A tunable optoelectronic oscillator based on a tunable microwave attenuator

A novel realization of a wideband tunable optoelectronic oscillator (OEO) based on dual-port electrode Mach–Zehnder modulator (DMZM), a tunable microwave attenuator (TMA), and a chirped fiber Bragg grating (CFBG) is proposed and demonstrated. By simply adjusting the power ratio between the two arms of DMZM, the chirp of the DMZM will be tuned, and the center frequency of the microwave photonic filter will be tuned. When the OEO loop in the proposed system is closed, the output frequency of OEO is determined by the microwave photonic filter, and a high spectral purity microwave signal with a tunable frequency from 5.8 to 11 GHz is generated. The single sideband (SSB) phase noise of the generated signal could reach −107.4 dBc/Hz at an offset frequency of 10 kHz.     

一种基于半导体光放大器的Ku波段可调谐光电振荡器

基于半导体光放大器(SOA)的非线性偏振旋转效应,提出了一种可调谐双环路光电振荡器(OEO),并从理论上分析了这种设计的基本原理。实验测得了振荡频率为12.978 GHz的微波信号的频谱图和相位噪声图,并且在Ku波段通过直接调节SOA注入电流得到调谐范围为40MHz,调谐步长约为2MHz的微波信号输出。在整个调谐范围内,输出微波信号的相位噪声在偏离中心频率10kHz处低于-75dBc/Hz。     

A novel optoelectronic oscillator based on all optical signal processing

A novel dual-loop optoelectronic oscillator(OEO),which is constructed based on all optical signal processing,is proposed and analyzed.By inserting an erbium-doped fiber amplifier(EDFA) and a fiber Bragg grating(FBG) on the optical domain,the amplification and filter are implemented in the OEO loop.The performance of the OEO is improved without any electronic filter or electronic amplifier.A theoretical analysis is performed,and the generated microwave signal exhibits good performance with phase noise lower than -120 dBc/Hz at 10 kHz and a high side-mode suppression ratio(SMSR).     

基于激光外调制的频率可调谐光电振荡器

为了实现光电振荡器(OEO)输出频率的可调谐,提出了一种基于外调制激光的频率可调谐光电振荡器。此方案在单环OEO的基础上增加一个由微波滤波器、电衰减器、电放大器和电移相器构成的电增益选频腔,通过调节电移相器的偏置电压可以等效改变电选频腔的腔长,从而改变其输出微波信号的频率;同时调节光延时线来改变光电振荡器的起振模式,通过电增益选频腔信号与光电振荡器自由振荡信号的电注入锁定,即可实现频率可调谐的光电振荡器,其输出信号的频率由锁定OEO模式的电增益选频腔决定。实验结果表明,本方案产生了频率调谐范围为10.05 GHz~10.09 GHz、调谐步长为400 kHz的输出信号,频率在40 MHz的范围内连续可调谐。在输出频率为10.0519 GHz时,其边模抑制比为60 dB,相位噪声为-115 dBc/Hz @10 kHz。该方案结构简单,既保留了单环OEO低相位噪声的优势,又能有效抑制边模,为实现频率可调谐OEO提供了一种新的方法。     

基于可调谐真相移的可调谐光电振荡器

提出一种基于真相移(TPS)实现可调谐光电振荡器( OEO)的方案。只需通过调谐Mach-Zehnder 调制器(MZM)的偏置电压,就可以实现可谐滤波器的频谱响应的改变,即可实现TPS滤波器。 其中,两个抽头的可调谐滤波器是由双光源、双调制器以及叠印光栅来实现。OEO的输出频 率由二抽头可调 谐滤波器的峰值频率决定,而滤波器可调谐,这样就可以实现输出OEO的输出频率可调。 仿真结果表明,输出频率可以实现5～10GHz宽带宽可调谐。     

次谐波调制下光注入DFB-LD结构的可调谐光电振荡器

为实现具有高频谱纯度、低相位噪声的宽带可调谐微波信号生成,提出并通过实验验证了一种次谐波信号调制下光注入半导体激光器结构的光电振荡器,其原理为通过利用光注入半导体激光器的单周期（P1）振荡工作状态和波长选择放大特性实现可调微波信号生成,并进一步通过在光电振荡环路中引入次谐波信号调制对系统生成微波信号的频率稳定性、边模抑制比与频谱纯度进行优化。实验结果表明,文中方案提出的光电振荡器可以生成输出功率大于5 dBm,频率调谐范围为12~18 GHz的微波信号。同时,系统生成的微波信号的3 dB带宽为100 kHz,边模抑制比可达 51 dB,且信号在频偏量为100 Hz和10 kHz处的相位噪声分别为?78 dBc/Hz和?109 dBc/Hz。此外,光电振荡器生成微波信号的频率调谐范围只受系统中使用的各类光电器件工作带宽的限制,通过采用具有更大带宽的光电器件可以实现更高频率的微波信号生成。     

基于非线性色散补偿光栅的可调谐光电振荡器

为实现光电振荡器(OEO)输出频率的连续可调,提出一种新型的基于非线性色散补偿光栅(FBG)实现可调谐OEO方案。本文方案不需要电滤波器,且振荡频率随着光源的波长变化而变化。其中,三阶色散补偿FBG可以采用FBG重构算法设计。当光源波长从1 550.6nm变化到1 551.4nm时,相应的色散为340～1 460ps/nm,输出频率的调谐范围为6.5～13.5GHz,实现了振荡频率的大范围可调谐。     

微波超低相噪光电振荡器

介绍了一种基于光纤收发系统的新型微波振荡器.这种光电振荡器由两个反馈光纤延时环组成,各环路中包括光纤、光电探测器、放大器、滤波器和功分器/合成器.光电振荡器具有超低相噪、频谱纯、工作频率高和稳定度高的特点,可广泛应用于微波系统和光纤通信系统.     

Optoelectronic oscillator for photonic systems

We describe a novel photonic oscillator that converts continuous-light energy into stable and spectrally pure microwave signals. This optoelectronic oscillator (OEO) consists of a pump laser and a feedback circuit including an intensity modulator, an optical-fiber delay line, a photodetector an amplifier, and a filter. We present the results of a quasi-linear theory for describing the properties of the oscillator and their experimental verifications. Our findings indicate that the OEO can generate ultrastable, spectrally pure microwave-reference signals up to 75 GHz with a phase noise lower than -140 dBc/Hz at 10 KHz. We show that the OEO is a special voltage-controlled oscillator with an optical-output port and can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and a phase-locked loop. Other OEO applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb frequency and pulse generation, carrier recovery, and clock recovery     

The design of a 3-V 900-MHz CMOS bandpass amplifier

A new bandpass amplifier which performs both functions of low-noise amplifier (LNA) and bandpass filter (BPF) is proposed for the application of 900-MHz RF front-end in wireless receivers. In the proposed amplifier, the positive-feedback Q-enhancement technique is used to overcome the low-gain low-Q characteristics of the CMOS tuned amplifier. The Miller-capacitance tuning scheme is used to compensate for the process variations of center frequency. Using the high-Q bandpass amplifier in the receivers, the conventional bulky off-chip filter is not required. An experimental chip fabricated by 0.8-μm N-well double-poly-double-metal CMOS technology occupies 2.6×2.0 mm² chip area. Under a 3 V supply voltage, the measured quality factor is tunable between 2.2 and 44. When the quality factor is tuned at Q=30, the measured center frequency of the amplifier is tunable between 869-893 MHz with power gain 17 dB, noise figure 6.0 dB, output 1 dB compression point at -30 dBm, third-order input intercept point at -14 dBm, and power dissipation 78 mW     

Inversionless amplification in semiconductor nanostructures: A way to create a frequency-tunable laser of far-infrared and terahertz radiation

A scheme of a far-infrared and terahertz amplifier or laser based on a semiconductor nanostructure, consisting of a superlattice of double quantum wells of a certain design placed into a planar metal waveguide and pumped by a CO₂ laser, is suggested. The structure operation is based on the inversionless mechanism of electromagnetic field amplification, which allows passing to room-temperature operation (in the pulsed mode) and significant (by a factor of more than 1.7) variation in the output radiation frequency by simple variation in the pump intensity. A laser based on such a scheme can be a convenient and easily tunable source of infrared and terahertz radiation for both basic research and various applications.     

Amplification Effect on Rayleigh Scattering and SBS in 25 km Distributed Fiber Raman Amplifier

The amplification effect on stimulated Brillouin scattering （SBS） and Rayleigh scattering in the backward pumped G652 fibers Raman amplifier have been researched. The signal source is a tunable narrow spectral bandwidth （〈10 MHz） ECL laser and is pumped by the tunable power 1427.2 nm fiber Raman laser. The Rayleigh scattering lines are amplified by fiber Raman amplifier, and Stokes stimulated Brillouin scattering lines are amplified by fiber Raman amplifier and fiber Brillouin amplifier. The SBS lines total gain is a production of the gain of Raman and the gain of Brillouin amplifier. In experiment, the gain of SBS is about 42 dB and the saturation gain of 25 Ion G652 backward FRA is about 25 dB, so the gain of fiber Brillouin amplifier is about 17 dB.     

39-GHz optoelectronic oscillator using broad-band polymerelectrooptic modulator

An optoelectronic oscillator (OEO) producing a 39-GHz microwave signal has been demonstrated using a novel electrode-poled push-pull polymer modulator. This is the highest reported OEO operating frequency to date. Preliminary measurement of the phase noise shows performance in the range of commercial synthesizers and behavior with respect to cavity length in accordance with theory. It is also observed that dispersion penalty is a significant factor at this high frequency     

Design and Analysis of Frequency-Tunable Amplifiers using Varactor Diode Topologies

The design of frequency-tunable amplifiers is investigated and the trade-off between linearity, efficiency and tunability is revealed. Several tunable amplifiers using various varactor diode topologies as tunable devices are designed by using load-pull techniques and their performances are compared. The amplifier using anti-series distortion-free varactor stack topology achieves 38% power added efficiency and it may be tuned from 1.74 to 2.36 GHz (about 35% tunable range). The amplifier using anti-series/anti-parallel topology is tunable from 1.74 to 2.14 GHz (about 23% tunable range) and provides 42% power added efficiency. It is demonstrated that tunable amplifiers using distortion-free varactor stack topologies provide better power added efficiency than the tunable amplifiers using reverse biased varactor diodes and their linearity is similar to that of a conventional amplifier. These amplifiers may facilitate the realization of frequency agile radio frequency transceiver front-ends and may replace several parallel connected amplifiers used in conventional multimode radios.     

Design techniques for tunable transresistance-C VHF bandpassfilters

In this paper, a tunable wideband linear transresistance (R_m ) amplifier is proposed and analyzed. Using the tunable R_m amplifier, a new transresistance-capacitor (R_m-C) differentiator is designed. Considering the intrinsic capacitances of the MOS transistors as filter elements, this R_m-C configuration can he regarded as a very high frequency (VHF) bandpass biquadratic filter. The proposed biquad has a simple structure and thus occupies a small chip area and consumes little power. Moreover, higher-order VHF bandpass filters can be realized by directly cascading the biquads. Experimental results have successfully proven the capability of the proposed new filter implementation method in realizing VHF bandpass filters with the center frequency higher than 100 MHz when C_d=1 pF. The deviations of the measured center frequency f _o and quality factor Q of the fabricated bandpass filter from the simulated results are less than 8%. The deviation of the center frequency can be post-tuned by adjusting the control voltages V_CN and V_CP of the tunable R_m amplifier. With 1 pF differentiating capacitor, the center frequency of the fabricated VHF R_m-C bandpass filters can be tuned in a wide range larger than 30 MHz. The measured maximum signal level is 25 mV_rms and the dynamic range is 47 dB. The chip area is 0.05 mm² and power consumption is 5.05 mW with ±2.5 V power supply     

零偏置光电振荡器相位噪声的讨论与分析

光电振荡器(OEO)可以产生低相位噪声的微波信号。在OEO中,MZ调制器(MZM)可以偏置于正交工作点使基频信号的损耗最低,也可以工作于零偏置点从而得到倍频信号。在MZM零偏置的OEO中,利用电分频器将倍频信号分频得到基频信号,从而构建环路振荡器。本文对这2种OEO(MZM正交偏置和MZM零偏置)的相位噪声进行了理论分析。由理论分析可知,MZM零偏置OEO的相位噪声优于MZM正交偏置OEO。根据仿真结果,可以发现MZM零偏置OEO的相位噪声噪底比MZM正交偏置OEO的相位噪声低3 dB。另外,MZM零偏置OEO的振荡模式间隔并不会受到电分频器的影响。     

RF Amplitude and Phase-Noise Reduction of an Optical Link and an Opto-Electronic Oscillator

In this paper we examine the optical sources of noise that degrade high-performance microwave photonic links. In particular, we study the residual phase noise due to laser frequency fluctuations and the detector nonlinearity on microwave signals transmitted on an optical fiber, or generated in the opto-electronic oscillator (OEO). Based on experimental findings, we identify a significant reduction of the relative intensity noise of the laser if the received optical power saturates the photodiode. Furthermore, we suggest the use of a semiconductor optical amplifier in saturation as yet another means to reduce the phase noise induced by laser intensity fluctuations. We also identify the use of multiple photodetectors to reduce the influence of associated 1/f noise, which adds to the phase noise of a transmitted microwave signal, and is the ultimate limitation to the phase noise of the high-performance OEO. Reduction of noise that is due to optical interferences is also addressed.     

Injection-Locked Hybrid Optoelectronic Oscillators for Single-Mode Oscillation

We demonstrate single-mode extraction from multiple modes in a 30-GHz optoelectronic oscillator (OEO) by injecting OEO modes into an electrical oscillator. The electrical oscillator is injection-locked by one OEO mode resulting in single-mode oscillation. The single-mode oscillation frequency can be tuned by changing the electrical oscillation frequency.      

下截止频率1.3～244Hz可调带通VGA设计

采用电压控制的伪电阻结构,设计了一款具有超低频下截止频率调节功能的带通可变增益放大器(VGA),由于该结构具有可调节超大的等效电阻和反馈电容使VGA的下截止频率可以调节.提出了一种改进的甲乙类运算跨导放大器(OTA)结构,采用新颖的浮动偏置设计,在满足高压摆率的条件下,有效提高共源共栅结构的电压输出范围.将伪电阻用于OTA的共模反馈,克服了阻性共模检测结构负载效应的问题.该VGA电路采用TSMC 0.18 μm标准工艺设计和流片,测试结果表明,1.2V电源电压下,其下截止频率调节范围为1.3～ 244 Hz,增益为49.2,44.2,39.2 dB,带宽为3.4,3.9,4.4 kHz,消耗电流为3.9 μA,共模抑制比达75.2 dB.     

Low-power fully integrated and tunable CMOS RF wireless receiver for ISM band consumer applications

A 0.25-/spl mu/m single-chip CMOS single-conversion tunable low intermediate frequency (IF) receiver operated in the 902-928-MHz industrial, scientific, and medical band is proposed. A new 10.7-MHz IF section that contains a limiting amplifier and a frequency modulated/frequency-shift-key demodulator is designed. The frequency to voltage conversion gain of the demodulator is 15 mV/kHz and the dynamic range of the limiting amplifier is around 80 dB. The sensitivity of the IF section including the demodulator and limiting amplifier is -72 dBm. With on-chip tunable components in the low-power low-noise amplifier (LNA) and LC-tank voltage-controlled oscillator circuit, the receiver measures an RF gain of 15 dB at 915 MHz, a sensitivity of -80 dBm at 0.1% bit-error rate, an input referred third-order intercept point of -9 dBm, and a noise figure of 5 dB with a current consumption of 33 mA and a 2450 /spl mu/m/spl times/ 2450 /spl mu/m chip area.