With the increase in demand for compact and high data rate communication systems, there is a need for high efficiency with modulated signals (PAPR 5-10 dB) for base-station power amplifiers. One of the famous architectures used to achieve this is Doherty architecture. The architecture has recently been extended to the Load Modulated Balanced Amplifier (LMBA) concept, where a separate integrated amplifier generates the control signal for load modulation. Almost all published studies are concerned with discrete "PCB-based" solutions for LMBA. In a recent study [1], the potential of designing an integrated LMBA in 0.18 μm CMOS has been evaluated. The main limitation concerning losses and area comes from the quadrature couplers, consisting of either two or four inductors. Using active inductors in the coupler design may be possible to obtain a more cost-effective solution. However, several aspects must be taken into consideration. One is that the power consumption of the active inductor should not exceed the power loss of the passive inductor. Another one is the ability to handle high power signals (high voltage swing), corresponding to 10-15 dBm at the input of the amplifier. The main objective of this thesis is to implement a hybrid coupler using an active inductor based on the theory of gyrators. The circuits were implemented using TSMC 0.18 μm process. The coupler and the active inductor are designed to operate at 2 GHz centre frequency. The active inductor implemented is considerably linear up to 12 dBm. The coupler has an input reflection coefficient (S11) of -26 dB, the transmission coefficient (S21) of -4.4 dB, and a coupling coefficient (S31) of -2.4 dB. The coupler shows good coupling and isolation characteristics. The phase difference between the through-port and the coupled-port of the coupler is 92°. As a result, when used as a power divider at the input of the power amplifiers, a PAE (Power Added Efficiency) of 63% and output power of 23 dBm is obtained at an input power of 12 dBm.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:liu-182432 |
| Date | January 2021 |
| Creators | Doddanna, Karthik |
| Publisher | Linköpings universitet, Elektroniska Kretsar och System |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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