Abstract: An OCDMA communication system in which channel signals are bandwidth spread according to a PN code and each channel is identified by a selected one of a set of RW code accesses. The set of RW codes is reduced by predetermined one (preferably RW.sub.0). Each transceiver has acquisition and tracking circuitry which search for a null (e.g., the unsent RW access code) falling lower than a predetermined threshold value and synchronizing tracking on detection of the null.

Abstract: An existing TDRSS satellite communication system is incorporated, together with low-power ground-based remote transceivers of special design, and additional beam forming and steering elements at the ground terminals, to make possible digital communication between low power field transceivers and satellite ground terminals. The satellite communication system transmits to its ground terminals a composite signal, comprising amplified, phase-coherent signals received by an array of broad-coverage antennas on the satellite. The field transceiver transmits a pseudonoise coded signal spread across all or a portion of the satellite's receive bandwidth. At the ground terminal, the downlinked composite signal is processed by a beamformer to define a narrow, high-gain beam between the satellite and low-power transceiver. Signal processing gain and beamformer gain in combination serve to elevate the received, demodulated signals well above the noise level at the receiver.

Abstract: The present invention is based on novel implementation techniques which makes orthogonal CDMA practical in a short range mobile telephone environment where significant multipath fading exists. Specifically, this invention provides novel techniques for establishing the time base, frequency, and power control necessary to achieve orthogonality. Use of a high power sounding burst on the outbound link permits: 1) antenna diversity selection to minimize the probability of a faded condition, 2) local frequency locking at the subscriber terminal which avoids the requirement for a costly precision frequency standard, and 3) essentially instantaneous inbound power control based on the outbound receive signal level. This is effective since time division duplexing is used and both transmission and reception take place on the same frequency. With the short frame structure and unique placement of the sounding burst the correlation between the outbound and inbound path losses is very high.

Abstract: A modulator system for generating a plurality of individual modulated RF signals and combining them and transmitting them in different frequency channels. The invention provides a practical method and apparatus for generating and combining a multiplicity of CDMA signals in several radio channels using digital circuitry. Further, several such band segments can be generated in parallel and combined to cover a large bandwidth. The invention generates this multiplicity of signals and combines them at baseband using all digital techniques. The advantage of this approach is a great simplification in hardware and improvement in reliability, as well as flexibility.

Abstract: A radio transmitter having a source of first signals for radio transmission, includes a modulator for modulating the first signals on an intermediate carrier frequency second signal to produce a third signal. A charge coupled device (CCD) is connected to receive and process the third signal in the absence of digital waveform shaping and digital-to-analog conversion. The CCD has a sampling rate which is a multiple of the intermediate carrier frequency second signal to provide aliased fourth signal components that are spectrally spaced in accordance with the multiple and provide upconversion to a fifth signal. A bandpass filter receiving the fifth signal is centered around a selected aliased signal component and a power amplifier/antenna means coupled to receive said selected aliased component for transmission. In a preferred embodiment, the multiple is 4. Moreover, the tap weights of the CCD are selected to provide wave shaping of the aliased fourth signal components.

Abstract: A high speed bidirectional cable transmission system for CATV and other television systems includes unidirectional transmission of video signals from a head end unit to a plurality of transceivers or subscribers connected to a transmission line. The head end unit encodes voice data using QPSK encoding and time division multiplexing of the encoded data in a plurality of frequency bands to the subscribers. Each subscriber attached to the cable for receiving continuous transmission of voice and video data is assigned an identification number and at least one voice channel for selectively accessing data. Each subscriber includes a transmitter for transmitting voice data on the cable to the head end unit using time division multiple access transmission of bursts of data in a plurality of frequency bands.

Abstract: The hub station of a network receives a multiplicity of signals in different frequency channels and possibly on different antennas. The individual signals to be demodulated may coexist in a radio frequency channel using FDMA, TDMA, or CDMA or other signal types or combinations thereof. The received frequency band is divided into subbands which are all translated to baseband and distributed to the backplane of one or more demodulator chassis (each of which contains many demodulators). In this way, any demodulator may be connected to any signal. Relatively large segments of the input bandwidth are translated to baseband. These segments are then digitized and further band segmentation is performed digitally. In this way, the digitation and switching functions are almost all done with digital hardware. This affords considerable advantage in hardware cost, size, and reliability.

Abstract: A location determination system and method in which mobile receiver units are in an area of at least three fixed commercial television stations, each television station broadcasting standard television signals, including horizontal, vertical and chrominance burst synchronizing signals. The standard television signals from selected ones of said television station are received at the mobile receiver unit and the times of arrival synchronizing signals of the selected ones of the television stations, respectively, are measured to produce mobile receiver unit signals corresponding thereto. A fixed reference station receives the television signals and detects any frequency and wavelength drift in the standard television signals from each of the fixed commercial television stations, respectively, and produces reference receiver correction signals.

Abstract: This invention relates to a novel receiver architecture, the Charge-Coupled-Device Integrated Receiver (IR), which simplifies electronic circuitry requirements and reduce baseband processing rates through efficient signal processing. The focus of this receiver's design is its use of Charge-Coupled-Device (CCD) technology. By using CCD's, in conjunction with other key technologies, to implement the signal processing techniques disclosed herein, it is possible to provide a receiver that is suitable for a wide range of applications (e.g., communications, sonar, radar, etc.). Information is presented which outlines the fundamental receiver architecture that is appropriate for a wide range of commercial services (e.g., AMPS, NAMPS, Digital Cellular, GSM, PCS, ISM, CT1, CT2, etc.) Furthermore, tile versatility of this architecture makes it suited for uses ranging from simple AM/FM receivers to complex high-order modulation TDMA/CDMA receivers.

Abstract: A received carrier containing pseudonoise-modulation and with additive noise is correlated with a local pseudonoise signal having the same binary sequence but an unknown time delay. A second correlation is performed using a signal derived from the local pseudonoise signal (in a preferred embodiment, its time derivative). The bandpass filtered outputs of the two correlators are used as inputs to a third correlator, whose low-pass filtered output controls the time delay of the local pseudonoise signal to form a delay lock loop in which the delay may be measured and low-frequency modulation extracted from the signal. This delay lock loop has improved noise rejection as compared to prior art loops, and does not experience the "cycle slip" effects observed in coherent delay lock loops of conventional design.

Abstract: An air traffic surveillance and communication system for air traffic controllers, includes a plurality of ground based first radio transceivers located in specific geographic sectors, respectively, and having a first frequency channel for supporting party-line digital voice and a second frequency channel dedicated to supporting a digital data channel for down-linking dependent surveillance data and for both up-link and down-link data communications. The first and second frequency channels are paired such that each time a frequency change is commanded by the ground both the first and second frequency channels will be automatically tuned to a new air-ground frequency paid. The system also includes a plurality of aircraft based second digital radio transceivers, one located in each aircraft. Each second radio transceiver has corresponding first and second frequency channels and a navigational data source on each aircraft.

Abstract: The present invention relates to a no outage GPS/AM position finding system wherein a GPS system having a plurality of satellites transmits time and location data over radio frequency signals to enable a mobile GPS receiver station on the ground to determine its position, and a cellular telephone is carried with the mobile GPS receiver, traveling in range of a plurality of conventional ground based amplitude modulated (AM) transmitters for transmitting AM signals. Each mobile GPS receiver station includes phase detection means for simultaneously receiving a predetermined number of the AM signals, and measuring the changes in phase of each of the AM signals as the mobile GPS receiver travels, and deriving therefrom an AM position signal. A reference station for receiving the GPS and AM signals provides correction signals via a cellular telephone network which receives and transmits the correction signals to the mobile GPS receiver station.

Abstract: An adaptive filter or equalizer for digital data communication includes, a first cascade circuit connected to operate as a digital finite impulse response (FIR) filter, the first cascade circuit having a first plurality of input taps for application of filter weighting signals thereto, a single input for samples of input data, and an output for filtered data. A second cascade circuit, which has the inverse canonical form, has a second plurality of input taps for receiving signal samples of input data, a single input for receiving error signals, and an output for yielding a succession of weighting signals. A sequencing circuit applies data signals to successive cascade stages of the second cascade circuit in a time sequence which is the reverse of that of the weight signals applied to the plurality of input taps of the first cascade circuit, such that the second cascade circuit functions as a weighting signal generator for the first cascade circuit.

Abstract: A modulator for data transmitted in a reverse channel or upstream spectrum in a cable transmission system requires a single frequency translation from baseband to a selected RF channel, thus eliminating conventional intermediate frequency (IF) translation. The modulator requires fewer components than the conventional modulator while eliminating nonlinearity, noise, and delay introduced by the IF upconversion. In a preferred embodiment, the modulator includes a serial to parallel differential quadrature phase shift keying encoder with transversal FIR filters and interpolation filters connecting the phase shift keyed data to a single mixer stage for directly translating the baseband signal to an RF (e.g., 5-40 MHz) channel spectrum.

Abstract: A position, time location receiving system deriving its output position estimates from received inputs from a distributed array of pseudonoise multiplexed transmitter channels at determinable spatial positions. The receiving system has a plurality of delay lock loops, one for each transmitter channel. Control signals for the delay lock loops of each transmitter channel are derived from a current estimated location vector (x, y, z) and time.

Abstract: The present invention is directed to novel implementation techniques which makes orthogonal CDMA practical in an a short range mobile telephone environment where significant multipath fading exists. Specifically, novel techniques for establishing the time base, frequency, and power control necessary to achieve orthogonality. Use of a high power sounding burst on the outbound link permits: 1) antenna diversity selection to minimize the probability of a faded condition, 2) local frequency locking at the subscriber terminal which avoids the requirement for a costly precision frequency standard, and 3) essentially instantaneous inbound power control based on the outbound receive signal level. This is effective since time division duplexing is used and both transmission and reception take place on the same frequency. With the short frame structure and unique placement of the sounding burst the correlation between the outbound and inbound path losses is very high.

Abstract: A global positioning system (GPS) in which a plurality earth orbiting satellites transmit position information to mobile radio stations on earth, is provided with a separate source satellite position data broadcast digital channels and one or more dial-up service separate communication channels (selected from a data link supported by terrestrial cellular telephone and other radio packet data services) for assisting the mobile radio station to access position information from the satellites. A controller is coupled to the mobile radio station for connecting to the separate communication channel for extricating the satellite position data via separate communication channel. The controller includes a microprocessor for processing the satellite position data to enable the mobile radio station to rapidly locate and access position information from said earth orbiting satellite. A unique system for processing the data is disclosed.

Abstract: A portable cellular telephone system including a stationary transceiver for radio communication with a plurality of mobile transceivers within a geographic cell, a mobile transceiver within said geographic cell and having sufficient power to communicate with said stationary transceiver, and a portable transceiver of limited size for personal transport and use. The portable transceiver communicates with the mobile transceiver by spread spectrum techniques, and the mobile transceiver communicates with the stationary transceiver by frequency modulated radio transmission or by digital radio transmission.

Abstract: In a Viterbi decoder including an add-compare-select (ACS) processor, speed is enhanced without loss of performance by maintaining a dynamic cumulative metric range for computed state metrics. Current state metrics are added to new branch metrics to obtain two computed metrics, and the smaller of the two computed metrics is stored along with previously computed state metrics. The stored state metrics are compared with a selected scale factor, for example one-half maximum scale factor, and all current state metrics are rescaled when the minimum stored metric value exceeds the selected scale factor.

Abstract: A digital audio broadcasting system that is capable of providing a large number of high quality stereophonic channels to mobile receivers in an environment with severe multipath delay and fading. Optimum combination of frequency and time diversity to guarantee robust performance in the mobile channel, with its multipath delay and frequency-selective fading effects. The system is based upon a dynamic single channel per carrier assignment of each stereo channel to many carriers. Intersymbol interference degradations caused by multipath delay are mitigated via an adaptive equalizer in the receiver. This dynamic single channel per carrier system preserves the simplicity inherent in the single channel per carrier assignment while it incorporates the ability to address frequency-selective fading by providing substantial frequency diversity.