Receiver Mixer Filter With Dual Feedback for Out-Band Rejection
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Solution Overview
Problem
Modern RF receivers face challenges in achieving high linearity and rejecting out-band signals while maintaining a low noise figure and cost-effectiveness, particularly in improving the third-order intercept point (IIP3) and requiring simple external low-cost low pass filters (LPF) or band pass filters (BPF).
Innovation Solution
A wireless communication receiver architecture that incorporates a first mixer for frequency conversion and a filter with a negative feedback loop and a positive capacitive feedback loop in parallel, allowing for effective band pass filtering and improved linearity, using NMOS transistors and operational amplifiers to generate I/Q channel signals with tunable Q factor and filter characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If higher order BPF is used to reject out-band signals, then out-band rejection is improved, but device cost increases due to numerous off-chip BPF
Solution Approach 1:
The patent combines multiple filter functions into a single integrated filter structure with parallel feedback loops. The first filter includes both negative feedback loop and positive capacitive feedback loop operating in parallel to achieve higher order filtering performance, eliminating the need for multiple separate off-chip BPF components and reducing device cost.
Solution Approach 2:
The patent implements nested feedback structures where the positive capacitive feedback loop is embedded within the overall filter architecture that also includes the negative feedback loop. This nested arrangement creates a multi-loop system that achieves higher order filtering characteristics while using a single integrated filter component rather than multiple external filters.
2Reliability
If complex filter architecture is used to achieve high linearity, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent employs dual feedback loops - a negative feedback loop and a positive capacitive feedback loop - to improve linearity. The negative feedback reduces distortion by opposing signal variations, while the positive capacitive feedback enhances selectivity and Q-factor. This feedback mechanism achieves high linearity through control theory rather than complex passive component arrangements.
Solution Approach 2:
The patent achieves linearity improvement by dynamically adjusting circuit parameters through the feedback loops, particularly by modifying the effective impedance and gain characteristics. The positive capacitive feedback loop changes the resonant frequency and Q-factor parameters, allowing the filter to maintain optimal linearity performance across varying operating conditions without requiring a complex fixed architecture.
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
The solution achieves better out-band rejection and linearity with negligible noise figure degradation, enabling higher-order filter performance and cost-effective implementation by tuning the gains of the operational amplifier and attenuator, thus enhancing the receiver's ability to handle in-band signals while attenuating unwanted out-band signals.
Implementation Method 1
a first mixer, coupled to the antenna, for performing frequency conversion on the received wireless communication signal from the antenna by mixing the wireless communication signal with a local oscillator signal to provide a first intermediate frequency (IF) signal
Implementation Method 2
a negative feedback loop coupled to the first mixer for performing negative feedback loop control on the first IF signal from the first mixer
Implementation Method 3
a positive capacitive feedback loop coupled to the first mixer for performing positive capacitive feedback loop control on the first IF signal from the first mixer
Data Source
AI summary
Provided is a wireless communication receiver including an antenna for receiving an RF signal; a first mixer, coupled to the antenna, for performing frequency conversion on the RF signal from the antenna by mixing the RF signal with a local oscillator signal to provide a first intermediate frequency (IF) signal; and a first filter, coupled to the first mixer, configured to pass a predetermined band of frequencies of the first IF signal and to generate a first channel signal. The first filter includes a negative feedback loop coupled to the first mixer for performing negative feedback loop control on the first IF signal; and a positive capacitive feedback loop coupled to the first mixer for performing positive capacitive feedback loop control on the first IF signal, the negative feedback loop and the positive capacitive feedback loop being coupled in parallel.