FERRITES FOR YOUR MICROSTRIP CIRCULATORS/ISOLATORS
Increasing demands in design miniaturization of high frequency applications involve the development of planar circuit technology using microstrip transmission lines resulting in the need of stripline Y-junction circulators. Military applications operating at millimeter wavelength require very high-end ferrite material at such high frequencies.
HSMAG is one of suppliers making its own material powders and this allows us in developing state of the art ferrite materials.
A planar Y-junction circulator is formed by depositing on a ferrite substrate a metallization pattern consisting of a central disc and three transmission line ports in a Y shape. The substrate is also metallized on its bottom side to form a ground plane and is bonded to a metal carrier. One permanent magnet provides the required magnetic field to induce the non-reciprocal behavior of the ferrite (gyromagnetic).
The energy in such circulator is then transmitted from one of its three ports to the adjacent while decoupling the signal from the third port where is connected a resistive termination to absorb the remaining signal. The efficiency of the transmitted power to the second port is driven by many parameters, such as the disc radius, the width of the lines, the angle between the three port lines, etc.
Losses of the transmitted power to the second port are also directly related to the insertion loss of the ferrite. It is then required to offer high-finished ferrite materials to Y- junction circulator manufacturers.
HSMAG , having a high experience in making ferrites, has developed dedicated materials and processes. Thanks to the characteristics of our product, we can offer state of the art ferrite substrates that can be used in circulators/isolators for a wide range of low or high power applications:
Very low losses: magnetic (DH, DHeff) or dielectric (Tanδ)
High saturation magnetization: 4pMs can be fitted to frequency
High power ferrites: DHk can be monitored
Thin ferrite substrate: lowest thickness 0.4 mm
Polished finishing: roughness Ra 0.1 µm*
Dimension: 2’’ x 2’’ square*
* Yttrium garnet materials (Y101 – Y918) or Dysprosium-doped series only
With increasing frequency, higher magnetization (4pMs) than garnet ones (1750~1850 Gauss maximum) is required. We suggest lithium ferrite series for higher 4pMs (≥ 2300 Gauss) and low losses (DHeff small < 10 Oe). Good power behavior may be also required, DHk can then be monitored and fitted to the application on request with these lithium ferrites (4 to 15 Oe or even more if needed).
For very high frequencies, the highest 4pMs being required, we suggest nickel zinc ferrite NZ50 (4pMs = 5000 Gauss, low losses).
In case of substrate with spinel ferrites (lithium or nickel zinc), we face more porous materials than garnet materials. Thus we intend to develop solutions for a higher density resulting in better smoothness of surface. Our goal is to propose polished substrate suitable for metal deposition and high printing definition of the lines.