Low Phase Noise Oscillator and Frequency Divider for SAW-Less receiver

The constant growth of wireless mobile communication systems, to keep up with consumer requests of higher data rate and lower latency yet maintaining a cheap cost of the new devices, necessitates RF engineers efforts to find implementing solutions for the latest standards, like 5G. The increase in complexity of the designs is exponential: the enormous number of bands for TX and RX, wider channel bandwidth, and higher frequency of operation must satisfy the rigorous requirement of FDD standards. In FDD the receiver and the transmitter, working at different frequencies, share the same antenna. For each band, a non-tunable duplexer is needed to decouple TX and RX, which is an off-chip component that exploits a SAW filter to guarantee isolation and filtering (up to 55dB) of unwanted signals like TX-leakage, self-interference signals and blockers. Off-chip components are bulky and expensive and the increment of them will result in an uneconomical choice. To overcome this cost-effective problem, numerous solutions have been presented in latest years, with the purpose of integrate on-chip the filters. The project exploits the concept of diversity, i.e., a form of redundancy in the communication scheme. Two communication channels are used to improve the quality of transmission and get through the problem of removing the high filtering action of a common SAW filter. This thesis proposes a Low Phase Noise Oscillator to relax the problem of reciprocal mixing affecting the down-conversion mixer, which increases the Noise Figure of the receivers and degrades the performance obtained. Then a frequency divider by two is implemented, which guarantees four output signals with 90° phase shift one from the others for the quadrature mixer and improve the Phase Noise. Finally, a TX-leakage and Reciprocal Mixing noise cancellation system is studied.