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A modified folded-waveguide (FW) delay line for traveling-wave tubes (TWTs) is proposed. The amplifier performance is assessed by full-wave and interaction simulation. Properly designed nose cones are shown to enhance the beam-wave coupling. This, in turn, improves the amplifier gain, a weak point of conventional FW-TWTs. The achievable beam efficiency is increased without sacrificing too much bandwidth.

On-line calibration systems with near-field probes are an attractive approach for large-size DBF arrays. In order to improve the calibration accuracy, a model of the coupling between the receiver patch and the calibration monopole probe is developed further in this contribution. A Fourier-based approximation of the radiation characteristic of the patch is proposed as a compromise between accuracy and computational effort. A planar array is built to validate the proposed concept. A phase error of 1.5° and an amplitude deviation of 0.8 dB are achieved in the experiments.

The ongoing developments of satellite antenna technology, mainly of multiple-feed-per-beam (MFB) concepts, combined with advanced compound semiconductor and packaging technologies that provide the building blocks for a new generation of K-band satellites, are reported. This paper proposes a next-generation MFB application scenario using the advantages of both new antenna and solid-state power amplifier concepts.

A stepped transition in substrate-integrated waveguide (SIW) technology is presented. The transition changes the height of an SIW using multiple steps. The steps can be tuned by varying the length of shorted stubs which represents a generalization of a stepped-impedance transformer. An accurate equivalent circuit model of the steps is developed, that enables fast optimization. An exemplary transition is designed that features two frequency bands at 20 GHz and 30 GHz. For verification the model is compared to full-wave simulation and a back-to-back coplanar-waveguide (CPW) to full-height SIW transition is fabricated and measured.

A design procedure for a hot-matched sever for folded-waveguide traveling-wave tubes (FW-TWTs) is proposed. To determine a starting point for a suitable load design, a realistic three-dimensional sever structure is developed using equivalent circuits and subsequent particle-free (cold) full-wave simulation. Additional wave impedance information, obtained by a small-signal eigenvalue analysis, is used to improve the termination for hot operation. The final full-wave optimization is then performed in the presence of the electron beam with only moderate computational effort. This procedure is applied to develop a sever structure for a given frequency point at Q-band. The simulated results support the approach.

In this work barium hexaferrite films for self-biased nonreciprocal devices are produced by means of the sol-gel method. The effect of the drying temperature on the film surface is examined via scanning electron microscopy. The influence of the crystallization temperature and the composition of the precursors on secondary phases is analyzed via X-ray diffraction analysis. Measurements of a coplanar waveguide with a barium hexaferrite thin-film show nonreciprocal behavior at the ferromagnetic resonant frequency in the Q-band without external biasing field.

This paper discusses antenna array integration concepts for combined receiver (Rx) and transmitter (Tx) terminals that can be used for ground based Ka-band satellite communications (SatCom). The combination of Rx and Tx enables very compact array architectures, which eases integration on mobile platforms. The associated challenges are discussed in the SatCom context and a comprehensive analysis of the array grids is carried out. Advanced dual-band antenna designs are presented for both tile and brick architecture. A dielectric-lens based wideband antenna is introduced as an element of a dual-band array in brick architecture. The approach eases the integration of the required passive and active circuitry.