Load-Switched LNA and Mixer Receiver for Linearity and Noise
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Solution Overview
Problem
Receivers in wireless communication systems face challenges in achieving good linearity and noise performance while minimizing size and cost, as they often require many reactive components and high bias current to meet stringent linearity and noise requirements.
Innovation Solution
A receiver design that includes a low noise amplifier (LNA) with multiple pairs of mixers, where each pair can be selectively enabled or disabled based on operating conditions, using PMOS transistors as internal load and varying the external load to achieve high or low linearity modes, thereby reducing distortion and noise figure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If many reactive components and high bias current are used to meet stringent linearity and noise requirements, then linearity and noise performance are improved, but receiver size, cost, and power consumption increase
Solution Approach 1:
The receiver dynamically switches between different mixer configurations (single pair, multiple pairs, parallel/series arrangements) based on operating conditions such as signal strength and interference levels. This dynamic reconfiguration allows the system to achieve high linearity performance only when needed, rather than being permanently configured for worst-case conditions, thereby reducing overall device complexity and cost.
Solution Approach 2:
The system changes operational parameters by selectively enabling or disabling mixer pairs and altering their configuration based on detected signal conditions. When interference is detected, the system transitions to a high-linearity mode with multiple mixer pairs in parallel; when interference is absent, it switches to a low-linearity mode with fewer active components, thus adapting performance to actual needs rather than maintaining fixed high-performance configuration.
2Reliability
If high bias current is used to meet linearity and noise requirements under worst-case operating conditions, then linearity and noise performance are improved, but power consumption increases
Solution Approach 1:
The receiver dynamically adjusts its power consumption by selectively activating mixer pairs based on operating conditions. The system monitors for interference signals and only engages additional mixer pairs (which consume more power) when interference is detected. During normal operation without interference, fewer mixer pairs are active, significantly reducing power consumption while maintaining adequate performance.
Solution Approach 2:
The system applies partial action by using only the necessary number of mixer pairs required for current operating conditions rather than always using the full complement of mixers. This means using minimal resources (fewer active mixer pairs) during normal operation and only escalating to full resources (all mixer pairs active) when interference requires high linearity performance, thus avoiding excessive power consumption during most operating periods.
3Reliability
If multiple pairs of mixers are always enabled to ensure high linearity performance, then linearity performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The receiver implements dynamic mixer pair selection based on detected signal conditions. The system includes control logic that monitors for interference signals and automatically reconfigures the mixer architecture accordingly. This dynamic approach allows the system to maintain high linearity performance only when interference is present, rather than permanently maintaining complex multi-mixer configurations, thus reducing overall device complexity.
Solution Approach 2:
The mixer pairs are designed to serve multiple functions: they can operate individually or in combination, and can be configured in parallel or series arrangements depending on requirements. This multi-functionality allows the same physical mixer components to provide different levels of linearity performance based on operational needs, eliminating the requirement for dedicated high-linearity circuitry that would be needed if maximum performance were always required.
Data Source
AI summary
A receiver includes a low noise amplifier (LNA) and multiple pairs of mixers. The LNA receives and amplifies an LNA input signal and provides at least one LNA output signal. Each pair of mixers downconverts one of the at least one LNA output signal when enabled. Each pair of mixers may be selectively enabled or disabled, e.g., based on a mode selected from among multiple modes. In one design, the LNA includes multiple load sections coupled in parallel. Each load section may be selectively enabled or disabled, e.g., based on the selected mode. In one design, first and second pairs of mixers and first and second load sections may be enabled for a high linearity mode. The first pair of mixers and the first load section may be enabled and the second pair of mixers and the second load section may be disabled for a low linearity mode.