Unlike phased-array antennas, which provide both rangeindependent and time-independent beampatterns, frequency-diverse array (FDA) antennas produce rangeangle and time-dependent beampatterns and, accordingly, autoscanning transmit beampattern (TB) characteristics due to the employment of a small frequency increment across its array elements. This article introduces the FDA antenna in the background of ultrawideband (UWB) radar and communication applications. The FDA range-dependent and autoscanning beampattern characteristics are analyzed for both continuouswave and pulsed signals. The FDA beampattern characteristics in narrow-band (NB) and UWB cases are illustratively compared. Potential applications in multipath mitigation and secure communications and low probability of interceptor (LPI) are discussed, along with their technical challenges, especially in antenna and propagation aspects, e.g., transmit beamforming and optimal array design.

Ultrawideband Frequency-Diverse Array Antennas: Range-Dependent and Autoscanning Beampattern Applications

Inspired by the fact that frequency diverse array (FDA) generates a time-variant transmit beampattern depending on both range and angle parameters, we propose joint utilization of the FDA and multiple-input multiple-output (MIMO) radar for counteracting mainlobe jamming signals. In doing so, the advantages of FDA and MIMO in range-time-dependent beampattern and increased degrees-of-freedom, respectively, are combined. The proposed algorithm development is based on eigenvalue projection and blocking matrix processing. Theoretical analysis and simulation results for evaluation of the FDA-MIMO framework are provided.

FDA-MIMO Signal Processing for Mainlobe Jammer Suppression

Frequency diverse array- (FDA-) based directional modulation (DM) is a promising technique for physical layer security, due to its angle-range dependent transmit beampattern. However, the existing schemes are not suitable for the broadcasting scenario, where there are multiple legitimate users (LUs) to receive the confidential message. In this paper, we propose a novel random frequency diverse array- (RFDA-) based DM scheme to realize the point to multi-point broadcasting secure transmission in both angle and range dimension. In the first stage, the beamforming vector is designed to maximize the artificial noise (AN) power, while satisfying the power requirement of LUs for transmitting the confidential message simultaneously. In the second stage, the AN projection matrix is obtained by maximizing signal-to-interference-plus-noise ratio (SINR) at the LUs. The proposed scheme only broadcasts the confidential message to the locations of LUs while the other regions are covered by AN, which promotes the security of the wireless broadcasting system. Moreover, it is energy efficient since the power of each LU is under accurate control. Numerical simulations are presented to validate the performance of the proposed scheme.

/pdf/broadcasting-directional-modulation-based-on-random-e6y0466vxa.pdf

Broadcasting Directional Modulation Based on Random Frequency Diverse Array

Unmanned aerial vehicles (UAVs) are widely applied in civil applications, such as disaster relief, agriculture and cargo transportation, etc. With the massive number of UAV flight activities, the anti-collision technologies aiming to avoid the collisions between UAVs and other objects have attracted much attention. The anti-collision technologies are of vital importance to guarantee the survivability and safety of UAVs. In this article, a comprehensive survey on UAV anti-collision technologies is presented. We firstly introduce laws and regulations on UAV safety which prevent collision at the policy level. Then, the process of anti-collision technologies are reviewed from three aspects, i.e., obstacle sensing, collision prediction, and collision avoidance. We provide detailed survey and comparison of the methods of each aspect and analyze their pros and cons. Besides, the future trends on UAV anti-collision technologies are presented from the perspective of fast obstacle sensing and fast wireless networking. Finally, we summarize this article.

Anti-collision Technologies for Unmanned Aerial Vehicles: Recent Advances and Future Trends

Unmanned aerial vehicles (UAVs) are widely applied in civil applications, such as disaster relief, agriculture and cargo transportation, and so on. With the massive number of UAV flight activities, the anti-collision technologies aiming to avoid the collisions between UAVs and other objects have attracted much attention. The anti-collision technologies are of vital importance to guarantee the survivability and safety of UAVs. In this article, a comprehensive survey on UAV anti-collision technologies is presented. We firstly introduce laws and regulations on UAV safety which prevent a collision at the policy level. Then, the process of anti-collision technologies is reviewed from three aspects, i.e., obstacle sensing, collision prediction, and collision avoidance. We provide a detailed survey and comparison of the methods of each aspect and analyze their pros and cons. Besides, the future trends on UAV anti-collision technologies are presented from the perspective of fast obstacle sensing and fast wireless networking. Finally, we summarize this article. 

/pdf/anti-collision-technologies-for-unmanned-aerial-vehicles-3uperhyc.pdf

Anti-Collision Technologies for Unmanned Aerial Vehicles: Recent Advances and Future Trends

Integrated wireless communications, radar sensing, and smart navigation is becoming increasingly necessary owing to their similar finite radio frequency (RF) electromagnetic spectrum resource [1]. By integration of various disciplines, a multitude of new and more intelligent services, such as smart city and ambient assistant living, can become available. For instance, using a joint waveform for both radar and communication applications, the occupied spectrum would be used in a more efficiently way and both applications could be operated simultaneously. Such an integrated radar and communication systems has been reported in multiple papers [2]–[9]. An early example of integrated radar and communication system is the National Aeronautics and Space Administration Space Shuttle Orbiter [10]. Another example is the intelligent transportation system [11], which allows the intelligent vehicles to autonomously sense the driving environment and cooperatively exchange the information data. Furthermore, the proposals for integrating cognitive radar and cognitive radio for efficient spectrum sharing are also suggested [12]. Many applications would possibly benefit from the availability of integrated navigation, sensing, and communications, which advantages can be summarized as follows [1]: (i) System cost is reduced and resource utilization is improved; (ii) The advantages of radar, such as high power and strong directivity, can be utilized to improve the communication quality and increase the effective sensing range; (iii) System automation level is enhanced.

FDA-OFDM for integrated navigation, sensing, and communication systems

Frequency diverse array (FDA) radar produces a time-variant transmit beampattern depending on both the range and angle parameters, which offers potential applications in electronic countermeasure scenarios, especially in the presence of mainlobe jamming signals. However, the range and angle of targets cannot be unambiguously estimated by a standard FDA radar due to its range-angle coupling response of targets. This paper proposes FDA and multiple-input multiple-output (MIMO) hybrid radar for counteracting mainlobe jamming signals, by jointly exploiting the advantage of FDA in range-angle-dependent beampattern and the advantage of MIMO in increased degrees-of-freedom (DOFs). The performance is evaluated by the cramer-Rao lower bounds (CRLBs).

He Huang

Papers

FDA-OFDM for integrated navigation, sensing, and communication systems

Frequency diverse array radar in counteracting mainlobe jamming signals