Tunable Bandpass LNA Using Multi-N-Path Filters for Blocker Rejection
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Solution Overview
Problem
Existing wireless communication systems face challenges in mitigating cross talk and signal leakage between transmit and receive streams due to shared antenna infrastructure, leading to performance limitations in multi-channel transceivers, particularly with high-order analog baseband filters and N-path mixers that are sensitive to process variations and require extensive redesign.
Innovation Solution
A digitally tunable bandpass low-noise amplifier (LNA) incorporating multiple N-path filters driven by different local oscillator signals, controlled by a frequency synthesizer, to achieve precise bandwidth and center frequency tuning with minimal analog component tuning, enhancing blocker rejection and isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-order analog baseband gm-C filters are used to achieve higher order filtering, then filtering performance is improved, but process sensitivity increases and requires extensive overdesign leading to power penalty
Solution Approach 1:
The patent replaces the mechanical/analog tuning system with a digital control system. Multiple N-path filters are controlled by digital signals that selectively connect different capacitive elements, allowing precise filtering performance without the sensitivity issues of analog gm-C filters. The digital control mechanism eliminates the need for extensive analog overdesign.
Solution Approach 2:
The patent changes the control parameters from analog continuous tuning to digital discrete selection. By using digitally controlled capacitive elements in N-path filters, the system achieves high-order filtering with fixed, predetermined characteristics that are insensitive to process variations, eliminating the need for extensive overdesign.
2Adaptability or versatility
If extensive tuning of capacitors, resistors, transistor sizes, and bias currents is performed to achieve high tunable range in bandwidth, then bandwidth tunability is improved, but manufacturing complexity and power consumption increase
Solution Approach 1:
The patent implements dynamic bandwidth tuning through digital control of N-path filter configurations. Multiple N-path filters with different bandwidth characteristics are selectively activated or deactivated based on digital control signals, enabling continuous bandwidth adjustment without physical component changes or complex analog tuning circuits.
Solution Approach 2:
The patent creates a universal filtering solution where a single N-path filter structure can operate at multiple bandwidths by digitally selecting different capacitive elements. This multi-functional approach eliminates the need for separate tuned circuits for different bandwidth requirements, reducing overall device complexity.
3Object-affected harmful factors
If single-frequency N-path mixers are used to achieve far-out rejection, then blocker rejection is improved, but isolation between filters is limited and tuning flexibility is reduced
Solution Approach 1:
The patent segments the filtering function into multiple independent N-path filters, each optimized for specific frequency ranges and bandwidths. This segmentation allows each filter to provide superior blocker rejection in its designated range while the collective system achieves broad tuning flexibility through digital selection and combination of different filter segments.
Solution Approach 2:
The patent creates a composite filtering system by combining multiple N-path filters with different characteristics. The composite structure leverages the strengths of individual filters to achieve both superior blocker rejection and broad tuning flexibility, with digital control enabling optimal combination of filter responses for different operating conditions.
Data Source
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Figure 2A
AI summary
A tunable bandpass low-noise amplifier (LNA). The LNA includes a plurality of N-path filters and a plurality of cascode amplifiers. The cascode amplifiers are configured to amplify an input signal. Each N-path filter is coupled to a different one of the plurality of cascode amplifiers. The plurality of N-path filters are driven by local oscillator (LO) signals having different frequencies, and output nodes of the plurality of cascode amplifiers are coupled in parallel. The frequencies of the LO signals may be symmetrically spaced around a desired frequency (fLO). Each N-path filter may be coupled to a source of the common-gate device of the coupled cascode amplifier. The LO signals may be generated by a digital-to-time converter (DTC)-based frequency synthesizer. The frequencies of the LO signals supplied to the N-path filters may be adjusted to tune the bandwidth of the bandpass LNA.