# US 5,708,433 A · Digital converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,708,433 A - Document ID: US5708433A - Status: Granted - Kind: A - Application number: 08/600,989 - Filed: 1996-03-01 - Granted: 1998-01-13 - Earliest claimed: 1993-09-02 - Inventors: Peter Graham Craven - Web page: https://patentgrep.com/patent/US5708433A ## CPC - H03M 1/822: {using pulse width modulation} - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) ## Abstract A digital converter includes a consecutive edge modulator and a noise-shaping circuit. The noise-shaping circuit modifies the input to the consecutive edge modulator in dependence upon values corresponding to the output of the consecutive edge modulator. The noise-shaping circuits apply different respective non-linear functions to samples corresponding to the trailing-edge and leading-edge outputs respectively of the consecutive edge modulator. The noise-shaping circuit may act upon an output simulating the output of the consecutive edge modulator for a given input sample value. A look-up table may be used to simulate the consecutive edge modulator output ## Claims ### Claim 1 A digital converter including a consecutive edge modulator (50'), and a noise-shaping circuit (30) arranged to modify the input to the consecutive edge modulator in dependence upon values corresponding to an output of the consecutive edge modulator, characterised in that the noise-shaping circuit (30) is arranged to apply different respective non-linear functions to samples at time instants corresponding to trailing-edge and leading-edge outputs respectively of the consecutive edge modulator. ### Claim 2 A digital converter including a consecutive edge modulator (50), and a noise-shaping circuit (30) arranged to modify the input to the consecutive edge modulator in dependence upon values corresponding to an output of the consecutive edge modulator, characterised in that the noise-shaping applied to the input of the consecutive edge modulator is effective at an oversampling frequency equal to twice the switching frequency of the output of the consecutive edge modulator and in that the level of noise-reduction within the baseband effected by the noise-shaping circuit is substantially independent of the signal modulation level. ### Claim 3 (depends on 1) A converter according to claim 1, including a quantiser (40), the output of the quantiser being connected to the consecutive edge modulator (50) and in which the noise-shaping circuit is connected in a feedback-loop around the quantiser and modifies the input to the quantiser. ### Claim 4 (depends on 1) A digital converter according to claim 1, in which the noise-shaping circuit (30) includes a simulator circuit (80) arranged to generate an output dependent upon the non-linear response of the converter including the consecutive edge modulator to a sample. ### Claim 5 (depends on 4) A digital converter according to claim 4, in which the simulator circuit includes a look-up table (82a-e) programmed with data modelling the said non-linear response. ### Claim 6 (depends on 5) A digital converter according to claim 5, in which the look-up table (82a-e) is addressed by the output of a quantiser (40). ### Claim 7 (depends on 1) A converter according to claim 1, in which the noise-shaping circuit (80) is arranged to generate a correction for a current input to the consecutive edge modulator dependent at least in part upon a preceding output of the consecutive edge modulator. ### Claim 8 (depends on 7) A converter according to claim 7, in which the noise-shaping circuit (80) is arranged to generate a correction for a current input to the consecutive edge modulator dependent also a least in part upon a calculated value substantially corresponding to a current output of the consecutive edge modulator. ### Claim 9 (depends on 8) A converter according to claim 8, in which the noise-shaping circuit (80) includes a delay stage and is arranged to generate a correction for a current input to the consecutive edge modulator dependent also at least in part upon a calculated value substantially corresponding to a succeeding output of the consecutive edge modulator. ### Claim 10 (depends on 1) A converter according to claim 1, in which the noise-shaping circuit includes a non-linear processor and means for conditionally negating one or more inputs and/or outputs to/from the non-linear processor, the non-linear processor and means for conditionally negating in combination thereby applying different respective non-linear functions to samples at time instants corresponding respectively to trailing-edge and leading-edge outputs of the consecutive edge modulator. ### Claim 11 (depends on 1) A digital power amplifier including a digital converter according to claim 1. ### Claim 12 A method of operating a digital converter including a consecutive edge modulator, the method including applying noise-shaping to the input to the consecutive edge modulator, characterised by applying different respective non-linear functions to samples at time instants corresponding to trailing edge and leading edge outputs respectively of the consecutive edge modulator. ### Claim 13 A method of operating a digital converter including a consecutive edge modulator, the method including applying noise-shaping to the input to the consecutive edge modulator, characterised in that the noise shaping is effective at an oversampling frequency equal to twice the switching frequency of the output of the consecutive edge modulator and in that the level of noise-reduction within the baseband effected by the noise-shaping circuit is substantially independent of the signal modulation level. ### Claim 14 (depends on 12) A method according to claim 12, in which the step of applying noise shaping includes applying a non-linear function to a current input to the consecutive edge modulator dependent at least in part upon a preceding output of the consecutive edge modulator. ### Claim 15 (depends on 14) A method according to claim 14 in which the step of applying noise shaping includes applying a non-linear function to a current input to the consecutive edge modulator dependent at least in part also upon a calculated value substantially corresponding to a current output of the consecutive edge modulator. ### Claim 16 (depends on 15) A method according to claim 15 in which the step of applying noise shaping includes applying a non-linear function to a current input to the consecutive edge modulator dependent at least in part also upon a calculated value substantially corresponding to a succeeding output of the consecutive edge modulator. ### Claim 17 A digital converter including an input for a signal to be converted; means for generating a quantised signal from the said signal to be converted; a consecutive edge modulator connected to the said means for generating; and a noise shaping circuit connected in the input path to said consecutive edge modulator; wherein said noise shaping circuit includes means for applying different respective functions to input samples corresponding to trailing edge and leading edge outputs of said consecutive edge modulator. ### Claim 18 (depends on 17) The digital converter of claim 17, wherein at least one of said different respective functions is a non-linear function. ### Claim 19 (depends on 2) A converter according to claim 2, including a quantiser (40), the output of the quantiser being connected to the consecutive edge modulator (50) and in which the noise-shaping circuit is connected in a feedback-loop around the quantiser and modifies the input to the quantiser. ### Claim 20 (depends on 2) A digital converter according to claim 2, in which the noise-shaping circuit (30) includes a simulator circuit (80) arranged to generate an output dependent upon the non-linear response of the converter including the consecutive edge modulator to a sample. ### Claim 21 (depends on 2) A converter according to claim 2, in which the noise-shaping circuit (80) is arranged to generate a correction for a current input to the consecutive edge modulator dependent at least in part upon a preceding output of the consecutive edge modulator. ### Claim 22 (depends on 2) A converter according to claim 2, in which the noise-shaping circuit includes a non-linear processor and means for conditionally negating one or more inputs and/or outputs to/from the non-linear processor, the non-linear processor and means for conditionally negating in combination thereby applying different respective non-linear functions to samples at time instants corresponding respectively to trailing-edge and leading-edge outputs of the consecutive edge modulator. ### Claim 23 (depends on 2) A digital power amplifier including a digital converter according to claim 2. ### Claim 24 (depends on 13) A method according to claim 13, in which the step of applying noise shaping includes applying a non-linear function to a current input to the consecutive edge modulator dependent at least in part upon a preceding output of the consecutive edge modulator. ### Claim 25 (depends on 24) A method according to claim 24 in which the step of applying noise shaping includes applying a non-linear function to a current input to the consecutive edge modulator dependent at least in part also upon a calculated value substantially corresponding to a current output of the consecutive edge modulator. ### Claim 26 (depends on 24) A method according to claim 24 in which the step of applying noise shaping includes applying a non-linear function to a current input to the consecutive edge modulator dependent at least in part also upon a calculated value substantially corresponding to a succeeding output of the consecutive edge modulator.