Ferrite Phase Shifters Research Articles

Microwave ferrites for phase shifters

The electronically steerable phased array radars (PARs) are finding extensive use in military, communication and civilian applications. A PAR system typically comprises a regular arrangement of a large number of phase controlled radiating elements. Ferrite-based phase shifters in various designs are employed in these systems operating at frequencies above 5 GHz due to their superior power rating and insertion loss characteristics. Under DRDO’s integrated missile programme considerable success has been achieved in the country on the development of ferrite materials, phase shifters and array system.The work done at SSPL on the development of ferrite materials for both X- and C-band phase shifters is described. The effect of various substituents in the chemical composition of the lithium-titanium ferrites and of the process parameters to evolve the grades with required magnetic, electrical and microstructural properties are discussed. The investigations carried out to enhance optimally the r.f. power handling capability of the material for meeting the desired specifications of the C-band phase shifter are also given.

An accurate field matching analysis of waveguides of complex cross-sectional geometry loaded with magnetized ferrite rods

Many structures, such as ferrite phase shifters and rectangular waveguides loaded with ferrite or dielectric rods of circular cross-section are difficult to analyze. We have developed a field-matching technique capable of analysis of waveguides of complex cross-sectional geometry comprising longitudinally magnetized ferrite rods. The method has been implemented on a PC computer equipped with a Microwave i860 board. Computations of inner products by FFT resulted in three-fold increase in computational speed and two-fold reduction of computer memory required. The method provides results with high accuracy and within a reasonable computing time. Convergence properties, numerical and experimental results are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Diagnostics for real-time plasma control in PBX-M

An important issue for future tokamaks is real-time plasma control for the avoidance of magnetohydrodynamic instabilities and other applications that require detailed plasma profile and fluctuation data. Although measurements from diagnostics providing this information require significantly more processing than magnetic flux data, recent advancements could make them practical for adjusting operational settings for plasma heating and current drive systems as well as field coil currents. On the Princeton Beta Experiment-Modification (PBX-M), the lower hybrid current drive phasing can be varied during a plasma shot using digitally programmable ferrite phase shifters, and neural beam functions can be fully computer controlled. PBX-M diagnostics that may be used for control purposes include motional Stark-effect polarimetry for magnetic field pitch angle profiles, soft x-ray arrays for plasma position control and the separation of βp from li, hard x-ray detectors for energetic electron distributions, a multichannel electron cyclotron emission radiometer for ballooning mode identification, and passive plate eddy current monitors for kink stabilization. We will describe the present status of these systems on PBX-M, and discuss their suitability for feedback applications.

Ferrite-superconductor microwave phase shifters

Experimental ferrite phase shifters that utilize superconductor circuits with very low conduction losses are described. Magnetic flux is confined to a closed path, thereby avoiding deterioration of the superconducting properties that occurs when magnetic fields enter the superconductor. X-band differential phase shifters with meanderline circuits fabricated from niobium superconductors operated at 4 K have produced figures of merit exceeding 1000 deg/dB. The designs are adaptable to high-T/sub c/ superconductors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Propagation characteristic of a ferrite image guide

The propagation of electromagnetic waves in a ferrite image line was theoretically formulated. The formulation was based upon the effective permeability approach. The ferrite image line consisted of an insulating slab of ferrite with a rectangular cross section overlaid on an electrical ground plane. The ferrite was purposely magnetically biased so that FMR coincided with the band of frequencies in which propagation is allowable in the waveguide structure. Insertion loss and phase shifts of the electromagnetic wave signal was calculated as a function of frequency. We suggest that ferrite phase shifters, isolators, filters, and switches operating at the millimeters wavelength may be feasible using this guided structure.

Average power capacity of rotary-field ferrite phase shifters

The average power capacity of the phase shifter as determined by the increase in rod temperature and the maximum thermal gradient is analyzed. An equivalent circuit model for thermal analysis is developed, and its parameters are determined by RF and temperature measurements. An alternative geometry which results in significantly improved average power capacity without noticeable degradation of RF performance is described. An experimental phase shifter using the alternative technique was built and tested. Comparison with a conventional rotary-field phase shifter demonstrates the improvement achieved.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

New applications of perturbation theory to ferrite phase shifters

A perturbation formalism has been developed which treats an inhomogeneously loaded waveguide containing ferrites and dielectrics quantitatively. The treatment has been applied to single and double toroidal phase shifters and a tunable electrooptic modulator. The agreement between theory and experiment for the toroids is within a few percent over a broad bandwidth. The theory can treat the coupling to higher order modes and the analysis of the waveguide impedances.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Application of perturbation theory to toroidal ferrite phase shifters

An application of a perturbation formalism is developed to solve for the phase shift of inhomogeneously loaded waveguides containing ferrite toroids with dielectric inserts. The nonreciprocal differential phase shift is derived explicitly for single and double toroidal phase shifters and agrees with experiment over a broad band of frequencies. A formalism that can take into account the coupling of the higher-order modes to the fundamental mode by the geometrical inhomogeneities and tensor properties of the ferrite is described. It is shown that the theory can also be used to evaluate the impedances over a broad bandwidth.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modulation method of determining channel characteristics of a phase antenna array (PAA) with ferrite phaseshifters

Modulation method of determining channel characteristics of a phase antenna array (PAA) with ferrite phaseshifters

Phased array for millimeter wave frequencies

A phased array is presented at a frequency of 70 GHz, consisting of a corporate feed, ferrite phase shifters and dielectric rod antennas. Metal waveguides were utilized to construct the feed network, whereas a special dielectric waveguide structure was employed for the ferrite phase shifter and dielectric rod antenna. Beam scanning can be performed electronically controlled in the horizontal plane.

Transient analysis of ferrite phase shifters in rectangular waveguide in three‐dimensional space

AbstractNumerous nonreciprocal devices using magnetized ferrites have been developed for microwave and millimeter‐wave circuits. Further, improvement of the material characteristics and development of new device structures have been studied with a view to high‐density implementation of the devices along with the development of microwave integrated circuits. With the advances in high‐speed digital techniques studies of transient characteristics became necessary. Hence, it has become indispensable to carry out a three‐dimensional (3‐D) analysis including the coupling with other devices as well as the time response analysis including the transient characteristics in the development of the devices using ferrite.Recent advances in phase array antennas have made the analysis of the characteristics of the rectangular waveguide phase shifters important with a view toward improvement. These phase shifters have several formats such as the local loading of a waveguide with several ferrite slabs and the use of residual magnetization. This paper makes use of the spatial network method which has been demonstrated to be effective for 3‐D time‐response analysis of electromagnetic fields. This method is used for the analysis of three types of phase shifters with one and two ferrite slabs and a toroidal ferrite. It is demonstrated that the structures can be treated systematically and the validity of the method is confirmed by comparison with the analytical solution.

Propagation properties of ferromagnetic insulator guide

In order to realize new ferrite planar devices for applications at millimeter-wavelength frequencies, the authors have developed nonreciprocal ferrite devices schemes for incorporating ferromagnetic layers in dielectric insulator guide geometries. Their research program involves both the calculation and the measurement of device characteristics. For the calculation, a method of effective permeability, in which the permeability is a tensor, is introduced to characterize the ferrite material. The propagation properties of the insular guide are calculated by using a single-mode approach. The calculated results for dispersion, dielectric, and conductivity losses show resonant behavior with the application of a magnetic bias field for a guide configuration in which the ferrite replaces the insular dielectric. Ferrite phase shifters, filters, isolators, and circulators are potential applications of this guide configuration. For the experimental part of the study, wave dispersion and attenuation were measured in a purely dielectric insular guide from 26.5 to 40GHz. In addition to these experiments wave attenuation was measured as a function of magnetic bias field for the case where a hexagonal ferrite platelet was mounted on the ground plane near the insulator guide. General agreement is found between calculated and measured attenuation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Transient analysis of ferrite twin-toroid phase shifter by spatial network method

The transient characteristics of electromagnetic fields caused by changing the direction of remanent magnetisation in a twin-toroid phase shifter is simulated by the spatial network method. The time responses of the field and its instantaneous distributions are presented.

Technical memorandum: Edge mode effect in the operations of waveguide twin-slab ferrite phase shifter

The distributions of the electric and magnetic fields and power of the classic rectangular waveguide twin-slab ferrite phase shifter, with one region magnetised along the positive y-direction and the other along the negative y-d irection, are re-examined in the paper. It indicates that this type of device may quite often be phenomenologically described by a nonreciprocal edge-mode effect, rather than, as is customary, in terms of circular variables. This model may be of value in the design of practical wideband devices. The presence of counter-rotating magnetic fields at the two open faces of the ferrite region is also of note. The use of unequal oppositely magnetised sections is a possibility that has not received any attention so far.

Microwave ferrite toroidal phase shifter in grooved waveguide with reduced sizes

Ferrite toroidal phase shifters in both rectangular and ridge waveguide were studied theoretically and experimentally. The influences of various parameters on the performance of the phase shifter are calculated and discussed. Theoretical analysis shows that, with proper choice of dimensions, the phase shifter may be made very broadband and the loss of the phase shifter may be reduced 16% when compared to the case using rectangular waveguides. The phase shift versus frequency characteristics of these two models are shown graphically. The loss factors are approximately 0.8-1.0 dB/360 degrees . The experimental results are in good agreement with theory. >

A rigorous method for computation of ferrite toroidal phase shifters

Coupled-wave theory is used to calculate the performance of twin-toroidal phase shifters. Computation results show that this method is effective, rather simple, and easy to handle. In comparison with the single-toroid phase shifter, the twin-toroidal model's phase shift is considerably larger and its production is simpler. The wires carrying magnetizing currents are located in the weak microwave electric field area. Hence, their influence on the performance of the phase shifter is negligible; this also facilitates production. The loss factors of these two kinds of toroid phase shifters are about the same. Experimental results are in good agreement with theoretical analysis. On this basis, it is concluded that coupled-wave theory is a powerful method for treating electromagnetic problems of waveguides loaded with magnetized ferrites. >

Dielectric slab matched ferrite gyrator

A 180° nonreciprocal ferrite phase shifter with stepped dielectric impedance transformer sections at both ends is designed using the method of field expansion into eigenmodes. The rigorous optimisation method includes the higher-order mode interaction between the step discontinuities. The design achieves compact and simple components, as relatively thick, and consequently short, uniform ferrite slabs of standard dimensions may utilised. A computer-optimized design example provides about 180° ± 1° nonreciprocal differential phase shift between 12.2 and 12.8 GHz together with more than 24dB return loss.

Theoretical Considerations on the Use of Circularly Symmetric TE Modes for Digital Ferrite Phase Shifters (Correction)

Recently, we have become aware of increased publication activity by authors who refer to the above early paper. We felt that it is particularly timely, therefore, to inform those concerned that in the above paper a few formulas, unfortunately, are in error.

Magnetostriction insensitive dual‐mode phase shifter

AbstractThe dual‐mode phase shifter is known as a reciprocal ferrite phase shifter. However, in the dual‐mode phase shifter made of ferrite with magnetostrictive effect such as YIG for high power and low insertion loss applications, the reciprocal characteristics of the insertion phase shift is degraded when an external force is applied. This paper shows theoretically and experimentally that this nonreciprocal insertion phase shift is caused by the circumferential magnetization in the Faraday rotator known as the inverse Wiedemann effect, one of the magnetostrictive effects. The paper describes a method for constructing a dual‐mode phase shifter in which the nonreciprocal insertion phase is cancelled and summarizes the results of the trial fabrication. In the dual‐mode phase shifter cancelling the non‐reciprocal insertion phase developed for the X band application, the nonreciprocal insertion phase shift is less than 2 degrees, that is, one‐tenth that in a conventional device made of identical material.

Finite-element analysis of helical phase shifters

Wave-propagation equations of nonreciprocal cylindrical helix phase shifters are conventionally solved using mathematical functions, for which extensive tables are not easily available. The finite-element method (FEM) appears to be a comparatively easier means of solving these problems. The paper describes the application of the finite-element method to a very complex problem: a gyromagnetic medium with periodically varying spatial boundary conditions. The results of finite-element analysis of a normal, an inverted and a ferrite-embedded helix ferrite phase shifter in circular cylindrical geometry are presented. The relative effectiveness of these three phase shifters is studied to show that the differential phase shift is large in the case of the normal helix compared with the inverted helix.