Abstract: A method for calibrating an impulse radio distance measuring system comprising an impulse radio transceiver by conducting a pulse through a transmit receive switch to an antenna, receiving return energy which has been discharged across the transmit receive switch, determining a time of arrival of the return energy. The return energy is comprised of two distinct pulses, one of which represents discharge of the transmit switch as the original pulse travels to the antenna, the second represents energy reflected from the antenna and again discharged across the transmit receive switch while the switch is in the transmit position. The timing of the un-reflected energy is determined then the timing of the reflected energy relative to the un-reflected energy is determined through auto-correlation of the time domain scan of the received composite waveforms.

Abstract: A communication system from maintaining synchronization includes a communication signal comprising a carrier and a data signal that is sent from a transmitter to a receiver which includes a phase lock loop. The receiver compares the output of a Viterbi decoder with the output of a quick decision circuit. The Viterbi decoder, which incorporates traceback, determines the minimum aggregate Euclidean distance for multiple symbols. The quick decision circuit determines the minimum Euclidean distance for a single symbol without decoding the symbol. A delay circuit is placed in series with the quick decision circuit to compensate for the traceback delay in the Viterbi decoder. If the difference in the output signals of Viterbi decoder and the quick decision circuit is greater than a predetermined threshold, the phase error signal in the phase lock loop is prevented from updating the phase lock loop filter.

Abstract: In the invention, it becomes possible to extract all clock information data processing data by simultaneously comparing first, second and third voltage levels to each data bit in clocked time increments wherein the magnitude of the increments is such that each binary data bit is in two of the three voltage levels and all data bits change each clock cycle, so that reconstructed signals of the binary information only may then be assembled based on a signal amplitude that is greater than a low threshold value that is less than the transition between the first and the second of the voltage levels and is less than a high threshold that is greater than the transition between the second and the third voltage levels. The reconstructed data signals are further shaped to be precise in timing, free of skewing and within the system clock.

Abstract: The receiver receives the standard frequency signal that includes a time code. A sampling unit samples one bit of the received signal at 32 positions. A smoothing unit smoothens the result of sampling by dividing the 32 positions in two to four intervals and determines a value of the received signal in each interval. A waveform determining unit determines waveform of each bit of the received signal based on the value obtained in the smoothing unit. The decoding unit extracts the time code based on the determined waveform. A time unit correct the time based on the extracted time code.

Abstract: The method of noise-immune information transmission of the present invention permits to increase the communication channel capacity without reducing the noise immunity of information being transmitted. In this method, informational digital samples are transmitted in the form of analog signal supplemented with a redundant information signal.

Abstract: An apparatus and a method for symbol decoding of baseband data in a wireless communications network is disclosed, and specifically CCK subsymbol prediction and symbol demodulation that occurs at 5.5 Mbps or 11 Mbps. The apparatus is configured to demodulate or predict the data differently, depending on the modulation rate. If the data was modulated at 11 Mbps, the ?3 rotator is rotated through each of its possible phase values and symbol correlation takes four clock cycles to complete. If the data was modulated at 5.5 Mbps, ?3 is not rotated with a set value of 0 within the correlator architecture, thereby saving power and reducing symbol correlation and subsymbol prediction to a single cycle while in such transmission mode.

Abstract: All practical communication channels impose some type of corruption on received data through inter-symbol interference (ISI). ISI corruption is particularly acute in high-order constellation transmission. Although ISI effects of high-order constellation transmission are very large on average, some symbols may be received that suffer relatively low levels of ISI. These symbols are “reliable symbols” and can be used to provide blind estimation of the ISI coefficients. Once the ISI effects of a channel are known, all captured signals may be corrected.

Abstract: Detecting a boundary between training sequences in a transmission is an important operation. In many communications systems, there are no special boundaries or markers to denote the end of one sequence and the beginning of another. Correlation has been a commonly used technique to detect sequences and a fall in the correlation can be used to indicate such boundaries, but classical correlation can be slow and a significant portion of the new sequence is received prior to the boundary being detected. A method and apparatus is presented that allows rapid detection of the boundary and only a small amount of the new sequence needs to be received prior to the detection of the boundary. Additionally, the method and apparatus can be used to detect the presence of a transmission on the communications medium.

Abstract: An apparatus and method for estimating phase information, including a matched filter that outputs converted synchronization signals, based on received data, and converted information of the received data; a phase estimator, having a plurality of averagers, that outputs the phase information based on the received data, a code generated from a code generator, and the converted synchronization signals outputted from the matched filter; and a CPU that inputs the converted synchronization signals outputted from the matched filter into the plurality of averagers and initializes the averagers.

Abstract: A fast equalization technique is disclosed for systems using high-order constellations where symbols have been corrupted by data correlated noise (ISI). The technique permits ISI estimation to begin immediately upon receipt of captured samples. Training symbols are not required for the operation of the equalization technique. ISI estimation is weighted in accordance to a reliability factor of each captured sample.

Abstract: The method determines the position of a predetermined known signal segment in a transmitted signal received in a receiver by means of a correlation between the received signal and a representation of the known signal segment stored in the receiver. The known signal segment is stored in the receiver as an erroned hierarchical sequence that is the sum of a hierarchical sequence and an error sequence. The correlation is formed as a sum of a correlation between the received signal and the stored hierarchical sequence and a correlation between the received signal end the stored error sequence.

Abstract: A weight vector of a precedent frame calculated by a weight vector calculator (4) and stored in a memory (3) is applied to a signal received through a plurality of antennas (ANT1, . . . ANTn) for removing an interference wave component. A synchronous position is detected from the signal subjected to removal of the interference wave component by a method of correlation synchronization, and supplied to the weight vector calculator (4). The weight vector calculator (4) executes calculation of a weight vector with the detected synchronous position as a start position. Thus, when signals of the same frequency are received in a CS in an overlapping manner, the synchronous position of a signal received from a desired PS can be correctly specified.

Abstract: A sync mark detector identifies a sync mark in an incoming bitstream of a communications channel. A bit comparing circuit compares the sync mark bit-by-bit to the incoming bitstream if channel irregularities do not exist. A symbol comparing circuit compares the sync mark symbol-by-symbol to the incoming bitstream if channel irregularities do exist. The bit comparing circuit implements a bit level matching rule. The symbol comparing circuit implements a symbol level matching rule. The bit comparing circuit generates a sync mark found state when the bit level matching rule is satisfied. The symbol comparing circuit generates a sync mark found state when the symbol level matching rule is satisfied. Post coding such as NRZ, INRZI, or NRZI can be used.

Abstract: A positioning apparatus for determining a present position of a mobile station by using radio waves coming from a plurality of base stations arranged within a communication area is provided. The positioning apparatus receives the radio waves coming from the plurality of base stations to generate reception signals corresponding to the respective radio waves, and determines propagation ranges of the radio waves coming from the respective base stations. The apparatus further derives propagation ranges of direct waves coming from the respective base stations from the determined propagation ranges. Then, the present position of the mobile station is determined by performing positioning operation using the derived propagation ranges of the direct waves.

Abstract: A 64-ary QAM (Quadrature Amplitude Modulation) demodulation apparatus and method for receiving an input signal Rk(Xk,Yk) comprised of a kth quadrature-phase signal Yk and a kth in-phase signal Xk, and generating soft decision values ?(sk,5), ?(sk,4), ?(sk,3), ?(sk,2), ?(sk,1) and ?(sk,0) for the input signal Rk(Xk, Yk) are disclosed. A first soft decision value generator receives the quadrature-phase signal Yk of the received signal Rk and a distance value 2a between six demodulated symbols on the same axis, and generates soft decision values ?(sk,5), ?(sk,4) and ?(sk,3) for sixth, fifth, and fourth demodulated symbols. A second soft decision value generator receives the in-phase signal Xk of the received signal Rk and the distance value 2a between the six demodulated symbols on the same axis, and generates soft decision values ?(sk,2), ?(sk,1) and ?(sk,0) for third, second and first demodulated symbol.

Abstract: Techniques to estimate the frequency response of a wireless channel in an OFDM system. In one method, an initial estimate of the frequency response of the wireless channel is obtained for a first group of subbands based on a pilot transmission received via the subbands in the first group. An estimate of the impulse response of the wireless channel is then derived based on the initial frequency response estimate. An enhanced estimate of the frequency response of the wireless channel is then derived for a second group of subbands based on the impulse response estimate. The first and second groups may each include all or only a subset of the usable subbands. Subband multiplexing may be used to allow simultaneous pilot transmissions by multiple terminals on their associated groups of subbands.

Abstract: Orthogonal frequency division multiplexing (OFDM) receiver embodiments of the invention provide data demodulator synchronization by finding the end of the short preamble in an IEEE-802.11a burst transmission. This method exploits the fact that there are certain symmetries in the long-preamble that can be used to determine synchronization. The long-preamble sequence is composed of a guard interval (GI) and two long-preamble symbols; the GI is the last 32 samples of the long-preamble symbol. The 32nd sample of the long-preamble acts as a “pilot” or “anchor” sample in that the previous N and subsequent N samples are complex conjugates, or conjugate “mirror” vectors. Due to the periodicities of the long-preamble, this property repeats every 32 samples. No other samples in the long preamble exhibit this property. Coherent combining is used in one embodiment for robustness.

Abstract: An apparatus and method for simultaneously processing each of a plurality of carrier signals having data modulated thereon, wherein a complete data stream is formed by extracting at least portions of at least two of the modulated signals and combining the extracted portions. Each of the portions of the complete data stream comprises a plurality of packets having associated with them respective stream identification and sequence codes, where the stream identification identifies the complete bit stream to be formed, and the sequence codes identify the order or position within the complete bitstream that the associated data packets should be inserted.

Abstract: A communications channel detector which determines the availability of a desired type of communications channel in a communication system having at least one communications channel, the communications channels including data streams comprising a number of data symbols. The channel detector includes a phase detector, a phase comparator coupled to the phase detector, and a phase correlator coupled to the phase comparator. The phase detector is configured to provide a plurality of phase measurements for at least two consecutive data symbols comprising a selected one of the communications channels. The phase comparator is configured to determine the phase differences between the obtained phase measurements. The phase correlator is configured to determine the whether or not the determined phase differences exhibit a predetermined phase difference profile.

Abstract: A system for detecting a burst in a wireless communications system. A signal strength indicator indicates the strength of an incoming signal representative of incoming packets. A signal strength change detector detects changes in the signal strength of the incoming signal. Signal strength detection logic determines if a change in signal strength of a predetermined magnitude has occurred. A pattern detector detects patterns of symbols, or symbol estimates, in the incoming signal to determine if a predetermined pattern of symbols is present. Burst detection logic signals detection of a burst if the signal strength detection logic determines that a change in signal strength of predetermined magnitude has occurred, and the pattern detector determines that a predetermined pattern of symbols is present.

Abstract: The invention provides a method of operating a communication system. A channel matrix of a gain and phase between each transmit antenna and each receive antenna of the communication system is provided. At least one receive weight vector is computed as a function of the channel matrix and at least one of transmit weight vectors. An updated transmit weight vector is computed as a function of the transmit weight vector, the receive weight vector, the channel matrix.

Abstract: A digital passband matched filter is automatically adapted to a carrier wave ? in accordance with a frequency offset of the carrier wave, to obtain a passband digital signal having no frequency distortion due to the frequency offset. Thus, a receiver in which drawbacks such as decrease of SNR and increase of circuit complexity caused by the fixed baseband/passband matched filter is obtained. Since a cosine wave generating section operates in a carrier wave frequency restoring mode and a carrier wave frequency adaptive mode, respectively, a single cosine wave ROM table can be used regardless of the respective operating modes, thereby reducing circuit complexity. Since the digital passband matched filter acts to renew the filter coefficients adapted to the carrier wave adaptive mode only, power consumption required to operate the filter can be minimized.

Abstract: A digital signal detector converts quantized modulation signals to digital data according to a plurality of discriminating conditions which are set by shifting phases, which are to be boundaries of discrimination, from each other. Predetermined data in the digital data are combined so that the phases used for discriminating the data rotate in time series, thereby constituting a plurality of comparison data. When a plurality of comparison data strings coincides with expected data strings, predetermined data strings can be detected. Since a plurality of comparison data strings corresponding to a plurality of frequency differences are compared with expected data strings by a plurality of discriminating units, data strings with frequency differences can be simultaneously detected, which results in shortening the time required for detection.

Abstract: Provided is a circuit that has a simple circuit configuration and can detect zero values in a 1-bit digital signal irrespective of a recording medium such as SACD. DSD data forming the 1-bit digital signal are successively sent to a shift register (1) whose number of stages corresponds to the number of bits of an idle pattern such as “101010101” which appears when assuming a zero value. For example, the shift register (1) is an 8-bit shift register. An adder (2) sums up the values at each stages of the shift register (1). A zero decision circuit (4) produces an output indicating decision of zero if the sum value is half of the number of bits. A counter (5) keeps counting while the output indicating zero decision is being delivered. If the count value of the counter exceeds a given value, the counter produces an output indicating detection of a zero value.

Abstract: In a communication system in which an incoming signal is pulse shaped prior to detecting the information bearing point of the signal, processing overhead can be significantly reduced by only processing the sample points corresponding to the information bearing point and two points bounding the information bearing point. During signal acquisition, the signal is over sampled and the pulse shaping filter processes every sample point, or every Nth sample point in the case of down sampling. Once the sample point corresponding to the information bearing point is determined, the pulse shaping filter can be instructed to only process the sampling corresponding to the information bearing point and two neighboring samples. The system and method is adaptive, in that the samples that are processed can shift as the information bearing point shifts relative to the sample points. This is accomplished by re-synchronizing the timing of the received slot.

Abstract: A method (500) and a mobile station (160) for reporting multi-path signals based on a report window are described herein. The mobile station (160) may determine a distribution of a plurality of multi-path signals observed by a receiving unit (220) within the mobile station (160). The mobile station (160) may determine a report window based on the distribution. Based on the report window, the mobile station (160) may report at least one of the plurality of multi-path signals.

Abstract: Methods and apparatuses for iterative parameter estimation are described. The iterative parameter estimation includes performing a first estimation of a first portion of a signal to obtain first parameters of the portion of the signal, wherein the signal contains no known data symbols. The first portion of the signal is demodulated using the first parameters to recover data symbols. The demodulated first portion of the signal is checked to confirm correct demodulation of the first portion of the signal. A second estimation of the first portion of the signal is performed using the recovered data symbols to obtain second parameters of the first portion of the signal. Then, a second portion of the signal is demodulated using the second parameters when the first portion of the signal is correctly demodulated.

Abstract: A wireless network is disclosed including at least one base station and a plurality of assigned terminals for exchanging user data and control data. The base station is arranged for transmitting the start time of at least one signaling sequence of at least terminal. For evaluating the signaling sequences transmitted by the terminals, the base station includes a device for correlating a received signaling sequence and for detecting the pulse evolving from a received and correlated signaling sequence. A terminal generates a signaling sequence by folding two code sequences.

Abstract: The invention relates to a monitoring method and monitoring arrangement, which receives a parallel-mode signal transferred to the arrangement by using a clock signal. The monitoring arrangement comprises a counter counting clock signals, a monitoring means, a control means, a second means and a first means where the parallel-mode signal is transferred by using the clock signal, the signal being converted to seemingly serial mode in the first means which transfers the signal it has converted to serial mode to the first means one bit at a time by using the above mentioned clock signal. The first and second means transfer their seemingly serial-mode output signals to the monitoring means which searches the received signals for a predetermined bit pattern where the control means locks to. On the basis of the number of the clock signals it has counted, the counter defines the signal point to be monitored.

Abstract: An apparatus for detecting the signals of transmission diversity based on space-time coding is disclosed. The apparatus and method for detecting signals of space-time coding performs linear interpolation and linear filtering to calculate the channel estimate of each transmission symbol from the channel estimate of each slot, thus providing the correct channel estimate even in a channel with considerable fluctuation. Further, the output control with estimation of SIR only passes a proper output of the demodulating and detecting circuit to improve the signal to noise ratio, maintaining enough communication quality even in a bad communication environment.

Abstract: A digital signal of which input data has been segmented as block each having a predetermined data amount and highly efficiently encoded along with an adjacent block is decoded, edited, and then highly efficiently encoded. A delay that takes place in such signal processes is compensated. Thus, part of a digital signal that has been highly efficiently encoded digital signal can be edited.

Abstract: An SIR information extracting section 106 extracts SIR measured at a communication terminal from the received data, and a fluctuation amount calculating section 109 calculates a fluctuation amount of SIR between time at which the communication terminal has measured SIR and transmission starting time of DSCH data using a TPC command, and a. transmission system determining section 110 adds the SIR fluctuation amount calculated in the fluctuation amount calculating section 109 to the SIR measured at the communication terminal and estimates SIR of DSCH data so as to determine an optimal transmission system of DSCH data according to the estimated SIR.

Abstract: A method and a device for providing timing recovery in a multicarrier transmission system is provided. The data derived timing recovery apparatus with the timing error controller adjusts the sampling rate at the receiver. The data derived timing recovery apparatus uses decision directed carrier phase errors to calculate a phase error. The timing error controller adjusts the sampling rate at the receiver in accordance with the phase error.

Abstract: An optical coding system is provided for a data transmission device with at least one laser transmitter and at least one laser receiver. The laser transmitter has a laser device and a code generator, and the laser receiver a detector device and an evaluation circuit. The detector device is designed for detecting a burst sequence (B1, B2, B3, . . . ), wherein the length d of the pulses of a burst is greater than 400 ns, and the length D of a burst consisting of a number b of pulses is less than 1000 &mgr;s.

Abstract: A receiver (10) achieves more reliable detection of signals transmitted by Direct Sequence Spread Spectrum Transmission by correlating received signals with a separate of N symbol patterns via N detector stages (181-18N). A maximum peak power detecting mechanism (241-24N, 261-26N and 28) detects which of the N correlated symbol patterns has a maximum peak power, as well as the identity of each of the N patterns actually received and an index of the peak power in each symbol. A computing mechanism (30, 32 and 34) computes a running power average of the received signals, while a ratio computing stage (36) computes the ratio of the largest peak power of the N correlated symbol patterns to the running power average. A comparator stage (38 and 40) compares the ratio to a threshold value to determine a first symbol in the received signals.

Abstract: A method is described for estimating channel impulse responses of a mobile radio channel with a broad bandwidth by a code division multiplexing method, and with a synchronization channel continuously transmitting sequences to mobile radio receivers. The sequences are provided for synchronization of each mobile radio receiver and are known to each of the mobile radio receivers. The transmitted sequences have pilot symbols for identifying the synchronization channel, and the pilot symbols are transmitted at points that are known to the receivers within a time slot. When searching for and identifying the synchronization channel, the pilot symbols and, possibly, further symbols and sequences which are known in the receivers, are evaluated to estimate the delay times and the complex amplitudes, of the mobile radio channel responses.

Abstract: A technique for determining performance characteristics of electronic systems is disclosed. In one exemplary embodiment, the technique may be realized as a method for determining performance characteristics of electronic systems. The method includes the steps of measuring a first response on a transmission medium from a falling edge transmitted on the transmission medium, and measuring a second response on the transmission medium from a rising edge transmitted on the transmission medium. The method also includes the step of determining worst case bit patterns for transmission on the transmission medium based upon the first response and the second response.

Abstract: DTV signals transmitted over the air with a symbol rate of around 10.76 million samples per second include echo-cancellation reference (ECR) signals each of which includes or essentially consists of a repetitive-PN1023 sequence with baud-rate symbols, which repetitive-PN1023 sequence incorporates a number of consecutive data-segment synchronization signals. Receivers for these DTV signals respond to these ECR signals to generate initial weighting coefficients for adaptive filters used for channel equalization and echo suppression. The initial weighting coefficients are calculated from a cepstrum extracted from the repetitive-PN1023 sequence ECR signal by DFT methods or with a PN1023 auto-correlation match filter.

Abstract: A data demodulating technique for binary data defined by a pulse code modulated signal. The technique involves digitizing the data signal read by a magnetic head from the stripe of a magnetic card. The time interval between peaks in the digitized signal is determined to provide peak interval values. The peak interval values form the basis for determining the end of a character and also by a pattern matching technique against idealized data form the basis for determining the character itself.

Abstract: An intermediate frequency signal SIF is demodulated and the noise component contained in a null portion (no-signal portion) is detected as the noise component contained in a signal of the sub-carrier frequencies. The frequency f0 of a reference frequency signal LO of a local oscillator 24 is feedback-controlled in accordance with the noise component thus detected. Further, the frequency f0 of the reference frequency signal LO is feedback-controlled in accordance with an error rate detected by an error correction section 23. Thus, the sub-carriers within the intermediate frequency signal SIF subjected to the frequency conversion by a mixer 16 based on the reference frequency signal LO thus feedback-controlled is separated from the noise component on the frequency axis. The intermediate frequency signal SIF is subjected to the Fourier transformation by a digital mixer/FFT calculation section 21, so that the noise component can be suppressed.

Abstract: A method of encoding a plural-bit data word as a plurality of multi-level symbols, where each of the plurality of multi-level symbols has a value selected from a predetermined plurality of levels. The method includes first translating each one of the selected bit positions of the plural-bit data word to one of the levels. When the contents of a predetermined one of the bits of the data word is a predetermined value, the method provides a second translation of each of the selected bit positions of the plural-bit data word to one of the levels. The method further includes generating a plural-bit offset word from predetermined bit positions of the data word and generating the multi-level symbols by addition of the offset word to the translated levels. One embodiment of the invention provides that the multi-level symbols are assigned a five-level code and the codes are treated as twos-complement numbers.

Abstract: Prediction methods for navigation message symbols of satellite systems, such as GPS (Global Positioning System) and GLONASS (Global Orbiting Navigation System), that use information repetition in navigation data messages are disclosed. The methods enable one to eliminate the impact of symbol modulation for a received signal on the threshold performance of any navigation receiver, thereby permitting its operation in severe environments when the carrier-to-noise ratio C/N0 of “weak” satellite signals falls to levels below C/N0=20 dB*Hz.

Abstract: A circuit for receiving data includes a first receiver having an input for receiving data and an input for receiving a first clock signal. The data is clocked into the first receiver by the first clock signal. The circuit also has a second receiver having an input for receiving data and an input for receiving a second clock signal. The first and second clock signals have the same frequency and are phase shifted with respect to one another. The data is clocked into the second receiver by the second clock signal. Determination is provided to determine if at least one of the receivers has correctly received the data. A first output of one of the receivers is enabled in accordance with the determination.

Abstract: A communication device for transmitting and receiving control and user data bursts in a digital telecommunication system. Data bursts including bursts of a first type and bursts of a second type different from the first type, are received, with the first type bursts comprising a first training sequence and the second type bursts comprising a second training sequence, Data of the received data bursts are auto-correlated; and the type of a received data burst is recognized on the basis of a phase value of the auto-correlation result of the training sequence of the data burst.

Abstract: Method and system for determining varying widths of each of a sequence of signal components (marks and spaces) in an incoming digital signal stream and for indicating which mark widths and which space widths fall outside acceptable ranges. A pre-mark and pre-space are added to the front end of the recieved stream for alignment purposes. The width of each signal component (mark or space) is determined and compared with an acceptable range of mark widths or space widths. Each mark or space that lies outside an acceptable range has an indicium associated with this mark or space, indicating this non-compliance. The modified digital signal stream, including the indicia, is re-issued after a selected time delay for subsequent signal processing. A method for measurement or estimation of mark width and space width is presented.

Abstract: A new method makes the most efficient use of the scarce spectral bandwidth in a wireless discrete multitone spread spectrum communications system. Each remote station and each base station in the network prepares an error detection field, such as a cyclic redundancy code (CRC), on each block of data to be transmitted over the traffic channels. The sending station prepares an error detection message for transmission over the link control channel of the network. The sending station prepares the error detection message by forming a link control channel vector that will be spread using the discrete multitone spread spectrum (DMT-SS) protocol to distribute the data message over a plurality of discrete tone frequencies, forming a spread signal for the link control channel. A link control channel is associated with communications session using the traffic channels. The instant of transmission of the error detection message is allowed to be different from the instant of transmission of the data message.

Abstract: Channel estimation is performed for a received signal, wherein different parts of the received signals are modulated using different modulation types. The channel is first estimated based on part of a received signal modulated with a first modulation type. This channel estimate is then transformed into a channel estimate corresponding to at least a second modulation type.

Abstract: In simultaneous reception of overlapping signals sharing a single spreading sequence, packet start times are found by separately demodulating, low pass filtering and despreading in-phase and quadrature components. Despread in-phase and quadrature signals are provided to sychronization filters connected in parallel and arranged in two identical pairs. Outputs from filters in different pairs are added, and the sums are squared. The squared signals are added. An exceeded threshold of the output from the last adder delineates a packet start. Knowing packet start times facilitates separating the overlapping inbound signals.

Abstract: A pulse monitoring circuit monitors the pulse length of both the logic high pulse and logic low pulse of a received digital sequence. The pulse lengths are compared with a preferred transition window, and if the pulses transition within the preferred transition window then they are categorized as good pulses. The pulse monitoring circuit issues an enable signal only when at least two consecutive good pulses are received. The pulse length is determined by means of a reference voltage, a first faster linear voltage ramp, and a second slower linear voltage ramp. The two linear voltage ramps are initiated in response to a logic change of the received digital sequence and continue to raise their outputs until the received digital sequence changes state once again. The values of the two linear voltage ramps at the time of the second state change are compared with the reference voltage.

Abstract: A method of design and an implementation system for reduced-state Viterbi detectors for intersymbol interference channels are provided. The method uses a complement states grouping technique that comprises the steps of finding the state distances between complement states; forming the reduced-state trellis by grouping the complement states with state distance no less than the minimum free distance; and by keeping the complement states with state distance less than minimum free distance unchanged. The resultant reduced-state Viterbi detector has negligible performance loss compared to the full-state Viterbi detector while the complexity is reduced by a factor of about two.