CMOS Gilbert Mixer With Current Bleeding for Low Flicker Noise
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Solution Overview
Problem
CMOS mixers in direct conversion receivers face challenges in improving conversion gain and linearity while reducing flicker noise, with existing solutions either introducing additional noise, requiring high LO power, or being unsuitable for wideband applications due to high LNA gain and poor gain flatness.
Innovation Solution
A mixer design incorporating a current bleeding circuitry with two inductors to resonate parasitic capacitance, reducing LO switching current and flicker noise, and enhancing conversion gain, while maintaining low LO power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If static current bleeding circuitry is used to reduce flicker noise, then flicker noise is reduced, but additional flicker noise occurs from the current bleeding circuitry and conversion gain decreases
Solution Approach 1:
The patent employs dynamic current bleeding circuitry where PMOS transistors are controlled by a dynamic control signal that switches between first and second voltage levels. This dynamic control allows the circuit to adaptively manage the bleeding current, reducing flicker noise while maintaining conversion gain through optimal timing and voltage control of the bleeding operation.
Solution Approach 2:
The patent changes the voltage parameter at the gate of PMOS transistors by applying a dynamic control signal with varying voltage levels. This parameter change enables the PMOS transistors to function as controllable switches that can dynamically adjust the bleeding current, resolving the contradiction between noise reduction and gain maintenance.
2Object-affected harmful factors
If dynamic current bleeding circuitry is used to reduce flicker noise, then flicker noise is reduced, but very high LO power is required to generate high voltage at gate nodes
Solution Approach 1:
The patent introduces an intermediary voltage boosting circuit that includes NMOS transistors and capacitors to generate the high voltage needed for PMOS gate control. This intermediary circuit acts as a mediator between the LO signal and the PMOS gate nodes, providing the necessary voltage swing without requiring proportionally high LO power, thus reducing the direct power consumption relationship.
Solution Approach 2:
The dynamic current bleeding operation is performed periodically synchronized with the LO signal cycles. The control signal switches between voltage levels at specific phases of the LO signal, enabling noise reduction during critical periods while allowing power recovery during other phases, thereby reducing average LO power consumption.
3Object-affected harmful factors
If LO switch size is increased to reduce inherent flicker noise, then flicker noise is reduced, but parasitic capacitance increases and more RF currents are shunted to ground
Solution Approach 1:
The patent uses dynamic control of PMOS transistors to achieve current bleeding only during specific phases of the LO signal. This dynamic operation allows the use of smaller LO switches that would otherwise be too small to provide sufficient noise reduction, because the effective noise reduction is achieved through timing-controlled current steering rather than relying solely on large device size.
Solution Approach 2:
The current bleeding operation is performed periodically in synchronization with the LO signal phases. During specific phases when the switching devices are naturally off or less critical, the PMOS transistors shunt current to reduce flicker noise. This periodic operation allows smaller switches to achieve the same noise reduction effect without continuous high parasitic capacitance penalties.
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 proposed mixer achieves a 17 dB conversion gain with significantly reduced flicker noise, improved linearity, and lower LO power consumption, making it suitable for wideband applications.
Implementation Method 1
A mixer design incorporating a current bleeding circuitry with two inductors to resonate parasitic capacitance
Data Source
AI summary
Provided is a mixer for use in a direct conversion receiver. The mixer includes Field Effect Transistors (FETs), a current source (IBias), two load resistors (RLoad), another FET, and two inductors L1 and L2. The FET M21 constitutes a current bleeding circuitry and the other components except for the two inductors L1 and L2 constitute a so-called Gilbert cell mixer.