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SummaryMoisture migration induced volume change in cereal materials was studied by environmental scanning electron microscopy, videomicroscopy and stereoscopy. It is shown that the in situ volume change can be monitored by the changes of projection area with the assumption of isotropic swelling/shrinkage. The projection area change from videomicroscopy matches well with the volume change by stereoscopy after dimensional normalization. The arbitrary volume values in between two relative humidity levels are available by interpolating the equilibrium volumes at beginning and ending. The sorption/desorption curves were fitted by the 'parallel exponential kinetics' model, which described two independent, parallel processes as 'slow' and 'fast'. In the low relative humidity range, sorption curves match well with the 'parallel exponential kinetics' model and the two parallel processes tend to be identical when relative humidity increases. The diffusivity of water moisture in a cracker, which was estimated by the half-equilibrium principle, has a strong dependence on relative humidity.

This letter presents the design of a Ka-band active integrated antenna in package (AIAiP). A monolithic microwave integrated circuit amplifier based on the GaAs process and a compact patch antenna based on the printed circuit board process are implemented, respectively. Then, the amplifier and antenna are assembled together in a specified package using the wire-bond process. Thus, compared to the traditional solutions, the transmission loss and the size of the proposed AIAiP are significantly reduced. Furthermore, the influence of the bonding wire and the package is taken into account in the design of the amplifier and the antenna, respectively. A good agreement between the simulation and measurement results can be observed. The proposed AIAiP occupies a compact size of 7 × 7 mm 2. Meanwhile, it achieves −10-dB impedance bandwidth from 33.4 to 37.2 GHz and a peak gain of 18.9 dBi at 35 GHz. Additionally, the impact of the package size on the antenna performance has been demonstrated for future AIA designers. Index Terms-Active integrated antenna (AIA), antenna in package, GaAs amplifier. I. INTRODUCTION A CTIVE integrated antenna (AIA) refers to the antenna integrated with one or more active solid-state devices. The AIA has received considerable interest due to its advantages in low loss and compact size, and is much more suitable for the phased-array antenna systems [1], [2]. Several kinds of AIAs