Active Biconical Antenna Buffer Amplifier Impedance Matching
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Solution Overview
Problem
Passive biconical and Vivaldi antennas face limitations in the low-frequency extension band, where they exhibit degraded sensitivity and resonate like electrically small dipole antennas, failing to leverage wideband behavior, and active dipole antennas experience higher-order resonances, while omnidirectional antennas are needed for direction finding.
Innovation Solution
Integration of a high-impedance buffer amplifier directly into the feed of the biconical antenna, combined with active Vivaldi antennas, to extend the usable bandwidth to lower frequencies without increasing antenna size, using field-effect transistors (FETs) with gallium nitride (GaN) semiconductor channels, and configuring the buffer amplifier for impedance matching across traditional and extension bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If passive biconical antenna is used in extension band, then antenna size is reduced, but receiver sensitivity is degraded
Solution Approach 1:
The patent combines a passive biconical antenna with an active buffer amplifier to create an active biconical antenna. The buffer amplifier is integrated directly into the antenna feed, merging the antenna element with the amplification stage. This combination allows the antenna to maintain small physical size in the extension band while the buffer amplifier compensates for the sensitivity degradation through signal amplification.
Solution Approach 2:
The buffer amplifier acts as an intermediary between the passive biconical antenna and the receiver system. It is positioned at the antenna feed and provides impedance matching and signal buffering, isolating the receiver from the antenna's frequency-dependent impedance variations. This intermediary component enables the small antenna to maintain effective coupling to the receiver across the extension band.
2Reliability
If active dipole antenna is used to improve low-frequency performance, then sensitivity is improved, but higher-order resonances are introduced
Solution Approach 1:
The patent applies local quality by using a buffer amplifier with frequency-dependent input impedance characteristics. The buffer is designed to provide high input impedance specifically in the extension band where the antenna is electrically small, while maintaining appropriate impedance matching in the traditional band. This localized impedance control allows sensitivity improvement in the extension band without introducing harmful resonances.
3Adaptability or versatility
If Vivaldi antenna is used for wideband operation, then bandwidth is extended, but omnidirectional radiation is lost
Solution Approach 1:
The patent segments the antenna system into different functional components: the biconical antenna element provides omnidirectional radiation characteristics, while the buffer amplifier provides the active impedance control and amplification. This segmentation allows each component to fulfill its specialized function - the biconical geometry ensures omnidirectional pattern while the active buffer extends the usable bandwidth into the extension band.
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
Improves receiver sensitivity by 10 dB in the extension band compared to passive biconical antennas while maintaining sensitivity in the traditional band, enabling direction-finding functionality and low-frequency bandwidth extension.
Implementation Method 1
a buffer amplifier that provides electrical impedance isolation from one circuit to another for the purpose of mitigating the effects of standing waves that an antenna impedance may produce
Implementation Method 2
an integrated low-noise signal amplifier built into the unit... the integrated low-noise amplifier boosts the radiofrequency (RF) signals picked up by the antenna to compensate for downstream cable loss
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An active biconical antenna (4) and a receive array (30) comprising a combination of active biconical and Vivaldi antennas (2). In one configuration, the active biconical antenna includes upper (8a) and lower (8b) cones. Each cone has a respective truncated apex. First and second feed points (18) are respectively connected to the truncated apexes of the upper and lower cones and to first and second conductors (la, lb). The active biconical antenna further includes a buffer amplifier (10) having respective input terminals connected to the first and second conductors. The buffer amplifier has an input impedance that is impedance matched to an antenna impedance at and above but not below a frequency fc and is higher than the antenna impedance at frequencies substantially less than fc. The buffer amplifier also has an output impedance that is impedance matched to a system impedance at frequencies both above and below fc. A length of the first and second conductors is less than a wavelength at the frequency fc.