John J. Geddes

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>>

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.

Comparison of MESFET and HEMT MMIC technologies using a compact Kaband voltage-controlled oscillator

To compare the capability of MESFET and HEMT technologies for monolithic microwave integrated circuit (MMIC) implementation we have fabricated and tested discrete field-effect transistors (FETs) and a novel Ka-band monolithic voltage controlled oscillator (VCO). We implemented the circuit with three different active devices: moderate- and high-doped ion-implanted MESFETs (metal-semiconductor FETs) and AlGaAs/GaAs HEMTs (high electron mobility transistors). A comparison of the measured oscillator phase-noise and an independent comparison of the temperature dependence of MESFET and HEMT RF equivalent circuits yields two general guidelines: MESFETs are preferred over HEMTs for applications requiring low phase-noise and temperature insensitive operation.

High Efficiency GaAs MBE Power FETs for Ka-Band

Submicron gate length, 300 micron gate width GaAs FETs were fabricated on MBE material using direct write e-beam lithography. Evaluation of the devices in a Ka-band test fixture with fin line transitions resulted in an amplifier output power of 110 mw with 11 percent power added efficiency at 30 GHz. At 2.9 dB gain the power per unit gate width is .46 W/mm referenced to the device. This is the highest power output per unit gate width reported to date for a GaAs FET at Ka-band.

Low-noise MMIC performance in Kaband using ion implantation technology

The progress made in producing low noise MMICs in Ka-band using an ion-implantation technology is reviewed. The technology is characterized by 3.8 dB noise figure with 14-16 dB gain and is suitable for high volume applications where the cost is to be kept low.

LED Driver And Pin Diode Receiver ICs For Digital Fiber Optic Communications

LED driver and PIN diode receiver ICs have been developed for application in fiber optic communication systems. The LED driver provides a drive current adjustable from 25 to 150 mA in 25 mA incre-ments. The current is stabilized against changes in supply voltage and changes in the LED voltage drop due to temperature variations by an internal regulator. When coupled with a suitable PIN diode, the receiver amplifies signals as small as 250 nanoamps to TTL logic levels. The receiver IC includes automatic gain control circuitry that enables it to operate over a 36 db range of optical input signal. Both ICs operate with a single 5-volt supply. These ICs can be used with state-of-the-art fiber optic components to construct fiber optic communications links operating at data rates greater than 10 Mb/s with Manchester encoded data or 20 Mb/s with NRZ data.