Bernhard Schoenlinner

Wide-scan spherical-lens antennas for automotive radars

A new approach to wide scan-angle antennas at millimeter-wave frequencies is introduced with special focus on ease of manufacturing and reliability. The system is composed of planar feed antennas (tapered-slot antennas), which are positioned around a homogeneous spherical Teflon lens. Beam scanning can be achieved by switching between the antenna elements. The spherical-lens system is analyzed through a combined ray-optics/diffraction method. It is found that a maximum efficiency of 50%-55% can be achieved using Teflon, Rexolite, or quartz lenses. The efficiency includes taper, spillover, and reflection loss. Calculations also indicate that the maximum lens diameter is 30-40 /spl lambda//sub 0/, which results in a maximum directivity of 39.5-42 dB. Measurements done on a single-element feed and a 5-cm Teflon lens agree very well with theory and result in a 3-dB beamwidth of 5.5/spl deg/ and better than -20-dB sidelobe levels at 77 GHz. Absolute gain measurements show a system efficiency of 46%-48% (including dielectric loss). A 23- and 33-element antenna array with a scan angle of /spl plusmn/90/spl deg/ and a -3.5- and -6-dB crossover, respectively, in the far-field patterns was also demonstrated. The 23-element array resulted in virtually no gain loss over the entire 90/spl deg/ scan angle. This represents, to our knowledge, the first wide scan-angle antenna at millimeter-wave frequencies.

A 24-GHz high-gain Yagi-Uda antenna array

A compact 24-GHz Yagi-Uda antenna has been developed using standard design tables and simple scaling to take into account the added capacitance due to the supporting dielectric substrate. The antenna results in a directivity of 9.3 dB, a front-to-back ratio of 11 dB, and a bandwidth of 2.5-3%. The Yagi-Uda antenna has been implemented in an 11-beam system using a planar array and a 2-inch Teflon spherical lens. The measured patterns show a 22 dB gain beam, a cross-polarization level of -24 dB, and a crossover level of -6 dB. The design method presented in this paper is quite straightforward, and can be used to develop low-, medium-, and even high-gain endfire Yagi-Uda antennas.

RF-MEMS Switch and Phase Shifter Optimized for W-Band

This paper presents the optimization of the low-complexity RF-MEMS technology for W-Band, the fabricated switches and phase shifters. All devices are fabricated on a thinned silicon substrate using only one metallization. The basic W-Band switch used for the phase shifter is presented in detail showing a very wide band RF-behaviour with an almost constant insertion loss of about -0.3 dB from 50 - 100 GHz. The 3-bit phase shifter itself with the design frequency of 76.5 GHz is realized using one loaded-line and two switched-line phase shifter elements. The mean insertion loss of the whole phase shifter is -5.3 dB and the phase deviation was calculated to be 13.4deg. Furthermore an extension to a 4-bit phase shifter by the use of a dual-state microstrip line phase shifter element is given. In addition, a short switching-time of the switches of only 15 mus was measured.

Hybrid Integrated RF-MEMS Phased Array Antenna at 10GHz

In this paper, a one-dimensional electrically steerable RF-MEMS phased array antenna for operation at 9.5 GHz is demonstrated. The antenna itself is a four by eight patch antenna array realised on low-loss Teflon substrate and the feed network made out of the same substrate is a one-to-four corporate feed network. The phase shifting necessary to steer the main beam of the antenna in the H-plane of the aperture is achieved by four 3 bit RF-MEMS phase shifters, which are integrated in a hybrid fashion between the antenna and the feed network. The paper describes the integration of the different elements in a standalone phased array antenna demonstrator. The design of the 3 bit RF-MEMS phase shifters is presented and validated by very good measurement results. Finally, the measured radiation characteristic of the complete phased array antenna is shown for different switching states of the phase shifters.

LTCC Patch Array for RF-MEMS based Phased Array Antenna at 35GHz

In this paper, a LTCC patch antenna array for Ka-band RF-MEMS based electrically steerable antenna is demonstrated. The paper presents a novel hybrid integration concept for the RF-MEMS phase shifters intended to steer the main beam of the antenna in the H-plane of the aperture. According to the proposed configuration, the phase shifters realised in silicon technology are packaged using LTCC lids bonded on top of the silicon chips and are flip-chip mounted on the antenna realised on LTCC. The architecture allows for the realisation of highly integrated RF-MEMS based phased array for millimetre-wave front-ends and aims at reducing the complexity and costs of such modules. The design of the four by four aperture coupled patch antenna array is validated by satisfactory measurement results. A study of the repeatability of the LTCC process used to fabricate the antenna is carried out over a population of five samples and the behaviour of the matching of the antenna over temperature is investigated.

Compact multibeam dual-frequency (24 and 77 GHz) imaging antenna for automotive radars

2 versions of a compact multi-beam dual-frequency antenna for 24 and 77 GHz have been developed for automotive applications. The antenna consists of a spherical Teflon lens with a frequency selective surface (FSS), which is fed by two sets of endfire tapered slot antennas (TSAs). The FSS is built on a 127 ¿m-thick Duroid¿ substrate and is placed between two Teflon hemispheres, and is reflective at 24 GHz and transparent at 77 GHz in the first design, and is transparent at 24 GHz and reflective at 77 GHz in the second design. The TSAs for the 24 GHz and 77 GHz systems are built on a single piece of 254 ¿m-thick Duroid¿ substrate. The measured patterns result in E and H-plane patterns with a -3-dB beamwidth of 19° at 24 GHz and 5.5° at 77 GHz. The sidelobe level is better than ¿17 to ¿20 dB when the FSS is transparent and is better than ¿14 dB when the FSS is reflective. The calculated efficiency of this antenna system is around 50%. The current designs provide 33° coverage at 24 GHz (3 beams) and 55° coverage at 77 GHz (11 beams) in the first design, and 99° coverage at 24 GHz (7 beams) and 33° coverage at 77 GHz (7 beams) in the second design, but the angles can be changed to suit different coverage angles.

High Q Micro-machined Cavity Resonator Filter in Low-Cost Silicon Technology

This paper demonstrates a two-pole filter based on high Q micro-machined cavity resonators for operation at 20 GHz. The filter implements a novel inter-resonator coupling cavity placed above the inter-cavity wall separating the resonators and etched out of silicon using the same KOH-etching process as the one used to realised the cavity resonators. The Q-factor of a single cavity resonator is measured as well as the response of the two-pole filter. The filter presented here constitutes the first development step toward a more sophisticated fixed as well as tunable four-pole filter aiming at the replacement of bulky waveguide filters mounted in a majority of satellite transceivers.

A new class of bandpass frequency selective structures

This work presents a new approach for designing frequency selective surfaces. In this approach the FSS is composed of AFA cells, which receive, filter. and transmit the signal. Two types of 3-pole bandpass FSS have been designed using the AFA approach. which demonstrate the application of this technique for synthesizing all-pole as well its more complicated bandpass FSSs. Finite element simulations predict an excellent performance for these designs at normal incidence. Prototypes of these FSSs are currently being fabricated, which will be used to verify the numerical results and determine the performance limitations such as insertion loss and angular sensitivity.

Broadband Single-Pole Multithrow RF-MEMS Switches for Ka-Band

This paper presents the design, fabrication and RF-characterization of SP3T, SP4T and SP6T RF-MEMS switches. All devices are fabricated on a 200 ¿m thin silicon substrate. The insertion loss of the SP3T is almost constant from 18 - 40 GHz with a value better than -0.5 dB. The SP4T and SP6T show an insertion loss better than -0.9 dB from 18 - 40 GHz. The isolation is better than -17 dB for all switches in almost all switching states from 18-40GHz. Furthermore, an on-wafer absorbing structure, acting as a quasi 50 ¿ match is shown, exhibiting a return loss of better than -10 dB for frequencies above 20 GHz.

Spherical-Lens Antennas For Millimeter Wave Radars

A low-cost 77 GHz spherical lens antenna has been developed for mobile applications. The antenna system consists of a 5 cm spherical Teflon lens which is fed by an endfire tapered slot antenna on a 127 ¿m-thick Duroid¿ substrate. The measured patterns result in symmetrical diffraction limited E and H-plane patterns with a 3-dB beamwidth of 5.5°, a sidelobe level below -20 dB and a crosspolarization level of -19 dB. The calculated efficiency of this antenna system is 54%. The efficiency includes spillover loss, amplitude taper, non-uniform phase, and reflection loss. This very low cost antenna can be easily extended to provide 170° coverage using a circular feed array around the spherical Teflon lens.