Different recent approaches have demonstrated the feasibility of applying millimetre-waves (MMW) for the imaging of objects at a person's body. The utilisation of MMW allows for the detection of both metallic and non-metallic objects. In order to reduce costs a low number of transmit-receive modules should be used. Furthermore, the person should also be illuminated from different angles in order to avoid shadowing effects as good as possible. A way to fulfil these two conditions is to place one sensor above and another one below the person and either rotate the person standing on a turntable (inverse synthetic aperture radar, ISAR) or move the sensors on a circular path around the person (synthetic aperture radar, SAR). The goal of the reconstruction is to obtain information about the shape of possible threats and their positions in all three dimensions. During processing as a first step, the reconstruction is done along range and azimuth, which span the principal surface given by the suggested sensor configuration. Afterwards, the third spatial dimension can be determined by combined evaluation of the resolution capabilities of the curved synthetic aperture and the interferometric phase of two coherent receiving channels of one sensor.

We present a bistatic extension of a broadband monostatic FMCW Radar working in the Millimetre-Wave (MMW) region and its bistatic imaging properties used for imaging purposes. Due to the different perspective of a bistatic setup compared to a monostatic one, additional information can be obtained.A wide bandwidth of approx. 10 GHz is used for the task of high resolution imaging as it could be used for the detection of threats at a person's body in security-sensitive environments. Since MMWs propagate easily through common clothing, it is feasible to image objects like concealed weapons worn under the clothing. MMW-Imaging of humans is one possibility to enhance the capabilities of nowadays security checkpoints, e.g. at airports.

Homeland security today presents a major field for technology improvement and systems development. For instance body scanners, commonly operated at airports, are basically metal detectors and therefore are not able to detect other potential hazards like ceramics or explosives as well. In this context millimeter-wave (MMW) radar systems are a promising approach, because the radiation does not present a health hazard to people under surveillance and readily passes through many optically opaque materials such as clothing fabrics. For indoor systems we propose to apply active and coherent sensors. Based on the principles of Synthetic Aperture Radar small physical apertures can be used in order to get very good resolved images providing all the image features necessary for localizing relevant objects. In order to get a view of the person from all sides either the person has to be rotated standing on a turntable or a sensor is moved on a circular path around the person. Additionally interferometric principles can be applied firstly in order to obtain a geometrically improved mapping of the reconstructed scene and secondly to reduce ambiguities related to numerical reconstruction.

To detect threats on a person's body surface the application of millimetre-waves is possible. In order to get a view of the person from all sides either the person has to be rotated standing on a turntable (Inverse Synthetic Aperture Radar, ISAR) or a sensor is moved on a circular path around the person (Synthetic Aperture Radar, SAR). The goal of the reconstruction is to obtain information about the shape of the threats and their positions in all three dimensions. At first the reconstruction is done along range and azimuth, which span the principal surface given by the sensor configuration. This paper reports on two methods to obtain the third spatial dimension. Due to the circular shape and its 3D focussing ability of the aperture this information can be obtained by the evaluation of the image focus. Secondly, if two coherent receiving channels are used, a possibility to achieve 3D spatial resolution is the processing of the interferometric phase. A comparison between these two will be presented.

We present a novel reconstruction algorithm of ω-k type which suits for wideband circular synthetic aperture data taken in stripmap mode. The proposed algorithm allows to reconstruct an image on a cylindrical surface. The range trajectory is approximated by Taylor Series expansion using only the quadratic terms which limits the angular reconstruction range (cross range). In our case this is not a restriction for the application. Wider areas with respect to cross range can be realized by joining several reconstructed images side by side to build a wider image by means of digital spotlighting.

We present design and realization of a broadband FMCW Radar working in the Millimeter-Wave (MMW) region. The usable frequency range lies between 91 GHz and 102 GHz. We use a homodyne radar setup. Thus only one MMW source is necessary which is used for TX and LO generation simultaneously. The complex RX radar signal is calculated by a Hilbert transform in order to avoid a broadband MMW IQ mixer. A free space calibration procedure is used to obtain a flat amplitude response and a fixed phase center. Static non-linearities of the transmitted chirp signal are compensated by predistortion of the VCO’s tuning voltage characteristic. A microwave coaxial delay line combined with a time domain resampling method corrects dynamic non-linearities. The ultra wide bandwidth of 11 GHz is necessary for the purpose of a high resolution imaging task. Due to the fact that MMWs propagate easily through common clothing it is feasible to image objects like concealed weapons worn beneath the cloth. Imaging of humans in the MMW region is one possibility to enhance the capabilities of nowadays security checkpoints, e. g. at airports.

We present design and realization of a broadband FMCW radar working in the millimeter-wave (MMW) region. The usable frequency range lies between 91 GHz and 102 GHz. The quadrature receiver signal is synthesized from a single homodyne receiver channel using Hilbert transform methods. This ultrawide bandwidth of 11 GHz is necessary for the purpose of a high resolution imaging task. Due to the fact that MMWs propagate easily through common clothing it is feasible to image objects like concealed weapons worn beneath the cloth. Imaging of humans in the MMW region is one possibility to enhance the capabilities of nowadays security checkpoints, e.g. at airports

Homeland security as a current issue brought up many questions about nowadays state of the art security relevant technologies both for civilian and military applications. Our motivation is related to security applications for airport environments especially in terms of people screening and object detection beneath the clothing. When developing a system for this environment one has not only to take into account good image quality but also issues like available space and financial resources of the airport's operator. In this paper we report about general solutions to this task and about our approach in the millimeter- wave region specifically.

Increasiug demands for screening personnel for concealed objects lead to additional research efforts related to suitable imaging systems and their industrial realization. In this context millimeter-wave systems are a promising approach, because the radiation does not present a health hazard to people under surveillance and readily passes through many optically opaque materials such as clothing fabrics. A survey of existing and proposed systems as well as an assessment of potential methods is presented. The results of basic experiments applied to a mannequin carrying concealed objects using a lens for local focusing are given. The results of this method, which is not suitable for real-time imaging, allow to assess the system??s imaging properties, which wiU he further developed to fulfill the data acquisition and processing time requirements for security checkpoints. The various applicable approaches to eflicient imaging configurations allowing for fast data acquisition are compared.

Basic experiments and results concerning MMW imaging of human beings with emphasis on people screening in safety crucial environments are discussed. Common network analysis equipment and several mechanical positioning systems are intended to be used to obtain significant pixel images of the human body and other concealed objects. Especially, lens focused pixel images are presented.