Passive Mixer and Switched-Capacitor Filter for Low-Noise RF Receivers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Forming satisfactory wireless receiver circuitry in electronic devices is challenging due to excessive power consumption and noise or aliasing in received radio-frequency signals if not properly managed.
Innovation Solution
Incorporating a passive voltage mode mixer and a second-or-higher order passive switched-capacitor filter with synchronized clocking circuitry to downconvert and filter radio-frequency signals, minimizing power consumption and optimizing unwanted signal rejection and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active components are used in the mixer and filter, then signal processing performance is improved, but power consumption increases
Solution Approach 1:
The patent replaces active electronic components (amplifiers, active filters) with passive components (switches, capacitors, resistors) to implement the mixer and filter functions. This substitution of active systems with passive systems reduces power consumption while maintaining signal processing performance through careful timing and synchronization of the switching operations.
Solution Approach 2:
The patent employs periodic switching of capacitors in the filter circuit, where switches are activated in a timed sequence to perform filtering operations. This periodic action allows the passive filter to achieve the desired signal processing performance by dynamically reconfiguring the capacitor network in sync with the mixer operation, eliminating the need for continuously powered active filter components.
2Reliability
If filtering is performed to reduce noise and aliasing, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent combines the mixer and filter functions into a single integrated circuit block, where the switching operations of the mixer and the filtering operations share common capacitors and control timing. This merging of functions reduces the overall device complexity compared to implementing separate mixer and filter circuits, while still achieving effective noise and aliasing reduction through the coordinated switching and filtering actions.
3Use of energy by moving object
If passive components are used to minimize power consumption, then linearity may be degraded, but power efficiency is improved
Solution Approach 1:
The patent incorporates synchronization feedback between the mixer clocking and the filter switching operations. The filter switching is timed to occur in coordination with the mixer LO signals, creating a feedback-like relationship where the timing of one component directly influences the operation of the other. This synchronization ensures that passive components maintain optimal linearity by operating in a coordinated manner that compensates for the inherent non-linearities of passive switching elements.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electronic device may include a receiver that receives radio-frequency signals using an antenna. The receiver may include a passive voltage mode mixer coupled to a passive second-or-higher order switched-capacitor filter with complex poles. Clocking circuitry may provide a control signal to the filter to cycle the filter through a series of states, may provide first and second local oscillator (LO) signals to the mixer, and may synchronize timing of the control signal with the first and second LO signals. The first and second LO signals may have the same period but may be shifted in time by half the period. The period may be equal to the duration with which the filter is placed in each of the states. The clocking circuitry may pulse the first and second LO signals once while the filter is placed in each of the states.