Patent ID: 7043222
Filing Date: 2006-05-09
Classification: H04L

Abstract:
1. A radio transmitter comprising: a frequency shift keying (FSK) coding logic circuit; a first digital-to-analog converter (DAC) coupled to a first output of the coding logic circuit and a second DAC coupled to a second output of the coding logic circuit; a first filter coupled to the first DAC and a second filter coupled to the second DAC; a first mixer coupled to the first filter and a second mixer coupled to the second filter; and a summing device that combines an output of the first mixer and an output of the second mixer, providing a modulated output signal; wherein the coding logic circuit is operable to receive digital input data at a rate determined by an operating signal frequency; wherein the coding logic circuit is further operable to generate a digitally encoded first periodic signal based on the digital data input and to provide the digitally encoded first signal to the first DAC; wherein the coding logic circuit is further operable to generate a digitally encoded second periodic signal and to provide the digitally encoded second signal to the second DAC when amplitude of the digital input data corresponds to a first level; wherein the coding logic is further operable to generate a digitally encoded third periodic signal and to provide the digitally encoded third signal to the second DAC when amplitude of the digital input data corresponds to a second level; wherein the first mixer is operable to receive a fourth signal substantially shaped like the second signal, and to multiply the fourth signal with data signal received by the first mixer from the first filter; wherein the second mixer is operable to receive a fifth signal substantially shaped like the first signal, and to multiply the fifth signal with data signal received by the second mixer from the second filter; wherein the first signal is substantially equal to the second signal shifted by a determined phase angle; and wherein each DAC is configured to generate a non-linear output.