Abstract-A compact microstrip resonator based on the interdigital structure is proposed. The resonator has several times higher unloaded quality factor compared to similar resonators presented previously and can even reach the Q-factor of a regular λ/4 resonator. The size of the resonator can be significantly reduced with a substantial increase in quality factor by incrementing the number of fingers in the interdigital structure. In addition, for each gap between the fingers, there exist an optimal number of fingers that correspond to the maximum Q-factor. An extension of the upper stopband for a bandpass filter designed using the resonator can be achieved by the interconnection of the fingers in each of the comb structures. The simulation results are proven by fabricated resonators and a fourpole bandpass filter. For the central frequency of 2000 MHz and 16.2% fractional bandwidth, the lateral size of the filter is only 11.5 mm × 3.8 mm for alumina substrate (eps = 9.8). The filter has an upper stopband up to 5.8f 0 at the level −40 dB.
This paper presents a new type of magnetically tunable phase shifter. The shifter has the structure of microstrip bandpass filter on a substrate containing magnetic material whose magnetic permeability is controlled by a magnetic field due to ferromagnetic resonance. The phase shifter's operation is based on the fact that phase shift in a bandpass filter changes with tuning of its central frequency. Two types of devices were designed and fabricated for the UHF band. One of them has a five-layer NiFe film as an active medium and demonstrates a figure of merit of 40°/dB achieved already at 20 Oe of the controlling magnetic field in 10% of the relative operational bandwidth. The second device with YIG ferrite as an active media gave 360° tunable phase shift in 5% operational bandwidth that corresponds to the figure of merit of 150°/dB (3.1°/dB*Oe).
Abstract-This paper proposes a miniature microwave bandpass filter. It comprises quasi-lumped suspended substrate stripline resonators of a new type. Their common substrate consists of two contiguous dielectric layers. Every resonator in the filter has three parallel strip conductors. Two of them are placed on the outer substrate surfaces and the rest is placed inside the substrate. The filter of the sixth order was designed with the use of special optimization rules that are universal for all resonator filters. The substrate of the fabricated filter was made of RT/Duroid 5880 (ε r = 2.2, tan δ = 0.002) with thickness of 0.127 mm. It has dimensions of 12 mm × 45.5 mm. The measured passband has a center frequency of 1.01 GHz, 3-dB fractional bandwidth of 11%, and minimum insertion loss of 1.4 dB. The 100-dB upper stopband extends up to 10.5 GHz.
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