W.H. Haydl

Millimeter-wave performance of chip interconnections using wire bonding and flip chip

The performances of two different interconnection techniques for coplanar MMICs, wire bonding and flip chip, are investigated at millimeter-wave frequencies. By developing an accurate model for the interconnections, which is validated with experimental data up to 120 GHz, the limitations with respect to frequency and interconnection distance of either technique are pointed out, yielding useful data for the design of hybrid MMW-subsystems.

On the use of vias in conductor-backed coplanar circuits

Ground planes of conductor-backed coplanar waveguides (CBCPWs) behave like overmoded patch antennas supporting parallel-plate modes and show numerous resonances. For typical monolithic-microwave integrated-circuit chip sizes, these unwanted resonance frequencies lie within the microwave and millimeter-wave frequency region. Due to this feedback mechanism, todays coplanar millimeter-wave amplifiers operating up to 250 GHz require special packaging techniques for stable operation. The use of vias is one method of suppressing parallel-plate modes. The effect of via-holes within a ground plane and the effect of an open or a shorted ground-plane periphery on the parallel-plate modes of CBCPWs were investigated in depth up to 200 GHz for quartz and GaAs substrates. It is shown that the placement of the vias within the coplanar-waveguide structure is crucial for the suppression of parallel-plate modes. If properly placed, vias are an effective means to suppress these unwanted modes over a chosen frequency range.

W-band HEMT-oscillator MMICs using subharmonic injection locking

The efficient stabilization of high electron mobility transistor (HEMT) oscillator monolithic microwave integrated circuits (MMICs) for W-band applications, using a new approach of high-order subharmonic injection locking, is presented. Transmission- and reflection-type injection locking techniques are applied to stabilize 94-GHz oscillators based on GaAs pseudomorphic-HEMT technology. A voltage-controlled oscillator MMIC was developed, consisting of the oscillator circuit and an integrated harmonic generator that can be stabilized by injection power levels of -45 dBm at 94 GHz using reflection-type injection locking, allowing reference frequencies as low as the fifteenth to twenty-first subharmonic as the input for the harmonic generator. Additionally, an injection-locked phase-locked loop (PLL) was developed, which enhances the locking range from 30 MHz to 1 GHz, using the twenty-first subharmonic as a reference signal. The combination of simple synchronization to a low-frequency reference signal and the control of the synchronization in the injection-locked PLL allows the generation of stable and low-noise millimeter-wave signals with a fully integrated MMIC source.

Models of coplanar lines and elements over the frequency range 0-120 GHz

The electrical properties of uniform coplanar lines on GaAs have been investigated, using a finite element simulator. Experimental results, extracted from on-wafer measurements to 120 GHz, are in good agreement with the simulated results. Frequency dependent models were developed for all characteristic parameters of the coplanar lines, such as impedance, effective relative dielectric constant and attenuation, describing the behavior of coplanar lines of different geometries over the entire frequency range from 0-120 GHz. Similarly, exact models applicable over the same frequency range have been developed for a number of coplanar elements, such as air bridges, 90 degree corners and probing pads. These models have been implemented in our HP-MDS data base, resulting in accurate designs of a number of millimeter wave circuits.

Coplanar millimeter-wave ICs for W-band applications using 0.15 /spl mu/m pseudomorphic MODFETs

A small signal S-parameter and noise model for the cascode MODFET has been validated up to 120 GHz, allowing predictable monolithic microwave integrated circuit (MMIC) design up to W-band. The potential of coplanar waveguide technology to build compact, high performance system modules is demonstrated by means of passive and active MMIC components. The realized passive structures comprise a Wilkinson combiner/divider and a capacitively loaded ultra miniature branch line coupler. For both building blocks, very good agreement between the measured and modeled data is achieved up to 120 GHz. Based on the accurate design database, two versions of compact integrated amplifiers utilizing cascode devices for application in the 90-120 GHz frequency range were designed and fabricated. The MMICs have 26.3 dB and 20 dB gain at 91 GHz and 110 GHz, respectively. A noise figure of 6.4 dB was measured at 110 GHz. The 90-100 GHz amplifier was integrated with an MMIC tunable oscillator resulting in a W-band source delivering more than 6 dBm output power from 94 to 98 GHz.

Resonance phenomena and power loss in conductor-backed coplanar structures

Resonances and associated power loss which occur in conductor backed coplanar transmission lines (CPWs) at selected frequencies have been investigated by experiment and by three-dimensional (3-D) EM simulations from 1 to 230 GHz. It is found that a substantial part of the incident power is lost by reflection and radiation. The resonance frequencies are predictable by patch antenna theory.

Single-chip coplanar 94-GHz FMCW radar sensors

A low-cost 94-GHz monolithically integrated coplanar FMCW radar chip has been developed, using 0.15-μm AlGaAs-InGaAs-GaAs PM-HEMT technology. The chip includes a VCO, electrically tunable over several gigahertz, transmit and receive amplifiers, a mixer, and a directional coupler. The monolithic microwave integrated circuits (MMICs) are as small as 8 mm2, delivering up to 10 mW of radio frequency (RF) power at a DC power consumption of 0.7 W. The receiver noise figure is 6-7 dB, and the conversion gain is 10 dB.

W-band MMIC VCO with a large tuning range using a pseudomorphic HFET

A widely tunable oscillator with a center frequency of 94 GHz including a two stage buffer amplifier has been designed and fabricated, The output power was 6 mW. The mechanical tuning range by removing air-bridges was 18 GHz. The electrical tuning range was 8 GHz. The noise performance was better than -67 dBc/Hz at 1 MHz from the carrier.

Design data for millimeter wave coplanar circuits

Theoretical and experimental data for the characterization and design of coplanar lines for millimeter wave ICs is presented for the substrates gallium arsenide (GaAs), indium phosphide (InP) and quartz. The theoretical data is based on the simplified model of Heinrich [1]. The experimental data was obtained by on-wafer S-parameter measurements up to 60 GHz on coplanar lines of different dimensions, and subsequent modeling and data extraction. Excellent agreement has been observed between theory and experiment.

Avoiding cross talk and feed back effects in packaging coplanar millimeter-wave circuits

The impact of the packaging configuration on cross talk and feed back effects caused by parasitic substrate modes is investigated for coplanar millimeter-wave circuits. It is demonstrated theoretically and by means of several circuit examples that both the mounting configuration and the thickness of the semiconductor substrate of coplanar MIMICs have to be chosen appropriately, in order to avoid circuit degradation or even failure.