VISHAY VITRAMON Multilayer Chip Capacitors Application Note VJ 6040 Tuning Circuit and Channel Selection VJ 6040 TUNING CIRCUIT AND CHANNEL SELECTION 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. SCHEMATICS Figure 1 presents the schematic recommended tuning circuit. of the VJ 6040 VJ 6040 reference tuning circuit is composed of two PIN diodes that enable four channels within the UHF band. This document describes these channels, and offers a detailed description regarding how to control the tuning circuit to obtain optimal antenna efficiency. Applications that do not require the full coverage of the UHF band can enjoy added efficiency by setting VJ 6040 to a single fixed channel. drawing C6 L1 L3 R1 Digital Input 1 D0 The values described in this application note have been measured using the VJ 6040 evaluation kit. D1 C1 L4 R2 D2 L2 VJ 6040 REFERENCE TUNING CIRCUIT The aggressive antenna miniaturization process that resulted in the ultra-small form factor of the antenna also caused the unwanted effect of reducing the antenna bandwidth to approximately 120 MHz at - 3 dBi from its peak value. Full coverage of the UHF band (470 MHz to 860 MHz) can be achieved by implementing a simple four channel active digital tuning circuit. The tuning circuit shifts the central operating frequency of the antenna, thus allowing full coverage of the UHF band. L5 R3 Digital Input 2 D1 C4 C5 C7 C2 Tuning circuit key features are: • Small outline - fits onto a single side PCB of 5 mm x 5 mm 50 Ω RF feed • Low cost BOM) Fig. 1 - Tuning Circuit Schematics • Robust design not affected by interference sources such as GSM Document Number: 45159 Revision: 06-Jul-09 For technical questions, contact: [email protected] www.vishay.com 1 APPLICATION NOTE • Digitally controlled - two digital control pins enable coverage of the entire band, by offering 4 combinations Application Note Vishay Vitramon VJ 6040 Tuning Circuit and Channel Selection LAYOUT Figure 2 shows the recommended layout of the tuning circuit. Layout should be as compact as possible. VISHAY VJ 6040 L1 C3 L3 R1 C6 Digital Input 1 C1 L4 R2 D1 C7 L2 C6 C4 L5 Digital Input 2 R3 D2 C2 Legend 50 Ω Line Ground plane copper area on top, botton and/or inner layers Conducting strip lines 0402 component to the Receiver Via hole to ground plane Fig. 2 - Tuning Circuit Layout REFERENCE TUNING CIRCUIT BOM APPLICATION NOTE TABLE 1 - TUNING CIRCUIT BILL OF MATERIALS VALUE REFERENCE QUANTITY PER CIRCUIT PART NUMBER MANUFACTURER 120 nH L3, L4, L5 3 HK 1005 R12J Taiyo Yuden PIN diode D1, D2 2 ???? Infineon 39 nH L2 1 IMC0402ER39NJ Vishay 47 nH L1 1 IMC0402ER47NJ Vishay 2.2 pF C1, C5 2 VJ0402A2R2BXAC-W1BC Vishay 220 pF C2, C3, C4, C6, C7 5 VJ0402A221JXAC-W1BC Vishay 1 kW R1, R3 2 CRCW1KJNED Vishay 0W R2 1 CRCW0R0Z0ED Vishay Note • Any changes made in the reference BOM might result in loss of radiation efficiency. www.vishay.com 2 For technical questions, contact: [email protected] Document Number: 45159 Revision: 06-Jul-09 Application Note Vishay Vitramon VJ 6040 Tuning Circuit and Channel Selection SINGLE CHANNEL Applications that require less than full coverage of the UHF band can remove the tuning circuit and set the antenna to a single channel centered at any point within the UHF band. The single channel tuning circuit is comprised of two components as described below: VJ 6040 L1 C1 50 Ω RF feed Fig. 3 - Single Tuning Circuit Layout For example, setting VJ 6040 to a single channel centered at 725 MHz, can be achieved by assembling a 47 nH inductor at L1, and a 3.9 pF capacitor at C1. Contact Vishay Vitramon technical support for more details regarding single channel tuning circuit values. 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 Vih Logical LOW - 0.3 0 0.2 V 1 kΩ Vil Equivalent DC Circuit Vih 2 3 5 V Sink current Isink 0 0.01 0.05 mA Vin = - 0.3 V Diode reverse leakage current Source current Isource 4 4.2 5 mA Vin = 5 V 1 kΩ Logical HIGH Note • Any changes made in the reference BOM might result in loss of radiation efficiency. Document Number: 45159 Revision: 06-Jul-09 For technical questions, contact: [email protected] www.vishay.com 3 APPLICATION NOTE Vih Application Note Vishay Vitramon VJ 6040 Tuning Circuit and Channel Selection CHANNEL CHARACTERISTICS The two digital control lines offer four frequency channels as described in the table 3 below. This table shows the peak gain obtained in each of the four channels. TABLE 3 PARAMETER D0 D1 BAND (MHz) S11 (dB) Return loss 10 1 H L 470 to 540 S11 (dB) 0 460 510 560 610 660 710 760 810 860 - 10 - 20 - 30 - 40 - 50 f (MHz) Return loss 0 460 560 660 760 860 760 860 -2 L L 540 to 580 -4 S11 (dB) 2 -6 -8 - 10 - 12 f (MHz) Return loss 0 460 560 660 3 H H 620 to 750 S11 (dB) -2 -4 -6 -8 - 10 - 12 f (MHz) Return loss 460 0 510 560 610 660 710 760 810 860 4 L H 750 to 860 S11 (dB) -5 - 10 - 15 - 20 - 25 f (MHz) APPLICATION NOTE Features are subject to revisions or changes without notification 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 www.vishay.com 4 For technical questions, contact: [email protected] Document Number: 45159 Revision: 06-Jul-09