有振幅调制和位相畸变光束的非线性传输

从广义惠更斯-菲涅耳衍射积分和B积分定义出发,并利用统计光学方法,对有振幅调制和位相畸变光束的非线性传输特性作了详细研究.     

面向无人机小区覆盖的毫米波波束优化设计

为了提高无人机毫米波波束覆盖区域内的通信容量,改善覆盖区域内用户通信质量,本文结合均匀平面阵列天线,提出采用一种基于目标覆盖区域量化的波束优化设计方法。该方法首先将目标区域进行量化,根据理想波束增益得到理想混合预编码向量;其次,以实际预编码向量与理想预编码向量之间的均方误差最小化为目标获得最优波束,进一步利用改进的正交匹配跟踪算法去拟合产生适合实际系统的波束成形矢量。仿真表明该波束设计方法在收敛速度和收敛精度上均优于传统方法,并可以获得更好的波束形状和波束增益,从而提高无人机目标覆盖区域内用户的通信质量。      

有振幅调制和位相畸变光束通过光阑的变化

用广义惠更斯-菲涅耳衍射积分和统计光学方法对有振幅调制和位相畸变光束分别通过硬边和软边光阑的传输特性作了详细研究。数值计算结果表明近场和远场光强分布与截断参数、系统菲涅耳数、光束的振幅调制和位相畸变参数均有关。     

利用介质超材料控制太赫兹波的振幅和相位

设计了基于介质高阻硅的超材料用于对太赫兹波的透射振幅和相位进行控制。这里组成超材料的基本结构单元为亚波长柱状硅,相比于基于金属的超材料,其损耗小,效率也更高。太赫兹入射到不同尺寸和旋向的柱状硅时,所透射的太赫兹波的振幅和相位也不同。通过设计不同空间位置处的柱状硅尺寸和旋向,就可以实现任意的振幅和相位分布,从而对透射波波前进行完全的控制。实验中,利用这种硅质微结构设计了三种不同的奇异光栅,其衍射级次和数目可任意控制。这种基于介质超材料的方法,设计简单,加工方便,在制作太赫兹波段低损耗的功能器件方面有着广泛的应用前景。     

Array grating lobes due to periodic phase, amplitude, and time delay quantization

Simple approximate formulas and generalized curves to evaluate the grating lobe levels of various kinds of contiguous subarrays with uniform illumination within each subarray are presented. The cases considered include phase quantization due to discrete phase shifters, amplitude taper at subarray input ports and time delay at the subarray input ports. In addition, the work is generalized to include certain cases of quantized phase or time delay at the input ports in addition to amplitude taper at subarray input ports.     

Generation of multiple simultaneous beams by aperture phase control

Radiation patterns containing multiple beams may be generated by manipulating merely the phase on an aperture, leaving the amplitude distribution undisturbed. The relative phases between the various beams may be adjusted for a best approximation.     

Electronic and electromagnetic devices for millimeter-wave beam control arrays

Device alternatives for millimeter-wave beam control arrays are examined. For the control function, a wide range of semiconductor device as well as bulk material alternatives are considered. In addition, alternatives to the traditional metal strip are considered for the passive electromagnetic array element. This work should provide a broader perspective regarding the choices available for the optimized design of new beam control arrays.     

A 4-bit CMOS phase shifter for millimeter-wave phased arrays

A 4-bit active phase shifter for millimeter-wave phased arrays is presented in this brief. The proposed phase shifter has achieved a phase-shifting range of $360^{\circ }$ with a $22.5^{\circ }$ resolution over 40 to 50-GHz. Thanks to the careful dimension designs of digitally controlled gain stage in the programmable weighted combiner, the active phase shifter achieves root-mean-square phase and gain errors of $5^{\circ }$ and 1.25-dB at 45-GHz, respectively. The measurement results also show that the input and output return losses are better than 7-dB from 40 to 50-GHz. The whole chip dissipates only 10.7-mA from 1.2-V supply excluding output driven buffer.     

Broadband phase modulators in integrated fin-line technique for millimeter-wave applications

Three structures of broadband reflection type phase modulators in unilateral fin-line are presented. The circuits have been analysed assuming ideal transmission line equivalent circuits for the fin-line sections, while the switching element, a pin-diode, is represented by a typical equivalent circuit at Ka-band. The insertion loss in all three cases is better than 1.5 dB and the phase error for a 180 degrees phase shift is less than 4 degrees over a 12% bandwidth, while a 16% bandwidth is achieved for a 90 degrees modulator at a phase error of 2 degrees.     

The design of millimeter-wave control components

The design of broadband high-performance control components covering the 18-40-GHz frequency range utilizing microstrip technology is described. Design considerations and experimental results are presented for high-speed single-pole, single-throw and single-pole, double-throw switches with 80- and 60-dB isolation, respectively. Design equations and experimental results are presented for a 3-dB quadrature microstrip reentrant coupler and for a nonreflective voltage-controlled attenuator with a dynamic range of 50 dB     

On instantaneous amplitude and phase of signals

In many questions of signal processing, it is important to use the concepts of instantaneous amplitude or phase of signals. This is especially the case in communication systems with amplitude or frequency modulation. These concepts are often introduced empirically. However, it is well known that the correct approach for this purpose is to use the concept of analytic signal. Starting from this point, we show some examples of contradictions appearing when using other definitions of instantaneous amplitude or frequency that are commonly admitted. This introduces the problem of characterizing pure amplitude-modulated or pure phase-modulated signals. It is especially shown that whereas amplitude modulated signals can be characterized by spectral considerations, this is no longer the case for phase-modulated signals. Furthermore, signals with constant amplitude have very specific properties, which are analyzed in detail. Some consequences and extensions to random signals are finally discussed     

Predicted performance of magnetized semiconductor phase shifters for millimeter-wave microstrip array antennas

The tunable phase shift of a planar magnetized semiconductor phase shifter is presented, suitable for an integrated environment due to its miniature size, low-biasing requirements, and lower material related problems at millimeter-wave frequencies. A linear microstrip phased array antenna with an integrated semiconductor phase shifter is designed and the calculated beam steering properties are tabulated. The design process is verified by simulating similar ferrite-based linear phased array antennas.     

Ultrawide-band fiber-optic control of a millimeter-wave transmitbeamformer

An ultrawide-band fiber-optic true time-delay millimeter-wave array transmitter is fully characterized and demonstrated in this paper. The beamformer is based on dispersive-prism optical-delay lines and exhibits squint-free ±60° steering in azimuth across the entire Ka-band (26.5-40 GHz). This is believed to be the first fully functioning demonstration of a photonically controlled wide-band millimeter-wave transmitter system     

振幅调制和位相扰动条件下三倍频器参数的优化

采用Ⅱ/Ⅱ类偏振失配的KDP晶体倍频方案,讨论了振幅调制和位相扰动对倍频系统转换效率和动态范围的影响,提出了在高功率条件下提高倍频系统转换效率和增大动态范围的方法。在振幅调制和位相扰动条件下对倍频器参数进行了优化设计。     

Iterative receiver employing phase noise compensation and channel estimation for millimeter-wave OFDM systems

This paper proposes an iterative OFDM millimeterwave receiver employing low-complexity decision-directed phase noise compensation (DD-PNC) to alleviate degradation due to the phase noise. High bit-rate OFDM transceivers based on the single-chip Si RF-CMOS IC technology in the 60-GHz millimeter-wave band have been extensively studied for wireless personal area network (WPAN) systems, and the relatively large phase noise in the phase locked loop (PLL) synthesizer severely degrades transmission performance. The proposed OFDM receiver iterates DD-PNC and decision-directed channel estimation (DDCE) by exploiting the output of the channel decoder. DDPNC estimates the phase noise each sampling time by using the decoder output, and then it removes the estimate from a time-domain received signal. In addition, DDCE estimates a channel impulse response by using the compensated received signal. Computer simulations demonstrate that in the 64QAM modulation with the coding rate of 3/4, the proposed receiver with DD-PNC and DDCE can perfectly remove the phase noise of -85 dBc/Hz at 1 MHz offset, and that it can alleviate the degradation of the channel estimation due to the phase noise.     

Spectrum analysis of phase amplitude modulation

The theoretical possibility of producing a CSSB (compatible single-sideband) wave by phase amplitude modulation with a predistorter before the phase modulator is discussed. The rule for achieving good one-sideband suppression is examined. It is argued that adequate lower-sideband suppression of a CSSB wave can be achieved by a phase-amplitude modulation system with a predistorter     

Current amplitude control circuits suitable for current-modeoscillators

A novel current amplitude control circuit suitable for current-mode oscillators is proposed. The circuit is a modified version of the well-known Gilbert gain cell. The technique obtains independent control of oscillation amplitude and small-signal current gain. As an example, the amplitude control circuit is applied to a current-mode oscillator. Simulations were carried out using HSPICE with 0.8 μm Nortel BiCMOS technology and Motorola RF transistors. Simulated results demonstrate that the nonlinear current gain control circuit behaves in a well defined manner. Low distortion and high frequency oscillations are easily obtained when the circuit is applied to a current-mode oscillator     

Coplanar Schottky variable phase shifter constructed on GaAs substrate for millimeter-wave application

A Schottky contact variable phase shifter constructed on either uniformly or periodically doped GaAs substrate is discussed in details. The device can operate at millimeter-wave frequencies with reasonably low attenuation.     

Estimation of amplitude and phase parameters of multicomponentsignals

This paper considers the problem of estimating signals consisting of one or more components of the form a(t)e/sup jφ(t/), where the amplitude and phase functions are represented by a linear parametric model. The Cramer-Rao bound (CRB) on the accuracy of estimating the phase and amplitude parameters is derived. By analyzing the CRB for the single-component case, if is shown that the estimation of the amplitude and the phase are decoupled. Numerical evaluation of the CRB provides further insight into the dependence of estimation accuracy on signal-to-noise ratio (SNR) and the frequency separation of the signal components. A maximum likelihood algorithm for estimating the phase and amplitude parameters is also presented. Its performance is illustrated by Monte-Carlo simulations, and its statistical efficiency is verified     

Optical control of millimeter-wave propagation in dielectric waveguides

We have demonstrated a new method for controlling millimeter-wave propagation in semiconductor waveguides-optical control. Phase shifts as high as 300°/cm at 94 GHz were observed accompanied by less than 1 dB insertion loss. A theoretical model has been developed to account in detail for the observed behavior. Extension of this technique to ultra-fast switching and gating of millimeter-wave signals is also described. Millimeter-wave pulsewidths as short as 1 ns and variable to tens of nanoseconds can readily be obtained.