×

Digital modulator having a digital filter including low-speed circuit components

  • US 5,926,065 A
  • Filed: 10/08/1997
  • Issued: 07/20/1999
  • Est. Priority Date: 10/11/1996
  • Status: Expired due to Fees
First Claim
Patent Images

1. A digital demodulator comprising:

  • a converter for converting an analog input signal into a digital signal, said converter operating so as to satisfy
    
    
    space="preserve" listing-type="equation">f.sub.s =4·

    f.sub.IF /(2n+1), wherein fIF indicates an intermediate carrier frequency, fs is a sampling frequency and n indicates a positive integer;

    a signal processing section for quadrature demodulating said digital signal output from said converter by mixing with quadrature local oscillation signals, a frequency fc'"'"', of said quadrature local oscillation signal is
    
    
    space="preserve" listing-type="equation">f.sub.c'"'"' =f.sub.s /4, wherein said signal processing section extracts a first and a second digital signal being orthogonal in phase to each other, and said first and second digital signals being alternately inverted in polarities with said sampling frequency;

    at least one digital filter section coupled with said signal processing section for sampling said first and second digital signals, said digital filter section comprising;

    first switching means, andsecond switching means,said first switching means conducting a change-over operation between said digital signals and a signal at binary zero with a frequency m·

    fs, and said second switching means receiving the signals from said first switching means and intermittently outputting therefrom signals at a period corresponding to a frequency m·

    fs /M, wherein m and M are positive integers and M>

    m; and

    at least one filter arithmetic section coupled with said digital filter section, for producing demodulated signals.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×