A monostatic microwave transmission experiment for line integrated precipitation and humidity remote sensing

AbstractNear-surface water vapor and precipitation are central hydrometeorological observables which are still difficult to quantify accurately above the point scale. Both play an important role in modeling and remote sensing of the hydrologic cycle. We present details on the development of a new microwave transmission experiment that is capable of providing line integrated estimates of both humidity and precipitation near the surface. The system is located at a hydrometeorological test site (TERENO-prealpine) in Southern Germany. Path length is kept short at 660m to minimize the likelihood of different precipitation types and intensities along the path. It uses a monostatic configuration with a combined transmitter/receiver unit and a 70cm trihedral reflector. The transmitter/receiver unit simultaneously operates at 22.235GHz and 34.8GHz with a pulse repetition rate of 25kHz and alternating horizontal and vertical polarization, which enable the analysis of the impact of the changing drop size distribution on the rain rate retrieval. Due to the coherence and the high phase stability of the system, it allows for a sensitive observation of the propagation phase delay. Thereof, time series of line integrated refractivity can be determined. This proxy is then post-processed to absolute humidity and compared to station observations. We present the design of the system and show an analysis of selected periods for both, precipitation and humidity observations. The theoretically expected dependence of attenuation and differential attenuation on the DSD was reproduced with experimental data. A decreased performance was observed when using a fixed A–R power law. Humidity data derived from the phase delay measurement showed good agreement with in situ measurements

Passive guaranteed broadband equivalent circuit derivation of symmetrical multi-port systems: application to multi-conductors and RF-Inductors

In this paper a passive guaranteed wide-band equivalent circuit derivation methodology bridging physical topology considerations with SPICE model extractions is proposed. Electromagnetic modal states formalism is considered for bridging between physical topology and SPICE models. The attributes of the proposed derivation in comparison with conventional extraction techniques based on pole-residue expansion, classical Π/T models, and Broad-Band-SPICE (BBS) models are discussed. The validity of the broadband extracted scalable models is demonstrated through correlations with RF measurement carried out on CPW transmission lines and coupled self-inductors up to high frequencies