Kirill Ponur

Currently, methods of radar remote sensing at small incidence angles (from the vertical to 15∘) are actively developed. An important application of these methods is the determination of the presence and sea ice concentration. This paper presents an approach to numerical simulation of an experiment in which a reflecting surface with different sea ice concentrations is modeled and then the characteristics of the radar signal reflected by this surface for a given measurement geometry are modeled. Without loss of generality, in this paper we will consider a specific geometry of the DPR (Dual-frequency Precipitation Radar) radar on the GPM (Global Precipitation Measurement) mission satellite and only the Ku-band of this radar. The signal reflected by sea waves will be calculated within the Kirchhoff approximation. Since there is no generally accepted model for the signal scattered by the sea ice at small incidence angles, an empirical formula obtained from DPR data will be used as a model. The paper discusses a method for determining sea ice concentration using radar sensing data at low incidence angles.

The paper is dedicated to Direction of Arrival (DOA) estimation of multiple sources using a single port phased antenna array. We consider the case of the received signal with randomly varying phase that may be caused by both hardware constraints and waveform design. The well-known subspace-based algorithms such as Multiple Signal Classification (MUSIC) show good performance with digital antenna arrays but they cannot be applied under the mentioned restrictions. Moreover, the existing beamspace approaches intended for phased antenna arrays cannot also be applied because of the phase variation. In this paper we propose a novel phase-independent beamspace MUSIC algorithm that uses the spatial power spectrum measured with a finite number of beams as the input. It builds an approximation of the signal covariance matrix and applies the MUSIC’s approach for DOA estimation. The simulation results shows that the developed algorithm has a superresolution ability and allows one to distinguish a weak source masked by the sidelobe power leakage of the stronger one.

The paper presents the results of a series of experiments performed in February-March 2023. An X-band radar was installed on the metro bridge across the Oka River in Nizhny Novgorod. The radar worked in the radio altimeter mode and the waveform of the reflected pulse was recorded (the dependence of the power of the reflected signal on time). As a result of processing, the distance to the reflection area on the surface was determined. Dependences of the power of the radar signal reflected by the ice cover on the incidence angle were obtained. The air temperature was recorded synchronously with the measurements. The change in the distance to the area of reflection on the surface was associated with a change in the water level in the Oka River. Dependences of the power of the reflected signal on the angle of incidence were plotted for a radar with a knife-like antenna beam for different days of measurements. Based on empirical data, a formula is obtained for the angular dependence of the power of reflected microwave signal for fresh ice cover.

The first results of data processing of the experiment on the Nizhny Novgorod cable car are presented. A pulsed X-band radar was installed on a technological trolley and performed measurements while moving in two modes that worked sequentially. In the radio altimeter mode, the reflected waveform was measured and the distance to the scattering surface was determined. In the Doppler mode, the Doppler spectrum of the reflected signal was measured, which contains information about the statistical parameters of the surface. Data processing was carried out and the first results confirmed the assumption that the Doppler spectrum can be an effective tool for classifying the type of the underlying surface according to the "ice/water" criterion. Subsequent data processing will allow us to evaluate the accuracy of the developed algorithms.

The paper is dedicated to the multipath angle of arrival (AOA) estimation problem in millimeter wave (mmWave) 5G NR communication system. The case of a phased antenna array with a single digital port is considered. In this scenario, the conventional highly accurate subspace-based algorithms cannot be applied because of hardware restrictions. We proposed a novel subspace-based algorithm called power-based root minimal polynomial method (PR-MPM) that uses the spatial power spectrum to get an approximation of the signal correlation matrix. The power spectrum is measured via the conventional beam sweeping procedure over a finite number of directions. The efficiency of the proposed method is studied using the high-realistic ray-tracing-based channel model applied in mmWave IEEE 802.11ay standard. Simulation results show that AOAs can be precisely estimated using only single-port power measurement.