Adaptive interpolation

Abstract

A method and apparatus for acquiring an analog signal. The method of the invention comprising the steps of acquiring a first portion of the analog signal by a first channel, the first portion of the analog signal spanning a first bandwidth range, and acquiring a second portion of the analog signal by a second channel, the second portion of the analog signal spanning a second bandwidth range adjacent the first bandwidth range. At least one spur in the signal acquired by the first channel corresponding to a portion of the analog signal that should have properly been acquired by the second channel is offset with an opposite spur in the second channel.

Description

BACKGROUND OF THE INVENTION [0001] The present invention is directed to real time oscilloscopes, and more particularly to real time oscilloscopes employing a bandwidth extension scheme (i.e. Digital Bandwidth Interleaving), such as that described in U.S. patent application Ser. No. 11 / 281,075, titled HIGH BANDWIDTH OSCILLOSCOPE, filed Nov. 17, 2005 (“the '075 application”), currently pending, the entire contents thereof being incorporated herein by reference. In accordance with the disclosure of this pending patent application, each of a plurality of channels (two, for example, which will be referred to as LF (low frequency) and HF (high frequency)) receive a portion of an input signal corresponding to a specific frequency band. As described in the above application, additional processing is performed on this split signal for acquiring and digitizing the signal. In accordance with the present invention, further modification to this process of the '075 application is presented. [0002...

AI Technical Summary

Benefits of technology

"The present invention proposes a method and apparatus for canceling out spurs that occur in a system. The spurs are caused by non-ideal filtering and can result in errors in the signal interpretation. The invention uses adaptive upsampling to replace the traditional truncated sin x / x function with a new function that takes into account the non-ideal filtering. The new function is designed to have the same effect on the signal as the hardware non-ideal filtering, so that the software and hardware spurs cancel each other out. This cancellation results in a more accurate and reliable signal interpretation."

Problems solved by technology

Secondly, the inventor of the present application has recognized another phenomenon hindering the use of the maximum theoretical available bandwidth.

This phenomenon causes a problem even if all signals are received in the correct frequency channel.

But, when approaching the Nyquist limit (fS / 2), the truncated Sinc filter fails to reject an undesired frequency because it is just too close to the desired frequency, and both are part of a curve with a finite slope.

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