舰载短波鞭天线天波地波干涉计算

为了计算舰载鞭天线近距离通信时地波和天波的干涉,在3~15 MHz频率范围内利用Rotheram地波传播理论计算了鞭天线的地波场强分布,利用国际电信联盟ITU-R P.533建议计算了鞭天线的天波场强分布。通过分析信噪比大于0 dB和场强相差±10 dB的区域后发现,舰载鞭天线的地波和天波场强在一定距离和时段内会互相干涉。结果表明:在通信双方位置一定的情况下,通信时机、通信频率和发射功率等对舰载鞭天线的地波和天波场强干涉区域的影响较大。     

High-speed modulation of an electrooptic directional coupler

A LiNbO3:Ti directional coupler driven by an RF signal has been tested at 1.06 μm over a large modulation bandwidth. An analytical model has been developed leading to simple usable expressions to describe the theoretical dependence of the frequency spectrum of sinusoidally modulated light. The frequency response has been measured with a scanning Fabry-Perot and also with a high-speed photodiode. Both methods provided results which are in good agreement. The 9 mm long switch exhibited a 2.5 GHz bandwidth; a 16 dB extinction ratio has been achieved with a driving power of approximately 50μW/MHz. The confirmation of practical modulation response expressions shows the advantage of the optical spectrum observation, which is a very simple measurement method without any bandwidth limitation. In addition, this method has the advantage of remaining quite accurate even for large modulation signals.     

Trivalent-iron-doped andalusite as crystal for microwave waves

Paramagnetic ions Fe³⁺, substituted as an impurity in andalusite (Al2SiO5) host crystals, have been experimentally investigated. The spin-lattice relaxation and cross-relaxation times and inversion ratio in this spin system were observed. Dielectric properties of the host crystals were determined. General maser properties of trivalent-iron-doped andalusite crystal are discussed. Two types of the andalusite cavity masers are described. TheX-band three-level maser operates at a temperature of 2.1°K and a magnetic field of 1400 gauss. Electronic gains of 25 dB and instantaneous bandwidth of 3.5 pm 0.5 MHz, at the frequency of 9.45 GHz, were obtained. TheF-band push-pull maser operates at a temperature of 2.1°K and a magnetic field of 2800 gauss. Electronic gains of 30 dB and instantaneous bandwidth of 5.5 ± 0.5 MHZ, at the frequency of 100.4 GHz, were obtained.     

Miniature superconductive coaxial transmission lines

This is a review paper concisely tracing the development of miniature superconductive coaxial transmission lines from the original invention as a vertical channel signal delay line for fractional nanosecond pulse oscillography to present-day work towards highly compact, broad-band, and low-loss telecommunication cables. The present state of development yields a 1.6-mm coaxial line operating at 4.2K and having Pb conductors, polyethylene dielectric, Z0= 50 ± 0.3 Ω and a 1-GHz attenuation of the order of 1 dB/km. The attenuation up to 1 GHz is mainly due to dielectric losses.     

Precise time and frequency dissemination via the Loran-C system

The Loran-C Navigation System is described in terms of its characteristics as a precise time and frequency dissemination system. The technique employed in timing a Loran-C chain is described, and user techniques are addressed including economic considerations. The accuracy available for both ground-wave and sky-wave transmission modes is shown to be a function of the low-frequency propagation factors and equipment delays involved. Phase and amplitude perturbations due to irregular terrain effects are shown to produce time difference discrepancies in inland service areas. Using broad assumptions, both ground-wave and sky-wave coverages are estimated. Experience shows that Loran-C provides an excellent medium for the dissemination of precise time and frequency on a continuous basis in both the ground-wave and sky-wave modes. The stability of the ground wave provides a submicrosecond precision capability, but the accuracy of the system is limited by propagation effects to about ± 1 µs. Loran-C sky-wave synchronization appears to be capable of ± 1 µs precision for one-hop daytime transmissions and an estimated ± 8 µs for one-hop nighttime transmissions. As distance is increased and more sky-wave hops are involved, nighttime synchronization precision is degraded to about ± 20 µs. Accuracy of sky-wave synchronization is limited to about ± 50 µs for both daytime and nighttime.     

宽带低杂散LFM信号的产生方法与系统设计

针对宽带雷达线性调频信号产生,采用FPGA电路和宽带DAC电路直接产生50 MHz~550 MHz 的线性调频中频信号。将中频信号上变频到2 GHz~2. 5 GHz 的射频频段,再经过2 倍频获得4 GHz~5 GHz的宽频带线性调频信号。为进一步提高射频输出信号的幅度/相位特性,采用幅/相预失真校准方法,并精心设计信号产生系统的中频电路和射频电路,进行了实验研究与分析。对实际系统的测试结果表明,系统产生LFM信号的带外杂散优于-55 dB,带内起伏小于依2 dB,且系统稳定、可靠。     

An experimental evaluation of the performance of two-branch spaceand polarization diversity schemes at 1800 MHz

Determines the mean signal level and envelope cross-correlation of 1800 MHz base station signals received in two-branch spatial and polarization diversity schemes. Measurements have been conducted with the experimental base site located in (i) two urban sites, (ii) a residential area, (iii) a rural area, and (iv) near a motorway. In each location, the effect of the random orientation of a typical mobile radio telephone handset has been studied by examining the characteristics of signals received from a mobile collinear antenna inclined at angles of 0°, 30°, 45°, 60°, and 90° to the vertical. Furthermore, the diversity gain at 90% signal reliability has been evaluated for each diversity scheme by simulating selection, equal-gain and maximal-ratio combining techniques using the recorded signals as inputs. Results have shown that 20λ separation in the horizontal plane or 15λ in the vertical plane is sufficient to obtain a cross-correlation of less than 0.7 for most of the time at 1800 MHz. Similar cross-correlation results were obtained for polarization diversity. When the antenna is inclined at 45°, a 6 dB degradation in signal level was recorded for space diversity schemes. However, the diversify gain is unaffected by tilt and remains unchanged at 5-6 dB for horizontal and 3.5-4.5 dB for vertical separation. For polarization diversity, only a little degradation is experienced because most of the energy lost on the vertical branch is recovered on the horizontal branch. The diversity gain is between 1-2 dB at 0° tilt and increases to 3-5.2 dB at 45°     

一种小型化C波段线性调频T/R组件

采用模拟调频方案,设计了一种小型化线性调频微波收发(T/R)组件。该微波T/R组件在实现所需的调频中心频率和带宽的同时,保证了调频稳定度。T/R组件的调频中心频率为(4 300±15) MHz,调制带宽为(150±1) MHz,调制线性度小于1.2,发射功率大于20 dBm,接收噪声系数小于3 dB,收发隔离度大于80 dB。此T/R 组件的尺寸仅为 50 mm×40 mm×12.3 mm,在同类型产品中具有较明显优势。     

移动数字电视接收机中宽带RF RSSI的设计

基于UMC 0.18 μm RF CMOS工艺,设计并实现了一个应用于移动数字电视接收机射频前端的接收信号强度指示仪(RF RSSI).提出了一种全新的功率检测电路,相对于传统的非平衡源级耦合对整流器,具有设计简单、功耗低以及良好的宽带功率指示功能;电路中前置放大器采用恒定跨导(G<,m>)偏置技术,输出放大器为三运放...     

An automated electromagnetic-field strength measurement system with a magnetic-field probe

An automated electromagnetic-field strength measurement system and its applications are described which are for the purpose of mapping the electromagnetic-field strength distribution inside and outside vehicles exposed to electromagnetic field. The system is comprised of three subsystems: electromagnetic-field generation unit, data transmission stage using a magnetic-field probe and a fiber-optic link, and data control/processing stage consisting of a graphic computer and peripherals. The system is capable of measuring field strength levels between 40 and 85 dBµA/m with errors within ± 1 dB in a frequency range of 20-200 MHz. The time required for making measurements at a single measurement point at intervals of 2 MHz from 20 to 200 MHz is about three min. Magnetic-field strength measurements at every interior position of a vehicle exposed to electromagnetic fields inside an anechoic chamber were made using this system. The field strength of the vehicle interior was found to vary with the polarization of an electromagnetic wave, the direction of irradiation, and the body shape of the vehicle.     

Wideband MOSFET differential V/I converter

This article presents a proposed modified flipped voltage follower for applications in a wideband MOSFET differential V/I converter using IBM 0.13 μm technology. Operating with ±2.5 V supply rails, the transconductance is nominally 3.3 mS for an input differential signal voltage range of 0.5 V, and the ?3 dB bandwidth exceeds 4 GHz. The THD measured at 1 MHz for a differential input signal of 500 mVp-p is less than –82 dB, and is still below –50 dB at 1 GHz.     

基于LTCC的超宽带巴伦滤波器小型化设计

该文设计了一种基于低温共烧陶瓷(LTCC)技术的小型化超宽带巴伦(Balun)滤波器。该巴伦滤波器由一个五阶带通滤波器和基于Marchand巴伦改进型巴伦级联组成,带通滤波器采用耦合谐振式的设计方法,设计成宽带高抑制巴伦滤波器,在二阶、三阶和四阶谐振之间创新采用电感级联的拓扑结构,使相对带宽在48%以上。巴伦输入与输出之间的耦合采用一种并联堆叠式耦合螺旋传输线,增强了传输线之间的耦合,并拓宽了巴伦的带宽。结果表明,该巴伦滤波器通带为1.71～2.76 GHz,插损均小于2.3 dB;在50～669 MHz,抑制大于35 dB;在669～1 245 MHz,抑制大于17 dB;在3 205～3 400 MHz,抑制大于27 dB;在3 400～6 000 MHz,抑制均大于30 dB。两个输出端口信号的相位差和幅度差分别为180°±15°(1 710～2 340 MHz)、180°±10°(2 500～2 760 MHz)和±1.0 dB,具有较高的通用性和良好的应用市场。     

Broadband 60-W HF linear amplifier

The design, construction and performance of a solid-state untuned 2-30 MHz amplifier is described. Operation is from 28 V dc. Overall CW efficiency is greater than 47 percent at 60-w unfiltered output. Amplifier efficiency for two-tone 60-W PEP output is greater than 31 percent. two-tone linearity over the frequency range is -30 dB or better at output powers from 5-60 W. Broadband transmission-line transformers wound on ferrite toroids are used throughout for impedance matching. Hybrids of similar construction are used for output-power adding.     

A power-efficient 10-bit 40-MS/s sub-sampling pipelined CMOS analog-to-digital converter

This paper presents a 10-bit 40-MS/s pipelined analog-to-digital converter (ADC) in a 0.13-μm CMOS process for subsampling applications. A simplified opamp-sharing scheme between two successive pipelined stages is proposed to reduce the power consumption. For subsampling, a cost-effective fast input-tracking switch with high linearity is introduced to sample the input signal up to 75 MHz. A two-stage amplifier with hybrid frequency compensation is developed to achieve both high bandwidth and large swing with low power dissipation. The measured result shows that the ADC achieves over 77 dB spurious free dynamic range (SFDR) and 57.3 dB signal-to-noise-plus-distortion ratio (SNDR) within the first Nyquist zone and maintains over 70 dB SFDR and 55.3 dB SNDR for input signal up to 75 MHz. The peak differential nonlinearity (DNL) and integral nonlinearity (INL) are ±0.2 LSB and ±0.3 LSB, respectively. The ADC consumes 15.6 mW at the sampling rate of 40 MHz from a 1.2-V supply voltage, and achieves a figure-of-merit (FOM) value of 0.22 pJ per conversion step.     

Application of laserQswitching for infrared spectroscopy

PassiveQswitching of IR lasers (N2O as well as CO2) has been applied for the detection of coincidences within a few 100 MHz between laser lines (νL) and molecular transitions (νM). Polar (¹²CH3F,¹³CH3F, C2H5OH, and C6H5CH3) as well as nonpolar molecules (SiH4, GeH4, CCl4, C2H4, C3H4, and C6H6) have been studied. The phenomenon depends strongly on the frequency mismatchDeltanu = nu_{M} - nu_{L}. 81combinations between laser lines and molecular absorption lines were found to produce theQ-switch effect.     

Interference-reducing antennas for shortwave broadcast listeners

Principles useful in the design of directional antennas capable of reducing interference in shortwave-broadcast reception are identified. Examples are given of designs which go beyond the time-honored vertical loop. It has been found that significantly improved rejection of both ground- and sky-wave interference can be obtained with minimum modification to the associated receiver, even in typical indoor environments. Measurements suggest that single-source sky-wave signal reductions of 20 dB can be achieved on average. This is sufficient in many instances to give satisfactory separation of two signals on the same frequency of comparable strength and having azimuth differences of 90° or greater. It seems likely that widespread use of these antennas would significantly reduce the severity of co-channel interference in shortwave broadcasting     

4-GHz 15-W power GaAs MESFET

High-field behavior of GaAs MESFET's such as drain-source breakdown characteristics and visible light emission and a model explaining these phenomena are described. An FET structure with a high drain-source breakdown voltage in excess of 26 V has been developed following an analysis of the high-field behavior of the device. Typical characteristics of the fabricated devices at 4 GHz are as follows: Pout= 9.6 W Ga= 5 dB ηadd= 33.6 percent at 18 V from single chip (WG= 13 mm) Pout= 15 W Ga= 5 dB ηadd= 28.3 percent at 22 V from two chip (WG= 26 mm) where Pout, Ga, ηadd, and WGindicate the output power, associated power gain, power added efficiency, and total gate width of the FET's, respectively.     

8GHz双栅FET上变频器

本文阐述了双栅FET的变频原理。通过对南京固体器件研究所WC52型双栅FET直流特性及微波“s”参数的分析,叙述了直流工作点的选择和微波匹配电路的设计。 研制了上变频器,并已用于8GHz无人值守微波中继机中。连同前置匹配放大器获得如下性能:输出频率8059.02±20MHz,输入频率140±20MHz,本振频率为8199.02MHz,增益22dB,1dB增益压缩点输出电平+4dBm,1dB压缩点处三阶交调产物为-23dBc。     

AN ANTI-ALIASING FILTER FOR ∑△ ADC

An anti-aliasing filter for ΣΔ ADCs using a combination of active RC and analog FIR filters is presented in this letter. The first order active RC filter is set at 100kHz to minimize the die size and variations of linear phase and gain in 0–4kHz passband. The 2-tap FIR filter provides more than −53dB attenuation at 2MHz ±4kHz frequency range. The proposed filter achieved more than −76dB attenuation at sampling frequency with ±0.01° phase linearity and ±0.02dB gain variation within 0–4kHz bandwidth. The active die area of the fully differential filter is 0.17mm² in 0.5μm CMOS technology. The experimental and simulation results have been obtained and the feasibility of the proposed method is shown. Supported by Foundation for University Key Teacher by the Ministry of Education of China