A. Sailer

Characteristics of Ka band waveguide using electromagnetic crystal sidewalls

Electromagnetic crystal structures have been used as sidewalls in special waveguides for the frequency range 30 to 40 GHz. They have the effect of substituting high impedance surfaces in place of the normal conducting metal sidewalls. The objectives in so doing are to obtain uniform electric field across the width of the waveguide and to force the wave in the guide to adopt the nature of a TEM wave. The measured insertion loss of Ka band waveguides is found to be low. The dependence of transmission phase on the center frequency of sidewall resonance has been measured and indicates that tunable sidewall resonance will provide simple and low loss phase shifting systems.

A Ka-band monolithic quasi-optic amplifier

Recent advances in the development of a Ka-band quasi-optic amplifier are reported. The amplifier consists of a two-dimensional array of PHEMT power amplifiers, each of which is coupled to individual input and output slot antennas. The array of 112 amplifiers (49 mm total gate periphery) is organized into pairs operating in push-pull between a 7/spl times/8 array of input slots and an 8/spl times/8 array of orthogonal output slots. The total chip size is 12.8 mm by 13.4 mm and has a thickness of 75 /spl mu/m. It is fabricated with standard MMIC processing techniques. The amplifier provided gain from 37.5 GHz to 39.5 GHz with a peak gain approaching 9 dB at 38.6 GHz. The maximum measured output power is 29 dBm.

A GaAs BiFET LSI technology

A GaAs BiFET LSI technology has been successfully developed for low power, mixed mode communication circuit applications. The direct placement of the FET on the HBT emitter cap layer simplifies the device epitaxial growth and process integration. High integration levels and functional circuit yield have been achieved. Excellent HBT and FET characteristics have been produced with the noise figure of the FETs comparable to those of traditional MESFETs, enabling them to perform well in front end receiver applications. Through this technology, several LSI circuits, including 32-bit by 2-bit shift registers and a single-chip DRFM have been successfully demonstrated.

A high-power W-band quasi-optical frequency tripler

A monolithic W-band quasi-optical array consisting of 196 heterostructure barrier varactors mounted in a waveguide has produced 684 mW of CW output power with a peak conversion efficiency of 11.3% at 93 GHz. The compact 32 mm/sup 2/ array was fabricated using two-barrier twin-mesa varactors with InGaAs/InAlAs/AlAs barriers on a lattice-matched InP substrate. Device measurements demonstrate low series resistance and high cutoff frequency. Simulations show even greater output power and efficiency can be achieved by increasing the device density in the array.

Tunable millimeter wave band pass filter using electromagnetic crystal sidewalls

Electromagnetic crystal (EMXT) structures are used as the waveguide sidewalls of a Ka-band waveguide cavity. With InP heterobarrier varactors (HBV) embedded, the EMXT structure acts as an electronically tunable surface impedance in place of the normal conducting metal sidewalls. By controlling and varying the sidewall impedance with a dc voltage, the EMXT waveguide propagation constant is varied and the effective electrical length of the cavity changed. The center of the pass band was tuned 31.6 GHz by varying the varactor bias from 0 to 10V. It is demonstrated that the guide width can play a significant role in controlling tuning range. Good agreement between measured and simulated band pass response was obtained.

7.5-14-GHz CE HBT MMIC linear power amplifier

A common-emitter (CE) AlGaAs-GaAs HBT MMIC amplifier was made to operate in X-band. 1-W CW output power was achieved in saturated power operation from 7.5 to 12 GHz. In class A linear power operation, it provides 26-dBm CW power. The amplifier shows low two-tone intermodulation distortion: better than -20 dBc IM/sub 3/ at 1-dB compression point throughout the 7.5-14-GHz bandwidth. The low third-order intermodulation distortion is a direct result of the excellent linear power performance of the CE AlGaAs-GaAs HBT. The combination of good efficiency, low third-order intermodulation distortion, and broad bandwidth in this MMIC amplifier clearly demonstrates the potential of the CE HBT in communication transmitter applications.<<ETX>>

Direct parametric extraction of 1/f noise source magnitude and physical location from baseband spectra in HBTs

This work describes a novel equivalent circuit representation for the modeling of low frequency 1/f noise in Heterojunction Bipolar Transistors (HBTs), and is presented as part of an extraction procedure which combines direct calculation of the HBT equivalent circuit from S-parameters, and separate measurement of the base and collector noise voltage spectra to determine the magnitude and physical location of the dominant intrinsic 1/f noise sources within the device.

A predictive model describing the upconversion of 1/f noise into AM sideband noise in HBTs

An analysis of AM noise in AlGaAs-GaAs HBT amplifiers is presented. A predictive model is introduced which allows calculation of AM noise sideband power alongside carrier signals in HBT amplifers as a result of the upconversion of low frequency noise. These sidebands are an unavoidable result of the nonlinear components in microwave oscillators and power amplifiers which causes upconversion of intrinsic low frequency 1/f noise into amplitude modulated (AM) and phase modulated (PM) sidebands about the carrier. AM and PM sidebands degrade the spectral purity of the carrier which ultimately limits system performance in communication systems. Many works have described the upconversion process in microwave oscillators with its dominant phase noise, but less attention has been paid to the AM noise of power amplifiers. This work presents the theory of such noise in AlGaAs-GaAs HBT amplification and details a predictive model that allows calculation of AM noise sidebands for any HBT device.

A PHEMT based monolithic plane wave amplifier for 42 GHz

We report the design and operation of a monolithic plane wave PHEMT amplifier operating at millimeter wave frequencies. The array is made up of input slot antennas (5/spl times/7 array) and output patch antennas (4/spl times/8 array) polarized in orthogonal directions. An array of PHEMT amplifiers (7/spl times/8) placed between the two antennas amplifies and reradiates the input signal. The amplifier was placed in an oversized waveguide in order to avoid diffraction losses of a free space system. Gain of the amplifier was 3 dB at 42 GHz without any corrections for internal fixture losses. The amplifier results correlate well with computer model predictions of the antenna structures. These results prove the feasibility as well as the manufacturability of this approach.

Near field magnetic communications for helmet-mounted display applications

Helmet-mounted displays need a data feed that is typically provided by a cable or RF wireless data link to an external computer. In defense applications these solutions are problematic: a cable gets in the way and restricts use and emergency egress, while an RF wireless link can be detected at some distance giving away position and is susceptible to jamming. What is required is an alternative wireless technology that is low power, extremely localized and difficult to detect or jam. Near field magnetic communications is one possible alternative to RF communications that may fulfill these needs. This technology uses a time varying magnetic field to carry information, and is only useable over small distances of order six feet. This is expected to have significant advantages for particular applications: notably power requirements and security compared with RF wireless links. The power stored in a magnetic field falls off as 1/r6, compared with 1/r2 for RF, which means that all the power is localized around the transmitter. By having a physically small communications region around each platform or user, a large bandwidth can be guaranteed by allowing the reuse of the frequency spectrum outside the immediate vicinity. It also confers security on the data-link, as the signal is undetectable beyond the short range of the system.