 Heated automobile mirror |
| We claim: 1. A defogging mirror unit comprises a plate of thermally and electrically conductive ... |
|
| Method and apparatus for automatically adjusting noise immunity of an integrated circuit |
| In accordance with a preferred embodiment of the present invention, a noise-immune integrated ... |
|
| Voltage generating apparatus |
| OF PREFERRED EMBODIMENTS Before describing the specific embodiments of the invention, the ... |
|
| Reference voltage distribution for multiload i/o systems |
| According to an embodiment of the invention a circuit that is to be coupled to a reference voltage ... |
|
| Input stage apparatus and method having a variable reference voltage |
| The present invention is directed to an input stage and method having increased input signal noise ... |
|
| Method for digitally measuring electrical impedance |
| The instant invention is distinguished over the known prior art in a multiplicity of ways. For one ... |
|
| System for measuring and recording a utility consumption |
| It is an object of the invention to provide an improved system for measuring and recording a ... |
|
| Baseband data switching apparatus for digital communications system |
| An object of the present invention is to provide a baseband switching apparatus which facilitates ... |
|
| Method of synchronizing two binary trains |
| To this end, the invention provides a method of synchronizing two binary trains in order to switch ... |
|
|
Method and apparatus for suppressing tones induced by cyclic dynamic element matching (DEM) algorithms
| Details |
Inventors: Ruha, Antti; Ruotsalainen, Tarmo; Tervaluoto, Jussi-Pekka; Kauppinen, Jani;
Assignee: Nokia Corporation (Espoo, FI)
Primary Examiner: Wamsley; Patrick
Assistant Examiner:
Attorney, Agent or Firm: Harrington & Smith, LLP
Disclosed is a method and apparatus for performing Dynamic Element Matching (DEM). The method operates to input a plurality of digital values and, for each value, to generate a plurality of N signals individual ones of which are intended to drive one of a plurality of N elements. The plurality of signals are generated so as to average the usage of individual ones of the N elements over time. The method further periodically rearranges the plurality of N signals so as to suppress the generation of undesired periodicities or tones in the usage of the N elements, and without affecting the averaging of the usage of the N elements. Preferably the periodic rearrangement occurs only at a time when the usage of the N elements is indicated as being averaged using, for example, an enable signal that is input to a secondary DEM block from a primary DEM block. The plurality of N signals are preferably generated by the primary DEM block using a cyclic DEM algorithm, such as a Data Weighted Averaging (DWA) algorithm or a rotation-based Clocked Averaging (CLA) algorithm, and the periodic rearrangement performed by the secondary DEM block is preferably based on randomization or pseudo-randomization. |
|
DETAILED DESCRIPTION The foregoing and other problems are overcome by methods and apparatus in accordance with embodiments of these teachings.
These teachings provide a technique to suppress or cancel the generation of tones for cyclic DEM algorithms, such as the DWA and CLA algorithms.
The circuitry can be implemented entirely in the digital domain, thereby making the incorporation of these teachings into integrated circuit applications particularly straightforward.
These teachings also do not require an increase in the number of analog circuit components, thereby conserving integrated circuit area and power consumption.
The preferred method and apparatus is based on a two step or two stage DEM algorithm.
The primary DEM algorithm is preferably a cyclic algorithm that converts the mismatch distortion to wide-band noise and tones, while the secondary DEM algorithm converts the tones to wide-band noise.
The secondary DEM algorithm does not decompose the averaging performed by the primary DEM algorithm, and thus the noise shaping of the primary DEM algorithm is preserved.
In the preferred embodiment a connection between the primary DEM algorithm processor block and the unit elements is randomized within a switching matrix of the secondary DEM algorithm.
The operation of the secondary DEM algorithm is synchronized to the operation the primary DEM algorithm, and thus the random switching applied by the secondary DEM algorithm does not decompose the averaging of the primary DEM algorithm.
In this manner the noise shaping and the long term averaging applied by the primary DEM algorithm is preserved, and the white noise floor near DC does not occur.
These are important considerations in maintaining the performance of the DWA algorithm.
The operation of the improved DEM technique in accordance with these teachings converts the unwanted tones to noise-shaped wide-band noise, and does not simply shift the unwanted tones to frequencies outside of the signal band of interest.
As a result, the out-of-band noise is not demodulated into the signal band of interest due to the high frequency tones produced by the DEM algorithm
|
|
Coded 
