Current-Domain Low-Pass Filter for Linear Out-of-Band Attenuation
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Solution Overview
Problem
Existing filters in receivers, such as DVB receivers, face challenges in effectively attenuating out-of-band noise and interference while maintaining high linearity for both in-band and out-of-band signals, and require additional filtering capabilities while consuming reduced power and being adaptable to multi-standard systems.
Innovation Solution
A second-order low pass filter operating in the current domain with high linearity, featuring tunable components and a programmable capacitor array, allowing for adjustable filtering characteristics and stackable configurations to suit various standards, comprising a MOS transistor, capacitors, and a bias resistor with a constant product of resistance and trans-conductance for easy control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional filters are used to attenuate out-of-band noise and interference, then filtering capability is provided, but linearity for both in-band and out-of-band signals deteriorates
Solution Approach 1:
The filter is divided into multiple cascaded stages, each contributing to the overall filtering function. This segmentation allows each stage to be optimized for specific performance characteristics, achieving both high out-of-band attenuation and maintained linearity through the cumulative effect of multiple controlled stages.
Solution Approach 2:
The filter employs tunable components including variable resistors and variable capacitors that allow dynamic adjustment of filter characteristics. This enables the filter to adapt its response to maintain optimal linearity and attenuation performance across different operating conditions and signal types.
2Object-affected harmful factors
If additional filtering capabilities are added to the receiver, then out-of-band attenuation is improved, but power consumption increases
Solution Approach 1:
The filter replaces traditional voltage-mode active filters with a current-mode implementation. This substitution inherently provides higher linearity and reduces the need for additional power-consuming active components, achieving improved filtering capability with reduced power consumption.
Solution Approach 2:
The filter uses tunable components including variable resistors and variable capacitors that allow optimization of the filter's Q-factor and cutoff frequency. By adjusting these parameters, the filter achieves high out-of-band attenuation with minimal power consumption by operating at optimal points for each filtering requirement.
3Adaptability or versatility
If the filter is made adaptable to multi-standard systems through tunable components, then versatility is improved, but device complexity increases
Solution Approach 1:
The filter incorporates a universal design with tunable components including variable resistors and variable capacitors that allow a single filter circuit to be configured for multiple broadcasting standards (DVB-T, DVB-T2, ISDB-T, ATSC). This multi-functionality is achieved through programmable capacitor arrays and bias control that enable the same hardware to adapt to different frequency ranges and filtering requirements.
Solution Approach 2:
The filter uses programmable capacitor arrays that can be configured to replicate different capacitance values digitally controlled. This allows the filter to copy the electrical characteristics needed for different broadcasting standards without requiring separate physical filter circuits for each standard, reducing overall system complexity while maintaining versatility.
Data Source
AI summary
Aspects of the disclosure can provide a second order low pass filter. The second order low pass filter can work in current domain, and have high linearity for in-band signals and out-of-band signals. The second order low pass filter can include a MOS transistor having a gate terminal, a current input terminal and a current output terminal, a first capacitor coupled between the current input terminal and a ground connection and a second capacitor coupled between the gate terminal and the current input terminal.