60GHz室内天线位置优化与天线选择策略

采用多天线技术的60 GHz无线通信被认为是未来室内场景下高数据率宽带无线接入一种有前途的解决方案。参考802.11ad工作小组采用的60 GHz信道模型,根据60 GHz路径损耗公式提出的分布式天线系统间距的优化方案可以保证房间内功率覆盖的均匀性。在此基础上,进一步分析60 GHz多天线系统在不同链路条件下的信道条件数关系,提出一种基于信道条件数的天线选择策略。该策略利用信道条件数判断信道性能,既保证了通信质量,又适时降低系统总功率,切换简单、易于操作,适用于60 GHz室内无线通信。     

Indoor channel characteristics based on wideband MIMO measurements at 5.25 GHz

Extensive indoor channel measurements were conducted in Beijing with wideband multiple-input multiple-output （MIMO） sounder at 5.25 GHz. Both line-of-sight （LOS） and non-line-of-sight （NLOS） propagation were measured in the indoor office and hotspot scenarios. On the basis of measured data, statistical channel characteristics are presented in this article, including the empirical path loss （PL） models, three excess delay parameters, circular azimuth spread （CAS）, and circular elevation spread （CES）. Comparative analysis of different propagation mechanisms in two scenarios is conducted. These values are significant for indoor coverage and technical research of MIMO and orthogonal frequency division multiplexing （OFDM） for the international mobile telecommunications-advanced （IMT-Advanced） system.     

Filter-based NRD-guide duplexer with low loss and high isolation at 60 GHz

A filter-based duplexer has been developed for a wireless broadband asymmetric digital subscriber line by using NRD guide technology. The isolation between the transmitter port and the receiver port is more than 45 dB, and the insertion loss is less than 3 dB in the 60 GHz band.     

2.5GHz光孤子传输

利用半导体光孤子源和掺铒光纤放大器成功地实现了２．５ＧＨｚ光孤子２１ｋｍ传输，并利用简化的半导体光孤子传输系统理论模型对实验系统进行了数值模拟计算，计算结果与实验结果基本一致。     

Indoor channel measurements and characterization at 60 GHz for wireless local area network applications

This work presents propagation measurement results at 60 GHz in order to determine the characteristics of indoor radio channels between fixed terminals. Path loss measurements are reported for line-of-sight (LoS) and non-line-of-sight (NLoS) cases, fading statistics in a physically stationary environment are extracted and a detailed investigation of the people movement effect on the temporal fading envelope is performed. Models that presented to predict path loss provide excellent fitting with errors of 1.13 and 3.84 dB for LoS and NLoS topographies, respectively. The dynamic range of fading in a quiescent environment is 8.8 dB and increased to 35 dB when a person moves between the fixed terminals with the channel becoming extremely nonstationary. Temporal variations induced by the moving people depend on the speed, the number of individuals the body sizes and the environment. Slow fading is observed as well as a quasi-wide-sense stationary (QWSS) behavior of the fading, but up to 50 ms of time.     

Propagation characteristics for wideband outdoor mobilecommunications at 5.3 GHz

In this paper, empirical channel models and parameters are derived from the wideband measured data at 5.3 GHz in outdoor mobile communications. The path loss exponents and intercepts are obtained by using the least square method. The mean excess delay and mean root-mean-square (rms) delay spread are within 29-102 ns and 22-88 ns, respectively. The correlation distances and bandwidths are within 1-11 λ and 1.2-11.5 MHz, respectively, when the envelope correlation coefficients equal 0.7 in line-of-sight cases. These correlation values depend strongly on the base station antenna heights. The window length for averaging out the fast fading components is about 1-2 m for microcells and picocells. The multipath number distributions follow both Poisson's and Gao's distributions, but Gao's distribution is better in the high probability region. Large excess delays up to 1.2 μs and rms delay spread about 0.42 μs are found in the urban rotation measurements, where the receiver is close to a large open square     

Sky brightness temperature measurements at 135 GHz and 215 GHz

Zenith sky brightness temperature measurements at 135 GHz and 215 GHz have been made on a semicontinuous basis for a period of seven months in the Gunston Cove area of Northern Virginia. These measurements were made using Dicke receivers with noise figures of 8 dB and 14 dB, respectively. A liquid nitrogen cooled load was used to calibrate the measurements. The 215 GHz sky temperature was on the average about 80 K greater than that at 135 GHz. Clouds were found to cause the sky temperatures to fluctuate as much as 150 K in a few minutes. Graphs are presented to outline general trends of the data as well as representative days, including the blizzard on February 11, 1983. In addition, empirical relations between precipitable water vapor, atmospheric water density at the surface, sky brightness temperatures, and zenith attenuation are given for visually clear days.     

Empirical characterization of wideband indoor radio channel at 5.3GHz

Characteristics of wideband indoor radio channel at 5.3 GHz were defined based on an extensive measurement campaign using a wideband channel sounder with 19 ns delay resolution. Pathloss exponents were 1.3-1.5 in LOS and 2.9-4.8 in non-line of sight (NLOS). Large difference in NLOS exponents was due to different dominating propagation mechanisms in different types of building structures. The delay dispersion was characterized by cumulative distribution functions (CDF) of the RMS delay spreads, the values for CDF=0.9 varied from 20 to 180 ns in different setups in an office building and large hall environments. The correlation functions of the radio channel in spatial and frequency domains were extracted. Small scale models for five typical indoor scenarios were developed using tapped delay lines     

Waveguide attenuation measurements at 890 GHz

A modified H guide has been proposed as a low-loss low-mode waveguide for the submillimetre-wave region, and is supported by theoretical studies and microwave model measurements. A resonance technique using guide-length variation with temperature change for attenuation and mode-characteristic measurement is shown to be feasible at 890 GHz with an HCN laser. Guide attenuations less than 8 dB/m are obtained in initial measurements on a submillimetre waveguide.     

Surface resistance measurements at 337 GHz

A high Q quasioptical hemispherical resonator, capable of making measurements on samples as small as 5 mm in diameter, was used to make surface resistance measurements at 337 GHz on samples of Al, Au, Mo, and Cu. Results for A1 agree with the low frequency approximation, the other metals are some what higher.     

2.5 GHz and 5 GHz harmonic mode-locking of a diode-pumped bulkerbium-ytterbium glass laser at 1.5 microns

Third-order harmonic mode locking of a diode-laser pumped bulk Er:Yb:glass laser by frequency modulation with a lithium niobate modulator is reported. Stable pulses at a repetition rate of 2.5 and 5 GHz with a pulse duration down to 9.6 ps are obtained. The average output power is 3 mW, the pulse peak power is 120 mW at 2.5 GHz repetition rate, and the pulses are approximately 1.4 times transform limited. The pulse duration can be increased up to 30 ps by decreasing the mode-locker drive power     

SiGe bipolar transceiver circuits operating at 60 GHz

A low-noise amplifier, direct-conversion quadrature mixer, power amplifier, and voltage-controlled oscillators have been implemented in a 0.12-/spl mu/m, 200-GHz f/sub T/290-GHz f/sub MAX/ SiGe bipolar technology for operation at 60 GHz. At 61.5 GHz, the two-stage LNA achieves 4.5-dB NF, 15-dB gain, consuming 6 mA from 1.8 V. This is the first known demonstration of a silicon LNA at V-band. The downconverter consists of a preamplifier, I/Q double-balanced mixers, a frequency tripler, and a quadrature generator, and is again the first known demonstration of silicon active mixers at V-band. At 60 GHz, the downconverter gain is 18.6 dB and the NF is 13.3 dB, and the circuit consumes 55 mA from 2.7 V, while the output buffers consume an additional 52 mA. The balanced class-AB PA provides 10.8-dB gain, +11.2-dBm 1-dB compression point, 4.3% maximum PAE, and 16-dBm saturated output power. Finally, fully differential Colpitts VCOs have been implemented at 22 and 67 GHz. The 67-GHz VCO has a phase noise better than -98 dBc/Hz at 1-MHz offset, and provides a 3.1% tuning range for 8-mA current consumption from a 3-V supply.     

Overwater line-of-sight fade and diversity measurements at 37 GHz

The results of line-of-sight propagation measurements at 37 GHz over a 10.0-mile overwater test site are presented. Measurements of the short-term fading statistics, and of the time, space, and frequency diversity parameters are included. Strong negative correlation was observed during both the space and frequency diversity measurements; negative correlation coefficients were as large as -0.8. The diversity improvement obtained was greater than the value expected from correlation calculations, which is attributed to the consistent occurrence of negative correlation in the vicinity of the interference nulls rather than the random occurrence assumed in the calculations. For the optimum case where maximum negative correlation occurs, sufficient diversity improvement is achieved with either space or frequency diversity to permit the elimination of almost the entire fade margin that is needed to overcome the multipath fading associated with reflections from the water surface.     

Mode partition noise of nearly single-mode semiconductor lasersmodulated at GHz rates

A new method to calculate very low errors due to mode partition noise in nearly single-mode semiconductor lasers has been developed. The laser is intensity modulated at GHz rates. The method allows us to obtain the error for a periodic sequence of input bits as a function of the threshold gain difference for different values of the bias current, above and below threshold, injected current in the ON state and modulation frequency. It is shown that bounds for the error under pseudorandom modulation conditions can be obtained from the periodic and gain switching sequences. The required threshold gain difference for an error of 10^-9 is calculated, and it is shown to increase with the current in the ON state. We also observe pattern effects at the output of the laser, for bias current above threshold, due do the pseudorandom sequence of input bits. For a special value of the bias current slightly below threshold, these patterns effects are suppressed and the error is independent of the modulation frequency and of the modulation regime     

Results of XPD site-diversity measurements at 11.8 GHz

The re-use of frequencies in the coming satellite telecommunications systems by means of orthogonal polarisations is based on the knowledge of the values of crosspolarisation discrimination (XPD) which are to be expected. The letter gives results of about one year's measurements of the improvement in XPD due to site diversity.     

Terrain backscatter measurements at 40 to 90 GHz

Experimental measurements were made under controlled laboratory conditions to determine terrain backscatter in the 40- to 90-GHz frequency range. Terrain samples in a dry and wet condition included asphalt, concrete, gravel, wood, sod, and tall weeds. Smooth and rough water were also included. Thebar{sigma}_{0}was established for angles of incidence from normal to45degwith the assumption thatbar{sigma}_{0}was frequency independent.     

2-D localization and identification based on SAW ID-tags at 2.5 GHz

An identification and localization system based on surface acoustic wave (SAW) radio sensors is presented in this paper. This system is able to identify and localize objects within a two-dimensional area. Identification is achieved with a fixed coded passive SAW identification-tag. Localization is carried out with three receiving antennas and with a following analysis of time delay between the sent interrogation signal and the received signals. For practical tests, a special interrogator has been established, as well as the receiving and demodulation unit. The whole system is controlled by a computer.     

Hemispherical power gain pattern measurements at 7.5 GHz

A technique is described for measuring the complete hemispherical power-gain radiation pattern of a 2.44-m diameter paraboloidal reflector antenna mounted atop a mobile small earth terminal operating at 7.5 GHz. Antenna power-gain data were measured versus azimuth and elevation angles with the earth terminal centered on a heavy-duty turntable flush with test range ground.Test site illumination was achieved with airborne transmitting antennas. Conventional and statistical power-gain patterns are presented for left-hand circular polarization and cross polarization. Results indicate that similar systems cannot rely upon orthogonal polarization to provide isolation or compatibility beyond the angular region of the main lobe.     

High resolution 20 GHz wideband delay generator

A digitally-programmable method for linearly controlling signal delay over a wide frequency and delay range has been developed. Circuits were fabricated in the HRL's G2+ InP HBT technology. Test results at 20 GHz confirm simulation results, showing a 5 ps range in delay, ramped in 16 steps to provide a 0.3 ps resolution step. Larger delay ranges are possible by combining several of the delay cells in series.     

Comparative study of millimeter wave propagation at 30 GHz and 60 GHz in indoor environment

The millimeter wave band appears to be a favourable choice for personal wireless communication systems for indoor environment, as it meets the requirements for sufficient bandwidth, small terminal dimensions and sporadic usage for commercial applications. In this paper measurements of millimeter wave propagation in both 30 GHz and 60 GHz bands, are presented in a comparative way. The topology of measurements covers both a line-of-sight situation and also a case where a direct path between transmitter and receiver does not exist. Although the second case does not seem obvious for outdoor applications in these frequencies, in indoor environment the multipath signals produced by objects like walls, doors, furniture etc., can be utilised in order to overcome the man-made shadowing. Both slow and fast fading characteristics of the received signal are studied and the measurements are modelled by the conventional Rician and Rayleigh distributions. Both frequency bands offer advantages for usage in in-house wireless communication systems. Although in 30 GHz band the coverage area is bigger than in 60 GHz (with the same transmitting power), frequency reuse is easier in 60 GHz band. because even if millimeter waves ‘escape’ through ‘windows’, the specific attenuation due to atmospheric oxygen (15 dB/km) at 60 GHz eliminates the interference between communication channels in neighbouring buildings.