Adaptive interference cancellation method
First Claim
1. A method of canceling an undesired signal from an input signal, the method comprising the steps of,receiving the input signal, scanning the input signal over a frequency operating bandwidth, detecting the presence of a detected signal having frequency components within the frequency operating bandwidth, determining when the detected signal is the undesired signal, determining when the detected signal is a pulse signal, determining when the detected signal is a continues wave signal, determining when the detected signal is the undesirable signal when the pulse signal has a duration greater than a preset value, determining when the detected signal is the undesirable signal when the continuous wave signal has the detected center frequency and the detected bandwidth respectively different than a predetermined desired center frequency and a predetermined desired bandwidth, isolating the detected signal within a frequency bandwidth as an isolated undesired signal, and subtracting the isolated undesired signal from the input signal.
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Abstract
The design and performance of an analog cancellation system is presented. The system generates either narrow or wideband nulls in order to minimize the effect of interfering signals on a receiver. A microcontroller directs the detection and classification of the interfering signal relative to frequency, amplitude and modulation, such as pulse-width or continuous wave modulation. A sampled version of the interfering signal at frequency, fi, is phase-inverted, amplified, and vector-summed with the input signal stream to null the interfering signal at fi. The microcontroller also monitors and adjusts the cancellation systems'"'"' circuit parameters to minimize any residual interfering signal at fi or respond to changes in the interference. The example system operates from 100-160 MHz, and can generate wideband nulls over a 5MHz bandwidth with a 15dB depth attenuation or narrowband nulls with a Q greater than 200, and with a null depth greater than 30dB.
47 Citations
11 Claims
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1. A method of canceling an undesired signal from an input signal, the method comprising the steps of,
receiving the input signal, scanning the input signal over a frequency operating bandwidth, detecting the presence of a detected signal having frequency components within the frequency operating bandwidth, determining when the detected signal is the undesired signal, determining when the detected signal is a pulse signal, determining when the detected signal is a continues wave signal, determining when the detected signal is the undesirable signal when the pulse signal has a duration greater than a preset value, determining when the detected signal is the undesirable signal when the continuous wave signal has the detected center frequency and the detected bandwidth respectively different than a predetermined desired center frequency and a predetermined desired bandwidth, isolating the detected signal within a frequency bandwidth as an isolated undesired signal, and subtracting the isolated undesired signal from the input signal.
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9. A method of canceling an undesired signal from an input signal, the method comprising the steps of,
receiving the input signal, coarsely scanning the input signal for a detected signal over a frequency operating bandwidth in coarse bandwidth steps, detecting the presence of the detected signal within one of the bandwidth steps when the detected signal has a detected amplitude above a threshold level, finely scanning the input signal for determining a detected center frequency of the detected signal, a detected bandwidth of the detected signal and the detected amplitude of the detected when above the threshold level, determining when the detected signal is a wideband detected signal or a narrowband detected signal when the detected bandwidth is greater or lesser, respectively, than a predetermined bandwidth, determining when the detected signal is the undesired signal, determining when the detected signal is a pulse signal, determining when the detected signal is a continues wave signal, determining when the detected signal is the undesirable signal when the pulse signal has a duration greater than a preset value, and determining when the detected signal is the undesirable signal when the continuous wave signal has the detected center frequency and the detected bandwidth respectively different than a predetermined desired center frequency and a predetermined desired bandwidth, isolating the detected signal within an isolating frequency bandwidth as an isolated undesired signal, the isolating frequency bandwidth is an isolating wide bandwidth or an isolating narrow bandwidth when the detected signal is respectively wideband or narrowband, amplifying the isolated undesired signal to an isolated amplitude to match the detected amplitude, phase shifting the isolated undesired signal by an isolated phase for coherency with the input signal, and subtracting the amplified, phase shifted, isolated undesired signal from the input signal.
Specification