Are you T.C. Banwell?

Claim your profile

Publications (17)30.94 Total impact

  • T.C. Banwell, W.E. Stephens
    [Show abstract] [Hide abstract]
    ABSTRACT: EMI/EMC is a dominant problem encountered in high bit-rate (>100 Mb/s) transmission over unshielded twisted-pair cable (UTP) which leads to a novel set of line-code dependent tradeoffs affecting transceiver and cable plant complexity. To understand the tradeoffs, the authors examined the factors affecting RF emissions and susceptibility in both trellis-configured cable plant models and installed cable plant. An analytical model is presented that describes mode conversion by discontinuities in multi-pair UTP cable plant. Termination of the three dominant propagating modes produces consistently lower radiated emissions than other standard cable termination procedures. Cable plant parameters which predict good transmission do not assure satisfactory EMI performance. Radiated emissions from the trellis model occur in broad bands at 43, 53, 60, 70, and 80 MHz, and show a positive correlation with the transmit signal spectrum. For a given transmit level at 155 Mb/s, the emissions with MLT3 and BPR1 were 8-13 dB (10 dB typ) and 4-20 dB (13 dB typ) below NRZ levels, respectively. The authors also compared the performance of NRZ, MLT3, BPR1, and BPR4 line codes in an experimental 155 Mb/s link with 100 m of UTP5 by measuring the BER sensitivity to both injected noise and pseudo-random data sequence length. When the measured receiver penalty associated with three levels is included, MLT3, BPR1, and BPR4 offer 5-15 dB better performance over NRZ at 155 Mb/s, although implementation complexity is greater
    IEEE Journal on Selected Areas in Communications 01/1996; · 3.12 Impact Factor
  • W.E. Stephens, T.C. Banwell
    [Show abstract] [Hide abstract]
    ABSTRACT: EMI/EMC is a dominant problem encountered in high bit-rate transmission over unshielded twisted pair cable (UTP). This leads to a novel set of design tradeoffs between transceiver complexity (near term cost) and cable plant complexity (long term cost) for 155 Mb/s transmission on twisted pair cable which depends on the choice of line code. To understand the tradeoffs, the factors affecting RF emissions and susceptibility were examined in both installed cable plant and trellis configured cable plant models, which included both category 5 cable and interconnection hardware. In addition, the BER sensitivity to injected noise and pseudo-random data sequence length was measured for experimental 155 Mb/s links with 100 meters of category 5 cable using NRZ, MLT3, BPR1 and BPR4 line codes. A model for common-mode conversion in multi-pair UTP cables is presented. Radiated emissions occur in broad bands at 43, 53, 60, 70, and 80 MHz and show a positive correlation with the transmit signal spectrum. Termination of all propagating modes produced consistently lower radiated emissions than other standard cable termination procedures. For a given transmit level at 155 Mb/s, MLT3 has the lowest emissions between 30-50 MHz while BPR1 has the lowest emissions above 60 MHz. The emissions with MLT3 and BPR1 were 8-13 dB (10 dB typical) and 4-20 dB (13 dB typical) below NRZ levels, respectively. When the measured receiver penalty associated with three levels is included, MLT3, BPR1 and BPR4 still offer 5-15 dB better performance over NRZ at 155 Mb/s, although implementation complexity is greater as well
    Computers and Communications, 1995. Conference Proceedings of the 1995 IEEE Fourteenth Annual International Phoenix Conference on; 04/1995
  • T.C. Banwell
    [Show abstract] [Hide abstract]
    ABSTRACT: The performance of low-voltage bandgap regulators built with only npn transistors is examined. The power supply rejection ratio (PSRR) is significantly constrained, more than any other performance parameter, by the exclusion of a complimentary active load. The PSRR for an inherently stable (single operating point) bandgap regulator built using only npn transistors is bounded below by 2.5 (nV<sub>T</sub>/V<sub>cc</sub>)<sup>n</sup>=0.7 mV/V or 0.04 mV/V for circuits with n=2 or 3 stages, respectively. This represents a “gain” constraint imposed by the coincidence of signal and bias paths in bipolar circuits which employ current differencing or bootstrapping techniques. Base current errors can significantly degrade PSRR. Two all-npn circuits are presented with PSRR &les;0.1 mV/V that exhibit a single operating point under most circumstances
    IEEE Transactions on Circuits and Systems II Analog and Digital Signal Processing 04/1995;
  • T.C. Banwell
    [Show abstract] [Hide abstract]
    ABSTRACT: Describes a new bias current regulation circuit for single-stage bipolar and FET amplifiers which achieves high precision and simplicity through a combination of feedback error amplifier with bandgap reference. The internally generated reference voltage can be preset between 100-200 mV. The approach is ideal for applications where the overhead voltage must be minimized to reduce power dissipation, and typically offers <0.5% regulation and &les;40 ppm/°C temperature coefficient. The authors present three common applications which demonstrate the unique advantages of the new topology
    IEEE Journal of Solid-State Circuits 03/1994; · 3.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recent successes in transporting optical power near the 1-W level via optical fiber suggest that it may be possible to operate conventional telephone station sets using electricity derived photovoltaically from light in a fiber. The authors investigate the constraints on optical powering in fiber-in-the-loop (FITL) applications and assess its applicability in terms of end-to-end efficiency, loop length, and system cost. To make this assessment, they look at several different optical-powering system architectures and components vis-a-vis their cost-versus-delivered-power capability. Related issues such as safety and reliability are discussed.
    Journal of Lightwave Technology 04/1993; · 2.56 Impact Factor
  • T.C. Banwell
    [Show abstract] [Hide abstract]
    ABSTRACT: There is a growing need to reduce the power consumption of the high-speed components in broadband telecommunications networks. This will require that power processing be treated simultaneously with signal processing in the development of new broadband products. The power consumption of fiber optic transmitters, which can use either lasers or LEDs, is considered to be relatively large. LED transmitters normally require considerably more operating power than lasers, which is often the deciding factor in the selection of a laser rather than an LED in short span 100-200 Mb/s fiber optic links. The LED transmitter issue therefore represents a good opportunity for examining new strategies to improve power-hungry technologies. The overall performance of an LED transmitter can be enhanced by using the available supply voltage more efficiently through power conditioning. A prototype 155 Mb/s LED transmitter that achieves a threefold improvement in power efficiency is described
    IEEE Transactions on Power Electronics 02/1993; · 5.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The feasibility of transmitting 1 55-Mb/s SONET/ATM signals over 131 m of unshielded 24 AWG single twisted pair copper cable and 213 m of shielded 22 AWG twisted pair cable with bit error ratios of less than 10 <sup>-13</sup> is shown. The transmission performance of the single-pair unshielded cable is compared to that of category 3 and 5 four-pair unshielded twisted pair cables and category 1 two-pair shielded twisted pair cables. The merits of two-level encoding and three-level encoding are examined. The three-level encoding has a noise margin that is 6 dB greater than the two-level encoding. The results indicate that it may be feasible to employ copper drops for distribution of SONET/ATM asynchronous optical network/asynchronous transfer mode) signals to businesses and residences and for a local area network within an office complex
    Global Telecommunications Conference, 1992. Conference Record., GLOBECOM '92. Communication for Global Users., IEEE; 01/1993
  • L.A. Reith, I. Ladany, T.C. Banwell, C.E. Zah
    [Show abstract] [Hide abstract]
    ABSTRACT: An electroplating technique for permanently fixing single-mode fibers into position in optical device packages is described. In this technique, the fiber is mounted in a metal tube and aligned to an optical device mounted on a metal substrate. The fiber is in close proximity to the substrate and a flexible conductive gel is used to connect the two electrically. The fiber, gel, and substrate thus form the plating cathode. When immersed in a plating bath with an anode inserted, metal can be deposited across the gel, forming a strong metal bridge between the fiber and substrate, locking the fiber into position. Under appropriate conditions, misalignments within ±1 μm during the plating process have been observed. This technique was used to package a laser diode transmitter, which locked the laser-to-fiber alignment to within 0.7 μm, or 0.1 dB of the optimum coupled power
    Journal of Lightwave Technology 08/1992; · 2.56 Impact Factor
  • T.C. Banwell, W.E. Stephens, G.R. Lalk
    [Show abstract] [Hide abstract]
    ABSTRACT: The feasibility is demonstrated of transmitting 155 Mbit/s SONET-ATM signals over 131 m of unshielded 24 AWG single twisted pair copper cable and 213 m of shielded 22 AWG twisted pair cable with bit error ratios of less than 10<sup>-13</sup>. The transmission performance of the single-pair unshielded cable is compared with that of four-pair unshielded twisted pair cables.
    Electronics Letters 07/1992; · 1.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The implementation of a highly integrated experimental research prototype ATM/SONET interface that operates at the SONET OC-3 rate of 155.52 Mbit/s is reported. The prototype interface provides various features of the physical (SONET) and asynchronous transfer mode (ATM) layers of the B-ISDN protocol reference model. This type of interface could be used in applications such as workstation interfaces in a switched ATM local area network or for the user-network interface in a broadband public network or customer premises network.
    Electronics Letters 12/1991; · 1.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The authors examine the physical design issues associated with terabit/second switching systems, particularly with regard to the customer access portion of the switch. They determine the physical design requirements in the areas of backplane interconnections, integrated circuit packaging, and circuit board technology and identify areas where existing- or near-future physical design technologies are inadequate to meet the requirements of this application. A new 3D interconnection architecture that solves some of the problems encountered at the backplane level is suggested. It is also suggested that multichip module technology will help meet some of the speed and density requirements at the chip packaging level. Some of the system-level consequences of the proposed model are discussed
    IEEE Journal on Selected Areas in Communications 11/1991; · 3.12 Impact Factor
  • T.C. Banwell
    [Show abstract] [Hide abstract]
    ABSTRACT: Techniques to reduce the sensitivity of the error amplifier to supply voltage and temperature variations in low-voltage regulators which use only n-p-n transistors as active devices are examined. The line regulation for inherently stable error amplifier topologies is bounded below by 0.7 mV/V. Current or voltage sharing imposes a constraint on the gain available from the feedback error amplifier. This has not been previously achieved with n-p-n or BiCMOS circuits. A fully compensated all-n-p-n regulator that achieves the optical performance using feedforward internal bias stabilization is described. The factors degrading line regulation are examined
    IEEE Journal of Solid-State Circuits 02/1991; · 3.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The authors examine several issues associated with the physical design of the very-high-throughput (terabit per second) packet switching systems that will be needed to provide ubiquitous broadband services. It is shown that conventional physical design alternatives do not scale well to the high data rates and complex connectivity needed to implement these systems. In particular, conventional interconnection technology alternatives, especially at the backplane level, do not provide adequate intramodule connectivity at the required data rates. An alternative design that uses a three-dimensional architecture is proposed. It provides rich connectivity among the switch functions but requires a anew generation of packaging hardware. The power delivery, thermal management, and other important issues that must be addressed before these large broadband switching systems can be realized are discussed
    Global Telecommunications Conference, 1990, and Exhibition. 'Communications: Connecting the Future', GLOBECOM '90., IEEE; 01/1991
  • Optical Engineering 01/1990; 29(3). · 0.96 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A multicasting photonic space switch reconfigurable in 50 ns is demonstrated utilising commercially available acousto-optic Bragg cells at lambda =0.83 mu m. Insertion loss of 15 dB, extinction ratio of 33 dB, crosstalk of -24 dB and polarisation difference of 0.8 dB are reported.
    Electronics Letters 03/1989; · 1.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A multicasting photonic switch reconfigurable in 50 ns is demonstrated utilizing acousto-optic Bragg cells at λ=0.83 μm. Crosstalk of -20 dB and an extinction ratio of -30 dB have been measured. Theoretical calculations indicate a maximum switch size of 20×20 and an insertion loss of 11 dB
    Optical Communication, 1988. (ECOC 88). Fourteenth European Conference on (Conf. Publ. No.292); 10/1988
  • T. C. Banwell, W. E. Stephens
    [Show abstract] [Hide abstract]
    ABSTRACT: This patent describes a laser driver circuit for modulating the light output power of a laser between a desired predetermined low output power level and a high output power level in response to the zeroes and ones, respectively, of an input digital signal comprising: a photodetector for producing a feedback signal proportional to the light output of the laser, means for deriving a reference signal from the input digital signal, means for combining the photodetector feedback signal, the reference signal and a level setting input signal having a value determined by the desired predetermined low output power level of the laser, to produce an error signal proportional to the difference between the desired predetermined low output power level of the laser and the low output power level detected by the photodetector, and an integrating low frequency error amplifier responsive to the error signal for generating a bias current to the laser to maintain the low output power level at the desired predetermined value, characterized in that the laser driver circuit further comprises a variable gain amplifier connected between eth combining means and the error amplifier, the variable gain amplifier having a gain controlled by the input digital signal, the gain of the variable gain amplifier being a first value when the input digital signal is one and a second value when the input digital signal is zero.