Digital PLL Oscillator Temperature Compensation for Low Phase Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Radio systems face challenges in maintaining phase stability and minimizing noise due to temperature variations, leading to reduced sensitivity and accuracy in signal transmission and reception, particularly in RADAR and radio communication systems, where phase noise affects frequency stability and system performance.
Innovation Solution
A digitally compensated phase locked oscillator (DCPLO) system that incorporates a phase frequency detector, a direct digital synthesizer (DDS), a temperature sensor, and a processor to adjust frequencies based on temperature readings, maintaining the phase locked state and minimizing phase noise through a frequency compensation circuit and bandpass filtering, eliminating the need for mechanical adjustments and reducing resonator quality factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature compensation is implemented using traditional methods, then frequency stability is improved, but device complexity increases
Solution Approach 1:
The patent replaces mechanical frequency adjustment mechanisms with a digital system comprising a temperature sensor, microprocessor, and direct digital synthesizer (DDS). The temperature sensor detects temperature variations, the microprocessor processes this data, and the DDS generates compensation signals electronically, eliminating the need for mechanical tuning components while maintaining frequency stability.
Solution Approach 2:
The system dynamically changes the frequency parameter of the local oscillator based on temperature readings. The microprocessor calculates compensation values according to stored temperature-frequency relationships and adjusts the DDS output frequency accordingly, allowing the system to adapt to temperature variations without mechanical intervention.
2Manufacturing precision
If mechanical frequency adjustments are used, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent eliminates mechanical frequency adjustment mechanisms and replaces them with a digital system. The frequency compensation is achieved through electronic signal generation by the DDS controlled by the microprocessor, which reads temperature data and applies appropriate compensation algorithms, thereby simplifying the manufacturing process while maintaining frequency accuracy.
Solution Approach 2:
The system incorporates automatic temperature compensation where the temperature sensor continuously monitors temperature, the microprocessor processes this information, and the DDS automatically adjusts the frequency without requiring manual intervention. This self-adjusting mechanism eliminates the need for post-production mechanical tuning.
3Reliability
If phase noise is reduced through traditional filtering, then signal quality is improved, but loss of energy increases
Solution Approach 1:
The patent replaces traditional analog filtering methods with a digital signal generation approach using DDS. The system generates precise frequency compensation signals electronically, achieving phase noise reduction through digital signal processing rather than energy-intensive analog filtering, thereby reducing energy loss while maintaining signal quality.
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 DCPLO system maintains low phase noise over an extended temperature range, improving system sensitivity and accuracy, reducing the need for post-production tuning, and simplifying manufacturing by eliminating mechanical frequency adjustments.
Implementation Method 1
a temperature sensor; and a processor coupled to the first DDS, the phase frequency detector, and the temperature sensor, the processor configured to set the frequency of the first DDS according to a temperature sensed by the temperature sensor
Implementation Method 2
a mixer, for mixing an output of the second DDS and the output of the PLL to produce a mixed signal
Implementation Method 3
a bandpass filter coupled to an output of the mixer for selecting a sideband of the mixed signal
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A digitally compensated phase locked oscillator (DCPLO) is disclosed herein. The DCPLO comprises: a DCPLO input for receiving a reference signal at a known frequency; a DCPLO output for outputting a signal at a desired frequency; a phased locked loop (PLL), the phased locked loop comprising: a phase frequency detector, an oscillator, and a PLL output coupled to the output; a first direct digital synthesizer (DDS), the first DDS having an output coupled to the PLL to supply a DDS signal to the PLL for adjusting the frequency within the PLL so as to maintain phase lock over the operating temperature; a temperature sensor; and a processor coupled to the first DDS, the phase frequency detector, and the temperature sensor, the processor configured to set the frequency of the first DDS according to a temperature sensed by the temperature sensor.