Abstract
Continuous Wave (CW) radars systems, especially air-coupled Ground-Penetrating Radar (GPR) or Through-Wall Imaging Radar (TWIR) systems, echo signals reflected from a stationary target with high energy, which may cause receiver saturation. Another effect caused by reflection of stationary targets is noticeable as background within a radargram. Nowadays, radar systems use automatic gain control to prevent receiver saturation. This paper proposes a method to remove stationary targets automatically from the received signal. The method was designed for a radar system with a moving platform, with an assumption that the distance between the surface and target is constant. The design is proposed of an SFCW radar with an integrated system for real-time multiple static target Echo Cancellation (EC). The proposed EC system removes the static target using active Integrated Circuit (IC) components, which generate the corresponding EC signal for each frequency step of the SFCW radar and sum it with the received echo signal. This has the main advantage of removing even multiple echoes at any distance, and excludes the need for a high-dynamic-range receiver. Additionally, the proposed system has minimal impact on the radar size and power consumption. Besides static target removal, the antenna coupling can be removed if the signal appears to be constant. The operating frequency was selected between 500 MHz and 2.5 GHz, due to the limitation of the used electronic components. The experimental results show that the simulated target’s echo using a cable with a known length could be suppressed to up to 38 dB. Experimental results using a moving radar platform and the real environment scenario with static and dynamic targets, show that the proposed EC system could achieve up to 20 dB attenuation of the static target. The system does not affect any other target of interest, which can even move at any distance during the measurement. Therefore, this could be a promising method for further compact implementation into SFCW radars, or any other radar type that generates CW single frequencies.
Highlights
A radar is a nondestructive sensor that was first used for military applications
The experimental results provide a proof of concept of the proposed Echo Cancellation (EC) system with a simulated target and a static reflection
The Stepped-Frequency Continuous Wave (SFCW) radar design with an integrated EC system is proposed in this paper
Summary
A radar is a nondestructive sensor that was first used for military applications. Nowadays, radars can be found in industrial applications, healthcare and medical applications, remote sensing, and subsurface investigation [1]. Due to the fact that the signal travels through a highly lossy medium—soil—the sensitivity of such a sensor is crucial Another scenario where the observed scene and required performance are similar would be in through-wall imaging radar applications [16,17,18,19]. This kind of system has become especially popular, since no physical contact is needed between the investigated medium and the antenna In this scenario, does attenuation cause a problem, and the fact that the Radar Cross-Section (RCS) of the observed surface can be several times larger than the RCS of the target of interest; RCS is a measure of the object‘s ability to reflect the signal back to the direction of the receiver and does not relate directly on the object‘s area, and considers frequency, aspect angle, and polarization [24]. The bandwidth could be increased further, but was limited due to the components, such as RF amplifiers and antennas
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