| Summary: | 碩士 === 國立交通大學 === 電信工程系所 === 92 === This thesis is divided into two parts. The first part describes the analysis and design of a Ka-Band power amplifier applied to the automotive collision avoidance radar system. In order to acquire the adequate linearity and efficiency of the system requirements, the architecture with two stages is adopted to design the power amplifier. The first stage utilizes class-A type to supply sufficient power gain. The second stage improves RF-to-DC signal ratio by class-AB type. By this way, the linearity of this circuit can also be improved. The semiconductor material of PHEMT is adequate to design the RF circuits with the characteristics of high power level and high operating frequency because it possesses the higher breakdown voltage and the lower doping channel. So as to operate the circuits at Ka-band, we select the semiconductor process of WIN 0.15-um GaAs PHEMT to design the circuits. At the central frequency of 32.4GHz, the measured results reveal that the fabricated power amplifier has the P-1dB of 2dBm、Pout of 12.4dBm, and PAE of 19.7% at P-1dB point.
The second section of this thesis proposes and demonstrates a novel architecture of 2.4GHz bi-directional amplifier. The approach improves effectively the isolation and noise figure of the circuit to ameliorate the quality of output signal. The framework includes two reflection-type amplifiers and a 90 degree branch-line circuit. The designed process must pay attention to the oscillation condition because its principles are similar to that of an oscillator. Meanwhile, the ability of bi-direction could be realized in accordance with the characteristic of branch-line circuit. The bi-directional amplifier with this architecture can obtain the gain which is same as that of a reflection-type amplifier. Also, a variable capacitance is arranged to steady the condition of oscillation and adjust the gain according to the circuit’s requires. And the conventional branch-line circuit must be realized by means of transmission lines with the quarter wavelength. This length is 16.7mm at the operating frequency of 2.4GHz. This approach is inappropriate for CMOS IC. Therefore, this 90 degree branch-line circuit is realized on a FR4 board and utilizes a new method to reduce the area. So, this IC only embraces these two critical reflection-type amplifiers. And the expected specifications of this reflection-type amplifier are as follows: power gain 13.6dBm, P1dB -5dBm，the noise figure 14.3dB. Furthermore, the return loss S11 of this bi-directional amplifier is below -10dB across overall utilized bandwidth. The gain can alter from 7.5dB to 16dB and the noise figure varies from 4.1 to 5.4.
|
|---|
