Log-Periodic Dipole Array Antenna Linear Phase Design
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Solution Overview
Problem
Conventional ultra-wideband (UWB) antenna systems, such as Log-Periodic Dipole Arrays (LPDAs) and Independently Center-fed Dipole Arrays (ICDAs), suffer from non-linear phase characteristics and low radiation efficiency, which hinder the accurate transmission and reception of UWB signals due to non-constant group delays and inefficient signal distribution among radiation elements.
Innovation Solution
A dipole array antenna system is designed with specific positioning of radiation elements and transmission lines to ensure that both the transmitter and receiver have identical radiation characteristics, with the difference in distances between elements on the transmission lines being substantial, allowing for linear phase characteristics to be achieved without compromising high radiation efficiency and gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional LPDA uses transmission line to connect radiation elements, then bandwidth is broadened, but phase linearity deteriorates due to non-constant group delay
Solution Approach 1:
The patent inverts the conventional LPDA configuration by reversing the order of radiation elements along the transmission line. Specifically, the elements are arranged in reverse sequence so that the element with the highest resonant frequency is positioned closest to the signal input, while elements with lower resonant frequencies are positioned progressively farther away. This inversion compensates for the transmission line delay by having higher frequency components (which experience less delay) radiated by elements closer to the input, and lower frequency components (which experience more delay) radiated by elements farther away, thereby achieving linear phase characteristics across the ultra-wide bandwidth.
2Manufacturing precision
If ICDA uses multiple transmission lines for independent feeding, then phase linearity is improved, but radiation efficiency deteriorates due to signal splitting loss
Solution Approach 1:
The patent segments the broadband signal into multiple frequency components, each directed to a specific radiation element optimized for that frequency range. By using a single transmission line with strategically positioned elements of different lengths and resonant frequencies, the system segments the radiation function across multiple elements while avoiding the energy loss associated with signal splitting in conventional ICDA configurations.
3Device complexity
If LPDA uses serial connection of elements, then device complexity is reduced, but signal distribution efficiency deteriorates
Solution Approach 1:
The patent applies local quality by positioning radiation elements with specific local characteristics (different lengths, resonant frequencies, and orientations) at different locations along the transmission line. Each element is locally optimized for its specific position and frequency range, with elements closer to the input having different properties than those farther away. This local optimization enables efficient signal distribution across the ultra-wide bandwidth while maintaining a simple serial feed network structure.
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 system ensures that all frequency components experience the same total delay, enabling linear phase signal recovery at the output, thus overcoming the limitations of non-linear phase characteristics and low efficiency in existing UWB antenna designs.
Implementation Method 1
Assume that element 1 (102) has a resonant frequency f1, and that element 2 (104) has a resonant frequency f2. If signals 106 with frequencies f1 and f2 are fed into the LPDA 100 at the same time, signals with frequency f1 will be radiated into free space by element 1 (102)
Implementation Method 2
Signals with frequency f2 will move along the transmission line 108 further since frequency f2 is not the resonant frequency of element 1 (102). Signals with frequency f2 will experience some additional delay caused by the transmission line 108
Data Source
AI summary
A log-periodic dipole array system employs a structure for the transmitter and the receiver designed in a way such that they compensate for the non-linear characteristics of each other to realize linear phase characteristics as a pair. Radiation elements on the receiver are positioned with respect to its corresponding transmission line in an order opposite to the positioning of the radiation elements on the transmitter. Although neither the transmitter dipole array nor the receiver dipole array itself has linear phase characteristics, the overall dipole array antenna system can realize linear phase characteristic. The log-periodic dipole array system has the advantages that linear phase characteristics can be obtained without sacrificing high radiation efficiency and gain.