J.M. Owens

Ion‐implanted magnetostatic wave reflective array filters

Ion‐implanted bars have been used in fabricating magnetostatic surface wave normal incidence reflective array filters at 3.0 GHz. A theory is presented, based on a dispersion relation derived from a four layer model, and data taken agrees well with the theory. The ion‐implanted bars provide a solution to problems previously associated with etched grooves and metal bars.

Electronically variable time delays using cascaded magnetostatic delay lines

A magnetostatic wave (MSW) variable time delay device with a phase deviation from linearity of less than 20 deg over a bandwidth of 300 MHz centered at 3 GHz has been demonstrated. The device consists of two cascaded delay lines. One delay line is biased to operate in the surface wave (MSSW) mode to provide a positive slope delay versus frequency characteristics, while the other operates in the backward volume wave (MSBVW) mode to provide a dispersive characteristic with negative slope. Both dispersions have been linearized by modifying the spacing between the propagation medium (YIG film) and the ground plane. The net device dispersion is the sum of the dispersive characteristics of the individual delay lines, and delay variability is achieved by varying the bias field of one of these components. A bias field change of 100 G will change the total delay by more than 40 ns.

’’Two‐port’’ magnetostatic wave resonators utilizing periodic metal reflective arrays

Single‐port and two‐port magnetostatic surface wave (MSSW) resonators have been demonstrated. These devices, based on etched groove array reflectors have shown high loaded Q’s (≳800) and clean resonance characteristics. A primary drawback lies in the fact that the reflective arrays must be accurately etched in the epitaxial YIG film, a complex and expensive process. This work reports the first use of etched metal reflector arrays to form resonant structures. A theoretical model is derived and applied to a two‐port model of the device. Simpler to fabricate, the structure shows Q’s of ∼600.

Magnetostatic Waves, Microwave SAW?

The continual demand for increased performance in modern communication and rader systems in terms of increased bandwidths and higher operating frequencies has led to investigation of novel techniques and technologies for analog signal processing. In particular, surface acoustic waves (SAW) have been extensively e xploited with great success to this end, but systems requiring bandwidths greater than 500 MHz and center frequencies greater than 1 GHz have pushed SAW devices near the practical physical limit of the technology. A novel technology promising increased bandwidths at higher frequencies is based on magnetostatic waves (MSW) propagating in epitaxial ferrite films such as Yttrium Iron Garnet (YIG). ploited in devices offering instantaneous bandwidths up to 2.2 GHz at microwave center frequencies from 0.5 to 20 GHz. This MSW signal processing technology, based on transversal filtering concepts used in SAW, has been under extensive investigation for the p ast 8 years. This paper will first discuss physical properties and limits o f magnetostatic waves, and consider similarities and differences with SAW. Next, the state of development of MSW technology in the United States and abroad will be summarized. Finally, some significant remaining problems for device application of MSW will be discussed followed by some projections for MSW technology limits.

Current status of magnetostatic reflective array filters

The continual demand for increased performance in modern communication and radar systems in terms of increased bandwidths and higher operating frequencies has led to investigation of novel techniques and technologies for analog signal processing. In particular, surface acoustic waves (SAW) have been extensively exploited with great success to this end, but systems requiring bandwidths greater than 500 MHz and center frequencies greater than 1 GHz have pushed SAW devices near the practical physical limit of the technology. A novel technology promising increased bandwidths at higher frequencies is based on magnetostatic waves (MSW) propagating in epitaxial films such as Yttrium Iron Garnet (YIG). These waves can be exploited in devices offering instantaneous bandwidths up to 2.2 GHz at microwave center frequencies from 0.5 to 20 GHz.MSW signal processing technology, based on transversal filtering concepts has been under extensive investigation for the past 10 years. This paper reviews the work that has been done utilizing the MSW technology in conjunction with reflective arrays to achieve practical spectral amplitude and delay modification.

GaAs MESFET simulation using PISCES with field-dependent mobility-diffusivity relation

Most conventional semiconductor device simulators, such as PISCES and BAMBI, use a constant diffusivity-to-mobility ratio modeling (linear relation). We modify PISCES to perform field-dependent diffusivity-to-mobility ratio (nonlinear relation) GaAs MESFET simulation and compare it to the constant ratio linear modeling. The results show that current overshoot and stable Gunn-domain formation occurred at a lower channel-impurity concentration for the field-dependent diffusivity-to-mobility ratio case. The transconductance and threshold voltage of a 1-µm gate-length MESFET are compared also.

Tunable Magnetostatic Surface Wave Oscillator At 4 GHz

An oscillator tunable from 1.8 GHz to 4.0 GHz has been fabricated using a Magnetostatic Surface Wave (MSSW) 2-port etched groove resonator as the frequency selective element, and a bipolar transistor amplifier for gain in the feedback loop. The theory for a resonator based oscillator is summarized, including the effect of loop gain, amplifier noise loop power, and resonator Q on oscillator noise. Noise and amplitude characteristics of the oscillator are reported over the tuning range. FM phase noise is comparable to YIG sphere oscillators and optimization should yield significant improvement.

MSSW Transversal Filters Based on Current Weighting in Narrow (10 µm) Transducers

A Magnetostatic Surface Wave, tunable bandpass filter using current weighted transducer arrays based on transversal filtering techniques has been built. A 100 MHz bandpass filter was realized with a minimum insertion loss of 15 dB and sidelobe suppression of 20 dB. The usable tunability range of the device was from 2 to 3.5 GHz.

A Ku Band MSW Delay Line

A MSW delay line operating at 14.4 GHz has been developed. The delay line has a minimum insertion loss of 15 dB and a VSWR of less than 2.0:1 across a 600 MHz bandwidth. This unit, including the biasing magnet, occupies a volume of four cubic inches and weighs less than one pound. A comparable coaxial delay line is 15 meters long, occupies 200 cubic inches and weighs 60 ounces. This paper presents the design techniques and data.

An Oblique Incidence Ion Implanted MSFVW RAF with Linear Group Delay

Ion implanted bars have been used in a MSFVW oblique incidence reflective array linear delay filter at 3 GHz. Theory and synthesis techniques are presented based on a four layer complex dispersion relation and the impulse reflection model.