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The use of ultra-wideband signals for moisture sensing by electromagnetic wave interaction provides more information on the material under test compared to single tone or narrowband approaches, regarding spatial and frequency dependent phenomena. Current activities to regulate the emission of electromagnetic waves in the spectral band up to 10 GHz for sensor applications open new perspectives for microwave moisture sensing. Therefore, improved and cost effective ultra-wideband measurement principles will become more and more interesting. The use of short pulses or swept sine waves are classic approaches to cover a large spectral band. However, this paper deals with some variants of an alternative method, which applies pseudo-random codes, namely M-sequences, to stimulate the test objects. The method permits monolithic integration of the RF-electronics in SiGe technology. The signal generation and data capturing are referred to a common stable single tone clock and they are controlled by steep trigger signals. This provides for very stable operation, which allows for measurements in both time and frequency domain. Two versions of an M-sequence approach will be considered and their functioning will be demonstrated by means of simple measurement examples.

The paper presents a simple principle to measure the transfer function or rather the impulse response of ultrawideband systems. The main aspects of the new measurement head are its flexibility of application, its measurement speed and the possibility of a full circuit integration, which results in small, robust, lightweight and low cost devices with low power consumption. Beside this, the method allows the measurement of multi-port devices and it has a good suppression of perturbation signals. These advantages may be exploited in a great variety of microwave sensing applications, covering single sensor and array arrangements.

Ring oscillator delay Early voltage V, k a x M. RoBberg', J. Sachs', P. Rauschenbach', P. Peyerl', K. Presse13, W. Winkler3, D. Knoll3 ~~ 22 .. 25 ps, FJF, = 1 , AV = 200 mV 40 V, V, , = 0.6 V, V , , = 0 V 80 -150ABSTRACT Transmitter and receiver circuits operating at 11 GHz system clock rate are described. These circuits, fabricated in a 0.8 vm SiGe-HBT technology, are the key elements of a radar head using a new ultra wideband principle.

Random noise radar attracts interest mainly because of its low interference and its camouflaged operation, as well as the relaxed requirements concerning transmitter power. Its challenge for very wideband operation is the impulse compression in order to gain range resolution. The use of pseudo random codes largely defuses this problem while keeping most advantages of random noise radar. Modern semi-conductor technologies permit the implementation of code generators operating at clock-rates up to tens of GHz at reasonable costs. The resulting range resolutions are to be found in the cm-and sub-cm-range. The implementation of our radar core is based on SiGe:Ctechnology. An overview of the basic system configurations will be given.

Ultra wideband sounding has been found to be suitable for a large number of applications in various areas. This results in a variety of different requirements concerning the measurement electronics. The article describes a conception of a measurement system, which provides for high flexibility in adapting performance to the actual need.

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Zusammenfassung Robuste Sensoren für die zerstörungsfreie Materialcharakterisierung im Labor und unter rauen industriellen Bedingungen sind von zunehmendem technischen und ökonomischen Interesse. Dieser Artikel behandelt die Entwicklung und Anwendung eines prozesstauglichen, modularen und breitbandigen impedanzspektroskopischen Hard- und Softwarekonzepts für den Feld- und Laboreinsatz. Besondere Beachtung finden weiterhin auch technische und biophysikalische Aspekte der Bio-Impedanzspektroskopie.