||The thesis treats three main topics. In the first topic, we discuss the design of baluns realized using PCB and IPD processes. In the PCB process, we use an induced-current structure for balun design and wound-coil structure to reduce the area. The total size is 8.1 × 8.6 mm2, and characteristics of balun in ISM band at 2.4 GHz are as follows : The insertion loss, amplitude imbalance and phase difference were less than 1 dB, 0.5 dB and 1°respectively. Besides, the CMRR was greater than 30 dB. In the IPD process, we use the Marchand balun structure for frequency band from 1 GHz to 3 GHz, and its size was about 2.03 × 1.13 mm2. The insertion loss, amplitude imbalance, and phase difference were less than 1.7 dB, 1 dB, and 3°respectively. The CMRR was also greater than 29 dB.|
In the second topic, we studied ground current distributions. At first, we analyzed balanced (Differential) and unbalanced (Single-ended) feeds for a balanced antenna. Besides, we also compared the current distributions for antenna fed by cable line and microstrip line. We found that the balanced antenna with balanced feeding had induced modes corresponding to wavelengths of full integers, and with the unbalanced feeding had modes corresponding to not only integer number but half wavelengths. This finding may help explaining the characteristics of antenna. The another part of the second topic is to suppress the interference created by ground radiation, so that other components in chip-package-board integration would not be affected. We proposed that balun be a circuit to suppress the ground current. Here, the effect of ground currents in a PIFA with balun was investigated. The results show that balun can reduce ground current and make current distribution more uniform, and the peak current value is reduce about 25 % to 50 %. However, this technique may reduce the radiation efficiency of the antenna.
The last topic is simulation of RF front-end transmitter circuit. Active circuit and passive circuits were designed using T18 and IPD processes, respectively. The active circuit is a power amplifier made by a senior from our laboratory, and the passive circuits consist of balun and PIFA. Flip chip interconnections are used to integrate the active device onto the IPD platform. Finally, co-design of the integrated RF front-end was conducted at the frequency band of 5.8GHz.