V.A. Maklashov – Deputy Director of Design Office in Radio Engineering Systems
JSC «SRI «Ekran» (Samara)
E-mail: mg37@rambler.ru
The article considers the problem of the reduction of the overall dimensions (minimization) and the increase of the manufacturability of the radio-receiving equipment working within microwave range. The shortcomings of the traditional design of microwave filters in micromodule version are demonstrated. To solve this problem a method of the embedding of microwave filters into the internal layers of the multilayer printed circuit is suggested. The results of the experimental research and calculation of the characteristics of the ultra wide band microwave filters manufactured on the multilayer printed circuit are considered. The comparison of the design data and experimental data is given; the temperature influence on the filter characteristics is demonstrated. The advantages of the stripline filters as compared with micro strip filters are listed. The recommendations for calculation, material selection and the structure of the multilayer printed circuit are given.
During the development of the ultra wide band radio-receiving equipment working in the microwave range the critical task is the reduction of the overall dimensions (minimization) and the increase of the manufacturability with simultaneously improvement of the technical characteristics. The construction of band-pass filters at the building of radio receivers must be of great importance, because many parameters of the receiver depend on their characteristics. The traditional structure of band-pass filters within microwave range has a micro strip version on microwave dielectrics such as Al2O3 (polycor) or on film-clad dielectrics of Rogers type. To get a good electrical performance one should place micro strip filters into electrohermetically sealed micro assembly with separation by metallic partitions, moreover the micro assemblies need hermetization and filling by dry nitrogen for protection from the environmental exposure (first of all moisture, hoarfrost and dew influence). Such construction leads to the weighting of the equipment and cost increase due to low manufacturability and high steel intensity. The using of strip-line filters embedded into printed circuit is one of solutions allowing the reduction of the overall dimensions and the increase of the manufacturability of microwave devices. Because of the absence of the input-output connection «on air» in strip-line filters, it is possible to provide a high selectivity using a high-order filter construction (more than 10th−12th order) with unachievable electrical performance for micro strip filters.
During the development of the strip-line filters it is necessary carefully to select the dielectric material, because the main characteristics of the filter depend on the dielectric material features. The most suitable material for strip-line filters is the film-clad microwave dielectric of RO3003 series by Rogers due to its high stability. To provide the geometric relationship of the pattern of the filter topology one must choose the thickness of the conducting copper layer (foil) between 2 values: 17 micron (½ oz.) or 9 micron (¼ oz.). In the strip-line version the filters of different types can be realized: low-pass filters (LPF), low-cut filters (LCF), bandpass filters (BPF) and low-and-high-pass filters (LHPF) as well.
Calculation is made using the electromagnetic simulation programs, such as CST Studio Suite by Dassault Systemes, Microwave Office by National Instruments and others.
A prototype of printed circuit with 17 filters of different types (LPF, LCF, BPF) and topology in the broad frequency range was produced to research strip-line filters and to check the methods of its calculation.
The prototypical circuit was placed into thermal environment chamber to research the stability of the filter characteristics at changing of the environmental temperature.
The experimental data show that the stability of the electrical performance of the strip-line filters on dielectric of series RO3003 is not worse than micro strip filters on Al2O3 substrate (polycor).
Thereby the research shows that the possibility of the replacement of micro strip filters produced on Al2O3 (polycor) by embedded into multilayer printed circuit strip-line filters for purposes of miniaturization and of the increase of the manufacturability of the radioreceiving equipment working within microwave range.
- Mattei G.L., Yang L.A., Dzhons E.M.T. Filtry SVCh, soglasuyushchie tsepi i tsepi svyazi. M.: Svyaz. 1971. (in Russian) 2. Hong J.-S. Microstrip Filters for RF/Microwave Applicationyu Edition 2nd. N.Y.: John Wiley & Sons, Inc. 2011.
- Spravochnik po elementam poloskovoi tekhniki. Pod red. A.L. Feldshteina M.: Svyaz. 1979. (in Russian)
- Zakharov A.V., Ilchenko M.E., Karnaukh V.Ya. Pinchuk L.S. Izvestiya VUZov. Radioelektronika. 2011. T. 54. № 3. S. 56. (in Russian) 5. Spravochnik po raschetu i konstruirovaniyu SVCh poloskovykh ustroistv. Pod red. V.I. Volmana. M.: Radio i svyaz. 1982. (in Russian)
- Zakharov A.V., Ilchenko M.E., Karnaukh V.Ya. Pinchuk L.S. Izvestiya VUZov. Radioelektronika. 2011. T. 54. № 3. S. 56. (in Russian)
- Spravochnik po raschetu i konstruirovaniyu SVCh poloskovykh ustroistv. Pod red. V.I. Volmana. M.: Radio i svyaz. 1982. (in Russian)
- Fukasawa A.. IEEE Trans. 1982. V. MTT-30. № 9. P. 1367.
- Makimoto M. Yamashita S. Microwave Resonators and Filters for Wireless Communication. Theory, Design and Application. Berlin: Springer. 2001.
- http://www.cstcorp.com.
- http://www.rogerscorp.com.