Half-Rate I/Q Clock Generator for Stable 90-Degree Phasing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional clock generators struggle to maintain the correct phase relationship between in-phase and quadrature clock signals at high operational speeds, particularly during startup, limiting their application in modern electronic systems.
Innovation Solution
The development of clock generator embodiments using D flip-flops and tri-state inverters configured to generate half-rate in-phase and quadrature clock signals, ensuring a 90-degree phase lag and high-speed operation by optimizing critical paths within the circuit, including the use of metal-oxide-semiconductor transistors for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional clock generators are used, then basic clock signal generation is achieved, but correct phase relationship between I and Q clock signals cannot be maintained at high operational speeds
Solution Approach 1:
The clock generator is divided into multiple D flip-flops (first and second edge-triggered D flip-flops) that independently process different phases of the clock signal. Each flip-flop is triggered by opposite edges of the input clock signal, allowing parallel processing that maintains phase relationships at high speeds.
Solution Approach 2:
The circuit is designed to establish the correct phase relationship between I and Q clock signals at startup before high-speed operation begins. The feedback paths and flip-flop configurations pre-establish the 90-degree phase lag, ensuring reliability is maintained when speed increases.
2Ease of manufacture
If clock generator structure is simplified, then ease of manufacture is improved, but operational speed capability is reduced
Solution Approach 1:
The circuit uses identical D flip-flop structures for both I and Q clock generation, copying the same reliable design pattern. This standardization simplifies manufacturing while the clever interconnection of these identical units achieves the high-speed performance through edge-triggered parallel operation.
3Productivity
If high-speed operation is achieved, then productivity is improved, but maintaining correct phase relationship becomes difficult
Solution Approach 1:
Each D flip-flop has its Q-bar output fed back to its D input, creating self-correcting feedback loops that maintain stable operation at high speeds. The feedback ensures that phase relationships are continuously reinforced rather than degrading with speed increases.
Solution Approach 2:
The circuit dynamically responds to opposite edges of the input clock signal, with the first flip-flop triggered by rising edges and the second by falling edges. This dynamic edge-triggered operation allows the circuit to adapt to high-speed variations while maintaining precise phase relationships.
Data Source
AI summary
Clock generator embodiments are provided to generate half-rate I and Q clock signals. The generators are configured to insure fan-out limitations, to insure correct phasing at startup, to reduce the number of signal inverters in a critical path, and to reduce the total number of inverter structures to thereby substantially extend generator operational frequency. An exemplary generator embodiment requires only two tri-state inverters and four inverters. These clock generators are particularly suited for variety of electronic systems such as high speed data serializers.