| dc.description.abstract | This thesis proposes high-efficiency RF energy harvester (EH) designs using a system-in-package (SiP) technique. The EH is consisted of matching networks, interconnects, and rectifiers. The matching networks are realized on a low-loss Glass-Integrated-Passive-Devices (GIPD) carrier while the rectifiers are implemented in a 0.18-µm CMOS technology. The CMOS chip is flipped and bonded onto the carrier through the interconnects. The native devices with threshold voltage of 0.2 V in the 0.18-µm CMOS technology enable the rectifiers to have high sensitivity. Passive components with high quality factor (Q) provided by the GIPD technology are used to design the matching networks. This not only gives a compact solution, but higher impedance transformation ratio between the source resistance and the rectifier input impedance also becomes feasible, which provides higher voltage gain to greatly enhance the EH efficiency. Three RF EHs are designed in this thesis to demonstrate the benefits of using the SiP technique.
The performance of the first RF EH is compared with that of a RF EH using a system-on-a-chip (SoC) technique in a 0.18-µm CMOS technology. The measurement result shows that the SiP-based RF EH provides peak efficiency of 4.7% at 2.4 GHz, around 72% improvement as compared with that of the SoC-based one.
The second RF EH improves the efficiency of the first one by optimizing an interconnect between the chip and the carrier and choosing a better inductor type. By properly designing the gap between the signal and ground bonding pads, the impedance mismatch and the power loss caused by the return path of the interconnect can be minimized. The simulated insertion loss is only -0.04 dB at 2.4 GHz, 2.85 dB improvement over the interconnect used in the first RF EH design. Moreover, considering the design rules of the GIPD technology, octagon inductors employed in the first RF EH design have limited design freedom due to the minimum via size requirement of 35×35 μm2. To avoid the via size issue, the square inductors are chosen, which enhances inductor Q from 22 to 31 at 2.4 GHz as compared with that of octagon ones. The measured efficiency of the second RF EH is 6.8%, 1.44 times better than that of the first RF EH design.
The third RF EH can provide dual-band operation by integrating additional band-pass and band-stop filters (BPF/BSF) before the matching networks. The proposed BPF/BSF can provide zeros and poles to pass and stop signals, respectively, allowing dual-band operation. The proposed dual-band RF EH can give measured output voltage of 1.51 V and 1.0 V with conversion efficiency of 9.6% and 7.0% at 0.89 and 2.52 GHz, respectively. | en_US |