Front-end Prototype Research Articles

An Integrated Solution for Suppressing WLAN Signals in UWB Receivers

A fully integrated solution for rejecting the interference caused by wireless local area network transmissions in the 4.9-5.825-GHz band for ultra-wide-band (UWB) receivers is presented. Front-end prototypes implemented in a low cost 0.35-m SiGe BiCMOS technology are used as a test vehicle to assess the effectiveness of the presented approach. The proposed blocker filtering technique mitigates the gain desensitization, third-order intermodulation distortion and second-order intermodulation distortion by as much as 9.8, 7.9, and 6 dB, respectively. At a power consumption of only 49.2 mW, the receiver conversion gain ranges from 22-19 dB while the double side-band measured at the PCB connectors ranges from 5.5-8 dB in the 3.6-7.4-GHz frequency range.

Design of Ultra-Low-Voltage RF Frontends With Complementary Current-Reused Architectures

In this paper, ultra-low-voltage circuit techniques are presented for CMOS RF frontends. By employing a complementary current-reused architecture, the RF building blocks including a low-noise amplifier (LNA) and a single-balanced down-conversion mixer can operate at a reduced supply voltage with microwatt power consumption while maintaining reasonable circuit performance at multigigahertz frequencies. Based on the MOSFET model in moderate and weak inversion, theoretical analysis and design considerations of the proposed circuit techniques are described in detail. Using a standard 0.18-mum CMOS process, prototype frontend circuits are implemented at the 5-GHz frequency band for demonstration. From the measurement results, the fully integrated LNA exhibits a gain of 9.2 dB and a noise figure of 4.5 dB at 5 GHz, while the mixer has a conversion gain of 3.2 dB and an IIP3 of -8 dBm. Operated at a supply voltage of 0.6 V, the power consumptions of the LNA and the mixer are 900 and 792 muW, respectively.

Design and practical implementation of multifrequency RF front ends using direct RF sampling

The use of direct RF sampling has been explored as a means of designing multifrequency RF front ends. Such front ends will be useful to multifrequency RF applications such as global navigation satellite system receivers that use global positioning system (GPS) L1, L2, and L5 signals and Galileo signals. The design of a practical multifrequency direct RF sampling front end is dependent on having an analog-to-digital converter whose input bandwidth accommodates the highest carrier frequency and whose maximum sampling frequency is more than twice the cumulative bandwidth about the multiple carrier signals. The principle of direct RF sampling is used to alias all frequency bands of interest onto portions of the Nyquist bandwidth that do not overlap. This paper presents a new algorithm that finds the minimum sampling frequency that avoids overlap. This design approach requires a multifrequency bandpass filter for the frequency bands of interest. A prototype front end has been designed, built, and tested. It receives a GPS coarse/acquisition code at the L1 frequency and GPS antispoofing precision code at both L1 and L2. Dual-frequency signals with received carrier-to-noise ratios in excess of 52 dB-Hz have been acquired and tracked using this system.

Design of a highly stable, high-conversion-efficiency, optical parametric chirped-pulse amplification system with good beam quality

An optical parametric chirped-pulse amplifier (OPCPA) design that provides 40% pump-to-signal conversion efficiency and over-500-mJ signal energy at 1054 nm for front-end injection into a Nd:glass amplifier chain is presented. This OPCPA system is currently being built as the prototype front end for the OMEGA EP (extended performance) laser system at the University of Rochester's Laboratory for Laser Energetics. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good output stability, and good beam quality are discussed. The dependence of OPCPA output on the pump beam's spatiotemporal shape and the relative size of seed and pump beams is described. This includes the effects of pump intensity modulation and pump-signal walk-off. The trade-off among efficiency, stability, and low output beam intensity modulation is discussed.

Teaching principles of fuzzy logic analysis using the BK-products model

The objective of the course is to give students experience using a generic front-end for relational knowledge based systems that explore the advantages of fuzzy computing with words, a natural language protocol that provides users the freedom to permit their common use of vague measurement terms in analyzing vague and partial relational knowledge structures. This course applies fuzzy logic to filter, organize, and compare verbal relational requests (queries) that relate patient symptoms with diseases. Also, an English Query Language (EQL) grammar is used to form appropriate queries that represent the BK-Product analysis being made on fuzzy relations. BK-products provide the computational structure that permits the use of natural language queries to direct a reasoning process. Students use a front-end prototype unit to parse and translate a natural language query into a BK-product meta-formula. This formula is evaluated for the degree of set membership as called for by the given product analysis.

Functional logic overloading

Functional logic overloading is a novel approach to user-defined overloading that extends Haskell's concept of type classes in significant ways. Whereas type classes are conceptually predicates on types in standard Haskell, they are type functions in our approach. Thus, we can base type inference on the evaluation of functional logic programs. Functional logic programming provides a solid theoretical foundation for type functions and, at the same time, allows for programmable overloading resolution strategies by choosing different evaluation strategies for functional logic programs. Type inference with type functions is an instance of type inference with constrained types, where the underlying constraint system is defined by a functional logic program. We have designed a variant of Haskell which supports our approach to overloading, and implemented a prototype front-end for the language.

MEDIPIX: a VLSI chip for a GaAs pixel detector for digital radiology

A GaAs pixel detector designed for digital mammography, equipped with a 36-channel single photon counting discrete read-out electronics, was tested using a test object developed for quality control purposes in mammography. Each pixel was 200×200 μm 2 large, and 200 μm deep. The choice of GaAs with respect to silicon (largely used in other applications and with a more established technique) has been made because of the much better detection efficiency at mammographic energies, combined with a very good charge collection efficiency achieved thanks to new ohmic contacts. This GaAs detector is able to perform a measurement of low-contrast details, with minimum contrast lower (nearly a factor two) than that typically achievable with standard mammographic film+screen systems in the same conditions of clinical routine. This should allow for an earlier diagnosis of breast tumour masses. Due to these encouraging results, the next step in the evolution of our imaging system based on GaAs detectors has been the development of a VLSI front-end prototype chip (MEDIPIX ) in order to cover a much larger diagnostic area. The chip reads 64×64 channels in single photon counting mode, each one 170 μm wide. Each channel contains also a test input where a signal can be simulated, injecting a known charge through a 16 f F capacitor. Fake signals have been injected via the test input measuring and equalizing minimum thresholds for all the channels. On an average, in most of the performing chips available up to now, we have found that it is possible to set a threshold as low as 1800 electrons with an RMS of 150 electrons (10 standard deviations lower than the 20 keV photon signal roughly equivalent to 4500 electrons). The detector, bump-bonded to the chip, will be tested and a ladder of detectors will be prepared to be able to scan large surface objects.

A 2D smart pixel detector for time resolved protein crystallography

A smart pixel detector is being developed for Time Resolved Crystallography for biological and material science applications. Using the Pixel Detector presented here, the Laue method will enable the study of the evolution of structural changes that occur within the protein as a function of time. The X-ray pixellated detector is assembled to the integrated circuit through a bump bonding process. Within a pixel size of 150/spl times/150 /spl mu/m/sup 2/, a low noise preamplifier-shaper, a discriminator, a 3 bit counter and the readout logic are integrated. The read out, based on the Column Architecture principle, will accept hit rates above 5/spl times/10/sup 8//cm/sup 2//s with a maximum hit rate per pixel of 1 MHz. This detector will allow time resolved Laue crystallography to be performed in a frameless operation mode, without dead time. Target specifications, architecture and preliminary results on the 8/spl times/8 front-end prototype and the column readout are presented.

The straw tracker for the SDC detector

We have developed the baseline design for a straw drift tube tracking system for the Solenoidal Detector Collaboration (SDC) detector. The system was designed to operate in the high-rate environment of the SSC. We present an overview of the tracking system and the requirements it is expected to fulfil. We describe the construction and properties of the straw drift tubes. We discuss the design of the carbon-fiber foam-laminate shell, which supports the wire tension and holds the straw in alignment. We also describe the design of the mechanical support structure, assembly procedure, and utilities. We present the performance characteristics of the prototype straw modules, read out through prototype front end electronics. The straw modules satisfy the performance criteria.

Design of front-end components for a high-power density beamline

A prototype front end for undulator beamlines to be installed on the storage ring Elettra is presented. Design criteria are briefly discussed, in particular for those components which have to withstand heavy heat load.

The Boeing Double Subharmonic Electron Injector - Performance Measurements

A two stage subharmonic injector has been installed and tested on the Boeing S band linac. The injector is designed as a prototype front end for a high voltage linac for free electron laser research.1 This accelerator will require long macropulse trains of widely spaced high current micropulses. Single micropulse output beams of 1-2 nC, 10 ps width, 1% full width energy spread and normalized emittance of ?n = s??r? = 0.01 cm-rad have been measured. The data are in good agreement with model predictions.2