This paper describes millimeter-wave HEMT oscillators developed to operate at 50 GHz and above. To determine the feasibility of using HEMTs for millimeter-wave oscillators, we measured and compared the low-frequency noise characteristics of both HEMT and GaAs MESFET devices and found them to have nearly identical characteristics. We also estimated the S parameters of a HEMT biased at Vds-3V and Ids5 mA for an equivalent circuit study. The oscillators consisted of a microstrip line resonator, a matching circuit, and a bias circuit. The output power and oscillation efficiency for the 60-GHz HEMT oscillator was 2.6dBm and 9.5%, and 2.8dBm and 6.4% for the 50-GHz oscillator. The efficiencies of these HEMT oscillators are higher than that of GaAs MESFET oscillators at millimeter-wave frequencies.

This paper describes the design of a 38-GHz high power MMIC amplifier using an improved load-pull technique. We improved the load-pull technique accuracy by using MMIC transtormers to match the input and output impedances of a GaAs MESFET to about 50 ohms. We used this technique to measure the large-signal load impedance of a FET with a 600-µm-wide gate. Using the data obtained, we developed an MMIC amplifier composed of two of these FET cells. At 38 GHz, the amplifier has an output power of 23.5 dBm for a 1 dB gain compression level.

We studied a 0.15-µm InGaP/InGaAs/GaAs pseudomorphic HEMT operating under a negative drain bias, using a parameter extraction technique based on an analytical parameter transformation. The bias-dependent data of smallsignal equivalent circuit elements was obtained from Sparameters measured at up to 62.5 GHz at various bias settings. We then described the intrinsic part of the device using a new empirical large-signal model in which charge conservation and dispersion effects were taken into consideration. As far as we know, this is the first report to clarify the behavior of a HEMT operating under negative drain bias. We included our largesignal model in a commercially-available harmonic-balance simulator as a user-defined model, and designed a 60 GHz MMIC oscillator. The fabricated oscillator's characteristics agreed well with the design calculations.

An important aspect of traffic safety is the development of aids that extend the driver's time and motion perception. One promising candidate is the compact, lightweight millimeter-wave FM-CW radar now being widely studied. Although the homodyne FM-CW radar is well known form its simplicity, it has a relatively low S/N ratio. This paper describes the principles behind our newly-developed heterodyne FM-CW radar and it's evaluation results. The heterodyne FM-CE radar generates sidebands by switching a front-end amplifier and also uses the heterodyne detection technique for gaining sensor sensitivity. The heterodyne FM-CW radar's signal to noise ratio was 19.5 dB better than previously designed homodyne FM-CW radar.