Abstract: A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Abstract: Methods, apparatus, and systems are disclosed for, among other things, passphrase input using secure delay, passphrase input with characteristic shape display, user authentication with non-repeated selection of elements with a displayed set of elements, document authentication with embedding of a digital signature stamp within a graphical representation of the electronic document wherein the stamp comprises digits of a digital signature, and sub-hash computation using secure delay.

Abstract: In a disclosed method for authenticating a digital signature key, a record is prepared that includes an integrated combination of indicia uniquely corresponding to the key, and indicia of a covenant not to repudiate any digital signature made with the key except under specified conditions. The owner of the key performs a legally accepted execution of the record, whereby he enters into a covenant with any bearer of the record not to repudiate any digital signature made with the key except under the specified conditions.

Abstract: A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Abstract: Among other things, calibration of a signal processing system is disclosed to minimize vector mismatch between signals frequency-translated from an RF signal and conveyed along a plurality of signal paths of the signal processing system. A calibration signal having a plurality of tones is coupled to the signal processing system such that it is frequency translated. The frequency-translated calibration signal is sampled along a first signal path of the signal processing system to obtain a first set of observed samples. It is also sampled along a second signal path of the system to obtain a second set of observed samples. The first set of observed samples is filtered with an adaptive filter having a set of adaptable coefficients to obtain a set of filtered samples. The coefficients are adapted to minimize undesired deviations between the set of filtered samples and the second set of observed samples.

Abstract: A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Abstract: An exemplary signal processing system determines vector mismatch between a plurality of signal paths. Advantageously, the system can determine mismatch across a range of frequencies. A signal generator of the system can provide a periodic calibration signal having a plurality of frequency components. The system frequency can translate the calibration signal to provide a first set of observed samples. The first sample set can be compared to a second set of samples, which can be modeled by a function of parameters including an estimated vector mismatch and a plurality of basis functions. A value of vector mismatch can then be determined (at least to an estimate) that minimizes the difference between the first sample set and the second sample set. Methods and other systems with different advantageous configurations are also described.

Abstract: A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Abstract: A system is disclosed for generating text responsive to both voice and handwriting input, including a microphone, stylus, and a tablet having an flat-panel display integrated into its surface. The system performs speech and handwriting recognition using a shared language model, which in one embodiment is trainable responsive to user correction of errors in either speech or handwriting recognition. Various other systems and methods are also disclosed.

Abstract: Certain disclosed methods and systems perform multiple different types of message recognition using a shared language model. Message recognition of a first type is performed responsive to a first type of message input (e.g., speech), to provide text data in accordance with both the shared language model and a first model specific to the first type of message recognition (e.g., an acoustic model). Message recognition of a second type is performed responsive to a second type of message input (e.g., handwriting), to provide text data in accordance with both the shared language model and a second model specific to the second type of message recognition (e.g., a model that determines basic units of handwriting conveyed by freehand input). Accuracy of both such message recognizers can be improved by user correction of misrecognition by either one of them. Numerous other methods and systems are also disclosed.

Abstract: A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Abstract: An RF tuner and tuning method employs analog quadrature mixing with a coarse-stepwise tunable local oscillator to a near-baseband passband region, followed by A/D conversion of the I and Q signals, correction of phase, group delay, and amplitude errors, image rejection, and translation to baseband by (1) fixed frequency translation, (2) stepwise channelized translation, or (3) essentially continuously variable tuning over a given digital tuning range. The near-baseband passband region is sized and located such that alternating image rejection provides non-redundant and complete tuning coverage of a desired high frequency spectrum with a local oscillator step size equal to about twice the digital tuning range or about twice the number of channels digitally stepwise tunable times the channel width, effectively doubling the typical local oscillator step size.

Abstract: Certain disclosed methods and systems perform multiple different types of message recognition using a shared language model. Message recognition of a first type is performed responsive to a first type of message input (e.g., speech), to provide text data in accordance with both the shared language model and a first model specific to the first type of message recognition (e.g., an acoustic model). Message recognition of a second type is performed responsive to a second type of message input (e.g., handwriting), to provide text data in accordance with both the shared language model and a second model specific to the second type of message recognition (e.g., a model that determines basic units of handwriting conveyed by freehand input). Accuracy of both such message recognizers can be improved by user correction of misrecognition by either one of them. Numerous other methods and systems are also disclosed.

Abstract: An RF tuner and tuning method employs analog quadrature mixing with a coarse-stepwise tunable local oscillator to a near-baseband passband region, followed by A/D conversion of the I and Q signals, correction of phase, group delay, and amplitude errors, image rejection, and translation to baseband by (1) fixed frequency translation, (2) stepwise channelized translation, or (3) essentially continuously variable tuning over a given digital tuning range. The near-baseband passband region is sized and located such that alternating image rejection provides non-redundant and complete tuning coverage of a desired high frequency spectrum with a local oscillator step size equal to about twice the digital tuning range or about twice the number of channels digitally stepwise tunable times the channel width, effectively doubling the typical local oscillator step size.

Abstract: Methods and systems permit electronic transmission of payment or a rebate to a payee or rebate recipient. The payee or rebate recipient (320) prints a financial instrument (364) or generates a coupon at a printer (360) or user terminal (350). The financial instrument or coupon (364) can be generated without the need for special equipment and can be redeemed for payment at a financial institution of the payee or rebate recipient's choosing.

Abstract: An RF tuner and tuning method employs analog quadrature mixing with a coarse-stepwise tunable local oscillator to a near-baseband passband region, followed by A/D conversion of the I and Q signals, correction of phase, group delay, and amplitude errors, image rejection, and translation to baseband by (1) fixed frequency translation, (2) stepwise channelized translation, or (3) essentially continuously variable tuning over a given digital tuning range. The near-baseband passband region is sized and located such that alternating image rejection provides non-redundant and complete tuning coverage of a desired high frequency spectrum with a local oscillator step size equal to about twice the digital tuning range or about twice the number of channels digitally stepwise tunable times the channel width, effectively doubling the typical local oscillator step size.

Abstract: The characterization and detection of an identifying bit sequence is performed without digital demodulation or bit synchronization. A waveform containing a digital bit sequence is correlated with waveforms corresponding to a set of known bit sequences. For each bit sequence, one of the inputs to a correlator is shifted through all possible values of correlation lag while the correlation match for each lag value is compared to the others so that a peak correlation between the two waveforms is determined. The peak correlation values for each of the known bit sequences are then compared to characterize how closely the received radio frequency signal corresponds to each of the known bit sequences. The bit sequence that most closely corresponds to the waveform of the received signal may then be identified. Applications include the identification of the N-AMPS DSAT and the GSM training sequence in a cellular radio scanning receiver.

Abstract: A sample reconstruction device and method extracts digital values from a DSP that are digital samples of a signal of interest and reconstructs the digital samples into an equivalent analog signal. A context detector monitors the context of the DSP's operation and determines when a digital value being processed by the DSP is a digital sample of a signal of interest. The context detector may be implemented using a logic analyzer, DSP emulator system, or the DSP itself. A digital probe or input extracts the digital values selected by the context detector for reconstruction into an analog signal. A sample buffering system having a FIFO buffer memory and control loop is employed to ensure that the analog sample interval is substantially constant, even if there is a great deal of variation between the digital sample intervals. The analog samples are reconstructed into an analog signal that accurately represents the digital signal found within the DSP.

Abstract: An RF tuner and tuning method employs analog quadrature mixing with a coarse-stepwise tunable local oscillator to a near-baseband passband region, followed by A/D conversion of the I and Q signals, correction of phase, group delay, and amplitude errors, image rejection, and translation to baseband by (1) fixed frequency translation, (2) stepwise channelized translation, or (3) essentially continuously variable tuning over a given digital tuning range. The near-baseband passband region is sized and located such that alternating image rejection provides non-redundant and complete tuning coverage of a desired high frequency spectrum with a local oscillator step size equal to about twice the digital tuning range or about twice the number of channels digitally stepwise tunable times the channel width, effectively doubling the typical local oscillator step size. The digital tuning is preferably performed by a continuously variable bandpass decimating filter with aliasing to within R.sub.D of baseband, where R.sub.

Abstract: A radio receiver for receiving radio frequency (RF) signals includes an analog down-converting and filtering section for down-converting and selecting the RF signals to an intermediate passband and a stopband which substantially determine the widest bandwidth of operation of the radio receiver. An analog-to-digital converter converts the intermediate frequency signal to a sampled digital signal. A digital filtering section, responsive to the sampled digital signal, includes wideband and narrowband digital filters for providing wide bandwidth and narrow bandwidth baseband quadrature output signals for the widest bandwidth of operation and a narrow bandwidth of operation at a frequency within a passband. The wideband digital filtering is designed to only provide a modest amount of additional stopband attenuation with a significantly sharper transition band rolloff from passband to stopband.