Abstract: An acknowledgment paging system is described which fits within the existing infrastructure of a paging network and which provides low cost manufacture and low power operation while still enabling the acknowledgment paging over long distances. The acknowledgment paging system consists of a standard paging transmitter and a plurality of remote paging units which respond to a page using frequency-hopped spread-spectrum differential bi-phase shift keying communications. The plurality of pagers are assigned to groups with each group being assigned a separate starting location in a common, repeating pseudo-random noise code which determines the frequency hops. The grouping of pagers minimizes the collisions of acknowledgment transmissions between groups and the enables a large number of paging units to operate within a single geographic area.

Abstract: A rectangular to phase converter (201) includes a first converter circuit (201B) which limits signals to a predetermined level. A phase selector (259) selects a relative phase from the limited signals. According to one aspect of the invention, input rectangular coordinate signals are mapped to the first quadrant in a first quadrant mapping circuit (201A) before the first quadrant signals are limited and the relative phase signal is returned to the original quadrant by an original quadrant mapping circuit (260).

Abstract: A wireless local area network includes a radio transmitter/receiver for transmitting and receiving in accordance with the FCC rules for the ISM band. The receiver/transmitter supports spread spectrum frequency hopping in the 2.4 GHz ISM band and can be tuned to one of e.g. 82 different frequencies spaced at 1 MHz intervals. The radio transmitter/receiver is a low cost, low power, small size unit located on a printed circuit board in a PCMCIA form factor. Third order mixers are used in combination with a switched prescaler for a low cost and compact frequency control system capable of rapid switching of the radio between transmitting and receiving functions. No special shielding is needed between the frequency control circuitry and the receiver IF circuitry.

Abstract: A transceiver uses feedback control to monitor a transmitted continuous phase modulation (CPM) waveform, such as a spread spectrum CPM waveform, and adjust the modulation index in response thereto. Codewords are selected from a table according to a data signal and applied to a pulse shaping network. The pulse shaping network outputs a CPM waveform to a prefilter. The prefilter is connected to an FM modulator, such as a voltage controlled oscillator. In one embodiment, a correlator in the transceiver monitors the transmitted waveform during times when the transceiver is not receiving signals, and provides a correlation signal to a feedback control circuit. The feedback control circuit dynamically adjusts the gain of the prefilter, and may comprise, e.g., a second order tracking loop filter. The feedback control signal thereby tracks the amplitude of the transmitted waveform and adjusts the output gain of the prefilter so as to maintain a constant signal envelope.

Abstract: A method and apparatus for improving the phase granularity when changing the phase of a digital signal. The present invention doubles the phase shift granularity of a phase shifting system by either adding or not adding one-half unit of phase delay to the digital signal being phase shifted. When increasing phase delay is being added to the digital signal, no additional phase delay is added to the digital signal. When decreasing phase delay is being adding to the digital signal, one-half unit of phase delay is added to the digital signal. Thus, whenever a change is made between increasing or decreasing phase delay, a one-half unit phase delay is introduced which effectively doubles the phase delay granularity of the phase delay system at the point of phase delay reversal.

Abstract: A computer program product, such as a floppy disk with pre-recorded software, is provided. The computer program product is for use with a computer or processing system which is to function as a node within a network. Synchronization of a local time maintained at the node with a reference time is facilitated through execution of the prerecorded software by the node. Bursts of synchronization messages containing reference time stamps are transmitted over the network, or over a communication link, according to a predetermined protocol. The node receives and time stamps the messages. Thus, times according to a first time scale and a second time scale are obtained. The protocol defines temporal relationships between certain ones of the times. In accordance with the protocol, the node determines a difference between a first time according to one of the time scales and a time related to second and third times according to the other time scale. The node then updates its local time based on the difference.

Abstract: A method and system for allocating a set of orthogonal PN code sequences of variable length among user channels operative at different data rates in a spread spectrum communication system is disclosed herein. PN code sequences are constructed that provide orthogonality between users so that mutual interference will be reduced, thereby allowing higher capacity and better link performance. In an exemplary embodiment, signals are communicated between a cell-site and mobile units using direct sequence spread spectrum communication signals. Information signals communicated on the cell-to-mobile link channels are encoded, interleaved, and modulated with orthogonal covering of each information symbol. Orthogonal Walsh function codes of varying length are employed to modulate the information signals. Code assignments are made on the basis of channel data rates in a manner which results in improved utilization of the available frequency spectrum.

Abstract: Methods for generating code sequences that have rapid acquisition properties and apparatus which implement the methods by processing spreading codes on in-phase and quadrature channels. A first method combines two or more short codes to produce a long code. This method may use many types of code sequences, one or more of which are rapid acquisition sequences of length L that have average acquisition phase searches r=log2L. Two or more separate code sequences are transmitted over the complex channels. If the sequences have different phases, an acquisition may be done by acquisition circuits in parallel over the different code sequences when the relative phase shift between the two or more code channels is known. When the received length L codes or the length L correlation codes used to find the phase of the received codes have a mutual phase delay of L/2, the average number of tests to find the code phase of the received code is L/4.

Abstract: A vehicle communications network is provided which includes a ground translation circuit and interfacing transmitter circuits that achieve smooth current sourcing transitions. Included is a communications bus such as a J1850 having multiple-access for interfacing with a plurality of electronics, preferably within a vehicle. Each transceiver has a transmitter and receiver interfaced with the bus. The transceiver is coupled via a resistive element to the communications bus and sources current onto the bus when the transmitter output voltage exceeds the bus voltage. The added resistance advantageously reduces changes in current which may otherwise exist on the communications bus when current sourcing switches on and off.

Abstract: A method of processing wireless signal of data pulses or packets in a communication system, in which a portion of the data pulses in an individual signal are utilized to determine a rate of time shift for eliminating or minimizing the effects of Doppler shift in the intra-data pulse processing. One embodiment of the invention provides a method of utilizing the time refinement section of a JTIDS waveform for the purpose of determining an intra-burst data correction factor based upon the average shift of the midpoint of the sampled time refinement section pulses.

Abstract: The present invention relates in general to a channel CODEC to increase the transmitting effect on a communication channel of a communication system, and more specifically to a branch metric module of a viterbi decoder. The module includes an operator for operating and outputting the differential magnitude of two signals, one signal being a code word generated to perform the viterbi decode and the other being a signal transmitted through the channel. An adder sums and outputs the data which is outputted to it from the operator. A receiving code word converter converts the magnitude of any of bits by the linear sampling quantization process, and non-linearly converts it in accordance with a preestimated or predetermined format. A number of operators calculate the magnitude between two signals at the absolute value to convert the magnitude of an inputted generative code word and the magnitude of the non-linear converted receiving code word.

Abstract: The apparatus includes a demodulator (70) responsive to a first received symbol (68) associated with a first transmitted symbol (39). The demodulator has a plurality of outputs (72) and produces a first set of outputs (99). The demodulator (70) is also responsive to a second received symbol (68) associated with a second transmitted symbol (39), and produces a second set of outputs (99). A coherent detector (100) receives some outputs from the first set of outputs (99), producing an estimate of the first transmitted symbol. The coherent detector also receives some outputs from the second set of outputs (99), producing an estimate of the second transmitted symbol. A first energy value (135) and an index (101) are associated with the first estimate, while a second energy value (135) is associated with the second estimate.

Abstract: Disclosed herein are methods and apparatus for detecting the presence of a CDPD carrier in a channel of a cellular system (although the invention is broadly applicable to detecting a specific kind of carrier associated with an "overlay" system, wherein an "overlay" system is one that shares the frequency allocation of another system on a non-cooperating basis). This specification describes a spectral estimation technique for detection of a CDPD carrier. In addition, this specification describes an MMSE (minimum mean-squared error) method that improves on the spectral estimation method.

Abstract: Disclosed are digital data receivers, methods and circuitry for differentiating between signals and data packets of varying physical layer protocols and frequencies transferred over a digital burst mode communications system, such as a packet-based LAN. Transitions in a received input signal to a squelch circuit start a counter which asserts one or more signals at various predetermined times from the transition. The absence or presence of the signal when the next transition in the input signal occurs indicates whether the input signal is less than or greater than a frequency associated with a particular predetermined time interval. When a predetermined number of transitions meeting a particular frequency requirement are received, the input signal is determined to be received at a particular frequency.

Abstract: A data receiving circuit of a digital communication system which receives a transmitted input data bit column and input clock, comprising a first clock generator having a first delay that receives the input clock and outputs a first clock, a delay locked loop having secondary delay cells connected in series to each other which allow the first clock to be sequentially phase-delayed by 2.pi./2n and as a result, output secondary clocks, and which locks a phase difference between the first clock and an output of delay cell of 2.pi.

Abstract: A device is disclosed for detecting a frame synchronous signal which has been applied to a communication system for indicating a starting point of transmitted data. The frame synchronous signal detector includes a parallel converter, a detector, and a buffer. The parallel converter sequentially divides parallel data into segments. The detector compares data of each of the segments with the data of the frame synchronous signal which has been mapped, and from this comparison, precisely detects the data of the frame synchronous signal even though data having an abnormal format is inputted.

Abstract: A timing signal generator includes a demodulator for an input modulated signal to provide first and second baseband signals having a quadrature relation relative to each other. A converter is used to convert the first and second baseband signals into angle data representing a phase, and a calculator is used to calculate a difference between the phase represented by current angle data and the phase represented by previous angle data, preceding the current angle data by a 1-symbol interval. The calculator outputs data representative of the calculated phase difference. A further converter converts the calculator output data into a binary reference signal responsive to which of predetermined divided regions contains a point corresponding to the calculated difference data. Also included is a generator for generating a symbol timing signal in synchronism with the binary reference signal.

Abstract: A circuit for clock recovery from an input signal, particularly an alternating input signal formed from a data signal, the invention calling for a filter/amplifier unit made up of several series-connected resonance ampliers to be formed in a regenerative frequency filter. Unlike series-connected resonance amplifiers without feedback, the filter/amplifier unit has an overall Q-factor in the feedback loop which increases essentially linearly with the number of resonance amplifiers and their Q-factor. This enables the required high overall Q-factor to be obtained for the clock-recovery circuit with a relatively low number of resonance amplifiers with a Q-factor which is low compared with the overall Q-factor. A slope detector, a frequency mixer and the resonance amplifiers have similar assemblies so that the circuit can be designed more simply as a solid-state integrated circuit.

Abstract: The present receiver includes a radiofrequency part (RF) coupled to a limiting amplifier (SL) which is in turn coupled to a demodulation means (DM) which recovers a digital signal from a received signal obtained by modulating a carrier signal with this digital signal. The limiting amplifier (SL) has an input-output characteristic which is substantially linear for smaller input signals and which strives with a decreasing gain towards a limit value for larger input signals. Due to this input-output characteristic smaller received signals are treated linearly up to the demodulation means (DM). The latter can therefore for these signals compensate for a specific spectrum shaping of the digital signal performed before the actual modulation. In this way the receiver will perform in a nearly optimal way resulting in low bit error rates. For larger received signals the limiting amplifier (SL) is non-linear and such compensation is consequently without effect resulting for these signals in a performance degradation.

Abstract: The object of the present invention is to provide a wireless modem that performs detection with high reliability even in the case of carrier detection by analogue level, and whereby a large decrease in power consumption in standby mode can be obtained. Control unit 80 controls synthesizer 100 during transmission mode so that it transmits from antenna 200 one or two or more unmodulated carriers that have not been subjected to spectrum dispersion, at the head of the transmission preamble signal; in addition it performs on/off control of the output transmission clock pulse and reception clock pulse of clock pulse generating control unit 90, and changeover control of transmission/reception switch 53. Control unit 80 outputs a carrier detection enable signal to level comparator 75. Controlling its operation. In standby mode, control unit 80 controls synthesizer 100 and IF unit 40 such that the received unmodulated carrier can be detected by level detector 60 and level comparator 75.