Radio lighting based on ultrawideband dynamic chaos generators

The problem concerned with lighting of objects and surfaces by means of artificial incoherent microwave sources is considered with the aim of their subsequent observation with the help of radiometric equipment. Transmitters based on dynamic chaos generators are used as wideband incoherent microwave emission devices. The experimental sample of the given device, namely, radio light lamp based on the chaos microgenerator, and its characteristics are described.     

Generation and radiation of high-power ultrawideband nanosecond pulses

The results of investigation of the generation and radiation of high-power ultrawideband electromagnetic pulses are presented. The possibility of obtaining wave beams of radiation with orthogonal polarizations of the electric field is shown. The radiating system is a 16-element antenna array that can be separated into two subarrays operating in orthogonal polarizations and excited by pulses separated in time. Two design versions of orthogonal subarrays are studied.     

Effect of high-hygroscopicity salts on the dielectric properties of saline soils in the decimeter wave band

The effect of salinity and volume wetness on the dielectric properties of saline sandy soils containing high-hygroscopicity salt CaCl₂ are investigated experimentally. A new type of behavior of the dielectric properties of saline soils in the bound-water region is determined.     

Generation and radiation of high-power ultrawideband pulses with controlled spectrum

A pulsed source of the ultrawideband radiation based on a nonlinear line and a single combined antenna is proposed. The frequency that corresponds to the maximum radiation spectrum can be tuned in the interval 0.5–1.3 GHz. The effective radiation potential of the source is 95–310 kV.     

Synthesis of ultrawideband differential phase shifters based on coupled transmission lines

Stepped and multielement differential phase shifters based on coupled transmission lines whose ends are connected by a connecting section are synthesized. It is found that a multielement structure with conventional C sections containing a zero-length connecting section should be used in the design of wideband phase shifters with a specified rated phase shift of φ₀ ≥ 180°, whereas stepped structures with a connecting section whose length is half the midband operating wavelength should be used in the design of wideband phase shifters with φ₀ > 180°.     

Hexagonal boundary Sierpinski carpet fractal shaped compact ultrawideband antenna with band rejection functionality

In this paper a second iteration Sierpinski carpet fractal shape UWB antenna with hexagonal boundary is presented. The antenna covers the frequency band from 3 GHz to 12 GHz (VSWR ≤ 2). The proposed antenna has the capability to reject 5.15–5.825 GHz band assigned for IEEE802.11a and HIPERLAN/2 which is achieved by embedding a ‘Y’ shaped slot in the radiator that extends to the central conductor of the CPW feed as well. A fabricated prototype is developed where the simulation and experimental results are in good agreement. Measured peak antenna gain varies from 1.25 dBi to 6 dBi within the band. The proposed antenna has a compact size of 33 mm × 32 mm that includes the substrate around the radiating element. Time domain characteristic reveal that the antenna is non-dispersive with a variation of measured group delay within 0.5 ns over the entire band.     

Frame-frequency estimation in ultrawideband systems

This paper investigates the estimation of the frame frequency in ultrawideband (UWB) communication systems. An estimation method is proposed that exploits the transmission of a periodic pulse sequence at the frame frequency. The samples of the received waveform are used to compute a cost function that depends on a trial value of the incoming pulse frequency. The location of the maximum provides an estimate of the transmitted frequency. The performance of the estimator is assessed theoretically and is compared to the Cramer-Rao lower bound. It is shown that in certain conditions the estimator achieves the bound at high SNR values. Simulations validate the theory and show the degradations in the estimation performance caused by multiple-access interference. They also give an idea of the estimation accuracy needed in a correlation receiver.     

混沌信号的相空间重构和预测方法研究

基于复杂非线性系统的相空间重构理论和神经网络本质为非线性映射关系的特点,提出利用混沌时间序列重构相空间和BP神经网络构建其预测模型的方法。利用该方法对典型的Lorenz混沌时间序列进行了空间重构,研究了预测模型的预测效果,结果表明单步预测效果理想,多步预测在50步以内也能取得较小的预测误差,证明了混沌信号不同于随机噪声,具有短期可预测、长期不可预测的特征。该方法为具有混沌特性的时间序列如心电信号、电力负荷等预测模型的建立提供了理论基础。     

Simulation and experimental study of chaos generation in microwave band using Colpitts circuit

Chaotic Colpitts circuits with fundamental frequency f^＊ beyond 1GHz are studied by both circuit simulation and experiment using Philips＇ broadband transistor with threshold frequency of 25GHz. For the basic configuration of Colpitts circuit with f^＊ of about 1,6GHz, broadband continuous power spectra could be obtained from both circuit simulations and experiments. The harmonics of the observed signal from Agilent PSA/ESA spectrum analyzer are as noticeable as far as 12GHz. A modified Colpitts circuit structure employing the parasitic inductance of BJT （Bipolar Junction Transistor） is also proposed and investigated. By circuit simulation, chaotic attractor and broadband continuous power spectra could be obtained from the modified Colpitts circuit with f^＊ of about 3.5GHz. Because the parasitic effects of the prototype board, the experiment result of the modified Colpitts circuit does not agree well with the simulation result. The gap between the simulation and experimental result could be bridged by replacing the lumped circuit elements with distributed ones.     

自泵浦相位共轭中的温度与混沌态

光折变晶体ＢａＴｉＯ３中实验测量了自泵浦相位共轭输出与温度的关系，发现不发温度超过８２℃后，自泵浦相位共轭输出出现混沌。与已有理论模型的计算机模拟解非常接近，说明在光折变晶体的ＳＰＰＣ中，非随机性混沌行为是温度的函数。     

New structure of ultrawideband fixed phase shifters based on stepped coupled transmission lines with stubs

Problems of the synthesis of ultrawideband fixed phase shifters with a new structure of the electric circuit of the phase-shifting channel formed by means of connection of two identical elements consisting of weakly coupled stepped transmission lines with stubs have been solved. The advantage of the proposed structure over the available structures is shown.     

Analysis of the characteristics of microstrip antennas in the decimeter wave range

Graphic dependences allowing one to promptly estimate the basic parameters of microstrip antennas (MSAs) are obtained for two frequency zones of decimeter wavelength range with central frequencies of 1600 MHz and 406 MHz, in which the equipment of satellite positioning systems (GPS, GLONASS, GALILEO, BEIDOU) and the COSPAS-SARSAT emergency radio beacon equipment operate. The influence of cuts in the MSA radiator that form a slow-wave structure (SWS) on the resonance frequency and frequency bandwidth of the antenna are studied. A technique of designing an MSA with circularly polarized radiated waves and this SWS is proposed, and the double impedance frequency band expansion is reached. The obtained bandwidth data are compared with theoretical limit values calculated from specified relation-ships that take into account the dissipative loss in the radiator. The MSA radiation efficiency is estimated.     

Estimation of ultrawideband quasi-radio signal duration

Quasi-likelihood and maximum likelihood algorithms of duration estimation for ultra-wideband quasi-radio signal of arbitrary shape with unknown amplitude and initial phase, influenced by additive Gaussian white noise, are synthesized. It was considered that conditions of relatively narrow band of received signal are not satisfied and its duration can constitute only several periods or a fraction of period of harmonic oscillation. It is shown that the structure of the algorithm for duration estimation of ultra-wideband quasi-radio signal is significantly different from the structure of duration estimation algorithm for narrowband radio signal. Relative bias and variance are determined as the statistical characteristics of synthesized duration estimates. The influence of unknown amplitude and initial phase on the accuracy of duration estimation is investigated. Quantitative limits for relation of signal bandwidth to its center frequency are formulated, such that the classical solution of the problem of duration estimation for narrowband radio signal possesses the required accuracy.     

Characteristics of estimating the amplitude of ultrawideband quasi-radio signal

Thesynthesis and analysis of the maximum likelihood algorithm for estimating the amplitude of ultrawideband quasi-radio signal with unknown amplitude and phase have been performed. The duration of the specified signal can amount to several periods or a fraction of the period of harmonic oscillation. The characteristics of the classical maximum likelihood estimate of the amplitude of a narrow-band radio signal were found while receiving an ultrawideband quasi-radio signal. The conditions of applicability of the model of narrow-band radio signal were defined for solving the problem of amplitude estimation with the specified accuracy.     

X波段低相噪VCO设计

从HJFET的物理模型出发，提出了反沟道HJFET的电路模型，分析其等效电路，并在此基础上设计并制作了一个反沟道振荡器。     

Digital audio broadcasting in the FM band based on continuous phase modulation

A method for broadcasting digital audio signals simultaneously with existing analog frequency modulation radio (88-108 MHz) in adjacent channels is presented. The digital transmission is based on continuous phase modulation (CPM) and a proper reduced-state sequence estimator. With the proposed method, the power level and the symbol rate of the transmitter signal is determined in a manner that the interference the CPM signal poses for the analog FM signal in adjacent channels remains below a level according to the radio frequency emission mask defined by international rules. Due to the multipath propagation of the transmitted signal, the transmission behavior of the radio channel is determined by high dispersion up to 85 /spl mu/s. With the selected bit rate, the receiver has to cope with a channel memory of up to 17 bits. Since Viterbi detection is not feasible due to the number of channel states, detection is performed by a reduced-state sequence estimator that is able to eliminate the complete channel interference by decision feedback. Simulation results show that the detector almost achieves the detection quality of the optimum receiver. CPM achieves data rates of up to 200 kb/s inside a 200 kHz FM channel, which is sufficient for transmission of digital compressed audio signals at compact disc quality. The encouraging results of field tests will be published in another paper.     

跳时超宽带无线电的性能分析

超宽带脉冲无线电是无线通信领域的一种全新技术,有着广阔的应用前景.它是一种基带无载波短脉冲,不同于使用正弦载波的传统通信系统.本文用满足FCC频谱规划的脉冲--高斯脉冲的五阶导数推导了TH-BPSK方式下的跳时超宽带扩频系统的误码与多址性能,并研究了多径对其性能的影响,比较了TH-BPSK 与TH-PPM系统性能,分析结果表明TH-BPSK的性能(未考虑多径)明显优于TH-PPM,但是TH-PPM抗多径性能优于TH-BPSK.     

相位图法研究光子晶体的禁带

给出了一种判断一维光子晶体禁带位置的相位图,利用扩展相位图可方便地描述光子晶体的禁带位置和禁带特征.研究发现,当光子晶体为1/4波片层堆时,光子晶体的禁带最宽;若要进一步展宽禁带,需提高构成周期单元的两种介质的折射率比.对于一般的光子晶体,若周期单元中两种介质的光学厚度不等,则其禁带中心将偏离中心频率的整数倍.此外还研究了禁带中心区的透射率,给出了中心频率附近透射率的一级近似解析解,并由此定性讨论了Fabry-Perot腔的谱线宽度和品质因子.     

Structure of arrays of ultrawideband combined antennas

The results of experimental investigations and calculations of the energy characteristics of four-element arrays of combined antennas excited by a single generator of bipolar voltage pulses with a duration of 1 ns through a power divider are presented. Based on the proposed criteria, the optimum structure of arrays is determined.     

Optimization of a combined high-power ultrawideband antenna

The results of optimization of the geometry of a combined ultrawideband antenna excited by a 1-ns bipolar pulse are presented. Numerical and physical experiments have been performed to optimize the increase in the electric-field strength in the direction of the antenna main beam. It has been shown that the peak field strength can be increased by 6%.