M. Ye. Ilchenko

Coupling coefficient of quarter-wave resonators as a function of parameters of comb stripline filters

The relationship of the coupling coefficient of quarter-wave resonators operating on the main resonance frequency f0 as a function of different parameters of comb filters made of sections of symmetric striplines has been analyzed. It has been found out that the coupling coefficient increases with the rise of relative dielectric permittivity of striplines, their thickness and the resonance frequency. The measured characteristics of the stripline 4-resonator comb filter with central frequency f0 = 2.4 GHz built on dielectric material with εr = 9.7 are also presented.

Coupling coefficients of step-impedance resonators in stripeline band-pass filters of array type

There are researched specificities of electromagnetic coupling coefficients at main and higher resonance frequencies between step-impedance resonators, fabricated from symmetric stripe transmission lines with open ends. It is shown, modification of step resonators parameters can result in modification of the coupling coefficient at main resonance frequency in wide range, that allows to realize band-pass filters of array type. It is stated in case of several values of parameters of stripe resonators their coupling coefficients values at frequencies higher than main one are zero. It is proposed a new method of expansion of suppressed frequency band of pass-band filters of array type, which is based on suppression of the first parasitic pass band due to zero coupling coefficient.

Stripline bandpass filters with step-impedance resonators

Research results for stripline bandpass filters with step-impedance resonators formed on Al2O3 (Alumina, polycor) and operating in the frequency band 1500–2500 MHz are presented in this article. Use of step-impedance resonators breaks repetition factor in frequency positioning of passbands in such filters. This allows suppressing harmonics of output signal in transmitters and widening stopband for parasitic signals in receivers.

Stripe delay filters

There are considered constructions of microsized stripe delay filters, which are realized on a basis of ceramic materials with high dielectric permittivity. Delay time of non-minimal phase filters is 7–12 ns at frequencies of 1900 MHz with relative bandwidth of 3.6–3.85%. Filters dimensions are comparable with ones used in portable communication devices. Dimensions of researched three-resonator filter at frequency of 1900 MHz are 8.4×5×2mmwith material dielectric permittivity εr = 92, and 5-resonator filter ones are 9.2×8.6×2 mm. Filters are different from traditional delay filters. Two filters of considered ones contain odd resonator number and the third one contains four resonators and it has two cross couplings. The basis of the filters is amount of step-impedance stripe resonators pairs located close to each others whose electromagnetic coupling behavior is capacitive. There are represented the results of frequency characteristics simulation for different delay filters.

Microstrip U-shaped resonators

Influence analysis of U-shaped microstrip resonators’ parameters and parameters of dielectric substrate on resonant frequencies and unloaded quality-factor of resonators is conducted. Three kinds of U-shaped resonators are considered which differ in operation modes at the resonator’s ends: short-circuit or no-load. It is revealed that in cases of small spacing between the arms of U-shaped resonators distribution of their resonant frequencies significantly differs from the corresponding quarter-wavelength or half-wavelength resonators and leads to decreased stop-band in pass-band filters based on them. Experimental research shows that decreasing the spacing between the arms of U-shaped resonators leads to decrease in quality-factor by 20–30%. Experimental samples were manufactured on substrates with ɛr = 92 and ɛr = 38.

Problems and Aspects Regarding the Creation of Terrestrial Digital TV Networks in Ukraine

Considered in this paper is the introduction of digital broadcasting in Ukraine taking into account foreign experience and development of microwave terrestrial, satellite and cable networks. Results of successive operation of DVB-T experimental zone within 470-862 GHz in Kiev and Odessa are presented. It is necessary to create hi-tech products, first of all universal tuners and transmitting devices using the achievements in the fields of microwave technology and microelectronics. Peculiarities and aspects are discussed regarding the introduction of wideband wireless technologies on the basis of existing UMDS systems and UWDS within 10150-10300 MHz, 10500-10600 MHz and 11700-12500 MHz. Results of microwave digital TV broadcasting and data transmission are presented within the frameworks of UWDS project in the Crimea on the basis of MITRIS technologies.

Interaction Features of Stepped-Impedance Stripline Resonators in Comb Filters

Mixed coefficients of coupling between the closely spaced stepped-impedance resonators in comb filters of stripline design have been investigated. Transmission zeros at frequencies fzi correspond to mixed coupling coefficients ki. These zeros can be moved with respect to the filter passband central frequency f0 by modifying the shape of resonators. It was proved that the reduction of gap between resonators made it possible to locate frequencies fz and f0 closer to one another. The existing restrictions on the minimal value of gap between resonators limit the degree of proximity between fz and f0. The N-resonator stripline comb filters with mixed coupling can have N−1 transmission zeros. The absence of cross-coupling links in stripline filters simplifies their construction. It has been established that the thickness of central conductors of stripline resonators affects the positive and negative mixed coupling coefficients. The paper presents measurement data of miniature stripline three-resonator comb filter having an enhanced selectivity at the expense of two transmission zeros. The central frequency of filter is f0 = 1850 MHz, the bandwidth BW = 100 MHz. The filter having dimensions 5.8×4.2×2 mm was implemented by connecting two ceramic substrates having relative dielectric permittivity εr = 92 and the metallized patterns deposited on them.

Stripline bandpass filters with alternating coupling coefficients

This article shows the possibility in principle to design stripline comb filters with alternating signs of the coupling coefficients. The new feature of the stepped-impedance resonators of the quarterwave type was established. They provide the opposite sings of the electromagnetic coupling with adjacent resonators. Such resonators are asymmetric relative to the vertical axes, which is drawn through their middle part. The stripline passband filters with alternating signs of coupling coefficients have attenuation poles that are located to the left and to the right of the passband. Those poles improve the selectivity of such filters. The articles provide the measured characteristics of the stripline comb filter of the forth order with alternating coupling, which has the central frequency of f0 = 1835 MHz and the passband width of 90 MHz. The filter is constructed using a dielectric material with relative permittivity of εr = 92 and has the dimensions of 7.4×4.2×2 mm.

Thin stripline bandpass filters for the centimeter band

This article considers the design of thin stripline (1 mm) bandpass filters in the centimeter band, which contain dielectrics with different relative permittivity εr. This includes the choice of the resonators, the dielectric material, the preliminary assessment of resonators’ unloaded quality factors and taking into account the features of the frequency response curve of the filter. It was found, that the passband width of the thin comb filters with λ/4 resonators and array-type filters with λ/2 resonators cannot exceed 6% for any values of εr and the length of resonators of at least 2 mm. The array-type filters with resonators of half-wave type and with alternating signs of the coupling factors between resonators were proposed. Under certain additional conditions, the attenuation poles appear in such filters, resulting in improved selectivity. The results of computer modelling of the frequency response curve of thin filters of cm band are presented. They are compared to the frequency response of other filters. The data obtained from computer modelling showed good correspondence with the experimental data.

Varicap-tuned narrowband filters with extended rejection band based on U-shaped microstrip Resonators

A resonance equation for the first unwanted resonant frequency of tunable microwave U-shaped loop-type resonator with variable capacitance has been derived. This frequency does not depend on the variable capacitance value; it is invariable and proportional to λ-type oscillations. The ascertained feature makes it possible to determine the ratio of the first unwanted resonant frequency to the frequency of the main resonance and control the rejection bandwidth of tunable filters with U-shaped resonators. A narrowband (2%) varicap-tuned filter with extended rejection band has been built and its experimental data are presented. The experimental four-resonator filter could be tuned in the frequency range 225–400 MHz. The filter rejection band in terms of the attenuation level of –40 dB was located in the frequency range 420–1290 MHz, i.e., fmax /fmin = 3.07. Varicap-tuned filters with microstrip U-shaped resonators are shown to have a good potential for their practical use.