A 345GHz SIS receiver for radio astronomy

A 345GHz superconductor insulator superconductor (SIS) tunnel junction receiver utilizing a full height rectangular waveguide mixer with two tuning elements, i.e. an E-plane and backshort tuner, has been constructed and installed on the Caltech Submillimeter Observatory 10m antenna on Mauna Kea, Hawaii. The receiver exhibits a best double side-band noise temperature response of 150K±20K (averaged over a 500 MHz IF bandwidth centered at 1.5GHz) at a design center frequency of 345GHz and at an ambient temperature of approximately 3.8K. Additional measurements show that the receiver has an excellent response at selected points within an RF input range of 280 to 363GHz.     

A 691 GHz sis receiver for radio astronomy

We report the development of a low noise heterodyne receiver optimized for astronomical observations in the 650 GHz atmospheric window, and specifically for the CO(J=6→5) line at 691.5 GHz. The system is based on an open structure SIS heterodyne mixer pumped by a continuously tunable solid state oscillator. A niobium SIS junction double array is placed at the end of an integrated V-Antenna. For broad band impedance matching a combination of microstrip impedance transformer and radial stub was used. Receiver noise temperatures of 550 K DSB at 684 GHz were achieved at a 1.8 K physical temperature. The performance improved substantially when decreasing the temperature from 4.2 to 1.8 K. Comparison of model calculations and Fourier transform direct detection measurements of the tuning structure implies that this effect is likely due to the coincidence of operational frequency and the gap frequency of the niobium.     

A 110 GHz SIS receiver for radio astronomy

A 110 GHz superconductor insulator superconductor (SIS) tunnel junction receiver has been developed and used in regular astronomical observations on the 4m radio telescope at the Department of Astrophysics, Nagoya University. The SIS junction consists of a sandwich structure of Nb/AlOx/Nb, and is cooled to 4.2K with a closed cycle He-gas refrigerator. The receiver exhibits a best double side band noise temperature of 23±2 K at 110GHz. Additional measurements at 98–115 GHz indicate that the receiver has a good response over this input frequency range.     

Efficient receiver structure for GSM mobile radio

The paper describes a receiver structure for the digital GSM mobile radio which is suitable for implementation using a DSP processor. The simulation results show that proposed simplifications have minor influence on the receiver performance and drastically reduce its computational complexity.     

A reduced-state Viterbi receiver with prefiltering for the mobile radio channel

This paper presents a possible receiver structure for high bit rate transmission on the mobile radio channel. The receiver is based on a reduced-state Viterbi algorithm combined with decision feedback, known as Decision Feedback Sequence Estimation. A tdma concept using a training sequence for channel estimation and continuous phase modulation is assumed. For channel estimation a least squares method is studied, and an adaptive prefilter is used to improve the receiver performance on minimum phase channels. Estimates on the computational complexity of the receiver and simulation results showing the performance on a typical urban (tu) channel are presented. The results show that the prefilter improves the performance of the receiver significantly when a small number of states is used in the Viterbi algorithm. However, the computational complexity for 2 Mbit/s continuous transmission is very high.     

Imbalance-compensated direct down conversion receiver for UMTS base stations

In this work, a new method for the estimation and the compensation of in-phase quadrature-imbalances in direct down conversion receivers is presented. The considerations are based on a receiver structure that is developed for the simultaneous down conversion of up to four neighboring carriers in universal mobile telecommunications system base stations. The image suppression of the system must achieve at least 60 dB. This requirement is not fulfilled by the analogue part and hence, an error estimation and compensation in the digital domain is necessary. In laboratory measurements using a wideband code-division multiple-access signal, the image suppression of the complete set-up including the analogue parts could be improved by 34 dB.     

Combined diversity sequence estimation receiver for widebanddigital mobile radio

An investigation is presented into the performance of a novel type of sequence estimation equalisation receiver. The receiver incorporates space diversity to further enhance the signal reception in multipath fading environments. It is shown that the receiver complexity is reduced by ~90% with virtually no performance loss compared to that of the MLSE     

An adaptive MLSE receiver for TDMA digital mobile radio

The authors present a simulation study of an adaptive receiver, based on the concept of maximum-likelihood sequence estimation (MLSE), which compensates for the heavy selective distortions caused by multipath propagation. The receiver includes a matched filter and a modified Viterbi processor and is suitable for implementation in a digital form. It operates adaptively, in a training mode at the beginning of each burst, as well as in a tracking mode during message detection. This makes the receiver robust both to fast Doppler shifts and to a large frequency offset. Simulation results are presented which show the performance in different multipath environments, with echo delay in excess of 20 μs and vehicle speed up to 250 km/h     

软件无线电跳频电台接收机射频前端设计

基于软件无线电的基本要求和发展趋势,提出了一种应用在软件无线电跳频电台中接收机射频前端电路结构,分析了接收机射频前端的总体设计方案,包括前端各部分增益的分配、动态范围的分配、噪声系数及灵敏度的计算,讨论了对器件选择的考虑.实际测试结果表明,该射频前端性能指标满足设计要求.     

Optimum positioning of base stations for cellular radio networks

Finding optimum base station locations for a cellular radio network is considered as a mathematical optimization problem. Dependent on the channel assignment policy, the minimization of interferences or the number of blocked channels, respectively, may be more favourable. In this paper, a variety of according analytical optimization problems are introduced. Each is formalized as an integer linear program, and in most cases optimum solutions can be given. Whenever by the complexity of the problem an exact solution is out of reach, simulated annealing is used as an approximate optimization technique. The performance of the different approaches is compared by extensive numerical tests. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improved four-channel direct-conversion SiGe receiver IC for UMTS base stations

This work presents the design and measurement results of an improved four-channel, direct down conversion receiver (DCR) for the application in universal mobile telecommunications system base stations. The whole analog receiver functionality including low noise amplifier, variable gain amplifier, local oscillator frequency divider, in-phase and quadrature DCR mixers and seventh-order active lowpass filter is integrated using Atmel's 50-GHz f/sub t/, 50-GHz f/sub max/ SiGe foundry technology (Atmel, 1998). Important cascaded design parameters of the fully ESD-protected device are a noise figure 1.5 to 2 dB; IIP3 (third-order intercept point) -20.3 to -15.8 dBm and a voltage gain of 51 to 57 dB into a 1000-/spl Omega/ /spl par/ 2.5-pF differential load [analog to digital converter].     

A 0.7-7 GHz wideband reconfigurable receiver RF front-end in CMOS

In this paper,a 0.7-7 GHz wideband RF receiver front-end SoC is designed using the CMOS process.The front-end is composed of two main blocks:a single-ended wideband low noise amplifier (LNA) and an inphase/quadrature (I/Q) voltage-driven passive mixer with IF amplifiers.Based on a self-biased resistive negative feedback topology,the LNA adopts shunt-peaking inductors and a gate inductor to boost the bandwidth.The passive down-conversion mixer includes two parts:passive switches and IF amplifiers.The measurement results show that the front-end works well at different LO frequencies,and this chip is reconfigurable among 0.7 to 7 GHz by tuning the LO frequency.The measured results under 2.5-GHz LO frequency show that the front-end SoC achieves a maximum conversion gain of 26 dB,a minimum noise figure (NF) of 3.2 dB,with an IF bandwidth of greater than 500 MHz.The chip area is 1.67 × 1.08 mm2.     

A suboptimal receiver for joint spatial-temporal filtering andmultiuser detection in mobile radio communications

This paper proposes a suboptimal receiver for joint spatial-temporal filtering and multiuser detection in mobile radio communications using single carrier signaling. The proposed receiver is a reasonable approximation of the maximum likelihood (ML) based optimal receiver described in the present paper. A cascaded connection of an adaptive array antenna and an ML multiuser sequence estimator is the basis of the proposed receiver. The major advantages of the proposed receiver over conventional adaptive array antennas are: (1) delayed path components of desired signals can be effectively combined; (2) interference signals exceeding the degree of freedom; and (3) those having the same incident angle as that of desired path components can both be suppressed. The proposed receiver does not require prohibitively large computational complexity. Results of computer simulations presented in this paper show that the proposed receiver exhibits excellent performance even in severe multipath fading environments     

Si bipolar chip set for 10-Gb/s optical receiver

Three Si bipolar ICs, a preamplifier, a gain-controllable amplifier, and a decision circuit, have been developed for 10-Gb/s optical receivers. A dual-feedback configuration with a phase adjustment capacitor makes it possible to increase the preamplifier bandwidth up to 11.2 GHz, while still retaining flat frequency response. The gain-controllable amplifier, which utilizes a current-dividing amplifier stage, has an 11.4-GHz bandwidth with 20-dB gain variation. A master-slave D-type flip-flop is also operated as the decision circuit at 10 Gb/s. On-chip coplanar lines were applied to minimize the electrical reflection between the ICs     

A high sensitivity and wide dynamic range zero-IF RF receiver for cognitive radio application

This paper presents an RF receiver of zero-Intermediate Frequency (IF) architecture for Cognitive Radio (CR) communication systems. Zero-IF architecture reduce the image reject filter and IF filter, so it is excellent in low cost, compact volume, and low power dissipation. The receiver employs three digital attenuator and a high gain, high linearity low noise amplifier to achieve wide dynamic range of 70 dB and high receiving sensitivity of −81 dBm. A fully balanced I/Q demodulator and a differential Local Oscillator (LO) chips are used to minimize the negative effects caused by second-order distortion and LO leakage. In order to select an 8 MHz-channel from 14 continuous ones located in UHF band (694–806 MHz) accurately, approach of channel selectivity circuits is proposed. The RF receiver has been designed, fabricated, and test. The measured result shows that the noise figure is 3.4 dB, and the error vector magnitude is 7.5% when the input power is −81 dBm.     

Enhanced efficiency and frequency assignment by optimizing the base stations location in a mobile radio network

Most mobile radio networks have been planned based on the classical cellular concept. However, alternative planning strategies that lead to more efficient network configurations are necessary due to the fact that the traffic density is generally far from constant throughout the service area, making necessary the relocation of base stations inside the traffic hotspots. If the traffic is characterized in a discrete way, the optimization of base stations location resembles vector quantization, a well-known problem in signal processing. In this paper, we use this analogy to propose a mobile radio network planning algorithm. Simulation results show that higher trunking efficiency as well as improved frequency assignment can be obtained if an existing mobile radio network is redesigned using the presented strategy. Raúl Chávez-Santiago was born in Oaxaca City, Mexico. He obtained the B.Sc. degree in communications and electronics engineering in 1997 from the School of Mechanical and Electrical Engineering (ESIME-IPN), and the M.Sc. degree in electrical engineering in 2001 from the Center of Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN) in Mexico City. He has professional experience as Computer Networking Engineer, and Research and Teaching Assistant. Currently, he is completing his studies toward the Ph.D. degree at Ben-Gurion University (BGU) of the Negev, Israel. In 2002, he received the URSI Young Scientist Award. His main research interests are the optimal planning of radio communication networks, the electromagnetic compatibility of terrestrial and satellite radio systems, and the efficient use of the radio spectrum. He is an IEEE and IEICE student member, and a URSI radio scientist. Avi Raymond was born in Yavne, Israel. He received the B.Sc. and M.Sc. degrees in electrical engineering from Ben-Gurion University (BGU) of the Negev in 2000 and 2005, respectively. He worked for two years in a communication company in the field of Telephony and Broadband Services. He also worked as a Research Assistant in the communications laboratory at BGU. He currently works at Elta Electronic Industries Ltd. as System Engineer and pursues studies toward a second M.Sc. degree in systems engineering at the Technion Institute of Technology, Haifa, Israel. His research interests are the optimization algorithms for frequency assignment in cellular networks. Vladimir Lyandres was born in 1944, in Vologda, Russia. He received the M.Sc. degree in communications engineering in 1966 and the Ph.D. degree in communications theory in 1972 from the State University of Telecommunications (SUT), Saint Petersburg, Russia. He was with SUT until 1990 holding a position of Senior Scientific Associate and working on research and development of digital transmission systems, modeling of radio communication channels and algorithms of frequency planning for broadcasting and cellular systems. Since 1991 he holds a position of Researcher at the communications laboratory and Professor at the Department of Electrical and Computer Engineering, Ben-Gurion University (BGU) of the Negev, Israel. His research interests include synthesis of Markov models, combinatorial optimization, and adaptive power loading. He is a senior member of IEEE and member of IEICE.     

Optimal base stations location and configuration for cellular mobile networks

In this paper, we study the problem of base stations location and configuration. Antenna configuration includes number of antennas installed at the base station, the azimuth of each base station, the tilt, height, and transmitted power for each antenna for cellular mobile networks. Towards this end, a mathematical model is formulated using integer programming (IP).The objective of the model is to minimize the cost of the network. The model guarantees that each demand point is covered. A demand point represents a cluster of uniformly distributed multiple users. In addition, the signal-to-interference-plus-noise ratio at each demand point is set at a given threshold value. A none-line-of-site situation is considered while calculating the path loss using COST-231-Walfisch-Ikegami propagation model. To illustrate the capability of the formulated IP model, we use a discretized map of some area with demand points. The IP model is solved using a commercial software, LINGO 12. Possible future research directions are stated in the conclusion.

     

RF CMOS Varactors for 2 GHz Applications

CMOS varactors are important components for the integration of tunable RF filters and VCOs. This paper presents a performance evaluation and comparison of three different types of CMOS varactors based on measurements. The tested varactor types are: (i) p⁺-to-n-well junction, (ii) standard mode nMOS, and (iii) accumulation mode nMOS. The performance of each varactor type with respect to capacitance ratio and quality factor Q is evaluated at 2 GHz. Further, it is shown how these varactor types must be configured in LC-tank circuits for optimum performance. Finally, the three varactor types are compared and it is concluded that the Standard Mode nMOS type seems to the best choice for RF applications.     

49 mW 5 Gbit/s CMOS receiver for 60 GHz impulse radio

A 5 Gbit/s CMOS receiver for 60 GHz impulse radio is realised. It contains a fully differential envelope detector for differential inputs, a current mode offset canceller for robustness against PVT variations, and a high-speed comparator with hysteresis for noise immunity. The receiver is fabricated using a 90 nm CMOS process with a size of 950 x 750 spl mu/m. The total power consumption of the receiver is 49 mW at 5 Gbit/s.     

A low-noise SIS receiver measured from 480 GHz to 650 GHz using Nb junctions with integrated RF tuning circuits

A heterodyne receiver using an SIS waveguide mixer with two mechanical tuners has been characterized from 480 GHz to 650 GHz. The mixer uses either a single 0.5 × 0.5 µm² Nb/AlO_x/Nb SIS tunnel junction or a series array of two 1 µm² Nb tunnel junctions. These junctions have a high current density, in the range 8 – 13 kA/cm². Superconductive RF circuits are employed to tune the junction capacitance. DSB receiver noise temperatures as low as 200 ± 17 K at 540 GHz, 271 K ± 22 K at 572 GHz and 362 ± 33 K at 626 GHz have been obtained with the single SIS junctions. The series arrays gave DSB receiver noise temperatures as low as 328 ± 26 K at 490 GHz and 336 ± 25 K at 545 GHz. A comparison of the performances of series arrays and single junctions is presented. In addition, negative differential resistance has been observed in the DC I–V curve near 490, 545 and 570 GHz. Correlations between the frequencies for minimum noise temperature, negative differential resistance, and tuning circuit resonances are found. A detailed model to calculate the properties of the tuning circuits is discussed, and the junction capacitance as well as the London penetration depth of niobium are determined by fitting the model to the measured circuit resonances.