Design of High-Precision Complex Quadrature Modulators and Demodulators

由于正交调幅（QAM）被应用于无线局域网和蜂窝系统以获得更高的比特率，因此强烈要求误差矢量幅度（EVM）小于1%。我们可以在复信号域中表示具有相位和幅度损伤的本振信号。在正交调制器中，本LO信号的负频率分量是不需要的。因此，使用一个复杂的正交调制器和一个复杂的滤波器，我们可以减少不希望的射频（RF）信号。此外，引入一种新的lo相位误差校正电路，可以得到小于1%的evm。该调制器在1.2 v电源下仅耗散8.2 mW。

Because quadrature amplitude modulation (QAM) is applied to WLANs and cellular systems to obtain higher bit rates, an error vector magnitude (EVM) with less than 1% is strongly demanded. We can express local oscillator (LO) signals with phase and amplitude impairments in the complex signal domain. In a quadrature modulator, the negative-frequency component of the LO signal is an undesired one. Therefore, using a complex quadrature modulator and a complex filter, we can reduce an undesired radio frequency (RF) signal. Moreover, introducing a new LO-phase-error correction circuit, we can get EVMs of less than 1%. This modulator dissipates only 8.2 mW at a 1.2-V-power supply.