Pulse Doppler Radar System Research Articles

전차 탑재 L-밴드 펄수 도플러 레이더 설계 및 제작

전차 탑재 레이더는 기상에 관계없이 전천후로 대전차 미사일을 탐지하는 능동 방호 장치의 필수적인 센서이다. 본 논문에서는 전차 탑재 레이더의 설계, 제작 및 시험 결과를 제시한다. 레이더 시스템은 안테나부, 송수신부, 신호처리부의 3개의 LRU로 구성되며, 개발 기술은 패치 안테나, SSPA 송신기, coherent I/Q detector, DSP기반 도플러 FFT 필터, 적응 CFAR, TWS 추적기 및 위협 판단을 포함한다. 개발된 레이더 시스템의 설계 성능은 고정 및 기동 시험을 통하여 확인한다. A Missile Warning Radar is an essential sensor for active protection system to detect antitank missile in all weather environments. This paper presents the design, development, and test results of L-band pulsed Doppler radar system for main battle tank. This radar system consists of 3 LRUs, which include antenna unit, transmitter and receiver unit and radar signal & data processing unit. The developed core technologies include the patch antenna, SSPA transmitter, coherent I/Q detector, DSP based Doppler FFT filter, adaptive CFAR, SIW tracking capability, and threat decision. The design performance of the developed radar system is verified through various ground fixed and moving vehicle test.

A Study on the Application of Time Modulated Antenna Arrays to Airborne Pulsed Doppler Radar

The time modulated (TM) linear arrays with variable aperture sizes (VAS) are applied to the airborne pulsed Doppler (PD) radar system in this paper. The VAS arrays which have great flexibility in the control of the aperture excitations are employed to synthesize low/ultra-low sidelobe patterns in the PD radar system, and the optimized time sequences obtained via the differential evolution (DE) algorithm is used to minimize the average power loss due to the time modulation. Numerical simulation results of the signals transmitted and received by PD radar based on the VAS arrays show that the time modulation changed the waveforms of the signals in time domain but the received signals also contain the correct range and velocity information of the moving target.

Monobit Subsampler for Digital Downconversion in Pulse-Doppler Radar Applications

This paper introduces a monobit RF subsampling technique for digital downconversion in pulse-Doppler radar systems. Design considerations for this application include the level of quantization imbalance given a noise-only input, the relation between input and output signal-to-noise ratio (SNR), the affect of jitter over the complete dynamic range of operation, and sensitivity to intermodulation distortion. An RF integrated circuit is designed to demonstrate the monobit subsampling approach. Measured results show excellent agreement with theoretical predictions. The device can detect a 495-MHz signal at input SNR levels less than -30 dB using a 1-MHz sampling clock. Excellent performance is maintained even in severe timing environments showing more than 400 ps of rms clock jitter.

Identification of Any Aircraft by Its Unique Turbulent Wake Signature

The theoretical groundwork for the detection of any aircraft from its unique turbulent wake signature will be discussed and practical methods by which to implement the theoretical result will be recommended. During the mid 1990’s, NASA conducted research on the detection of atmospheric turbulence through the use of light detection and ranging equipment (LIDAR). This lidar technology was able to detect turbulent disturbances by the Doppler shift in the frequency of laser-emitted energy that is scattered from atmospheric aerosols. Using this technology, the detection of turbulent disturbances physically created by the passage of aircraft through the atmosphere can be developed. Traditional aircraft detection methods include pulse-Doppler radar systems that measure the frequency shift of RF signals reflected off the skin of an aircraft. This method is currently being defeated through stealth technology. In a military application, lidar turbulent detection would be able to spot the unconcealable turbulent disturbances caused by aircraft, thereby defeating current stealth technology. In addition, research suggests that turbulent wake generators (i.e. aircraft) have unique turbulent energy signatures. Using the principles of turbulent self-preservation, models can be created to predict both Reynolds stress and momentum defect signatures of aircraft as a function of their altitude and airspeed. By using statistical analysis of the turbulent wake, the Reynolds stress or momentum defect can be compared against computed models to determine the identity of the aircraft being targeted. The theoretical and practical manner by which this can be achieved is discussed and examples of aircraft ranging from the F-15, F-16, F-18, and B-52 are provided.

An algorithm of data representation in a pulse-Doppler radar systems

A new algorithm is suggested for organization of data in systems for processing three-dimensional images of surfaces as applied to an airborne pulse-Doppler radar system.

Diversity Waveform Signal Processing for Delay–Doppler Measurement and Imaging

Bell, M. R., and Monrocq, S., Diversity Waveform Signal Processing for Delay–Doppler Measurement and Imaging, Digital Signal Processing 12 (2002) 329–346 Coherent pulse–Doppler radar systems, whether used for synthetic aperture imaging or surveillance purposes, generally transmit a coherent pulse train made up of identical pulses. While these pulses may contain complex modulation—for example, linear FM chirps or frequency and phase coding—the fact remains that these pulses are usually identical. In this paper, we consider the potential advantages of pulse trains made up of pulses that are distinctly different from pulse-to-pulse. In particular, we investigate a signal processing algorithm that provides increased resolution and discrimination through delay–Doppler sidelobe suppression in the region surrounding the mainlobe of the delay–Doppler response.

A Millimeter-Wavelength Dual-Polarization Doppler Radar for Cloud and Precipitation Studies

Abstract A pulse Doppler radar system operating at 35 GHz and having full polarization (linear and circular) diversity capability is described. Separate antennas are used for the transmitter and the receiver because this design approach allows better overall radar sensitivity. The transmitter operates in the double-pulse mode to optimize the unambiguous Doppler velocity measurable with the system. A polarizer capable of handling about 200 kW of peak power when pressurized with sulfur hexafluoride (SF6) at 25 psi was developed for the transmitter. The radar system has built-in test sequences for checking the gain and alignment of the transmitter and receiver antennas. The dual-polarization intermediate frequency (IF) receiver has a total of six analog channels. A very flexible data acquisition and processing system has been developed to allow both coherent and incoherent dual-polarization measurements to be performed; the system includes a microprocessor-controlled pulse-pair processor and a minicomputer w...

Neutral wind measurements over Waltair using meteor wind radar

A coherent pulse Doppler Radar System at Waltair (17°43′N, 83°18′E) has been used to measure neutral winds in the altitude range 80–110 km. Preliminary results obtained during July and August 1979 are presented. The diurnal component is found to be the dominant tidal mode for most of the time. The results are compared with meteor wind observations at other stations.

Rotating Blades Radio Interference in a Helicopter-Borne CW Doppler Radar

Radio interference generated in a helicopter-borne continuous wave (CW) Doppler radar system due to the rotating blades is analyzed. This problem has been previously treated for the case of pulse Doppler radar systems with very narrow (near zero) beamwidth. In this case the strong interference component returning directly from the blades (with no ground reflection) need not be considered as it reaches the receiver when it is still blinded. In the case of a CW Doppler radar, however, this interference component must be included. Numerical calculations show that the total blade interference power level, dominated by the direct component, is higher than that of the direct ground clutter in the radar clutter region. It decreases approximately as (f - fo)-4 in the radar clear region. It stays, however, well above the thermal noise level which might cause false alarm and degrade the radar performance.

Near-Field Analysis of Helicopter Rotating Blades Modulation Interference

A near-field analysis is carried out to obtain the level of modulation interference due to rotating blades in a helicopter-borne pulse Doppler radar system. The interference power spectra are calculated for different values of antenna depression angle and helicopter (radar) speed at a constant helicopter altitude of 300 m. Numerical results for the case of 1 kW radiated power show that blade interference level is about 5 to 8 dBW/Hz less than that of the direct ground clutter in the clutter region. It extends, however, into the clutter-free region which may cause false alarms and degradation of the radar performance.

Radio Interference in Helicopter-Borne Pulse Doppler Radars

Radio interference generated in a helicopter-borne pulse Doppler radar system due to rotating blades is analyzed for the case that blades are located in the far field region of the radar antenna. A first-order estimate of the blade interference power spectrum is obtained as a function of antenna depression angle and radar (helicopter) altitude and speed. Numerical calculations show that blade interference is very weak compared with the direct ground clutter. It extends, however, into the clutter-free region which causes false alarms and degrades the radar performance.

Recursive computation of the discrete fourier transform, with applications to a pulse-Doppler radar system

A recursive method of computing the discrete Fourier transform (DFT) is described. Applications of this method in a range-gated pulse-Doppler radar system is discussed. The filter bank of the pulse-Doppler radar receiver is shown to be realizable by a set of digital filters that can be obtained directly from the DFT. Filter responses are obtained and an example is given to show the computational speed necessary in an actual application.