Earticle

The probability of detection and the accuracy of a measurement are determined by the available SNR ratio and hence by the energy used for illuminating the target. Also, increasing the rate of illumination of a target allows obtaining less uncertain predictions. A high energy burst and a high illumination rate are desirable from the tracker's accuracy point of view. However they negatively affect the transmitter beam occupancy budget and therefore they are undesirable from the point of view of the radar's ability to deal with multiple targets. Hence, tracker parameters (including track illumination rate and dwell-time or burst energy) should be designed to satisfy a double objective such as minimum beam occupancy, which will give maximum efficiency in the use of radar's energy and maximum beam scheduling effectiveness (shorter pulses, reduced dwell-time)-desired tracking accuracy. In this paper we presented a new approach to optimally select both the energy of the tracking waveforms and the track sampling rates which jointly minimize occupancy and satisfy angular accuracy requirements for a MFR with an tracking filter.

To overcome considerable path loss in millimeter-wave propagation, high-gain directional beamforming is considered to be a key enabling technology for outdoor 5G mobile networks. Associated with beamforming, this paper investigates propagation power loss characteristics in two aspects. The first is beamwidth effects. Owing to the multipath receiving nature of mobile environments, it is expected that a narrower beamwidth antenna will capture fewer multipath signals, while increasing directivity gain. If we normalize the directivity gain, this narrow-beamwidth reception incurs an additional power loss compared to omnidirectional-antenna power reception. With measurement data collected in an urban area at 28 GHz and 38 GHz, we illustrate the amount of these additional propagation losses as a function of the half-power beamwidth. Secondly, we investigate power losses due to steering beam misalignment, as well as the measurement data. The results show that a small angle misalignment can cause a large power loss. Considering that most standard documents provide omnidirectional antenna path loss characteristics, these results are expected to contribute to mmWave mobile system designs.

본 논문에서는 ESA 레이다의 성능을 향상시키기 위하여, 간섭이 예상되는 PRF를 회피하여 효과적으로 PRF(Pulse Repetition Frequency)를 설계하는 방법을 제시하고 있다. 본 논문에서 제안하는 기법은 기존의 기법에서 고려하던 송신신호 및 직하방신호(nadir)와의 간섭 이외에 빔폭과의 간섭을 새롭게 고려하고 있으며, 특히 ESA 레이다의 조향각 변화에 따른 빔 넓어짐 효과를 고려함으로써, 기존의 방법에서 회피할 수 없었던 부적절한 PRF를 회피하여 ESA 레이다의 파형설계가 가능하다. 시뮬레이션 결과를 통해 본 논문에서 제시하는 PRF 설계 기법이 기존의 방법에서 회피할 수 없었던 ESA 레이다의 간섭들을 회피하여 PRF가 설계가 가능함을 정량적 및 정성적으로 확인할 수 있었다.

In this paper, we propose a PRF design method to improve the performance of the ESA radar, by excluding the interference from an improper PRF. Like the conventional method, the proposed method also considers the interference between the transmitted signal and the nadir signal, but additionally analyzes the relationship between the interference and the signal beamwidth. The simulation results show that the proposed method quantitatively and qualitatively excluded interference from the PRF and additionally dealt with the beamwidth broadening effect of an ESA radar.

본 논문에서는 구성 안테나의 수신 영역을 빔 폭 내로 한정하고, 각도 측정 모호성이 없는 선형간섭계 안테나 설계를 위한 수식을 제안하였다. 수식을 이용하여 구성 안테나 간격과 각도 모호성과의 관계를 설명하고, 선형간섭계 설계를 위한 운용주파수, 각도 정확도, 빔폭, 측정 확률을 계산하여 고각과 방위각 측정을 위한 총 5개의 구성 안테나로 이루어진 선형간섭계 안테나를 설계, 제작, 측정한 결과를 제시하였다. 각도 측정 정확도는 방위각, 고각 각각 $0.01^{\circ}$, $0.016^{\circ}$ 이며, 계측 값의 99 % 이상이 모호성 없이 정확히 측정되었다. 이로써 제안한 수식과 설계 과정이 유효함을 확인할 수 있었다.

In this paper, it is represented that equations for design of linear interferometer antenna when the 3 dB beamwidth is only region of interest. Using the equations, relationships between angle measurement ambiguity and element antenna spacings are described. And then, operating frequency, angle measurement accuracy, beamwidth, correct measurement probability are calculated for five antennas interferometer to measure azimuth and elevation angle. The interferometer antenna was designed and fabricated using the calculated parameters. The angle measurement accuracy were $0.01^{\circ}$ and $0.016^{\circ}$ for azimuth and elevation axes with 99 % probability of doing measurements correctly which means that ambiguous solution did not occur more than 1 % of the time. These results validated the equations and design procedures.

In this paper, a modified multimode hem antenna is designed to have 142 mm horn aperture radius and 921 mm length in order to be safe under 100 MW peak pulse power at 3 cm wave length through breakdown phenomenon study that threshold field strengths for the air breakdown phenomena is decided to be 3.78 MV/m. The proposed antenna is measured gain over 27 dBi and the -25 dB beam width of 29$^{\circ}$ in vertical plane.