PLL Switching in RF Transceivers for Low-Power Phase Noise Control
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Solution Overview
Problem
RF transceivers in ultra-low power systems face high power consumption due to always-on voltage controlled oscillators (VCOs) and phase locked loops (PLLs), leading to interference issues when VCOs are not sufficiently isolated, which can overpower received signals.
Innovation Solution
A transceiver design that includes a phase lock loop (PLL) with a common control circuit and switches for VCOs, a mismatch compensation device, and a leakage compensation device to optimize power usage and reduce interference by controlling the VCOs' operation based on transmission and reception modes, and using quenching waveform generators to prevent overlapping oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PLL and VCO are kept on all the time to maintain frequency accuracy, then frequency stability is improved, but power consumption increases
Solution Approach 1:
The patent applies periodic action by controlling the PLL and VCO to operate only during specific periods (transmission or reception modes) rather than continuously. The controller activates the PLL and VCO when needed for signal transmission or frequency synthesis, and deactivates them during idle periods, thereby maintaining frequency stability when required while significantly reducing average power consumption.
2Adaptability or versatility
If multiple VCOs operate simultaneously to support both transmission and reception, then communication functionality is improved, but interference between VCOs increases
Solution Approach 1:
The patent implements periodic action by sequentially activating different VCOs based on operational mode. During transmission mode, the transmission VCO is activated while the reception VCO is deactivated. During reception mode, the reception VCO is activated while the transmission VCO is deactivated. This time-division approach maintains full communication functionality while eliminating simultaneous VCO interference.
Solution Approach 2:
The controller performs preliminary action by predicting the operational mode requirements and activating the appropriate VCOs before actual transmission or reception begins. This ensures that the required VCO is already operational and stable when communication starts, while preventing unnecessary simultaneous operation that would cause interference.
Data Source
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AI summary
A transceiver may include a reception (Rx) radio frequency (RF) part configured to process a received signal, a transmission (Tx) RF part configured to process a transmitted signal, and a phase lock loop (PLL) configured to provide a reception frequency to the reception RF part and provide a transmission frequency to the transmission RF part. The PLL may be controlled according to whether the reception RF part or the transmission RF part is on. In addition, a transceiver may include quenching waveform generator (QWGs) to control quenching waveforms of the RF parts corresponding to a plurality of antennas. The quenching waveforms may be generated respectively by VCOs operating at a same frequency. The QWGs may control the VCOs such that the quenching waveforms do not overlap.