Development of Wide Bandwidth and Tunable Circuits and Antennas for Ultra-wideband Radar Applications
Abstract
Signal integrity is key to the performance of a ground penetration radar system. To achievehigh performance, clutter should be minimized and signals reflected from targeted objects shouldbe highly distinguished with reflections from ground, antennas, and any circuits within a transmittingchain. In the past decades, research on ultra-wideband antennas has primarily been focusedon bandwidth, radar cross-section, gain, etc. [1, 2]. Other antenna research efforts take a morecomprehensive approach to consider soil models and the signal integrity of transmitted and receivedpulses [3, 4]. However, the study of time-domain pulses is only limited to the antennaitself. Unwanted reflections can come from open ends, a feed-point of an antenna, interfacedpassive circuits (baluns, feed structures, etc.) to an antenna and signal power levels. In addition,these studies are also limited to individual antenna evaluation rather than actual ground penetrationradar deployments. Usage scenarios and actual environment effects are often not taken into account.A resistively loaded vee dipole antenna (RLVD) is an excellent representation. While ithas been developed for ultra-wideband radar systems, the design and implementation that maintainsexcellent signal integrity have not been perfected.An important application of an ultra-wideband ground penetration radar system is to detectland mines with a diameter of ~8 cm and height of 4 cm in a depth in order of ~10 cm. In order toresolve land mine features, the signal peak frequencies should be around 4 GHz to 6 GHz (shortpulses). The bandwidth of a typical ground penetration radar system is around 500 MHz to 6 GHzwhich compromises radar performance. The conductivity of soil becomes quite lossy above 1GHz. Thus, it is challenging for high-frequency signals to penetrate deep into ground. While lowfrequency signals (below 500 MHz) can penetrate deeper into ground, the frequency bandwidthratio of the radar will become larger than 12:1. In previous decades, antennas and passive circuitcomponents relying on electromagnetic coupling and resonant structures (half-wavelength transmissionlines, etc.) have limited bandwidth ratios. The largest bandwidth ratio 46:1 of a passivebalun using broadside transmission lines (without any ferrite materials) was reported by the PI [5,6]. To cover the low frequency ends, an antenna or a passive device must have a much larger sizewhich also causes much higher conductor losses at high frequencies. An alternative approach isto use ferrite materials that have high permeability. Many of these ferrite components are handwoundstructures that have limited GHz frequency performance and cause significant signal variations.There have been very little research efforts to develop wide bandwidth components froma few MHz~s to multi-GHz~s with compact size, low loss, consistent electrical performance andtuning capabilities.In this project, we propose 1) develop and improve the signal integrity of an integrated balunand restively loaded vee dipole antenna (500 MHz-8 GHz) using advanced multi-layered LiquidCrystal Polymer boards for current ultra-wideband radar systems, 2) develop ultra-wideband antennasand related passive circuits with large bandwidth ratios (~800:1) and tuning capabilities,and 3) develop high power low noise amplifiers for pulse receivers using an advanced GalliumNitride (GaN) semiconductor to handle high reflections with improvements more than 1000 times.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712488
Entities
People
- Anh-Vu Pham
Organizations
- Office of Naval Research
- United States Navy
- University of California, Davis