Programmable TX-CTF Current Scaling for Linearity and Battery Life
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Solution Overview
Problem
Designing a transmit continuous-time filter (TX-CTF) for multi-mode cellular handsets that meets performance criteria such as high current drive capability, high linearity, low input referred noise, and low bandpass ripple while minimizing current consumption to extend battery life and reduce battery size is challenging, as increasing current consumption leads to high battery drain.
Innovation Solution
A programmable-current TX-CTF system with amplifier and passive circuitry that adjusts bias current based on transmitter control signals, including modulation mode, band, and power signals, to optimize performance according to operating conditions, using passive upconversion mixers to reduce power consumption and maintain linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high current is used in TX-CTF, then current drive capability and linearity are improved, but battery current drain increases
Solution Approach 1:
The patent implements a programmable current TX-CTF where the bias current can be dynamically adjusted based on operating conditions. The system includes a current control mechanism that programs the bias current to different levels depending on the required performance, allowing the filter to adapt between high current (for high linearity and drive capability) and low current (for battery conservation) modes, thus resolving the contradiction between reliability and energy consumption
Solution Approach 2:
The patent changes the bias current parameter of the TX-CTF based on operating conditions. By programmatically adjusting the bias current level, the system can optimize performance for different modulation modes and power requirements while minimizing average current consumption, directly addressing the contradiction between maintaining high current drive capability and reducing battery drain
2Reliability
If high current is used in TX-CTF, then linearity is improved, but battery current drain increases
Solution Approach 1:
The system dynamically adjusts the bias current based on the required linearity performance. When high linearity is needed (such as during high-power transmission or specific modulation modes), the bias current is increased. When lower linearity is acceptable, the bias current is reduced, thus maintaining linearity performance when required while minimizing battery current drain during normal operation
Solution Approach 2:
The bias current parameter is programmatically changed according to operating conditions and performance requirements. This allows the system to achieve high linearity only when required by operating conditions, rather than maintaining maximum linearity at all times, thereby reducing average power consumption while meeting linearity specifications when needed
3Duration of action of moving object
If TX-CTF current consumption is minimized, then battery life is extended, but current drive capability is reduced
Solution Approach 1:
The programmable current TX-CTF allows the system to switch between low current consumption mode (extending battery life) and high current drive mode (providing sufficient current drive capability) based on real-time operating conditions. The control mechanism ensures that high current drive capability is available when needed while minimizing current consumption during normal operation, thus extending battery life without permanently reducing current drive capability
Solution Approach 2:
The bias current parameter is adjusted based on the required current drive capability. During normal operation, lower current is used to extend battery life. When high current drive capability is required (such as during power amplification or specific transmission modes), the bias current is increased to provide the necessary drive capability, thus resolving the contradiction between battery life extension and maintaining current drive capability
4Quantity of substance
If TX-CTF current consumption is minimized, then battery size can be reduced, but current drive capability is reduced
Solution Approach 1:
The system uses dynamic current adjustment to allow for smaller battery size while maintaining adequate current drive capability. By programming the bias current to be high only when necessary and low during normal operation, the system reduces the average current requirements, enabling the use of a smaller battery while still providing high current drive capability when required by transmission conditions
Data Source
AI summary
A programmable-current transmit continuous-time filter (TX-CTF) system can be included in a radio frequency (RF) transmitter. The input of the TX-CTF can receive a baseband transmission signal, and the output of the TX-CTF can be provided to an upconversion mixer for conversion to RF for transmission. The TX-CTF includes amplifier circuitry and passive circuitry that together define the filter parameters. The TX-CTF further includes programmable current circuitry that provides a programmable bias current to the amplifier circuitry. The TX-CTF system also includes control logic that receives one or more transmitter control signals and, in response, generates signals that control the bias current provided to the TX-CTF.