Dynamic Bias RF Switch Reducing Spurious Emissions
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Solution Overview
Problem
Existing radio frequency switch integrated circuits using negative biasing methods face issues with spurious emissions and extended turn-on time, which affect their performance in high power handling and harmonic characteristics.
Innovation Solution
A radio frequency switch apparatus employing a dynamic bias circuit and switch control circuit that generates bias and buffer voltages lower than the battery voltage, using a voltage difference and operational amplifiers, to provide stable gate and body voltages for series and shunt switches, thereby improving switching performance and reducing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If negative biasing method is used to improve power handling and harmonic characteristics, then power handling capability is improved, but spurious emissions increase and turn-on time is extended
Solution Approach 1:
The patent changes the bias voltage parameter from a fixed negative voltage to a dynamically adjusted voltage that transitions from negative to positive during the turn-on period. This parameter change eliminates spurious emissions while maintaining improved power handling capability, as the dynamic voltage adjustment optimizes the switching characteristics of the RF switch throughout the transition period.
Solution Approach 2:
The patent introduces a dynamic biasing mechanism that adjusts the gate voltage over time during switching operations. The bias voltage transitions dynamically from a negative value (during turn-off) to a positive value (during turn-on), which reduces the turn-on time and eliminates spurious emissions while maintaining power handling capability. This dynamic approach replaces the static negative biasing method.
2Power
If negative biasing method is used to improve power handling and harmonic characteristics, then power handling capability is improved, but turn-on time is extended
Solution Approach 1:
The patent introduces a dynamic biasing mechanism that adjusts the gate voltage over time during switching operations. The bias voltage transitions dynamically from a negative value (during turn-off) to a positive value (during turn-on), which reduces the turn-on time and eliminates spurious emissions while maintaining power handling capability. This dynamic approach replaces the static negative biasing method.
Solution Approach 2:
The patent applies a preliminary positive voltage to the gate terminal before the actual switching operation begins. This preliminary action prepares the switch for faster turn-on by pre-charging the gate capacitance, thereby reducing the overall turn-on time while maintaining the power handling benefits of the negative biasing during the off state.
3Device complexity
If fixed bias voltage is used to simplify circuit design, then device complexity is reduced, but insertion loss varies with battery voltage fluctuations
Solution Approach 1:
The patent employs a feedback mechanism that monitors the battery voltage and dynamically adjusts the bias voltage applied to the gate terminal. This feedback control ensures that the insertion loss remains consistent despite battery voltage fluctuations, while the overall circuit design remains relatively simple. The feedback loop compensates for voltage variations automatically.
Solution Approach 2:
The patent introduces an intermediary voltage regulation stage between the battery and the gate terminal. This intermediary circuit (such as a voltage regulator or divider with feedback) decouples the gate bias from direct battery voltage variations, maintaining stable insertion loss characteristics while keeping the overall system design simple and integrated.
Data Source
AI summary
A radio frequency switch apparatus includes a radio frequency switch, a dynamic bias circuit, and a switch control circuit. The radio frequency switch includes a first radio frequency switch circuit connected between a first signal terminal and an input terminal. The first radio frequency switch circuit includes a series switch and a shunt switch. The dynamic bias circuit is configured to generate a bias voltage and a buffer voltage lower than a battery voltage by a preset voltage, using the battery voltage and configured to output the bias voltage to a signal line connected to the input terminal. The switch control circuit is configured to generate first and second gate voltages to switch the first radio frequency switch circuit, based on a band selection signal, using the battery voltage and the buffer voltage.