Broadband: the last mile

The regulatory and service drivers that are prerequisites for local access evolution to the broadband integrated services digital networks are discussed. A tutorial on the state of the art in relevant technologies is presented, and it is shown that many of the technologies are not yet mature. The broadband technologies discussed are analog cable television systems, optical fiber, optical amplifiers, optical receivers, transceivers, and image compression systems. Regulatory considerations include bandwidth on demand and competition     

165-GHz Transceiver in SiGe Technology

Two D-band transceivers, with and without amplifiers and static frequency divider, transmitting simultaneously in the 80-GHz and 160-GHz bands, are fabricated in SiGe HBT technology. The transceivers feature an 80-GHz quadrature Colpitts oscillator with differential outputs at 160 GHz, a double-balanced Gilbert-cell mixer, 170-GHz amplifiers and broadband 70-GHz to 180-GHz vertically stacked transformers for single-ended to differential conversion. For the transceiver with amplifiers and static frequency divider, which marks the highest level of integration above 100 GHz in silicon, the peak differential down-conversion gain is -3 dB for RF inputs at 165 GHz. The single-ended, 165-GHz transmitter output generates -3.5 dBm, while the 82.5-GHz differential output power is +2.5 dBm. This transceiver occupies 840 mum times 1365 mum, is biased from 3.3 V, and consumes 0.9 W. Two stand-alone 5-stage amplifiers, centered at 140 GHz and 170 GHz, were also fabricated showing 17 dB and 15 dB gain at 140 GHz and 170 GHz, respectively. The saturated output power of the amplifiers is +1 dBm at 130 GHz and 0 dBm at 165 GHz. All circuits were characterized over temperature up to 125degC. These results demonstrate for the first time the feasibility of SiGe BiCMOS technology for circuits in the 100-180-GHz range.     

Tapered-magnitude lossy bandpass networks†

Bandpass lossy matching networks (both lumped and distributed) having sloped gain versus frequency characteristics are presented. These networks have approximately 6dB/octave slope in gain against frequency and acceptable impedance matching properties at the input and output ports. This type of network is very useful in the matching of broadband UHF and microwave power amplifiers.     

基于神经网络的宽带功放动态非线性行为建模

文章主要讨论了如何利用神经网络对宽带功放进行动态非线性行为建模的问题。首先简述了功放的动态非线性特性及行为建模的方法。然后回顾了基于实数时延前馈神经网络、径向基函数神经网络等浅层神经网络构建的功放动态非线性行为模型。在此基础上,针对5G/6G宽带功放具有更强的记忆效应的问题,重点分析了如何使用长短期记忆(LSTM)神经网络对功放的动态非线性进行精确的行为建模。最后展望了构建具有普适性的功放非线性行为模型将是5G/6G通信时代功放非线性建模的一个重要发展方向。     

CMOS mm-wave transceivers for Gbps wireless communication

The challenges in the design of CMOS millimeter-wave (mm-wave) transceiver for Gbps wireless communication are discussed. To support the Gbps data rate, the link bandwidth of the receiver/transmitter must be wide enough, which puts a lot of pressure on the mm-wave front-end as well as on the baseband circuit. This paper discusses the effects of the limited link bandwidth on the transceiver system performance and overviews the bandwidth expansion techniques for mm-wave amplifiers and IF programmable gain amplifier. Furthermore, dual-mode power amplifier (PA) and self-healing technique are introduced to improve the PA''s average efficiency and to deal with the process, voltage, and temperature variation issue, respectively. Several fully-integrated CMOS mm-wave transceivers are also presented to give a short overview on the state-of-the-art mm-wave transceivers.     

Transmission of many WDM channels through a cascade of EDFA's inlong-distance links and ring networks

We analyze the transmission of many wavelength-division-multiplexed (WDM) channels through a cascade of erbium-doped fiber amplifiers (EDFA) in both long-distance links and ring-based networks. For a megameter long-distance system, optimal operating conditions are found for achieving a high signal-to-noise ratio (SNR) per channel with as small an SNR differential as possible between 20 WDM channels spaced 0.5 nm apart. Critical issues addressed in this paper include: (a) the non-uniformity of the EDFA gain with wavelength: (b) the link loss between amplifiers; (c) the small-signal gain per amplifier; and (d) the input signal power     

Output power excursions in a cascade of EDFAs fed by multichannelburst-mode packet traffic: experimentation and modeling

A serious problem facing wavelength-division multiplexed (WDM) networks with fiber amplifier cascades is transient cross-gain saturation or gain dynamics of fiber amplifiers. Attention has been focused primarily on circuit-switched scenarios. When the number of WDM channels transmitted through a circuit-switching network varies, channel addition/removal will tend to perturb signals at the surviving channels that share all or part of the route. Even more serious bit error rate deterioration can arise in WDM packet switched burst mode networks. In this paper, we present experimental and theoretical results demonstrating the effect of fast power transients in erbium-doped fiber amplifiers (EDFAs) on packetized traffic transmitted through a chain of five EDFAs. Traffic of a local-area network has been transmitted over three channels. The effect of EDFA cross-gain saturation due to the burstiness of the traffic has been observed in a continuous-wave monitoring channel. The stabilizing effect of gain clamping of the first EDFA in the cascade has been investigated. The experimental results are extended to eight-channel WDM system using a large signal numerical analysis     

A Gaussian Approximation of High-Order Distortion Spectrum in Broadband Amplifiers

A novel analytical Gaussian approximation is developed for the evaluation of the distortion spectrum introduced by a nonlinear amplifier. This method allows to consider high-order distortion contributions when the device is driven by a broadband signal with Gaussian amplitude distribution. The results are applied to a ninth-order power series model based on well known single-tone and two-tone analysis parameters. The cascade of two or more amplifiers is investigated as well providing a complete set of tools for the early system specification of broadband transceivers. Simulations shows excellent agreement even for high input power levels, when former third-order and fifth-order approximations fail to yield accurate predictions.      

On distributed Raman amplification for ultrabroad-band long-haulWDM systems

We present an analysis and design method for multiwavelength pumped fiber Raman amplifiers for massive wavelength division multiplexing (WDM) systems with signal bandwidths of 10 to 12 THz and a very large number of channels. We solve self-consistently the optimal design problem for backward-pumped distributed Raman amplifiers with special gain profiles that compensate for the Raman tilt and wavelength-dependent fiber loss. We study the noise performance of these optimally designed amplifiers and address the issues of multispan amplification for long-haul transmission of such broadband signals     

Overview for the Special Section on the 2007 Radio Frequency Integrated Circuits Symposium

The papers in this special section reflect the general challenges that RF IC designers are confronting: mainly, practical integration of CMOS power amplifiers, implementation of integrated circuits from 60 GHz to above 100 GHz, and various circuit techniques to enable broadband/multi-band transceivers.     

Prospects of CMOS technology for high-speed optical communication circuits

This paper describes the capabilities of deep-submicron CMOS technologies for the realization of highly integrated optical communication transceivers in the range of tens of gigabits per second. Following an overview of a CMOS process, the design of traditional and modern transceivers is presented and speed and integration issues are discussed. Next, the problem of equalization is addressed. Finally, the design of critical building blocks such as broadband amplifiers and high-speed oscillators is described and a method of estimating the jitter is introduced.     

Numerical comparison between distributed and discrete amplificationin a point-to-point 40-Gb/s 40-WDM-Based transmission system with threedifferent modulation formats

We describe a detailed numerical investigation on the relative merits of gain flattened distributed Raman amplification (DRA) and discrete gain flattened amplifiers. We simulate a system with forty 40-Gb/s channels spaced at 100 GHz and compare the performance of three different modulation formats nonreturn-to-zero (NRZ), return-to-zero (RZ) and carrier-suppressed RZ (CS-RZ). Three types of amplifiers, multifrequency backward- and forward-pumped DRAs, and an idealized discrete gain flattened amplifier are examined for various signal powers and transmission distances. For the backward-pumped DRA, we also describe calculated tolerance limits imposed by incomplete dispersion slope compensation and polarization mode dispersion (PMD) level     

Invariance of S21/S12 and K-factor underparallel operation of linear two-port devices

Based on a generalized circuit model for parallel-operated amplifiers with linear two-port devices, it has been proved that the S-parameter ratio S₂₁/S₁₂ and hence MSG (maximum stable gain) are invariant as long as the devices have an identical value of S₂₁/S₁₂ and the input and output networks are reciprocal. The invariance of K factor has been shown to hold for two cases: (i) devices are identical and input/output networks are lossless and symmetric with respect to each device, and (ii) identical admittances are added to the networks of case (i) so as to connect every device port with each other. Thus at least in these two cases, MAG (maximum available gain) and U (unilateral gain) are invariant as well as MSG under parallel operation of linear two-port devices. The invariance of S₂₁/S₁₂ and hence MSG applies to a variety of parallel-operated amplifiers such as distributed amplifiers and linear power amplifiers     

多波长抽运C+L波段喇曼放大器的数值模拟与分析

为了合理地设计出宽带分布式光纤喇曼放大器系统,采用理论分析与数值模拟相结合的方法,对前向抽运方式的喇曼耦合方程进行数值仿真,获得了合适的抽运源波长,从而实现了分布式喇曼光纤放大器的带宽为80nm(1530nm～1610nm).在抽运功率均匀分配的情况下,对80个信道的信号进行分布式放大,分析了不同信号、抽运功率沿光纤的...     

1111 km, two channel IM-DD transmission experiment at 2.5 Gb/sthrough 21 in-line erbium-doped fiber amplifiers

Two-channel transmission is demonstrated in a 2.5 Gb/s intensity-modulated direct-detection system over a distance of 1111 km, using 21 in-line erbium-doped fiber amplifiers. The two channels incur virtually no penalty when they are transmitted simultaneously. Owing to the use of gain filtering in the amplifiers instead of discrete in-line optical filters, the overall bandwidth of the link is about 15 nm, for a sensitivity penalty smaller than 1 dB on one single transmitted channel     

True Broadband Technique for On-Chip-Series Connection of TWAs Using Differential Distributed Amplifiers

A new technique for series connection of monolithic broadband travelling wave amplifiers (TWAs) is presented, using differential distributed architectures. This technique is intrinsically broadband because no series capacitor is used, it starts operating at dc up to cut-off frequency. With a GaAs heterojunction bipolar transistor monolithic microwave integrated circuit process, two on-chip-series coupled 18 dB gain and 23 GHz cut-off frequency TWAs are realized. Our approach avoids packaging steps and hybrid components. This is a very promising result for monolithic high-gain broadband amplifiers.     

Mobile broadband system (MBS): trends and impact on 60 GHz bandMMIC development

The RACE mobile broadband system (MBS) project aims to extend the broadband integrated services digital network (B-ISDN) to mobile users. To meet the future demand for broadband wireless picocell networks, frequencies have been allocated in the 62-63 and 65-66 GHz bands. However, for the use of a mobile broadband system to become widespread it is necessary to develop relatively low cost transceivers based on millimetre wave GaAs P-HEMT MMICs. A transceiver architecture and elementary building blocks have been defined. 60 GHz transistor models have been refined and circuit design, layout and simulation achieved. Future cost decrease is a function of the MMIC manufacturing yield, since a high yield allows a higher layout density and consequently fewer MMICs per transceiver, and of the improvement in packaging techniques above 60 GHz     

A wavelength encoded multichannel optical bus for local areanetworks

A scalable, high-speed, wavelength encoded multichannel optical bus (WEMCOB) employing the wavelength division multiplexing (WDM) technology is proposed to reduce the link speed requirement, the wiring complexity, and the number of optical amplifiers for local area networks. In this paper, a hierarchical network topology is adopted, in which a dual unidirectional WEMCOB with separate control and data channels composes the backbone network, and unidirectional tree-based WEMCOB's with centralized arbiters constitute the subnetworks. We perform a feasibility study on the implementation of a local area network based on the WEMCOB, discuss the related issues, and show that a total transmission capacity of several tens of gigabits per second (Gb/s) can be achieved to serve a large number of broadband users by utilizing today's optoelectronic technology     

基于最优匹配网络的宽带功率放大器设计

针对宽带功率放大器的需求,以及传统匹配网络只能用于实现窄带设计的现状,在匹配网络研究的基础上,提出了一种可行的、有效的宽带功率放大器匹配网络的设计方法。基于该方法,对最优匹配网络算法进行Matlab建模,并利用ADS软件进行了仿真和优化,实现了1~2.8 GHz宽带功率放大器。对设计的宽带功率放大器进行测试,结果表明,在1~2.8 GHz宽频带范围内,增益为27 dB,平坦度为±1 dB,输入回波损耗小于－10 dB,匹配性能明显优于其他类型的拓扑结构。该方法对于设计宽带功率放大器具有良好的应用价值。     

Large bandwidth BiCMOS operational amplifiers for SC videoapplications

A single-ended and a fully differential broadband BiCMOS operational amplifier for switched-capacitor video applications are presented. The amplifiers feature a folded cascode gain stage with a current source as output load. For the single-ended amplifier the current mirroring is accomplished with a modified bipolar Wilson current mirror at the output of the differential pair. Symbolic expressions for the transfer functions for both amplifiers are derived. The amplifiers are integrated in an analog 1 μm BiCMOS process with an active die area of 0.72 mm² and 0.96 mm² for the single-ended and the fully differential amplifier, respectively. For both amplifiers a DC-gain of 68 dB and a unity gain frequency greater than 250 MHz was measured for a power supply voltage of 5 V