Research On Multimode Transmitter Chips For 2G/3G Mobile Communication

Nowadays, mobile communications are characterized as multi-mode, multi-band and multi-rate, as a result, single user equipment (UE) can be no longer available for this trend. The UE which can support multimode applications becomes a hot topic recently both in companies and universities. The key of this UE is the transceiver that can deal with multi-mode signals. This dissertation focuses on the design of multi-mode transmitter for 2G/3G communications, espically for GSM, TD-SCDMA and WCDMA system.Firstly, the frequency bands allocations, channel definations and work modes of 2G/3G system are summarized, the digital modulation schemes for 2G/3G system is analyzed in detail.Secondly, the architectures of transmitter are discussed, among which, direct conversion transmitter (DCT) is adopted for our multi-mode transmitter solution. A system model based on DCT is proposed with the help of ADS to verify the key parameters of the transmitter chain and this way of analysis is helpful for both system design and circuit optimization.Thirdly, the design of CMOS linear power amplifier (PA) is presented which is a great challenge to a transmitter. With some explorations for non-linearity sources and analysis on output matching networks that can boost the output power of a power amplifier and reject the output harmonics, a two-stage high efficienct CMOS PA is realized in a 0.18?m CMOS technology with a 1.8V supply.Fourthly, the research on carrier leakage for DCT is also given. The reasons for carrier leakage is mathematically analyzed which reflects the sources of carrier leakage including even distortion from analog baseband. Based on the present algorithm for carrier leakage calibration, a new method with two-point estimation for carrier leakage calibration is presented and verified, as a result, a 31dB improvement is achieved. Meanwhile, a wideband power detector (PD) with high dynamic range for carrier leakage calibration is presented with a preceding LNA after noise analysis.Finally, a multi-mode, multi-band transmitter chip for GSM and TD-SCDMA (or WCDMA) applications is realized in SMIC 0.13?m CMOS 1P8M mixed-signal process. The methods for noise and linearity optimization are emphasized for the building blocks of transmitter. The work includes the noise analysis for LPF, proposal of a low noise, high linear analog variable gain amplifier and the realization of a modulator with resistive feedback. According to the measurements, the designed multi-mode transmitter can provide a high dynamic power control range of 78dB, the noise floor can also meets SAW-less requirements for TD-SCDMA and WCDMA systems. The experimental results show that the designed multi-mode transmitter can meet the requirements of design specifications in ACLR, EVM, power control range, output noise and so on for 2G/3G mobile communication applications.