A defected microstrip structure (DMS) is proposed to reducing the size of a rectangular patch antenna by increasing its electric length, without degrading its performance. To illustrate this advantage, one conventional and one proposed defected patch antenna were developed and measured at 1.77 GHz. The simulated and measured results concerning the radiation patterns and bandwidth of both antennas are very closely related, but the proposed defected antenna achieves 22% of total‐area reduction. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 481–484, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20508

This paper describes a pair of compact CW/FM airborne SAR systems for small UAV-based operation (wingspan of 3.5 m) for low-cost testing of innovative SAR concepts. Two different SAR instruments, using the C and X bands, have been developed in the context of the ARBRES project, each of them achieving a payload weight below 5 Kg and a volume of 13.5 dm3 (sensor and controller). Every system has a dual receiving channel which allows operation in interferometric or polarimetric modes. Planar printed array antennas are used in both sensors for easy system integration and better isolation between transmitter and receiver subsystems. First experimental tests on board a 3.2 m wingspan commercial radio-controlled aircraft are presented. The SAR images of a field close to an urban area have been focused using a back-projection algorithm. Using the dual channel capability, a single pass interferogram and Digital Elevation Model (DEM) has been obtained which agrees with the scene topography. A simple Motion Compensation (MoCo) module, based on the information from an Inertial+GPS unit, has been included to compensate platform motion errors with respect to the nominal straight trajectory.

UAV (unmanned Aerial Vehicle) platforms represent a challenging opportunity for the deployment of a number of remote sensors. These vehicles are a cost-effective option in front of manned aerial vehicles (planes and helicopters), are easy to deploy due to the short runways needed, and they allow users to meet the critical requirements of the spatial and temporal resolutions imposed by the instruments. L-band radiometers are an interesting option for obtaining soil moisture maps over local areas with relatively high spatial resolution for precision agriculture, coastal monitoring, estimation of the risk of fires, flood prevention, etc. This paper presents the design of a light-weight, airborne L-band radiometer for deployment in a small UAV, including the hardware and specific software developed for calibration, geo-referencing, and soil moisture retrieval. First results and soil moisture retrievals from different field experiments are presented.

The development of two reduced microstrip slot antennas with a U‐shaped resonant configuration is presented. The additional resonator is located inside the slot and is designed to perform dual band operation, covering the 2.4 GHz and 5.8 GHz WLAN frequency bands. The main goal of the antenna design is to get the optimum size reduction without significant degradation of electrical characteristics compared to a similar antenna reported in literature. The antenna implementation was done using low cost substrates. A size reduction of 84% was got by using a dielectric constant substrate of 10. Simulation and experimental results are presented for both antennas, showing close convergence. Their radiation patterns have quasi‐omnidirectional behavior useful for WLAN applications. Both antennas have small size suitable for mobile applications. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2684–2689, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27187

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