VISHAY VITRAMON Ceramic Chip Antenna Application Note VJ 6040 GSM Interference Immune Tuning Circuit VJ 6040 GSM INTERFERENCE IMMUNE TUNING CIRCUIT GSM Antenna VJ 6040 VJ 6040 is a narrow band antenna that requires an active digital tuning circuit to allow it to cover the UHF band which spans between 470 MHz and 860 MHz. The tuning circuit typology is designed to withstand external interference such as GSM transmission. Tuning Circuit GSM Connector Port 1 Vishay offers an evaluation kit fitted with the GSM immune tuning circuit and the VJ 6040 miniature UHF antenna to allow designers to measure the antenna parameters. UHF Connector For any technical support please contact: [email protected] Port 2 Nevertheless, in cases where the GSM transmitter is in close proximity to VJ 6040, the tuning circuit typology should be modified to eliminate the risk of antenna detuning. The following document describes in detail the GSM interference immune tuning circuit. CHOOSING THE CORRECT TUNING CIRCUIT Vishay Vitramon division provides two tuning circuit reference designs: Network Analyzer S12 • Standard tuning circuit - described in detail in a separate application note titled “EVK 6040 User Guide”. Fig. 1 - Test Setup • GSM immune tuning circuit - described hereafter. The standard typology enables excellent antenna performance while maintaining minimal cost. However, the standard tuning circuit can withstand GSM interference up to 0 dBm, measured at the VJ 6040 antenna feed. The power received by VJ 6040 can be estimated using the test setup described in figure 1. Once the coupling factor is measured, the received power at the VJ 6040 feed can be estimated as follows: Received Power = Transmitted Power + Coupling Factor Example: If the GSM peak power output is + 33 dBm and the coupling factor was found to be - 15 dB then the maximum received power would be + 18 dBm. The GSM immune tuning circuit should be used in cases where the peak received power is greater than 0 dBm. Document Number: 45155 Revision: 07-Jul-10 For technical questions, contact: [email protected] www.vishay.com 13 APPLICATION NOTE A test PCB should be designed to accommodate both VJ 6040 and the GSM antennas. The two antennas should be positioned as far from each other as allowed by the mechanical constraints of the application. Using a network analyzer, the coupling between the antennas can be directly measured for each of the four channels offered by the tuning circuit. The same test setup can later be used to fine tune the tuning element components to negate any detuning caused by the GSM antenna, or other nearby components. Application Note Vishay Vitramon VJ 6040 GSM Interference Immune Tuning Circuit GSM IMMUNE TUNING CIRCUIT TYPOLOGY Figure 2 presents the schematic drawing of the recommended tuning circuit. Schematics VJ 6040 L1 R1 L4 D1 Digital input 1 L2 C3 R2 L5 L3 D2 Digital input 2 C4 R3 C1 L6 C2 50 Ω RF feed APPLICATION NOTE Fig. 2 - Tuning Circuit Schematics www.vishay.com 14 For technical questions, contact: [email protected] Document Number: 45155 Revision: 07-Jul-10 Application Note Vishay Vitramon VJ 6040 GSM Interference Immune Tuning Circuit LAYOUT Figure 3 shows the recommended layout of the tuning circuit. Layout should be as compact as possible. VISHAY VJ 6040 L1 Digital input 1 R1 L4 L2 D1 D2 L5 R2 Digital input 2 L3 C3 C4 R3 L6 C1 L4 C2 50 W line Ground plane copper area on top, bottom and/or inner layers Conducting strip lines 0402 component Via hole to ground plane Fig. 3 - Tuning Circuit Layout Document Number: 45155 Revision: 07-Jul-10 For technical questions, contact: [email protected] www.vishay.com 15 APPLICATION NOTE Legend Application Note Vishay Vitramon VJ 6040 GSM Interference Immune Tuning Circuit LAYOUT GUIDELINES 1. The distance between the tuning circuit components should be minimized 2. Inductor L1 should be located as close as possible to the antenna 3. Inductors L4 and L5 should be as close as possible to the PIN diodes 4. It is recommended to remove all ground planes from under the tuning circuit. The ground plane should be added to insure a 50 Ω wave guide after capacitor C1 REFERENCE TUNING CIRCUIT BOM TABLE 1 - TUNING CIRCUIT BILL OF MATERIALS VALUE REFERENCE QUANTITY PER CIRCUIT PART NUMBER MANUFACTURER 120 nH L4, L5, L6 3 HK 1005 R12J-T Taiyo Yuden D1, D2 2 BAR63-05W Infineon 39 nH L1 1 IMC0402ER39NJ Vishay 22 nH L2 1 IMC0402ER22NJ Vishay 27 nH L3 1 IMC0402ER27NJ Vishay 3.9 pF C1 1 VJ0402A3R9BXACW1BC Vishay 220 pF C2, C3, C4 3 VJ0402A221JXACW1BC Vishay 330 Ω R1, R2, R3 3 CRCW0402330RFKED Vishay PIN diode Note • Any changes made in the reference BOM might result in loss of radiation efficiency. CONTROL SIGNAL INTEGRITY The following table describes the desired control signal properties: TABLE 2 - SIGNAL INTEGRITY FOR ELECTRICAL CONTROL ALTERNATIVE Parameter SYMBOL MIN. TYP. MAX. UNITS COMMENTS Equivalent DC Circuit VCC Logical LOW Vil - 0.3 0 0.2 V APPLICATION NOTE Equivalent DC Circuit VCC Logical HIGH Source current Sink current www.vishay.com 16 Vih 2 3 5 V Isource 0 0.01 0.05 mA Vin = 5 V Diode reverse leakage current Isink 4 4.2 5 mA Vin = - 0.3 V For technical questions, contact: [email protected] Document Number: 45155 Revision: 07-Jul-10 Application Note Vishay Vitramon VJ 6040 GSM Interference Immune Tuning Circuit CHANNEL CHARACTERISTICS The two digital control lines offer four frequency channels as described in table 3 below. This table shows the typical peak gain obtained in each of the four channels. TABLE 3 - PEAK GAIN OBTAINED IN EACH OF THE FOUR CHANNELS PARAMETER D1 D2 BAND (MHz) S11 (dB) 460 5 560 660 760 860 760 860 760 860 760 860 0 -5 1 H H 470 to 540 - 10 - 15 - 20 - 25 460 5 f (MHz) 560 660 0 -5 2 L H 540 to 620 - 10 - 15 - 20 - 25 460 5 f (MHz) 560 660 0 -5 3 H L 620 to 750 - 10 - 15 - 20 - 25 460 5 f (MHz) 560 660 0 -5 4 L L 750 to 860 (1) - 10 - 15 - 25 f (MHz) Note (1) Applications withstanding strong GSM interference will incorporate a band pass filter designed to filter out the interfering signal. Such a filter will add significant attenuation above 750 MHz. The company’s products are covered by one or more of the following: WO2008250262 (A1), US2008303720 (A1), US2008305750 (A1), WO2008154173 (A1). Other patents pending. ORDERING INFORMATION VISHAY MATERIAL PACKAGING QUANTITY VJ 6040 VJ6040M011SXISRA0 1000 pieces Document Number: 45155 Revision: 07-Jul-10 For technical questions, contact: [email protected] www.vishay.com 17 APPLICATION NOTE - 20