Abstract: A method and an apparatus of estimating a frequency offset in a wireless communication system are provided. An orthogonal frequency division multiplexing (OFDM) receiver performs envelope equalized processing (EEP) with respect to a reception signal and calculates a partial periodogram with a plurality of test values based on the reception signal which goes through the EEP. The OFDM receiver estimates a first frequency offset, a second frequency offset, and a third frequency offset based on two partial periodograms adjacent to each other among the partial periodograms for the plurality of test values.

Abstract: Provided is an apparatus for estimating a frequency offset by one training symbol including two symbols having the same structure and value in an OFDM system. The apparatus includes a first likelihood function calculator for modeling non-Gaussian impulsive noise included in the training symbol to a Cauchy probability density function in which a characteristic exponent of a BIS?S probability density function is 1, and calculating a likelihood function of a Cauchy distribution using the Cauchy probability density function, and a first frequency offset estimator for estimating an effective frequency offset value in which the likelihood function of the Cauchy distribution of the first likelihood function calculator becomes highest as a frequency offset estimation value. Thereby, it is possible to improve the performance of frequency offset estimation in non-Gaussian impulsive noise environments.

Abstract: A hermetic sealing method, which is capable of preventing oxidation of a micro-electromechanical system (MEMS) and sealing the MEMS at a low temperature. A low temperature hermetic sealing method having a passivation layer includes depositing a junction layer, a wetting layer, and a solder layer on a prepared lid frame, depositing a first protection layer for preventing oxidation on the solder layer and forming a lid, preparing a package base on which a device is disposed, and in which a metal layer and a second protection layer are formed around the device, and assembling the lid and the package base, heating, and sealing them. The protection layer is laminated on the solder layer that is formed by the lid, thereby preventing oxidation without using a flux. The low temperature hermetic sealing method having a passivation layer is suitable for sealing a device, such as the MEMS, which is sensitive to heat, water and other by-products.

Abstract: A hermetic sealing method, which is capable of preventing oxidation of a micro-electromechanical system (MEMS) and sealing the MEMS at a low temperature. A low temperature hermetic sealing method having a passivation layer includes depositing a junction layer, a wetting layer, and a solder layer on a prepared lid frame, depositing a first protection layer for preventing oxidation on the solder layer and forming a lid, preparing a package base on which a device is disposed, and in which a metal layer and a second protection layer are formed around the device, and assembling the lid and the package base, heating, and sealing them. The protection layer is laminated on the solder layer that is formed by the lid, thereby preventing oxidation without using a flux. The low temperature hermetic sealing method having a passivation layer is suitable for sealing a device, such as the MEMS, which is sensitive to heat, water and other by-products.

Abstract: An optical switch module for aligning and fixing an optical fiber array relative to an optical switch device includes an optical fiber support member for fixing the optical fiber array; a first support device forming a homo-junction with the optical fiber support member and including a first thermal deformation buffer device; and a second support device forming a hetero-junction with the first support device to support the first support device and including a second thermal deformation buffer device.

Abstract: A method for correcting or hammering a deformation which occurs in the multi-channel optoelectronic module and is caused by a post welding shift. The multi-channel optoelectronic module has an optical fiber support member for supporting an optical fiber array. The method includes the steps of: assembling the multi-channel optoelectronic module by using a laser welding process; and forming at least one welded portion on a predetermined position of said optical fiber supporting member corresponding to the deformation to thereby recover the deformation by using a shrinkage effect of the welded portion.

Abstract: A bidirectional optical communication module using a single optical fiber is disclosed. The module includes an optical fiber having a cut-away surface polished to have an acute angle between the cut-away surface and an axis of the optical fiber, a semiconductor laser emitting a transmission light coupled with a light fiber core, and a bidirectional optical device having a light receiving portion absorbing a receiving light outputted from the light fiber core for thereby optically coupling a bidirectional optical device in which a light receiving device is integrated into a light transmitting semiconductor laser as a single chip and an optical fiber when fabricating an optical module for implementing a light signal transmission and receiving operation using one optical fiber.

Abstract: The present invention relates to an accurate method using laser welding for mounting an optical focusing lens utilized in a semi-conductor laser module for optical transmission and optical amplification through an optical fiber and a laser module so produced. The laser module includes an aligned laser diode, a lens fixture mounting the laser diode, a focusing lens mounted within a lens housing which in turn is mounted by a lens ring to the lens fixture. In the method, the steps include aligning mutual positions between the laser diode and the optical focusing lens in the vertical and horizontal directions so that the magnitude of the optical signal output from the optical fiber is maximized after the distance between the optical focusing lens and the optical fiber is adjusted and fixed to obtain a maximum optical coupling efficiency between the laser diode and the optical fiber. Next a laser-welding step is performed at an interval between the lens housing and the lens ring.

Abstract: A package for a power semiconductor device is made using the method comprising the steps of preparing a lead frame including a blade or paddle for providing a semiconductor chip on a top surface thereof, tie bars for supporting said paddle, wherein said paddle being provided lower in horizontal surface than the leads; attaching a heat radiating plate on a bottom surface of the paddle by cladding; attaching a Kovar plate on the top surface of the paddle by soldering, said Kovar plate having similar heat expansion coefficient to that of the chip; providing the chip on the Kovar plate by soldering; wire-bonding terminals of said semiconductor chip to the corresponding leads of the lead frame, respectively; coating polyimide over the semiconductor chip by spin-coating; curing the polyimide coated thus; forming a metal cap above the said paddle by soldering, and injecting a molding material into a molder for enclosing the paddle and curing the molding material injected thus.

Abstract: A method of packaging a power semiconductor device is disclosed, comprising the steps of preparing a lead frame including a paddle for providing a semiconductor chip on a top surface thereof, tie bars for supporting said paddle, wherein said paddle being provided lower in horizontal surface than the leads; attaching a heat radiating plate on a bottom surface of the paddle by cladding; attaching a Kovar plate on the top surface of the paddle by soldering, said Kovar plate having similar heat expansion coefficient to that of the chip; providing the chip on the Kovar plate by soldering; wire-bonding terminals of said semiconductor chip to the corresponding leads of the lead frame, respectively; coating polyimide over the semiconductor chip by spin-coating; curing the polyimide coated thus; forming a metal cap above the said paddle by soldering, and injecting a molding material into a molder for enclosing the paddle and curing the molding material injected thus the method can be applied to produce a plastic packa