Nec Corporation

Nec Electronics Corporation

Osamu Ohnishi

Takeshi Inoue

Osamu Myohga

Tadao Uchikawa

Sadayuki Takahashi

Yasuhiro Sasaki

Toshiyuki Okuyama

Kaneo Uehara

Isao Kagaya

Nobuo Ohde

Akio Iwamoto

Sadayuki Ueha

A reverse spreading device is provided which is capable of performing timing detection and channel estimation even in a large frequency offset environment without great increases in its circuit scale and its power consumption and of expanding a range being within the AFC (Automatic Frequency Control) for the frequency offset. A multiplication is made by multipliers between complex base band signals and spread codes and then resulting n-pieces of multiplied values are integrated by m-pieces of adders for every k-pieces of multiplied values to produce m-pieces of complex intermediate signals before obtaining complex symbols. A probability of correct synchronization is increased by providing a frequency offset to m-pieces of complex intermediate signals using phase rotators to compensate for rotation within one symbol period and to obtain a great spreading gain. A range being within the AFC for the frequency offset is expanded since a phase error is corrected before a production of the complex symbol signals.

Reverse spreading device, timing detecting device, channel estimating device, frequency error measurement method and automatic frequency control method

A cell search method is disclosed in which autocorrelation patterns are subtracted from a correlation value profile. When carrying out a cell search with respect to a correlation value profile, the peak timing of a first base station is first detected and the scrambling code of this base station is identified. A path search process is then carried out using this timing and scrambling code to detect timings at which multipath occur. Autocorrelation patterns that center on the obtained frame timings and autocorrelation patterns that center on multipath are next generated and a process is performed to subtract these autocorrelation patterns from the correlation value profile. This process enables the rapid detection of peak produced by a second base station.

Cell search method to subtract autocorrelation patterns from a correlation value profile

An apparatus is provided for detecting a correlation of samples with a spread code comprising: an L-chip accumulator which inputs the samples to generate and output an intermediate correlation signal; M memories, each of which stores L&#xd7;M samples of the intermediate correlation signal; an adder which has input terminals as many as M and inputs from each of the input terminals the intermediate correlation signal which is outputted from the L-chip accumulator or the intermediate correlation signal which is outputted from a corresponding memory among the memories; and a controller which supplies the intermediate correlation signal outputted from the L-chip accumulator to the memories as many as M and to the M input terminals of the adder in rotation with a unit of L&#xd7;N samples, and reads, and supplies to each of the input terminals of the adder, the intermediate correlation signal which has been stored in each of the memories M&#x2212;1 times; wherein an output of the adder is outputted as an correlation signal outputted from the apparatus.

Apparatus for detecting correlation, spectrum despread apparatus and receiver having the same, and method for detecting correlation

Provided is an apparatus for detecting a correlation of samples with a spread code comprising: an L-chip accumulator which inputs the samples to generate and output an intermediate correlation signal of a bit width of W, wherein W is an integer larger than one; memories as many as M&minus; each of which has a data width of 2W bits and addresses as many as L&times;N/2 and stores samples of the intermediate correlation signal as many as L&times;N while combining two samples as one pair; an adder which has input terminals as many as M and inputs from one of the input terminals the intermediate correlation signal which is outputted from the L-chip accumulator and from the other of the input terminals the intermediate correlation signal which is outputted from a corresponding memory among the memories; and a controller which supplies the intermediate correlation signal outputted from the L-chip accumulator to the memories as many as M&minus;1 in rotation with a unit of L&times;N samples, and reads, and supplies to each of the other of the input terminals of the adder, the intermediate correlation signal which has been stored in each of the memories M&minus;1 times; wherein an output of the adder is outputted as an correlation signal outputted from the apparatus.

A synchronization acquisition device in a spread spectrum communication system is disclosed that can both reduce the required storage capacity and prevent erroneous detection caused by such factors as noise. In the first correlation value processing, the control circuit causes only the N highest-ranking values of correlation values obtained by a correlator to be stored in a timing-correlation value storage unit. In the second and subsequent calculations, the control circuit stores K&times;P &plus;(1&minus;K)&times;P as the new value if a timing corresponding to the obtained correlation value P has already been stored, and stores K&times;P as the new value if a corresponding timing is not stored but the obtained correlation value is greater than the N correlation value that is stored. Instead of storing correlation values of all timings of a fixed interval portion, only correlation values that are peak candidates and the associated timing information are stored, and as a result, the device allows a reduction in the required storage capacity. In addition, in slot averaging processing, the reordering of timings that are peak candidates is based only on actual correlation values and not on dummy value, and erroneous detection due to such factors as noise therefore can be reduced.

Synchronization acquisition device for both preventing erroneous detection due to noise and reducing required storage capacity

An image code transform system for arranging and composing a plurality of small screens of moving images to a large screen image, compressing and encoding the large screen image to generate a large screen compressed/coded data sequence, and extracting small screen compressed/coded data sequences of the plurality of small screens of moving images from the large screen compressed/coded data sequence. The system includes a multiplexer for re-arranging frames of the plurality of small screen moving images at an identical time to generate a composite frame and generating a large screen moving image signal of the composite frame; a compressor/encoder for compressing and encoding the large screen moving image signal on a block basis to generate a large screen compressed/coded data sequence signal and for outputting the large screen compressed/coded data sequence signal, the block being obtained by dividing the large screen moving image signal; and a separator/converter for separating and converting a plurality of small screen compressed signals corresponding to the plurality of small screens directly from the large screen compressed/coded data sequence signal.

Image code transform system for separating coded sequences of small

A motion picture encoder employs a motion compensation predictive encoding method to provide video signals. The motion picture encoder uses a relatively small storage capacity for a frame memory. Specifically, the frame memory has a storage capacity for storing at least two original pictures and one local decoding picture. A noise reducer unit performs a noise reducing process with respect to a present picture signal and a preceding picture signal. For example, a difference value is calculated between the present picture signal and preceding picture signal and is multiplied by a prescribed coefficient, whereupon a result of the multiplication is added to the preceding picture signal. In addition, a motion estimation/compensation unit is provided to perform motion estimation and motion compensation with respect to an encoding picture and a reference picture. A memory control unit is provided to control a data transfer between the noise reducer unit, frame memory and motion estimation/compensation unit. Specifically, the memory control unit controls the frame memory to allow an input of the present picture from the noise reducer unit, an output of the preceding picture to the noise reducer unit, outputs of the encoding picture and reference picture to the motion estimation/compensation unit and an input of the local decoding picture from the motion estimation/compensation unit. An interface between the frame memory and memory control unit has the capacity for a data transfer rate which is five or more times faster than an input rate of video signals.

Motion picture encoder

One driver having external electrodes arranged over both surfaces of a piezoelectric ceramic plate polarized in the direction of its thickness, and one generator having two mutually opposed interdigital electrodes on one or both surfaces of a piezoelectric ceramic plate and alternately polarized in the direction of its length between the electrode fingers of the interdigital electrodes are formed combined in alignment in the direction of the length of the piezoelectric ceramic plate. Alternatively, the driver and generator may be formed in alignment in the direction of the width of piezoelectric ceramic plate. By applying a low voltage to this piezoelectric ceramic transformer from the driver at a resonance frequency of a longitudinal vibration of second order mode of the piezoelectric ceramic plate, a high voltage can be picked up from the generator. Here, through connection of the input terminals and output terminals at the nodes of vibration, failure due to vibration of lead wires can be prevented, thereby obtaining a compact and slim transformer element that provides high reliability. A plurality of drivers and generators may also be employed, and in addition, an interdigital electrode may be used in the driver as well as in the generator.

Piezoelectric ceramic transformer

One driver having external electrodes arranged over both surfaces of a piezoelectric ceramic plate polarized in the direction of its thickness, and one generator having two mutually opposed interdigital electrodes on one or both surfaces of a piezoelectric cermic plate and alternateley polarized in the direction of its length between the electrode fingers of the interdigital electrodes are formed combined in alignment in the direction of the length of the piezoelectric ceramic plate. Alternatively, the driver and generator may be formed in alignment in the direction of the width of piezoelectric ceramic plate. By applying a low voltage to this piezoelectric ceramic transformer from the driver at a resonance frequency of a longitudinal vibration of second order mode of the piezoelectric ceramic plate, a high voltage can be picked up from the generator. Here, through connection of the input terminals and output terminals at the nodes of vibration, failure due to vibration of lead wires can be prevented, thereby obtaining a compact and slim transformer element that provides high reliability. A plurality of drivers and generators may also be employed, and in addition, an interdigital electrode may be used in the driver as well as in the generator.

A piezoelectric ceramic transformer includes a piezoelectric plate, a pair of driving sections, and a power generating section. The piezoelectric plate is made of a piezoelectric ceramic material and has a long plate-like structure. The pair of driving sections are arranged at two end portions of the piezoelectric plate and formed by alternately stacking a plurality of piezoelectric ceramic layers polarized in a direction of thickness of the piezoelectric plate and first internal electrodes, and cause longitudinal vibration by a driving voltage applied to first and second input terminals. The power generating section is arranged at a central portion of the piezoelectric plate in a lengthwise direction thereof and polarized in the lengthwise direction of the piezoelectric plate, and generates an output voltage at a first output terminal by the longitudinal vibration transmitted from the driving sections.

A piezoelectric ceramic transformer includes a high impedance portion having internal electrode layers which are opposite each other in a thickness direction in a radial central portion of a piezoelectric ceramic disc; an annular insulating portion disposed externally of the high impedance portion and having no electrode; and a low impedance portion disposed externally of the annular insulating portion and having annular internal electrode layers which are opposite each other in a thickness direction, the internal electrode layers of the high impedance portion being exposed on the side end face of the piezoelectric ceramic disc at respective ends thereof without being in contact with the annular internal electrode layer of the low impedance portion and being alternately connected on the side end face with external electrodes, each of which is connected with an electric terminal, and the internal electrode layers of the low impedance portion being exposed on the side end face of the piezoelectric ceramic disc at respective ends thereof and being alternately connected on the side end face with external electrodes, each of which is connected with an electric terminal. The transformer is operable in a high frequency band and can be used for an onboard power supply.

Low and high impedance thickness mode vibration portions are integrally laminated. Each vibrator portion comprises electrode layers between which a piezoelectric layer polarized in the direction of thickness is interposed. In each vibrator portion, every other electrode layer is connected to respective common external terminals. These common external terminals are of either four-terminal construction consisting two pairs, one pair for the low impedance mode vibrator portion and the other pair for the high impedance thickness mode vibrator portion, or three-terminal construction in which one of each pair are united together into a common terminal. Difference between the impedances is set on difference in the number of electrode layers and/or on difference in dielectric constant between the piezoelectric layers.

Thickness mode vibration piezoelectric transformer

In an ultrasonic motor which uses, as a stator, a longitudinal-torsional composite vibrator in which longitudinal and torsional piezoelectric elements are sandwiched between two blocks, and urges a rotor against the stator, a member is arranged on a piezoelectric element side of the block located near the rotor, so that an inertial mass of the member becomes larger with respect to torsional vibration than that of a rotor side.

Ultrasonic motor

An ultrasonic motor has a longitudinal-torsional composite transducer, a stator constituted by an ultrasonic vibrator sandwiching the transducer, and a rotor urged against the stator. The stator excites longitudinal-torsional ultrasonic vibrations to rotate the rotor by a frictional force. The motor includes a vibration adjusting rod for matching resonance frequencies of longitudinal and torsional ultrasonic vibrations of the stator with each other.

Ultrasonic motor and method of adjusting the same

This invention provides an ultrasonic motor using a bolt-tightened Langevin type torsional vibrator as a stator. The stator produces a vibrational energy to be converted into a rotational energy for a rotor contacted with the stator. The rotor is provided between a piezoelectric actuator and the torsional vibrator so that the contact state between the rotor and the torsional vibrator is controlled either one of loose contact and tight contact therebetween. According to the present invention, since the piezoelectric actuator is slidingly combined to the rotor, the rotation energy is not applied to the piezoelectric actuator and thus the life time of the actuator becomes long.

Growing community of inventors

Tokyo, Japan

Osamu Ohnishi