dc.description.abstract | Several microwave and millimeter broadband mixers using Darlington cell are presented in this thesis for the receiver in wireless communication. Based on the broadband Darlington cell, three circuit topologies, including a broadband single-ended mixer, a broadband distributed mixer, and a broadband double-balanced mixer are proposed. A self-oscillation mixer (SOM) using a hybrid cascode topology is also proposed.
The broadband single-ended mixer is realized in 0.25 m GaAs enhancement/depletion-mode (E/D-mode) pseudomorphic high-electron mobility transistor (pHEMT) process. To achieve low local oscillation (LO) driving power, a Darlington cell and a directional coupler are adopted. The proposed mixer features with 3-dB bandwidth from 10 to 40 GHz, a low LO driving power of -5 dBm, a maximum conversion gain of 13.2 dB. The proposed mixer features with low LO driving power and conversion gain as compared to the bulk-driven mixer.
The broadband distributed mixer using Darlington cell is implemented using a 0.18 m SiGe BiCMOS technology. To extend the operation bandwidth, a uniform distributed topology is utilized for wideband matching. The LO driving power is further reduced as compared to the distributed drain mixer. The proposed mixer consists of a Darlington cell and a two-section Wilkinson power combiner. This mixer exhibits a broad RF bandwidth from 2 to 67 GHz, a low LO driving power of 0 dBm, a maximum conversion gain of 5 dB, and a small chip size of 0.41 mm2.
The broadband double-balanced mixer employed Darlington cell is implemented using a 0.18 m SiGe BiCMOS process. A compact Marchand balun and a Wilkinson power divider are used to generate the differential RF and LO signals for the gate-pumped mixer. Meanwhile, the high port-to-port isolations are achieved. The proposed double-balanced mixer achieves a broad RF bandwidth from 30 to 67 GHz, a low LO driving power of 2 dBm, and a conversion gain of -5 dB. Morever, the spurious suppression is better than -40 dBc due to the double-balanced topology.
The self-oscillation mixer using a GaAs 2 μm heterojunction bipolar transistor (HBT) and 0.5 μm high electron mobility transistor (HEMT) process. The HBT-HEMT cascode mixer is similar to a dual-gate mixer. The voltage-controlled oscillator (VCO) and the transconductance stage are investigated using four transistor combinations to enhance the conversion gain, bandwidth and phase noise. Among four configurations, the HBT-HEMT cascode mixer exhibits the best gain-bandwidth product, the widest bandwidth and the lower phase noise. The measured tuning range of VCO is from 19.51 to 21.17 GHz. The measured phase noise at 1-MHz offset is -123 dBc/Hz at 20.34 GHz. The measured conversion loss is 16 dB with an input 1-dB compression point of -7 dBm, as the self-oscillation mixer is performed as an up converter.
Finally, the conclusions and future works are addressed in Chapter 7.
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