Uppsala universitet
Integrated Antennas
Monolitic and Hybrid Approaches

Erik Öjefors

PhD Thesis, Uppsala University, ISBN 91-554-6651-6 Oct. 2006, 69 pp. summary, Acta Universitas Upsaliensis 221.

Dissertation in Engineering Science with specialization in Microwave Engineering, publicly examined in Siegbahnsalen, Ångström Laboratory, Uppsala on October 12, 2006 at 10.15 a.m.


The thesis available in Pdf: 4.3 M.

Paper copies of the thesis can be obtained from Ylva Johansson, Signals and Systems Group, Uppsala University, Box 534, SE-75121 Uppsala, Sweden.


Outline:
Due to recent advances in semiconductor manufacturing, complete single chip radio receivers and transmitters for micro- and millimeterwave frequencies can be built in standard silicon processes. However, an external antenna has so far been needed in order to obtain a complete radio module. In this thesis, integration of antennas on the same chip or printed circuit board as the radio electronics is presented.

The use of on-chip antennas offers the benefit of reduced complexity in the packaging and assembly of millimeter-wave radio modules. The absence of an external antenna also allows complete wireless communication and sensor modules of only a few millimeters size to be built. One application for the studied integrated antenna radio chips is short range communication links operating in the license exempt 24 GHz and 60 GHz frequency bands. Another application is car radars for collision avoidance and intelligent cruise control at 24 GHz and 77 GHz.

It is known that the capacity and range of wireless communication networks can be extended by the use of steerable base station antennas, which direct the radiation towards active users in the network. Due to the high complexity and cost, steerable antennas are however not in common use. In this thesis, a integration method where the beam steering electronics is placed on the same printed circuit board as the antenna elements is proposed and evaluated. As only a few extra components are required compared to a conventional antenna design, the additional cost of the beam steering electronics is low.

Abstract:
This thesis considers integration of antennas and active electronics manufactured on the same substrate. The main topic is on-chip antennas for commercial silicon processes, but hybrid integration using printed circuit board technology is also addressed.

The possible use of micromachining techniques as a means of reducing substrate losses of antennas manufactured on low resistivity silicon wafers is investigated. Compact dipole, loop, and inverted-F antennas for the 20-40 GHz frequency range are designed, implemented, and characterized. The results show significantly improved antenna efficiency when micromachining is used as a post-processing step for on-chip antennas manufactured in silicon technology.

High resistivity wafers are used in a commercial silicon germanium technology to improve the efficiency of dipole antennas realized using the available circuit metal layers in the process. Monolithically integrated 24 GHz receivers with on-chip antennas are designed and evaluated with regard to antenna and system performance. No noticeable degradation of the receiver performance caused by cross talk between the antenna and the integrated circuit is observed.

For low frequency antenna arrays, such as base station antennas, hybrid integration of active devices within the antenna aperture is treated. A compact varactor based phase shifter for traveling wave antenna applications is proposed and evaluated. Electrically steerable traveling wave patch antenna arrays, with the phase shifters implemented in the same conductor layer as the radiating elements, are designed and manufactured in microstrip technology. It is experimentally verified that the radiation from the feed network and phase shifters in the proposed antenna configuration is small.

Keywords:
antenna travelling wave arrays, antenna phased arrays, phase shifters, micromachining, silicon, monolithic microwave integrated circuits, dipole antennas, loop antennas, slot antennas.

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