An improved optical heterodyne DPSK receiver to combat laser phasenoise

Presents a method to improve the performance of a standard delay-and-multiply type optical heterodyne binary-DPSK receiver. This is achieved by using separate “weighting” bandpass filters to shape the phase noise corrupted direct and delayed signals before combining and decoding as for the standard receiver. The optimization of a filter parameter allows this “weighted” receiver to exhibit a lower phase noise sensitivity than the standard receiver. The most significant achievement of the weighted receiver is the ability to tradeoff excess signal power to obtain low bit error rates when large amounts of phase noise are present     

An SIS waveguide heterodyne receiver for 600 HGz-635 GHz

A waveguide SIS heterodyne receiver using a Nb/AlO_X/Nb junction has been built for astronomical observations of molecular transitions in the frequency range 600 GHz - 635 GHz, and has been successfully used at the Caltech Submillimeter Observatory (CSO). We report double sideband (DSB) receiver noise temperatures as low as 245 K at 600 GHz -610 GHz, and near 300 K over the rest of the bandwidth. These results confirm that SIS quasiparticle mixers work well at submillimeter-wave frequencies corresponding to photon energies of at least 90% of the superconductor energy gap. In addition, we have systematically investigated the effect on the receiver performance of the overlap between first-order and second-order photon steps of opposite sign at these frequencies. The receiver noise increases by as much as 40% in the region of overlap. We infer potential limitations for operating submillimeter-wave Nb/AlO_x/Nb mixers.     

Optical heterodyne receiver providing random channel selection

The authors describe a digitally tuned optical heterodyne receiver which can randomly access the channels of an FDM optical communication system. The receiver can identify missing channels, and is insensitive to variation of the LO laser frequency relative to the tuning current.<>     

Low-noise SIS heterodyne receiver at 230 GHz

A 230 GHz laboratory receiver has been built using a superconductor-insulator-superconductor (SIS) junction as the mixing element. The junction is mounted in 4:1 reduced-height waveguide, terminated at one end with a circular adjustable backshort. Recent results indicate a receiver noise temperature of TR ? 120 K (DSB).     

GaInAs/GaInAsP multiple-quantum-well integrated heterodyne receiver

Describes the fabrication and performance of the first integrated heterodyne receiver capable of actual heterodyne data reception. Integrating a continuously tunable 1.5 mu m MQW-DBR laser with a single-mode directional coupler/switch and zero-bias MQW waveguide photodetectors, the authors have achieved error-free reception of FSK-modulated pseudorandom digital code at 105 Mbit/s.<>     

An adaptive wideband antenna array receiver of low complexity

A low complexity wideband antenna array receiver is proposed for wideband wireless communication systems. With the proposed algorithm, the array beampattern remains almost the same within a wide frequency range of interest. In comparison to the conventional algorithm, the new algorithm offers a faster convergence rate with a lower computational complexity. Simulation results are presented to demonstrate the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd.     

First heterodyne receiver frontend module including a polarizationdiversity receiver OEIC on InP

For the first time a packaged polarization diversity coherent receiver OEIC including detector units (photodetectors, JFET, load resistor) has been fabricated with the following data: waveguide loss 2 dB, 3 dB balance within 0.4 dB, polarization extinction >30 dB (TM) and >17 dB (TE), 3 dB cutoff frequency of 0.9 GHz, common mode rejection ratio 30 dB     

基于点阵照明的APD阵列外差激光雷达外差效率的提高

当前研制的快速成像无扫描激光雷达系统由于激光器功率和信号损耗的限制,遇到了无法增大作用距离的瓶颈。结合光外差体制和APD阵列探测器设计的APD阵列外差探测激光雷达系统可以有效地解决这个问题。鉴于光学系统的外差效率能够直接影响外差激光雷达的性能,因此照明方式的设计是该套激光雷达系统的一个关键。经过分析,传统的直接扩束照明模式下系统的平均外差效率仅为10-5量级,远无法打到使用要求;因此提出了采用改进的点阵照明,并采用在阵列探测器前置微透镜阵列实现匹配接收的方式来解决这一问题。计算结果显示,经过优化后的点阵照明模式下的系统外差效率可达0.82,进而证明了采用点阵照明设计的APD阵列外差激光雷达系统的性能可以达到实用要求,为进一步开展APD阵列外差激光雷达的研究工作奠定了理论基础。     

An experimental four-element adaptive array

The experimental pattern behavior of a four-element adaptive array based on a steepest-descent feedback algorithm is described. The array uses four multiturn loop elements on an aircraft fuselage mock-up. Operational patterns have been measured as a function of various parameters: frequency, element placement, desired signal and interference angles of arrival, signal powers, etc. Typical patterns are presented and the performance characteristics of the array are described.     

Retrodirective array using the heterodyne technique

A retrodirective array using a single microwave mixer to accomplish conjugate phase shift in each element is described. Reradiated patterns were measured for a four-element array to substantiate the predicted performance. This array has an advantage over the Van Atta array in that the elements are not restricted to being located on a plane surface. It is more efficient than the previously used method of employing two mixers to provide conjugate phase shift because of the reduction in converison loss and LO (local oscillator) power.     

Microwave photonic direct-sequence transmitter and heterodyne correlation receiver

This paper proposes and demonstrates a new architecture for the transmission, heterodyne reception, and correlation of direct-sequence (DS) signals encoded onto an optical carrier. The approach is practical for pseudo-noise in-modulated laser radar and free-space optical-code-division multiple-access communications. Although the local oscillator is free running, we show that the received signal is free from laser phase noise. Furthermore, by applying DS coding to both the transmitted signal and the local oscillator, the delay required for correlation can be realized via a combination of electrical and optical means.     

Polarisation-insensitive optical heterodyne receiver for coherent FSK communications

An optical FSK heterodyne communications receiver is proposed using a polarisation diversity technique which has a reduced level of complexity. The proposed receiver is constructed and tested at 100kbit/s and shown to have a maximum fluctuation in sensitivity of 17% over conditions of originally complete polarisation fading.     

The Mott diode as a heterodyne receiver element

This paper considers a novel doping profile for Schottky barrier mixer diodes called the Mott barrier. The structure consists of a metal-semiconductor junction in which the semiconductor's epitaxial layer is very lightly doped and thin enough so that it remains depleted even under substantial forward bias. It has been proposed that Mott barrier diodes will generate less noise and have lower series resistance-junction capacitance products than standard Schottky diodes, thus increasing the sensitivity and cut-off frequency of heterodyne receivers. In this paper, the band structure and electron transport properties of the Mott diode are evaluated. This analysis shows that the Mott diode actually will have a large series resistance-junction capacitance product and excessive hot electron noise, making it a poor candidate for high-frequency applications. Experimental results are presented which substantiate these conclusions.     

Phase-noise-insensitive coherent optical heterodyne CPFSK receiver with limiter-discriminator detector

A coherent optical heterodyne CPFSK receiver with a limiter-discriminator (LD) detector, which cannot be degraded by quantum phase noise of lasers when the frequency deviation ratio h is equal to 1, is proposed. The receiver can give the same bit error rate as the ideal digital DPSK system. In addition, 1/2 exp (-SNR) can be considered as the upper bound of the minimum error rate of the CPFSK-LD detector.<>     

Optical heterodyne receiver for selecting densely frequencydivision multiplexed signals

An optical heterodyne receiver that can select any channel out of 2.5 Gbit/s frequency division multiplexed (FDM) signals with spacing as narrow as 5 GHz has been developed. Sharp filtering characteristics of the heterodyne receiver at the intermediate frequency stage enable FDM signals with such narrow channel spacing to be demultiplexed     

A 100-GHz-band heterodyne sis receiver for the trao telescope

A 100-GHz-band Superconductor-Insulator-Superconductor (SIS) receiver has been developed for radio astronomy. The mixer used in this receiver has no mechanical tuning elements, such as a backshort or an E-plane tuner. The SIS junction consists of an array of four Nb/Al-AIOx/Nb junctions in series. The quasi-optic system for this receiver has been designed by frequency-independent matching method. The average DSB receiver noise temperature measured in the frequency range from 85 to 115 GHz is 40 K. The receiver is being successfully operated at the Taeduk Radio Astronomy Observatory in Korea.     

Stabilisation of heterodyne receiver sensitivity with automatic polarisation control system

A low-insertion-loss automatic optical fibre polarisation control system with low driving voltage and low monitoring power has achieved stabilisation of the receiver sensitivity within the fluctuation range of less than 0.4 dB in an optical FSK heterodyne 280 Mbit/s, 141 km transmission experiment.     

A dual-detector optical heterodyne receiver for local oscillator noise suppression

The performance of a dual-detector optical heterodyne receiver was analyzed and compared with the performance of a conventional single-detector heterodyne receiver. The dual-detector receiver is found to offer two main advantages over the single-detector receiver-1) increased performance in the presence of local oscillator intensity fluctuations that might severely degrade single-detector receiver performance, and 2) decreased local oscillator power requirements. These two advantages are particularly important in a communication system which uses semiconductor laser diodes as local oscillators. Such lasers suffer from intrinsic wide-band intensity fluctuations and can also impose strict power constraints on receiver design. Based on the analysis, suggestions for the optimal design of a dual-detector heterodyne receiver are made. Also, several experiments were performed to demonstrate the improved performance of the dual-detector receiver-both for unguided- and guided-wave receivers.     

Balanced operation of a GaInAs/GaInAsP multiple-quantum-wellintegrated heterodyne receiver

The balanced operation of a multiple-quantum-well balanced heterodyne receiver photonic integrated circuit (PIC) is described. Using only SMA-connected 50 Ω commercial electronics, a free-space beam sensitivity of -42.3 dBm at 108 Mb/s and -39.7 dBm at 200 Mb/s for NRZ FSK (frequency-shift keying) reception has been achieved. This represents a 14 dB improvement over any previous heterodyne receiver PIC sensitivity. In addition to providing the multichannel benefits of heterodyne reception, this is also the highest sensitivity yet reported for any OEIC (optoelectronic integrated circuit) receiver     

Performance analysis of a noncoherently combined large apertureoptical heterodyne receiver

The performance of a noncoherently combined, multiple-mirror heterodyne receiver is analyzed. In the absence of atmospheric turbulence, the performance of the noncoherently combined receiver is shown to be inferior to that of a monolithic, diffraction-limited receiver with equivalent aperture area. when atmospheric turbulence is taken into consideration, however, the efficiency of a monolithic aperture heterodyne receiver, is limited by the phase coherence length of the atmosphere, and generally does not improve with increasing aperture size. In contrast, the performance of a noncoherently combined system improves with an increasing number of receivers. Consequently, given a fixed collecting area, the noncoherently combined system can offer a superior performance. The performance of the noncoherently combined heterodyne receiver is studied by analyzing the combining loss of the receiver SNR (signal-to-noise ratio). It is shown that, given a constant collecting area, the performance of the combined receiver is optimized when the diameter of each of the individual receivers is on the order of the phase coherence length r₀ of the atmospheric turbulence