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Non reciprocal passive components on LTCC ferrite substrate

Abstract : This thesis investigates passive non-reciprocal components (mainly circulators) based on ferrite Low Temperature Co-fired Ceramic (LTCC) substrate. The external magnets used in conventional circulators must be strong to overcome the ferrite's demagnetization field. The novel circulator presented herein uses an embedded winding within the ferrite substrate to magnetize the material from the inside, thereby significantly reducing the demagnetization effects. Because of the controllability of the bias field, the resulting device is also multifunctional: when the windings are energized by a current, the device operates as a dynamic circulator in which the circulation direction can be changed by switching the direction of the current. Unlike other LTCC circulators with external magnets, the proposed device can even operate as a power splitter by removing the bias current. A circulator prototype has been characterized in three states: unbiased, biased by winding and biased by winding and external magnets. When no current is applied, the transmission of each port is about -5 dB with return loss better than 20 dB at 14.8 GHz. When a current of 300 mA is injected into the winding, the measured insertion loss and isolation of the circulator is approximately 3 dB and 8 dB, respectively, whereas the return loss is better than 20 dB at 14.2 GHz. When external magnets are added in addition to the current of 200 mA, the insertion loss and isolation is improved to 1.6 dB and 23 dB, respectively at 14.2 GHz. The variation of the circulator's working frequency is 0.6 GHz. This is achieved firstly by the change of internal magnetization M when current is less than 120 mA, then the heat in the substrate due to the winding introduces more frequency shifting. The total size (L*W*H) is 8mm*8mm*1.1mm
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  • HAL Id : tel-01628200, version 1

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Shicheng Yang. Non reciprocal passive components on LTCC ferrite substrate. Optics / Photonic. Université Jean Monnet - Saint-Etienne, 2015. English. ⟨NNT : 2015STET4020⟩. ⟨tel-01628200⟩

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