Abstract: Sub-microsecond time transfer in a GPS/GNSS receiver using a weak GPS/GNSS signal is provided. The digitized complex baseband signal and the generated PN code are cross-correlated for each code period so as to output a complex correlation value at each code epoch of the generated PN code, where a sequence of the output correlation values form a data stream representing the navigation message. Bit synchronization generates bit sync pulses at bit boundaries. The location of a target segment having a known sequence at a known bit location in the navigation message is detected by searching through a plurality of sub-frames and accumulating search results for the plurality of subframes. Transmission time of the target segment is determined from the detected location of the target segment, with a certain time ambiguity. Accurate local time is determined by solving the time ambiguity using approximate time obtained from an external source.

Abstract: A data processing apparatus includes a first correlation operation unit which performs a mutual correlation operation of a first input series and a second input series, a threshold value operation unit which calculates a threshold value based on the first input series, a first comparison unit which compares a first mutual correlation value with the threshold value, a search window setting unit which sets a search window for detecting the second input series to the first input series on the basis of the comparison result, a hard decision unit which performs binarization of the first input series, a second correlation operation unit which performs a mutual correlation operation of a first input hard decision value, and a detection position determining unit which searches for a maximum value of the mutual correlation value within the search window and determines the detection time of the maximum value.

Abstract: A preamble detection apparatus includes: a threshold generation unit that determines a correlation maximum value detection threshold on the basis of a correlation peak value; a determination unit that detects one of correlation results, which exceeds the correlation maximum value detection threshold, as a correlation maximum value; a detection unit that updates the correlation peak value to the detected correlation maximum value when the correlation maximum value is detected; and a control unit that sets a period, in the event a correlation peak occurs, to a first period, sets a period, centering on a position where a distance from a correlation peak position is an integer multiple of a frequency hopping cycle, to a second period, and monitors presence or absence of a correlation result that exceeds the correlation maximum value detection threshold in the first and second periods, while not applying an erroneous detection threshold to the first period.

Abstract: A navigation system includes a correlation engine configured to despread a received signal. The correlation engine includes a correlator configured to evaluate the received signal against a replica signal to produce a correlation result, and a packet encoder configured to produce a packet comprising a destination address, a source address, and the correlation result. An input/output interface is configured to provide the packet to another component in the navigation system.

Abstract: A system and method of extracting data from data packets transmitted over a wireless network includes receiving a data packet having a preamble portion and a payload portion. The preamble portion is cross correlated with a first known spreading sequence to generate a first timing signal and the preamble portion is cross correlated with a second known spreading signal to generate a frame timing signal. An impulse is detected in the first timing signal and a first timing parameter is set based upon the detected impulse in the first timing signal. An impulse is detected in the frame timing signal and a frame timing parameter is set based upon the detected impulse in the frame timing signal. Data is extracted from the received payload portion according to the first timing parameter and the frame timing parameter.

Abstract: A spread spectrum communication system includes a channel encoder configured for modulating a carrier signal with data to form an information signal. A spreading sequence generator is configured for generating a spreading sequence having a phase angle dependent upon a chaotic sequence and contiguously distributed over a predetermined range. The chaotic sequence also has a magnitude which is selectively dependent upon the pseudo-random number or chaotic sequence. The invention also includes a multiplier configured for forming a spread spectrum signal by multiplying the information signal by the spreading sequence. The spreading sequence generator is responsive to a magnitude control signal for controlling the selective dependency of said magnitude. The magnitude can be constant to form a constant amplitude zero autocorrelation signal. Alternatively, the magnitude can be allowed to vary in selectively controlled chaotic or pseudo-random manner to vary a peak to average power ratio.

Abstract: A method for the generation of a signal including a minimum of disturbances and noise is provided. A method for the detection of a signal including a minimum of disturbances and noise is also provided. An element of the signal is functionally dependent on at least one further element of the signal.

Abstract: A method for detecting coherent interference includes the steps of: (a) receiving a signal at a first frequency, (b) forming a set of cross-correlation results by at least cross-correlating the signal with a first known code for a plurality of code offsets, (c) determining a statistical signature of the cross-correlation results, and (d) deciding, based on the statistical signature, whether non-negligible coherent interference is present within a search bin defined by the combination of the first frequency and the first known code.

Abstract: A UE may store received samples of a wireless signal at cx1 to reduce memory usage, but then may correlate those samples with cx2 timing hypotheses to improve performance. The received sequence is resampled at cx2 instead of cx1. The UE still performs the correlation of the cx2 timing hypotheses for the performance gain, but the reference waveform is resampled with cx2 time offset. A Fast Fourier Transform (FFT) may be taken of the received and reference waveforms. In the frequency domain, resampling may be performed by multiplying the FFT of the reference waveform by a phase ramp—a pointwise multiplication in the frequency domain with a constant magnitude sequence whose phase varies linearly.

Abstract: A method and apparatus for receiving a signal from transmitters such as GPS satellites, for fixing the location of the receiver. Each of the transmitted signals includes a unique periodically-repeating sequence. A received signal is stored by the receiver for at least two repetitions of the periodically-repeating sequence. FFT operations are performed, and the resulting data frequency samples are pruned responsive to a hypothesized residual frequency, a procedure which significantly reduces the total number of subsequent calculations and therefore significantly reduces processing time. A correlation series is determined from the pruned samples and reference frequency samples corresponding to a hypothesized transmitter. If a match is found in the examination of this series, a code phase offset is determined; if not the process is repeated with another hypothesized residual frequency. Multiple correlation series similarly obtained may also be incoherently combined prior to this examination.

Abstract: A correlation apparatus and method for frequency synchronization are provided. A frequency synchronization method of a receiver in a broadband wireless access communication system includes acquiring a highest correlation value by conducting a differential correlation of a variable interval between a received signal and a reference signal and performing a frequency synchronization according to the highest correlation value.

Abstract: A cell search method and apparatus for an asynchronous mobile communication system are provided. A Secondary Synchronization Code (SSC) correlator despreads a signal at every slot boundary in accordance with a z-sequence to output a SSC correlation value. The signal is received over a first symbol duration. A Primary Synchronization Code (PSC) correlator despreads the received signal in accordance with a PSC to output a PSC correlation value. A dot product calculator performs dot product calculation between the SSC correlation value and the PSC correlation value to output a correlation result of the SSC. A frame synchronization detector extracts frame synchronization information from the correlation result.

Abstract: A low complexity RACH preamble detector is described herein. The RACH preamble detection algorithm uses the peak detection of the time domain correlation function through frequency domain processing. The frequency domain processing considers the reference signals generated directly from frequency domain CAZAC sequence or time domain CAZAC sequence with DFT conversion. A low-complexity poly-phase LPF along with down sampling is implemented before the FFT to reduce the required length of the long FFT operation N-folded.

Abstract: Control circuitry is configured to control a sampler, in a sampling phase determination process, to sample a signal at a sampling period of T±T/n for outputting a sample set for each one of n phases of the sampled signal. Each one of n correlators has a first input configured to receive one of the sample sets, a second input configured to receive a PN signal, and an output which provides a correlation result from a correlation process between the sample set and the PN signal. The control circuitry is further configured to identify, from the correlation results, one of the phases associated with the optimal correlation result. The control circuitry is then configured to control the sampler, in a communication mode, to sample a received signal at a sampling period of T at the phase associated with the optimal correlation result.

Abstract: There is provided a channel estimating method of performing frequency conversion by a first fast Fourier transformation on a reception signal and extracting a desired signal after demodulating the reception signal, and deriving electrical energy against time delay of a channel by inverse fast Fourier transformation of the extracted result, wherein: values of a low pass filter, having an output from oversampling the input to the first fast Fourier transformation, are thinned by a plurality of thinning circuits with the same synchronization and different discrete times, and based on the outputs of the plurality of thinning circuits, the electrical energy against time delay related to the reception signal arrival time position is derived by respectively performing the first fast Fourier transformation and the inverse fast Fourier transformation.

Abstract: A multipath searcher and method includes a programmable decimation filter configured to adjust a sample rate of a received pilot signal. A plurality of correlators is configured to compare the received pilot signal to a reference code in a first mode and in a second mode. The first mode includes a low resolution search of a search window performed such that the plurality of correlators encompass an entire search window concurrently and the plurality of correlators receives a delayed reference code delayed to correspond with a portion of the search window in which a corresponding correlator performs correlation to identify peaks in the received pilot signal. The second mode includes a high resolution search of a refined search window only at or near identified peaks discovered in the first mode. The high resolution search is focused at the peak location by adjusting delays in the plurality of correlators.

Abstract: Methods and apparatus are presented for improving the feedback of channel information to a serving base station, which allows a reduction in the reverse link load while allowing the base station to improve the forward link data throughput. Over a channel quality indicator channel, three subchannels are generated; the re-synch subchannel, the differential feedback subchannel, and the transition indicator subchannel. The information carried on each subchannel can be used separately or together by a base station to selectively update internal registers storing channel conditions. The channel conditions are used to determine transmission formats, power levels, and data rates of forward link transmissions.

Abstract: A synchronization method in a Ultra Wideband (UWB) receiver includes receiving a signal through a multipath channel, and synchronizing with a first multipath component of the received signal by computing a correlation value between the received signal and a template signal of the receiver in a predetermined search range. Since multipath components received at the receiver after the first multipath component of the received signal have lower power than that of the first multipath component, the synchronization with the first multipath component of the received signal may improve the performance in processes after the synchronization process.

Abstract: A MIMO transmitter has a modulator (40,41,42, 120, 122) a demultiplexer 100 arranged to divide the information into one or more demux streams for transmission over different ones of the channels, and a diversity splitter (110) to derive one or more sub-streams of the same information. A decorrelator (120) such as a scrambler (150, 155) decorrelates the sub-streams before or after the modulation. The arrangement is configurable to vary in use a ratio of demultiplexing and of diversity splitting. This balances between the gains from diversity and spatial multiplexing, without needing major changes to the transmit and receive processing.

Abstract: A radio transmission apparatus for transmitting a first radio signal and a second radio signal with different communication system, the apparatus includes: a first transmission unit which generates the first radio signal on the basis of a first communication system and transmits the first radio signal; a diffusion processing unit which performs diffusion processing of data allocated to DC subcarrier on the basis of the first communication system, and generate a diffusion signal; an addition unit which adds the diffusion signal and a signal obtained by orthogonal frequency division multiplex processing; and a second transmission unit which transmits the added signal as the second radio signal.

Abstract: A convenient handheld locator is provided for locating an item in an urban environment in which the locator is programmed to search for and locate specific items, with the detected item being displayed on the locator as to its identity or name, also displaying where the item is relative to the locator, as to position and range.

Abstract: A method for communication includes transmitting data from a transmitter to a receiver using Adaptive Coding and Modulation (ACM). The data rate is set by selecting, based on feedback, an ACM profile defining a Forward Error Correction code and a modulation scheme. Upon detecting that the feedback is unusable, an operation of the transmitter is changed independently of the feedback. In another method, data is exchanged over two opposite directions of a bidirectional link that uses ACM by communicating using two ACM profiles. A joint constraint is defined on the two directions. The two ACM profiles are set based on first and second measured reception quality metrics of the two link directions, to meet the joint constraint. In yet another method, a subset of the ACM profiles is temporarily disabled, and the data is transmitted using only the ACM profiles that are not disabled.

Abstract: A multipath signal determination method includes carrying out correlation operation between a received signal of a positioning signal spread-modulated with a spread code and a replica signal of the spread code with respect to each of IQ components at a predetermined sampling phase interval, and determining whether the received signal is a multipath signal or not, in accordance with a plot position in the case where each correlation value in each of the sampling phases is sequentially plotted on an IQ coordinate.

Abstract: An adaptive transversal filter having tap weights Wj which are products of corresponding tap coefficients Cj and tap gains Mj is provided. A filter control loop controls all of the tap coefficients Cj such that an error signal derived from the filter output is minimized. One or more tap control loops controls a tap gain Mk such that the corresponding tap coefficient Ck satisfies a predetermined control condition. For example, |Ck| can be maximized subject to a constraint |Ck| Cmax, where Cmax is a predetermined maximum coefficient value. In this manner, the effect of quantization noise on the coefficients Cj can be reduced. Multiple tap control loops can be employed, one for each tap. Alternatively, a single tap control loop can be used to control multiple taps by time interleaving.

Abstract: The present invention relates to an apparatus for rejecting images in a receiver. The apparatus of the present invention relates to an apparatus for rejecting image signals in a receiver of a direct conversion structure and comprises a signal mismatch compensation unit configured to detect gain error and phase error between an In-phase (I) signal and a Quadrature (Q) signal received through the receiver, to reject image signals existing in the I and Q signals, and to output a result. The signal mismatch compensation unit detects the gain error and the phase error using an adaptive step method of reducing the step size of the gain error and the phase error step by step whenever the gain error and the phase error are converged. According to the present invention, high image rejection ratio is achieved and the adaptation time taken to obtain a high image rejection ratio is reduced simultaneously.

Abstract: Complex digital data values derived from a DSSS signal, in particular, a GNSS signal, are delivered to a general purpose microprocessor at a rate of 8 MHz and chip sums over eight consecutive data values spaced by a sampling length (TS), each beginning with one of the data values as an initial value, formed and stored. For code removal, each of a series of chip sums covering a correlation interval of 1 ms and each essentially coinciding with a chip interval of fixed chip length (TC), where a value of a basic function (bm) reflecting a PRN basic sequence of a satellite assumes a correlation value (Bm), is multiplied by the latter and the products added up over a partial correlation interval to form a partial correlation sum. The partial correlation interval is chosen in such a way that it essentially coincides with a corresponding Doppler interval having a Doppler length (TD) where a frequency function used for tentative Doppler shift compensation and represented by a step function (sine, cosine) is constant.

Abstract: The present invention relates to a method for transmitting data Di in a telecommunication system SYST including a first transceiver TXi and a second transceiver RX linked together by means of a communication channel Chi, one of which transceivers being mobile, which method includes: a spreading step for spreading said data Di over a plurality of components Ctj (for j=1 to M), and an equalization step during which each component Ctj (for j=1 to M) is multiplied by an equalization value Wi(j)* representative of communication conditions within the communication channel Chi. According to the invention, the equalization values Wi(j)* are also representative of a Doppler effect generated by movement of the mobile transceiver. The invention enables to significantly compensate for alterations caused to the communication channel Chi by movement of the mobile transceiver.

Abstract: A code division multiplex signal transmitter includes an operational circuit, a modulator unit and a multiplexer. The operational circuit adds up input transmission data on channels to produce resultant added data and modulates pieces of bit transmission data which are indicative of the values of the respective bits of the added data, when expressed in binary form, the pieces of bit transmission data being equal in number to the M bit positions of the added data expressed in binary form. The modulator unit includes modulators corresponding in number to the M bit positions of the added data in the binary form. A k-th modulator, where k is an integer of 1 to M, inclusive, modulates a k-th piece of bit transmission data to produce a k-th bit modulated signal whose amplitude level is 2k-1. The multiplexer multiplexes first to M-th bit modulated signals to produce a code division multiplex signal.

Abstract: A method for estimating the speed of a mobile device in a network is provided that includes selecting a correlation length from a plurality of possible correlation lengths. A correlation result is generated based on the selected correlation length. A speed estimate is generated for the mobile device based on the correlation result.

Abstract: A correlation device and method is provided. According to the present invention, the correlation device comprises a first signal path for receiving a received signal; at least one second signal path for receiving the received signal and eliminating effect of a subcarrier component of the received signal; and a correlation unit couple to the first signal path and each second signal path, for selecting an output of one of the first and second signal paths to execute signal correlation.

Abstract: Signal impairment correlations for multiple signals in a received multipath signal are constructed by fitting parametric models associated with each high-data-rate signal in the multipath against measured impairment correlations. The estimated model fitting parameters are applied to form impairment correlation estimates for all signals. The models comprise a separate impairment covariance matrix scaled by a model fitting parameter for each high-data-rate signal and a noise covariance matrix scaled by a noise element model fitting parameter. The model fitting parameters may be estimated by a least-squares formulation and applied to form impairment correlation estimates for all signals of interest. The resulting impairment correlation estimates may be provided to G-RAKE receivers or joint scaling demodulators to demodulate the signals while suppressing interference from the high-data-rate signals.

Abstract: In a wireless communication system, a portable device and an in-vehicle device wirelessly communicate with each other by a spread spectrum method. The in-vehicle device transmits a synchronization signal indicative of a reference period to the portable device. The in-vehicle device performs code acquisition for only a portion of a spread wireless signal received from the portable device. The portion has a starting point in a search period from a search start point to a search end point. The search start point is identified based on the reference period and a predetermined first correction time. The search end point is identified based on the reference period and a predetermined second correction time.

Abstract: A parallel interference cancellation (PIC) receiver incrementally removes interference from signals in parallel modules in successive stages. For each desired signal, as interfering signals are removed, corresponding updates to a data covariance matrix are modeled as computationally tractable rank-one updates to a root matrix of the covariance matrix. Processing of signals and/or covariance information may be initiated, continued, and/or halted at various stages, e.g., in response to signal or data quality. The PIC receiver using root matrix updates is applicable to a variety of demodulation techniques.

Abstract: In one embodiment, a method includes generating a set of sequences of chip values and calculating a correlation between a demodulated signal and each one of two or more of the sequences. Each of the correlations has an absolute value, and one of the correlations has a highest absolute value. The method includes selecting the one of the sequences with the correlation having the highest absolute value; identifying a sequence index corresponding to the selected one of the sequences; and, for each of one or more data symbols in the demodulated signal, determining a value of the data symbol based on the sequence index corresponding to the selected one of the sequences.

Abstract: The present invention includes a method of determining a phase estimate for an input signal having pilot symbols. The method includes receiving a plurality of pilot symbols, and then multiplying two or more pilot symbol slots by corresponding correlator coefficients to correct a phase estimate of the input signal.

Abstract: In accordance with a detection method in a wireless communication system, an initial hypothesis for a starting position of a desired signal within a received wireless communication signal may be determined. The desired signal may have a conjugate symmetric property. At least one correlation value may be determined based on the initial hypothesis. The at least one correlation value may indicate the extent to which at least one sample sequence selected from the received signal has the conjugate symmetric property.

Abstract: Provided is a receiver including a receiving unit, a demodulator-decoder unit, a synchronization detecting unit, and an output control unit. The receiving unit receives digital broadcasting. The demodulator-decoder unit obtains an output including a transport stream through a demodulating processing and a decoding processing performed on a reception signal received by the receiving unit. The synchronization detecting unit secures synchronization on the basis of the reception signal received by the receiving unit, and generates a timing signal to be used in the demodulating processing and in the decoding processing. The output control unit outputs the output including the transport stream from the demodulator-decoder unit if the synchronization is secured. The output control unit fixes a logic level of the output including the transport stream if the synchronization is not secured.

Abstract: Rapid uplink synchronization is enabled by reducing a 2D search problem to two 1D search problems, which can generally be performed in less time. Advantage is taken of fact that a mobile device sends a ranging code on multiple sub-carriers. Using the assumption that adjacent sub-carriers will have approximately equivalent channel characteristics, phase ambiguity can be removed by differentially combining pairs of adjacent sub-carriers. Once the phase ambiguity is removed, the code, timing, and power level may be determined relatively quickly. In one embodiment, the values of correlations between received signals and possible codes are compared with a threshold.

Abstract: An early-late gate based ADC timing approach is described for performing early-late gate timing recovery despite the presence of multipath signal distortion. Multipath conditions may severely distort Barker correlator magnitudes generated for taps within two taps of a determined bit synchronization time. Exemplary embodiments of the described approach may combine Barker correlator magnitudes for several receive chains to calculate the timing error correction corresponding to a difference of early and late taps. The approach may be used to increase the size and stability of Barker correlator magnitudes generated for taps far away from a determined bit synchronization time.

Abstract: A system and method is provided for improving the operating range for UWB communication systems by increasing the margin between true correlation peaks and false correlation peaks in a received UWB signal. A received signal is first correlated with a UWB kernel before being correlated with the PRN code. The UWB kernel is a very short UWB pulse having the same pulse shape as the UWB signal pulses. By pre-correlating the received signal with the UWB kernel at least once prior to correlating with the PRN code, the margin between true correlation peaks and false correlation peaks is substantially improved.

Abstract: Certain embodiments of the present disclosure allow for detection of a transmitted preamble sequence by processing a correlation of a received signal and a preamble hypothesis in a way that exploits the good correlation properties of the known set of preamble sequences. For certain embodiments, the highest peaks of the correlation output may be compared across all preamble hypotheses to decide which preamble sequence is transmitted.

Abstract: Techniques for initial wireless network synchronization by a mobile station are provided. For certain embodiments, the techniques may involve a joint search for the cell identification (ID-cell index) and the coarse carrier frequency offset (CFO) estimation. For certain embodiments, the techniques may be based on hard correlation and binary differential despreading that substantially simplifies computational complexity compare to known techniques that independently search for the ID-cell index and perform CFO estimation.

Abstract: A method for processing, in an ultra-wide band receiver, a sampled rectified ultra-wide band received signal, including: at least one sliding correlation between a selection of samples of the sampled ultra-wide band received signal and a correlation sequence, the sliding correlation carrying out a succession of n elementary correlation steps, n being an integer larger than or equal to 2, at a frequency f, between the selection of samples and the correlation sequence, an elementary correlation producing a series of intermediate correlation samples, and summation of the intermediate correlation samples delivered by each of the n elementary correlation steps to form n correlation samples which form a correlation vector.

Abstract: The invention relates to the acquisition of a code modulated signal, wherein a first set of correlation results for correlations between the code modulated signal and a first replica code with different code phases and a second set of correlation results for correlations between the code modulated signal and a second replica code with different code phases are available. In order to achieve a high sensitivity, results from both sets of correlation results are combined, wherein correlation results used in the combination are selected based on information on a relative difference between a correct code phase for both replica codes. Then, it is determined based on the combination whether at least one of the sets of correlation results comprises a correlation result representing the correct code phase for the first replica code or the second replica code, respectively.

Abstract: A device performs demodulation of control signals from multiple radio terminals, based on the correlations in the frequency domain between a predetermined code and the orthogonalized control signals and reference signals of the multiple radio terminals obtained by cyclic shifts of the predetermined code. The device includes: a demultiplexer which demultiplexes a reference signal component and a control signal component based on a correlation profile; a path detector which detects a path location or path locations for each radio terminal based on the power values of the reference signal components; extractor which extracts the correlation values of the reference signal components and the correlation values of the control signal components, respectively; and RAKE combiner which combines the extracted values.

Abstract: A method for determining a Doppler shift of a first signal is provided. First, a plurality of Doppler frequency hypotheses is combined to obtain a joint Doppler signal. The first signal is the correlated according to the joint Doppler signal and a plurality of code signals with phases corresponding to a series of code phase hypotheses to obtain a series of correlation results which are then examined to determine whether the Doppler shift does lie in the Doppler hypotheses. A fine Doppler search is then performed to determine the Doppler shift when the Doppler shift lies in the Doppler hypotheses.

Abstract: A system including a differential demodulation module, a first summing module, and a second summing module. The differential demodulation module generates differentially demodulated signals based on having differentially demodulated received signals. The first summing module generates a combined signal by adding the differentially demodulated signals, wherein the combined signal includes a plurality of symbols. The second summing module generates a plurality of sums for each of a plurality of derived preamble sequences, wherein the derived preamble sequences are derived from preamble sequences, and wherein each of the derived preamble sequences includes a plurality of derived symbols. The second summing module further generates cross-correlation values for the derived preamble sequences based on the plurality of sums, wherein one of the cross-correlation values generated for one of the derived preamble sequences is a sum of the plurality of sums generated for the one of the derived preamble sequences.

Abstract: Methods and apparatus are provided for use in devices operatively enabled to perform waveform correlation result processing.

Abstract: Direct detection of wireless interferers in a communication device for multiple modulation types. One or more radios implemented within a communication device is/are operative to receive and process wireless communications. A wireless communication signal is processed to extract symbols there from. Various symbols groups are processed in accordance with correlation processing to identify potential interferers (e.g., other communication devices using common portions of frequency spectra). Alternatively, matched filter processing (e.g., using a Barker matched filter in some embodiments) operates on the various symbol groups to identify some potential interferers. Various combinations of correlation processing and matched filter processing may be employed in other instances (e.g., using any of a desired means of comparison, combining, etc.) in considering interferers identified in accordance with each of these two means.

Abstract: Methods, systems, and machine-readable code for optimizing transmit power of a power amplifier using a Vbat monitor are disclosed and may comprise adjusting the gain of gain stages in a transmit path based on a control signal that is a function of a supply voltage signal, among other variables, derived from a supply voltage that may be used to power a transmit path. The supply voltage signal may be received from a power management unit or derived directly from a battery or other supply. The supply voltage signal may be compared to a reference signal, the result of which may be utilized to generate the control signal. The values for the control signals may be determined over a range of supply voltages and stored in a lookup table.