Variable Resistive Attenuator for RFIC Noise and Board Area Limits
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Solution Overview
Problem
The integration of a piezoelectric bandpass filter (BPF) with a radio frequency integrated chip (RFIC) in mobile communication devices is limited by practical constraints, leading to increased costs and board area, and results in noise degradation due to power amplifier gain variations, which is particularly challenging in GSM networks with stringent noise requirements.
Innovation Solution
An on-chip variable resistive attenuator is used to replace the off-chip BPF, allowing for adjustable attenuation of the RFIC output power to maintain acceptable noise performance without the need for a SAW filter, thereby reducing power consumption and noise leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an off-chip bandpass filter (SAW filter) is used to reduce receiver band noise, then noise performance is improved, but board area and cost increase
Solution Approach 1:
The patent merges the bandpass filter functionality with the power amplifier by integrating a variable resistive attenuator directly into the PA circuitry. This integration eliminates the need for a separate off-chip SAW filter, reducing board area while maintaining noise performance through the attenuator's ability to control gain variation.
Solution Approach 2:
The variable resistive attenuator serves multiple functions: it acts as both a gain control element for the power amplifier and a noise filter for the receiver band. This multi-functionality replaces the dedicated SAW filter, achieving noise reduction without requiring additional board space.
2Power
If power amplifier gain is increased to compensate for noise degradation, then output power is improved, but noise leakage increases
Solution Approach 1:
The patent employs a variable resistive attenuator that dynamically adjusts its attenuation level based on operating conditions. This dynamic control allows the system to optimize the balance between output power and noise leakage by varying the attenuation in response to gain variations in the power amplifier.
Solution Approach 2:
The variable resistive attenuator changes its resistance parameter to control the amount of attenuation applied to the RF signal. By adjusting this parameter, the system can compensate for power amplifier gain variations while maintaining controlled noise leakage levels.
3Power
If an external attenuator is used to reduce output power, then power amplifier over-driving is prevented, but relative noise level degrades
Solution Approach 1:
The variable resistive attenuator acts as an intermediary element between the driver amplifier and the power amplifier. It provides controlled attenuation that prevents power amplifier over-driving while minimizing the impact on relative noise level through its specific resistance configuration and control mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution achieves a 0.15 dB degradation in receiver band noise for every 1.0 dB reduction in RFIC output power, allowing for the desired noise level to be maintained without the insertion loss of a SAW filter, thus reducing power consumption and noise leakage.
Implementation Method 1
An on-chip variable resistive attenuator is used to replace the off-chip BPF, allowing for adjustable attenuation of the RFIC output power
Data Source
AI summary
Disclosed are circuits, techniques and methods for implementing an attenuator in a signal transmission path. In one particular implementation, an attenuation may be adjusted based, at least in part, on a control signal. In another implementation, such an attenuation may be adjusted in coarse increments by varying one or more gate voltages applied one or more transistors. In yet another implementation, adjusting said attenuation in fine increments by varying a bias voltage applied to at least one level shifter.