共查询到20条相似文献,搜索用时 130 毫秒
1.
Gene J.M. Winzer P.J. Essiambre R.-J. Chandrasekhar S. Painchaud Y. Guy M. 《Photonics Technology Letters, IEEE》2007,19(16):1224-1226
We report on experimental investigations of real-time maximum-likelihood sequence estimation (MLSE) in the presence of narrowband optical filtering, using 10.7-Gb/s nonreturn-to-zero ON-OFF keying and a fiber grating filter with 6.25-GHz bandwidth. Compared to standard threshold detection, the MLSE eliminates a 10-3 error floor due to narrowband optical filtering and results in DFB a <2-dB optical signal-to-noise ratio penalty at a 10-3 bit-error ratio. Furthermore, we demonstrate the ability of the MLSE to simultaneously compensate for narrowband optical filtering and chromatic dispersion. Finally, we investigate the influence of narrowband filter frequency detuning and show that the well-known effect of increased filtering tolerance given by the vestigial sideband effect observed in standard threshold detection, disappears in the presence of the MLSE. 相似文献
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An 8-MHz seventh-degree elliptic-function low-pass filter is described, demonstrating an approach to low-distortion antialias filtering for high-definition video applications. The filter's performance goals are achieved through the use of circuit design principles that capitalize on the strengths of BiCMOS technology. The integrator circuits composing the filter consist of a new wideband low-distortion transconductor circuit and a unique BiCMOS Miller-stage circuit. Integrator time constants are determined by stable RC products, enabling a simplified filter calibration scheme that is insensitive to temperature-induced variations and requires no phaselock circuits. The prototype filter IC, consisting of seven integrators assembled in an active-ladder configuration, was fabricated in a 10-V, 2-μm 2.5-GHz BiCMOS technology that also features thin-film resistors and polysilicon-plate capacitors. Measured results from the calibrated filter show passband flatness of 0.2 dB, with aberrations of less than ±1 dB over a 100°C temperature range. Stopband attenuation meets its designed goal of 60 dB. Driven by 7-Vpp, differential input signals, the filter exhibits less than -72-dBc third-order intermodulation distortion products at 1 MHz. For 5-Vpp inputs at 4 MHz, third-order intermodulation spurs remain below -65 dBc 相似文献
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The use of wide-bandwidth interdigital microwave circuits to provide electrooptic modulation of light is discussed. Two models employing lithium niobate crystals of different aspect ratios have been constructed and tested. Both have nominal bandwidth from 1.0 to 2.0 GHz but actually give somewhat greater modulation bandwidth. Single-pass modulation tests made using 6328-Å light at RF drive power level of 5 watts show that 30 percent modulation depth over a 1.5-GHz frequency band is obtained for one model while approximately 50 percent modulation depth over a 1.1-GHz band is obtained for the other. These results show excellent agreement with analytical predictions. Measurement techniques are also discussed. 相似文献
4.
This letter proposes a wideband bandpass filter by cascading two 3-dB stepped-impedance cascadable 180deg hybrid rings with a pair of stepped-impedance lines. Thanks to the stepped-impedance lines, a broad upper stopband is achieved. The stepped-impedance vertically installed planar (VIP) coupler is used to implement the ideal 180deg phase inverter and crossovers. The experimental results show that this 2-GHz center frequency, fourth order filter has a 10-dB return loss bandwidth of 92.5% and upper stopband rejection levels of better than -20 dB up to 6.8 GHz. This proposed filter achieves wide passband and broad stopband performance simultaneously. 相似文献
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宽带数字下变频的一种高效实现结构 总被引:19,自引:2,他引:17
宽带数字接收系统要以大的调谐带宽截获窄带信号,要求数字下变频器具有高的数据率和快的调谐时间,现有的商用数字下变频器不能满足这些要求。本文提出一种高效实现结构,综合利用DFT滤波器的灵活性和多相滤波的高效性,按照先抽取数据,再低通滤波、混频的顺序,较好地解决了硬件速度和高速数据流不匹配的问题。计算机模拟结果证明了处理结构的有效性。 相似文献
7.
A new circuit design for narrowband microwave active filters is presented. By increasing the tank circuit unloaded Q-valve an ideal one-section bandpass filter is realised. The planar distributed structure is suitable for both MIC and MMIC circuits.<> 相似文献
8.
《Microwave Theory and Techniques》1976,24(5):237-241
A new Michelson-interferometer (MI) hybrid having a miter angle is developed for use as a millimeter-wave band-splitting filter. The construction and operating principle of the filter are described. The design method and the experimental results are also presented. This filter has low branching loss, yet keeps very wide band characteristics. For the 4W-120-GHz-frequency-range filter with 35/spl deg/ miter angle, the branching loss is 0.68-1.56dB. This is about 40 percent lower than that of the conventional MI filter. The input VSWR is less than 1.29 and the guard bandwidth is less than 250 MHz. This filter can be used for the 40-120-GHz guided-millimeter-wave transmission systems. 相似文献
9.
《Microwave and Wireless Components Letters, IEEE》2009,19(3):158-160
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《Microwave Theory and Techniques》2009,57(7):1767-1773
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《Microwave Theory and Techniques》1986,34(10):1059-1063
A new, computer-assisted method, based on small-signal "S" parameters, is described for the systematic design of wide-band VCO's. The method has been applied to design 6-12-GHz and 12-18-GHz GaAs FET VCO's, and it has shown an excellent capability to predict the maximum obtainable tuning bandwidth. The tuning linearity of the VCO's has also been optimized Delta f/f <= +-0.4 percent over a 3-GHz bandwidth. 相似文献
14.
40-GHz coplanar waveguide bandpass filters on silicon substrate 总被引:3,自引:0,他引:3
Chan K.T. Chen C.Y. Chin A. Hsieh J.C. Liu J. Duh T.S. Lin W.J. 《Microwave and Wireless Components Letters, IEEE》2002,12(11):429-431
We report a very simple process to fabricate high performance filter on Si at 40 GHz using proton implantation. The filter has only -3.4-dB loss at peak transmission of 40 GHz with a broad 9-GHz bandwidth. In sharp contrast, the filter on 1.5-/spl mu/m SiO/sub 2/ isolated Si has much worse transmission and reflection loss. This is the first demonstration of high performance filter at the millimeter-wave regime on Si with process compatible with current VLSI technology. 相似文献
15.
《Microwave Theory and Techniques》1985,33(2):135-142
This paper discusses development, for the 240-GHz region, of whisker contacted diode mixers with LO powers between 10 and 50 µW. Mixer requirements for low parasitic diodes, situated in high-embedding impedance circuits are described and appropriate RF and IF circuit designs presented. A capacitive post RF matching circuit for a full-height waveguide is developed with superior bandwidth characteristics at high impedance levels and greater ease of fabrication than usual matching circuits in reduced height guide. Corroborating experimental results are presented for an X-band model and for a 235-GHz mixer. 相似文献
16.
Chiang P. Dally W.J. Lee M.-J.E. Senthinathan R. Yangjin Oh Horowitz M.A. 《Solid-State Circuits, IEEE Journal of》2005,40(4):1004-1011
A 20-Gb/s transmitter is implemented in 0.13-/spl mu/m CMOS technology. An on-die 10-GHz LC oscillator phase-locked loop (PLL) creates two sinusoidal 10-GHz complementary clock phases as well as eight 2.5-GHz interleaved feedback divider clock phases. After a 2/sup 20/-1 pseudorandom bit sequence generator (PRBS) creates eight 2.5-Gb/s data streams, the eight 2.5-GHz interleaved clocks 4:1 multiplex the eight 2.5-Gb/s data streams to two 10-Gb/s data streams. 10-GHz analog sample-and-hold circuits retime the two 10-Gb/s data streams to be in phase with the 10-GHz complementary clocks. Two-tap equalization of the 10-Gb/s data streams compensate for bandwidth rolloff of the 10-Gb/s data outputs at the 10-GHz analog latches. A final 20-Gb/s 2:1 output multiplexer, clocked by the complementary 10-GHz clock phases, creates 20-Gb/s data from the two retimed 10-Gb/s data streams. The LC-VCO is integrated with the output multiplexer and analog latches, resonating the load and eliminating the need for clock buffers, reducing power supply induced jitter and static phase mismatch. Power, active die area, and jitter (rms/pk-pk) are 165 mW, 650 /spl mu/m/spl times/350 /spl mu/m, and 2.37 ps/15 ps, respectively. 相似文献
17.
Broad bandwidth amplifiers are typically limited in their spurious free dynamic range by second-order products. We have demonstrated more than 30 dB reduction in second-order products for amplifiers with 1-2 octaves of bandwidth utilizing a novel circuit approach. Improved planar baluns (180° transformers) are combined with differential amplifiers fabricated from 0.25-μm GaAs pseudomorphic high electron mobility transistors to implement 4-16-GHz and 3-6-GHz small-signal amplifiers. Measured values of OIP2 exceed 60 dBm with a 1-dB compression level of approximately 5 dBm. These unprecedented levels enable miniaturized, low-power front ends for broad bandwidth microwave systems 相似文献
18.
Jiangzhou Wang Milstein L.B. 《Selected Areas in Communications, IEEE Journal on》1996,14(8):1548-1559
This paper extends and complements previous research we have performed on the performance of nonadaptive narrowband suppression filters when used in cellular code-division multiple-access (CDMA) overlay situations. An adaptive least mean square (LMS) filter is applied to a cellular CDMA overlay in order to reject narrowband interference. An accurate expression for the steady-state tap-weight covariance matrix is derived for the real LMS algorithm for arbitrary statistics of the overlaid interference. Numerical results illustrate that when the ratio of the narrowband interference bandwidth to the spread spectrum bandwidth is small, the LMS filter is very effective in rejecting the narrowband interference. Furthermore, it is seen that the performance of the LMS filter in a CDMA overlay environment is not significantly worse than the performance of an ideal Wiener filter, assuming the LMS filter has had sufficient time to converge 相似文献
19.
It has been proposed that CDMA systems can be assigned to spectral bands which are presently occupied by narrowband users to further increase spectral capacity. Such CDMA overlay systems could provide new options for efficient utilization of the spectrum with minimal disruption to existing narrowband users, especially if adaptive interference suppression techniques are utilized in the spread spectrum receiver. Previous studies have defined the SNR improvement ratio which can be achieved for tone interferers and for narrowband interferers for which the center frequency of the interference is at the carrier frequency of the CDMA signal. In this paper the bit-error-rate (BER) performance of the mobile-to-base link of a CDMA system for a single narrowband user which occupies a significant portion of the CDMA bandwidth is evaluated. It is shown that the narrowband model used in previous studies does not apply in this case, especially for the large, effective, bandwidths which are characteristic of the interferers in the overlay system. The dependence of the BER on the filter order, the bandwidth of the interference, and its center frequency relative to the CDMA carrier frequency are defined. Additionally the increase in BER for a digital implementation of the adaptive suppression filter relative to the optimal Wiener filter is characterized with respect to the adaptive time constant and the quantization errors due to finite wordlength. It is shown that these implementation errors can be made negligible compared to the errors which are characteristic of the optimal Wiener filter. Analytic results are validated by simulation for typical system parameters 相似文献
20.
《Microwave Theory and Techniques》1985,33(6):543-545
A low-noise and low-power GaAs monolithic broad-band amplifier is proposed and has been developed, which has a new cascade connection with a large gate-width input FET and the other circuits in such a way that the output stage current flows through the input FET. The fabricated amplifier operates on +5-V single supply voltage, and provides a 3.3-dB noise figure, less than 180-mW power dissipation, and a 10-MHz--2.0-GHz bandwidth with 16-dB gain. 相似文献