297 results about "Loop bandwidth" patented technology

A novel apparatus for and a method of estimating, calibrating and tracking in real-time the gain of a radio frequency (RF) digitally controlled oscillator (DCO) in an all-digital phase locked loop (ADPLL). Precise setting of the inverse DCO gain in the ADPLL modulating path allows direct wideband frequency modulation that is independent of the ADPLL loop bandwidth. The gain calibration technique is based on a steepest descent iterative algorithm wherein the phase ADPLL error is sampled and correlated with the modulating data to generate a gradient. The gradient is then scaled and added to the current value of the DCO gain multiplier.

A method for maintaining the states of a receiver during the silent line state of a network device operating in a low power link suspend mode is presented. Accordingly, a method of freezing the states of the equalizer and keeping the receiver clock locked to a frequency that is approximately equal to that of the input data while providing for rapid adjustment to the phase and thus recovery of the input data is presented. During Silent Line State (SLS), the receiver states are frozen using methods that avoid parasitic decay. Also, the receive clock phase lock loop is locked onto the local transmit clock since the local transmit clock has a frequency approximating the incoming data frequency. During the SLS, the transmitter of the remote network device may have been turned off to conserve power therefore the receiver has no way of immediately knowing the phase of an incoming data. Thus, in order to prevent loss of data, the receiver loops of the receiving network device are trained to the frequency of the transmitting remote network device using periodic Link Suspend packets. Thus, in most cases, only the phase of the incoming signal need be acquired when data arrives. The phase may be quickly acquired using loop bandwidth shift methods whereby the receive clock phase lock loop bandwidth is increased to a value that aids rapid acquisition of the input clock and then, after acquisition, the bandwidth is shifted to a low value to enhance noise rejection during tracking.

A receiver (50) includes a self-calibrating receive path correction system for correction of I/Q gain and phase imbalances in a radio frequency signal. The system includes a signal-processing block (53), an I/Q phase imbalance detection and correction circuit (98), an I/Q gain imbalance detection and correction circuit (96), and an adaptive loop bandwidth control circuit (102). The I/Q phase imbalance detection and correction circuit (98) equalizes for the relative phase imbalance and the I/Q gain imbalance detection and correction circuit (96) equalizes for the relative gain imbalance between the I and Q channels created by the analog portion of a quadrature receiver. The adaptive loop bandwidth control circuit (102) dynamically adjusts at least one loop bandwidth for the I/Q gain imbalance detection and correction circuit (96) and the I/Q phase imbalance detection and correction circuit (98) on a slot boundary.

A switch-mode power supply (SMPS) with auto-tuning using limit-cycle oscillation response evaluation provides optimized performance with reduced capacitance and inductance requirements for a given design. During operation of the SMPS, parameters of the converter are extracted, and the feedback and/or feed-forward compensation is adjusted to either hold the loop bandwidth of the converter near the critical bandwidth of the output capacitors, or maintain output voltage transients within a specified limit. The compensator response is either periodically updated, or is updated in response to an event, such as detection of a transient voltage spike having a characteristic that exceeds one or more predetermined thresholds.

A system and method for canceling DC offset for Mobile Station Modems having direct conversion architectures. The present invention is a fast acquiring DC offset cancellation block that provides rapid and accurate DC offset estimates and cancellation techniques to support direct conversion architectures. The fast acquiring DC offset cancellation block combines four mechanisms to rapidly acquire and remove a DC offset estimate after power up, temperature changes, receiver frequency changes, and gain setting changes by increasing high pass loop bandwidth and adjusting DC offset levels at baseband. After removing the DC offset in large portions, the high pass loop bandwidth is decreased to fine tune the previous estimate and to remove any small variation in DC offset due to receiver self-mixing products.

A frequency synthesizer and an automatic calibration device are disclosed. An automatic calibration device for a phase-locked loop based frequency synthesizer includes: a frequency-to-digital converter for converting a frequency of a signal outputted from a voltage controlled oscillator into a first digital value; a frequency difference detector for calculating a difference between the first digital value outputted from the frequency-to-digital converter and a second digital value corresponding to a target frequency; an automatic frequency calibration logic for selecting an optimal control code for a capacitor bank such that an output frequency of the voltage controlled oscillator is closer to the target frequency; and a loop bandwidth calibration logic for tuning a charge pump gain such that a loop bandwidth is kept constant in the optimal control code using the frequency-to-digital converter. Thus, the calibration speed can be increased, and the loop bandwidth can be kept constant within the output frequency range.

Techniques for direct modulation of a voltage-controlled oscillator (VCO) with adaptive digital gain control for wideband wireless applications are disclosed. A digital adaptive gain control loop is used to directly modulate the VCO, and a phase-locked loop (PLL) to track the frequency drift and other nonlinear effects of the VCO. As the PLL is applied to track the carrier frequency without passing the modulation signal into the PLL loop filter, the PLL can be implemented with a narrow loop bandwidth. The wideband frequency modulated signal is directly up-converted to the radio frequency (RF) signal by directly modulating the VCO through a digital-to-analog converter which is digitally controlled by an adaptive gain control loop. Thus, both wide bandwidth and low output noise for a frequency synthesizer and modulator can be achieved.

A phase locked loop (PLL) can include a test loop filter (100) that generates a control voltage (V_CTRL) for input to a voltage controlled oscillator (VCO). In a test mode, a control voltage can be varied and resulting output frequencies recorded, from which an open loop bandwidth can be determined. A control voltage can be varied by enabling a switch element (104-1) that can provide a current path through load resistance (RL) of test loop filter (100). Current provided to the test loop filter can be varied according to test signals to provide a variable control voltage (V_CTRL).

A digital phase lock loop circuit, where under certain conditions the phase error is derived from phase comparison between a reference clock edge and the next oscillator clock edge rather than a feedback clock edge. This technique can be used to significantly reduce digital phase lock loop circuit power by disabling feedback divider and sync FF once initial frequency lock is established, provided phase jitter of digital phase lock loop circuit is low enough so that there is no cycle slip. This technique can also be used to multiply the effective reference clock frequency of digital phase lock loop circuits to increases the loop bandwidth, thus reducing the phase noise. Both the applications of this technique can be combined in some circuits.

The invention discloses a new method for RAIM (receiver autonomous integrity monitoring) based on a satellite selecting algorithm in a multimode satellite navigation system. The method comprises the steps of first determining space position information of satellites according to a navigation message and eliminating satellites with a small elevation angle according to a shielding angle; determining an observation matrix including only one clock correction item according to clock correction conversion factors in the navigation message; selecting p satellites from N visible satellites so as to be used for positioning calculation of a receiver, acquiring a satellite combination, which enables the GDOP (geometric dilution of precision) to be minimum, through the satellite selecting algorithm to act as calculating satellites, and determining a weight matrix in WLS (weighted least squares) according to parameters such as the carrier-to-noise ratio, the loop bandwidth, pre-check integral time and the like of satellite signals; carrying out RAIM availability detection according to a false alarm rate and a missed alarm rate which are preset by the receiver, and calculating a pseudo-range residual error threshold value after positioning according to the false alarm rate and a degree of freedom in Chi-squared distribution; carrying out global detection at first, then carrying out local monitoring in a circumstance that a fault satellite exists, determining calculation satellites again through satellite selection, and finally carrying out positioning calculation through selecting satellite combinations within the threshold value. The method disclosed by the invention is simple, high in fault recognition rate, not only applicable to multi-mode and multi-fault satellite navigation systems, but also applicable to single-mode and multi-fault satellite navigation systems, thereby providing new ideas for carrying out RAIM by a modern GNSS (global navigation satellite system).

A multi-ported storage area network (SAN) controller system with command completion that utilizes optimal port selection. The system determines the optimal port for command completion based on criteria such as loop bandwidth utilization or port throughput maximization, and allows data and response information to occur via the optimal port regardless of the receiving port. This is accomplished through port aliasing (spoofing) of port identities, in which the receiving port identity is substituted into a sending port identity by a distributed control entity. In this way, any port within the SAN may return data or status to the originating host.

Methods and apparatus for controlling a controlled oscillator using a phase-locked loop (PLL) or frequency-locked loop (FLL) having a digital loop filter with programmable filter parameters. An exemplary PLL (or FLL) includes a digital loop filter having one or more of the programmable filter parameters, which are changed by increments during operation in order to minimize disturbances (e.g., settling transients) as the loop bandwidth of the PLL is varied from a narrow loop bandwidth to a wide loop bandwidth, or vice versa. By changing the loop filter parameters in increments the loop bandwidth can be varied with substantially no perturbation. The end result is a much faster frequency switching time, improved settling dynamics, and predictable and stable loop operating performance. According to another aspect of the invention, one or more of the programmable filter parameters are changed in order to oppose a change in tuning sensitivity of the controlled oscillator (e.g., in order to maintain a constant loop bandwidth). By holding the loop bandwidth constant, switching time is maintained substantially constant under all conditions. This allows design and production margins to be reduced in a frequency agile system, and also relaxes the tuning sensitivity linearity requirements of the controlled oscillator.

This invention relates to the field of Inertial Navigation Systems (INS) and satellite navigation systems such as the Global Positioning System (GPS) and in particular relates to methods of integrating GPS and INS data in order to provide more accurate navigation solutions. The invention provides a method of improving the accuracy of a tightly coupled integrated INS and satellite radio navigation system in cases where the satellite navigation receiver has adaptive tracking loop bandwidths.

An approach for allocating bandwidth is disclosed. A request is detected from a terminal for capacity on a communication channel based on type of traffic transmitted from the terminal. A bandwidth allocation pattern designated for the terminal is retrieved, wherein the bandwidth allocation pattern is set based on a predetermined service plan associated with the terminal. Bandwidth over the communication channel is reserved for the terminal according to the bandwidth allocation pattern without feedback to the terminal. This arrangement has particular applicability to a satellite network that provides data communication services.

A system and method for improving the signal-to-noise ratio of a frequency generator suppresses phase noise and noise generated from mismatches in the internal generator circuits. This is accomplished using a modulation scheme which shifts spurious noise signals outside the loop bandwidth of the generator. When shifted in this manner, the noise signals maybe removed entirely or to any desired degree using, for example, a filter located along the signal path of the generator. In one embodiment, a Sigma-Delta modulator controls the value of a pulse-swallow frequency divider situated along a feedback path of a phase-locked loop to achieve a desired level of noise suppression. In another embodiment, a reference signal input into a phase-locked loop is modulated to effect noise suppression. In another embodiment, the foregoing forms of modulation are combined to accomplish the desired frequency shift. Through these modulation techniques, the signal-to-noise ratio of the frequency generator may be substantially improved while simultaneously achieving faster lock times.

A hybrid numeric-analog clock synchronizer, for establishing a clock or carrier locked to a timing reference. The clock may include a framing component. The reference may have a low update rate. The synchronizer achieves high jitter rejection, low phase noise and wide frequency range. It can be integrated on chip. It may comprise a numeric time-locked loop (TLL) with an analog phase-locked loop (PLL). Moreover a high-performance number-controlled oscillator (NCO), for creating an event clock from a master clock according to a period control signal. It processes edge times rather than period values, allowing direct control of the spectrum and peak amplitude of the justification jitter. Moreover a combined clock-and-frame asynchrony detector, for measuring the phase or time offset between composite signals. It responds e.g. to event clocks and frame syncs, enabling frame locking with loop bandwidths greater than the frame rate.

An adaptive closed loop transmit power control system which does not require extensive factory calibration of power control loop bandwidths and feedback detect path gain settings over the power transition ranges, frequency bands of operation, temperature, and supply voltage is disclosed. The system automatically compensates for any gain or slope variations in the analog feedforward and feedback paths to maintain system stability and meet performance specifications. The system achieves this by using an adaptive digital signal processing (DSP) system architecture within the feedback path of this closed loop power control system. The system eliminates the need for extensive factory calibration of such parameters as loop bandwidths and feedback detect path gain settings over power transition ranges, frequency bands of operation, temperature, and supply voltage.

A method of operating a phase locked loop (FIG. 5) for a wireless receiver is disclosed. The method includes receiving a reference signal (503) having a first and a second plurality of cycles and receiving a feedback signal (512) having the first and the second plurality of cycles. The feedback signal is compared (504) to the reference signal. A plurality of phase errors is produced for each cycle of (UP, FIG. 10A) the first plurality of cycles in response to the step of comparing.