Nada El-Zein

X-band heterostructure interband tunneling FET (HITFET) VCOs

This paper reports on the DC and microwave performance of novel X-band voltage controlled oscillators fabricated by integrating heterostructure interband tunneling diode (HITD) with a heterostructure FET. The measured RF performance of VCOs incorporating single and double HITDs is discussed. The power output of the single HITD VCO was 2.0 dBm and that of the dual HITD was 4.3 dBm at a center frequency of 8.2 GHz. The dual HITD VCO also exhibited a wider tuning range than the single HITD VCO. The phase noise of these VCOs was approximately -128 dBc, 3 MHz away from the center frequency.

Microfabrication of two layer structures of electrically isolated wires using self-assembly to guide the deposition of insulating organic polymer

Abstract The fabrication of two layer structures of electrically isolated wire — crossed wire structures and a surface coil inductor — is described. The fabrication process utilizes the tools of soft lithography and incorporates two levels of self-assembly. The use of microcontact printing and patterned self-assembly of liquid polymers removes the need for registration of the insulating layer with the underlying layer as required in conventional lithography techniques. The performance characteristics of the surface coil inductor are measured and closely resemble those predicted by theory.

DC and RF characterization of different heterojunction interband tunneling diodes

Tunnel diodes are semiconductor devices with the unique property of negative differential resistance (NDR). These devices show great potential for power generation at high frequencies. Heterostructure interband tunneling diodes (HITDs) when integrated with heterojunction FETs (HFETs) produce a three-terminal device that we call a HITFET. The NDR characteristics of a HITFET can be controlled by either the gate or drain biases. Devices and circuits based on HITDs and HITFETs have shown great promise and are being considered in many digital and analog applications. To satisfy the variety of matching conditions for the combination of the different devices and to facilitate the integration, it is important to have flexibility and good control over the tunnel diode electrical characteristics. We report our investigation of HITDs in the In/sub 0.53/Ga/sub (0.47)/As/In/sub (0.52)/Al/sub (0.48)/As/InP material system. We study and optimize the dependence of the tunnel diode peak current density on p/sup +/ doping levels, quantum well widths, and doping layer thicknesses. We also introduce a new interband tunnel diode structure with almost an order of magnitude higher peak current density (/spl sim/40,000A/cm/sup 2/) while maintaining a reasonable peak to valley current ratio of approximately 20. We investigate the high frequency properties of these tunnel diodes and compare the new and the conventional HITD performance.

Low loss air-gap spiral inductors for MMICs using glass microbump bonding technique

Air-gap spiral inductor structures have been fabricated and itegrated with semiconductor substrates using glass microbump bonding (GMBB) techniques. Spiral inductors using air-gap structures have the advantages of low losses, and low parasitic capacitance compared to conventional inductors on doped silicon semiconductor substrate. Stacked air-gap spiral inductors on GaAs substrates using GMBB techniques also can reduce the inductor area. Because the glass microbump bonding techniques are simple, this bonding technique provides an alternative integration approach for monolithic microwave integrated circuits (MMICs). Experimental results of air-gap spiral inductor on both silicon and GaAs substrates are presented in this paper.

A comprehensive DC/RF tunnel diode model and its application to simulate HITFETs (heterostructure integrated tunneling FETs) and quantum-MMIC's

A comprehensive tunnel diode large signal model that incorporates the bias voltage dependence of its RF characteristics is developed. The model consists of a voltage controlled current source and is implemented in the Advanced Design System (ADS) simulation tool. This model is applied to simulate heterostructure integrated tunneling field effect transistor (HITFET) devices and circuits. HITFETs are quantum functional devices realized by monolithically integrating tunnel diodes and FETs. The enhanced functionality of a HITFET is utilized to design novel circuits with reduced complexity and size and having better performance. Many HITFET based circuits, such as voltage controlled oscillators, amplifiers, mixers, and antennas have been proposed and demonstrated. This new technology shows promise for portable communication applications and monolithic microwave integrated circuits (MMICs). This large signal model incorporated in ADS enables designers to simulate monolithic, multifunctional ICs containing tunnel diodes and HITFETs.

A MMIC lumped element directional coupler with arbitrary characteristic impedance and its application

In this paper the design technique for MMIC lumped element directional couplers, based on arbitrary termination impedance, is described. Arbitrary impedance terminations allow matching the linear and nonlinear elements to the coupler without the requirement of transformer networks. The techniques capability is demonstrated through the design of a single balanced mixer prototype at 1.8GHz for which measured and simulated data are provided.

Tunnel diode nonlinear model for microwave circuits and active antennas

Tunnel diodes have a unique property: negative differential resistance (NDR). The integration of tunnel diodes with other electronic devices creates novel, quantum functional devices and circuits. The enhanced functionality of these devices enables design of both digital and analog circuits with reduced complexity, size and better performance. In this paper we investigate the applications of a nonlinear, large signal model of the tunnel diode. This model is used to analyze tunnel diode characteristics under external conditions such as input RF signal and termination resistance. We also discuss the application of the model to simulate quantum-MMIC circuits. VCOs, and active antennas designed using tunnel diodes show power outputs in the range of -4 to -10 dBm in the 1-2 GHz band. The DC to RF conversion efficiency is about 8% in VCOs and 16% in the antennas.

A highly linear single balanced mixer based on heterojunction interband tunneling diode

In this paper a compact and highly linear MMIC single balanced mixer based on heterojunction interband tunnel diode (HITD) technology working at 1.8 GHz, is described. The prototype consisted of a pair of HITDs biased at zero volts and a lumped element directional coupler with arbitrary impedance terminations. The salient feature of the mixer is the linearity due to the quasi square law DC characteristics exhibited by the device around zero voltage. The design techniques along with a detailed experimental validation are provided. The prototype exhibited an IIP3 power level of 17 dBm and a 1 dB compression point of 7.5 dBm.

Analysis and design of active antenna arrays

In this paper, the FDTD method is extended successfully to analyze active antennas using Z-transform method for small signal model and by a stable scheme for large signal model. The two approaches are validated by comparison with analytical impedance expression in frequency domain. Through these approaches, we analyze active antennas and antenna arrays containing tunnel diodes. Effects of various device parameters are investigated in order to find desired oscillations. Single and array active antennas are designed and tested. Experimental and simulated results are given and compared.

Active antennas incorporating tunnel diodes-large signal model approach

In this letter, a comprehensive dc and RF model of heterostructure interband tunnel diodes (HITDs) is extracted. Active antennas incorporating tunnel diodes are analyzed in the time domain using this tunnel diode model. The simulated and measured results are in good agreement in terms of oscillation frequencies of the active antennas. Phase noise of -114.67 dBc/Hz @1.0 MHz offset is achieved for injection-locked active antennas. The simulated injection locking range of a Ka band active antenna array is investigated.