On /spl Zopf//sub 4/-linear Preparata-like and Kerdock-like codes

We say that a binary code of length n is additive if it is isomorphic to a subgroup of /spl Zopf//sub 2//sup /spl alpha// /spl times/ /spl Zopf//sub 4//sup /spl beta//, where the quaternary coordinates are transformed to binary by means of the usual Gray map and hence /spl alpha/ + 2/spl beta/ = n. In this paper, we prove that any additive extended Preparata (1968) -like code always verifies /spl alpha/ = 0, i.e., it is always a /spl Zopf//sub 4/-linear code. Moreover, we compute the rank and the dimension of the kernel of such Preparata-like codes and also the rank and the kernel of the /spl Zopf//sub 4/-dual of these codes, i.e., the /spl Zopf//sub 4/-linear Kerdock-like codes.     

Generalized MacWilliams identities for /spl Zopf//sub 4/-linear codes

In this correspondence, the generalized MacWilliams identities between the support weight distributions of a /spl Zopf//sub 4/-linear code of type 4/sup k/ and that of its dual are established.     

Lee metric decoding of alternant codes over /spl Zopf//sub q/

A multi-stage Lee metric list decoding approach for alternant codes over /spl Zopf/(p/sup l/ )where p is prime and l/spl ges/2 is proposed. It is demonstrated that the error-correcting capability of such a decoding scheme increasingly surpasses that of a single-stage decoding approach as the length of the code and l increases.     

On the generators of /spl Zopf//sub 4/ cyclic codes of length 2/sup e/

Results are presented on the generators of ideals in the ring /spl Zopf//sub 4/[x]/(x/sup n/-1). In particular, each ideal (cyclic code) has a unique distinguished set of generators that characterizes any cyclic code. Some results about dual codes are also included.     

Cyclic codes over GR(4/sup m/) which are also cyclic over /spl Zopf//sub 4/

Let GR(4/sup m/) be the Galois ring of characteristic 4 and cardinality 4/sup m/, and /spl alpha/_={/spl alpha//sub 0/,/spl alpha//sub 1/,...,/spl alpha//sub m-1/} be a basis of GR(4/sup m/) over /spl Zopf//sub 4/ when we regard GR(4/sup m/) as a free /spl Zopf//sub 4/-module of rank m. Define the map d/sub /spl alpha/_/ from GR(4/sup m/)[z]/(z/sup n/-1) into /spl Zopf//sub 4/[z]/(z/sup mn/-1) by d/spl alpha/_(a(z))=/spl Sigma//sub i=0//sup m-1//spl Sigma//sub j=0//sup n-1/a/sub ij/z/sup mj+i/ where a(z)=/spl Sigma//sub j=0//sup n-1/a/sub j/z/sup j/ and a/sub j/=/spl Sigma//sub i=0//sup m-1/a/sub ij//spl alpha//sub i/, a/sub ij//spl isin//spl Zopf//sub 4/. Then, for any linear code C of length n over GR(4/sup m/), its image d/sub /spl alpha/_/(C) is a /spl Zopf//sub 4/-linear code of length mn. In this article, for n and m being odd integers, it is determined all pairs (/spl alpha/_,C) such that d/sub /spl alpha/_/(C) is /spl Zopf//sub 4/-cyclic, where /spl alpha/_ is a basis of GR(4/sup m/) over /spl Zopf//sub 4/, and C is a cyclic code of length n over GR(4/sup m/).     

Generalization of the /spl Sigma//sub 0/-rank criteria for space-time codes

Recently, Liu et al., developed the /spl Sigma//sub 0/-rank criteria for space-time codes. It provides a sufficient condition on codeword and generator matrices defined over finite rings /spl Zopf//sub 2k/(j) to ensure full spatial diversity with 2/sup 2k/-QAM modulation. Here, we generalize the /spl Sigma//sub 0/-rank criteria and derive a sufficient condition on the generator matrices defined over finite rings /spl Zopf//sub 2l/(j) to ensure full spatial diversity with 2/sup 2k/-QAM modulation for any positive integer l/spl les/k. We also show that generator matrices defined over GF(2) satisfying the BPSK stacking construction constraint of Mammons and El Gamal achieve full spatial diversity when used with 2/sup 2k/-QAM modulation.     

Measurement technique for the quotient of cross sections /spl sigma//sub e/(/spl lambda//sub s/)//spl sigma//sub a/(/spl lambda//sub s/) of erbium-doped fibers

A method for the measurement of the quotient of the emission and absorption cross section of erbium-doped fibers is presented which utilizes the spontaneous emission perpendicular to the fiber axis. The maximum population of the first excited state achievable through illumination by signal light (/spl lambda//sub s/=1530 nm) is fixed by the quotient of the absorption and the emission cross section. This fact is used to determine the desired quotient. First measurements show that this method is very simple and highly accurate.<>     

/spl pi//4-shifted differential QPSK space-time block codes

A new power efficient modulation scheme for two transmit antennas is introduced. It is an extension of /spl pi//4-DQPSK used in single antenna systems. It achieves full diversity advantage and is suitable for nonlinear amplifiers due to its inherit /spl pi//4-phase shift in every symbol interval for both antennas.     

Optimal self-dual codes over F/sub 2//spl times/F/sub 2/ with respect to the Hamming weight

In this paper, we study optimal self-dual codes and type IV self-dual codes over the ring F/sub 2//spl times/F/sub 2/ of order 4. We give improved upper bounds on minimum Hamming and Lee weights for such codes. Using the bounds, we determine the highest minimum Hamming and Lee weights for such codes of lengths up to 30. We also construct optimal self-dual codes and type IV self-dual codes.     

Maximum minimal distance partitioning of the /spl Zopf//sup 2/ lattice

We study the problem of dividing the /spl Zopf//sup 2/ lattice into partitions so that minimal intra-partition distance between the points is maximized. We show that this problem is analogous to the problem of sphere packing. An upper bound on the achievable intra-partition distances for a given number of partitions follows naturally from this observation, since the optimal sphere packing in two dimensions is achieved by the hexagonal lattice. Specific instances of this problem, when the number of partitions is 2/sup m/, were treated in trellis-coded modulation (TCM) code design by Ungerboeck (1982) and others. It is seen that methods previously used for set partitioning in TCM code design are asymptotically suboptimal as the number of partitions increases. We propose an algorithm for solving the /spl Zopf//sup 2/ lattice partitioning problem for an arbitrary number of partitions.     

The extended irregular /spl pi/-rotation LDPC codes

We extend the class of deterministic /spl pi/-rotation low-density parity-check codes to a more flexible irregular pattern. The extended codes maintain the advantages of the classic /spl pi/-rotation pattern with easy implementation based on a single vector while providing superb performance.     

InGaAs-InP mesa DHBTs with simultaneously high f/sub /spl tau// and f/sub max/ and low C/sub cb//I/sub c/ ratio

We report an InP-InGaAs-InP double heterojunction bipolar transistor (DHBT), fabricated using a conventional triple mesa structure, exhibiting a 370-GHz f/sub /spl tau// and 459-GHz f/sub max/, which is to our knowledge the highest f/sub /spl tau// reported for a mesa InP DHBT-as well as the highest simultaneous f/sub /spl tau// and f/sub max/ for any mesa HBT. The collector semiconductor was undercut to reduce the base-collector capacitance, producing a C/sub cb//I/sub c/ ratio of 0.28 ps/V at V/sub cb/=0.5 V. The V/sub BR,CEO/ is 5.6 V and the devices fail thermally only at >18 mW//spl mu/m/sup 2/, allowing dc bias from J/sub e/=4.8 mA//spl mu/m/sup 2/ at V/sub ce/=3.9 V to J/sub e/=12.5 mA//spl mu/m/sup 2/ at V/sub ce/=1.5 V. The device employs a 30 nm carbon-doped InGaAs base with graded base doping, and an InGaAs-InAlAs superlattice grade in the base-collector junction that contributes to a total depleted collector thickness of 150 nm.     

Resonant Frequency of a TE//sub 01delta//spl deg/ Dielectric Resonator

The resonant frequency of a TE/sub 01delta//spl deg/ dielectric resonator was obtained by assuming a cylindrical surface containing the circumference of a dielectric resonator as a magnetic wall. In such a method, the error was less than 10 percent. In this short paper, the resonant frequency is obtained by a variational method, where the surface impedance is variated from a infinite value. The theoretical value of a resonant frequency has a good agreement with our experimental result with an error less than 1 percent.     

Characteristics of MOSFET Prepared on Si/MgO /spl dot/ Al/sub 2/O/sub 3//SiO/sub 2//Si Structure

A new silicon on insulator (SOI) wafer with epitaxial-Si/ epitaxial-MgO/spl dot/Al/sub 2/O/sub 3/ (0.1 /spl mu/m)/SiO/sub 2/(0.5 /spl mu/m)/     

H/sub /spl infin// control of differential linear repetitive processes

Repetitive processes are a distinct class of two-dimensional (2-D) systems (i.e., information propagation in two independent directions) of both systems theoretic and applications interest. They cannot be controlled by direct extension of existing techniques from either standard [termed one-dimensional (1-D) here] or 2-D systems theory. Here, we give new results on the relatively open problem of the design of control laws using an H/sub /spl infin// setting. These results are for the sub-class of so-called differential linear repetitive processes which arise in applications.     

Efficient amplification using the /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica fiber

Amplification characteristics of the three-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica glass fiber are investigated under strong signal saturation and high pump power (150 mW). Aluminum codoped Nd-silica fibers exhibit strong superfluorescent behavior in the four-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 11/2/ transition which limits the optical conversion efficiency into the three-level transition. Ge-doped silica fibers do not exhibit this limitation and can efficiently amplify in the three-level transition with current laser-diode pump technology.     

Robust speed control of an induction motor: an /spl Hscr//sub /spl infin// control theory approach with field orientation and /spl mu/-analysis

In this paper we present a robust speed control strategy for an induction motor under field orientation. The control framework employed properly represents the induction motor state-space model and its inherent variations, which are treated as structured uncertainties. Applying an /spl Hscr//sub /spl infin//, optimization methodology on this framework we derive a stabilizing controller to meet design objectives and then robust stability and performance against such variations are checked by using /spl mu/-analysis. No on-line tuning is required for the parameters of the derived controller, which is the dynamic system responsible to keep the rotor flux orientation as well as the speed regulation at design levels, irrespective of the motor operating points. A general methodology arose from the usage of the proposed strategy and simulated experiments showed satisfactory results for the robust speed control of an induction motor.     

Performance analysis of minimum /spl lscr//sub 1/-norm solutions for underdetermined source separation

Results of the analysis of the performance of minimum /spl lscr//sub 1/-norm solutions in underdetermined blind source separation, that is, separation of n sources from m(相似文献   

A novel high-/spl kappa/ SONOS memory using TaN/Al/sub 2/O/sub 3//Ta/sub 2/O/sub 5//HfO/sub 2//Si structure for fast speed and long retention operation

A novel high-/spl kappa/ silicon-oxide-nitride-oxide-silicon (SONOS)-type memory using TaN/Al/sub 2/O/sub 3//Ta/sub 2/O/sub 5//HfO/sub 2//Si (MATHS) structure is reported for the first time. Such MATHS devices can keep the advantages of our previously reported TaN/HfO/sub 2//Ta/sub 2/O/sub 5//HfO/sub 2//Si device structure to obtain a better tradeoff between long retention and fast programming as compared to traditional SONOS devices. While at the same time by replacing hafnium oxide (HfO/sub 2/) with aluminum oxide (Al/sub 2/O/sub 3/) for the top blocking layer, better blocking efficiency can be achieved due to Al/sub 2/O/sub 3/'s much larger barrier height, resulting in greatly improved memory window and faster programming. The fabricated devices exhibit a fast program and erase speed, excellent ten-year retention and superior endurance up to 10/sup 5/ stress cycles at a tunnel oxide of only 9.5 /spl Aring/ equivalent oxide thickness.     

Properties of Si/sub 3/N/sub 4//Si/sub x/Ge/sub 1-x/ metal-insulator-semiconductor capacitors

The density of fast interface states was studied in Si/sub 3/N/sub 4//Si/sub 0.8/Ge/sub 0.2/ metal-insulator-semiconductor (MIS) capacitors. The interface state density does not appear to be strongly affected by the presence of a thin Si interlayer between the nitride and SiGe alloy. This is in contrast to the results when SiO/sub 2/ is used as the insulator material in similar structures.<>