Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-04-16
2001-04-24
Jastrzab, Jeffrey R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S032000, C128S903000
Reexamination Certificate
active
06223083
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to communication receivers adapted for use with an implantable medical device. More particularly, the present invention pertains to a receiver employing a digital filter for filtering demodulated data corresponding to data impressed on a carrier signal and transmitted from an implantable medical device.
BACKGROUND OF THE INVENTION
Various implantable medical devices have been developed that receive information from one or more physiologic sensors or transducers. A typical physiologic sensor transduces a measurable parameter of the human body, such as blood pressure, temperature or oxygen saturation for example, into corresponding electrical signals. At the appropriate time, the physiologic data acquired by an implantable medical device is uplinked to an external receiving system, such as a programmer, for storage and analysis.
In many implantable medical device applications, a radio frequency (RF) telemetry approach is used by which data acquired by an implantable medical device is impressed on a carrier signal and transmitted to an external receiving system during an data uplink procedure. A demodulation circuit is typically provided in the receiving system that recovers the physiologic information signal from a modulated signal received from the implantable medical device. An analog low pass filter is typically used to extract the physiologic information signal from the demodulated signal, which generally contains noise and exhibits other undesirable corruptive characteristics.
In many conventional receiving systems, noise is introduced into the RF signal channel from a number of traditional sources which corrupts the demodulated data signal. In addition, high frequency noise components are introduced into the demodulated data signal as a result of the demodulation process. Moreover, receiving systems that employ analog components generally experience problems that normally arise from processing of analog signals with relatively large signal swings and large bandwidths. Such problems include bit distortion due to low-to-high and high-to-low slew rate differences, failure to follow distortion (i.e., DC level shifts) caused by parasitic capacitances and charging of capacitors, failure to follow distortion caused by data in which there may be more positive data than negative data, and inter-symbol interference caused by tradeoffs in analog filter performance.
A traditional approach to addressing such signal corruption and processing problems involves the use of a programmable analog low pass filter, such as use of filters implemented in analog integrated circuits (IC's) and analog switches. Another traditional analog approach involves the use of a switched capacitor filter and an adjustable clock. Although analog low pass filtering provides for some degree of improvement in the extracted data signal, a successful analog low pass filtering circuit implementation is typically complex and requires a significant amount of printed circuit board space.
Further, a traditional analog low pass filtering approach typically involves a “custom” design, which is generally intolerant to changes in data rates and the frequency response of the filter. Such custom designs tend to be both expensive and limited in terms of the potential to use standardized, readily available, and relatively inexpensive electronic components. Still further, the use of analog components in a particular filter design is generally associated with increased power consumption, in contrast to a fully digital implementation. Increasing the power consumption requirements of the receiving system, including the filtering circuitry, may pose a significant problem in portable and small scale receiver applications.
Various implementations of RF telemetry systems directed for use with an implantable medical device are known in the art, examples of which may be found in the issued U.S. Patents listed in Table 1 below.
TABLE 1
U.S. Pat. No.
Inventor(s)
Issue Date
4,281,664
Duggan
August 4, 1981
4,494,545
Slocum et al.
January 22, 1985
4,556,063
Thompson et al.
December 3, 1985
4,562,840
Batina et al.
January 7, 1986
4,571,589
Slocum et al.
February 18, 1986
4,681,111
Silvian
July 21, 1987
4,757,816
Ryan et al.
July 19, 1988
4,949,299
Silvian
July 31, 1990
5,058,581
Silvian
October 22, 1991
5,107,833
Barsness
April 28, 1992
5,127,404
Wyborny at al.
July 7, 1992
5,241,961
Henry
September 7, 1993
5,264,843
Silvian
November 23, 1993
5,292,343
Blanchette et al.
March 8, 1994
5,300,093
Koestner et al.
April 5, 1994
5,312,453
Shelton et al.
May 17, 1994
5,383,912
Cox et al.
January 24, 1995
5,475,307
Silvian
December 12, 1995
5,620,472
Rahbar
April 15, 1997
The patents listed in Table 1 hereinabove are hereby incorporated by reference herein in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, the Detailed Description of Various Embodiments, and the claims set forth below, many of the devices and methods disclosed in the patents identified below and listed in Table 1 above may be modified advantageously by using the teachings of the present invention.
SUMMARY OF THE INVENTION
The present invention has certain objects. That is, various embodiments of the present invention provide solutions to one or more problems existing in the prior art with respect to telemetry receiving systems for use with implantable medical devices. Such problems associated with prior art receiving systems include, for example, those that arise from processing analog signals with relatively large signal swings and large bandwidths; an inability to utilize standardized, low-cost, and readily available electronic components, relatively large analog components that consume appreciable amounts of power and require a significant amount of printed circuit board space, and additional problems identified in the Background of the Invention.
Various embodiments of the present invention have the object of solving at least one of the foregoing problems. While some systems have been able to solve the general problem of filtering high frequency content from demodulated data produced by an implantable medical device, such approaches have generally resulted in implementations that increase noise, reduce frequency response and data rate adjustability, increase design and integration complexity, and increase the power consumed, and space occupied by, the filtering circuitry. It is therefore another object of the present invention to provide an improved apparatus and methodology for filtering demodulated RF data corresponding to data transmitted by an implantable medical device that fulfills at least one of the foregoing objects.
In comparison to known implementations of receiving system circuitry, various embodiments of the present invention may provide one or more of the following advantages: providing the opportunity to utilize standardized, low-cost, digital components in the filtering circuit design, eliminating all analog elements in the filtering circuitry, reducing the power and circuit board/chip space required to support the filtering circuitry, and increasing the adjustability of the filtering circuitry in terms of data rates and frequency response characteristics.
Some embodiments of the invention include one or more of the following features: a circuit for receiving and filtering data received from a body implantable medical apparatus, including an antenna, a demodulator circuit coupled to the antenna, and a digital filter that removes high frequency content of a demodulated digital information signal to produce a filtered digital information signal; a digital filter that comprises a multiple stage delay line coupled to a multiple tap selection device; a digital filter that includes a plurality of delay blocks and a register, each of the delay blocks having an input coupled to an output of the demodulator circuit and an output coupled to the register; a digital filter that comprises a multiple stage delay line and a vot
Jastrzab Jeffrey R.
Medtronic Inc.
Patton Harold R.
Wolde-Michael Girma
Woods Thomas F.
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