PLL Frequency Synthesizer Dynamic Carrying Against SDM Saturation
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Solution Overview
Problem
Conventional phase locked loop frequency synthesizers with sigma-delta modulators experience saturation issues when the amplitude of transmitting data exceeds a certain threshold, leading to incorrect function and inability to represent input DC values within the modulator's processing limits.
Innovation Solution
A dynamic carrying method is introduced, where transmitting data is separated into a residue part and a carrying part when the amplitude exceeds a threshold, with the residue part processed by the sigma-delta modulator to generate a first modulus control signal, and an auxiliary modulator processes the carrying part to generate a second modulus control signal, which are then summed to prevent saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amplitude of transmitting data is amplified by a compensation filter, then the signal strength is improved, but the sigma-delta modulator experiences saturation when the amplitude exceeds the threshold
Solution Approach 1:
The transmitting data is segmented into two parts: a residue part that is processed by the sigma-delta modulator and a carrying part that is processed by an auxiliary modulator. This segmentation allows the residue part to remain within the threshold range for correct SDM operation while the carrying part handles the excess amplitude information separately.
Solution Approach 2:
An auxiliary modulator is introduced as an intermediary device to process the carrying part of the transmitting data. This auxiliary modulator generates a second modulus control signal that, when combined with the first modulus control signal from the SDM, reconstructs the original high-amplitude signal without causing saturation.
2Adaptability or versatility
If the sigma-delta modulator processes high amplitude signals, then the dynamic range is improved, but saturation occurs resulting in incorrect function
Solution Approach 1:
The input signal is divided into residue and carrying parts based on the threshold. The residue part is processed by the SDM within its safe operating range, while the carrying part is handled by the auxiliary modulator, effectively extending the dynamic range without sacrificing operational correctness.
Solution Approach 2:
The first modulus control signal from the sigma-delta modulator and the second modulus control signal from the auxiliary modulator are merged through addition to produce the final modulus modulation signal. This combining operation reconstructs the complete high-dynamic-range signal while maintaining correctness.
3Device complexity
If a single sigma-delta modulator is used, then the device complexity is reduced, but the system cannot handle transmitting data with amplitude exceeding the threshold
Solution Approach 1:
The signal processing function is segmented between two parallel modulator paths: the SDM for the residue part and the auxiliary modulator for the carrying part. This segmentation enables the system to handle a wider input signal range while keeping each individual modulator relatively simple.
Solution Approach 2:
The auxiliary modulator is designed with the same signal transfer function as the SDM, making it a universal modulator structure that can be used in place of or alongside the SDM. This multi-functionality allows the system to handle both low-amplitude and high-amplitude signals using similar building blocks.
Data Source
AI summary
A dynamic carrying method to prevent saturation of a sigma-delta modulator of a phase locked loop frequency synthesizer. The phase locked loop frequency synthesizer using the dynamic carrying method comprises a forward portion receiving a reference frequency signal and a first frequency signal to generate an output carrier signal; a multi-modulus divider dividing the output carrier signal frequency to generate the first frequency signal; a dynamic carrying device receiving and separating transmitting data into a carrying part and a residue part when the transmitting data amplitude exceeds a threshold; a sigma-delta modulator receiving the residue part to generate a first modulus control signal; an auxiliary modulator receiving the carrying part to generate a second modulus control signal; and a first adder receiving the first modulus control signal, the second modulus control signal, and a third modulus control signal and outputting a modulus modulation signal to modulate the multi-modulus divider.