Paul E. Bauhahn

A millimeter wave passive FET mixer with low 1/f noise

A millimeter-wave resistive (intermediate frequency) FET mixer design that provides down-conversion to low IF (intermediate frequency) frequencies with low 1/f noise is described. The single FET unbalanced mixer has a double sideband noise figure of 7.5 dB with a conversion loss of 9 dB at an LO (local oscillators) drive level of 9 dBm. An RF to LO isolation of 15 dB is achieved through the use of a resonant loop from drain to gate. The design allows downconversion to low IF frequencies using a FET-compatible process with a small chip size. A comparison of MESFET and HEMT (high electron mobility transistor) versions of the mixer shows that the 1/f noise level is higher in the HEMT mixer.<<ETX>>

Laser link performance improvements with wideband microwave impedance matching

The wideband microwave performance of a laser link was improved using a lossless microwave impedance-matching network. Matching has been achieved from 3 to 9.5 GHz, which is more than one octave with a 5 dB associated improvement in both throughput loss and noise figure for the optical link. The improved noise figure makes it possible to use the laser link with lower-gain amplifiers in front of the laser, and the improved throughput loss reduces the gain needed after the link. It is concluded that impedance matching not only improves the performance but also reduces power consumption in the whole system.

High-density circuit approach for low-cost MMIC circuits

Using spectral domain coupled transmission line calculations and computer programs to generate circuit files for standard circuit analysis programs, a double balanced monolithic mixer with RF/IF overlap has been developed using spiral baluns. This technique can be employed to extend the design of high density MMIC circuits to frequencies greater than 20 GHz.