|dc.description.abstract||The thesis aims to study and implement different topologies of the broadband mixer using GaAs and CMOS processes. Three circuit topologies for the broadband mixer are presented in Chapter 3, 4, and 5, respectively. The conclusion is summarized in Chapter 6.
The fundamental of the mixer and the processes are presented in Chapter 2. Some conventional single-ended mixers with various mechanisms are described in Chapter 3, and the fundamental of the gate-pumped mixer is also outlined. The broadband mixers are achieved using Darlington pair instead of a single transistor. The conversion gain of the mixer is investigated, the effect of the DC bias and the transistor size to conversion efficiency are also addressed. A 20~70 GHz single-ended Darlington mixer is implemented using 0.13 ?m CMOS process, the mixer has a conversion gain of 5.5 dB with a LO power of -1 dBm. In addition, a 25~45 GHz single-ended Darlington mixer is implemented using 0.5 ?m GaAs PHEMT process, the mixer has a conversion gain of 12 dB with a LO power of 2 dBm. The simulation and measurement are demonstrated. Moreover, a distributed mixer is implemented using the Darlington pair. The Darlington pair composes of GaAs HBT and HEMT, and broad bandwidth and high conversion gain can be both achieved using the proposed topology. The simulations of four distributed mixers are presented, and the theoretical conversion gain of the distributed mixer is carefully compared with the experimental results. The characteristic of the transmission lines at the gate and drain are also discussed. A 6~33 GHz distributed mixer with flat conversion gain is implemented using 2 ?m /0.5 ?m GaAs HBT-HEMT process, and the mixer has the advantages of the small chip size and the low LO power.
The Gilbert-cell mixer with inductive peaking is presented in Chapter 5. The fundamental of the Gilbert-cell mixer is introduced, and the transconductance stage and the switch stage are designed using various topologies with the HBT and HEMT to achieve broad bandwidth and good conversion gain. The theoretical calculation for the topologies and the frequency response of the transconductance and switch stages are also presented to verify the proposed design concept. Besides, a feedback IF amplifier is used to extend the 3-dB IF bandwidth of the mixer. Finally, the comparisons with the previously reported results and the conclusion are given in Chapter 6.