Multi-Mode Delta-Sigma ADC for Blocker-Resistant IF Reception
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Solution Overview
Problem
High-frequency analog-to-digital converters face challenges with out-of-band signal transfer function peaking, particularly in applications like TV broadcasting, where close-in blockers can destabilize the ADC and reduce in-band dynamic range, and existing solutions like baseband or intermediate frequency filters are insufficient.
Innovation Solution
A delta-sigma modulator configurable in low-pass and band-pass filter modes, with selection logic and adjustable integrator gains to manage signal processing paths, reducing out-of-band signal transfer function peaking by disabling specific integrators based on control signals, thereby optimizing performance across different intermediate frequency modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a baseband or intermediate frequency filter is used to reduce close-in blockers, then the ADC stability is improved, but the in-band dynamic range is reduced
Solution Approach 1:
The patent changes the order parameter of the delta-sigma modulator based on the operating mode. In LIF mode, a fifth-order modulator is used with all integrators enabled to maximize dynamic range. In standard IF mode, a fourth-order modulator is used with the fifth integrator disabled to reduce out-of-band STF peaking and improve stability against close-in blockers. This dynamic reconfiguration of the modulator order allows the system to optimize both stability and dynamic range according to the specific operating conditions.
2Reliability
If the ADC input level is increased to ensure residual blockers do not overload the ADC, then the ADC stability is improved, but the in-band dynamic range is reduced
Solution Approach 1:
Instead of increasing the ADC input level to handle blockers, the patent changes the modulator order parameter to reduce out-of-band STF peaking. By disabling the fifth integrator in standard IF mode, the system reduces the amplification of out-of-band signals, thereby preventing blocker overload without sacrificing in-band dynamic range. This approach addresses the stability issue through structural modification rather than level adjustment.
3Device complexity
If distributed feed-forward topology is used to reduce internal signal swings and use fewer feedback DACs, then device complexity is reduced, but out-of-band signal transfer function peaking is increased
Solution Approach 1:
The patent introduces dynamic reconfiguration capability to the distributed feed-forward topology by making the integrator enablement status controllable based on operating mode. The system can dynamically switch between enabling all integrators (fifth-order) for LIF mode and disabling the fifth integrator (fourth-order) for standard IF mode. This dynamic adaptation allows the simplified DFF topology to achieve low out-of-band STF peaking when needed while maintaining its complexity advantages.
4Stability of the object's composition
If more aggressive loop scaling is done in multi-bit quantizer delta-sigma modulators, then loop stability is improved, but out-of-band signal transfer function peaking is increased
Solution Approach 1:
The patent addresses the trade-off between loop stability and out-of-band STF peaking by changing the modulator order parameter rather than adjusting loop scaling. By reducing the modulator order from fifth to fourth in standard IF mode through disabling the fifth integrator, the system achieves reduced out-of-band STF peaking while maintaining adequate loop stability through the remaining four integrators and the multi-bit quantizer structure.
Data Source
AI summary
A method of configuring an analog-to-digital converter (ADC) includes configuring the ADC to operate in one of a low-pass filter mode and a band-pass filter mode according to a value of a control signal. In at least one embodiment, the method further includes configuring an integrator gain of the ADC and a feed-forward gain of the ADC based on selection of one of a low-intermediate frequency (LIF) mode and a zero-intermediate frequency (ZIF) mode.