Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By frequency
Reexamination Certificate
1999-04-07
2001-06-26
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By frequency
C327S045000
Reexamination Certificate
active
06252428
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of signal detection, and more particularly, to the detection of a sinusoidal signal.
BACKGROUND OF THE INVENTION
There are many applications in which the detection of a sinusoidal signal is required. For example, in a multipoint data network, the beginning of a transmission by one station on the network may be indicated by a timing signal formed by one or more sinusoidal signals. Such a timing signal is recognized by receivers on the network as an indication that a packet of data will follow on the network. Accurate and rapid detection of a sinusoidal signal is critical in such an application. However, this is merely one example of the use of a sinusoidal signal detector.
Other examples of applications in which sine wave detection is used includes position detectors (U.S. Pat. No. 5,801,835), and speech recognition devices. In most applications, it is desirable to make the determination that the signal is a sinusoidal signal as quickly as possible. It is also desirable to do so in a manner that employs a relatively minimal amount of logic to implement the detection scheme.
SUMMARY OF THE INVENTION
There is a need for methods and apparatus to detect a sinusoidal signal in a manner that is not computationally intensive yet provides a fast detection. The detection scheme should be accurate, but should also allow for an adjustable amount of noise or imperfection in the sinusoidal signal.
This and other needs are met by the present invention which provides a sinusoidal signal detector having a sampling circuit that samples a received signal. An error signal generator receives as inputs two previous samples of the received signal and a current sample of the received signal. The error signal generator generates an error signal based upon the previous and current samples. A comparison circuit compares the generated error signal for the current sample to an error threshold value. The comparison circuit generates a threshold comparison signal that indicates whether the generated error signal is below the error threshold value. A determination circuit then determines whether the received signal is a sinusoidal signal based on the threshold comparison signals that are generated for a plurality of samples.
The detector of the present invention rapidly and with a relatively minimal amount of logic determines the presence of a sinusoidal signal on an input signal line by predicting the current sample from the previous samples if the signal was a perfect sinusoidal. By comparing the two previous samples of a received signal to a current sample, and comparing the error in the prediction to an error threshold, a plurality of samples may be used to determine whether a sinusoidal signal is detected. If the sinusoidal signal was not perfect, but close, so that a small number of samples did not pass the error threshold, but the majority of the samples are within the error threshold, a sinusoidal signal will still be detected. The present invention operates on any sinusoidal signal that has a known frequency, but has an unknown amplitude and any unknown phase.
The earlier stated needs are also met by another embodiment of the present invention which provides a method of detecting a sinusoidal signal that has an unknown amplitude and an unknown phase. The method includes the steps of sampling a received signal to produce a plurality of samples. A current sample is predicted based upon the previous samples. An error signal is produced as a function of a deviation of an actual current sample from a predicted current sample. The error signal is compared to an error threshold. It is then determined whether the input signal is a sinusoidal signal as a function of the number of samples for which the error signal produced is below the error threshold.
The foregoing and other features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4509016 (1985-04-01), Yamamoto
patent: 5410196 (1995-04-01), Izuta
patent: 5801835 (1998-09-01), Mizutani et al.
Barsoum Maged F.
Chang Hungming
Gershon Eugen
Huynh Muoi V.
Hwang Chien-Meen
Advanced Micro Devices , Inc.
Wells Kenneth B.
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