Harris P. Moyer

Passive Millimeter-Wave Imaging Module With Preamplified Zero-Bias Detection

An analytical model and supporting measured data are presented for a preamplified W-band radiometer with a zero-bias detector appropriate for commercial millimeter-wave imaging cameras. Basic radiometer parameters, including RF bandwidth, are computed directly from simple low-frequency measurements and compare well with those obtained from RF measurements. A detailed analytical model shows how radiometer performance depends on internal component parameters, such as low-noise amplifier gain, noise factor, reflection coefficient, detector responsivity, etc. The measurements suggest that performance is sufficient for operation without a Dicke switch or mechanical chopping. A measured noise equivalent temperature difference of 0.45 K was obtained, assuming a single sensor is scanned across a focal plane, forming 32 pixels with 3.125-ms integration time per pixel. This sensitivity is considered sufficient by commercial manufacturers to obtain quality images in low-contrast (e.g., indoor) environments.

GaN MMIC technology for microwave and millimeter-wave applications

In this paper we demonstrate the merits of GaN MMIC technology for high bandwidth millimeter-wave power applications and for microwave robust LNA receiver applications. We report the development of a broadband two-stage microstrip Ka-band GaN MMIC power amplifier, with 15dB of flat small signal gain over the 27.5GHz to 34.5GHz frequency range and 4W of saturated output power at 28GHz, with a power added efficiency of 23.8%. This is to the best of our knowledge the best combination of output power, bandwidth and efficiency reported for a GaN MMIC in Ka-band frequency range. We also report a robust two-stage wideband (0.5GHz-12GHz) GaN LNA MMIC, which can survive 4W of incident input RF power in CW mode without input power protective circuitry. The presented LNA MMIC has, to the best of our knowledge, the best combination of NF, bandwidth, survivability and low power consumption reported to date in GaN technology.

GaN MMIC PAs for E-Band (71 GHz - 95 GHz) Radio

High data rate E-band (71 GHz- 76 GHz, 81 GHz - 86 GHz, 92 GHz - 95 GHz) communication systems will benefit from power amplifiers that are more than twice as powerful than commercially available GaAs pHEMT MMICs. We report development of three stage GaN MMIC power amplifiers for E-band radio applications that produce 500 mW of saturated output power in CW mode and have > 12 dB of associated power gain. The output power density from 300 mum output gate width GaN MMICs is seven times higher than the power density of commercially available GaAs pHEMT MMICs in this frequency range.

Ka-band MMIC power amplifier in GaN HFET technology

We report the development of Ka-band GaN MMIC power amplifiers in CPW and microstrip topologies. This is, to the best of our knowledge, the first demonstration of millimeter wave MMICs in GaN technology. The single stage CPW MMIC utilizes four 2/spl times/100 /spl mu/m wide GaN HFETs whilst four 4/spl times/60 /spl mu/m wide HFETs with individual through substrate source vias were used for the microstrip MMICs. The CPW amplifier has a gain peak of 8 dB at 33 GHz with 4 GHz bandwidth while the microstrip amplifier has a peak gain of 9 dB at 27 GHz and gain higher than 8 dB over the 2.45 GHz to 33 GHz frequency range. The saturated CW output power of the amplifiers measured into a 50 /spl Omega/ system at 33 GHz was, respectively, 1.6 W for the microstrip MMIC. The corresponding power density of 2.3 W per mm of gate periphery for the microstrip MMIC is by a factor of 4 higher than that of a typical GaAs pHEMT MMIC at this frequency. Microstrip MMIC performance was further improved through external output impedance matching, resulting in power levels of up to 2.8 W (27% associated PAE) and peak PAEs of up to 36.2% (1.2 W associated power).

GaN Technology for E, W and G-Band Applications

Highly scaled GaN T-gate technology offers devices with high ft/fMAX, and low minimum noise figure while still maintaining high breakdown voltage and high linearity typical for GaN technology. In this paper we report an E-band GaN power amplifier (PA) with output power (Pout) of 1.3 W at power added efficiency (PAE) of 27% and a 65-110 GHz ultra-wideband low noise amplifier (LNA). We also report the first G-band GaN amplifier capable of producing output power density of 296mW/mm at 180 GHz. All these components were realized with a 40 nm T-gate process (ft= 200 GHz, fMAX= 400 GHz, Vbrk > 40V) which can enable the next generation of transmitter and receiver components that meet or exceed performance reported by competing device technologies while maintaining > 5x higher breakdown voltage, higher linearity, dynamic range and RF survivability.

A Low Noise Chipset for Passive Millimeter Wave Imaging

Technology for passive millimeter wave imaging has been maturing over the last 4-5 years. One key piece of technology that will allow for large scale production is a low cost front-end receiver. We have developed a two chip solution that addresses this need at W-band. A four stage InP LNA with a pre-matched Sb-heterostructure diode provides a low noise equivalent temperature difference (NETD). Our fabricated chipset provides sensitivities of 10,000 mV/muW over a 22 GHz noise equivalent bandwidth and an NETD of 0.8 K. To our knowledge, this is the best performance to date of a two chip solution for a passive millimeter wave radiometer.

A unified analytical model and experimental validations of injection-locking processes

Unified analytical expressions predicting the locking range for fundamental, subharmonic (n=2), superharmonic (n=2), and parametric injection (m=n=p=1) locking are presented and compared in this paper. Power series are employed to model the device nonlinearity. The /spl alpha/-parameters, relating nonlinear I-V behavior, are extracted using a harmonic-balance approach. These expressions are verified using an UHF oscillator; and good agreement is obtained between the experimental and analytical results.

High efficiency X-band class-E GaN MMIC high-power amplifiers

We have demonstrated 8.5-11.5 GHz class-E MMIC high-power amplifiers (HPAs) with a peak power-added-efficiency (PAE) of 61% and drain efficiency (DE) of 70% with an output power of 3.7 W in a continuous-mode operation. At 5 W output power, PAE and DE of 58% and 67% are measured, respectively, which implies MMIC power density of 5 W/mm at Vds = 30 V. The peak gain is 11 dB, with an associated gain of 9 dB at the peak PAE. At an output power of 9 W, DE and PAE of 59% and 51 % were measured, respectively. In order to improve the linearity, we have designed and simulated X-band class-E MMIC PAs similar to a Doherty configuration. The Doherty-based class-E amplifiers show an excellent cancellation of a third-order intermodulation product (IM3), which improved the simulated two-tone linearity C/IM3 to >; 50 dBc.

W-Band Sb-Diode Detector MMICs for Passive Millimeter Wave Imaging

A W-band monolithic microwave integrated circuit (MMIC), including an Sb-heterostructure diode on a GaAs substrate, has been demonstrated. The MMIC also includes the RF choke and output shorting capacitor essential to detector circuits. Additional input matching has yielded peak sensitivities on the order of 10 000 V/W and equivalent bandwidths of 40 GHz. Using these circuits in conjunction with current W-band low-noise amplifier technology can achieve the sub-1degK noise equivalent temperature difference necessary for producing discernible images with W-band passive imaging cameras.

Sb-Heterostructure Low Noise W-Band Detector Diode Sensitivity Measurements

Sb-heterostructure diodes have become the detector of choice for W-band millimeter wave imaging cameras. Here we demonstrate lower impedance versions that optimize noise equivalent power (NEP). The goal is to decrease the gain required of the RF pre-amplifier, ideally to zero. Measured W-band sensitivities for three diodes are 3500, 5500, and 6000 V/W. Their zero bias differential resistance values imply Johnson noise limited NEPs of 0.98, 0.83, and 0.79 pW/Hzfrac12, respectively, much less than obtained from conventional Schottky diodes. A wideband transition from a horn antenna to the 6000 V/W detector has produced an integrated bandwidth of 30 GHz with implied temperature sensitivity (NEDeltaT) close to 10degK