A broad-band low-noise SIS receiver for submillimeter astronomy

A quasi-optical heterodyne receiver using a Pb-alloy superconductor-insulator-superconductor (SIS) tunnel junction as the detector and a planar logarithmic spiral antenna for the RF coupling is described, and its performance is compared with the predicted performance of a theoretical model. Noise measurements were made in the laboratory at frequencies between 115 GHz and 761 GHz, yielding double-sideband noise temperatures ranging from 33 K to 1100 K. The receiver has also been used for astronomical spectroscopy on the Caltech Submillimeter Observatory (Mauna Kea, Hawaii) at 115, 230, 345, and 492 GHz     

A low noise receiver for millimeter and submillimeter wavelengths

A broadband, low noise heterodyne receiver, suitable for astronomical use, has been built using a Pb alloy superconducting tunnel junction (SIS). The RF coupling is quasioptical via a bowtie antenna on a quartz lens and is accomplished without any tuning elements. In this preliminary version the double sideband receiver noise temperature rises from 205 K at 116 GHz to 375 K at 349 Ghz, and to 815 K at 466 GHz. This is the most versatile and sensitive receiver yet reported for sub-mm wavelengths.     

Low noise submillimeter SIS receiver with niobium nitride quasiparticle tunnel junctions

We have developed and tested a submillimeter waveguide SIS mixer with NbN-MgO-NbN quasiparticle tunnel junctions. The two junction array is integrated in a full NbN printed circuit. The NbN film critical temperature is 15 K and the junction gap voltage is 5 mV. The size of the junctions is 1.4 × 1.4 µm and Josephson critical current density is about 1.5 KA/cm² resulting in junction R_NωC product about 40. The inductive tuning circuit in NbN is integrated with each junction in two junction array. A single non contacting backshort was tuned at each frequency in the mixer block. At 306 GHz the minimum DSB receiver noise temperature is as low as 230 K. The sources of the receiver noise and of the limits of the NbN SIS submillimeter mixer improvement are discussed.     

镜像综合孔径辐射计接收机的单双边带选择

与综合孔径复相关接收不同,镜像综合孔径辐射计只需测量同相相关输出,为此镜像综合孔径辐射计与综合孔径辐射计的接收机结构也有明显区别,而镜像干扰分析对于辐射计接收机结构及单双边带选择尤为重要。为了分析镜像综合孔径辐射计接收机结构及单双边带选择,本文首先介绍了镜像综合孔径辐射计的接收机结构,然后从镜像综合孔径接收信号角度出发推导了镜像综合孔径辐射计接收机结构分别选择单、双边带工作模式下接收机通道相关函数表达式,分析其是否会产生镜频干扰。理论推导发现,镜像综合孔径辐射计在单、双边带工作模式下,都不会产生镜像干扰, 唯一的区别在于双边带重建亮温的幅度是单边带的2倍。这是与综合孔径辐射计接收机结构在下变频、再I/Q解调且选择双边带模式时会产生镜像干扰最大的不同。最后,通过双点源和展源仿真验证了理论的正确性。研究结果可为实际应用中镜像综合孔径辐射计接收机单双边带选择提供参考。     

Digital single-sideband modulators

A new derivation of Darlington's digital s.s.b./f.d.m. modulator1 implementation is presented, giving additional structural insight.     

Digital single-sideband mixer

A single-sideband (SSB) frequency converter using only exclusive-or logic gates and no reactive or frequency-selective analog circuit elements takes square-wave inputs at two arbitrary frequencies f1and f2and generates an output waveform whose principal spectral component is at either f1+f2or f1-f2, selectably. A pair of outputs is generated in phase quadrature.     

一种单边带QPSK调制解调方法

提出了一种单边带QPSK调制解调的方法.该方法在调制端通过适当的滤波器滤去QPSK调制信号的一个边带,在解调端通过希尔伯特变换构造出频谱上的共轭对称量实现解调,并通过使用对原始信号进行密勒码编码的方法减弱了希尔伯特变换在低频处的不理想对系统性能的影响.给出了详细的理论推导,并通过计算机仿真实验结果证明,提出的单边带QPSK调制解调方法在AWGN信道上的误码性能比传统的双边带QPSK调制解调方法差3dB,但能够节省一半传输带宽.因此,它是一种很有实际应用价值的调制解调算法,尤其适用于带宽受限的数据传输系统.     

A new single-sideband digital mixer

A single-sideband digital mixer using logic exclusive-OR gates, J-K flip-flops, and one-shot multivibrators, but not containing any reactive filters accepts square inputs at two arbitrary frequencies f1and f2and generates a pair of phase-quadrature waves with fundamental frequency at either f1+ f2or f1- f2.     

Integrated-optical single-sideband modulator and phase shifter

A scheme of spatially weighted coupling between two waveguide modes is proposed in which the weights form an electrooptically induced periodic coupling structure that can be moved at variable speeds forward or backward along the guide. The device can operate as an optical phase shifter with unlimited phase range, as a single-sideband amplitude modulator or frequency shifter, or as a polarization transformer.     

Impact of nonlinear distortion in radio over fiber systems with single-sideband and tandem single-sideband subcarrier modulations

In radio over fiber (RoF) systems, two subcarrier modulations (SCMs), i.e., single-sideband (SSB) and tandem single-sideband (TSSB), have been widely used. Both SSB and TSSB SCMs can be obtained using optical Mach-Zehnder modulators. In this paper, the authors theoretically investigate the impact of harmonic distortion and intermodulation distortion in RoF systems for one wavelength carrying two radio frequency (RF) signals with either SSB or TSSB SCM. It is found that nonlinear distortion can be reduced when the frequency difference of two RF signals is /spl sim/ 1 GHz compared with /spl sim/ 2 GHz and higher for both TSSB and SSB SCMs, particularly for large modulation indexes. When the frequency difference of RF signals is /spl sim/ 2 GHz and beyond, either a small modulation index or a medium modulation index combined with a minimum RF of 6 GHz must be used, and a large modulation index cannot be used due to serious nonlinear distortion. Comparison of SSB and TSSB SCMs with uniform distribution of optical signal subcarriers in a dense wavelength-division-multiplexing RoF system with channel spacing of 12.5 GHz shows by simulation that SSB SCM is better (worse) than TSSB SCM for small (large) modulation indexes.     

Integrated-optical single-sideband Bragg modulator with taperedwaveguides

Surface acoustic wave (SAW) Bragg modulators yield high optical and electrical bandwidth. The Bragg modulator consists of tapered monomode waveguides and the SAW field in between. Overall suppression of unwanted frequencies of better than 30 dB (TM) and 20 dB(TE) are obtained     

对LFM脉压雷达的移频压制干扰技术研究

分析了移频干扰对线性调频脉冲压缩雷达的干扰效果,提出移频干扰不能作为假目标欺骗干扰应用的观点,其产生的假目标由于不满足目标运动特性,易被雷达识别.研究了移频压制干扰在一定移频条件下实现对线性调频脉压雷达的压制干扰效果,可获得雷达部分压缩增益,因此相对噪声压制干扰,可明显节约干扰功率.仿真验证了结论的正确性.     

Multichannel single-sideband SCM/DWDM transmission systems

To understand the transmission limitation of multiple narrow single-sideband subcarrier-multiplexed (SSB/SCM) signals, this paper first presents a closed-form analysis to predict Mach-Zehnder intensity modulator-induced composite triple beat (CTB), and linear-fiber-dispersion-induced composite second-order (CSO) and CTB distortions. To combine SSB/SCM with dense-wavelength-division-multiplexing (DWDM) systems, analytical and numerical tools, which are not constrained by any wavelength spacing and modulation frequencies, are used to analyze cross-phase modulation-induced crosstalk. All the analytical and numerical results are verified by computer simulations. Several multichannel SSB/SCM/DWDM systems with transport capacities of 10 or 20 Gb/s per wavelength, with a wavelength spacing of 25, 50, and 100 GHz, are also studied in this paper to understand the fundamental transmission limitations.     

Optical single-sideband suppressed-carrier modulator for wide-bandsignal processing

We develop and demonstrate a technique for implementing a wide-band optical single-sideband suppressed-carrier modulator. The technique relies on a dual-electrode traveling wave modulator for sideband suppression and a Sagnac fiber-loop interferometer for carrier suppression. The implementation uses all commercially available components and demonstrates >40 dB optical carrier suppression, and as much as 60 dB unwanted signal sideband rejection across a 6-20 GHz microwave frequency range. The modulator is used to demonstrate broad-band spectral shifting- and inversion across the 3-18 GHz frequency range     

Dual single-sideband modulation for wideband data transmission

A new modulation method for data transmission is described for use on groupband communication channels (60?108 kHz), which is compatible with the existing group- and supergroup-reference pilots. Dual single-sideband modulation permits a basic transmission rate of 48 kbit/s, which can be extended to 72 or 96 kbit/s by means of special multilevel coding.     

Simple design procedure for single-sideband crystal filters

The letter gives simple, direct formulas for the design single-sideband crystal `ladder? filters. The resulting designs are easily realisable by using only crystals and capacitors.     

单边带辅助BOC信号跟踪方法设计

二进制偏移载波调制是现代化后的卫星导航信号的主要特征,可以为用户提供更高性能的服务,然而其相关函数的多侧峰特点也在跟踪过程中引入了误锁的风险。针对二进制偏移载波BOC(1,1)信号,提出并设计了一种利用单边带处理方法的无模糊特点来辅助BOC直接跟踪的方法,从而达到既消除误锁风险又可进行高精确度信号跟踪的双重目的;进而对该方法的实现结构进行简化,并针对实现结构的不足做出相应改进。经测试,该方法可以实现对信号的无模糊跟踪并达到了较高精确度,证明该方法相关设计的有效性和实用性。     

Design of Lange-couplers and single-sideband mixers usingmicromachining techniques

This paper reports on the design and performance of micromachined Lange-couplers and single-sideband mixers (SSB) on thin dielectric membranes at Ku-band. The micromachined Lange-coupler results in a 3.6±0.8 dB coupling bandwidth from 6.5 to 20 GHz. The Lange-coupler and an interdigital filter are used in a 17-GHz SSB. The SSB mixer requires 1-2 mW of local oscillator (LO) power without dc bias and achieves a 30 dB upper-sideband (USB) image rejection for an IF frequency of 1 GHz and above. The micromachined membrane technology can be easily scaled to millimeter-wave monolithic microwave integrated circuits (MMIC's) to meet the low-cost requirements in automotive or portable communication systems