Direct-Conversion Receiver Circuit for Shared Gain and DC Offset Control
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Solution Overview
Problem
Direct conversion receivers face challenges with offset voltage control, requiring separate gain for DC levels across different frequencies, leading to increased component count and board area, and limiting the integration of automatic gain control due to large capacitors needed for frequency cutoff.
Innovation Solution
A receiver with a common gain control circuit and DC offset cancelling circuit, utilizing an inverting amplifier with a reference signal to adjust output DC levels independently of input DC levels, allowing for a fully integrated automatic gain control without discrete components and reducing silicon area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate gain control circuits are used for different frequency bands, then the DC offset control is improved, but the device complexity and board area increase
Solution Approach 1:
The patent combines multiple gain control circuits for different frequency bands into a single shared gain control circuit. The baseband signal processing stage applies common gain control to I and Q signals across all frequency bands, eliminating the need for separate gain control circuits per band. This merging reduces component count while maintaining DC offset control through the shared circuit's ability to handle baseband signals from multiple bands.
Solution Approach 2:
The shared gain control circuit is designed to universally handle baseband signals from multiple frequency bands simultaneously. The circuit performs multi-functional gain control for I and Q signals across different bands without requiring band-specific customization, thereby reducing overall system complexity while maintaining effective DC offset management.
2Measurement precision
If large capacitors are used for frequency cutoff, then the DC level control is improved, but the device area and integration difficulty increase
Solution Approach 1:
The patent replaces the traditional mechanical/electrical approach of using large physical capacitors for frequency cutoff with a digital signal processing approach. The DC level control is achieved through digital processing of baseband signals, eliminating the need for large analog capacitors. This substitution dramatically reduces board area while maintaining precise DC level control through software-based filtering and processing.
3Ease of manufacture
If discrete components are used for gain control, then the manufacturing flexibility is improved, but the manufacturing cost and device complexity increase
Solution Approach 1:
The patent merges multiple discrete gain control functions into a single integrated baseband processing stage. Instead of implementing separate gain control circuits for each frequency band using discrete components, the invention uses a unified digital processing approach that handles all bands simultaneously. This integration maintains manufacturing flexibility through programmable control while dramatically reducing the total number of discrete components required.
Solution Approach 2:
The patent changes the operating parameters from analog discrete component-based gain control to digital parameter-based control. Gain control is achieved by modifying digital signal processing parameters rather than adjusting analog component values. This parameter change enables flexible manufacturing through software configuration while reducing the need for precision discrete components and complex assembly procedures.
Data Source
AI summary
A receiver and a method for a receiver is disclosed. The receiver comprises a signal processing path for receiving a first signal modulated by a first modulation method and having a first bandwidth and a second signal modulated by a second modulation method and having a second bandwidth. A common gain control function is provided for processing said first and second signals. A common DC offset cancellation is also provided for said first and second signals. In a preferred embodiment the gain control and the DC offset cancellation a provided by a single circuit.