The present invention employs one or more complementary sequences, e.g., Golay pairs of sequences, to provide accurate and efficient synchronization between radio transceivers. A matched filter corresponding to a complementary pair of sequences is used to correlate the received signal with one of the complementary pair of sequences. A peak output is detected from the matched filter, and the detected peak is used to generate a timing estimate for synchronizing transmissions between transceivers. Each of the complementary sequences has minimal aperiodic autocorrelation sidelobe values for all non-zero delays of that complementary sequence and a maximal autocorrelation main lobe value for a zero delay of that complementary sequence. The one sequence may be used as a preamble portion of a random access message transmitted by a mobile station to a base station over a random access channel. The sequence may also be used as a synchronization code transmitted by the base over a synchronization channel and used by mobile stations to obtain synchronization. An efficient Golay correlator and a bank of efficient Golay correlators for correlating respectively with a single sequence and with a set of orthogonal sequences are disclosed.

Method and apparatus for efficient synchronization in spread spectrum communications

A receiving apparatus includes a base-band conversion circuit, a synchronizing circuit/code generator and a demodulator. The base-band conversion circuit converts a received signal into a base-band signal. The synchronizing circuit/code generator detects a spread code included in the received signal to generate a plurality of spread codes in synchronization with the spread code included in the received signal. The demodulator uses the plurality of spread codes supplied by the synchronizing circuit/code generator to demodulate the base-band signal.

Spread spectrum receiving apparatus

A spread-spectrum code division multiple access interference canceler for reducing interference in a direct sequence CDMA receiver having N chip-code channels. The interference canceler includes a plurality of correlators or matched filters, a plurality of spread-spectrum-processing circuits, subtracting circuits, and channel correlators or channel-matched filters. Using a plurality of chip-code signals, the plurality of correlators despreads the spread-spectrum CDMA signal as a plurality of despread signals, respectively. The plurality of spread-spectrum-processing circuits uses a timed version of the plurality of chip-code signals, for spread-spectrum processing the plurality of despread signals, respectively, with a chip-code-signal corresponding to a respective despread signal. For recovering a code channel using an i th chip-code-signal, the subtracting circuits subtracts from the spread-spectrum CDMA signal, each of the N-1 spread-spectrum-processed-despread signals thereby generating a subtracted signal. The N-1 spread-spectrum-processed-despread signals do not include the spread-spectrum-processed-despread signal of the i th channel of the spread-spectrum CDMA signal. The channel correlator or channel-matched filter despreads the subtracted signal.

Spread spectrum CDMA subtractive interference canceler system

A surface acoustic wave (SAW) filter includes a piezoelectric substrate. A resin pattern having a permittivity less than that of the piezoelectric substrate and first and second conductor patterns are disposed on the piezoelectric substrate. The first conductor pattern defines two one-terminal-pair SAW resonators and two longitudinally coupled resonator SAW filters. A portion of the second conductor pattern defines wiring traces having different potentials. Portions of the wiring traces facing each other in a plan view are disposed on the resin pattern.

Surface acoustic wave filter and communication apparatus

The problem of allocating bandwidth on the upstream channel (26) of an HFC cable network (10) for contention-based transmission of requests that are used to reserve upstream bandwidth (26) for transmission of user data is solved by a method of allocation which dynamically adapts to the prevailing offered load of reservation requests. In one embodiment this is done by determining an appropriate size for a contention interval in each upstream transmission frame by attempting to balance the rates of flow of user data into and out of a virtual global data queue using a fluid approximation method that is based on a solution to a balanced equation relating the demand and supply of slots for data transmission within each frame.

Method and device for bandwidth allocation in multiple access protocols with contention-based reservation

A surface acoustic wave device includes a piezoelectric substrate, a wave guide path provided on the piezoelectric substrate and an interdigital transducer for exciting a surface acoustic wave. The interdigital transducer is provided with plural portions of mutually different pitches of the electrode finger, respectively corresponding to different frequencies. The portions are parallelly arranged along a direction perpendicular to the propagation direction of the surface acoustic wave. The surface acoustic wave generated by the interdigital transducer is entered in concentrated manner into the wave guide path.

Efficient surface acoustic wave device capable of excitation in plural frequency bands, and signal receiver and communication system utilizing the same

In a surface acoustic wave device, there are arranged a piezoelectric substrate, an input electrode and an output electrode. The input electrode is formed on the substrate, and generates a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal. The output electrode is also formed on the substrate, and converts the surface acoustic wave to an electric signal. One of the input and output electrodes includes a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave. The other one of the input and output electrodes may comprise a pair of taps arranged at a predetermined distance in the propagation direction. The electrode including a plurality of taps or the electrode including a pair of taps satifies a predetermined relation established among a length between the taps, a transmission speed of the input signal, a propagation velocity of the surface acoustic wave and so forth. According to such a structure, two bits of the signal can be processed without a delay circuit. A demodulating device and a communication system respectively include the surface acoustic wave device so that a circuit structure can be simplified and that data can be reproduced with a high signal quality.

Surface acoustic wave device, and demodulating apparatus and communication system using the surface acoustic wave device

A surface acoustic wave element is provided with a piezoelectic substrate, a first input transducer, a second input transducer and an output device such as output electrode. The piezoelectric substrate has a first and a second surfaces which are mutually faced. The first input transducer is formed on the first surface of the substrate to generate a first surface acoustic wave which propagates in a predetermined direction. The second transducer is formed on the first surface of the substrate to generate a second surface acoustic wave which propagates in a direction opposite to the predetermined direction. The output device is formed on the first surface of the substrate to extract a signal produced by an interaction of the first and second surface acoustic waves. At least part of the second surface of the substrate is caused to be inclined in a direction perpendicular to the predetermined direction with respect to the first surface.

Surface acoustic wave element and communication system using the same

A diffusion code generating method for a code division multiplex communication by a spread spectrum system is provided. A receiving apparatus according to the above method receives the signal which was multiplexed by using a plurality of sets of diffusion codes and comprises: a generator to generate a sync code and a plurality of sets of diffusion codes other than the sync code; a correlator to obtain a correlation between a reception signal and the sync code generated from the generator; and a receiver to receive the reception signal on the basis of the plurality of sets of diffusion codes generated from the generator. The generator generates the sync code in a manner such that the cross-correlation values are set to very small values at positions near a code sync point or are enough smaller than the autocorrelation peak of the sync code or are set to very small values at both of or either one of the positions before and after the code sync point.

Diffusion code generating method for spread spectrum communication

An elastic surface wave convolve comprises a piezoelectric substrate, a plurality of input transducers formed on said substrate for generating elastic surface waves corresponding to respective input signals, a plurality of waveguides provided side by side on a region of the substrate where elastic surface waves radiated from the input transducers overlap, wherein a convolution signal of input signals is produced due to parametric mixing effect of elastic surface waves in respective waveguides, these waveguides generating an elastic surface wave corresponding to the convolution signal, and an output transducer for receiving the elastic surface wave radiated from the waveguides and taking out an electrical signal by conversion of the convolution signal, wherein the width of elastic surface wave radiated from the waveguides is narrower immediately before reception with the output transducer than immediately after radiation from the waveguides.

Norihiro Mochizuki

Papers

Efficient surface acoustic wave device capable of excitation in plural frequency bands, and signal receiver and communication system utilizing the same

Surface acoustic wave device, and demodulating apparatus and communication system using the surface acoustic wave device

Surface acoustic wave element and communication system using the same

Diffusion code generating method for spread spectrum communication

Elastic surface wave convolva having wave width converting means and communication system using same