Magnetostatic Wave Delay Line Research Articles

Microwave Magnetics and Considerations for Systems Design

The adoption of non-linear magnetic devices in Radio Frequency (RF) systems has been relatively slow due to their unique characteristics that do not lend themselves well to traditional design tools and methodologies. Herein we present the practical considerations in employing such devices in modern RF system design with an emphasis on realizable improvements in performance and adaptability in addition to the common design methodology that has been adopted to account for their unique behavior. Specifically, this article begins by presenting how a standalone nonlinear device such as a Frequency Selective Limiter (FSL) can enable a higher-level subsystem such as the Frequency Selective Canceller (FSC). This discussion sheds light on the importance of characterizing the behavior of an FSL and how this behavior is different from other, more traditional RF components such as a Pin Diode Limiter, as explained in the second part of the article. Lastly, a Magnetostatic Wave (MSW) delay line that leverages the recent advancements in non-linear magnetic device design is introduced in order to provide an attractive alternative to traditional delay lines. A more complete understanding of system-level performance benefits and device-level functionality will undoubtedly facilitate the widescale deployment of nonlinear magnetic devices to help mitigate spectrum congestion challenges faced by modern and future RF systems.

Active magnetostatic wave delay line for microwave signals

Summary form only given. Three variants of a new active magnetostatic wave (MSW) delay line for pulsed microwave signals providing controlled delay times of up to 1 /spl mu/s has been developed and experimentally tested. The proposed active delay line consists of an input and output transducers, yttrium-iron garnet (YIG) film waveguide (where the microwave MSW pulse is propagating), and an open dielectric resonator which is situated between the transducers and is used to supply electromagnetic pumping pulses having frequency (9.4 GHz) twice as large as the carrier frequency of the input microwave radio-pulse (4.7 GHz). In contrast with the usual passive MSW delay line, where characteristics are controlled by the external bias magnetic field, the characteristics of the developed active delay line are controlled by the amplitude, duration, and the moment of application of the pumping pulse. While traditional passive MSW delay lines have substantial insertion losses proportional to the delay time (/spl sim/ 80 dB//spl mu/s), in the developed active delay line the amplitude of the output delayed pulse can be kept constant in the whole interval of possible time delays.

Electronically tunable nondispersive magnetostaticwave delay line

An electronically tunable, nondispersive magnetostatic wave delay line consisting of cascaded magnetostatic backward volume waves and magnetostatic surface waves delay lines has been designed and realised. The distinguishing feature of the device is a wide continuously tunable time delay range of ±30% with the central value of 58 ns. An obtained bandwidth for constant time delay is ~300 MHz at a 3.15 GHz centre frequency. A deviation from constant delay is < ±5%.

Suppression of microwave magnetic envelope solitons by continuous wave magnetostatic wave signals

The influence of continuous wave (cw) magnetostatic wave signals on microwave magnetic envelope soliton pulse formation and propagation in magnetic films has been examined. Pulsed and cw microwave signals were applied to the input of a single crystal yttrium–iron–garnet film magnetostatic wave delay line. The nominal operating frequency was 4.8 GHz. The pulse signals served to form solitons with no cw power present. Under suitable conditions, the cw signal served to inhibit or eliminate the soliton formation and propagation. The suppression effect was measured as a function of the cw signal frequency and power. The suppression is maximized when the cw signal frequency coincides with the pulse carrier frequency. At this frequency, an input cw power of 80 mW is sufficient to suppress completely a soliton pulse formed from a 10 ns wide, 500 mW peak power input pulse.

Excitation of bright and dark microwave magnetic envelope solitons in a resonant ring

The excitation of both bright and dark microwave magnetic envelope solitons has been realized for one and the same resonant ring containing a yttrium–iron–garnet film magnetostatic wave (MSW) delay line. The resonant ring modifies the MSW character to produce a series of frequency intervals with alternating regions of positive and negative dispersion. These alternating regions support bright and dark soliton production, respectively.

Active narrowband magnetostatic wave filter

An active passband microwave filter consisting of a magnetostatic wave (MSW) delay line and microwave amplifier has been developed and tested. A narrow passband of 120 kHz was obtained at the S/C-band corresponding to a quality factor Q of ~40000. The frequency response characteristics are presented.

Active magnetostatic wave delay line

Two configurations for an active microwave delay line with feedback to improve the loss per unit delay time have been made and characterized. The lines utilized thin yttrium iron garnet (YIG) film, magnetostatic wave (MSW) passive elements, a microwave amplifier, and a variable attenuator connected in a feedback loop. The two delay line setups used a surface wave (MSSW) configuration with a single MG element and a nondispersive configuration with MSSW and backward volume wave (MSBVW) delay lines in series. For each setup, a sequence of delayed pulses at the output is observed when a single microwave pulse is fed to the input. The one-pass delay time T of the pulse through the MSW delay line and the number n of circulations in the feedback loop defines the total delay time nT for the nth pulse. The feedback resulted in a reduction in the output pulse decay rate and longer useful delay times. For a passive delay line with no feedback, typical values of the loss p.u. delay time L and useful delay time (nT)/sub U/ were -110 dB//spl mu/s and 0.1-0.2 /spl mu/s, respectively. With feedback for the MSSW delay line, a 4.5-GHz operating frequency, and 40 ns input pulses, L and (nT)/sub U/ were -19 dB//spl mu/s and 0.6 /spl mu/s, respectively. Feedback with the nondispersive delay line gave L and (nT)/sub U/ values of -12 dB//spl mu/s and 3 /spl mu/S, respectively, for 4.5-GHz, 40-ns input pulses.

Phase properties of microwave magnetic envelope dark solitons in yttrium iron garnet thin films (abstract)

Although microwave magnetic envelope (MME) solitons in thin yttrium iron garnet (YIG) films have been studied extensively, only recently have dark MME solitons been observed. For a single dark soliton, one has a carrier phase change of 180°. Reference 1 indicated such a change. However, the overall phase change for a given dark pulse experiment should be 0°. The objective of this work was to examine phase profiles in detail for the dark soliton experiment. The results show that both of the above expectations are, in fact, satisfied. The 5 GHz measurements were done with a magnetostatic wave delay line structure with a long and narrow 7.2 μm thick single crystal YIG film oriented in the surface wave configuration. A GaAs microwave switch produced 300 ns long bright pulses separated by a dark pulse with a width in the 15 ns range. The input power was 0.002–1.0 W. The output signal showed two main dark pulse features, independent of power level. At low powers, the changes in phase across both features were small. With increasing power, the phase change across the first feature showed a rapid increase while the phase change for the second feature remained small. The phase change for the first feature saturated at a large value, on the order of 200°, relative to the phase change at low power. The phase change over the entire profile was always 0°. These results show: (1) There are significant phase changes at both low and high powers in the dark pulse experiment. (2) The phase change for a dark soliton must take into account the background phase change at lower powers. (3) Only the main dark pulse feature in the output profile exhibits single dark soliton characteristics through a clearly resolved phase saturation at 180°. (4) These thresholds are on the order of 10 mW for typical strip line transducer structures, compared to 100 mW or so for bright solitons.

Nonlinear propagation of short microwave pulses in magnetostatic volume wave delay lines

The conditions for the excitation of volume wave solitons and self induced transparency in magnetostatic volume wave (MSW) delay lines will be discussed and compared with experimental results. The dispersion and nonlinearity characteristics of compact device structures will be analytically derived in the one and two ground plane configurations, and their influence on the onset of a solitonic behavior will be analyzed in some detail. >

Backward volume wave solitons in a yttrium iron garnet film (invited) (abstract)

Solitons are nonlinear propagating wave pulses that preserve their shape without spreading. Recently, microwave envelope solitons have been observed in thin yttrium iron garnet (YIG) films for magnetostatic surface wave and forward volume wave configurations. In this work, we report the first observation of microwave envelope of magnetostatic backward volume waves (MSBVW) for an in-plane magnetized YIG film with waves propagating parallel to the magnetization direction. Both soliton profiles and the nonlinear peak power response were observed. The experiments were conducted using a microstrip magnetostatic wave delay line structure. A single crystal YIG film of 7.2 μm thickness, 2 mm×15 mm in size, and with unpinned surface spins was magnetized in-plane by a static external field of 1343 Oe along the long 15 mm edge. The 10 GHz ferromagnetic resonance linewidth of the film was 0.6 Oe. Square microwave pulses with pulse widths from 2 to 200 ns and a carrier frequency of 5.78 GHz were launched parallel to the field through a microstrip antenna. The output signal was received by a second microstrip antenna placed 4 mm downstream and analyzed in the time domain with a microwave transition analyzer. Envelope soliton behavior evident from the time resolved waveforms was observed for various input-power/pulse-width combinations. At relatively low power levels, one sees a broad output signal with a peak power increasing linearly with the input power. As the input power is increased above some threshold, a sharp soliton pulse emerges and the peak power increases more rapidly with input power than in the low power regime. The threshold varies with pulse width, as expected for solitons. A further increase of the input power produces multiple soliton profiles and a corresponding drop in the peak power. These results clearly demonstrate the existence of MSBVW solitons in YIG films. Dr. J. D. Adam of Westinghouse is acknowledged for providing the YIG films. This work was supported in part by the National Science Foundation, Grant No. DMR-8921761 and by the U. S. Army Research Office, Grant No. DAAL03-91-G-0327.

End reflections and triple transit contribution to the band shape of magnetostatic volume wave delay lines

An analysis of the signal reflections originating at the garnet film ends and of the triple transit between the microstrip transducers in magnetostatic volume wave delay lines has been performed. The influence of those effects on the band shape and on the insertion loss of magnetostatic wave devices has been inferred and compared with experimental results. In this framework, the possible utilization of the reflections for filterbank applications is also proposed.

Multimode oscillation and mode locking of magnetostatic wave delay line oscillator

Multimode oscillation at up to 15 frequencies and a modelocking regime in a magnetostatic backward volume wave delay line oscillator have been realised. At 3.53GHz central frequency the mode-locked oscillator generated 7.10 ns long coherent pulses with 53 ns pulse repetition period.

Design of tunable magnetostatic volume wave filters with dispersion and bandwidth control

The possibility of controlling the bandwidth and the dispersion of a tunable magnetostatic volume wave (MSVW) delay line filter based on yttrium-iron-garnet (YIG) films is demonstrated. The simulation has been performed on a MSW filter consisting of two delay lines in cascade having opposite dispersion properties: a backward volume wave delay line and a forward volume wave one. The filter can be used effectively in the microwave frequency range for bandwidths between 20 MHz and 200 MHz, with the center frequency tunable with the DC magnetic bias.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thin‐film permanent magnet requirements for magnetic devices in MMIC

AbstractThe use of sputtered thin‐film permanent magnets for biasing microwave devices in planar geometries compatible with monolithic integration is considered. Possible geometries are presented for biasing a reciprocal microstrip phaser at 7 GHz, a stripline circulator at 15 GHz, and a magnetostatic wave delay line at 3 GHz. Yttrium iron garnet (YIG) is assumed to be the ferrite used in each of these devices. It is concluded that the in‐plane magnetization orientation is more useful than normal magnetization, and thick films (100‐150 μm) are needed with high magnetization ( &gt; 16 kG) and moderate coercivity ( &gt; 2 kOe). Below‐resonance devices are preferable because of their modest field requirements and tolerance to bias field inhomogeneities.

Oscillators using magnetostatic-wave active tapped delay lines

A novel oscillator that combines a magnetostatic wave (MSW) tapped delay line with GaAs monolithic microwave integrated circuits has been fabricated. This oscillator incorporates an external feedback loop that is extremely short and provides multiple outputs delayed in time by the MSW delay line. The oscillator is tunable from 2.76 to 2.95 GHz, and the 3-dB bandwidth of the oscillation is approximately 10 kHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Insertion loss of electronically variable magnetostatic wave delay lines

An investigation is presented of insertion loss and constant variable delays in electronically variable magnetostatic-volume-wave delay lines. The delay line has a conductor-dielectric-YIG-dielectric-conductor structure. Variable delays up to 300 MHz bandwidth have been obtained in a single volume-wave delay line by adjusting the direction and magnitude of the biasing DC magnetic field in a plane containing the normal to the YIG film and the direction of wave propagation. Insertion loss as a function of frequency has been obtained for different biasing field angles and also for the angles corresponding to variable constant delays. Good agreement between theoretically obtained insertion loss and experimental results is found. Electronically variable magnetostatic-wave delay lines have promising applications in broadband phased-array antennas at 1-20 GHz. >

Second-order term effect on the dispersion characteristics of a magnetostatic delay line

This work reanalyzes the methods of calculation of the dispersion characteristics of a dispersive magnetostatic wave delay line. It turns out that the analytical approach, commonly developed in a first-order approximation, leads to erroneous results when exploited to derive the variation of the group velocity as a function of the wave vector k (or of the frequency), particularly for k values lower than 100–200 cm−1. To get a more accurate response, higher-order terms have been introduced in the analysis of the dispersion relation. To describe their effect, the inferred analytical results are compared to the numerical ones and to the experimental responses of a magnetostatic wave delay line. Furthermore, the method has been exploited to evaluate the power threshold levels (Pthr) in the excitation of magnetostatic solitons. It gives the correct order of magnitude of values when compared to the experimental ones.

Loss reduction of the magnetostatic forward volume wave delay line using the YIG film

AbstractThis paper describes from the experimental viewpoint the group delay characteristics, particularly, loss characteristic (both propagation loss and transducer conversion loss) of the magnetostatic forward volume wave in a YIG film nonuniformly magnetized with a conical pole piece. The maximum time delay of 3 m̈s has been observed at 4 GHz and the propagation loss has been found to be 15 dB/m̈s. It has been found that the delay time minimizing the loss increases with the degree of nonuniformity of the magnetic field. A theoretical study has been made for the experimental results. It is assumed that a lens‐like medium is formed in a YIG film by means of the nonuniform magnetic field. From the lens theory, the focal length for the magnetostatic wave beam has been obtained and the focal length is estimated as a function of the delay and the degree of nonuniformity of the magnetic field. It is concluded that the focal point of the magnetostatic wave beam is formed on the receiving transducer if the loss is minimum, and that the loss is related mainly to the conversion loss.

Suppression of higher-order thickness modes in magnetostatic forward volume wave delay lines

This paper presents a theoretical study of suppression of undesired higher-order thickness modes excited in magnetostatic forward volume delay lines. This can be done by using the exciting and receiving transducers deposited directly on the top of an yttrium iron garnet film. Though this geometry has been used before, this paper describes more detailed investigation. Numerical results obtained are quite useful and encouraging. The magnetostatic volume wave delay lines have potential applications in microwave signal processing with larger operating bandwidth directly at microwave frequencies.

Low-loss magnetostatic wave delay line operating at 14.4 GHz

A magnetostatic wave (MSW) delay line operating across a 600 MHz bandwidth at 14.4 GHz has been developed. The delay line has a maximum insertion loss of 21 dB, a minimum delay of 72 ns and a VSWR of less than 2.0:1, while occupying a volume of 4 in 3 (166.5 cm3). This unit weighs less than 16 oz (454 g).