H Philips Semiconductors B.V. Gerstweg 2, 6534 AE Nijmegen, The Netherlands Report nr. Author Date Department : RNR-45-98-B-0827 : Haris Duric & Robert Cloudt : 16 December 1998 : DSC-N, Development CDMA CELLULAR VCO WITH THE BFG425W, BFG410W AND VARACTOR BB142 Abstract: This application note contains an example of a Voltage Controlled Oscillator for cellular CDMA applications with the fifth generation BFG425W and BFG410W Double Poly RF-transistors. The BB142 is a new varactor specially designed for RF-application with low noise performance. The VCO is designed for the receive band of the IS-95 standard. Appendix I: Schematic of the circuit Appendix II: Printlayout and list of used components & materials Appendix III: Results of measurements 1 H Philips Semiconductors B.V. Introduction: With the new Philips silicon bipolar double poly BFG400W series, it is possible to design low phase noise VCO’s for cellular and PCS frequency applications with a low current and a low supply voltage. These VCO’s are well suited for the new generation low voltage high frequency wireless applications. In this note an example of such an VCO will be given. This VCO is designed for a center frequency of 881.5 MHz and a span of 25 MHz. Designing the circuit: The circuit is designed to show the following performance: VSUP=2.7 V Isup=7.3mA Center freq=881.5 MHz Span = 25 MHz Pout = 3.33 dBm Phase noise at 60 kHz <= -117 dBc/Hz VSWRo<2:1 transistor: BFG425W, BFG410W varactor : BB142 The output matching is realised with a LC-combination in the buffer stage. The matching circuit will also supress the harmonics somewhat. There’s a trade off between the pulling and the noise performance of the VCO. Designing the layout: A lay-out has been designed with HP-MDS. Appendix II contains the printlayout and component placement. Measurements: Measurements of the total circuit (epoxy PCB) have been done. The result can be found in Appendix III. 2 H Philips Semiconductors B.V. Appendix I: Schematic of the circuit Figure 1:VCO circuit CDMA VCO Component list: Component: Value: C1 47n C2 3.6p C3 4.3p C4 56p C5 1.2p C6 3p C7 47n C8 56p C9 56p C10 47p C11 1.8p C12 6.8p R1 8.2k R2 22k R3 390 R4 2k R5 1k R6 100 L1 82n L2 12n L3 4n T1 BFG425W T2 BFG410W Varactor BB142 Comment: DC-filter Determines tuning range Determines tuning range DC-block Negative impedance Negative impedance DC-filter RF-bypass RF-bypass match between VCO and buffer RF-feed/output match Output match/filter Bias Bias Bias Bias Bias Better RF-stability (K>1) RF-choke Ouput match Microstripline inductance for better Q SOT 343 SOT 343 SOD 523 3 H Philips Semiconductors B.V. Appendix II: Printlayout and list of used components & materials GND Vtune Vsup C1 L3 L1 C7 Varactor C8 C9 R6 C3 C2 R4 R2 R5 C10 C4 R3 R1 C5 T1 C6 T2 C12 L2 C11 RF-out Figure 2: Printlayout CDMA VCO Component list: Component: Value: C1 47n C2 3.6p C3 4.3p C4 56p C5 1.2p C6 3p C7 47n C8 56p C9 56p C10 47p C11 1.8p C12 6.8p R1 8.2k Comment: 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips 4 H Philips Semiconductors B.V. R2 R3 R4 R5 R6 L1 L2 L3 T1 T2 Varactor 22k 390 2k 1k 100 82n 12n 4n (W=0.7mm;L=9.6mm) BFG425W BFG410W BB142 0402 Philips 0402 Philips 0402 Philips 0402 Philips 0402 Philips TDK MLG 1608 SERIES TDK MLG 1608 SERIES Microstrip (PCB: εr=4.6,H=0.5mm) SOT 343 SOT 343 SOD523 5 H Philips Semiconductors B.V. Appendix III: Results of measurements: Samples CDMA VCO's Specification Unit Value Vcc Power Consumption Control Voltage range Min. Volt <=mA Volt 2.7 7.3 0 Control Voltage range Max. Operating f range Min. Volt MHz 2.5 849 MHz MHz/V 900 17 >=dBm (+/-dBm) 3.33 0.17 <=dBc -75 Phase Noise(15KHz) Phase Noise(30KHz) <=dBc/Hz <=dBc/Hz -105 -111 Phase Noise(60KHz) <=dBc/Hz -117 Pushing figure (Vcc +/-0.3V) (+/-KHz) 400 Pulling figure (VSWR=2.0 for all phase, ref:50Ohm) (+/-KHz) 500 <=dBc -25 Operating f range Max. Modulation sensitivity Output Level Output level deviation C/N Spurious response (Harmonics) VSWRo Oscillation guaranteed for VCC = Width (mm) Length (mm) 1.8 Volt 2.4<Volt<3 10.25 10.1 6