These devices are critical in the switching and routing of microwave energy. Description: Southern Microwave , Inc. Description: Crane's Microwave Solutions offers a wide range of product solutions from component level devices to complex, advanced integrated microwave assemblies.
Description: -junction circulators Fabrication of very weakly and weakly magnetized microstrip circulators The final chapter explores important and continuing discrepancies between theoretical models and actual practice. For designers building circulators, isolators , and phase shifters; researchers. When you. Description: contains a wide variety of radio frequency communications systems as well as many radar and microwave communications systems.
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The frequency of natural magnetic resonance resonance at zero external magnetic field in the soft ferrites equals almost zero. With the available external fields the frequency of magnetic resonance in the soft ferrites can be tuned only to about 20 GHz. Because of that, this class of ferrites is regarded as the low-frequency materials.
The high-frequency devices usually incorporate the hard ferrites. The hard ferrites are the permanent magnets possessing a considerable residual magnetization. Therefore, once being magnetized they are capable of maintaining the magnetization even without the external magnetic field. In the microwave range the hard ferrites are usually used as self-biased high frequency ferrites. Typically, the stripline circulators are the narrow-band devices. The bandwidth here is defined as being a difference between the highest and lowest operation frequencies, at which an acceptable insertion loss and required isolation between the corresponding ports are maintained.
If the application requires a broadband operation, the circulators should incorporate the wideband matching transformers or composite ferrites see, for example, U. The composite ferrite is made in such a way that its constituent elements ferrite puck and rings are. The utilization of composite. This is achieved by selecting the size and magnetization of the external ferrite ring determined as a function of the lowest frequency of the pass band. The second ferrite is selected to have the dimensions and magnetization determined as a function of the second frequency being above the first frequency.
The third and additional ferrite elements may be selected using the same approach see, for example, U. Since a common external magnetizing system is used in this setup, all portions of a composite ferrite are magnetized in the same direction. The application of stronger magnetic fields, the utilization of sophisticated multi-ring ferrite assemblies and complicated matching transformers in order to extend the bandwidth and to increase the operational frequency, requires more space, adds to size, weight and cost. For clarity, the present invention will be described in a stripline embodiment only.
This, however, does not restrict in any way the scope of present invention, because it can also be implemented with other types of propagation lines, including the microstrip lines, waveguides and quasi-optical beams. The stripline Y-circulator according to the present invention is comprised of two composite ferrites, central junction, and of at least two ferrous plates.
Each composite ferrite represents a monolithic disk-shape body and consists of at least two regions. One of the regions is made from a soft ferrite and another one from a hard ferrite. Both soft and hard ferrite regions have substantially different resonant frequencies. The central junction having basically the Y-shape is situated between the composite ferrites.
The ferrous plates are disposed on the external faces of a ferrite-junction-ferrite structure. The hard and soft ferrite regions of the composite ferrites are the parts of a magnetic loop completed via ferrous plates. The direction of magnetization in all hard ferrite regions is the same. The hard and soft ferrite regions are magnetized in the opposite directions. The shape of the central junction is selected to match its impedance to that of the transmission line, thereby minimizing the insertion and reflection losses.
The operational bandwidth of a device incorporating this ferrite structure is selected to be between the frequencies of magnetic resonance in the soft and hard ferrites. The composite ferrites and ferrous plates in the structure are disposed symmetrically on each side of the junction in parallel relationship with each other.
The composite ferrites, each consisting of at least two ferrite portions, the soft and hard ones, have different frequencies of magnetic resonance. Both portions of a ferrite structure exhibit the gyromagnetic properties, while the hard ferrite portion possesses also the permanent magnetic properties.
The magnetic flux outgoing from the hard ferrites is trapped within a magnetic loop composed by the ferrous plates and soft ferrites. As a result, the magnetization of the soft ferrites is opposite to the magnetization in the hard ferrites. The operational bandwidth is selected to be between the frequencies of magnetic resonance in the soft and hard ferrite regions.
It is a primary object of the present invention to have a compact and lightweight structure that provides a broadband circulation action, including the frequency domain that is difficult to achieve with the conventional structures approximately from 20 to 40 GHz. It is a further object of the present invention to have a structure wherein the areas of magnetic flux creation and confinement would be the region where. The arrows show that the puck and ring areas of the composite ferrite are magnetized in the same direction. Figure shows that the area where the magnetic flux was generated is beyond the area of RF field circulation.
The arrows show that the soft and hard ferrite portions being parts of the magnetic loop are magnetized in the opposite directions. Arrows show that the soft and hard ferrite portions of the confined-flux ferrite structure have the same sense of circulation.go site
The Stripline Circulator: Theory and Practice by J. Helszajn - handweworksa.tk
The bold lines correspond to the magnetic configuration realized in a confined-flux ferrite structure according to the present invention. The dashed area is the operation range for circulator incorporating confined-flux ferrite structure according to the present invention. The upper and lower waveguide walls made from ferrous metal are touching the top and bottom faces of a composite ferrite situated in the center of a waveguide junction.
The central disc is a composite ferrite consisting of the soft and hard ferrite regions. Two ferrite plates are attached to the faces of a composite ferrite to close the magnetic loop. The entire structure is transparent to the incident quasi-optical beam. The prototype circulator has the overall dimensions of 0.
The Stripline Circulator: Theory and Practice
The description of the present invention is given in comparison with the state-of-the-art drum-like setup ferrite structure. Referring to FIG. Each of the ferrites 1 is made either of only one ferrite material or represents a composite body consisting of several regions of different ferrite materials composite ferrites consisting of two regions are shown, each region having different hatch pattern.
In a drum-like design of the prior art the magnetic field is usually created by three external magnets 2 disposed along the structure's periphery. These magnets are outside of the area where the field circulation is realized.
Stripline circulators; theory and practice.
The ferrous plates 4 , 5 extend beyond the composite ferrites to cover also the magnets 2 in order to complete the magnetic loop. With such magnetic arrangement the magnetic flux has the same direction in all areas of a composite ferrite. The resulting sense of circulation also should be the same as shown by arrows in FIG. Before the ferrite structure according to the present invention will be described, it is expedient to consider briefly the theory of circulation. According to 4 , the frequency of natural magnetic resonance resonance at zero external field depends on the strength of the effective field of magnetic anisotropy.
The anisotropy of soft ferrites is very small leading to the natural magnetic resonance at very low frequencies.
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The hard ferrites are highly anisotropic materials. Correspondingly, they displaying the natural magnetic resonance at the frequencies about 40 GHz and above.