Abstract: A circulator is used as a notch filter having a notch at a notch frequency band outside its frequency band of operation as a circulator. It has been observed that circulators operate as a notch filter at a relatively narrow band of operation outside its typical band of operation as a circulator. In certain embodiments, the circulator operates as a narrowband notch filter with sharp edges. Such a notch filter can be used between frequency bands carrying communications signals to reduce energy from one frequency band from spilling into a different frequency band. Since the notch has been observed to be relatively narrow and deep with sharp edges, such a notch filter can be used to reduce the guard bands between frequency bands, thereby increasing the amount of bandwidth that can de used to transmit communications signals. Furthermore, since a typical ferrite circulator is a relatively low cost component, the resulting notch filter can also be of low cost.

Abstract: A rate control system is provided for a link between a first node, such as an RNC and a second node, such as a Node B, within a wireless communications system where at least one user is provided a rate over the link as a function of link load. For example, the rate control system sets at least one user to a reduced rate on the link as a function of the rates of a plurality of users on the link. In certain embodiments, the rate control system controls the rate by selecting the size of a transport format block used to transport data for a user over the link during a transmission interval. The size of the transport format block can be selected by changing the number of transport blocks used to form the transport format block as a function of the total user data to be transported over the link at that time. The rate of data offered to the link can be controlled by the way user data is mapped into the transport format blocks used to send user data over the link.

Abstract: A system and method for preventing a call from being dropped changes from a first set of serving base station(s) for the call to a second set of serving base station(s) which can be determined independently by both the wireless unit and the wireless communications system. As such, the wireless unit can attempt to recover the call using the second set of serving base station(s) even without the availability of a communication link between the wireless unit and the current set of serving base station(s). The wireless communications system can independently determine a second set of serving base station(s) for the call using information known at both the wireless communication system and at the wireless unit before the communication link was severed.

Abstract: A digital transmitter converts a digital signal into analog form with a digital to analog converter (DAC) and uses an analog signal image produced from the DAC to provide an analog signal at a transmission frequency and/or uses a projected analog signal image to produce analog signals for transmission. Rather than removing analog signal images with a low pass filter at the output of the DAC and/or using analog signal images and analog mixers for frequency conversion, the digital transmitter uses the analog signal images from the DAC to produce the analog signals at the desired frequency/frequencies. By setting and/or adjusting the conversion rate for the DAC and/or the digital signal frequency/frequencies, the analog signal images produced from the DAC can be positioned in the desired frequency band(s). For example, the digital transmitter can position the digital signals within non-overlapping portions of a conversion bandwidth defined as one-half the conversion rate for the DAC.

Abstract: A predistortion system and method uses an inner predistortion function to adjust a signal being input into a distortion generating circuit and at least one outer predistortion function to adjust the signal being input into the inner predistortion function. Thus, the inner predistortion function can reduce the distortion from the distortion generating circuitry, and any remaining distortion can be reduced by the outer predistortion function.

Abstract: A key update system uses information in an update message from a communications system to generate a new key and perform a bidirectional validation of the new key. After a unit validates the new key, at least a portion of information from the update message is used by the communications system to validate the new key. As a result, the communications system is not required to generate and transmit a separate authentication challenge to validate the new key. For example, a wireless communications system can send an update message with a sequence RANDSSD to the wireless unit. The wireless unit generates a new SSD using at least a portion of the sequence RANDSSD, and the wireless unit uses at least a portion of the new SSD to generate a signature value AUTHBS to validate the new key and thereby the home authentication center that initiated the update of the SSD.

Abstract: A predistortion system compensates or equalizes the phase and/or amplitude response over frequency of at least a portion of a signal path prior to the distortion generating circuitry, such as an amplifier, and/or of at least a portion of a feedback path after the distortion generating circuitry. For example, in a power amplification system using predistortion, an equalizer on the signal path adjusts the phase and amplitude of a predistorted signal across frequency to compensate for the amplitude and phase response of circuitry on the signal path, such as the amplitude and phase response of analog filters in the up-conversion process. After amplification, an equalizer on a feedback path adjusts the phase and amplitude across frequency of the signal representing the output of the amplifier to compensate for the amplitude and phase response of circuitry, such as analog filters in the down-conversion process, on the feedback path.

Abstract: An amplifier distortion reduction system obtains a distortion signal from the amplifier output and feeds the distortion signal back to the input side of the amplifier to cancel with the distortion produced at the amplifier output. For example, a signal to be amplified by an amplifier is received on a main signal path. The amplifier produces an amplified output with a non-distortion spectrum and a distortion spectrum. A sample of the amplified output is produced from the main signal path and placed on a feedback path. On the feedback path, the distortion spectrum is obtained from the sample amplified output. The distortion spectrum is phase and/or amplitude adjusted to produce the distortion signal. The distortion signal is placed onto the main signal path at the input side of the amplifier with the signal to be amplified to destructively combine with the distortion produced from the amplifier in amplifying the signal to be amplified.

Abstract: A procedure for triggering a handdown or a handoff a mobile station served by a base station of a cellular wireless communication system. A tolerable path loss for signal links between the base station and a mobile station located within the base station's cell, is initially determined. A control signal is radiated at a known transmit power level from the base station over its cell. A receive power level threshold is determined for the control signal for reception by the mobile station, according to the transmit power level and the tolerable path loss. A handoff of the mobile station is triggered after deriving the received power level of the control signal at the mobile station, and determining that the received power level is less than the receive power level threshold.

Abstract: A signal amplification system independently adjusts the relative phase and/or amplitude between the signal components and/or the relative phase and/or amplitude between the distortion components to improve the combination of corresponding components. For example, a signal amplification system has first and second amplifier paths carrying replicas of signal components. On the first amplifier path, a first amplifier amplifies signal components and generates distortion components. A replica of the amplified signal components and distortion is provided to a coupling path. On the coupling path, the distortion components are isolated by canceling the signal components, and the distortion components are then amplitude and/or phase adjusted without a corresponding adjustment to the phase and/or amplitude of the signal components. The adjusted distortion components are coupled onto the second path where the signal components and the adjusted distortion components are amplified by a second amplifier.

Abstract: A signal notching system reduces signal peaks by notching the peak of a signal above a threshold to produce a notched signal. The notched signal is then filtered to produce a resulting signal with a reduced peak amplitude. For example, in an implementation where the signal is represented by signal samples, the peak notching system first locates a peak sample that is beyond a threshold, such as a sample representing a positive peak sample of a peak above the threshold. Once a peak sample is located, the peak notching system adjusts the peak sample by an amount which is a function of the amount that the peak sample is beyond the threshold, effectively creating a notched signal with a one sample notch at the peak. The peak notching system filters the notched signal to fill in the notch to produce a signal with a reduced peak.

Abstract: A packaging system includes a medium which transports energy in a first form away from a radiation point in a device to where the energy can be converted to a second form without damaging the device or effecting other devices. In certain embodiments, the medium can inhibit the propagation of energy in the second form. For example, in an optical coupling device, the medium includes a substrate adjacent to the radiation point which transports light energy away from the radiation point to a housing which converts the light energy into thermal energy away from the radiation point. In accordance with another aspect, the packaging system suspends at least a portion of the device, for example, to protect the device against a third form of energy. For example, in the optical coupling device, the medium includes an air gap which separates the radiation point from the substrate to suspend at least a portion of the device.

Abstract: A pilot adjusting system adjusts the power level of the pilot relative to the power level of the input signal. For example, the pilot adjusting system detects the power level of the input signal on the signal path leading to an RF amplifier. In response to the power level of the input signal, the pilot adjusting system adjusts the power level of the pilot signal which is injected into the signal path prior to the RF amplifier. In certain embodiments, the pilot adjuster adjusts the pilot power level to maintain a desired input signal to pilot signal ratio at the input to the RF amplifier for the input signal range of the RF amplifier. As such, if the input signal power level drops 30 dB, the pilot adjuster reduces the power level of the pilot signal by 30 dB, thereby maintaining the input signal to pilot ratio throughout the input range of the RF amplifier.

Abstract: A complex spreading and/or scrambling code sequence generation system uses a first complex code sequence having at least two components and a second complex code sequence having at least two components. The components of the first complex code sequence are respectively mixed with the corresponding components of the second complex code sequence to generate the complex scrambling code sequence. In doing so, an offset between the components of the complex scrambling code sequence is achieved for the same and/or different users. The complex scrambling code sequence can be used for spreading, scrambling, de-spreading or descrambling an information signal.

Abstract: A high priority and/or emergency overload access control system treats a wireless unit as a higher priority wireless unit when the wireless unit is attempting to access a wireless communications system with a high priority call, such as an emergency call. For example, the overload access control system can recognize if the wireless unit is attempting to initiate a call to an emergency number. If so, the wireless unit can perform a persistence test as an emergency class (e.g. overload class 10-15) wireless unit in attempting to access the wireless communications system. Thus, the wireless unit will experience an increased probability of passing the persistence test and thereby reducing the persistence delay in attempting to access the wireless communications system with the emergency call.

Abstract: The timing of a carrier signal is tracked in a receiver. The receiver receives a signal produced by a transmitter having a single frequency source which is used to generate a reference clock frequency and a carrier signal frequency, there being a fixed, predetermined relationship between the reference and carrier frequencies. In the receiver there is a single frequency source which is used to generate a reference clock frequency and a carrier reference signal frequency, there being a fixed, predetermined relationship between the reference and carrier reference frequencies. The fixed, predetermined relationship in the transmitter and the receiver is the same.

Abstract: The present invention involves an adaptive digital radio communications architecture which can be reconfigured by reprogramming at least one programmable device, and thus more efficiently use the available bandwidth of a time-varying RF channel and/or to provide a flexible and adaptive digital communications system. In certain embodiments, the programmable device uses a Programmable Logic Device (PLD) to perform the digital communications processing functions of the transmitter or the receiver of a radio communications system. In this context, PLD is a general term representing a family of programmable logic devices; examples of this family are a Programmable Array Logic (PAL), a Complex PLD (CPLD), and a Field Programmable Gate Array (FPGA). The architecture is reconfigurable in the sense that any or all of the digital communications processing algorithms can be modified by reprogramming the PLD.

Abstract: An integrated circuit (shown below dashed line A--A) for a voltage controlled oscillator comprises a first transistor (T.sub.1) having its collector coupled to a first port (Port 1) via a filter comprising a capacitor (C.sub.f) and an inductor (L.sub.f) and its emitter coupled to the emitter of a second transistor (T.sub.2) whose collector is coupled to a second port (Port 2). The collector of the first transistor is also coupled via a capacitive divider (C.sub.1, C.sub.2) to the base of the second transistor. The base of the first transistor is AC decoupled (C.sub.3). The emitters of the first and second transistors are fed by a current source (I.sub.1). A capacitor (C.sub.s) connects the base of the second transistor to the first port. The first and second ports are for connection to an external resonator (L.sub.1, D.sub.1, C.sub.p, L.sub.p) (shown above dashed line A--A) where C.sub.p and L.sub.

Abstract: A nested feed forward distortion reduction system, which reduces the distortion from a main amplifier on a main signal path, uses a nested feed forward arrangement for the correction amplifier to reduce the distortion produced from the correction amplifier. In reducing the distortion from the correction amplifier(s) and using progressively higher quality correction amplifier(s), the nested feed forward arrangement produces an improved, more stable representation of the distortion from the main amplifier, thereby alleviating the need for variable gain and/or phase control in producing amplified signal with reduced distortion.

Abstract: A coherent optical system includes an optical coupler or combiner for combining a received upstream optical signal and an optical local oscillator signal. The coherent optical system further includes a coherent optical receiver which is configured to receive and process the combined optical signal from the optical coupler to retrieve upstream information from the upstream optical signal. In certain embodiments, the coherent optical communication system includes a central office having an optical source for generating a composite downstream optical signal made up of downstream optical signals of particular wavelengths (or sets of wavelengths).