Method for mixing optical and microwave signals using a GaAs MESFET
US5304794A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 25, 1993 |
| Grant date | Apr 19, 1994 |
| Priority date | — |
| Expiry date | May 25, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D7/125
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The present invention utilizes the internal photovoltaic effect of a GaAs SFET to mix an RF modulated optical signal with a microwave signal. As those skilled in the art will readily recognize, a GaAs MESFET generically comprises an n layer of GaAs (channel) deposited on semi-insulating GaAs (substrate). Source, gate and drain electrodes are then formed on the channel with the gate acting as a Schottky barrier. In this standard MESFET, the difference in doping between the channel and substrate produces a potential barrier. It has been found that when the device is illuminated, the potential barrier is reduced in the region between the source and the gate and drain and the gate. This reduced potential barrier allows more drain current to flow from the device. It has been found that this drain current photoresponse is highly non-linear with respect the gate voltage applied to the device and therefore, it may be used to mix RF modulated optical signals with microwave signals. Accordingly, the present invention uses this effect to mix an optical signal directly or indirectly delivered to the MESFET with an RF signal so as to produce an IF signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.