Alexis Zamora

A Wideband, Pressure-Driven, Liquid-Tunable Frequency Selective Surface

A wideband, liquid-metal-based, tunable frequency selective surface is presented. The structure consists of a periodic array of liquid mercury (Hg) volumes separated by gaps of mineral oil, encapsulated by an array of parallel polytetrafluoroethylene tubes. Tunability is achieved via pressure-driven fluidic control over the respective volumes of Hg and oil. A tuning range of 4.08-16.96 GHz (122.4% fractional bandwidth) is demonstrated.

Recent progress in scaling InP HEMT TMIC technology to 850 GHz

In this paper, recent work on pushing InP HEMT amplifier technology to 850 GHz is reported. In particular, we have demonstrated on-wafer gain at this frequency. To our knowledge, this is the first time gain has been reported at this frequency. This achievement is possible by transistor scaling, frontside and backside feature scaling and detailed transistor modeling and design.

A 0.85 THz Low Noise Amplifier Using InP HEMT Transistors

In this letter, the first packaged THz solid-state amplifier operating at 0.85 THz is reported. The InP HEMT amplifier achieves a noise figure as low as 11.1 dB with an associated gain of 13.6 dB at 0.85 THz using high fMAX InP HEMT transistors in a 10-stage coplanar waveguide integrated circuit. Output power up to 0.93 mW is measured.

An Interleaved, Interelement Phase-Detecting/Phase-Shifting Retrodirective Antenna Array for Interference Reduction

An interleaved, interelement phase-detecting/phase-shifting retrodirective antenna array for interference reduction is presented. This system uses two independent retrodirective subarrays to form a null in one direction while retrodirecting a beam in another direction, while also eliminating the R4 path loss of previous interleaved architectures. Retrodirectivity as well as null steering is reported at 2.4 GHz.

A self-steering array using power detection and phase shifting

A half-duplex self-steering array using power detection and phase shifting is presented. The system combines a phase-shifting array and an RF power-tracking control circuit to autonomously steer its beam toward the peak-power direction. Retrodirectivity is reported for angles of 0Ð, −15Ð, −30Ð, and +45Ð at a transmitting frequency of 6.5 GHz.

Multiple interrogation of phase-conjugating arrays

The performance of a phase-conjugating array (PCA) in a multiple-interrogator environment is investigated. The PCA demonstrates the ability to properly retrodirect signals toward multiple interrogators to varying degrees, dependent on phase, angle of incidence, and amplitude differences between the interrogators. The effect of the three parameters is demonstrated for the 6-GHz array at interrogating angles of ±10° and ±20°. Agreement between the experimental results and theoretical simulations confirm the validity of the measurements; extrapolation of the simulations for additional cases is also presented.

A 670 GHz Low Noise Amplifier with <10 dB Packaged Noise Figure

In this letter, a packaged Low Noise Amplifier (LNA) operating at 670 GHz is presented. The LNA uses a new generation of 25 nm InP HEMT with 1.5 THz fMAX. The eight-stage amplifier shows approximately 16 dB associated gain in package with a noise figure ranging from 9.4-9.9 dB measured across a 15 GHz bandwidth. These results represent better than 3 dB improvement in sensitivity to previously published InP HEMT results, and represent the lowest measured noise figure for any LNA at this operating frequency.

A Submillimeter Wave InP HEMT Multiplier Chain

In this letter, we demonstrate the first 400 GHz multiplier chain with integrated buffer amplifiers through the chain. The x9 multiplier chain uses 25 nm InP HEMT MMIC technology. The chain consists of three packaged MMICs in split-block waveguide packages with each multiplier incorporating an integrated output buffer. We report a peak output of 6.9 mW and greater than 4 mW over a 10% bandwidth.

A ×18 340 GHz InP HEMT multiplier chain

We demonstrate a ×18 340 GHz multiplier chain using 25 nm InP HEMT technology. The active multiplier chains topology consists of three packaged MMICs in two split-block waveguide packages. The multiplier chain uses HEMT multipliers with integrated output buffers to convert an input frequency centered at 18.8 GHz to 340 GHz. The presented work demonstrates an electronically tunable multiplier chain outputting a peak power of 8 dBm at 340 GHz while consuming only 445 mW of DC power. This gives a peak efficiency of 1.4% for the ×18 entire chain. This demonstrates that adding power amplification to the output significantly enhances the efficiency of submillimeter wave power generation using multiplier chains.

An inter-element phase-detecting retrodirective array for nonuniform wavefronts

A retrodirective array designed to respond to nonuniform wavefronts is presented. The design overcomes the limitations of existing phase-detection-based retrodirective array architectures by measuring the phase difference between adjacent element pairs to increase array resolution. The transmit and receive frequencies are 2.45 and 2.4 GHz, respectively. Measurements demonstrate the ability to retrodirect to both single and multiple interrogators.