® Accu-P Thin-Film Capacitors Act as Band Reject Filters A B S T R A C T : AVX Accu-P ® capacitors exhibit excellent resonance stability which makes them ideal for Band Reject Filters, whereas Ceramic capacitors are unsuitable due to their wide SRF scatter. Avital Yaish AVX Corporation Accu-P® Thin-Film Capacitors Act as Band Reject Filters Avital Yaish AVX Corporation The exact capacitance value should be determined experimentally as it will be affected by the surrounding circuit. Definition of Band Reject Filters (BRF) An Outline of Band Reject Filers Band reject, or notch, filters are used to reject a narrow frequency band and pass a wide frequency range. B. Intermodulation frequencies suppression. Transceiver characteristics may be affected by internally generated frequencies. In these cases the signal frequency and amplitude are known so that a narrow band BRF is ideally suited for the application. Traditionally, BRF’s are custom designed for each specific frequency application. Basic design C. Multi-Band Systems. In multi-band transceivers, which operate at several frequencies, BRF are used as additional decoupling elements both in the receiving and the transmitting channel. When several RF systems work simultaneously, e.g. WCDMA at 1.9 GHz and short range accessories at 2.4 GHz or 5.2 GHz, parasitic signals may form in the main channel, lowering the receiver sensitivity. A BRF can be realized by a simple shunt capacitor (Figure 1) or by a more elaborate Twin T design (Figure 2) R C C R 2C C BRF realization using Accu-P® Capacitors R/2 Figure 1. Shunt Capacitor Design AVX’s Accu-P® Thin-Film RF capacitors are a simple BRF that is both cost effective and miniature. Until recently, most high frequency/microwave capacitors were based on fired-ceramic (porcelain) technology. Layers of ceramic dielectric material and metal alloy electrode paste are interleaved and then sintered in a high temperature oven. This technology exhibits component variability in dielectric properties (losses, dielectric constant and insulation resistance), variability in electrode conductivity and variability in physical size. Figure 2. Twin T Design Major applications Band reject filters (BRF) perform several basic functions in RF circuits. A. Additional filtering of the basic signal harmonics (2F0, 3F0, 4F0). The Thin-Film Capacitors developed by AVX virtually eliminate these variances. Thin-Film technology is commonly used for producing semiconductor devices. In the last two decades, this technology has developed tremendously, both in performance and in process control. Today line definitions of below 1 µm and layer thickness control of 100Å (10-2 µm) are possible. Applying this technology to the manufacture of capacitors has enabled the development of components where both electrical and physical properties can be tightly controlled. In this case, the BRF is located either at the PA output or next to the antenna: PA BRF Matching Circuit Antenna Accu-P® RF Capacitors are made by Thin-Film Technology (see Figure 3) and exhibit nearly ideal characteristics. Harmonic rejection is usually performed by a LPF located after the PA, but the need often arises to suppress a spurious harmonic at a later stage of development or when the circuit is actually in production. In these cases an AVX Accu-P® Thin-Film RF capacitor is the preferred solution. 2 Table 1 Orientation Marking SRF [MHz] for Accu-P® 0402, 0.2 pF 4 different production batches. Alumina # 1 2 3 4 5 6 7 8 9 10 AVG MAX MIN STD Electrode Seal Dielectric Electrode Alumina Terminations Figure 3. Accu-P® Capacitor Structure Batch 1 23,256 23,199 23,256 23,238 23,217 23,199 23,272 23,238 23,256 23,232 23,236 23,272 23,199 25 Batch 2 23,256 23,290 23,256 23,199 23,199 23,276 23,296 23,260 23,288 23,238 23,256 23,296 23,199 35 Batch 3 23,459 23,479 23,483 23,479 23,461 23,479 23,472 23,479 23,461 23,441 23,470 23,483 23,441 14 Batch 4 23,198 23,246 23,204 23,161 23,170 23,178 23,210 23,188 23,226 23,179 23,196 23,246 23,161 26 0 The main features of Accu-P® may be summarized as follows: (3.3pF) -5 • High purity of electrodes for very low and repeatable ESR. -10 • Highly pure, low-K dielectric for high breakdown voltage, high insulation resistance and low losses at frequencies up to 40GHz. -20 MLC Thin Film -20 -25 s11 (dB) (dB) -15 -30 • Very tight dimensional control for uniform and stable frequency characteristics, unit to unit, batch to batch, year after year. -35 • Very tight capacitance tolerances for high frequency signal applications. -50 -30 -35 -40 -40 -45 -50 3500 -45 Accu-P® capacitors are the ideal component for realizing the simple notch filter shown in Figure 1. For each capacitance value a very stable impedance is displayed over a wide range of frequencies, see Figure 4. -25 0 10000 Freq (MHz) 4250 Freq (MHz) 9000 20000 Figure 5. Typical Thin-Film vs. Ceramic MLC SRF Distribution. • Determine the frequency FO that needs to be rejected. • Select an Accu-P® capacitor case size. 0 • Use the SRF vs. Capacitance graph (Appendix 2) for the selected case size in order to find an Accu-P® capacitance with an SRF closest to FO. -10 • Order samples of that Accu-P® capacitance as well as of neighboring capacitance values. dB -20 20 0.2 pF -30 • For a wider selection range order Accu-P® Engineering Kits (Appendix 3). 0.4 pF 0.3 pF 1 pF -40 • The best Accu-P® capacitance value for the particular circuit can now be experimentally determined. 0.7 pF 16 pF -50 0 5 10 15 20 25 Frequency, GHz Figure 4. S21 for Several Capacitance Values, Accu-P® 0402 The capacitance value is experimentally determined for each specific application. Table 1 and Figure 5. show Accu-P®’s excellent resonance stability compared to ceramic capacitors which cannot be used as BRF’s because of their wide SRF scatter. BRF Design steps: 3 Appendix 1: Measurement Technique Appendix 2 : SRF vs. Capacitance Graphs AVX Accu-P® 0201 Capacitors SRF vs. Capacitance Agilent 8722 ET/ ES Network Analyzer 12.0 Port 1 Port 2 10.0 SRF (GHz) 8.0 10dB Attenuator Microstrip Z=50? 6.0 4.0 2.0 Capacitor 0.0 Ground 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Capacitance (pF) SRF Test Setup AVX Accu-P® 0402 Capacitors SRF vs. Capacitance Connector 1 Connector 2 20.0 Short 18.0 Open 16.0 Connector 3 SRF (GHz) 14.0 Connector 4 12.0 10.0 8.0 6.0 4.0 2.0 Measurement Jig 0.0 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 Capacitance (pF) Microstrip Ground Component AVX Accu-P® 0603 Capacitors SRF vs. Capacitance 20.0 18.0 16.0 SRF (GHz) 14.0 Close-up of Capacitor on Jig 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0.0 5.0 10.0 15.0 20.0 Capacitance (pF) Test Setup 4 25.0 30.0 35.0 Appendix 3: Engineering Kits Accu-P® Accu-P® Accu-P® Designer Kit Type 1700 Order Number: Accu-P® 0201KIT02 Designer Kit Type 1800 Order Number: Accu-P® 0201KIT03 Designer Kit Type 1300 Order Number: Accu-P® 0402KIT01 Volts 25 16 10 Capacitors Tolerance Value pF 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.5 1.8 2.0 2.2 2.4 2.7 3.0 3.3 3.6 3.9 4.7 5.6 6.8 7.5 8.2 10.0 12.0 A A A B B B B B B B B B B B B B B B B B B B B B B B B B G G 600 Capacitors, 20 each of 30 values Tolerance A = ± 0.05pF B = ± 0.1pF G = ± 2% Volts 25 16 10 Capacitors Tolerance Value pF 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.3 3.4 3.6 3.9 4.1 4.3 4.5 4.7 A A A A A A A A A A A B B B B B B B B B B B B B B B B B B B 600 Capacitors, 20 each of 30 values Tolerance A = ± 0.05pF B = ± 0.1pF Volts 25 16 10 Capacitors Tolerance Value pF 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.5 1.8 2.0 2.2 2.4 2.7 3.0 3.3 3.9 4.7 5.6 6.8 8.2 10.0 12.0 15.0 18.0 22.0 A A A B B B B B B B B B B B B B B B B B B B B B B G G G G G 600 Capacitors, 20 each of 30 values Tolerance A = ± 0.05pF B = ± 0.1pF G = ± 2% Accu-P® Accu-P® Accu-P® Designer Kit Type 1400 Order Number: Accu-P® 0402KIT02 Designer Kit Type 900 Order Number: Accu-P® 0603KIT01 Designer Kit Type 800 Order Number: Accu-P® 0805KIT02 Volts 25 Capacitors Tolerance Value pF 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.3 3.4 3.6 3.9 4.1 4.3 4.5 4.7 A A A A A A A A A A A B B B B B B B B B B B B B B B B B B B 600 Capacitors, 20 each of 30 values Tolerance A = ± 0.05pF B = ± 0.1pF Volts 50 25 Capacitors Tolerance Value pF 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.5 1.8 2.0 2.2 2.4 2.7 3.0 3.3 3.9 4.7 5.6 6.8 8.2 10.0 12.0 15.0 18.0 22.0 A A A B B B B B B B B B B B B B B B B B B B B B B G G G G G 600 Capacitors, 20 each of 30 values Tolerance A = ± 0.05pF B = ± 0.1pF G = ± 2% 5 Volts 100 50 25 Capacitors Tolerance Value pF 0.1 0.2 0.3 0.4 0.5 0.7 0.8 0.9 1.0 1.2 1.5 1.8 2.0 2.2 2.7 3.3 3.9 4.7 5.6 6.8 8.2 10.0 12.0 15.0 18.0 22.0 27.0 33.0 39.0 47.0 A A A A B B B B B B B B B B B B B B B B B G G G G G J J J J 300 Capacitors, 10 each of 30 values Tolerance A = ± 0.05pF G = ± 2% B = ± 0.1pF J = ±5% Appendix 3: Engineering Kits (Cont.) Accu-P® Accu-P® Designer Kit Type 700 Order Number: Accu-P® 1210KIT02 Designer Kit Type 2100 Order Number: Accu-P® 0402KIT03 Volts 100 Capacitors Tolerance Value pF 1.0 1.5 1.8 2.2 2.7 3.3 4.7 5.6 6.8 10.0 12.0 18.0 22.0 27.0 33.0 Volts B B B B B B B B B G G G G G G 25 Capacitors Tolerance Value pF 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 P P P P P P P P P P P P P P P 300 Capacitors, 20 each of 15 values Tolerance P = ± 0.02pF 150 Capacitors, 10 each of 15 values Tolerance B = ± 0.1pF G = ± 2% Accu-P® Accu-P® Designer Kit Type 2200 Order Number: Accu-P® 0603KIT02 Designer Kit Type 2000 Order Number: Accu-P® 0201KIT04 Volts 50 Capacitors Tolerance Value pF 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 Volts P P P P P P P P P P P P P P P 25 300 Capacitors, 20 each of 15 values Tolerance P = ± 0.02pF Capacitors Tolerance Value pF 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 P P P P P P P P P P P P P P P 300 Capacitors, 20 each of 15 values Tolerance P = ± 0.02pF 6 AMERICAS EUROPE ASIA-PACIFIC AVX Myrtle Beach, SC Corporate Offices AVX Limited, England European Headquarters AVX/Kyocera, Singapore Asia-Pacific Headquarters Tel: 843-448-9411 FAX: 843-448-1943 Tel: ++44 (0) 1252-770000 FAX: ++44 (0) 1252-770001 Tel: (65) 6286-7555 FAX: (65) 6488-9880 AVX Northwest, WA AVX/ELCO, England AVX/Kyocera, Hong Kong Tel: 360-699-8746 FAX: 360-699-8751 Tel: ++44 (0) 1638-675000 FAX: ++44 (0) 1638-675002 Tel: (852) 2-363-3303 FAX: (852) 2-765-8185 AVX North Central, IN AVX S.A., France AVX/Kyocera, Korea Tel: 317-848-7153 FAX: 317-844-9314 Tel: ++33 (1) 69-18-46-00 FAX: ++33 (1) 69-28-73-87 Tel: (82) 2-785-6504 FAX: (82) 2-784-5411 AVX Midwest, MN AVX GmbH, Germany AVX/Kyocera, Taiwan Tel: 952-974-9155 FAX: 952-974-9179 Tel: ++49 (0) 8131-9004-0 FAX: ++49 (0) 8131-9004-44 Tel: (886) 2-2698-8778 FAX: (886) 2-2698-8777 AVX Mid/Pacific, CA AVX srl, Italy AVX/Kyocera, Malaysia Tel: 510-661-4100 FAX: 510-661-4101 Tel: ++390 (0)2 614-571 FAX: ++390 (0)2 614-2576 Tel: (60) 4-228-1190 FAX: (60) 4-228-1196 AVX Southwest, AZ AVX Czech Republic Tel: 602-678-0384 FAX: 602-678-0385 Tel: ++420 57 57 57 521 FAX: ++420 57 57 57 109 ASIA-KED KED, Hong Kong Tel: (852) 2305 1080 FAX: (852) 2305 1405 KED, Shanghai Tel: (86) 21 6859 9898 FAX: (86) 21 5887 2542 KED, Beijing Tel: (86) 10 5869 4655 FAX: (86) 10 5869 4677 KED, South Korea Elco, Japan Tel: 045-943-2906/7 FAX: 045-943-2910 Tel: (82) 2 783 3288 FAX: (82) 2 783 3207 KED, Taiwan Tel: (886) 2 2950 0268 FAX: (886) 2 2950 0520 KED, Singapore Tel: (65) 6255 3122 FAX: (65) 6255 5092 Kyocera, Japan - AVX AVX South Central, TX Tel: (81) 75-604-3426 FAX: (81) 75-604-3425 Tel: 972-669-1223 FAX: 972-669-2090 Kyocera, Japan - KDP AVX Southeast, GA Tel: (81) 75-604-3424 FAX: (81) 75-604-3425 Tel: 404-608-8151 FAX: 770-972-0766 AVX Canada AVX/Kyocera, Shanghai, China Tel: 905-238-3151 FAX: 905-238-0319 Tel: 86-21 6341 0300 FAX: 86-21 6341 0330 AVX South America AVX/Kyocera, Beijing, China Tel: ++55-11-2193-7200 FAX: ++55-11-2193-7210 Tel: 86-10 8458 3385 Fax: 86-10 8458 3382 Contact: A KYOCERA GROUP COMPANY http://www.avx.com S-APTF0M706-N