Abstract: A robust encoding and decoding system of the present invention for communicating binary information using angular modulation system is disclosed. Binary information to be transmitted is data words consisting of 8 data bits, a parity bit, and two additional coding bits at the end of the data word. A transmitter transmits the data words using a binary phase-shift keying (BPSK) modulated signal. The receiver compares the phase of incoming BPSK modulated signal against a local reference signal and records the phase characteristics of the BPSK signal. The receiver also records the amplitude of the recovered data signal. The receiver demodulates and decodes the BPSK signal using a rotating frame of reference that tracks the current phase of the recovered data signal. The receiver tests the parity bit of each word to detect errors. If an error is detected, the receiver attempts to correct the error using the record phase and amplitude information.

Abstract: A power line communications analyzer (PLCA) provides a signal strength metering system and selectable signal attenuation functions for adjusting the transmitting unit's attenuation and measuring error rate without the need for a user to be present at both the sending and receiving locations under test. Each PLCA is coupled to a power line communication network via an electrical outlet and power lines. In actual operation, one of the PLCAs acts as a data transmitter and the other PLCA acts as a data receiver. The mode of operation of the PLCA can be dynamically altered during operation of the system. The PLCA comprises control logic that receives command inputs from a keypad, generates data packets for transmission on the power line communication network, receives and analyzes data packets received from the power line communication network, detects the power line signal and/or noise level and drives the LED display accordingly, and displays packet transmission information on an LCD display.

Abstract: A power supply for a node that transmits data onto a power line. A DC supply and capacitor supply power to the node where the output current of the DC supply may be less than required for transmission by the node. When the voltage on the capacitor drops to Vmin transmissions are stopped allowing the capacitor to recharge. A timing circuit is used to determine when to begin transmission to compensate for variables in the node such as line voltages and part tolerances.

Abstract: A power supply for operating from a switched leg of an AC power line and for powering a transmitter is described. A switch provides current during the beginning of each AC half cycle to an inductor and charges a capacitor. When the switch is open, the inductor continues to charge the capacitor. During the time that the inductor is coupled to that AC line, the switched leg is open. For instance, the signal used to close the switch also prevents a triac in the switched leg from conducting. When the voltage on the capacitor drops to a predetermined level transmission from the transmitter is inhibited. A timing circuit is used to determine when to begin transmissions to compensate for variables in the node such as line voltages and part tolerances.

Abstract: In a communications system, an apparatus and method for detecting a valid signal from noise. An adaptive threshold is used to qualify a received signal. The adaptive threshold is set according to the number of false detects occurring within a given time interval. The number of false detects is initially determined by a quick qualification process. This initial number is subsequently adjusted by a more accurate qualification process. The transmitted signal is modulated with a particular pattern. Upon receiving the signal, it is demodulated to retrieve that pattern. The demodulated pattern is correlated against multiple reference patterns and combined to provide a measure of peak correlation that is independent of pattern phase. Furthermore, a tone detector is used to distinguish valid signals from interfering tones. Two different types of detection methods are performed in parallel. One is based on the energy of the received signal, whereas the other is based on the correlation of the received signal.

Abstract: An apparatus for snubbing or blanking digital signals representing a band of signals that includes an encoded carrier signal transmitted over a power line. An average signal level is compared with the instantaneous signal level to develop a blanking circuit control signal. Additionally, snubbing occurs in the circuit which determines the average signal level to prevent noise from building-up the average signal level. A hold-off signal is used in this circuit to prevent the average signal level from being latched permanently low. A unique infinite impulse filter subtracts out the D.C. offset thereby improving the dynamic range of the blanking. Additionally, the average signal level is used by AGC logic to control the gain at the front end of the apparatus. The state and switching of the AGC is controlled to minimize errors.

Abstract: An improved transceiver for power line communication using a spread spectrum signal. The amount of correlation for each bit in a word is determined. If a parity error occurs, the state of the bit with the weakest correlation is changed.

Abstract: A method and means for for recovering data in a spread spectrum communications system. The present invention includes a method and means for providing a sync window time period. The sync window is set to encompass the correlation values which are generated one baud time from the previous recovered data bit. The present invention also determines the peak correlation value within the sync window and the location in time within the sync window that the peak correlation value occurs. The present invention also provides a polarity window time period. The polarity window occurs during the sync window. The present invention decodes the data according to the direction of the peak correlation and whether the peak occurred within the polarity window. The sync and polarity windows are then set to occur, such that the peak correlation of the next baud falls within the next instance of the sync window. In this way, data can be recovered continuously.

Abstract: In a power line communication apparatus, data is redundantly transmitted on a first and a second carrier where the carriers are separated by a predetermined number of Hz. In the receiver two channels are used, one for each of the carriers. The noise level in each channel is independently determined. A switching network is used to allow the selection of the channel with the lesser noise or if the noise is approximately equal in both channels, the signals in the channels are combined.

Abstract: A power line communication (PLC) apparatus wherein transmission mode information is encoded into each data packet while maintaining immunity from single bit errors. In the present invention, a power line communication system includes a transmitter/receiver (i.e. transceiver) which is coupled to a power distribution network. Data is transmitted through the power line by the transceiver in packets. The transceiver includes a preamble generator which creates a preamble for each of the data packets and a preamble decoder that decodes the preamble of a data packet and determines word sync for the packet. The preamble generated by the preamble generator consists of a carrier detect interval, a carrier sync interval, a bit sync interval, and a word sync pattern. The transceiver may select either BPSK or QPSK transmission modes on a data packet by data packet basis by encoding information into the packet preamble.

Abstract: A method and means for for recovering data in a spread spectrum communications system. The present invention includes a method and means for providing a sync window time period. The sync window is set to encompass the correlation values which are generated one baud time from the previous recovered data bit. The present invention also determines the peak correlation value within the sync window and the location in time within the sync window that the peak correlation value occurs. The present invention also provides a polarity window time period. The polarity window occurs during the sync window. The present invention decodes the data according to the direction of the peak correlation and whether the peak occurred within the polarity window. The sync and polarity windows are then set to occur, such that the peak correlation of the next baud falls within the next instance of the sync window. In this way, data can be recovered continuously.

Abstract: A transceiver for transmitting and receiving spread spectrum signals having an adaptive threshold for distinguishing between valid receive data signals and noise. The transceiver includes a transmitter for transmitting spread spectrum signals and a receiver for receiving spread spectrum signals. A correlator correlates a received signal against an expected receive pattern. The correlation of the received signal is compared to a threshold value. If the correlation exceeds the threshold value, a carrier detect signal is generated. The number of false carrier detect signals occurring within a pre-determined period of time is determined. The threshold value is varied according to the number of false carrier detects.

Abstract: An improvement in an apparatus which uses a carrier detection threshold level for detecting a carrier signal modulated with binary data. The threshold level is dynamically changed and generally seeks a level above the background noise. The threshold level is maintained constant when the detected signal exceeds the threshold level. An evaluation circuit is able to examine the detected signal to determine whether it contains data or only noise, and if it contains only noise, a possible trapped condition is avoided by raising the threshold level to a level higher than the background noise.

Abstract: In a power line communications apparatus an improvement for blanking or snubbing impulse noise. The impulse noise is detected and used to snub the detected signal. The duration of the snubbing pulses is controlled to assure complete blanking of noise including the trailing noise signals following a main noise pulse which may not otherwise be detectable. Also, the number of snubbing pulses which can occur are limited to prevent too much energy from being snubbed during any given baud period.

Abstract: An error detection and correction method and apparatus is described which permits the correction of double errors using a (15,11) Hamming code and a parity bit. The Hamming code and parity bit allows the detection of double errors. A modulated waveform carrying the binary data is examined for anomalies such as noise pulses. A hint signal is generated based on the anomalies which points to a suspect bit. The state of this bit is changed to correct for double errors.

Abstract: An interface between a network cell and an associated network communications transceiver passes both network information and command/control information between the cell and the transceiver. The interface is designed to minimize the number of control lines between the cell and the transceiver. A protocol between the two devices is established to deal with configuration and error reporting as well as the passage of network data. This protocol consists of the cell and the transceiver each exchanging 8 bits of status and 8 bits of data simultaneously and continuously at rates up to 1.25 MBPS. Only a single version of cell firmware is required since a fixed amount of configuration information is sent from the cell to the transceiver, and a fixed amount of status information is returned from the transceiver to the cell.