100-channel optical FDM transmission/distribution at 622 Mbit/s over 50 km utilising a waveguide frequency selection switch

100-channel optical FDM transmission/distribution at 622 Mbit/s is demonstrated for a fibre length of 50 km. A polarisation-insensitive waveguide frequency-selection-switch with 10 GHz intervals and an FSK/direct-detection scheme using a Mach-Zehnder filter type optical frequency discriminator are verified as feasible.<>     

Coplanar stripline resonators modeling and applications to filters

This paper presents coplanar stripline (CPS) resonators and their practical implementations to filters. Five types of CPS resonator are built using open and short-ended strips. Lumped-element equivalent circuits are presented for each resonator. Their performances are investigated and compared in terms of Q factor or bandwidth. Two types of bandpass filter are developed with the resonators. The bandpass filters have low-passband insertion losses and wide-stopband suppression bandwidths. Lumped-element equivalent circuits are presented for the bandpass filters. A wide-band CPS-to-microstrip transition is developed for the measurements. The back-to-back transition has an insertion loss of less than 3 dB and a return loss of better than 10 dB for the frequency range from 1.3 to 13.3 GHz (1:10.2)     

System design and long-span transmission experiments on an optical FSK heterodyne single filter detection system

The influence of LD phase noise on a heterodyne noncoherent detection system was evaluated. Based on the evaluation, an optical FSK heterodyne single filter detection system with large frequency deviation and wide-band IF filter has been developed to allow use of stand-alone DFB LD's. In the system, a phase tunable DFB LD was used as an FSK transmitter light source to improve the FSK modulation characteristics. An IF filter with appropriate bandwidth evaded the influence of LD phase noise. With these configurations, long-span (243 km at 140 Mbit/s and 204 km at 280 Mhit/s) transmission experiments have been successfully carried out on this single filter detection system. To the contrary, influence of LD phase noise appeared in a limited IF bandwidth case, which agrees well with the theoretical evaluation.     

Design and analysis of a super compact wide-band bandpass filter based on metamaterial resonators

In this paper, a novel compact wide-band bandpass filter (BPF) with a wide frequency range is presented. This filter consisting of a multi-mode resonator (MMR) and four metamaterial unit-cells benefits from a very compact size. Unit-cells based on a complementary spiral resonator (CSR) including a metallic via, improve both upper and lower stopband rejection and compensate the insertion loss (I.L) within the passband altogether. This wide-band filter presents a 3-dB bandwidth of 7.7 GHz, ranging from 3 GHz to 10.7 GHz and the Insertion loss is less than 0.7 dB over the passband. The measured results are in good agreement with both the full-wave electromagnetic simulation and the proposed circuit model results. The dimension of the fabricated filter is 0.128 λ × 0.1 λ (i.e., 5.6 × 4.4 mm²). This filter is considerably compact compared to the other wide-band bandpass filters with the same substrate.     

29 GHz E-plane biphase modulator

A biphase PSK modulator for use in 29 GHz radio equipment has been developed that gives state-of-the-art performance (less than 3 dB insertion loss across 7% bandwidth, including transition losses, and 70/100 Mbit/s data rate using PIN diodes as the switching elements). A drive amplifier has been developed for use with the modulator that allows beam lead PIN diodes with a long minority carrier lifetime to be used in the circuit up to 70 Mbit/s.     

16-channel optical FDM distribution/transmission experiment utilising multichannel frequency stabiliser and waveguide frequency selection switch

A 16-channel, 622 Mbit/s optical FDM distribution/transmission system experiment is demonstrated for a fibre length of 13 km. The feasibility of a multicarrier frequency stabiliser and waveguide frequency selection switch for 5 GHz frequency intervals is verified.<>     

A 12–18-GHz Three-Pole RF MEMS Tunable Filter

This paper presents a state-of-the-art RF microelectromechanical systems (MEMS) wide-band tunable filter designed for the 12–18-GHz frequency range. The coplanar-waveguide filter, fabricated on a glass substrate using loaded resonators with RF MEMS capacitive switches, results in a tuning range of 40% with very fine resolution, and return loss better than 10 dB for the whole tuning range. The relative bandwidth of the filter is$hbox5.7pm hbox0.4hbox%$over the tuning range and the size of the filter is 8 mm$, times ,4$mm. The insertion loss is 5.5 and 8.2 dB at 17.8 and 12.2 GHz, respectively, for a 2-$hboxkOmega/hboxsq$bias line. The loss improves to 4.5 and 6.8 dB at 17.8 and 12.2 GHz, respectively, if the bias line resistance is increased to 20$hboxkOmega/hboxsq$. The measured$ IIP_3$level is$≫$37 dBm for$Delta f ≫ 200$kHz. To our knowledge, this is the widest band planar tunable filter to date.     

Generation and distribution of a wide-band continuously tunable millimeter-wave signal with an optical external modulation technique

A new technique to generate and distribute a wide-band continuously tunable millimeter-wave signal using an optical external modulator and a wavelength-fixed optical notch filter is proposed. The optical intensity modulator is biased to suppress the odd-order optical sidebands. The wavelength-fixed optical notch filter is then used to filter out the optical carrier. Two second-order optical sidebands are obtained at the output of the notch filter. A millimeter-wave signal that has four times the frequency of the microwave drive signal is generated by beating the two second-order optical sidebands at a photodetector. Since no tunable optical filter is used, the system is easy to implement. A system using an LiNbO/sub 3/ intensity modulator and a fiber Bragg grating filter is built. A stable and high spectral purity millimeter-wave signal tunable from 32 to 50 GHz is obtained by tuning the microwave drive signal from 8 to 12.5 GHz. The integrity of the generated millimeter-wave signal is maintained after transmission over a 25-km standard single-mode fiber. Theoretical analysis on the harmonic suppression with different modulation depths and filter attenuations is also discussed.     

Toward Wide-Band High-Resolution Analog-to-Digital Converters Using Hybrid Filter Bank Architecture

The paper presents the problem of design and simulation of a high-speed wide-band high-resolution analog-to-digital (ADC) converter working in a bandpass scenario. Such converters play a crucial role in software-defined radio and in cognitive radio technology. One way to circumvent the limits of today’s ADC technologies is to split the analog input signal into multiple components and then sample them with ADCs in parallel. The two main split approaches, time interleaved and frequency splitting, can be modeled using a filter bank paradigm, where each of these two architectures requires a specific analysis for its design. In this research, the frequency splitting approach was implemented with the use of a hybrid filter bank ADC, which requires an output digital filter bank perfectly matched to the input analog filter bank. To achieve this end, an analog transfer function, together with an assumption of strictly band-limited input signal, has been used to design the digital filter bank so far. In contrast, the author proposes dropping the band-limit assumption and shows that the out-of-band input signal has to be taken into account when designing a hybrid filter bank.     

基于波纹耦合微带线的可调谐带通滤波器

设计了一种紧凑5阶双零点可调谐带通滤波器。通过在传统梳状线滤波器中引入波纹耦合微带线结构,该滤波器可以在中心频率调谐过程中保持绝对带宽恒定,同时尺寸相较于传统方法可减小50%。谐振器中引入分布式补偿电容利于滤波器应用于高介电常数衬底的微带线结构。基于源与负载间的耦合,引入两个传输零点来提高滤波器的衰减特性。HFSS仿真结果显示,当加载的电容值为2.43 pF时,滤波器的中心频率为1.48 GHz,带宽为194 MHz,插入损耗为1.36 dB。随着加载电容值从2.15 pF增加到2.93 pF,滤波器的中心频率从1.55 GHz减小至1.37 GHz。保持绝对带宽恒定的情况下,通带内的插入损耗小于1.5 dB。     

一种用于高速QPSK解调的四次方环载波恢复电路

为解决高速QPSK信号全数字解调的技术瓶颈问题,采用模拟方案,研制了一种四次方环载波恢复电路,重点介绍了应用混频器上变频特性的宽带平方电路以及锁相环(PLL)载波提取电路的设计过程.测试结果表明,该载波恢复电路可以完成载频为720 MHz、码速率100 Mbit/s～1 Gbit/s范围的QPSK信号同步载波恢复,解决了高速信号相干解调中载波同步的关键技术问题.     

Multireflection optical multi/demultiplexer using interference filters

A multireflection multi/demultiplexer using interference filters is proposed. Light waves of different wavelengths are combined or separated while they propagate between two filter arrays. The insertion loss of the 6-channel demultiplexer was around 1dB.     

宽频带高插损电源滤波器的研制

军标认证测试对传导辐射有严格的要求,针对低辐射保密机柜传导超标的问题,设计了一种宽频带高差损滤波器.该滤波器能在9 kHz～1 GHz频段上提供超过80 dB的共模插入损耗,有效抑制了传导辐射.从设计原理、结构和材料选择上分别进行了阐述,并对实物进行了测试.测试结果表明该滤波器的研制符合设计需求.     

Transmission experiments through 101 km and 84 km of single-mode fibre at 274 Mbit/s and 420 Mbit/s

Four transmission experiments through low-loss single-mode optical fibre at 1.3 ?m have been performed at 274 Mbit/s and 420 Mbit/s with different objectives. The first demonstrates transmission through 101 km of single-mode fibre at 274 Mbit/s with negligible dispersion penalty. The second experiment at 274 Mbit/s and 84 km uses only components suitable for use in an undersea cable system. Two additional experiments, both at 420 Mbit/s, accomplish a bitrate × distance product of 35 GHzkm with 84 km of fibre and show no dispersion penalty with 63 km and 2.4 ps/km nm dispersion.     

Simultaneous single-fibre transmission of video and bidirectionalvoice/data using LiNbO3 guided-wave devices

A system experiment which uses integrated optics to effect bidirectional transmission on a single-mode fiber is described. The system has practical applications and provides more functionality than previously reported experimental systems. The system consists of a video link (180 Mbit/s) and a voice/data link (1.54 Mbit/s) to the end user and a return voice/data link (1.54 Mbit/s) from the end user. Two LiNbO ₃ devices are used to externally modulate lasers and a third is used in a novel way to demultiplex the incoming signals and to eliminate the need for an optical source at the user's end. The system operated over 4 km of standard single-mode fiber with a BER⩽10^-9 and excess margins (4.9, 9.3, and 28.1 dB) on the three links     

16-channel optical FDM distribution/transmission experiment utilising Er/sup 3+/-doped fibre amplifier

A 16-channel optical FDM distribution/transmission experiment at around 1534 nm wavelength is demonstrated utilising an Er/sup 3+/-doped fibre amplifier. 16 intensity-modulated optical signals at 622 Mbit/s were amplified simultaneously at a gain of 15.2-18.5 dB. One of the amplified signals is selected using the waveguide frequency selection switch and directly detected with a receiver sensitivity of -38 dBm (P/sub e/=10/sup -9/).<>     

TUNABLE FIBER FABRY-PEROT FILTER FOR OPTICAL CARRIER-SUPPRESSION AND SINGLE-SIDEBAND MODULATION IN RADIO OVER FIBER LINKS

A novel method of simultaneous realization of optical carrier-suppression and single-sideband modulation using fiber Fabry-Perot tunable filter is presented. In order to enhance transmission performance of radio over fiber links, we use a fiber Fabry-Perot tunable filter to filter out one sideband as well as suppress the optical carrier power. The results demonstrate 20.5dB and 14.2dB improvement in the signal noise ratios when 18GHz and 10GHz microwave signals carrying 5Mbit/s quadrature-phase-shift-keyed (QPSK) format data is transmitted over 35 km single mode fiber, respectively.     

Design Theory of Up-Converters for Use as Electronically-Tunable Filters (Sep. 1961 [T-MTT])

The up-converters discussed use a single diode, a wide-band impedance matching filter at their signal input, a moderately wide-band impedance matching filter at their pump input, and a narrow-band filter at their sideband output. With a narrow-band filter at the sideband output, the frequency which will be accepted by the amplifier can be controlled by varying the pump frequency. Analysis of the impedance matching problem involved shows that tuning ranges of the order of a half-octave to an octave are possible. Theory is presented for both the lower-sideband and upper-sideband types of tunable up-converters and for the design of the required impedance matching networks. It is shown that, because of the pump input bandwidth required, it will generally be necessary to accept some mismatch at the pump input. But, by use of a properly designed impedance matching filter, the reflection loss can be kept nearly constant across the pump band, and the incident pump power required is not unreasonable. It is seen that properly designed devices of this type using voltage-tunable pump oscillators should have wide tuning range, fast tuning capability a useful amount of gain, no image response, and a low noise figure.     

The Design of an ADPCM/TASI System for PCM Speech Compression

This paper describes the design of a digital speech interpolation (DSI) system called ADPCM/TASI for adaptive differential PCM with time assignment speech interpolation. This system is designed to compress the output of two T1 24-channel PCM carrier terminals into a 1.544 Mbit/s signal that can be transmitted over a single T1 carrier line. The design is based on a bit slice microprocessor structure. Alternative designs are also described.     

A broadly tunable wavelength-selectable WDM source using a fiberSagnac loop filter

In this letter, we describe a new discretely wavelength-selectable 1.5-μm source based on the use of a fiber Sagnac loop filter leading to the possibility of an efficient all-fiber source. The filter has an ~1.6-dB insertion loss, 14-dB peak-to-valley transmission ratios, and can be tuned to a very precise match with the International Telecommunications Union-wavelength-division-multiplexing grid. We demonstrate 25-channel outputs with precise 50-GHz channel spacings and very large (65 dB) output signal to background noise ratios