Non-Integer Frequency Divider for Spur-Suppressed RF Output
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Solution Overview
Problem
Existing frequency divider circuits in wireless transmitters introduce undesirable harmonics, which are problematic due to regulatory and mask limitations, especially in high-power transmitter systems.
Innovation Solution
A non-integer frequency divider circuit that includes a first divider, a mixer, a filter, and a second divider, which together produce a signal frequency ratio that is a non-integer value, effectively reducing the power and number of undesired frequency spurs by attenuating sideband components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an integer frequency divider is used to divide the VCO output frequency, then the division is simple and reliable, but undesired frequency spurs and harmonics are generated that violate regulatory and mask limitations
Solution Approach 1:
The frequency division process is segmented into multiple stages: a first integer divider divides by N, a mixer combines the divided signal with the original VCO signal, and a second integer divider divides by M. This segmentation allows the system to achieve non-integer division (N/M) while filtering out harmful spurs through the mixer and intermediate filtering stages, resolving the contradiction between reliable division and harmful frequency generation.
Solution Approach 2:
A mixer is introduced as an intermediary component between the first divider and the second divider. The mixer combines the divided signal with the original VCO signal to produce sum and difference frequencies, allowing selective filtering of unwanted harmonics and spurs. This intermediary mechanism enables clean non-integer frequency division without generating harmful frequency components.
2Object-generated harmful factors
If a non-integer frequency divider is implemented using multiple dividers and a mixer, then undesired frequency spurs are reduced, but the device complexity increases
Solution Approach 1:
The patent merges multiple integer division operations with a mixing operation to achieve non-integer division. By combining the output of the first divider with the original VCO signal in a mixer, and then dividing again in the second divider, the system achieves complex non-integer frequency ratios using relatively simple, well-established integer divider circuits and a standard mixer, thus managing complexity while reducing spurs.
3Power
If the output power is increased in high-power transmitter systems, then the transmission range is improved, but the power of undesired frequency spurs increases violating regulatory limitations
Solution Approach 1:
The patent converts the potentially harmful frequency spurs generated by integer division into beneficial filtered outputs. By using a mixer to generate sum and difference frequencies followed by selective filtering, the system eliminates harmful spurs while maintaining the desired frequency components. This allows high-power transmission to be achieved without violating regulatory spectral mask requirements, as the harmful frequency components are converted and filtered out in the process.
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 non-integer divider reduces the power of undesired frequency spurs, enabling higher output power and relaxing front-end filtering requirements, while maintaining low power consumption.
Implementation Method 1
A mixer is coupled to receive the first signal, and a second signal having a frequency equivalent to that output by the first divider. The mixer outputs a third signal having a frequency based on respective frequencies of the first and second signal.
Data Source
AI summary
A non-integer divider for dividing the frequency of a signal is disclosed. A non-integer divider includes a first divider that divides the frequency of a first signal. A mixer is coupled to receive the first signal, and a second signal having a frequency equivalent to that output by the first divider. The mixer outputs a third signal having a frequency based on respective frequencies of the first and second signal. A second divider receives and frequency divides the third signal to produce a fourth signal. A ratio of the frequency of the first signal to the fourth signal is a non-integer value.