Fruit-frost during spring is one of the main causes of damage to the harvest of fruit in orchards. Various systems using different methods of preventing spring-frost are available on the market. To determine when these systems should be activated, the temperature in the orchard needs to be determined. In this project, a self-sustaining autonomous temperature sensor network is designed, which is capable of making a 3D temperature map of the orchard. The system is used to warn farmers when the threat of fruit-frost occurs and to gather data on the spatial variation of the temperature in the orchard. In this thesis, the focus is put on designing the smart measurement and control system. This includes choosing an appropriate control unit and temperature sensors. Also, the software for the control unit is designed, which allows for a smart measurement scheme that balances energy usage and measurement frequency. Finally, an estimation of the energy usage of the subsystem is given based on theoretical analysis.

Photoconductive antennas (PCAs) are an interesting candidate for imaging systems due to their relatively low cost and ability to provide a bandwidth of hundreds of GHz. The large bandwidth of PCAs allows for sub-millimeter depth resolution. However, the often-used single-element PCAs are intrinsically limited in the amount of power they can radiate due to several saturation effects. To increase the radiated power, array-based PCAs have been introduced by the scientific community. In the first part of this work, the impact of adding a leaky wave cavity to a lens-coupled Photoconductive Connected Array (PCCA) is studied. The fields radiated by the lens are found using a Physical Optics method, and the effect of the lens on the energy spectra of the radiated fields is quantified. Measurements of two fabricated PCCA geometries are compared with simulations. In the second part of this work, an imaging setup is designed to benchmark several state-of-the-art PCAs. Subsequently, the coupling between two PCAs in an imaging setup is studied via a field-matching formalism.