J.H. Collins

Magnetostatic Wave Signal Processing

A novel technology for analog, real time, signal processing at GHz frequencies is described utilizing the propagation of slow magnetostatic waves in magnetically biased films of yttrium iron garnet, grown by liquid phase epitaxy on substrates of gadolinium gallium garnet. dispersion, attenuation and tunability c haracteristics of these waves are reviewed together with methods for efficient microstrip transduction, controlled tapping and realizing matched terminations. Comparisons are drawn with SAW technology in the context of available parameters and performing non- recursive transversal filtering. Basic experiments on magnetostatic wave propagation in periodic structures, comprised of either etched arrays or metal overlay arrays, both at normal and oblique incidence are described. The paper concludes with a survey of magnetostatic devices for GHz signal processing applications including bandpass filters, resonator-filter s, delay lines, o scillators and The

A Review of Current and Future Components for Electronic Warfare Receivers

This paper addresses the role of conventional and new components in passive electronic warfare (EW) receivers. The various areas of EW are defined before restricting the discussion predominantly to the radar intercept problem at microwave frequencies. The operational parameters of conventional components are then reviewed including the multiplexer; crystal video, instantaneous frequency measurement (IFM), and scanning superheterodyne receivers. The significance of modularity, digital control, and hybrid combinations of components is highlighted. A brief description follows of the operational Cutlass EW equipment. New components based on surface-acoustic waves (SAW) and acoustooptic (AO) Bragg cells are then presented and their particular importance in channelized receivers, IFMs, and microscan receivers noted. Finally, a number of conclusion5 are drawn covering likely trends in EW receivers and the need for continuing development of large-scale integrated (LSI) circuits for signal sorting and overall digital management.

Waveform Detection and Classification with SAW Cepstrum Analysis

A prototype real time cepstrum analyzer incorporating surface acoustic wave (SAW), Fourier transform processors is reported. This system offers sophisticated wideband signal processing for radar, sonar, and communications applications. Practical results demonstrate its capabilities when analyzing bandwidths in excess of 10 MHz in a few microseconds with simulated pulsed RF waveforms in the presence of multipath echoes. Pulse duration, repetition interval, and binary code length are resolved and the potential to characterize unknown chirp waveforms is briefly reported.

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.

Two-Port Magnetostatic Wave Resonators Utilizing Periodic Reflective Arrays

Two-port magnetostatic wave, surface wave resonators utilizing periodic etched groove array reflectors have been fabricated on LPE YIG and evaluated in S-band. Loaded Qs of greater than 800 have been observed with octave bandwidth tunability. Theory based on a cascaded transmission line model has shown good agreement with the experimental results. Loaded Qs approaching the material Q of >3000 appear feasible. Cascading of resonators to obtain better off-resonance isolation and complex filter function is feasible.

Generation and correlation of digitally controlled coherent frequency-hopped waveforms using surface acoustic wave devices

A digitally controlled coherent frequency synthesizer is reported which uses two surface acoustic wave chirp filters to generate frequency-hopped waveforms. Attractive features are wide bandwidth and instantaneous switching between frequencies, which are selected by an external word generator. Experimental results show waveforms which hop every 2.5 µs within a 12.5-MHz band. Phase coherence between pulses is demonstrated by correlating the waveform in a surface acoustic wave plate convolver.

Surface Wave Device Applications in Microwave Communication Systems

The application of certain prototype devices, already realized in the complementary surface acoustic wave (SAW) and magnetostatic wave (MSW) technologies, is examined in the context of analogue and digital microwave communications equipments. The specifications of Gaussian response IF bandpass filters and satellite channel multiplexing filters are detailed in the context of SAW designs. Extensions of SAW filter technology to the construction of IF remodulating modems incorporating frequency modulated oscillators and discriminators are examined. Stable SAW oscillators are also reviewed in the context of lightweight, rugged, spacequalified local oscillator drives. The application of MSW technology to the design of a group delay equalizer for millimetric waveguide long-haul digital communications equipments is surveyed. Finally, the paper addresses the design of fixed and variable delay lines realized in both technologies, and SAW code generators, for application to path-length equalization and test{ng of high data rate microwave radio relay systems, respectively.

Microwave losses in GGG

Realisation of low‐loss microwave devices using YIG grown by LPE on gadolinium gallium garnet (GGG) imposes severe constraints not only on the dielectric and magnetic losses in the YIG but also in the single crystal GGG substrate. Measurements of dielectric loss in GGG show that tan δd<2×10−4 at X‐band. In contrast, the magnetic loss in GGG is found to be both frequency and bias field dependent. At 30 GHz a full resonant absorption is observed in a cylindrical GGG resonator with a linewidth of approximately 7k Oe and ’g’ splitting factor of approximately 2. These results are consistent with broad paramagnetic resonance of the Gd3+ ion. For devices operating in X‐band the effective tan δ is thereby restricted to 10−3, whereas for devices operating at 2 GHz th eeffective tan δ is 2×10−4.

Planar microwave multipole filters using LPE YIG

YIG discs fabricated by LPE on GGG have been utilised in tunable microwave bandpass multipole filters. However, filter realisation in MIC format is complicated by conductor steps in excess of 10 μm. These result from the necessary microwave interconnections of the discrete YIG discs formed by etching the LPE YIG film. This paper describes a planar fabrication procedure which overcomes the conductor step problem without degrading the YIG properties.A photolithographically defined SiO2 mask is used to etch wells into the GGG substrate. LPE YIG is grown over the entire susbtrate to a thickness equal to the depth of the wells. The YIG outside the wells is removed by Syton polishing, leaving a planar surface with discrete YIG islands. YIG discs as thick as 50 μm, and YIG regions as narrow as 10 μm with 5 μm depth have been fabricated. Planar bandstop filters have exhibited linewidths below 1 Oe. Planar bandpass filters have shown external Q’s down to 60 at 2.8 GHz.

Tapped microwave nondispersive magnetostatic delay lines

Nondispersive magnetostatic surface wave delay lines when spatially tapped form the basis for real time signal processing at microwave frequencies. Devices have been fabricated reproduceably from narrow linewidth LPE‐YIG, spaced from a ground plane by a dielectric layer. Transduction and tapping of the magnetostatic waves was efficiently performed with fine line conductors at S‐band. Experimental performance and design limitations are discussed with particular emphasis on delay, transduction loss, propagation loss and power saturation.