High Order Harmonic Oscillators in Microwave and Millimeter-wave ...

1 Introduction
1.1 Background
Wireless communication services have been rapidly expanding year after year. The
requirement of the high speed data transmission in the wireless communication systems
has been increasing every year. A millimeter-wave wireless LAN in 60 GHz band, a
collision avoidance car radar in 77-GHz and 24-GHz bands, and Terahertz wave detectors
and imaging technology in biomedical field are promising applications of the wireless
technology [1], [2].
An oscillator is the most important component in the microwave and millimeter-wave
systems because the characteristic of the oscillator mainly decides the system quality.
However, microwave and millimeter-wave oscillators have still some practical problems
such as the output power, phase noise, stability and cost. Performances of the high frequency
oscillator are restricted because of the performance of the semiconductor devices.
Some approaches for these issues have been demonstrated. Semiconductor device technologies
have been developed. 90 nm CMOS and SiGe HBT achieves high frequency
performances as well as GaAs transistors. InP device consisting the advantages of high
electron density and high electron mobility achieves 350 GHz operation [3]. GaN is progressing
for the high power device utilizing its wide band gap [4].
Some circuit configurations to obtain high frequency signal have been developed as well
[5]. Harmonic oscillator, frequency doubler, frequency multiplier, sub-harmonic mixer,
Phased Locked Loop (PLL) oscillator, and injection locking are the up converting methods.
Down converting the optical power spectrum using mixer and filters is also one of
the signal generation method. In this dissertation, we call these high frequency signal
generation method “conventional oscillator”.
1