Design And Research Of Direct Quadrature Modulator With Injection-locked Frequency Divider In Low-Noise LTE Transmitter

LTE (Long Term Evolution) is the 3G evolution of the project, which improves and enhances air access of 3G technologies. It provides downlink 100Mbit/s and uplink 50Mbit/s peak rate in 20MHz spectrum bandwidth,improves the performance of users at cell edge, expands capacity and reduces system latency.Direct-conversion transmitter is for a variety of modulation techniques, such as GSM, WCDMA and LTE. The simplicity of structure is suitable for broadband applications. The quadrature modulator, as a core of transmitter, includes the local oscillator (LO) signal generator, mixer and driver amplifier.ILFD can be used as a quadrature signal generator, and its outstanding feature is low power consumption.A 2500MHz low-noise direct quadrature modulator with injection-locked frequency divider for LTE system is presented, which includes passive mixer, 25%-duty-cycle LO generator and a driver amplifier. The whole circuit is implemented in TSMC 65nm 1p6m CMOS process. The modulator provides output power 2.5dBm, an ACPR of -46dBc at 5MHz offset, -60dBc at 10MHz offset and output noise of -163dBc/Hz at 40MHz offset. The whole circuit consumes 51mW from 1.2V and 2.5V supply voltage.