One single travelling-wave MMIC for highly linear broadband - Mixers and variable gain amplifiers

A travelling-wave circuit concept allowing device application both as ultra-broadband mixer and variable gain distributed amplifier is presented and demonstrated. The compact layout MMIC is realized in a 0.15 mu m GaAs pHEMT technology. Cascode amplifier cells with current-voltage feedback are used in eight-stage distributed configuration. In VGA mode, the gain may be controlled between 5-12dB with a near-constant bandwidth of up to 43GHz and excellent power matching properties. The amplifier is capable of delivering 20dBm to a 50 Omega load. Being operated as travelling-wave mixer, the device exhibits 2dB conversion loss in a bandwidth exceeding 50GlIz, while requiring the comparatively low LO power of 5dBm. Mixer operation is demonstrated both for downconversion to fixed IF- and for broadband conversion using fixed LO frequencies. In mixer mode, exceptionally high input-related linearity of 6dBm is reached.