FIRST (Far InfraRed and Submillimetre Telescope) is a European science mission that will perform photometry and spectroscopy in the 80-670 tm range. The proposed heterodyne instrument for FIRST is a seven-channel receiver, which combines the high spectral resolving capability (O.3-300km/s) of the radio heterodyne technique with the low noise detection offered by Superconductor-Insulator-Superconductor (515) and Hot Electron Bolometer (HEB) mixers. It is designed to provide almost continuous frequency coverage from 480-2700 GHz. The Jet Propulsion Laboratory is responsible for developing and implementing the local oscillator sources for the 1200-2700 GHz mixers. The present state-of-the-art approach for millimeter-wave multipliers, based on waveguide blocks and discretely mounted devices, becomes harder and harder to implement as the frequency range is extended beyond 300 GHz. This talk will focus on the technology that is being developed to enhance and extend planar integrated Schottky devices and circuits to meet mission local oscillator requirements. The baseline approach is to use GaAs power amplifiers from 7 1 to 1 15 GHz followed by a series of planar Schottky diode varactor multiplier stages to generate the required LO signal. The circuits have to be robust, relatively easy to assemble, and must provide broad fix-tuned bandwidth. A number of new technology initiatives being implemented to achieve these goals will be discussed. Approaches include quartz-based and substrate-less diode circuitry and integrated GaAs membrane technology. Recent results and progress-to-date will be presented.