Abstract: Systems and methods for operating a communication device so as to mitigate intermodulation interference to a signal. The methods comprise: continuously monitoring several communication channels by the communication device; using a noise floor level estimate of the communication device to detect when the communication device is under an influence of hig interference; determining an optimal level of attenuation to be applied by a variable attenuator of the communication device's receiver so as to mitigate the influence of intermodulation interference to the signal; and selectively adjusting an amount of attenuation being applied by the variable attenuator to achieve the optimal level of attenuation for mitigating intermodulation interference.

Abstract: Systems and methods for mitigating broadband and/or Intermodulation (“IM”) interference. The methods comprise: monitoring performance of at least one demodulator performance metric of a communication device; detecting when the communication device is under or will be under an influence of IM interference based on a performance of the at least one demodulator performance metric; determining an improved level of gain to be applied to (i) a variable attenuator of the communication device or (ii) a variable gain low noise amplifier of the communication device; and selectively adjusting an amount of gain being applied by the variable attenuator or variable gain low noise amplifier based on the improved performance achieved with new level of attenuation.

Abstract: Systems and methods for operating a communication device so as to mitigate intermodulation interference to a signal. The methods comprise: continuously monitoring several communication channels by the communication device; using a noise floor level estimate of the communication device to detect when the communication device is under an influence of hig interference; determining an optimal level of attenuation to be applied by a variable attenuator of the communication device's receiver so as to mitigate the influence of intermodulation interference to the signal; and selectively adjusting an amount of attenuation being applied by the variable attenuator to achieve the optimal level of attenuation for mitigating intermodulation interference.

Abstract: Symbol sampling in a high time delay spread interference environment includes acquiring (602) a time varying baseband waveform. The waveform has a signal amplitude that varies between one of a plurality of symbol states. The waveform is sampled (603) at a rate of m times the symbol rate. During an evaluation time, an error value is calculated (604, 606) for each of m data sample positions. Each of the error values comprises an average distance between the measured value of the waveform as indicated by the data sample and a closest known symbol value. The error values are used to create an error surface. Thereafter, the error surface is modeled as a quadratic and an optimal sample time is determined (608, 610, 612) based on finding the time location where the quadratic surface is minimum. A sinc interpolator is then used to resample the data.

Abstract: Symbol sampling in a high time delay spread interference environment includes acquiring (602) a time varying baseband waveform. The waveform has a signal amplitude that varies between one of a plurality of symbol states. The waveform is sampled (603) at a rate of m times the symbol rate. During an evaluation time, an error value is calculated (604, 606) for each of m data sample positions. Each of the error values comprises an average distance between the measured value of the waveform as indicated by the data sample and a closest known symbol value. The error values are used to create an error surface. Thereafter, the error surface is modeled as a quadratic and an optimal sample time is determined (608, 610, 612) based on finding the time location where the quadratic surface is minimum. A sinc interpolator is then used to resample the data.

Abstract: Method for optimizing the delay spread performance of a radio receiver (200) includes evaluating (306) a delay spread environment to determine if a desired RF signal is being received under conditions of low delay spread or high delay spread. If a low delay spread condition, the baseband digital data signal is filtered using a narrow filter (310). Otherwise, the signal is filtered using a wide bandwidth filter (312) having a bandwidth wider than the narrow filter. The center frequency of the wide bandwidth filter is selectively shifted (316, 320) in accordance with a predetermined frequency offset if a second received power level of an interfering signal in an adjacent channel exceeds the first received power level by a predetermined threshold amount. This frequency shift of the filter allows for improved delay spread performance while minimizing any performance degradation when an interfering signal is present on an adjacent channel.

Abstract: Peak fade depth is measured (202) over a period of time, and a bandwidth of a channel filter (104) is then determined (206) according to the measured peak fade depth (202). In preferred embodiments the average peak fade depth over two or more time slots is used. In a specific embodiment, an ? filter (206) is used to determine the bandwidth of the matched filter (104), in which ? is determined based upon the measured peak fade depth (204). In various embodiments, peak fade depth is correlated to the Doppler shifting of the channel, which in turn is used to determine the bandwidth of the matched filter by way of the ? parameter. Hence, a non-linear equation can be used to determine the value of ? which yields a minimum bit error rate for the matched filter (104).

Abstract: Peak fade depth is measured (202) over a period of time, and a bandwidth of a channel filter (104) is then determined (206) according to the measured peak fade depth (202). In preferred embodiments the average peak fade depth over two or more time slots is used. In a specific embodiment, an ? filter (206) is used to determine the bandwidth of the matched filter (104), in which ? is determined based upon the measured peak fade depth (204). In various embodiments, peak fade depth is correlated to the Doppler shifting of the channel, which in turn is used to determine the bandwidth of the matched filter by way of the ? parameter. Hence, a non-linear equation can be used to determine the value of ? which yields a minimum bit error rate for the matched filter (104).

Abstract: These and other objects of the present invention are achieved using an Adaptive Multi-Path Filter (AMPF) which eliminates audibly objectionable click noise generated at the output of an FM discriminator to prevent audible distortion or other corruption of the desired signal which may include voice and low speed digital data. Clicks are detected at the discriminator output using a colored-noise, matched filter designed and adapted to the click signature/shape as well as to the desired signal characteristics. The colored-noise matched, filter output is then compared to an adaptive threshold. When the threshold is exceeded, a click is registered as detected. Click duration is then estimated. An estimate of the desired signal is generated and that replaces the originally received data signal estimate within the click duration region.

Abstract: A location dependent signal processor for radiant energy detector arrays which include two-dimensional spatial filtering and/or background normalizing, with means providing programmed control of the signal processor filter weighting and normalizer thresholding operations as a function of the location of each successive output pixel with respect to the periphery of the detector array, so as to enable the signal processor to minimize the effects of initialization and wrap-around pixels on the processor signal output.