# US 7,613,253 B2 · Noise balanced QAM detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,613,253 B2 - Document ID: US7613253B2 - Status: Granted - Kind: B2 - Application number: 10/519,609 - Filed: 2002-07-03 - Published: 2006-04-20 - Granted: 2009-11-03 - Earliest claimed: 2002-07-03 - Assignees: Telefonaktiebolaget L M Ericsson (publ) - Inventors: Dan Rutger Weinholt - Web page: https://patentgrep.com/patent/US7613253B2 ## CPC - H04L 27/3827: {in which the carrier is recovered using only the demodulated baseband signals} - H04L 25/061: {providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of DC offset (removal of DC offset in coupling arrangements H04L25/029, H04L25/0296)} - H04L 27/38: Demodulator circuits; Receiver circuits - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method of demodulating digital data using M'ary QAM has been disclosed, comprising the steps of detecting a complex symbol vector D, establishing within which reference symbol boundaries the detected symbol vector D falls, the given reference symbol boundaries being associated with a complex reference vector R. Quadrature components (E_I and E_Q) of an error vector (E) constituting the difference between the detected vector D and the associated reference vector R are found and an error control signal (E′) as feed back signal in the demodulation stage is approximated. The influence of thermal noise in the receiver stage has been limited by a weighting and/or by noise balancing. ## Claims ### Claim 1 In a radio receiver in a communication system, a method of demodulating digital data, using M'ary QAM, comprising the steps of detecting a complex symbol vector D, establishing within which reference symbol boundaries the detected complex symbol vector D falls, the given reference symbol boundaries being associated with a complex reference vector, establishing quadrature components, which comprise a real quadrature component and an imaginary component, of an error vector, constituting a difference between the detected complex symbol vector D and the associated complex reference vector, and seeking to approximate an error control signal as a feedback signal in a demodulation stage, whereby when the detected complex symbol vector D falls within a first sector in a complex plane surrounding an imaginary axis (Q), the first sector being delimited by at least two lines crossing origin, the first sector being symmetrical with regard to the imaginary axis, approximating the error control signal by the imaginary quadrature component of the error vector, whereby when the detected complex symbol vector D falls within a second sector in the complex plane surrounding a real axis (I), the second sector being delimited by at least two lines crossing origin, the second sector being symmetrical with regard to the real axis, approximating the error control signal by the real quadrature component of the error vector; and when the detected complex symbol vector D belongs neither to the first sector nor to the second sector, approximating the error control signal by the mean value of the real quadrature component and the imaginary quadrature component. ### Claim 2 (depends on 1) The method according to claim 1, whereby the first sector is delimited by an area ID_QI>ID_II and the second sector is delimited by an area ID_QI2*ID_II, the second sector is delimited by an area ID_QI<½*ID_II. ### Claim 4 (depends on 1) The method according to claim 1, further comprising the steps of using a weighted error signal, the error signal being a function of the error control signal as the feed-back signal in the demodulation stage, whereby the weighted error signal approaches zero for the error control signal approaching zero, attains a positive value for positive values of the error control signal close to zero and attains a negative value for negative values close to zero, approaches zero when the error signal vector approaches the symbol boundaries of the detected symbol. ### Claim 5 (depends on 4) The method according to claim 4, wherein when the error signal vector exceeds the symbol boundaries, the weighted error signal attains a reduced value or a zero value. ### Claim 6 (depends on 5) The method according to claim 5, wherein the error control signal is reduced according to WE = E ′ ( 1 - 2 ⁢ W T ) where E′ corresponds to the deviated control error and T corresponds to the symbol boundary size and where W=Max{abs(E_I); abs(E_Q)}. ### Claim 7 (depends on 4) The method according to claim 4, wherein no weighting is performed for outer corner portions of the M'ary QAM constellation. ### Claim 8 (depends on 7) The method according to claim 7, wherein when the detected signal falls outside the symbol boundaries along the Q and I axes, the weighting function WE=0 is applied.