RF Square-Law Circuit Bridge Topology
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional high-density voltage-to-current square-law circuits require large capacitors for sufficient settling time and sensitivity, leading to increased die space and noise, making them less compact and less efficient.
Innovation Solution
A compact V/I square-law circuit design that includes a first and second current mirror with a low-pass filter having a filter capacitor coupled between the current mirrors, allowing for a large time constant without the need for large capacitance, achieved by using resistors or transformers to filter out high-frequency components and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large capacitor is used to achieve sufficient settling time and sensitivity, then the filtering performance and sensitivity are improved, but the die space and noise increase
Solution Approach 1:
The patent changes the circuit topology from a single large capacitor to a combination of smaller capacitors with resistors arranged in a bridge configuration. This parameter change allows achieving the same time constant (τ = RC) with smaller individual capacitor values, thereby reducing die space while maintaining sensitivity and filtering performance.
Solution Approach 2:
The patent segments a single large capacitor into multiple smaller capacitors (C1, C2, C3, C4) arranged in a bridge circuit. This segmentation allows the same overall capacitance effect to be achieved with smaller individual components, reducing the total die space required while maintaining the necessary settling time and sensitivity.
2Duration of action of stationary object
If a large capacitor is used to achieve sufficient settling time, then the filtering performance is improved, but the noise and die space increase
Solution Approach 1:
The patent changes the circuit configuration to use resistors in series with smaller capacitors, creating multiple RC time constants in the bridge configuration. This allows achieving the required settling time through the combined RC product without using a single large capacitor, thereby reducing noise while maintaining the necessary duration of action.
3Duration of action of stationary object
If a large capacitor is used to achieve sufficient settling time, then the filtering performance is improved, but the die space and noise increase
Solution Approach 1:
The patent transforms the single large capacitor design into a bridge circuit with multiple smaller capacitors and resistors. The time constant is maintained through the RC product relationship, allowing sufficient settling time to be achieved with smaller individual capacitor values, thus reducing die space while preserving filtering performance.
Solution Approach 2:
The patent divides a single large capacitor into multiple smaller capacitors arranged in a bridge configuration with resistors. This segmentation enables the same overall time constant to be achieved with smaller components, reducing the area occupied on the die while maintaining the necessary settling time for adequate filtering.
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 design achieves a compact and high-fidelity circuit with reduced noise and increased sensitivity, allowing for effective envelope filtering of RF signals while maintaining a low-density design.
Implementation Method 1
a low-pass filter having a filter capacitor coupled between a gate of the first current mirror transistor and the second current mirror transistor
Implementation Method 2
The square law behavior of a metal-oxide semiconductor field effect transistor (MOSFET) may be utilized to recover the envelope from a modulated radio frequency (RF) signal
Data Source
AI summary
A circuit includes a first transistor that conducts a first current responsive to a DC bias voltage and an RF signal. A second transistor conducts a second current responsive to the DC bias voltage. The first current and the second current are mirrored through a pair of current mirrors coupled together through a low-pass filter to filter the envelope of the RF signal.