Benjamin Rohrdantz

Microstrip ring resonator based frequency reconfigurable band-pass filters at K-band

In this contribution two planar microstrip band-pass filters based on closed loop resonators with reconfigurable center frequency are proposed at K-band. Two geometries, a square-ring and a meander loop, are closely investigated. The frequency reconfigurability is achieved by means of PIN diodes. The filters are designed for and fabricated on a standard printed circuit board technology. Dual-mode resonators are used to obtain a compact design suitable for integration into an active antenna frontend. The paper presents the filter design, the tuning range, an analysis of the occurring losses, and the verification through simulation and measurement.

3D-printed low-cost, low-loss microwave components up to 40 GHz

This contribution investigates the manufacturability and the performance of waveguide components fabricated using a consumer-grade 3D printer. This low-cost process enables a fast fabrication of microwave circuits almost directly from a 3D simulation model to a ready-to-use component. Two different components, a simple waveguide and a more complex array with integrated power combiner, are manufactured and characterized to validate the approach.

Rx/Tx integration concepts for ground segment SatCom antenna arrays

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.

Ka-band antenna arrays with dual-frequency and dual-polarized patch elements

In this contribution a dual-band, dual-polarized microstrip antenna element for array applications is presented. The patch antenna is designed to operate simultaneously at around 30 and 20 GHz, the up- and downlink frequencies of modern Ka-band satellite communication systems. The antenna is smaller than half the freespace wavelength at 30 GHz to enable its utilization as array element of dual-band ground terminals. Integrating transmitter and receiver circuits allows, in turn, for a very compact active terminal solution. To minimize production cost, the design is carried out in standard multilayer printed circuit board technology. The antenna features two distinct polarization ports suitable for either dual linear or dual circular polarization if both ports are excited in quadrature. The single antenna design process is described in detail and simulation and measurement results are presented. Finally, different arrays based on this patch antenna are evaluated by simulation and measurements.

Modeling and design of stepped transitions for substrate-integrated waveguides

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 Flexible Surface Description for Arbitrarily Shaped Dielectric Lens Antennas

Abstract A method to efficiently describe arbitrarily shaped dielectric lens antennas based on spherical harmonics is proposed. It makes use of a Fourier-Laplace series and requires a low number of expansion coefficients, only. Symmetries can be included to impose special geometries or to further reduce the number of coefficients. The efficiency of the approach enables a fast optimization of the surface. This is particularly useful for electrically small lenses. Three exemplary lens designs based on different specifications are obtained through optimization. The manufacturing is discussed and the radiation characteristics are explored and validated through measurements.

In-situ probes for patch antenna array calibration

A novel calibration network for patch antennas is proposed. We introduce magnetically coupled in-situ probes, which excite the fundamental patch mode. In that way, finite array effects and mutual coupling are taken into account, providing the opportunity for accurate online calibration of active antenna terminals. The specific advantages of the approach are demonstrated for linearly polarized patch antennas. Realization aspects of the multilayer antenna are discussed and the effect of some fabrication imperfections are investigated. Measured S-parameters as well as radiation simulation results of a single patch with the integrated probes are presented. Based on simulation of antenna arrays with in-situ probes the calibration accuracy is given in theory.

An Electronically Scannable Reflector Antenna Using a Planar Active Array Feed at Ka -Band

This contribution presents the system design procedure and performance of an array fed reflector antenna. Combining the inherent benefits of a reflector antenna—high gain, low-cost, and simplicity—with the agility provided by a scannable active array feed, enables a new range of applications, for instance in commercial mobile antenna terminals. The whole arrangement features a restricted field of view for either scanning or multibeam applications. To minimize system cost, a planar patch antenna array in printed circuit board technology is used for the feed and the reflector diameter is restricted to 60 cm. To obtain optimal performance, both the reflector and the feed are specifically designed for the desired application, i.e., mobile satellite communication at Ka-band. A comprehensive study of various rotationally symmetric reflectors is carried out to determine arrangements maximizing the field of view and still complying with the respective regulations. For the feed, a 30 GHz transmit array with 49 elements is developed, enabling 2-D scanning in a ±6° conical sector. It includes a wideband signal distribution network and frontend electronics.