Switching Current Source RF Oscillator for Ultra-Low Voltage Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF oscillators for IoT devices face challenges in achieving ultra-low power consumption, low voltage operation, small physical size, low cost, and maintaining phase purity, especially when powered by energy harvesters that provide supply voltages lower than standard CMOS circuits.
Innovation Solution
The development of an RF oscillator circuit with a switching current source topology that combines the benefits of low supply voltage operation of conventional NMOS cross-coupled oscillators with high current efficiency of complementary push-pull oscillators, utilizing a two-port resonator with a step-up transformer and tuning capacitors, which reverses tank current direction every half period, reducing power consumption and phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional NMOS cross-coupled oscillators are used, then low supply voltage operation is achieved, but current efficiency is poor
Solution Approach 1:
The oscillator is divided into two separate transistor pairs: a first pair for generating oscillations and a second pair for providing current. This segmentation allows each pair to be optimized for its specific function, with the first pair operating at low voltage and the second pair providing efficient current sourcing, thereby resolving the contradiction between low voltage operation and current efficiency.
Solution Approach 2:
The patent combines the advantages of NMOS cross-coupled oscillators (low voltage operation) with complementary push-pull oscillators (high current efficiency) by merging their functional elements into a unified circuit architecture where both transistor pairs work together to achieve both low power consumption and high current efficiency simultaneously.
2Object-generated harmful factors
If complementary push-pull oscillators are used, then high current efficiency is achieved, but supply voltage requirement increases
Solution Approach 1:
By segmenting the oscillator into two functional pairs, the circuit can operate at lower supply voltages than traditional complementary push-pull oscillators while maintaining high current efficiency through the specialized current-source transistor pair.
Solution Approach 2:
Different parts of the circuit have different functional qualities: the first transistor pair is optimized for low-voltage oscillation generation while the second pair is optimized for efficient current sourcing, allowing the overall circuit to achieve both low voltage operation and high current efficiency.
3Device complexity
If tank current direction is not reversed, then circuit simplicity is maintained, but power consumption increases
Solution Approach 1:
The second transistor pair periodically reverses the tank current direction every half period, creating an alternating current pattern that improves power efficiency by ensuring bidirectional current flow through the resonant tank, which optimizes energy transfer and reduces losses without significantly increasing circuit 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
This solution achieves significantly lower power consumption, improved phase noise, and a better tank Q-factor, allowing the RF oscillator to operate efficiently at ultra-low voltages while maintaining phase purity, suitable for a wide range of IoT applications including phase locked loops and mobile devices.
Implementation Method 1
The resonator comprises a step-up transformer (for example, 1:2) and tuning capacitors at its primary and secondary windings
Implementation Method 2
an LC-tank circuit coupled between the gate terminals of the transistors and drain terminals of the lower pair
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~3D
AI summary
A novel and useful RF oscillator suitable for use in applications requiring ultra-low voltage and power. The oscillator structure, employing alternating current source transistors, combines the benefits of low supply voltage operation of conventional NMOS cross-coupled oscillators together with high current efficiency of the complementary push-pull oscillators. In addition, the 1/f noise upconversion is also reduced. The oscillator can be incorporated within a wide range of circuit applications, including for example a conventional phase locked loop (PLL), all-digital phase-locked loop (ADPLL), wireline transceiver circuits and mobile devices.