Programmable TX Continuous-Time Filter for Low-Noise Power Scaling
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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 is challenging, as increasing current consumption leads to high battery drain, which is undesirable for maximizing talk and standby time.
Innovation Solution
A programmable-current TX-CTF system that includes amplifier and passive circuitry with programmable bias current control, adjusted by control logic in response to transmitter control signals like modulation mode, band, and power signals, to optimize current consumption and noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TX-CTF current is increased to meet performance requirements (high current drive capability, high linearity, low input referred noise), then noise performance and linearity are improved, but battery current drain increases
Solution Approach 1:
The patent implements dynamic current control by making the bias current programmable and adjustable based on operating conditions. The control logic dynamically selects appropriate current levels for different modulation modes (WCDMA, GSM, EDGE) and operating scenarios, allowing the TX-CTF to achieve required noise performance and linearity only when necessary, thereby reducing average power consumption and extending battery life
Solution Approach 2:
The patent changes the bias current parameter of the TX-CTF based on different operating conditions. By programmatically adjusting the bias current according to modulation mode and performance requirements, the system optimizes the trade-off between noise performance/linearity and power consumption, achieving high reliability only when required while minimizing energy usage during normal operation
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.