N-PATH FILTER USING DIGITAL FILTER AS TIME INVARIANT PART

• US 3,629,509 A
• Filed: 05/01/1969
• Issued: 12/21/1971
• Est. Priority Date: 05/01/1969
• Status: Expired due to Term

• Current Assignee: Arthur B. Glaser
• Original Assignee: Arthur B. Glaser
• Inventors: Glaser, Arthur B.
• Application Number:
  US04/820,813
• Time in Patent Office: 964 Days
• US Class Current: 370/535
• CPC Class Codes: H03H 19/002 N-path filters

Abstract

A time division multiplexed digital filter is used as the timeinvariant part of an N-path filter. The use of a multiplexed digital filter alleviates the problem of closely matching the transmission characteristics of each of the N-paths.

Claims

1. A time-varying network comprising:

means for selectively modulating an applied input signal with a plurality of predetermined modulating signals, means for developing multiplexed sample pulses of said modulated signals, digital filter means for processing said multiplexed sample pulses, means for demultiplexing pulses processed by said digital filter, and means for selectively demodulating said demultiplexed pulses.

2. An N-path filter comprising:

means for simultaneously modulating an applied input signal with a plurality of predetermined modulating sIgnals and time multiplexing said plurality of modulated signals, means for developing sample pulses of said modulated multiplexed signals, digital filter means for processing said sample pulses, means for demultiplexing pulses processed by said digital filter, and means for demodulating said demultiplexed pulses.

3. The N-path filter defined in claim 2 wherein said means for simultaneously modulating and time multiplexing comprises:

operational amplifier means shunted by resistor means, a first circuit path responsive to said input signal comprising a first plurality of resistor means connected to one terminal of said operational amplifier means, a second circuit path responsive to said input signal comprising a second plurality of resistor means connected to another terminal of said operational amplifier means, and means for selectively altering the transmission characteristics of said first and second circuit paths.

4. An N-path filter comprising:

means for simultaneously modulating an applied input signal with a plurality of predetermined modulating waves, means for developing sample pulses of said modulated signals, means for time multiplexing said sample pulses, means for encoding said multiplexed sample pulses,

5. An N-path filter comprising:

means for simultaneously selectively modulating an applied input signal with plurality of predetermined modulating signals, multiplexing said plurality of modulated signals, and sampling said plurality of multiplexed signals, means for encoding said modulated multiplexed sample signal, digital filter means for processing said encoded signal, means for demultiplexing signals processed by said digital filter, means for decoding said demultiplexed signals, and means for demodulating said decoded signals.

6. The N-path filter defined in claim 5 wherein said means for simultaneously selectively modulating, multiplexing and sampling comprises:

operation amplifier means shunted by resistor means, a first circuit path responsive to said input signal comprising a first plurality of resistor means connected to one terminal of said operational amplifier means, a second circuit path responsive to said input signal comprising a second plurality of resistor means connected to another terminal of said operational amplifier means, means for selectively altering the gain of said amplifier in a stepwise manner, and means for sampling signals appearing at the output of said operational amplifier means.

7. An N-path filter comprising:

means for simultaneously selectively modulating an applied input signal with a plurality of predetermined modulating signals, multiplexing said plurality of modulated signals, and sampling said plurality of multiplexed signals, digital filter means for processing said modulated, multiplexed, and sampled signal, means for demultiplexing signals processed by said digital filter, and means for demodulating said demultiplexed signals.

8. The N-path filter defined in claim 7 wherein said means for simultaneously selectively modulating, multiplexing and sampling comprises:

operational amplifier means shunted by resistor means, a first circuit path responsive to said input signal comprising a first plurality of resistor means connected to one terminal of said operational amplifier means, a second circuit path responsive to said input signal comprising a second plurality of resistor means connected to another terminal of said operational amplifier means, means for selectively altering the gain of said amplifier in a stepwise manner, and means for sampling signals appearing at the output of said operational amplifier means.