Differential PLL Phase Adder for Low-Spur High-Frequency Signals
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Solution Overview
Problem
Conventional phase adders at high frequencies suffer from non-linear effects that generate undesired spurious signals, leading to output phase errors, and are difficult to realize with ideal or close to ideal characteristics, especially when dealing with sinusoidal signals.
Innovation Solution
The development of high-quality Phase Adder circuits using differential multiplier circuits with triode interface configurations and phase locked loops, which include balanced differential mixer circuits, loop filters, and voltage-controlled oscillators, to generate a uniform timing reference for phased arrays, reducing intermodulation distortion and phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional phase adders are used at high frequencies, then the circuit structure is simple, but non-linear effects generate undesired spurious signals leading to output phase errors
Solution Approach 1:
The phase adder is divided into multiple functional blocks: a first mixer that generates sum and difference frequencies, a bandpass filter that selects the sum frequency, and a second mixer that combines it with the local oscillator signal. This segmentation allows each block to perform its function optimally, reducing spurious signals while maintaining manageable circuit complexity
Solution Approach 2:
An intermediary bandpass filter is introduced between the first mixer and the second mixer to selectively pass only the desired sum frequency component while blocking spurious signals and intermediate frequencies. This intermediary element acts as a mediator that cleans the signal before further processing, improving phase accuracy without requiring complete redesign of the entire circuit
2Ease of manufacture
If double-side-band analog multipliers are used, then the multiplication function is achieved, but removing one side band introduces additional output phase errors
Solution Approach 1:
The invention converts the harmful effect of having both side bands present into a benefit by using the difference frequency component constructively. The second mixer combines the filtered sum frequency with the local oscillator to produce an output where the phase relationship is preserved and enhanced, rather than trying to eliminate one side band and introducing errors in the process
Solution Approach 2:
The circuit employs feedback mechanisms where the output of the second mixer is combined with the local oscillator signal in a controlled manner. This feedback approach allows precise control over the phase relationship between input signals and output, ensuring phase coherence is maintained throughout the multiplication process
3Speed
If phase adders operate at high frequencies, then signal distribution speed is improved, but non-linear effects are enhanced generating more spurious signals
Solution Approach 1:
The bandpass filter performs preliminary action by pre-selecting and cleaning the sum frequency component before it enters the second mixer stage. This preliminary filtering removes spurious signals and intermediate frequencies early in the signal path, preventing them from being further processed or amplified, thus reducing the overall spurious signal content at the final output
Solution Approach 2:
The invention transitions from direct high-frequency multiplication to a multi-stage process involving frequency conversion to intermediate frequencies, filtering, and then final mixing. By operating in another dimensional space (intermediate frequencies) temporarily, the circuit achieves better control over non-linear effects while maintaining the ability to produce high-frequency output signals
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
These circuits significantly reduce phase errors and spurs, achieving a more precise and coherent signal distribution over large areas by eliminating leakage and DC components, thereby enhancing the quality of the reference product component.
Implementation Method 1
a voltage controlled oscillator (VCO) circuit having an input electrically connected to the output of the loop filter and with an output electrically feeding back to the second differential input of the balanced differential mixer circuit
Implementation Method 2
a loop filter having an output and an input electrically connected to the output of the balanced differential mixer circuit
Implementation Method 3
a balanced differential mixer circuit with a first differential input electrically connected to the differential output of the differential multiplier circuit, a second differential input, and an output
Data Source
AI summary
An electronic circuit including: a differential multiplier circuit with a first differential input and a second differential input and a differential output; and a phase locked loop (PLL) circuit including: (1) a balanced differential mixer circuit with a first differential input electrically connected to the differential output of the differential multiplier circuit, a second differential input, and an output; (2) a loop filter having an output and an input electrically connected to the output of the balanced differential mixer circuit; and (3) a voltage controlled oscillator (VCO) circuit having an input electrically connected to the output of the loop filter and with an output electrically feeding back to the second differential input of the balanced differential mixer circuit.