Search

The idea of Ku-band transceiver frequency conversion module design based on 3D micropackaging technology is proposed. By using the double frequency conversion technology, the dual transceiver circuit from Ku-band to L-band is realized by combining with the local oscillator and the power control circuit to complete functions such as amplification, filtering and gain. In order to achieve the performance optimization and a high level of integration of the Ku-band monolithic microwave integrated circuits (MMIC) operating chip, the 3D vertical interconnection micro-assembly technology is used. By stacking solder balls on the printed circuit board (PCB), the technology decreases the volume of the original transceiver to a miniaturized module. The module has a good electromagnetic compatibility through special structure designs. This module has the characteristics of miniaturization, low power consumption and high density, which is suitable for popularization in practical application.

An antipodal Vivaldi antenna (AVA) with band-notched characteristics is proposed in this paper for ultra-wideband (UWB) applications. For UWB systems, there will be some interference from the narrow band systems. The proposed antenna adopts resonant parallel strip (RPS) to reject an unwanted narrow band. It is easy to tune the RPS to eliminate the interference band. To validate this approach, a printed AVA with RPS is simulated and fabricated. From 2 to 9 GHz, the proposed antenna shows a good result with approximate 2:1 VSWR, an average gain of 6.5 dB, and stable radiation patterns except the notched band. At the center frequency of the notched band, the measured results show that the VSWR is more than 8:1, the realized gain is less than −10 dB and a messy radiation pattern is achieved. The simulated and measured results are in good agreement.

A novel planar printed log-periodic dipole array (LPDA) antenna fed by tapered microstrip line (MSL) to double sided parallel strip line (DSPSL) is proposed in this paper. The proposed antenna adopts MSL feeding approach from backside. Using this feeding technique makes the printed LPDA antenna easier to be integrated into radio frequency (RF) circuits. In this paper, four layers are used to construct the antenna. The four layers of the printed LPDA antenna are printed on three thin dielectric substrates which are integrated together. To validate this approach, a printed LPDA antenna is simulated and fabricated for operating in the S and C bands (2.5–6 GHz). The antenna showed a good result over the whole frequency range with 2 : 1 VSWR, an average gain of 6.5 dB, and stable radiation patterns. The measured results are in very good agreement with simulations.

Based on fractional Fourier transform (FRFT) and mode-space algorithm of circular arrays, a new 2D direction of arrival (DOA) estimation algorithm of linear frequency modulation (LFM) signals is proposed in this paper. Firstly, we construct a new array data model based on the fact that the LFM signal has the energy concentrated performance in the fractional Fourier transform domain (FRFD), and then we use the mode-space algorithm to get a new array manifold matrix of the virtual linear array. Finally we use the least square (LS) method to realize 2-D DOA estimation of LFM signals and the simulation results verify the effectiveness of the algorithm proposed by this paper.

With the developments in radar signal processing, it is more common that the received signals are the combinations of noncircular and circular ones. Some variations of MUSIC and ESPRIT have been developed to cope with the case. One typical method has been discussed in [F. Gao, A. Nallanathan, Y. Wang, “Improved MUSIC Under the Coexistence of Both Circular and Noncircular Sources”, IEEE TRANSACTIONS ON SIGNAL PROCESSING, vol.56, no. 7, pp.3033–3038], where all the sources are completely polarized (CP). In this correspondence, an algorithm named conjugate MUSIC is proposed to estimate the Direction-of-arrival (DOA) of partially polarized (PP) signals. Compared with the conventional MUSIC, the conjugated version improves the estimation accuracy by exploiting the noncircularity. Numerical examples show the effectiveness of the proposed method.

Radar stealth technology plays an important role in modern warfare, where the most challenging topic is antennas' radar cross section (RCS) reduction. Absorptive frequency selective surfaces (AFSS) can effectively reduce the RCS of antenna system whereas radiation performance is not affected, achieving aircraft stealth. In this paper, a single-layer AFSS is proposed with polarization insensitivity. This metamaterial has two absorption bands separated by one pass band. Compared with existing structures, it has the advantages of simple structure, easy fabrication and bilateral electromagnetic wave absorption.

In this letter, a segmentation method is proposed based on an adaptive Bayesian non-local MRF (ABNL-MRF) model. Aimed at the multiplicative speckle existing in SAR images, a patch-similarity measure based on a ratio of probability is introduced firstly. Then non-local similar pixel-blocks are adopted to guide the segmentation of the noisy image. However, non-local method over-smoothes edge regions and makes them inaccurate though it is robust for speckle. A rectification index is designed according to the homogeneity degree of local window. Based on the value of rectification index, a non-local constraint term is adaptively integrated into the potential function. Thus a suitable prior is defined that guarantees both the smoothness of the denoised image and the preservation of its structure. Experimental results demonstrate the very good performance of the proposed method.

When applied to a broadband high-resolution radar, the traditional approaches of CFAR (Constant False Alarm Processing) can't strike a balance between efficiency and performance. This paper proposes a new approach of CFAR which is realized on a multicore DSP platform: TMS320C6678. First, two-dimensional OSCA-CFAR algorithm has been improved by adding the extraction from range and azimuth. Then the algorithm is realized on a DSP platform, where core 0 is a master core and core 1 and core 2 are data cores to execute Ping-Pong processing. DDR3 memory works as a large data sharing point in 6678. In 6678, Seampore2 is used to synchronize data and EDMA3 is utilized to transmit data at high speed between inside and outside of the cores. When applied to the broadband high-resolution radar area, the experiment results show that the proposed CFAR algorithm can greatly improve the operational efficiency while meeting the accuracy requirement. It is a good candidate for real-time image processing based on the airborne radar or the missile radar.

In order to get high output power to load, a methodology called load-pull and source-pull is often utilized to select the optimal input and output impedance. Based on the methodology, using the GaN HEMT CGHV1F006S from CREE, simulation is performed by using microwave simulation software ADS. The results indicate that within 8.5GHz–10.2GHz, Delivered Power is higher than 37 dBm with Gain Ripple being lower than 1dB and power-added efficiency (PAE) is higher than 35% when the input power is 28dBm and the amplifier is overdriven at Class AB condition. The results show that the methodology is effective and reasonable.

This paper presents a printed dipole antenna with a parallel metal plate, exploring the impact of the distance and relative position between the metal plate and the printed dipole antenna. The characteristics of the antenna such as reflection coefficient S11, radiation patterns, and realized gain are given. There are many differences between the printed dipole antenna with a parallel metal plate and without a metal plate. Our paper also presents these differences.

Micro-motion characteristics of the sea corner-reflector jamming and the ship are different. The corresponding time-frequency feature extracted from the time-frequency representation (TFR) of the target echo can be used to discriminate the corner-reflector jamming and the ship. Three parameters, including the micro motion period, the time-frequency spectrum entropy and the maximum of micro-Doppler half-period frequency difference, are applied to describe time-frequency feature of the target. An identification method based on those time-frequency feature parameters is presented to discriminate the corner-reflector jamming and the ship. Experiments with measured data validate the effectiveness of the identification method via time-frequency feature.

The millimeter wave broadband coherent radar has the capabilities of high range resolution and Doppler resolution, which provides a new approach for anti-chaff jamming. Based on the echo model of broadband coherent radar, the range Doppler two-dimensional profile of the target is derived. Then the differences of the range Doppler two-dimensional profile between the echoes of the ship and the chaff jamming are analyzed. A range Doppler two-dimensional extended target detector based on Otsu is applied to detect the target region. Three characteristic parameters based on the range Doppler two-dimensional profile are proposed to discriminate the ship and the chaff jamming. An identification method based on those characteristic parameters is presented to discriminate the chaff jamming and the ship. Experiments with measured data validate the effectiveness of the identification method via range Doppler two-dimensional profile.

As the traditional radar system can't quickly and effectively identify group targets, this paper uses a millimeter-wave radar system to identify, sort and track the sea fleet targets. The radar scans the sea surface firstly to get the DBS image, then the image is processed by the CFAR processor to detect the fleet targets, and finally according to various parameters provided by the INS (inertial navigation system), the positional relationship between the radar and a specific target can be worked out. Then the radar will set the servo system so that the antenna can beam the targets area and then the radar can go to monopulse tracking quickly. The results show that: the system and algorithm proposed by this paper can identify and sort the group targets and track the specific target quickly and steadily. It is suitable for the airborne or missile fields.

In this article, the size of the cavity combline filter is greatly reduced by using capacitively loaded disks and reentrant combline resonators. It has low loss, high Q quality factor and wide stopband. The feasibility of this method is analyzed theoretically. The characteristics of the structure are studied by simulations. The size of the fabricated filter is almost 50% of the size of the conventional cavity combline filter. The measured S parameters of the two filters are given. At 1575 MHz, which is the operating frequency of the global positioning system receiver antijamming antenna array system, the inserted loss of the improved filter is 0.702 dB. To minimize the interference from the Bei-Dou double star positioning system, at 1615 MHz, which is the operating frequency of this system, the out-of-band rejection of the improved filter at this frequency is 27.010 dB. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 910–913, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24191

This paper reports that an analytic method is used to calculate the load responses of the two-wire transmission line excited by a plane-wave directly in the time domain. By the frequency-domain Baum–Liu–Tesche (BLT) equation, the time-domain analytic solutions are obtained and expressed in an infinite geometric series. Moreover, it is shown that there exist only finite nonzero terms in the infinite geometric series if the time variate is at a finite interval. In other word, the time-domain analytic solutions are expanded in a finite geometric series indeed if the time variate is at a finite interval. The computed results are subsequently compared with transient responses obtained by using the frequency-domain BLT equation via a fast Fourier transform, and the agreement is excellent.

Alternating direction implicit finite difference time domain (ADI-FDTD) method is unconditionally stable and the maximum time step is not limited by the Courant stability condition, but rather by numerical error. Compared with the conventional FDTD method, the time step of ADI-FDTD can be enlarged arbitrarily and the CPU cost can be reduced. 2D perfectly matched layer (PML) absorbing boundary condition is proposed to truncate computation space for ADI-FDTD in dispersive media using recursive convolution(RC) method and the 2D PML formulations for dispersive media are derived. ADI-FDTD formulations for dispersive media can be obtained from the simplified PML formulations. The scattering of target in dispersive soil is simulated under sine wave and Gaussian pulse excitations and numerical results of ADI-FDTD with PML are compared with FDTD. Good agreement is observed. At the same time the CPU cost for ADI-FDTD is obviously reduced.

A finite-different time-domain (FDTD) algorithm is applied in this paper to study the bistatic electromagnetic(EM) scattering by a conductive cylinder covered with inhomogeneous, collision, cold, time-varying plasma. The collision frequency of plasma is a function of the electron density and the pressure of the background gas. The plasma density follows any prescribed distribution function of the rise time of plasma and the radius of the column. The bistatic radar cross section (RCS) of the conductive cylinder covered with inhomogeneous time-varying plasma and inhomogeneous steady-state plasma is calculated under different conditions. The results illustrate that a plasma cloaking system can successfully reduce the RCS of the conductive cylinder.

A finite-difference time-domain (FDTD) algorithm is applied to study the electro-magnetic reflection of conduction plane covered with inhomogeneous time-varying plasma, homogeneous plasma and inhomogeneous plasma. The collision frequency of plasma is a function of electron density and plasma temperature. The number density profile follows a parabolic function. A discussion on the effect of various plasma parameters on the reflection coefficient is presented. Under the one-dimensional case, transient electromagnetic propagation through various plasmas has been obtained, and the reflection coefficients of EM wave through various plasmas are calculated under different conditions. The results illustrate that a plasma cloaking system can successfully absorb the incident EM wave.

Circular array interferometer with analog phase detector requires higher signal to noise ratio than the digital phase detection structure, which leads to lower accuracy of direction-of-arrival (DOA) estimation. T o overcome this, we proposed two kinds of methods which can work together. They are the modified phase accumulation method (MPAM) and the optimal baseline pair method (OBPM). Modified phase accumulation method solves the problem caused by phase jump near ±π in analog phase detection structure in conventional phase accumulation method (CPAM). Taking the azimuth corresponding to one certain baseline pair as reference, OBPM outputs the azimuth and elevation corresponding to the highest accurate baseline pair. Simulation results show the effectiveness and correctness of these two methods. At last, we introduced the FPGA implementation about the two methods. By taking advantage of the parallel architecture, we saved the processing time.

The high cross-polarization of the microstrip integrated balun-fed printed dipole antenna cannot meet the demands of many engineering applications. This kind of antennas has high cross-polarization levels (about −20 dB). And we find that the high cross-polarization radiation is mainly produced by the microstrip integrated balun rather than the dipole itself. The very limited method to lower the cross-polarization level of this kind of antennas is to reduce the substrate thickness. In this paper, to improve the low cross-polarized performance, firstly, an equivalent model is presented to analyze the cross-polarization radiation. Secondly, a novel structure with low cross-polarization is proposed. The microstrip integrated balun is enclosed by a center slotted cavity. The E-field of the microstrip integrated balun is transformed parallel to the dipole arms by the slot, so the radiation of the cross-polarized component is suppressed. Measured results show that this structure can achieve a bandwidth wider than 40% while reducing the cross-polarization level to less than −35 dB within the frequency band.

A new frequency-selective surface (FSS) with loadings is introduced in this paper and analyzed by way of period moment methods (PMMs). The simulated results show that FSS may operate in different bands and especially generate a large reduction in the resonant frequency for a fixed unit cell size through different loadings. This provides a new orientation in the development for FSS. Practical circuits are fabricated, and the measured results agree well with the simulated results.

The picosecond photoconductive switches are developed and used to detect the pulse laser waveform. By using the photoconductive switches, an novel lab model of ultra-wide band(UWB) radar is also developed. The experimental results are given to show the performances of the switches and the UWB radar.

To solving the isolation problem of transmitting-receiving antenna in very-near anti-missile system, this letter analyses the equivalent model of AMC, which is made of high-impedance electromagnetic surface, and shows the relationship between its reflectance and phase offset. Then a novel method is brought to improve the isolation by the AMC and the experiments show that this method is able to make the isolation reach −80dB in a 200M band. So it has a very huge application value because of its simple structure and low cost.

Ultra wideband (UWB) antenna is widely used in UWB communication, radar and electronic warfare in recent years. UWB antenna is indispensable in impulse radar, which transmits and receives short electromagnetic pulse signals, and preserves the waveform well. To detect and track moving-target, UWB time-domain antenna array is studied in this paper. Firstly, the theory of time-domain antenna array scan is analyzed, some useful conclusions are achieved. Then, an experiment system of UWB time-domain antenna array scan is built, which includes an antenna array, delay controller and other equipments. Finally, many experiment results are made to validate the theory of UWB time-domain antenna array scan.

To reduce phase noise of microwave-band frequency synthesizer based on phase-locked loop(PLL), the method that the output signal of VCO is mixed with a Lo signal and the IF signal is detected, is proposed. Then, the compatible loop filter is designed. Finally, the experimental results prove that the phase noise of improved frequency synthesizer is greatly lower than that of directly phase-locked synthesizer.

High impedance surface (HIS) is a kind of resonance-type microwave photonic crystals. In this paper, the HIS is used for a circular waveguide antenna, a dielectric rod antenna and a waveguide-fed slot antenna as high-impedance ground plane (HIGP). The HIGP has a very obvious surface wave bandgap. Suppression or reduction of surface waves is expected to improve antennas efficiency, and to bring a reduction of back lobe level due to diffraction of surface waves. The measured radiation patterns show that an addition in the antennas gain and a distinct reduction in the back lobes if the antennas work frequency are in the HIGP surface wave bandgap.

Vessel classification using inverse synthetic aperture radar (ISAR) imagery is important because it can be used for maritime surveillance and has a high military value. We propose a vessel classification algorithm based on multifeature joint matching. We first utilize a preprocessing method to eliminate the vessel wakes and strong sea clutter, which interfere with feature extraction. In view of the different categories of vessels, we then propose a new two-dimensional strong scattering points encoding (SSPE2-D) for vessel recognition. Furthermore, we modify the method to calculate the number of peaks in the range profile in order to obtain a more accurate result. The high-resolution ISAR images obtained as a result are used to verify the effectiveness of our method. We also compare our proposed method with three other classification methods, and show that the classification rate obtained using our technique is more accurate than that from each of the other methods. Our experiments also show that the preprocessing and the new encoding feature improve classification accuracy.