Bandpass-Filtered Frequency Quadrupler for Harmonic Suppression
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Solution Overview
Problem
Conventional frequency multipliers generate unwanted harmonics, reducing spectral purity and deteriorating the performance of communication systems, particularly in ultra-high frequency synthesizers used in 5G mobile and phased array antennas.
Innovation Solution
A high spectral purity frequency quadrupler employing bandpass filters, utilizing a cascade method of multiplying frequencies through a high-performance low-frequency oscillator, which includes a first and second push-pull doubler and a pair of bandpass filters to selectively amplify and filter out unwanted harmonics, and amplifies the second harmonic of the input signal, and removes unnecessary harmonics using a bandpass filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional frequency multipliers are used to multiply frequency, then frequency multiplication is achieved, but unwanted harmonics are generated reducing spectral purity
Solution Approach 1:
The frequency quadrupling process is divided into two separate doubling stages (first push-pull doubler and second push-pull doubler), with a bandpass filter placed between them. This segmentation allows intermediate filtering of harmonics generated in the first stage, preventing them from propagating to the second stage and degrading the final spectral purity.
Solution Approach 2:
The bandpass filter extracts and removes unwanted harmonics (specifically the 3rd harmonic and other spurious signals) from the output of the first doubler, allowing only the desired 2nd harmonic to pass through to the second doubler. This extraction of harmful frequency components directly addresses the spectral purity problem.
2Object-generated harmful factors
If bandpass filter is added to remove harmonics, then spectral purity is improved, but device complexity increases
Solution Approach 1:
The bandpass filter's resonant frequency and bandwidth parameters are specifically designed to pass only the 2nd harmonic frequency while blocking other harmonics. By carefully selecting these parameters, the filter achieves effective harmonic rejection with a relatively simple circuit implementation, balancing spectral purity improvement against device complexity.
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 proposed solution effectively increases spectral purity and improves system performance by selectively amplifying the second harmonic and removing unnecessary harmonics, enhancing the output signal quality.
Implementation Method 1
a first bandpass filter that passes a signal having a frequency band twice that of the input ultra-high frequency signal among output signals of the first push-pull doubler
Implementation Method 2
The first bandpass filter may be configured by connecting an inductor and a capacitor in parallel
Implementation Method 3
the first amplifier unit amplifies the second harmonic of the input ultra-high frequency signal to output the amplified second harmonic
Implementation Method 4
the first input impedance matching unit selectively transmits a second harmonic of the input ultra-high frequency signal to the first amplifier unit
Data Source
AI summary
A high spectral purity frequency quadrupler employing a bandpass filter, includes a first push-pull doubler that doubles a frequency of an input ultra-high frequency signal, a first bandpass filter that passes a signal having a frequency band twice that of the input ultra-high frequency signal among output signals of the first push-pull doubler, a second push-pull doubler that doubles an ultra-high frequency signal passing through the first bandpass filter, and a second bandpass filter, where the first push-pull doubler comprises a first input impedance matching unit, a first amplifier unit, and a first output impedance matching unit, and where the first input impedance matching unit selectively transmits a second harmonic of the input ultra-high frequency signal to the first amplifier unit, and the first amplifier unit amplifies the second harmonic.