hybrid coupler at 10 GHz and a 4 4 Butler matrix with an equal-ripple four-pole Chebyshev bandpass characteristic centred at 12.5 GHz with 500-MHz bandwidth are described, confirming the synthesis technique proposed. Two models of the 4 4, one built with additive manufacturing and the other with milling, are also presented and compared. Experimental measurements are in good agreement with both simulations and theoretical expectations.Index Terms-Bandpass filters (BPFs), Butler matrix, circuit synthesis, multi-port power amplifier (MPA), power distribution.
In this paper, a new topology for rectangular waveguide band-pass and low-pass filters is presented. A simple, accurate and robust design technique for these novel meandered waveguide filters is provided. The proposed filters employ a concatenation of ±90º E-plane mitered bends (±90ºEMBs) with different heights and lengths whose dimensions are consecutively and independently calculated. Each ±90ºEMB satisfies a local target reflection coefficient along the device so that they can be calculated separately. The novel structures allow to drastically reduce the total length of the filters and to embed bends if desired, or even to provide routing capabilities. Furthermore, the new meandered topology allows the introduction of transmission zeros above the passband of the low-pass filter, which can be controlled by the free parameters of the ±90ºEMBs. A band-pass and a low-pass filter with meandered topology have been designed following the proposed novel technique. Measurements of the manufactured prototypes are also included to validate the novel topology and design technique, achieving excellent agreement with the simulated results.
This article investigates the potential of additive manufacturing for the fabrication of complex antenna geometries with enhanced performance at K-band. Stereolithography is here used to 3D-print a novel topology of dual-polarized leaky-wave antenna that allows for the control of its aperture illumination both in phase and magnitude. The antenna consists of a modulated triple-ridge square waveguide perforated on its top wall with crossed slots of different sizes. An orthomodetransducer is integrated within the structure for dual-mode operation. Monolithic implementation of this compound threedimensional structure is only possible thanks to additive manufacturing. In addition, low weight and compactness are attained comparing to classical milling. The present proposal is validated through the manufacturing of a low sidelobe levels prototype suitable for intersatellite links. The corresponding measured results are in very good agreement with full-wave predictions.
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