Ka-band direct transmitter modules for baseband pre-compensation

This paper presents two different RF modules for implementation in a Ka-band direct transmitter architecture with feedback for baseband I/Q pre-compensation. The first module is realized using conventional MIC technology, and combines a direct Ka-band SSB modulator, a driver amplifier, a microstrip directional coupler, and a detector circuit in the feedback loop. A maximum conversion gain of +9.6dB is measured at 29GHz. The second module was fabricated using LTCC technology to provide similar functionality in a more compact package. Measured conversion gain for this unit reaches a maximum of +6.1dB at 29GHz. With pre-compensation, suppression levels of at least 40dB for the carrier, and 30dB for the image sideband, have been achieved for both modules.