M. Schlechtweg

This letter presents coplanar integrated directional couplers for 90 and 180 GHz with a 60-GHz (120-GHz) band- width and up to 20-dB directivity. A three-dimensional (3-D) field simulator has been used to calculate the complex propagation constants and the impedances of the two modes. For the first time, the comparison of simulated and measured -parameters up to 230 GHz shows the validity of the design approach and the capability of integrated coplanar couplers.

Compact high-gain W-band multistage amplifier MMIC's have been developed in coplanar technology using 0.15- mu m AlGaAs/InGaAs/GaAs PM-HEMT's. The conventional dual-gate HEMT has been modified to include an additional interstage network between the common-source and the common-gate HEMT. The effect of stabilizing circuit elements has been investigated. A gain of 10 dB per cascode stage is obtained at 94 GHz. Multistage amplifier MMIC's with up to 40-dB gain have been realized

A 58 GHz amplifier module with more than 55 dB gain has been developed in coplanar technology. The signal distortion could be minimized by using a low number of substrates and high performance interconnection and packaging technologies. Flip chip bonding of the MMICs allowed the minimization of the parasitic inductance and capacitance of the chip interconnection. By two local cavities, realized as substrate integrated packages (SIP) on one thin film substrate, a miniaturized solution to reduce cross talk inside the package was used resulting in an isolation of more than 80 dB. The coupling of the coplanar mode to other parasitic modes could be suppressed by a special coplanar feed-through for the SIP. A direct coaxial to coplanar transition allowed the realization of a pure coplanar signal path between the coaxial connectors at the module input and output.

The potential of HEMT oscillators as signal sources for millimeter wave systems was investigated. Free running, varactor tuned and subharmonic injection locked oscillators, based on 0.15 μm AlGaAs/InGaAs/GaAs HEMTs have been developed at millimeter wave frequencies from 35 to 94 GHz. Integration of these oscillators with amplifiers in a coplanar environment has been demonstrated.

Reproducible pseudomorphic MODFET MMIC amplifiers with 18.5 dB gain at 51 GHz were realized in coplanar waveguide technology. An on-wafer S-parameter measurement system up to 75 GHz was developed to establish the MMIC design database. The RF wafer yield of the MMICs is greater than 80%. The system advantages of CPW for multi-chip modules are demonstrated by a 6-stage amplifier comprising 2 cascaded chips, resulting in a gain of 37.5 dB at 51 GHz and 21.5 dB at 60 GHz. Our measurements proof absolute stability of the realized modules. The MMICs were inserted into a V-Band waveguide module comprising the CPW/waveguide transitions. The measured gain and noise figure of the waveguide module was 16 dB and 6.0 dB at 54 GHz, respectively.