LTCC带通滤波器外文翻译.docx

1、LTCC带通滤波器外文翻译来源：Microwave Conference,2008.EuMc 2008.38th EuropeanBandpass Filters for Ka-Band Satellite Communication Applications Based on LTCC Abstract -The design of two compact bandpass filters for Ka-band satellite communication applications (downlink 1722 GHz) is presented. Both filters are de

2、signed with additional transmissionzeros at finite frequencies in order to improve the out-of-band selectivity. The filters have been realised as low-cost LTCC modules and the scattering parameters have been measured with on-wafer probing.I. INTRODUCTION Modern multimedia satellites are getting more

3、 complex with transponder connectivity requirements, multiple coverage beams, et cetera. Hence, satellite operators increasingly demand flexibility in function, efficient signal routing and signal processing. Therefore, future applications in multimedia satellite communications require innovative co

4、mponents with high RF-performance and, at the same time, with low weight, small size, and high reliability. Advanced integration and packaging technologies, such as low temperature co-fired ceramics (LTCC), combine different design techniques with low cost of fabrication, small size and multiple fun

5、ctionality. LTCC technology provides modular,hybrid-integrated systems with a high degree of miniaturization of microwave payload equipment and, hence, flexibility for adaptation to varying applications. It is one of the reasons,why LTCC became very popular, not only for low frequencydesigns, but fo

6、r high frequencies in the microwave and even millimeter-wave ranges as well . This paper focuses on bandpass filters for Ka-band downlink frequencies as important parts of multimedia satellite signal chains, which are based on LTCC multilayer technology and can be combined with other Ka-band microwa

7、ve LTCC modules presently under development. The two filters presented here display high stop-band isolation for an efficient suppression of the Ka-band uplink frequencies, and low insertion loss. They are developed for separating channel groups with total bandwidths of 500 MHz up to 1 GHz in the fr

8、equency range of 1722 GHz. For demonstration purposes, these filters have been developed for a centre frequency of f0 = 19.5 GHz. Additional effort has been spent in investigating the influence of grounding and different conductive pastes on the filter performance.II. DESIGN OF LTCC BANDPASS FILTERS

9、 WITH TRANSMISSION ZEROS AT FINITE FREQUENCIES The following specifications have been chosen for the design of the bandpass filter: -Passband: 18000 21000 MHz; -Maximum in-band insertion loss: 2 dB; -Minimum in-band return loss: 12 dB (VSWR 1.7); -Steepness of the filter slopes: 20 dB/GHz. Besides m

10、eeting these specifications, the following problems have to be solved with respect to the high frequencies of operation: (a) feeding of the filters with low-loss half-wavelength transmission lines to improve the matching at the input and output ports; (b) providing high-quality transitions from the

11、striplines embedded in the LTCC module to the coplanar ground-signal-ground test port for on-wafer probing. Because of the strict in-band requirements, the number of resonators constituting the filter could not be higher than four. In order to provide the required steepness of the filter skirts,two

12、designs with transmission zeros at finite frequencies have been chosen: a coupled-line filter design and a cross-coupled filter design.A. Coupled-line Filter Design For the coupled-line filter, we applied the established design of bandpass filters based on half-wavelength coupled resonators with att

13、enuation zeros 8. With this method, attenuationpoles are obtained by both input/output and inter-stage coupling.Tap-coupling,parallel-coupling and anti-parallel coupling structures were investigated. For the tap-coupling structure, an attenuation pole is generated at that frequency at which the elec

14、trical length from the phase centre of the tap to the open end of the resonator becomes 90. In order to generate an attenuation pole at pf0, a tap-coupling should be devised at a position where the electrical length tap from the open is equivalent to 90/p at centre frequency。 For the parallel-couple

15、d lines structure, transmission becomes zero at the frequency where the electrical length of the coupled line becomes 180. Therefore, to generate an attenua-tion pole at pf0, the electrical length of the coupled line at centre frequency p has to be chosen 180/p . Since the electrical length of a hal

16、f-wavelength resonator is 180, p will exceed 1. This implies that an attenuation pole can only be obtained at frequencies above the pass-band. For the anti-parallel coupled structure, where the open ends of the parallel lines are placed side by side, a pole is generated at pf0 under the condition ap

17、 = 90/p, where ap is the electrical length of the coupled line at centre frequency. As for the tap coupling, the attenuation pole can be obtained both below and above the pass-band. Two tap-couplings and one anti-parallel coupling have been used to design a four-pole bandpass filter with three atten

18、uation zeros placed at 16.82 GHz, 22.43 GHz, and 32.88 GHz. The filter layout is shown in Fig. 1, panel (a). Half-wavelength feed-lines have been employed to reduce the influence of the feed-line impedance and provide ,therefore,good impedance matching. The initial simulation of the filter structure

19、 was performed by a 2.5-dim electromagnetic field simulator (AWR Microwave Office). Verification was carried out with a 3-dim full wave simulator (CST Microwave Studio). The simulated frequency response of the filter is presented in panel (b) of Fig. 1. The in-band insertion loss is less than 1.2 dB

20、. The return loss is not worse than 14.5 dB. The characteristic slopes at the band edges amount to about 20 dB/GHz.图1 Four-pole coupled-lines bandpass filter with three attenuation poles: layout (a) and simulated frequency response (b).B. Cross-coupled Filter Design The synthesis of bandpass filters

21、 with source-load coupling was theoretically described and experimentally verified, especially for two-pole filters . Such a cross-coupling allows to obtain a frequency response with equal numbers of transmission poles and zeros. The same source-load coupling can be applied to higher-order filters a

22、s well, allowing for additional stop-band attenuation. The scheme of a four-pole cross-coupled filter is depicted in Fig. 2, panel (a). The resonators are represented by nodes, and the couplings are indicated as connecting lines. Two additional couplings have been added to the filter. The coupling C

23、1 is a capacitive coupling between the input and the output feedlines of the filter; the coupling C2 is an inductive crosscoupling between the first and the fourth resonator. Adjusting the strength of the cross-coupling, the positions of the transmission zeros and the steepness of the filter slopes

24、could be tuned to the desired values. The topology of the four-pole cross-coupled filter is shown in panel (b) of Fig. 2. The filter was implemented using LTCC multi-layer ceramics and consisted of four C-shaped stripline resonators, situated in two conductive layers: the first and the fourth resona

25、tor lines were printed in the bottom layer, while the second and the third resonator as well as the feed-lines were placed on the top conductive layer. The separation of the resonators in the vertical direction enables the reduction of the overall size of the filter, compared with an entirely planar

26、 structure. The numerical simulations were performed in two steps as described above. The expected frequency response of the cross-coupled filter is shown in Fig. 2, panel (c). Two pairs of transmission zeros, placed symmetrically around the pass-band, are clearly visible in both stop-bands of the f

27、ilter. The in-band insertion loss IL was not worse than 1.4 dB, and the return loss RL better than 15 dB. The area occupied by the filter was 55 mm2. The steepness of the skirts amounted to 45 dB/GHz. Comparing the responses of the two types of filter (Fig. 1 and Fig. 2) reveals that the cross-coupl

28、ed filter provides much higher attenuation in the narrow stop-band but, atfrequencies around 32-35 GHz, the performance suffers from a spurious harmonic, which was suppressed by one of the transmission zeros in the coupled-line filter design.图2 Four-pole cross-coupled filter: (a) schematic, (b) mult

29、i-layer layout, (c) simulated frequency response.III. FABRICATION AND MEASUREMENTS OF THE FILTERS Both filter structures were manufactured using the DuPont Green Tape 951 LTCC system with a thickness of the dielectric layers of 205 m (DP-951 AX/PX) and a nominal dielectric permittivity r = 7.8 after

30、 sintering This material system has been chosen for fabricaton, because it includes a variety of appropriate inks, photoimageable screen printing (Fodel-technology) 12, and provides satisfactory hermeticity and planarity of the sintered modules. Fig. 3 shows a photograph of LTCC-integrated Ka-band f

31、ilters. 图3 LTCC module with the filter samples fabricated.Two different conductive materials were used for the fabrication: photo defined silver paste with a thickness of 7 m after sintering, and a laser-cut silver foil with a thickness of 25m. The built stack of LTCC-layers integrating the develope

32、d filters was laminated with a pressure of 20 MPa and a temperature of 70C for 10 minutes. The co-fired sintering was conducted in a muffle furnace using a firing profile with 875C peak temperature for 10 minutes and an overall duration of about 450 minutes. The electrical characterisation of the filters was conducted using an Agilent E8367A PNA vector network Analyser (up to 67 GHz) and 200-m-pitch coplanar ground-signal-ground probe tips (|Z|-probes from Suess MicroTec). The measured performance of the two different coupled-line filter samples is shown in Fig. 4. W