RF Level Shifter Bias Control for Standby Noise Reduction
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Solution Overview
Problem
Existing RF switch control systems face challenges in maintaining isolation and performance across different RF bands and modes, particularly during standby modes where charge pumps can introduce noise and unpredictably control gate voltages, leading to degradation in system performance.
Innovation Solution
The proposed RF system incorporates a charge pump that generates a voltage, a level shifter, and a level shifter control circuit to control RF switches based on a mode signal, enabling or disabling the charge pump and adjusting bias voltages to track the charge pump voltage in active mode and stabilize in standby mode, ensuring proper voltage levels for RF switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the charge pump is enabled to generate voltage for RF switch control, then the RF switch can operate properly across different bands, but noise is introduced and performance degrades in standby mode
Solution Approach 1:
The bias voltage supplied to the RF switch is made dynamic by tracking the charge pump voltage when active and transitioning to a fixed standby voltage when the charge pump is disabled. This dynamic adaptation allows the system to maintain proper RF switch operation during active bands while eliminating noise during standby mode, thus resolving the contradiction between versatility and harmful factors.
2Productivity
If the charge pump voltage is used directly to control RF switch gates, then switching between bands is facilitated, but gate voltages become unpredictable in standby mode leading to performance degradation
Solution Approach 1:
A bias voltage intermediary circuit is introduced that conditionally couples the charge pump voltage to the RF switch gates. During active mode, the bias voltage tracks the charge pump voltage enabling fast switching. During standby mode, the bias voltage decouples and provides a fixed predictable voltage level, ensuring reliable gate control. This intermediary resolves the contradiction between switching productivity and gate voltage reliability.
Data Source
AI summary
Apparatus and methods for level shifting in a radio frequency system are provided. In certain configurations, a radio frequency system includes a level shifter operable to provide level shifting to an input signal. The level shifter is biased by a bias voltage and powered by a supply voltage and a charge pump voltage. The radio frequency system further includes a charge pump configured to provide the charge pump voltage and to receive a mode signal operable to enable the charge pump in a first state and to disable the charge pump in a second state. The radio frequency system further includes a level shifter control circuit configured to control the bias voltage to track the charge pump voltage when the mode signal is in the first state, and to control the bias voltage with the supply voltage when the mode signal is in the second state.