Space scanning FMCW-based two-dimensional frequency diverse array radar

The frequency-modulated continuous wave (FMCW)-based frequency diverse array (FDA) radar concept is extended to two dimensions (2D). The radar operates as a linear pulsed FMCW/FDA in the transmission (TX) mode while it operates as a pulsed FMCW/phased array (PA) in the receiving mode. It is shown that the FDA has the capability of scanning a 2D angular sector in a single pulse TX. It is shown that local instantaneous frequency bandwidth is much smaller than the radiofrequency (RF) frequency deviation of linear frequency modulation. Positive and negative slope TX/RF locations offer frequency diversity. The low signal-to-noise ratio of FDA is well compensated due to target temporal decorrelation diversity in the observation time and by the cumulative detection scheme used. Time domain and frequency domain signal processings are described. A Kuband direct digital synthesis-based FDA radar design is compared by a corresponding equivalent PA radar

Prospects of FMCW-based frequency diverse array radar

The linear frequency modulated (LFM) frequency modulated continuous wave (FMCW)-based frequency diverse array (FDA) radar concept is investigated in detail. The radar operates as a linear pulsed FMCW/FDA in the transmission (TX) mode while it operates as a pulsed FMCW/phased array (PA) in the receiving mode. The issues such as low signal-to-noise ratio (SNR) of FDA, the time-angle scanning and time-range ambiguities are studied. It is shown that the local instantaneous frequency bandwidth is much smaller than the radio frequency (RF) deviation of LFM. Positive and negative slope TX/RF locations offer frequency diversity. Time domain and frequency domain signal processings are described. A Ku band direct digital synthesis-based FMCW/FDA radar example based on the cumulative detection scheme is given and compared with an equivalent FMCW/PA radar

Pulsed FMCW waveform design for LPI radars based on stretch processing

An FMCW radar waveform design based on stretch procesing is described. Transmit (TX) and Receive (RX) functions are separated in time. A single antenna with no isolation problems can be used. A rigorous analysis of coherent processing is presented. Advantages and disadvantages are discussed. Compared to Pulsed Doppler Radar (PDR) this waveform has significant LPI properties. A generic design example is also given. © 2012 EUROPEAN MICROWAVE ASSOC

An Inverted L-Shape Fed Microstrip Patch Antenna for Mobile Communication

This paper proposes the configuration of a novel wideband patch antenna system suitable especially for indoor mobile communication applications. This configuration consists of an elevated patch antenna, which has different feed structure from classical patch antenna feed configurations that the antenna is fed by an inverted L-shape structure. The antenna structure is designed, simulated and manufactured in order to be used in mobile communication applications when used in pairs that its operation bandwidth spans 1900-2700 MHz covering Bluetooth, Wireless Local Area Networks (WLAN) and Universal Mobile Telecommunications System (UMTS) bands. Simulation and measurement results show that the antenna has wide beamwidth, low return loss and cross polarization; but, comparably higher back lobe level making the antenna more suitable for indoor applications. However, the antenna can be modified to be used in outdoor applications by increasing the ground plane size, which results in lower back lobe levels

Mitigating the Multipath Effects of Low Angle Monopulse Tracking by Even Difference Pattern

In this study, low angle monopulse DF error due to multipath is dealt with using even difference pattern in a monopulse system. It is shown that the complex angle processing based on this approach has a potential to solve the problem. The multipath problem is modelled using both the specular and the diffuse scattering, while the random nature of the latter is also taken into account

Narrow band wide angle scanning circular frequency diverse array radar

One dimensional Linear Frequency Diverse Array (FDA) is extended to a circular two dimensional FDA array (CFDA). The CFDA operates as a pulsed FDA in the transmission (TX) mode while it operates as a pulsed phased array (PA) in the receiving (RX) mode. CFDA has a constant antenna pattern steering property in the plane of the circle while it has FDA scanning property in the orthogonal plane. This is achieved by assigning frequency offsets to the elements of the array cosinusoidally which changes with the steer angle, making the CFDA narrow band. The matched filter (MF) for pulse compression is also designed for a particular direction of interest

Zero crossing counter for accuracy improvement of FMCW range detection

For civil and military purposes FMCW radars are widely used. The theoretical background is well-established. Nevertheless, improvement of various aspects of these radars is still required. Signal processing is one of the crucial points of the system which determines the capabilities of the radar. In this study a zero crossing detector implementation, which can be efficiently used for target detection and range calculation in short range FMCW range detector is proposed. The duration between consecutive zero-crossings are used as the data instead of the number of cycles per unit time. Experimental evaluation of its performance is also given

Extraction of target poles from electromagnetic scatter signals by using page distribution for target recognition Hedef tanima amaci ile page daǧilimi kullanarak elektromanyetik saçilim sinyallerinden kutup çikarimi

In this paper, we work on the electromagnetic target recognition problem based on the scattered field measurements. These measurements were obtained both in frequency and time domains by using two 0.8-12 GHz horn antennas in bistatic position and HP8720D vector network analyzer. First, the theory of electromagnetic scattering from a target and singularity expansion method (SEM) are summarized. The importance of complex natural resonance frequencies (CNR) in identification problem is discussed in this part. Afterwards, the results of CNR extraction from the scattered data of three dielectric spheres with different sizes and permitivities are presented by using time-frequency techniques to discriminate these targets from each other. It is also demonstrated that Page distribution produces much better results in this respect as compared to Wigner distribution. © 2005 IEEE

Monopulse Direction Finding For Linear Frequency Modulation Based Frequency Diverse Array

Novel methods for monopulse direction finding for linear frequency modulation based frequency diverse array (LFM-FDA) are introduced and experimental results are presented. Amplitude comparison monopulse technique constitutes a part of these methods. Radar operation is continuous wave (CW); in order to apply amplitude comparison monopulse technique on LFM-FDA, specific customizations are suggested, such as null tracking. One of the monopulse direction finding methods is implemented on an LFM-FDA setup. Results show that +/- 2 degrees direction accuracy for approximately 20 degrees beamwidth is obtained for 60 degrees azimuthal angular coverage in anechoic chamber