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Abstract

An apparatus for modulating a digital input signal having a pre-assigned symbol rate and having a baseband carrier frequency by using a single sample clock signal. The pre-assigned symbol rate is selected from the group consisting of a plurality of symbol rates. The apparatus in a baseband mode comprises: (a) an Interpolate_by_2_Nyquist Filter block configured to double the pre-assigned symbol rate, to perform Nyquist filtering operation, and configured to output an Inphase (I) and a Quadrature (Q) components of the pre-assigned signal having the double symbol rate; (b) a Complex Shaper block configured to pre-compensate the spectrum of I and Q components of the signal having the double symbol rate in advance for a spectrum distortion caused by the apparatus; .COPYRGT.) a Cascaded Integrated Comb (CIC) Interpolator filter configured to increase by an interpolation R factor the sample rate of the signal as compared with a sample rate of the baseband carrier; (d) a Phase Shifter configured to compensate a phase of interpolated by R signal for a known quadrature error; (e) an Inphase (I) channel and Quadrature (Q) channel Gain blocks configured to pre-compensate the I and Q components of the interpolated by R signal for a known gain difference circuit between the I and Q channel gains; (f) an I and Q channel DC offset blocks configured to pre-compensate I and Q components of the interpolated by R signal for a known DC offset difference circuit between I and Q channel DC offset blocks; and (g) a Controller block configured to supply a plurality of control signals to the apparatus. In the passband mode, I and Q channel Gains are set to one, and I and Q channel DC offsets are set to zero.

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First Claim