Direct-digital modulation (DIDIMO) transmitter with −156dBc/Hz Rx-band noise using FIR structure

A direct-digital modulation (DIDIMO) transmitter employing 3-taps 10-bit Finite Impulse Response configuration is proposed and evaluated. FIR-DIDIMO provides simultaneous combination of D/A conversion, up-conversion, power control and also quantization noise filtering at arbitrary offset frequency from the carrier. This makes the circuit suitable for multistandard transmitters by eliminating the area-consuming analog baseband low-pass filter. Moreover it enables optimum RF noise shaping against various modes and bands requirement. The noise shape adjustment scheme is also detailed in this paper. Using a WCDMA signal, the transmitter achieves 81dB of power control range, EVM of less than 3% from -42dBm to +6.0dBm output power for band I operation with 568.32MHz sampling frequency. The RX band (190 MHz offset) noise floor achieves -156.3dBc/Hz measured with 291mW analog power consumption at +6.0dBm output. WCDMA band II and LTE 20M band1 performances are also demonstrated. The chip is designed and implemented with a low-power 0.13um 1.5V/3.3V CMOS process and the transmitter analog area measures 1.3mm².