Hughes Electronics Corporation

Hughes Aircraft Company

Hughes Network Systems, LLC

Simha Erlich

Michael I Parr

Allan B Lamkin

T G Vishwanath

Zhen-Liang Shi

Graham M Avis

Ho Lee

A method for enabling synchronization of a communications terminal in a wireless communication system, and a corresponding acquisition system of the communications terminal, wherein the method consists of the steps of: receiving a burst at a receiver of the communications terminal, the burst containing a composite waveform including two or more component waveforms, wherein each of the two or more waveforms has a known frequency variation throughout the burst; detecting the presence of the composite waveform; and estimating a frequency offset and a timing offset of the composite waveform as received into the receiver, whereby synchronization is achieved.

Acquisition mechanism for a mobile satellite system

A waveform to be transmitted as a burst within a channel that is used for the synchronization of unsynchronized wireless communications terminals in a wireless communications system, and a method of synchronization involving the waveform, that consists of a composite waveform. The composite waveform comprises two or more component waveforms, wherein each of the two or more component waveforms has a known frequency variation throughout the burst. The composite waveform has a composite bandwidth on an order of an available channel bandwidth and each of said two or more component waveforms have a component bandwidth on the order of the available channel bandwidth. Furthermore, a range of values for the differences between the instantaneous frequencies of two of said two or more component waveforms is on an order of twice of said available channel bandwidth.

Synchronization in mobile satellite systems using dual-chirp waveform

A communication system that communicates between a base station and a mobile station over a wireless rf channel. The communication system uses a novel protocol for transmitting a data frame in which an 8-bit data byte is divided into two 4-bit data nibbles. Each data nibble is assigned a 4-bit sequence number to form a transmission byte. By determining the sequence number of any transmission byte or series of transmission bytes, the beginning and the end of a data frame can be determined. A CRC check indicates when a data frame has been received successfully. The protocol does not require the use of unique start-of-frame (SOF) and end of-frame (EOF) characters. Also, the system implements a majority vote algorithm that collects data from successively transmitted copies of a given data frame and performs a majority vote to determine a mostly likely received data pattern. The protocol allows the system to achieve an improvement analogous to a 1.5 to 2.5 dB increase in signal power over other transmission protocols that require the use of SOF and EOF characters to transmit a data frame.

Byte sequencing protocol for an asynchronous data transmission system

A frequency shift keyed demodulator system employs a first bandpass filter having a passband centered at a first frequency; a second bandpass filter having a passband centered at a second frequency; a first Goertzel's discrete Fourier transform processor coupled to an output of the first bandpass filter; a second Goertzel's discrete Fourier transform processor coupled to an output of the second bandpass filter; and an adder coupled to an output of the first Goertzel's discrete Fourier transform processor, and to an output of the second Goertzel's discrete Fourier transform processor.

FSK demodulator using goertzel's discrete fourier transform

A digital FM modulator (10) which functions to modulate a fixed frequency, e.g. RF, reference signal f.sub.r with an incoming AM analog signal v(t) by way of utilization of digital signal processing circuitry (14, 18, 22, 26, 28, 38, 48). The digital FM modulator 10 includes a digital encoder, e.g. a codec 14, which samples the incoming analog signal v(t) at a prescribed sampling rate f.sub.s, and converts it into a digital signal S.sub.D comprised of successive digital words representative of a prescribed parameter (e.g. amplitude) of the analog signal v(t) at corresponding, successive sampling times t.sub.i. This digital signal S.sub.D is a digital data stream which is subsequently conditioned for input to a direct, digital synthesizer (DDS) (48), which, in response to this input, synthesizes an output signal having I.sub.A and Q.sub.A components disposed in phase quadrature relation to each other. The DDS output signal components I.sub.A and Q.sub.A are coupled to respective first and second mixers (62, 68) of an I/Q hybrid circuit (59), with the I.sub.A and Q.sub.A DDS output signal components serving to modulate the reference RF carrier signal f.sub.r, which is also coupled to the mixers (62, 68) in phase quadrature, to thereby ultimately produce, after summation of the resultant IF.sub.A and IF.sub.B mixer output signals, a modulated FM signal P(t). The modulated FM signal P(t) is essentially equivalent to a modulated FM signal generated by an analog FM modulator, wherein the incoming analog signal v(t) modulates a voltage controlled oscillator (VCO).

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Haifa, Israel

Simha Erlich