Abstract: Conventional EAS systems, such as ULTRA*MAX, use noncoherent detection and a highly nonlinear post detection combining algorithm. It is well known that using the phase information that is present in the received signal has advantages in detection performance. This is difficult to do in conventional ULTRA*MAX receiver because of the combination of a narrow signal bandwidth and short receive window duration. A method to incorporate signal phase into the detector by differential coherent combining is provided, which significantly improves processing gain that was not previously obtainable.

Abstract: Conventional EAS systems, such as ULTRA*MAX, use noncoherent detection and a highly nonlinear post detection combining algorithm. It is well known that using the phase information that is present in the received signal has advantages in detection performance. This is difficult to do in conventional ULTRA*MAX receiver because of the combination of a narrow signal bandwidth and short receive window duration. A method to incorporate signal phase into the detector by differential coherent combining is provided, which significantly improves processing gain that was not previously obtainable.

Abstract: Digital implementation of electronic article surveillance (EAS) detection filtering for pulsed EAS systems is provided. Embodiments include direct implementation as a quadrature matched filter bank, as an envelope detector, a correlation receiver, and as a discrete Fourier transform. Pre-detection nonlinear filtering is also provided for impulsive noise environments.

Abstract: A ringdown canceller is provided for electronic article surveillance (EAS) tag response processing, which uses two adaptive replica signals and compares the replica signal phase to the receive signal phase to determine if there is a stationary EAS tag in the interrogation or detection zone. The adaptive replica buffers allow the system to adjust to changing ambient conditions, and adjust rapidly to an EAS tag that suddenly appears in the detection zone and becomes stationary, or to a stationary EAS tag that suddenly leaves the detection zone. The ringdown response of the transmitter circuit is constant, just like a stationary tag, and is removed from the receive signal in the same manner as a stationary tag.

Abstract: Digital implementation of electronic article surveillance (EAS) detection filtering for pulsed EAS systems is provided. Embodiments include direct implementation as a quadrature matched filter bank, as an envelope detector, a correlation receiver, and as a discrete Fourier transform. Pre-detection nonlinear filtering is also provided for impulsive noise environments.

Abstract: A distributed wireless phase locked loop system for synchronizing the transmit carrier's modulating waveform, such as the transmitter pulse timing in a pulsed EAS system and the transmit sweeping function for swept RF synchronization, is provided. To remove the effect of phase noise on the power line signal, a phase locked loop is used to filter this signal. The filtered output is used as a reference to a second phase locked loop tied to a numerically controlled oscillator and the received signal to provide a distributed phase looked loop algorithm that is wireless, and automatically synchronizes adjacent EAS systems.

Abstract: In an EAS system and method, a reference antenna is used to spatially separate the interference and tag signal allowing the interference signal to be removed, which improves performance of the EAS receiver. The reference antenna is coupled to the system by an adaptive filter, which can be a software filter that is continually adapting itself to optimum performance. The continuous adaptation obviates the need for manually tuning the coupling network and permits the system to perform at its optimum level over long periods of time.

Abstract: A signal received in an electronic article surveillance system is comb-filtered to remove interference. A second comb-filtering function is provided to detect occasions when the first comb-filtering generates ringing artifacts in response to impulsive noise. Alarm indications are inhibited at times when the artifacts due to impulsive noise are detected. Bandwidths of the filtering functions are adjustable in response to operator input.

Abstract: An electronic article surveillance system includes a signal generator for generating an interrogation signal in an interrogation zone, an antenna which receives a signal present in the interrogation zone, and interference cancelling circuitry for cancelling interference components in the signal received by the antenna. The interference cancelling circuitry includes a hybrid interference component cancelling loop in which a digital interference estimate signal is formed and converted into an analog estimate signal, and the analog estimate signal is subtracted from an input analog signal. The resulting difference signal is processed with a hybrid automatic gain control loop. A digitized signal, formed from the resulting difference signal, is subjected to digital interference cancellation processes in addition to the hybrid interference component cancellation process.

Abstract: A signal received in an electronic article surveillance system is subjected to a nonlinear comb filtering function to remove interference. The nonlinear comb filtering is provided by performing a polyphase decomposition of an input digital signal, nonlinear filtering of the resulting subsequences, and then synthesizing the nonlinear-filtered subsequences. A median filter may be used as the subsequence filtering function. A linear comb filtering function may be provided downstream from the nonlinear comb filter to provide additional attenuation of interference.

Abstract: A signal received by an electronic article surveillance system is processed using a neural network processing algorithm to determine whether an electronic surveillance marker of a predetermined kind is present. The raw received signal is processed to generate a small number of parameter values to be provided as inputs for the neural network. The neural network processing distinguishes between two different types of surveillance marker.

Abstract: A semiconductor device inspection template for use in visual inspection of semiconductor die or packages includes a selectively patterned transparent film mounted in a sleeve adapted for rapid placement and removal from an optical inspection instrument's optical tube.