Bistatic Radar Geometry Research Articles

Above-Ground Biomass Retrieval over Tropical Forests: A Novel GNSS-R Approach with CyGNSS

An assessment of the National Aeronautics and Space Administration NASA’s Cyclone Global Navigation Satellite System (CyGNSS) mission for biomass studies is presented in this work on rain, coniferous, dry, and moist tropical forests. The main objective is to investigate the capability of Global Navigation Satellite Systems Reflectometry (GNSS-R) for biomass retrieval over dense forest canopies from a space-borne platform. The potential advantage of CyGNSS, as compared to monostatic Synthetic Aperture Radar (SAR) missions, relies on the increasing signal attenuation by the vegetation cover, which gradually reduces the coherent scattering component σ coh , 0 . This term can only be collected in a bistatic radar geometry. This point motivates the study of the relationship between several observables derived from Delay Doppler Maps (DDMs) with Above-Ground Biomass (AGB). This assessment is performed at different elevation angles θ e as a function of Canopy Height (CH). The selected biomass products are obtained from data collected by the Geoscience Laser Altimeter System (GLAS) instrument on-board the Ice, Cloud, and land Elevation Satellite (ICESat-1). An analysis based on the first derivative of the experimentally derived polynomial fitting functions shows that the sensitivity requirements of the Trailing Edge TE and the reflectivity Γ reduce with increasing biomass up to ~ 350 and ~ 250 ton/ha over the Congo and Amazon rainforests, respectively. The empirical relationship between TE and Γ with AGB is further evaluated at optimum angular ranges using Soil Moisture Active Passive (SMAP)-derived Vegetation Optical Depth ( VOD ), and the Polarization Index ( PI ). Additionally, the potential influence of Soil Moisture Content (SMC) is investigated over forests with low AGB.

The Effect of Polarization on the Quantum Radar Cross Section Response

The quantum radar cross section (QRCS) is a measure of how electromagnetically “large” an object appears to a quantum radar. The fundamental mechanism that creates the return response is the interaction between the atomic electric dipole moments and the incoming photon. This paper derives the QRCS equation considering the effect of photon polarization in this interaction, as well as providing a means to study bistatic radar geometries. It is found that under normal circumstances, polarization plays no role in the target response. However, if the target’s atomic dipoles are all aligned in one particular direction, such as if the object is in a strong uniform or slowly varying field, polarization has a significant effect on the response by allowing us to “steer” the location of a null to any observation angle desired. Furthermore, scattering can be suppressed in a very large range of scattering angles (not just one) if the polarization of the object and photon are chosen judiciously. It will be shown that this effect is unique to quantum radar and has no classical counterpart.

바이스태틱 레이더에서 아이소레인지-아이소도플러 컨투어 맵을 이용한 이미징 기법

바이스태틱 레이더 환경에서 지상 표적의 이미징은 수신 데이터 획득 시간 동안에 송신부 및 수신부의 이동에 따른 레인지 및 도플러 정보의 변화가 복잡하여 이에 대한 보상과정, 즉 이미징 과정이 모노스태틱 레이더 환경에 비해 상당히 어렵다. 본 논문에서는 아이소레인지(isorange)와 아이소도플러(isoDoppler) 컨투어 정보를 이용하여 이미징이 가능한 resolution 격자를 추출할 수 있는 바이스태틱 레이더 송수신기 geometry를 제시하고, 고정된 표적을 이미징할 수 있는 알고리즘을 제시한다. 또한, 이때 얻을 수 있는 해상도를 분석하고, 시뮬레이션으로 성능을 검증한다. Imaging in bistatic radar has been known a more difficult task than that in monostatic radar. It is because the behavior of the bistatic range and the bistatic Doppler due to the motion of a transmitter and a receiver is so random that the compensation procedure, which we call an imaging algorithm, is quite complicated. This paper presents a bistatic radar imaging algorithm that can be used in some specific bistatic radar geometry. We show this geometry can present rectangular-like resolution cell on isorange-isoDoppler contours map. We also present the associated resolution and simulation results.

Coherent Doppler Processing Using Interpolated Doppler Data in Bistatic Radar

In order to execute coherent Doppler processing in a high range-rate scenario, whether it is for detection, estimation or imaging, range walk embedded in target return should be compensated first. In case of a bistatic radar geometry where a transmitter, a receiver and a target can be all moving, the extent of range walk depends on their relative positions and velocities. This paper presents a coherent Doppler processing algorithm to achieve target detection and Doppler frequency estimation of a target under a bistatic radar geometry. This algorithm is based on the assumption that a target has constant Doppler frequency during a coherent processing interval (CPI). Thus, we first show under what condition the assumption could be valid. We next develop an algorithm, along with its implementation procedures where the region of range walk, called a window, is manipulated. Finally, the performance of a proposed algorithm is examined through simulations.

Radar studies of lightning‐induced plasmas with potential applications to radio communications and space surveillance

The problem of radio backscatter from lightning‐induced plasmas is briefly reviewed. The predicted wavelength dependence of the backscattered power is compared to observations made with the MIT S band, C band and the Millstone UHF radar. The analysis is extended to a pancakelike plasma created through single radar beam heating of the atmosphere. The artificial plasmas are modeled as perfectly conducting, rough plasma disks, with random surface inhomogeneities described by either a Gaussian or power law type spectrum. Both monostatic and bistatic radar geometries are considered. These may be used in diagnostic and space surveillance/radio communication applications, respectively. The wavelength dependence of the radio reflectivity of a plasma pancake with Gaussian type surface roughness is found to be different from that of a plasma with a power law type surface roughness in the backscatter radar geometry. In the radio communication and space surveillance applications, the radio reflectivity may be independent of the incident wavelength, if the surface density inhomogeneities are characterized by an azimuthally symmetric power law type spectrum. By contrast, a wavelength dependence is expected for the Gaussian type spectrum.