Buffered Clock Distribution for RF Noise Isolation
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Solution Overview
Problem
Mobile wireless communications devices face performance degradation due to spurious signals and jitters caused by digital noise from the microprocessor, which shares a clock with RF circuits without proper buffering, leading to failed RF specifications.
Innovation Solution
Incorporating clock buffer circuitry on the circuit board to isolate the clock signal from microprocessor noise, using a plurality of serially connected buffers providing 40 to 80 decibels of reverse isolation, and connecting sensitive RF circuits like GSM/GPRS chipsets directly to the crystal oscillator with impedance matching, while less sensitive components like Bluetooth modules receive isolated clock signals through buffer circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the microprocessor and RF circuits share the same clock signal without buffering, then device complexity is reduced, but digital noise from the microprocessor degrades RF performance causing spurious signals and jitters
Solution Approach 1:
The patent introduces buffer circuits as intermediary components between the crystal oscillator and the microprocessor/RF circuits. These buffers act as mediators that isolate the clock signal from digital noise generated by the microprocessor, preventing noise from coupling into the RF circuits while still distributing the clock signal to all necessary components.
Solution Approach 2:
The patent segments the clock distribution network into separate buffered paths for different circuits. Instead of a single shared clock line, the system divides the clock distribution into multiple isolated channels using buffer circuits, allowing independent control and noise isolation for each recipient circuit.
2Reliability
If buffer circuits are added to isolate the clock signal, then RF performance is improved by reducing digital noise, but device complexity increases
Solution Approach 1:
The buffer circuits serve as intermediary components that provide necessary isolation without requiring complete redesign of the clock distribution architecture. By placing buffers at strategic points in the existing circuit, the patent achieves noise isolation while minimizing the increase in overall system complexity.
Solution Approach 2:
The patent applies buffering selectively rather than uniformly throughout the entire system. Buffer circuits are placed specifically at points where noise isolation is most critical (between the microprocessor clock input and the RF circuits), rather than adding buffers to every clock line, thus optimizing the balance between performance improvement and complexity increase.
3Object-affected harmful factors
If sensitive RF circuits are connected directly to the crystal oscillator, then reverse isolation is maximized protecting against noise, but device complexity and layout requirements increase
Solution Approach 1:
The patent differentiates between sensitive and less sensitive RF circuits, connecting sensitive circuits (such as GSM/GPRS chipsets) directly to the crystal oscillator for maximum reverse isolation, while connecting less sensitive circuits (such as Bluetooth modules) through buffer circuits. This selective connection strategy optimizes noise protection for critical circuits without unnecessarily complicating the entire system.
Solution Approach 2:
The patent applies the direct connection approach (without buffers) only to the extent necessary for the most sensitive circuits that require maximum reverse isolation. By providing 40 to 80 decibels of reverse isolation through buffers for less sensitive circuits, the patent achieves sufficient protection without the full complexity of direct crystal oscillator connections for all circuits.
Data Source
AI summary
A mobile wireless communications device includes a circuit board carried by a housing. A microprocessor, RF transceiver and circuitry are carried by the circuit board and operative with each other. Clock buffer circuitry is carried by the circuit board and connected to the RF transceiver and circuitry and microprocessor for isolating a clock signal from the noise of the microprocessor and allowing greater isolation for the RF transceiver from RF circuitry.