Current Research
Wireless Systems and RFIC Design

1. RFIC Subharmonic Double-Balanced Mixers for Direct Conversion Receivers

We are currently developing a subharmonic double-balanced mixer using SiGe and BiCMOS RFIC technologies. The mixer will be essential to direct conversion receivers since it does not suffer from the LO self-mixing effect. Also, the double-balanced design ensures that no RF and LO leakage occur at the IF port. The mixer also employs very small inductors, and therefore, does not occupy space on the wafer. The simulated performance at 1.9 GHz RF, 900 MHz LO and 100 MHz IF is listed below. The chip is currently being tested and the results will be posted soon. Please contact rebeiz@umich.edu for more details.

2. Injection Locked Oscillators

It is possible to build low noise RFIC oscillators using injection locking techniques. The oscillator must be designed to be of medium Q so as to allow some tuning in the injection locking mechanism. The injection locked oscillator may be an ideal candidate for low-cost designs at 2.4 GHz. We are building such oscillators in BiCMOS technology using the Conexant process.

3. Coupled Oscillators

It is possible to reduce the noise of oscillators using two coupled oscillators, which are injection locked or self-locked to each other. We are exploring these designs so as to produce low noise oscillators. The theory indicates that the noise will reduce as the number of oscillators, and we are currently using two oscillators to check this idea. More will be presented on this idea in the coming months. This work is done with Conexant.