China
Africa
Explore chapters and articles related to this topic
Target Measurements Using Radar Networks
Published in Hai Deng, Zhe Geng, Radar Networks, 2020
Amplitude-comparison monopulse radar transmits a pulse at the predicted position of the target, and the target echo is received with two squinted beams that are separated in angle by a fraction of the beamwidth (Blair, 2010). It determines the target DOA relative to the antenna boresight with the in-phase part of the monopulse ratio, which is obtained by dividing the difference of the two offset received signals by their sum. If DOA estimation in both azimuth and elevation is desired, four squinted beams are used to receive the target echo, and two monopulse ratios are formed. It is also worth mentioning that when two targets are closely spaced with respect to the resolution of the amplitude-comparison monopulse, the measurements from them can merge into one single measurement and lead to significantly declined DOA estimation performance. To address the problem of unresolved targets, several approaches have been proposed in literatures (Blair & Brandt-Pearce, 2001; Wang et al., 2004; Zhang et al., 2005).
Tracking Radars
Published in Habibur Rahman, Fundamental Principles of Radar, 2019
A block diagram of an amplitude comparison monopulse radar with provision for extracting error signals in both azimuth and elevation is shown in Figure 10.13. Hybrid junctions generate the sum channel, the azimuth difference channel, and the elevation difference channel. Two phase-sensitive detectors are included to extract the angular error information, one for azimuth and the other for elevation, while the range information is extracted from the output of the sum channel. According to Page,5 the phase difference between channels must be maintained to within 25° or better. AGC is needed to maintain a stable closed-loop servo-control system for angle tracking. The AGC in a monopulse radar is achieved by employing a voltage proportional to the sum channel IF output to control the gain of all three receiver channels.
UWB full polarization single-plane monopulse reflector antenna
Published in Electromagnetics, 2023
Beam deviation factor for different values of F/D and feed displacement is investigated. Considering feed lateral distance and corresponding squint angle, reflector with the proper F/D ratio has been chosen. An equivalent Cassegrain antenna was proposed to obtain same effects as single parabolic reflector with large F/D. In addition to reducing the axial dimensions, it eliminates blockage caused by coupler and LNA. The feed is placed at virtual focal plane of the fabricated Cassegrain antenna. Outdoor measurement results indicated that the work in this paper is significant for the development of UWB monopulse radar. By adding one feed array to the proposed architecture, double plane full polarization monopulse with UWB can be realized.
The novel two-port hybrid ring dipole-like antenna with simultaneous sum and difference radiation patterns
Published in Electromagnetics, 2020
S. A. Alekseytsev, D. A. Bukhtiyarov, A. P. Gorbachev, D. S. Vilmitsky
The classical center-fed printed dipole antennas with simultaneous sum and difference radiation patterns have been used in various microwave areas to realize the coherent side-lobe cancellation, direction finding and monopulse radar (Jenn and Chua 2003). Besides, these antennas with the sum radiation pattern play the role of the printed quasi-Yagi assembly drivers that is an excellent discovery through the realization of high-efficiency push-pull power amplifier (Hang et al. 2001). This merger of the quasi-Yagi assembly and active circuits, often referred to as active-integrated antennas, paves the way for microwave circuit integration (Waterhouse 2007).