Polyphase Quadrature Clock Generation With Lower Phase Noise
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Solution Overview
Problem
Existing quadrature signal generation methods for memory systems, such as DDR memory systems, face challenges including increased size, power consumption, and phase noise due to the use of divide-by-two circuits and dual oscillators, which can lead to high phase noise and tuning difficulties.
Innovation Solution
A quadrature signal generator that uses a filter bank, specifically a polyphase filter, to generate quadrature clock signals at the same frequency as the input clock signals, reducing the need for the clock generator's operating frequency to be twice that of the desired frequency, and incorporating a duty cycle and phase adjuster to optimize signal quality within a wideband frequency range of 2.5 GHz to 5 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a divide-by-two circuit with an oscillator at twice the desired frequency is used to generate quadrature signals, then quadrature clock signals can be generated, but phase noise increases and power consumption increases
Solution Approach 1:
The patent changes the operating frequency parameter from twice the desired frequency to the same frequency, eliminating the need for frequency multiplication and subsequent division. This parameter change directly reduces phase noise while maintaining quadrature signal generation capability.
Solution Approach 2:
The patent extracts and removes the divide-by-two circuit from the system architecture. By using a filter bank instead, the harmful frequency division operation that introduces phase noise is eliminated while the quadrature signal generation function is preserved.
2Reliability
If a PLL with two coupled local oscillators is used to generate quadrature signals, then quadrature clock signals can be generated, but inductor area increases
Solution Approach 1:
The patent removes the dual oscillator architecture and its associated large inductors from the system. By replacing it with a filter bank approach operating at the same frequency, the inductor area is dramatically reduced while maintaining quadrature signal generation.
Solution Approach 2:
The patent merges the frequency generation and quadrature signal generation functions into a single stage operating at the desired frequency, eliminating the need for separate oscillators and reducing the overall inductor area requirement.
3Reliability
If the clock generator operates at twice the desired frequency to generate quadrature signals, then quadrature clock signals can be generated, but power consumption increases
Solution Approach 1:
The patent changes the operating frequency parameter from twice the desired frequency to the same frequency. This parameter change reduces the power consumption of the clock generator while maintaining the ability to generate quadrature signals through the filter bank.
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 approach reduces phase noise, power usage, and inductor area requirements, while maintaining high bandwidth capabilities, effectively addressing the limitations of previous methods by generating quadrature clock signals that meet the high bandwidth demands of modern memory systems without increasing the operating frequency of the clock generator.
Implementation Method 1
A quadrature signal generator that uses a filter bank, specifically a polyphase filter, to generate quadrature clock signals at the same frequency as the input clock signals
Data Source
AI summary
Apparatuses and methods for quadrature signal generation are provided. An example includes a quadrature signal generator. The quadrature signal generator is configured to generate, based on a received differential signal, a plurality of quadrature clock signals at a same frequency as that of the received differential signal. The quadrature signal generator is also configured to provide the plurality of quadrature clock signals to a memory system.