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In this study, we design a pair of third‐order conformal Hilbert curve antennas for use in capsule endoscopy at three different bands (Industrial, Scientific, and Medical [ISM]), especially at 433 MHz, 915 MHz, and 2.45 GHz. The antennas are placed orthogonally with respect to each other, offering dual linear polarization characteristics, which have been highlighted in literature as the most robust communication link between a roaming transmitting capsule within the GI tract and the receiver antenna. The robustness of the link depends on (i) invariance of linear polarization with the position and orientation of the roaming transmitter, as well as (ii) tolerance of linearly polarized fields to depolarization effects when penetrated through the body. The antennas were manufactured on polyimide substrate, which was wrapped around a 3D‐printed capsule volume. Both antennas were measured inside bovine muscle tissue and the obtained results have been compared with the simulated results to validate the performance of the propose solution. The presented results showed that, the return loss characteristics and the measured bandwidth, for both antennas inside bovine muscle tissue, have matched with the simulated results. To the best of our knowledge, these demonstrated antennas are the first designed capsule antennas to address three ISM bands with dual linear polarization. The designed antennas can be adapted for clinical use with further development.

In this study, we illustrate the design and implementation of a wideband microwave small-signal amplifier composed of mixed elements. The design is based on Simplified Real Frequency Technique (SRFT). A design of low power amplifier circuit is completed and its simulations are performed in success. The circuit is designed with lumped elements, however, some of the lumped elements are converted to distributed elements for their convenience in production. In this way, a mixed element wideband microwave amplifier comprised of input/output matching networks with lumped and distributed elements has been formed. Layout work and also post layout simulation is given with satisfying results.

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Generation of proper source/ load pull impedances for a selected GaN device is essential to design a microwave power amplifier for optimum gain and power-added efficiency. As they are obtained, these impedances may not be realizable network functions over the desired frequency band. Therefore, in this paper, first, we introduce a new method to test if the given source and load impedances are realizable. Then, a novel numerical procedure is introduced to model the source and load pull impedances as realizable network functions, which in turn results in the optimum power intake and power delivering capacity for the GaN transistor used in the design. In the numerical modelling process, a robust tool called "Virtual Gain Optimization" is presented. Numerically generated realizable source and load impedances are modelled analytically. Eventually, these impedances are synthesized using our automatic Darlington Synthesis Robot software to yield the optimum input and output matching network topologies with component values. Examples are presented to test the realizability of the given source/load pull impedance data. Then, the power intake and delivery capacity of the active device are assessed for a 10W-GaN power transistor, namely "Wolfspeed CGH40010F" over 0.8-3.0 GHz bandwidth. Eventually, the power amplifier is designed and manufactured. It is shown that the computed and the measured performance of the amplifier is very close with 10 Watts output power, 11.4 ± 0.6 dB gain and 49% to 76 % power added efficiency.