Ferrite Coupled Line Circulators Research Articles

Design and Measurement of Nonuniform Ferrite Coupled Line Circulator

Nonuniform ferrite coupled line constructed by placing section of corrugated coupled lines on longitudinally magnetized ferrite substrates is investigated. Unlike the usual uniform ferrite coupled line, the proposed nonuniform ferrite coupled line is corrugated with different cosinusoidal contours on the coupling slots. Compared with a standard ferrite coupled line designed at 7.6 GHz, the nonuniform ferrite coupled line based on the same ferrite substrate and of the same dimension is found to operate at a higher frequency. The center frequency of operation is up shifted by about 1 GHz. It is also found that the nonuniform ferrite coupled line has a broader bandwidth. The proposed nonuniform ferrite coupled line operates at the center frequency of 8.6 GHz with a bandwidth of about 26.7%, while the standard uniform ferrite coupled line operates at 7.6 GHz with a bandwidth of 14.5%. Two 3-port circulators are built by adding simple T-junctions to the uniform and the nonuniform ferrite coupled lines respectively. The measurements confirm the up shift in center frequency and the broadening in operating bandwidth of the nonuniform ferrite coupled line circulator.

Scattering-matrix analysis of ferrite-coupled line circulator

The conditions for the optimal non-reciprocal operation of longitudinally magnetised ferrite-coupled line (FCL) are obtained for the first time from the scattering-matrix treatment, and the necessary conditions for the multicomponent reciprocal network joint with a FCL section to be a circulator are specified. Using these optimal conditions, the minimum length of the FCL is also found. A self-biasing circulator with the minimum length of FCL at millimetre-wave frequency is reported and its scattering characteristics are simulated and discussed.

Microstrip four-port circulator using a ferrite coupled line section

This paper describes an alternative configuration of a four-port circulator realized in a microstrip ferrite coupled line technology. The proposed fully planar device employs two three-port circulators consisting of a ferrite coupled line junction and T junction. Both circulators are connected through the same arm, hence, the problem of anti-parallel magnetization met in this type of circulators is avoided without the increase of the device width. The simulated and experimental results check feasibility of such device. The constructed four-port ferrite coupled line circulator is applied as a double isolator operating in the frequency band from 9 to 18 GHz, with average insertion losses - 3 dB and isolation better than - 20 dB .

Ferrite coupled-line circulator with reduced length

A method to design a circulator based on a ferrite coupled line (FCL) with reduced length is presented. This is achieved by appropriate matching networks. Using ferrite perturbation theory, we derive closed-form expressions for the required matching impedances and the resulting bandwidth of the matched device. Based on this analysis, a realistic design for a stripline FCL circulator is obtained, whose length is shorted by a factor of three. A microstrip FCL circulator with only half of the optimum length is designed and fabricated. Both simulation data and measurement results clearly demonstrate the feasibility of a circulator based on an FCL with reduced length.

Novel Folding Technique for Planar Ferrite-Coupled-Line Circulators

A novel folding technique for a longitudinally magnetized ferrite-coupled-line (FCL) section is reported in this paper. The results from Ansoft HFSS simulations of a single-folded structure are presented for a 17-GHz folded stripline FCL section and the measurements on the 17-GHz folded stripline three-port FCL circulator confirm the folding concept and demonstrate that nonreciprocal behavior is retained.

Broad-Band Three-Port and Four-Port Stripline Ferrite Coupled Line Circulators

The broad-band characteristics of a stripline ferrite coupled line (FCL) section are verified through measurements, for the first time. Subsequent simulations and measurements on a 17-GHz three-port circulator employing a stripline FCL section shows a 65% bandwidth, from 11.5 to 22.5 GHz. A four-port FCL circulator, which is a modification of that proposed earlier by Masur and Mrozowski and Queck and Davis is also realized by connecting the two lines together at the center of the FCL section, i.e. within the ferrite region. Compared to the four-port circulator consisting of an FCL section and a hybrid coupler, it has the advantage of much broader bandwidth. Simulations and measurements confirm its circulating behavior and also show a similar 65% bandwidth, from 12.0 to 23.5 GHz.

Theoretical and experimental treatment of a microstrip coupled ferrite line circulator

The paper describes a microstrip ferrite coupled line (FCL) junction practically applied as a section of the FCL circulator. Improvements over the earlier models include realisation of the microstrip circuit on the dielectric substrate and placing a ferrite overlay on top of the coupled line of the FCL section. Simulation and measurements show the operation bandwidth from 10 to 15 GHz with isolation and reflection losses better than 10 dB and average insertion losses <2.5 dB.

Performance of stripline-type ferrite coupled line circulators

The normal-mode approach is used to design stripline-type ferrite coupled line circulators with alumina as a substrate and ferrite as a superstrate. The measurements that are taken clearly demonstrate the nonreciprocal behavior of these devices, with an average insertion loss of 5 dB and an isolation of −12 dB. It is found that the three-port circulator has a broader bandwidth (9–14 GHz) than that of the four-port circulator (9–12 GHz), and the hybrid coupler has been identified as the bottleneck in the latter. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 173–179, 2003.

Self-biased hexagonal ferrite coupled line circulators

The simulated performance for novel hexagonal FCL circulators is presented for the first time. Compared to conventional FCL circulators, these structures do not require external biasing and have the advantages of smaller size and lower conductor and dielectric loss. Simulations show that the size decreases as the value of 4πMeff of the hexaferrite increases.

Design and measurement of microstrip ferrite coupled line circulators

The design of microstrip ferrite coupled line (MFCL) circulators using normal mode theory and the first proof-of-principle experiments are described. The longitudinally magnetized ferrite slab is positioned on top of a pair of microstrip lines to form the FCL and this is used with a T-junction and a novel hybrid coupler to form a three-port and a four-port circulator, respectively. The results show MFCL circulator behavior for the first time, and impedance levels and discontinuities are discussed. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 121–130, 2001