Low IF Receiver Digital Gain Phase Imbalance Compensation
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Solution Overview
Problem
Current radio receivers, particularly those using direct conversion and low intermediate frequency systems, face challenges with DC offset and self-generated interferers, which degrade signal quality and increase complexity and cost, especially in EDGE modulation and GSM/EDGE systems.
Innovation Solution
A low intermediate frequency receiver system that digitally estimates and compensates for gain and phase imbalances, and repositions adjacent channel interferers by inverting the local oscillator signal, thereby reducing RF impairments and minimizing the impact of DC offset and 1/f noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct conversion receiver (DCR) systems are used to simplify receiver architecture, then device complexity is reduced, but DC offset and self-generated interferers degrade signal quality
Solution Approach 1:
The patent extracts and removes the harmful DC offset component from the received signal by detecting and subtracting it in the digital domain, separating the desired signal from the interfering DC component that arises in direct conversion receiver architectures
Solution Approach 2:
The patent implements a feedback mechanism where the receiver detects the DC offset level and interferer characteristics, then uses this information to dynamically adjust and compensate for these impairments, creating a closed-loop system that continuously mitigates the harmful effects
2Object-affected harmful factors
If conventional IF-based radios use high IF frequencies to ensure image frequency rejection, then signal quality is improved, but expensive filtering components and additional mixer hardware increase device complexity and cost
Solution Approach 1:
The patent replaces the traditional analog mechanical filtering approach with digital signal processing techniques, using digital algorithms to reject image frequencies and interferers instead of physical filters and additional mixer stages
Solution Approach 2:
The patent changes the intermediate frequency parameter to a low IF value and uses digital processing to achieve the same image rejection that would traditionally require high IF frequencies and complex analog filtering, fundamentally altering the frequency domain parameters of the receiver
3Object-affected harmful factors
If averaging and subtraction processes are used to remove DC offset in DCR systems, then DC offset is reduced, but the phase randomization in TDMA systems makes long term averaging difficult and increases processing complexity
Solution Approach 1:
The patent performs DC offset detection and compensation during specific time intervals within the TDMA frame structure, preparing and storing compensation values in advance for use during signal reception, rather than attempting continuous averaging across randomly phased bursts
4Object-affected harmful factors
If semiconductor manufacturers use fabrication processes with good 1/f noise characteristics to reduce low frequency noise, then signal quality is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts and removes the low frequency noise component from the signal path through digital filtering and processing techniques, eliminating the need for expensive specialized fabrication processes designed to minimize 1/f noise at the manufacturing stage
Data Source
AI summary
Embodiments of a low intermediate frequency system and method are disclosed. In one embodiment, among others, a method for operating a receiver is disclosed that comprises receiving a radio frequency signal, downconverting the radio frequency signal to a downconverted signal comprising an in-phase component and quadrature component, and estimating a gain and phase imbalance between the in-phase component and the quadrature component.