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A plastic, 95-GHz rectangular waveguide with an integrated plastic flange has been successfully demonstrated using micro hot embossing and electroplating technologies. Two prototype devices with integrated flanges on both ends have been tested using an Agilent PNA 5250 network analyzer. The prototype with non-metallized flange shows return loss s11 and insertion loss s21 values of −21.5 and −1.09 dB at 108 GHz, respectively with signal transmission rate at 77.8%. The prototype with metallized flange has s11 and s21 values of −31.5 dB and −0.7 dB, respectively, at 92.5 GHz, with signal transmission rate at 85%. The time domain measurement showed that the system losses are mainly due to the discontinuity losses at the interfaces between the network analyzer adaptors and the waveguide input/output ports. These losses could be further minimized in future integrated systems. As such, this new class of plastic waveguides has potential applications in replacing the expensive and bulky/heavy metallic waveguides in current millimeter-wave systems. © 2005 Elsevier B.V. All rights reserved.

Recent developments in micromachining techniques at the University of Michigan have resulted in novel high-performance low-loss filters for microwave and millimeter-wave applications. The idea is based on suspending the filters on thin dielectric membranes to eliminate dielectric loss and dispersion problems, resulting in a pure TEM mode of propagation and conductor-loss-limited performance. The dielectric membrane and the surrounding cavities are built using chemical etching in Silicon and GaAs wafers. The filters are therefore compatible with low-cost IC fabrication techniques and can be com- bined with planar diodes and transistors to result in active filter networks. Several state-of-the-art filters have been realized including 15-GHz and 20-GHz bandpass interdigi- tal suspended stripline filters, lowpass and bandpass microshield filters at 30 GHz and 90 GHz, microstrip 94-GHz bandpass filters, and a 250-GHz bandpass filter with 1.0-1.5-dB insertion loss. This article reviews the associated fabrication techniques, the different types of transmission lines achieved using this technology, and the measured performance from 15 to 350 GHz. The study concludes with a detailed description of the future work in this area. Q 1997 John Wiley & Sons, Inc. Int J Microwa'e Millimeter-Wa'e CAE 7: 149-166, 1997.

We report on stripline resonators on thin dielectric membranes that show dispersion-free, conductor-loss limited performance at 13.5 GHz, 27.3 GHz, and 39.6 GHz. The unloaded-Q (Q/sub u/) of the resonators increases as /spl radic/f with frequency and is measured to be 386 at 27 GHz. The measured results agree well with a new conformal mapping analysis. The stripline resonators are used in a micromachined state-of-the-art planar interdigitated bandpass filter at K-band frequencies. Excellent agreement has been achieved between the microwave model at 850 MHz and the 20 GHz filter. The micromachined filter exhibits a passband return loss better than -15 dB and a conductor-loss limited 1.7 dB port-to-port insertion loss (including input/output CPW line loss) at 20.3 GHz.

Planar microwave and millimeter-wave inductors and capacitors have been fabricated on high-resistivity silicon substrates using micro-machining techniques. The inductors and capacitors are suspended on a thin dielectric membrane to reduce the parasitic capacitance to ground. The resonant frequencies of a 1.2 nH and a 1.7-nH inductor have been increased from 22 GHz and 17 GHz to around 70 GHz and 50 GHz, respectively. We also report on the design and measurement of a new class of stripline filters suspended on a thin dielectric membrane. Interdigitated filters with 43% and 5% bandwidth have been fabricated and exhibit a port-to-port 0.7 dB and 2.0 dB loss, respectively, at 14-15 GHz. The micro-machining fabrication technique can be used with silicon and GaAs substrates in microstrip or coplanar-waveguide configurations to result in planar low-loss lumped elements and filters suitable for monolithic integration or surface mount devices up to 100 GHz. >

The PDB (planar doped barrier) diode consists of a p/sup +/ doping spike between two intrinsic layers and n/sup +/ ohmic contacts. Such devices can have an anti-symmetric current vs. voltage characteristic. The capacitance is approximately constant with the applied voltage, and the barrier height and device capacitance are easily adjustable. These characteristics make the PDB a candidate for millimeter- and submillimeter-wave subharmonic mixers. We have fabricated 2 and 4 /spl mu/m diameter diodes with different barrier designs using GaAs epi-layers. The devices are planarized using an air-bridge and a surface channel etch. After completely removing the substrate, the devices are mounted on a quartz substrate to reduce parasitic effects. Diced diodes were tested as subharmonic mixers around 200 GHz in both a quasi-optical planar wideband subharmonic receiver and a planar-diode waveguide-mixer. The quasi-optical measurements show that a 0.23 V (and 0.4 V) barrier height GaAs diode with 2.0 /spl mu/A (and 5 nA) of saturation current gives a DSB conversion loss of 10.8 dB (and 9.5 dB) and a DSB noise temperature of 3795/spl deg/ K and 2450/spl deg/ K). The waveguide mixer measurements were made with a similar 0.23 V barrier height PDB. Such a mixer has a minimum conversion loss of 10.2 dB and noise temperature of 3570/spl deg/ K, and requires only 1.2 milliwatts of available LO power. >

Recently, millimeter-wave devices have been attracted more attentions in applications owing to their short wavelengths, higher resolutions, broader bandwidths and higher environmental tolerance. The great challenges of high fabrication and assembly costs, bulky volumes, and heavy weights of millimeter-wave systems call for new integrated manufacturing techniques. The hot embossing technique could address these challenges. In this paper, a review of micro plastic hot embossing was given for the fabrication of miniaturized millimeter-wave systems. The micro hot embossing on plastic materials demonstrated its advantages on significant costs, volume and weight reduction, while maintaining high performances. We have designed, fabricated and characterized a W-band rectangular waveguide and a W-band iris waveguide filter with integrated plastic flanges using micro hot embossing and selective electroplating. In this paper, we reviewed the results and discussed the design methodology in details for the micromachined components. The prototype devices showed promise for the system designs.

A plastic, 95-GHz rectangular waveguide with an integrated plastic flange has been successfully demonstrated using micro hot embossing and electroplating technologies. The prototype device shows s/sub 11/ and s/sub 21/ values of -20.7 dB and -1.35 dB at 95GHz, respectively, and the signal transmission rate is 73.3% as compared to commercial all-metal waveguides at 85%. The time domain measurement showed the system losses are mainly due to the discontinuity losses at the interfaces between the network analyzer adaptors and the waveguide input/output ports and could be further minimized in future integrated systems. As such, this new class of plastic waveguides has potential applications in replacing the expensive yet bulky/heavy metallic waveguides in current millimeter-wave systems.

A micromachined W-band iris filter was successfully demonstrated using micro hot embossing and selective electroplating technologies. The filter design follows the insertion loss method with a Chebyshev polynomial to synthesize the desired spectral responses and numerical simulations were performed using the finite-element tool, high frequency structure simulator (HFSS), to study the effects of iris thickness on the bandwidth and center frequency. The measured prototype filter performance has a transmission loss of -3.49 dB and a return loss of -18 dB at the resonant frequency of 95 GHz. The filter has a bandwidth of 3.5 GHz and a rejection loss of better than -50 dB, while the loaded quality factor is 27.27. This plastic, low-cost manufacturing process opens up opportunities in replacing the expensive metallic components and integrated 3D manufacturing for current and future millimeter-wave systems.

Subharmonically pumped mixers using zero-biased anti-parallel Schottky diode pairs produce good results, but require a larger LO power than biased Schottky diodes. Presented here is a novel planar-diode anti-parallel pair that allows independent biasing of the two diodes. This diode pair is integrated into a quasi-optical wideband receiver and the RF measurements on a 1.2-/spl mu/m anode diameter pair show a reduced LO power requirement at 180 GHz by a factor of 2 to 3 with a similar DSB conversion loss and noise temperature (9.7 dB and 1850 K) to an unbiased Schottky diode pair. This structure has potential for applications at submillimeter-wave frequencies where a large amount of LO power is not easily available. >

We present for the first time a quasi optical mixer realized as a resistive HFET mixer with an integrated slot antenna. The mixer circuit conversion loss, defined as the measured IF-power in the 50 ohm load divided by the RF-power available at the slot-antenna terminals, is approximately 7 dB at an LO-power of 10.5 dBm when the mixer is fundamentally pumped, and 16 dB for subharmonically pumping at 10 dBm LO-power. >

A novel quasi-optical planar subharmonically pumped receiver including a log-periodic antenna and an anti-parallel Schottky diode pair with independent bias is presented. The antenna and Schottky diode pair have a 20 /spl mu/m and 2.5 /spl mu/m wide split, respectively, for biasing considerations and an overlay capacitor for RF coupling. Millimeter-wave measurements at 91 GHz show that, at /spl plusmn/0.4 V bias, the separately biased subharmonic mixer requires 2-3 times less LO power than the zero-biased subharmonic mixer for the same 8 dB (SSB) conversion loss. At 180 GHz a similar LO power requirement reduction has been achieved, with a minimum conversion loss of 9.7 dB and noise temperature of 1850 K (DS8). >

Planar millimeter-wave microstrip inductors and capacitors have been fabricated on high-resistivity silicon substrates using micro-machining techniques. The spiral inductors and interdigitated capacitors are suspended on a thin dielectric membrane to reduce the parasitic capacitance to ground. The resonant frequencies of a 1.2 nH and a 1.7 nH inductor fabricated on a high-resistivity silicon substrate and on a small dielectric membrane, have been increased from 22 GHz and 17 GHz to 73 GHz and 54 GHz, respectively. The planar micro-machined elements are compatible with the via-hole technology process in GaAs and InP MMIC, and can be used as true inductors and capacitors up to 50-60 GHz. The technique can be also applied to lumped elements in coplanar-waveguide transmission lines. >

The extrinsic transconductance of a PHEMT device is examined using a rigorous isothermal pulsed I-V technique. The extrinsic transconductance is determined directly from the pulsed I-V (gm pulsed) measurements and compared with pulsed S-parameter measurements (gm RF). The discrepancy between gm pulsed and gm RF for the Vgs range of -1.0 to -0.4 is less than 10%. Transconductance extracted from the conventional DC I-V measurements (gm DC) differs by greater than 35% from the gm RF values over this same Vgs range.

We report on the results of a state-of-the-art planar interdigitated bandpass filter at K-band by using micromachining techniques. In this design, a microwave model was first built at 850 MHz to simulate the K-band filter, and the 20 GHz micromachined filter was fabricated based on the 850 MHz microwave model. Excellent agreement has been achieved between the microwave model and the 20 GHz filter. The micromachined filter exhibits a return loss better than -15 dB within the passband and a 1.7 dB port-to-port insertion loss at 20.3 GHz. A grounded coplanar waveguide with a micromachined mouse-hole shielding structure has also been carefully examined. The grounded coplanar waveguide structure is used in the micromachined filter as the input/output feeding line and exhibits a return loss better than -20 dB up to 32 GHz. >

We report on the design and measurement of a new class of stripline filters for millimeter-wave applications. The novelty in this work is to suspend the interdigitated lines on a thin dielectric membrane to eliminate the dielectric losses and to render the interdigitated filter physically realizable at millimter-wave frequencies. A wide band filter with a center frequency of 13.7 GHz and a bandwidth of 45% has been fabricated. The filter exhibits a port-to-port insertion loss of 0.7dB at 13.7 GHz. This fabrication technique can be easily used at higher frequencies to result in planar low loss filters suitable for monolithic integration or surface mount devices up to 40-60 GHz.