Arthur Paolella

Analytical model for optically generated currents in GaAs MESFETs

The MESFET as an optically sensitive microwave element in MMICs has attracted much attention. The theoretical modeling of the device, however, needs more consideration. The authors propose an analytical model for the illuminated MESFET, complete in that all major contributions to the optical response are considered. The dependence of the response on bias conditions, the wavelength and intensity of the optical input, and the particulars of device structure, are incorporated in the model. The importance of the internal photovoltaic effect, which has not been properly modeled previously, is emphasized. The novel theoretical model is verified by experimental results. >

A double-stage injection-locked oscillator for optically fed phased array antennas

In an optically fed phased array antenna system, the microwave carrier signal is transmitted via a modulated lightwave to each active T/R (transmit/receive) module, where it must be converted back to the microwave domain. Currently, efficient optical-to-microwave conversion is extremely difficult, as the detected microwave signal is weak and noisy. A novel circuit, containing a high-gain/low-noise microwave injection-locked oscillator, has been developed to improve the interface between the optical and microwave components. The circuit utilizes two FETs and a dielectric resonator, which serves as a frequency-dependent feedback element. The circuit, designed to operate at about 8 GHz, provides significant amplitude and phase noise suppression. In addition, the circuit realization is compatible with MMIC technology. >

Optical control of a digital phase shifter

A method for the optical control of digital phase shifters which significantly reduces the number of control lines required is described. The technique uses a simple cost-effective light-emitting diode (LED) source along with a MESFET detector and an A/D converter to generate the digital phase shifter command. The approach is independent of the phase shifter operating frequency and is compatible with monolithic microwave integrated circuit (MMIC) technology and parallel optical signal processing. Experimental results are presented for the optical control of a 6-b digital phase shifter. To provide 360 degrees of phase shift, 310 mu W of optical power are required.<<ETX>>

A MMIC based injection locked oscillator for optically fed phased array antennas

A novel circuit, containing a high-gain-low-noise microwave injection-locked oscillator, has been developed to improve the interface between the optical and microwave sub-assemblies of optically fed phased array antennas. The circuit utilizes two FETs and a dielectric resonator, which serves as a frequency-dependent feedback element. The circuit provides significant amplitude and phase noise suppression and is designed to operate around 10 GHz. The circuit realization is fully compatible with MMIC (monolithic microwave integrated circuit) technology.<<ETX>>

Modeling the optical switching of MESFET's considering the external and internal photovoltaic effects

One of the aspects of the merging of microwave and optical technologies is the use of optical signals to switch electronic circuits in general and microwave circuits in particular (including MMIC). During the last decade, the feasibility of optical switching of MMICs has been demonstrated. This paper presents a novel model for the optical switching of the MESFET, which is the building block of MMICs. The model predicts the optical switching performance as a function of the optical signal parameters, the bias level, and the device physics and geometry. The results and conclusions from the theory are verified by measurements. The new model can serve as a design tool for designing an optimal MESFET for optical switching purposes. >

Optical Phase and Gain Control of a GaAs MMIC Transmit - Receive Module

This paper reports on the optical phase and gain control of a GaAs MMIC phase shifter and amplifier with applications for active phased array antennas. Phase shifts of 40 degrees were obtained with 50?w of optical power and amplifier gain was controlled 15 dB with 250?w of light intensity.

A new high-efficiency optical-microwave mixing procedure

A new high-efficiency optical-microwave mixing procedure has been developed and studied in detail. In many applications there is a need for mixing modulated lightwaves and microwaves. The new method offers many advantages providing a high mixing product in a wide frequency range. An optimum ad, justment has also been found.

Optical Phase And Gain Control Of A GaAs Mmic Transmit-Receive Module

This paper reports on the optical phase and gain control of a GaAs MMIC phase shifter and amplifier with applications for active phased array antennas. Phase shifts of 40 degrees were obtained with 50¿w of optical power and amplifier gain was controlled 15 dB with 250¿w of light intensity.

Optical gain control of a GaAs MMIC transmit-receive module compatible with optical spatial filters

A description is given of the optical gain control of a microwave amplifier which could be used in antenna beamforming applications. The challenge in developing the experimental circuit was to devise a means for the optical control of the microwave subsystem consistent with microwave monolithic integrated circuits (MMIC) technology, and compatible with optical processing and computing techniques. The experimental circuit consists of four main sections on LED with pigtail, a light-sensitive FET, a DC amplifier, and a distributed microwave amplifier. The electronic circuits are standard GaAs MMIC components which can be integrated into a single chip. A 250- mu W optical signal provided by the LED gave rise to 15 HB of gain control. The approach has several important attributes such as: it is independent of the operating frequency of the microwave components and can be extended to the millimeter range. It is compatible with GaAs MMIC fabrication processes; it can be extended to phase control circuits for pulsed applications; it has a fast response and is cost-effective because it uses a low-cost, low power LED and standard MMIC; and it is totally compatible with parallel optical processing such as spatial filters.<<ETX>>

Modelling the photoresponse of heterojunction bipolar transistors

An analytic model, which solves for the electrical and photogenerated currents in the emitter, base and collector of an HBT, is presented. Self aligned and non self-aligned devices, which have different empirical characteristics, are discussed. In the case of abrupt junctions, the model provides a correction term for the boundary conditions that account for band discontinuities. Experimental and theoretical results relating to the characteristics of the illuminated device given.