The track-before-detect (TBD) methodologies jointly process more consecutive scans and show superior detection performance for the low signal-to-noise ratio (SNR) targets over the conventional methods. A TBD algorithm based on improved Randomized Hough Transform for dim target detection is proposed in this paper. This algorithm uses the sequence numbers of scans to make sure that the point pairs are selected from different scans, avoiding the unreasonable situation that the point pairs may be selected from the same scan in the traditional Randomized Hough Transform (RHT). Second, it introduces a new voting method. Based on the minimum Euclidean distance criterion, this voting method finds the optimal parameter cell to vote, making the voting result better than the traditional RHT. In addition, we not only increase score of the optimal parameter cell but also update the corresponding parameter, thus suppressing the deviation between the recovered track and the target's track. Simulation results demonstrate the proposed algorithm can detect the dim target more rapidly and accurately than traditional RHT, especially under the background of low SNR.
This paper presents a modified Gysel power divider (PD) with harmonic suppression performance by utilizing equivalent Π-shaped, T-shaped and Π-T-hybrid-shaped open stubs transmission line (TL) models. Explicit closed-form expressions for generating parameters of the equivalent TL models are derived based on the ABCD matrix analysis. The proposed PD not only features suppression at the hoped harmonic frequencies and flexible layout, but also maintains Gysel PD's high power handling advantage. For demonstration, the simulated and experimental results of three proposed PDs at 1 GHz implemented on microstrip are given.
A new design consideration is explored for a hair-pin resonator. A grounding via at the mid-point of the resonator acts as a perturbation to split the resonant frequencies. The via also suppresses even harmonics of the fundamental. The principle operation of the hair-pin resonator with a via is analyzed and verified by measurement. It is shown that such a hair-pin resonator can be made more compact using stepped impedance line. A compact 4-pole bandpass filter using the modified compact hair-pin resonator with a via is demonstrated. Simulation and measured results showed good agreement.
A new type of low-profile frequency selective surface (FSS) with an overall thickness of λ/40 and a second-order band pass frequency response is presented. The proposed FSS is composed of two metal layers, separated by a thin dielectric substrate. Each layer is a two-dimensional periodic structure with sub-wavelength periodic unit cells. By printing the same topology on each side of the substrate, a second-order frequency response is realized. To provide a physical insight into the operating mechanism, equivalent circuit networks are also investigated in each step of design procedure. Using the proposal technique, low profile and reduced sensitivity to angle of incident wave for both TE and TM polarizations are obtained and the overall thickness of the substrate is fairly thin. FSS samples are designed, fabricated, and installed in waveguide operating at X-band and a good agreement between the simulated and measured results is achieved.
This paper presented an estimation method of maximum effective isotropic radiated power (EIRP) and electro-magnetic field (EMF) strength of a wideband code-division multiple-access (WCDMA) base station based on over-the-air measurements of a pilot channel in a code domain. To verify the feasibility of the proposed method, we estimated the maximum EIRP and EMF strengths of the self-designed test base station, and compared them with EIRP and EMF values measured by the traditional test scheme. Then, we applied our estimation scheme to the inspection test for a commercial base station. The maximum difference between the estimated EIRP values from our method and the reported values is 1.3 dB. The estimated EMF results show more than 90% agreement with both the traditional EMF measurement value under a full-traffic load condition and the theoretical value. Therefore, it can be concluded that our proposed estimation method should be an effective inspection test for domestic base stations.
In this paper, we propose a method based on evolutionary computations for joint estimation of amplitude, Direction of Arrival and range of near field sources. We use memetic computing in which the problem starts with a global optimizer and ends up with a local optimizer for fine tuning. For this, we use Genetic algorithm and Simulated annealing as a global optimizer while Interior Point Algorithm as a rapid local optimizer. We set up Mean Square Error as a fitness evaluation function which defines an error between actual and estimated signal. This fitness function is optimum and is derived from Maximum likelihood. It requires only single snapshot to converge and does not require any permutations to link it with the angles found in the previous snapshot as in some other methods. The efficiency and reliability of the proposed scheme is tested on the basis of Monte-Carlo simulations and its inclusive statistical analysis.
A compact dual band notched Ultra-wideband (UWB) antenna with the multiple Hilbert curve slots is proposed that exhibits an impedance bandwidth from 2.5 GHz to 12 GHz. Hilbert curve slots result in band notch in the frequency range 5.15-5.5 GHz assigned to IEEE 802.11a and HYPERLAN/2 as well as 7.9-8.4 GHz band assigned to X-band uplink satellite communication systems. The antenna gain varies from 3 dBi to 5 dBi over the operating frequency. Stable radiation patterns throughout its operating frequency are obtained. Over all antenna size is 25 mm by 45.75 mm including the ground plane. Simulation and measured result of the proposed antenna are in good agreement.
Radar waveform synthesizer is a key component in radar system as it determines the best achievable resolution. A popular approach in radar waveform synthesis is the Direct Digital Synthesis approach where the signal is first generated in digital domain and converted into analog signal using a High Speed Digital-to-Analog Converter (HS-DAC). In this paper, a miniature and low cost radar waveform synthesizer is proposed. The synthesizer is targeted for Unmanned Aerial Vehicle (UAV) based radar system applications that require miniaturized equipment due to limited space in aircraft's fuselage. The signal synthesizer has been developed using Altera DE3 development board (Stratix III FPGA) and a custom made dual-channel 420 MSPS HS-DAC board. The proposed system is capable of generating various types of radar waveforms: a) Linear Frequency Modulated (LFM) or chirp pulse, b) Frequency Modulated Continuous Wave (FMCW), and c) Calibration Tone (Cal-Tone), for use in different types of radar applications. The distinguishing feature of the proposed synthesizer is its capability in reconfiguring the signal properties in real-time. The performance of the synthesizer has been benchmarked with commercially available radar waveform signal synthesizer and comparable performance has been observed.
A challenge faced by the information and communications technology (ICT) industry is the growing data volume and associated energy consumption. How to both meet a dynamic traffic demand at a consistently low energy consumption level is of importance from both commercial and climate change perspectives. This paper proposes a dynamic basestation concept that allows the number of active sectors to be adjusted in accordance with the traffic load. This is achieved through a novel switchable antenna design that can adjust the azimuth beam-width by using a tuneable reflector. Simulation and theoretical results show that the dynamic basestation can reduce the total operational energy of a cellular network by a peak of 75% and a mean of 38%.
This paper presents a compact microstrip stepped-impedance lowpass filter with ultra-wide stopband by using back-to-back C-shaped and triple C-shaped thin slots. The properties of several thin slots in the ground plane have been investigated in this paper. With the full-wave simulation results and a simplified equivalent model, the total equivalent inductance of the thin slots can be extracted at cutoff frequency for lowpass filter design purpose. On the other hand, the thin slots work as bandstop filter at the stopband of the lowpass filter for a better stopband rejection. The proposed lowpass filter with a cutoff frequency of 2 GHz shows a wide stopband with an over 25-dB attenuation up to 17.5 GHz. From dc to 2 GHz, the insertion loss is less than 0.3 dB and the return loss is greater than 20 dB. In comparison to the conventional stepped-impedance lowpass filter with the same passband performance, the proposed lowpass filter shows not only a 24.3% size reduction but also a better stopband rejection.
Large electrical systems or facilities can be satisfactorily shielded by using low-cost meshed metallic nets. Here the shielding effectiveness for two such planar meshes is calculated analytically and verified both experimentally by using cascaded reverberation chambers as well as numerically with results computed using a full wave electromagnetic solver. It is shown that all three methods agree and, in addition, that non-square shaped aperture meshes can be handled with an equivalent square area shaped aperture.
This paper presents a rectifying antenna (rectenna) for the harvesting of the microwave energy associated to UHF (Ultra-High Frequency) Radio Frequency IDentification (RFID) systems. The proposed device uses a capacitively loaded T-shaped monopole with a coplanar waveguide feeding line as receiving antenna and a five-stage voltage multiplier as rectifier. Experimental results demonstrating an RF-to-DC conversion efficiency of about 54% with an input power density of 80 μW/cm2 will be presented and discussed.
This paper proposed a new approach, which is based on minimum mean-square error (MMSE) criterion, for wideband signal spatial direction-of-arrival (DOA) estimation when there is array error, and the impact of random array error to the new algorithm is analyzed in this paper. Pass the wideband signal mixed with array error through a bank of narrowband filters to obtain narrowband signals, then recover the sparse representation of the narrowband signals by re-iterative method in the MMSE frameworks, and estimate the number and DOA of sources from the sparse representation. The new method do not require the number of sources for direction finding, furthermore, it can estimate the DOA of coherent signals and the robustness of new algorithm to array error is better than coherent subspace algorithms. The simulated results confirmed the effectiveness and robustness of the new method.
In this paper, an ultra-wideband (UWB) printed dipole antenna with semicircular dipoles is presented. A balanced microstrip line is used for feeding the dipole antenna. By introducing the loading disc, an ultra wide frequency band from 3.2 GHz to 15.6 GHz with VSWR < 2 is obtained. Through analyzing the surface current of the antenna, the equivalent array radiation models of standing wave current and traveling wave current are obtained. These models can well explain the antenna's radiation characteristic, which matches measured results well.
This paper investigates the performance of DCS1800/CD-MA-EVDO dual-mode dual-link (DM-DL) UE, and presents an effective solution which is based on our designed high isolation antenna for the UE local electromagnetic interference (EMI). To this end, a DCS1800/CDMA-EVDO DM-DL UE model is firstly brought out, together with its system model, interference analysis and performance evaluation. Simulated results show that the DCS1800 (CDMA-EVDO) local interference will cause a sharp deterioration of the CDMA-EVDO (DCS1800) receiving sensitivity. To solve this problem, then, a compact and high isolation double-band handset antenna is given with its structure designed and performance validated by measurement. On the basis of this antenna and existing UE bandpass filter, we introduce a solution called ``passive isolation" to eliminate the local interference. Finally, the performance of DCS1800/CDMA-EVDO DM-DL UE is researched again by our solution, simulated results indicate that the isolation effect is quite good and the DM-DL UE can work normally.
This paper presents a study of the effects of line width on the resonance frequency and bandwidth of a microstrip square-ring antenna at its primary resonance frequency. Although such ring antennas operating in TM11 mode are smaller than regular patch antennas, they are not explored much as they are considered to have poor bandwidth and efficiency at this mode. We have used a transmission line model to study their input characteristics and found that a non-uniform width ring antenna has significantly better (nearly double) bandwidth and radiation efficiency than a uniform width square ring antenna. Extensive simulations were done and a prototype non-uniform width square ring antenna is fabricated and tested to verify these results.
This paper presents an integrated millimeter-wave (mmW) low noise amplifier (LNA) which is implemented by using 0.15-μm baseline GaAs pHEMT technology. The design utilized modified co-planar waveguide (CPW) to perform a slow wave transmission line (TLine) with electromagnetic band gap (EBG) ground structures for the input/output matching networks. The low noise V-band LNA chip size was hence reduced by adopting the new EBG transmission lines. The developed amplifier exhibited a noise figure of 6.21 dB, and a peak gain of 17.3 dB at 66 GHz. Additionally, the amplifier has linear characteristics and its measured third-order intercept (IIP3) point is greater than -0.5 dBm a dc power consumption of 75 mW.
The increasing need for automatic identification and object tracking in supply chains has led to the development of radio frequency identification (RFID) systems. High frequency (HF) and ultra-high frequency (UHF) bands are frequently used because of their advantages over other bands. Although many HF and UHF band tags exist, some are unsuitable to handle the hostile environment of a supply chain. Therefore, this paper contributes to the research on a dual band RFID tag antenna operating on both the HF (13.56 MHz) and the UHF (919 MHz to 923 MHz) band, the UHF band used in Malaysia, by embracing the advantages of both HF and UHF bands to overcome the previously mentioned problems. The compact design is constructed by locating the UHF band antenna inside the HF band antenna and by reducing the number of turns of the HF band antenna compared to previous designs. The -10 dB bandwidth for the proposed design covers 12.9 MHz to 14.2 MHz for the HF band and 914.0 MHz to 929.0 MHz for the UHF band. The proposed antenna also overcomes the degradation problem by obtaining a high efficiency around 94% and a gain of 3.709 dB.
A simple method and structure to design a dual-band filter by using λ/4 stepped impedance resonators (SIRs) is presented in this paper. This filter has enhanced performance, including a good rolloff in the stopband and good insertion-loss response. The structure is compact and easy to fabricate. The circuit is investigated with the even-odd mode theory to prove the existence of transmission zeros. The dual-band response is analyzed by using SIR theory and the parallel-coupled line theory. Based on the proposed filter topology, two dual-band filters center operating frequency at 2.4 GHz and 5.2 GHz respectively with different configurations have been designed and one of them was tested, which validates the diversity of the filter configuration. Experimental results show that the measured and simulated performances are in good agreement. The overall area of the fabricated filter is 12mm * 12 mm.
This paper presents a novel design of a 4x4 two-layer wideband Butler matrix using a CB-CPW wideband multilayer directional coupler as well as a novel CB-CPW wideband elliptic directional coupler. With this configuration, the proposed matrix was designed to avoid crossovers as in conventional Butler matrices, thus reducing its size, losses and the design complexity while leading to a broad bandwidth of 3 GHz. To evaluate the performance of the proposed matrix, experimental prototypes of the directional elliptic coupler, the CB-CPW multilayer directional coupler and Butler matrix were fabricated and measured. Furthermore, a 4-element antenna array was connected to the matrix to form a beamforming antenna system at 5.8 GHz. As a result, four orthogonal beams were realized in the band 4.5-7.5 GHz.