Attenuator Voltage Circuit for Linear dB Control Under PVT Variation
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Solution Overview
Problem
Existing voltage generating circuits for attenuators in RF transceivers produce non-linear attenuation characteristics, which affect receiver performance and are process-voltage-temperature (PVT) dependent, requiring higher resolution from digital-to-analog converters (DACs).
Innovation Solution
A voltage generating circuit that includes a digital-to-analog converter (DAC) providing differential currents, coupled with transistors and isolation circuits to generate non-linear voltages that control an attenuator, resulting in linear attenuation characteristics in decibels, independent of PVT variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If linear voltages are used to control the attenuator, then the control is simple, but the attenuation characteristics become non-linear in decibels
Solution Approach 1:
The patent changes the functional relationship between control voltage and current by introducing non-linear circuits (transistor-based circuits with specific configurations of resistors and transistors). These circuits transform the linear control voltage into non-linear control currents that, when applied to the attenuator, produce linear attenuation characteristics in decibels. This parameter transformation resolves the contradiction by maintaining control simplicity while achieving the desired attenuation linearity.
2Manufacturing precision
If non-linear voltages are generated to achieve linear attenuation, then attenuation linearity improves, but circuit complexity increases
Solution Approach 1:
The patent divides the voltage generation function into multiple independent non-linear circuits, each responsible for generating control voltages for specific attenuator segments. This segmentation allows each circuit to be optimized independently and simplifies the overall control architecture, reducing the complexity burden while maintaining attenuation linearity across the full range.
Solution Approach 2:
The patent introduces intermediate non-linear conversion circuits that act as mediators between the simple linear voltage source and the attenuator. These intermediary circuits perform the non-linear transformation required to achieve linear attenuation, effectively decoupling the simplicity of the voltage source from the linearity requirement of the attenuator performance.
3Measurement precision
If higher resolution DAC is used to compensate for non-linear characteristics, then attenuation precision improves, but device complexity and cost increase
Solution Approach 1:
The patent changes the transfer function of the voltage-to-current conversion stage to compensate for the attenuator's non-linear characteristics. By designing the conversion circuit with a specific non-linear relationship (using transistor parameters and resistor ratios), the system achieves linear attenuation with a standard-resolution DAC, eliminating the need for higher resolution converters and reducing overall system complexity.
4Device complexity
If control voltages are directly applied to the attenuator, then the circuit is simple, but PVT dependence degrades performance
Solution Approach 1:
The patent incorporates feedback mechanisms within the non-linear voltage generation circuits, where the transistor operating points are established through self-biasing configurations. These feedback loops automatically compensate for PVT variations by adjusting the transistor operating conditions, ensuring stable attenuation characteristics across process, voltage, and temperature ranges while maintaining circuit simplicity.
Solution Approach 2:
The non-linear conversion circuits are designed to be self-regulating, using the inherent characteristics of the transistors and resistors to automatically compensate for PVT variations. The circuits serve themselves by utilizing the physical relationships between components to maintain correct operating points without external calibration or complex compensation networks, achieving PVT independence with minimal added complexity.
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 solution achieves linear attenuation characteristics, enhancing receiver performance and reducing the need for higher DAC resolution, while isolating the circuit from input signal interference.
Implementation Method 1
A digital-to-analog converter (DAC) provides a first current at a first output terminal of the DAC and a second current at a second output terminal of the DAC. The first current is differential to the second current.
Implementation Method 2
The first circuit generates a first voltage and a second voltage. The first voltage is non-linear with respect to the first current and the second voltage is non-linear with respect to the second current.
Implementation Method 3
The circuit includes first isolators and second isolators. The first isolators prevent a signal at a first node from interfering with a signal at a second node. The second isolators prevent a signal at the second node from interfering with a signal at a third node.
Data Source
AI summary
A circuit includes a digital-to-analog converter (DAC), coupled to a power supply, that provides a first current at a first output terminal of the DAC and a second current at a second output terminal of the DAC, the first current being differential to the second current; a first circuit, coupled to the first output terminal of the DAC and to the second output terminal of the DAC, that generates a first voltage and a second voltage, the first voltage being non-linear with respect to the first current and the second voltage being non-linear with respect to the second current; and an attenuator coupled to the first circuit, and responsive to the first voltage and the second voltage to attenuate an input signal of the attenuator and to generate linear attenuation characteristics in decibels with respect to the first current and the second current.