Abstract: A radio transmitter for transmitting signals in a predetermined frequency band has a transmit filter and a compensating filter. The transmit filter filters a signal to be transmitted from the transmitter to suppress the transmission of parts of the signal outside the band. The compensating filter, e.g., operating in the digital domain, filters the signal upstream from the transmit filter, wherein the compensating filter is arranged to alter the signal to counteract at least one of a phase ripple, an amplitude ripple, and a group delay variation of the transmit filter within the band.

Abstract: Pre-distortion, whose magnitude—and preferably phase—are frequency-dependent, is applied to an input signal in order to reduce spurious emissions resulting from subsequent amplification of the signal. In preferred embodiments, the pre-distortion technique of the present invention is implemented in combination with the (frequency-independent) magnitude and phase pre-distortion technique described in U.S. patent application Ser. No. 09/395,490 (“the '490 application”), where the frequency-dependent pre-distortion corresponds to amplifier distortion that has a magnitude that is proportional to the frequency offset from the carrier frequency and a phase shift of ±90° on either side of the carrier frequency. The frequency-dependent pre-distortion is generated by differentiating waveforms corresponding to pre-distortion parameters with respect to time and then applying the resulting differentiated pre-distortion parameters to the input signal.

Abstract: A set of interconnected delay stages, such as a voltage-controlled oscillator, has switch-controlled load circuitry connected to each output of each delay stage in the oscillator ring. In one embodiment, for each delay stage output, the switch-controlled load circuitry includes a switch, a transistor, and a current source. The switch is connected between the corresponding delay stage output and the transistor gate, the current source is connected between a power supply and the transistor drain, and the transistor source is connected to ground. In such a configuration, the transistor's gate-to-source capacitance can be applied to the corresponding delay stage output by closing the switch, for example, for lower-frequency operations. In addition, the output impedance of the current source decouples the capacitive load from the power supply, thereby substantially shielding the oscillator ring from noise in the power supply.

Abstract: A programmable logic device (PLD) having a programmable routing structure that employs non-static memory cells, such as dynamic random access memory (DRAM) cells, to control configurable circuit elements, such as pass-transistors and/or MUXes. In a representative embodiment, each DRAM cell is connected to its corresponding configurable circuit element using a buffer adapted to stabilize the output voltage generated by the cell and offset the effect of charge leakage from the cell capacitor. In addition, refresh circuitry associated with the DRAM cell periodically restores the charge in the cell capacitor using a refresh operation that is performed in the background, without disturbing the user functions of the PLD. Advantageously, a relatively large capacitance associated with a DRAM cell makes a PLD of the invention less susceptible to soft errors than a prior-art PLD that relies on SRAM cells for configuration control of its routing structure.

Abstract: Frequency-independent and frequency-dependent pre-distortion is implemented using look-up tables to retrieve pre-distortion parameters. To compensate for changes in amplifier operating characteristics over time, fixed pre-distortion tables can be used by appropriately offsetting the index values used to retrieve the pre-distortion parameters. The overall amplifier gain as well as the biases applied to one or more amplifier stages are also preferably controlled. In addition, the frequency-independent and/or frequency-dependent pre-distortion tables can be updated either periodically or as needed, by mapping a measure (e.g., average input signal power) to one or more parameters using equations (e.g., piecewise linear curves), where the parameters are applied to one or more polynomials to update the tables.

Abstract: A predistorter (26) comprises an array (44) of band pass filters (46 to 52) which divide an input signal into components. Each of the components is manipulated using coefficients retrieved from respective look-up tables (54 to 60). The amplitude of each component is used to retrieve a coefficient from its respective look-up table. The amplitude of each component is then multiplied with its respective retrieved coefficient to generate a predistorted amplitude for that component. The predistorted amplitudes are summed (at 80) to produce a predistorted input signal. The predistortion of the input signal is arranged to counter the distortion characteristic of a signal handling element (such as non-linear power amplifier 22 in FIG. 1) to which the predistorted input signal is subsequently supplied. The coefficients in the look-up tables (54 to 60) can be adapted using feed back from the output of the signal handling means (FIG. 5).

Abstract: Two or more digital-input RF amplifiers are configured in parallel such that a combiner combines their respective outputs to generate a relatively large composite RF output signal. A feedback control architecture minimizes the phase differences between the various amplifier outputs so that the outputs can be efficiently combined. The feedback control can measure the return loss for each amplifier to determine how to adjust each amplifier's phase. In some embodiments, the feedback control can also measure the composite RF output signal for use in phase adjustment. In certain implementations, phase adjustment is implemented by an iterative coarse phase-adjustment mode (e.g., based on either the return loss or the composite output signal) followed by an iterative fine phase-adjustment mode (e.g., based on the return loss).

Abstract: Programmable devices, such as FPGAs, are designed with I/O buffer architectures having (at least) three different types of I/O buffers: single-ended buffers with Peripheral Component Interconnect (PCI) clamps, single-ended buffers without PCI clamps, and differential buffers without PCI clamps. By distributing these different types of I/O buffers around the periphery of the device, a relatively low-cost device can be implemented with relatively small I/O buffers that collectively provide all of the I/O signaling functionality of prior-art devices that are implemented with relatively large, all-purpose I/O buffers, each of which supports the full range of I/O signaling options available on the device.

Abstract: In an amplifier system having two or more different amplifier sub-systems, the input signal to at least one of the amplifier sub-systems is pre-distorted based on the combined output signal from the two or more amplifier sub-systems. In one embodiment, each other amplifier sub-system pre-distorts its input signal based on only its own output signal. In one operational scenario, during initial operations, each amplifier sub-system separately pre-distorts its input signal based on only its own output signal. After pre-distortion has settled, one of the amplifier sub-systems is switched to pre-distort its input signal based on the combined output signal, while the other amplifier sub-systems continue to pre-distort their input single based on only their own output signals.

Abstract: A turbo encoder includes a memory for temporarily storing an incoming data sequence and an interleaved address generator (IAG) designed to generate a sequence of addresses corresponding to the interleaved data sequence. The IAG performs calculations based on the length of the incoming data sequence and is able to generate a first interleaved address by (or before) the time the incoming data sequence has completely shifted into the memory. As a result, the encoder begins to output encoded data substantially as soon as the corresponding incoming data have been received, thus substantially reducing the processing delay. In addition, each interleaved address can be generated on the fly as needed during data output. As a result, the entire set of interleaved addresses does not need to be stored, thus reducing the memory requirements for the encoder.

Abstract: Errors present in the output of an amplifier (10) are compared with the amplifier input in a control unit (24) to derive corrected coefficients for a look-up table used by predistorter (12) to eliminate distortion in the output of the amplifier (10). Depending on the format of the predistorter (12), at least some of the coefficients are corrected using measured errors that have been rendered independent of the input signal's amplitude.

Abstract: According to one embodiment, for an amplifier circuit employing feed-forward distortion compensation, phase and amplitude adjusters in the carrier cancellation and error cancellation loops can be continuously and simultaneously controlled to compensate for changes in the operating characteristics of the amplifier circuit. For the carrier cancellation loop, the two signals that are used to generate the error signal are sampled and used to generate control signals for the phase and amplitude adjusters that adjust the signal applied to the main amplifier. For the error cancellation loop, the two signals that are used to generate the output signal are sampled and used to generate control signals for the phase and amplitude adjusters that adjust the signal applied to the error amplifier. In each case, the control signals can be generated in the analog domain using relatively simple measurement circuitry.

Abstract: A convenience container (e.g., bag, tote, or case), mounted on a person (e.g., via a belt or belt loop), work bench, or work area, simplifies access and organization of tie wraps or cable ties in the work environment. The can be made of a heavy canvas cloth and includes a cut-out in the front that allows a user to reach in with his/her fingers, grasp a tie in the tote, and pull it out for use while preventing the other ties from spilling out at the same time. An access flap at the top, bottom, or side (optionally closed with Velcro, snap, or zipper) allows loading and unloading of ties into and from the tote. A belt loop on the back allows easy attachment to a utility or regular belt on the side, back, or front of one's person. Alternatively, a belt is included with the tote. Optionally, for larger versions of the tote, an additional (removable) thigh strap is included which allows the tote to be more securely fastened to the leg and prevents it from swinging free.

Abstract: Carrier phase recovery employs a single-axis blind cost criterion from the Bussgang class of functions, and its stochastic gradient, to generate a carrier phase error used to adjust a received and demodulated signal to near baseband. For one implementation, the estimate is derived in accordance with a Single-Axis Constant Modulus (SA-CM) criterion and its stochastic gradient via a SA-CM algorithm (SA-CMA). The carrier phase error is then used to adjust the carrier frequency and phase of the received and demodulated signal toward the frequency and phase of the carrier used to modulate the transmitted symbols, driving the carrier phase error to zero. The values used for the phase recovery may be either i) an IIR filtered signal, ii) a processed signal (e.g., decisions for the signal symbols), or iii) an equalized and processed signal.

Abstract: A single-axis receiver processing, for example, complex vestigial sideband modulated signals with an equalizer with forward and feedback filters. Forward and feedback filters have parameters that are initialized and adapted to steady state operation. Adaptive equalization employs linear predictive filtering and error term generation based on various cost criteria. Adaptive equalization includes recursive update of parameters for forward and feedback filtering as operation changes between linear and decision-feedback equalization of either single or multi-channel signals. An adaptive, linear predictive filter generates real-valued parameters that are employed to set the parameters of the feedback filter. In an initialization mode, filter parameters are set via a linear prediction filter to approximate the inverse of the channel's impulse/frequency response and a constant modulus error term for adaptation of the filter parameters.

Abstract: Methods of detecting relative misalignment between a color filter array and a sensor array in a color sensor array. The present invention provides methods for detecting and compensating for shifts of one or more rows and/or columns between a color filter array and a sensor array that may occur during the color sensor array fabrication process. The present invention also enables the use of color sensor arrays in which the alignment of a color filter array relative to the corresponding sensor array is unknown. In one embodiment, a detectable pattern of one or more pixels (e.g., pixels having black filters) is introduced into the periphery of the color sensor array. The position of the pattern is detected and color image data are processed with respect to the detected position. The invention is very cost effective and enables the use of image sensors with misaligned color filter arrays just as if they were manufactured correctly.

Abstract: An auditory scene is synthesized from a mono audio signal by modifying, for each critical band, an auditory scene parameter (e.g., an inter-aural level difference (ILD) and/or an inter-aural time difference (ITD)) for each sub-band within the critical band, where the modification is based on an average estimated coherence for the critical band. The coherence-based modification produces auditory scenes having objects whose widths more accurately match the widths of the objects in the original input auditory scene.

Abstract: A lineariser (100) for reproducing distortion present in the output of an amplifier (110) (or other signal handling device) generates a predistortion signal from the amplifier input. The predistortion signal is mixed into the amplifier input signal using, for example, a vector modulator (112). The predistortion signal may be derived in a quadrature format, the orthogonal components of the predistortion signal being mixed into separate mixers of the vector modulator. The predistortion signal is generated by multiplying the input signal with itself repeatedly to generate components of distortion which are susceptible of independent control. The predistortion signal is generated digitally using DSP (116). A multiplier or mixer may be used to square the sampled input signal to produce a reduced frequency signal which the DSP can use to gennerate the predistortion signal. Another lineariser mixes the predistortion signal into the input signal during up conversion.

Abstract: Symbol timing recovery employs a blind cost criterion from the Bussgang class of functions, and its stochastic gradient, to generate a timing phase error used to adjust sampling of received symbols. For one implementation, the estimate is derived in accordance with the Constant Modulus (CM) criterion and its gradient via the CM algorithm (CMA), and the estimate is calculated from a sequence of samples. This estimate is then used to adjust the period and phase of the sample sequence toward the period and phase of the transmitted symbols, driving the timing phase error to zero. The values used may be either i) samples themselves, ii) processed (e.g., interpolated) samples, or iii) equalized and processed samples. In addition, timing phase error estimates for other cost criteria, including the least mean squares algorithm, may be generated. These timing phase error estimates are selected either alone or in combination for deriving the timing phase error used to adjust the period and phase of the sample sequence.

Abstract: An imaging system with multiple boot options and preferably implemented as an integrated system-on-a-chip (SOC) imaging system. According to the present invention, an imaging system can be operated in one or more operating modes enabled in a number of ways. The imaging system can boot using one or more configurations stored either internally or externally, wherein a user can select a mode of operation or configure the imaging system for different applications. Consequently, multiple applications and, thus, market segments can be served by essentially the same hardware, while application-specific customization can be achieved by configuring the system from a plurality of boot options according to the intended application. In addition, the present invention enables loading new software, adding a new capability, such as interfacing with a new type of device, or implementing a special troubleshooting operating mode for maintenance and diagnostics.