We present a pin-Traveling wave Photodetector (TWPD) on semi-insulating (SI) InP substrate at 1.55 μm wavelength window with an electrical bandwidth of more than 120 GHz, a line characteristic impedance of about 50 W, and microwave index matched to the optical group index. The internal quantum efficiency more than 99% for a 200μm long device is determined. The layer stack of the TWPD has previously utilized in a semiconductor optical amplifier (SOA). The TWPD can be monolithically integrated with passive and active components such as arrayed waveguide grating (AWG), Mach-Zehnder Interferometer (MZI), laser and modulator.
High-accuracy pulse repetition interval (PRI) estimation is meaningful for passive sensors to identify radar emitters. This paper considers the problem of estimating the PRIs of motionless radars in moving passive sensor systems. A modified method which based on observation calibration is proposed. This method can efficiently compensate the estimation bias induced by model mismatch, through calibrating the pulse time of arrival (TOA) measurements with emitter geolocation information. Performance analysis and simulation results show that our method can improve the PRI estimation accuracy significantly.
In this paper, we present a comprehensive framework from synthesis to implementation of active matched filters for UWB Impulse Radio. The method delays and sums UWB pulses coherently to strengthen the signal over white Gaussian noise. Theoretical analysis shows that the signal peak is maximized against noise, and an arbitrary transfer function could be realized by adjusting filter parameters. To verify the concept, a four-stage matched filter operating in 3-5 GHz with 360 degrees phase delay is demonstrated first. It is implemented in a commercial 2-μm GaAs HBT process and achieves a power gain of 13.8 dB with a 10 dB bandwidth of 1.3 GHz. Based on a similar architecture, another design is presented but with only half of the delay. It has a power gain of 15.9 dB at the center frequency of 4 GHz and a 10 dB bandwidth of 2.3 GHz. An advantage of the proposed method is a precise control of the impulse response that can be matched to either symmetrical or asymmetrical UWB pulses by taking a time domain design approach.
In this paper, a high gain, low side lobe level Fabry Perot Cavity antenna with feed patch array is proposed. The antenna structure consists of a microstrip antenna array, which is parasitically coupled with an array of square parasitic patches fabricated on a FR4 superstrate. The patches are fabricated at the bottom of superstrate and suspended in air with the help of dielectric rods at 0.5λ0 height. Constant high gain is obtained by resonating parasitic patches at near close frequencies in 5.725-5.875 GHz ISM band. The structure with 9 × 9 square parasitic patches with 1.125λ0 spacing between feed elements is fabricated on 5λ0 × 5λ0 square ground. The fabricated structure provides gain of 21.5 dBi associated with side lobe level less than -25 dB, cross polarization less than -26 dB and front to back lobe ratio of more than 26 dB. The measured gain variation is less than 1 dB and VSWR is less than 2 over 5.725-5.875 GHz ISM band. The proposed structures are good candidates for base station cellular systems, satellite systems, and point-to-point links.
This paper reports algorithm and technique for the accurate phase calibration in order to measure current and voltage waveforms at the terminals of two-port microwave devices. The calibration approach presented in this paper does not require any multi-harmonic coherent signal generator and golden standard, reported in earlier papers, thus allowing the system to be more reliable, generic and accurate. The results achieved using the reported calibration algorithm on a developed measurement setup shows good agreement with those obtained on a standard commercial scope. In the end, it has been shown that the developed algorithm and measurement setup can be adapted for carrying out waveform engineering which clearly identifies the application of this work in the characterization and measurement of microwave devices.
A new CPW-fed dual-band circularly-polarized (CP) annular slot antenna with two perturbation strips is proposed. The structure of the annular slot, along with two concentric annular-ring patches, can achieve dual-band input impedance matching. And circular polarization at the operation bands can be achieved by using the two perturbation strips placed on the backside of the antenna. To reduce the resonant frequencies, a third strip protruded from the ground plane is introduced. Both the simulated and measured results show that the impedance bandwidths determined by 10-dB return loss are about 29.1% for the lower band (1.92-2.61 GHz) and 12.1% for the upper band (3.21-3.65 GHz). And the AR bandwidths are about 7.5% and 11.0%, respectively.
This paper describes the investigation of broadband interaction and harmonic suppression. A special dispersion shape used in broadband traveling-wave tubes (TWT) is obtained. The theoretical and simulation studies of negative dispersion are presented. On the basis of these studies, a broadband TWT used in microwave power module (MPM) is designed. Compared with the old TWT with flat dispersion, the new one with negative dispersion decreases the second harmonic content about 10 dB and improves the fundamental efficiency about 5% at the low end of the band. The new one operates with the beam voltage of 3600 V and current of 250 mA. The modified TWT is fabricated and the simulation results meet the measurements very well.
This paper presents a design of circularly polarized dielectric resonator antenna (DRA) array. The dielectric resonators (DRs) were excited by rectangular aperture coupling slots feed with a linear microstrip. The slot positions were determined based on the characteristic of standing wave ratio over a short ended microstrip to deliver the maximum amount of coupling power to the DRs, in order to improve the array gain. Each DR element was rotated 45ᵒ with respect to the sides of the exciting slot to generate circular polarization pattern. The DRA array was modeled and simulated as a parallel RLC input impedance component using Agilent (ADS) software, since that will ensure the resonant frequency of the antenna as primary design step before simulating in (CST) software and doing the measurements. The results of the return loss, gain, radiation and pattern axial ratio are shown. The gain of the proposed array in X band was about 8.5 dBi, while the 3dB axial ratio bandwidth started from 8.14 to 8.24 GHz. The impedance bandwidths started from 8.14GHz to 8.26GHz. The proposed DRA exhibited an enhancement of the gain in comparison to a single pellet DRA. The size of the whole antenna structure is about 40 mm X 50 mm and can potentially be used in wireless systems.
An Ultra Wide Band (UWB) Low Noise Amplifier (LNA) for 802.15.4a UWB PHY (physical layer) is proposed. The amplifier is designed using IHP Microelectronis CMOS 0.25 μm technology for lower price. The LNA area, power, and performance was optimized using the Genetic Algorithm (GA). The optimization goals included inductance values, power consumption, and performance in the frequency domain using S-Parameters, then fine tuned in the time domain using the reference UWB pulses of the 802.15.4a standards. The LNA consumes around 10mW excluding the output buffer stage, has a gain of 11 to 15 dB, a 1 dB compression point of -9 dBm, and five inductors with a total value around 10 nH.
A dual wideband CPW-fed slotted Koch snowflake fractal monopole, which is suitable for WLAN/WiMAX applications, is presented. The proposed antenna has been analyzed and designed with Ansoft HFSSTM v.11. Then an experimental prototype is fabricated and measured. It is compact with a total size of 41.5 mm × 27 mm × 1 mm (L×W×T). Results of simulation and measurement indicate that the proposed fractal monopole with a U-shaped slot has dual impedance bandwidths 2.35-4.25 GHz and 4.8-5.95 GHz, which covers WLAN bands (2.4/5.2/5.8GHz) and the WiMAX bands (2.5/3.5/5.5 GHz) respectively. In addition, good radiation performances such as omnidirectional and doughnut-shaped directivity and goodish gain over the operating bands have been obtained.
This paper presents a new composite material, which is developed by mixing calcium alginate spheres with commercially available epoxies Stycas 2850 FT (s2850) and Stycast W19 (W19). The resulting composite material is examined in terms of transmission and reflection coefficients in microwave frequencies (26 to 40 GHz, 70 to 110 GHz and 300 to 320 GHz). The study reveals that the new material exhibits reflection coefficients much lower than some commercial CR absorbers from the Eccosorb group. The experimental results justify the use of the new composite material as absorber at microwave frequencies.
In this paper, a covariance matrix adaptation evolutionary strategy (CMA-ES) is employed for optimization design of non-uniform circular antenna arrays. To achieve minimum sidelobe levels with the constraint of a specific first null beamwidth, the CMA-ES is utilized to find out the optimal weights and geometry of the circular array. The three various circular ring arrays are solved via CMA-ES, and the results are presented for arrays of varying configurations. The design results obtained with CMA-ES are compared to the existing array designs in the literature and to those found by the other evolutionary algorithms. Comparison with the results of other algorithms reveals the superiority of the CMA-ES.
Wideband spectrum sensing is an essential functionality for cognitive radio networks. It enables cognitive radios to detect spectral holes over a wideband channel and to opportunistically use under-utilized frequency bands without causing harmful interference to primary networks. However, most of the work on wideband spectrum sensing presented in the literature employ the Nyquist sampling which requires very high sampling rates and acquisition costs. In this paper, a new wideband spectrum sensing algorithm based on compressed sensing theory is presented. The proposed method gives an effective sparse signal representation method for the wideband spectrum sensing problem. Thus, the presented method can effectively detect all spectral holes by finding the sparse coefficients. At the same time, the signal sampling rate and acquisition costs can be substantially reduced by using the compressive sampling technique. Simulation results testify the effectiveness of the proposed approach even in low signal-to-noise (SNR) cases.
In this paper, a synthesis method is presented for Chebyshev type II band-pass filters in the microwave frequency range. We investigate the cause of the second harmonic passband of coupled-serial-shunted lines bandpass filters. Filters are employed substrate suspension, wavy-edge coupling, ring resonators, defect ground structure (DGS), and a combination of the wavy-edge coupling and ring resonators may be used and were investigated to suppress the harmonic pass-band. With a combination of the wavy-edge coupled-lines and ring resonators, the harmonic pass-band of the parallel-coupled line filter is rejected more effectively. Several filters are fabricated and measured to demonstrate the design.
This work presents the results of the synthesis of a light-weight inexpensive reconfigurable planar array antenna. The antenna structure is based on four circular patches. The sources points and some discontinuities on the patches can be electronically reconfigured by means of radio-frequency (RF) switches in order to modify the radiation pattern. In particular, the main lobe could be steered towards a desired direction to obtain an optimal management of wireless resources. An experimental prototype has been realized and tested. Numerical and experimental results are reported and compared to assess the reconfigurable capabilities of the proposed antenna prototype.
This paper presents a novel planar antenna with a reconfigurable radiation pattern. The proposed layout consists of N ≥ 2 monospaced planar bowtie antennas selected one by one by means of a pair of PIN diodes. Experimental results referring to the case of N=2 and N=4 are reported and discussed demonstrating the feasibility and effectiveness of the proposed design approach.
In this paper, a novel approach to design compact multi-band loop antennas is proposed. This type of antennas is composed of coplanar waveguide (CPW)-based composite right/left-handed (CRLH) quarter-wave type resonators, and developed on a vialess single layer. Both size reduction and low frequency ratios have been achieved, profiting from the employment of quarter-wave resonators and the high nonlinearity in the left-handed region of CRLH transmission line (TL) dispersion diagram. A sample prototype operating at three negative modes (1.92/2.15/2.64 GHz) with an overall size of 29 × 21.3 × 1.0 mm3 was manufactured and measured. Measured results show good agreement with EM simulation, exhibiting good impedance matching as well as stably omni-directional radiation patterns at the three operating modes.
This paper focuses on the electromagnetic compatibility domain, coupling in microwave circuits and wideband (WB) impedance matching in time domain using a purely temporal method, such as the centered-points Finite Difference Time Domain (FDTD). The paper here presents a new approach of WB impedance matching in transient regime and coupling context, of active circuits such as multiple complex nonlinear components (represented here by metal semiconductor field-effect transistors (MESFETs)), using Nonuniform Multiconductor Transmission Lines (NMTL) with frequency dependent losses and FDTD as modeling method. The FDTD method has several positive aspects such as the ease to introduce nonlinear components in the algorithm, the ease to use NMTL and the gain in simulation time and memory space. Also the FDTD method allows the study of WB impedance matching in time domain without recourse to the frequency domain. Systematic comparisons of the results of this method with those obtained by PSpice are done to validate this study. These comparisons show a good agreement between the method presented here and PSpice. The technique presented in this paper shows higher efficiency and ease to implement when compared to PSpice in regard to the treatment of frequency dependent losses, or shapes of transmission lines.
A low profile CPW fed millimeter wave rectangular slot antenna operating with a wideband; centered at 94 GHz has been designed, fabricated and tested on a 10 μm silicon diaphragm. To improve the bandwidth of the conventional slot antenna a C-shaped tuning stub has been incorporated. Measurement results show that the antenna operates from 75 to 105 GHz with a reflection coefficient better than -10 dB. At its resonant frequency the fabricated slot antennas have a reflection co-efficient ranging from -25 dB to -35 dB. The bandwidth of the antenna with a tuning stub was found to be over 30% at -10 dB. By using the slot antenna with a C-shaped tuning stub the bandwidth has been shown to improve, which could be used for several Millimeter wave applications.
A planar folded dipole antenna with triple-band operation for WLAN and WiMAX applications is proposed. It comprises a pair of symmetrical branch arms, which occupy a compact size of 35(L)x4(W) mm2 to be easily embedded inside a portable device as an internal antenna. By properly designing the branch radiating strips, three operating bands covering 2.39-2.5 GHz, 3.3-3.94 GHz, and 5.06-6.06 GHz can be acquired with the antenna. Moreover, the antenna's resonance can be appropriately adjusted to optimize the radiation performance for actual application. A fabricated prototype of the proposed antenna is tested and analyzed. Experiments show that good omnidirectional coverage and stable gain variation to enhance communication quality for WLAN/WiMAX operations can be obtained with the antenna.