US 7,609,187 B2
ΔΣ modulator and ΔΣ analog-digital converter
Koichi Maezawa, Nagoya (Japan); and Takashi Mizutani, Nagoya (Japan)
Assigned to National University Corporation Nagoya University, Nagoya-shi (Japan)
Appl. No. 11/883,886
PCT Filed Feb. 10, 2006, PCT No. PCT/JP2006/302334
§ 371(c)(1), (2), (4) Date Aug. 08, 2007,
PCT Pub. No. WO2006/085605, PCT Pub. Date Aug. 17, 2006.
Claims priority of application No. 2005-035196 (JP), filed on Feb. 10, 2005.
Prior Publication US 2008/0258952 A1, Oct. 23, 2008
Int. Cl. H03M 3/00 (2006.01)
U.S. Cl. 341—143  [341/155] 34 Claims
OG exemplary drawing
 
1. A ΔΣ modulator comprising:
an oscillator changing a frequency thereof according to an analog signal to be converted into a digital signal, wherein the analog signal is input into the oscillator, and the oscillator outputs a frequency modulation signal whose frequency changes according to the voltage of the analog signal;
a reference signal source outputting a reference signal at a predetermined frequency;
a mixer mixing the frequency modulation signal output from the oscillator and the reference signal output from the reference signal source;
a low-pass filter passing a low frequency component of the frequency modulation signal output from the mixer;
a quantizing unit quantizing the frequency modulation signal output from the low-pass filter; and
an operation circuit applying a predetermined operation to a digital signal output from the quantizing unit,
wherein a center oscillation frequency of the oscillator is set higher than a target center oscillation frequency of the frequency modulation signal output from the low-pass filter.