Abstract: Methods and apparatus for conditioning communications signals based on detection of high-frequency in the polar domain. High-frequency events detected in a phase-difference component of a complex baseband signal in the polar domain are detected and used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain. Alternatively, high-frequency events detected in the phase-difference signal that correlate in time with low-magnitude events detected in a magnitude component of the complex baseband signal are used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain.

Abstract: A pulse amplitude modulation (PAM) signal generator that injects a copy of a pulse into the PAM baseband signal prior to frequency upconversion and power amplification. The pulse comprises a function of, or an extra copy of, a pulse in the PAM baseband signal. The pulse injector analyzes the PAM baseband signal for times when a predetermined threshold is exceeded and forms a pulse that is constructed and arranged to reduce the amplitude of the PAM baseband signal to a desired peak amplitude when the pulse is added to the PAM baseband signal.

Abstract: A communications transmitter having a main transmit chain for main signal features and one or more auxiliary transmit chains for auxiliary signal enhancements. In one embodiment, a communications signal is produced by digitally processing a representation of a desired signal so as to limit a trajectory of a signal represented by a resulting processed signal. A digital representation of a difference signal approximating a difference between the processed signal and the desired signal is produced. A first modulated, amplified signal is produced in dependence on the processed signal, and a second modulated, amplified signal is produced in response to the difference signal. The first modulated, amplified signal and the second modulated, amplified signal are combined to produce the desired signal. In this manner, a main transmit chain may be optimized with respect to other properties than signal quality (e.g.

Abstract: The present invention, generally speaking, provides a method of obtaining very accurate estimates of the phase and amplitude distortions introduced by radio frequency or microwave power amplifiers even where polar modulation is used.

Abstract: This invention, generally speaking, modifies pulse amplitude modulated signals to reduce the ratio of average power to minimum power. The signal is modified in such a manner that the signal quality remains acceptable. The signal quality is described in terms of the Power Spectral Density (PSD) and the Error Vector Magnitude (EVM).

Abstract: A system and method of modulation is described that initially over-modulates with an information signal at a scale that is N times an intended modulation scale and then subsequently, frequency-divides the over-modulated signal by the same factor of N to generate a modulated signal having the intended modulation scale wherein distortion of the resulting modulated signal is reduced by a factor of 20 log10(N)dB.

Abstract: The present invention, generally speaking, provides a method of obtaining very accurate estimates of the phase and amplitude distortions introduced by radio frequency or microwave power amplifiers even where polar modulation is used.

Abstract: A low-cost emergency locator beacon (ELB) device that transmits an identifying serial number in addition to the beacon signal. This transmission includes an audio modulated Manchester encoded digital version of the serial number, and an analog, voice synthesized version of the serial number. In one embodiment, the device incorporates a receiver that enables the user of the device to enter into two-way, direct voice communication with a rescuer. The device also includes an automatic receive function which facilitates operation of the device by users not aware or not able to operate the device. In another embodiment, the ELB device includes an inhibit function which prevents non-emergency, ELB device to ELB device communication.