(MO4B-4) A Fully Integrated 1.175-to-2GHz Frequency Synthesizer with Constant Bandwidth for DVB-T Applications L.Lu,L.Yuan,H.Min and Z.Tang 05 Fudan University No.825 Zhangheng Road Shanghai,China,201203 RFIC-Atlanta June 15-17,2008
RFIC – Atlanta June 15-17, 2008 1 (MO4B-4) A Fully Integrated 1.175-to-2GHz Frequency Synthesizer with Constant Bandwidth for DVB-T Applications L. Lu, L. Yuan, H. Min and Z. Tang Fudan University No. 825 Zhangheng Road Shanghai, China, 201203
Outline o Reasons that cause the variation of loop bandwidth Wideband VCO with constant tuning gain (Kyco)and band step Automatic frequency control (AFC)and charge pump Circuit details and measurement results RFIC-Atlanta June 15-17,2008
RFIC – Atlanta June 15-17, 2008 2 Outline • Reasons that cause the variation of loop bandwidth • Wideband VCO with constant tuning gain (KVCO) and band step • Automatic frequency control (AFC) and charge pump • Circuit details and measurement results
Motivation Dual-conversion DVB-T architecture needs a 1.175-to-2GHz frequency synthesizer Loop bandwidth changes due to VCO tuning gain (Kvco)and division ratio Variation of loop bandwidth may result in loop instability and phase noise deterioration To ensure loop bandwidth constant,some techniques are explored... RFIC-Atlanta June 15-17,2008
RFIC – Atlanta June 15-17, 2008 3 Motivation • Dual-conversion DVB-T architecture needs a 1.175-to-2GHz frequency synthesizer • Loop bandwidth changes due to VCO tuning gain (KVCO) and division ratio • Variation of loop bandwidth may result in loop instability and phase noise deterioration • To ensure loop bandwidth constant, some techniques are explored
Pros Cons Good points Single LC-VCO is used Loop bandwidth variation is within +10% Phase noise is nearly constant Integrated rms phase error is sub-1 。 Problems Process limits the minimum values of capacitors and varactors Add a little complexity in layout design RFIC-Atlanta June 15-17,2008
RFIC – Atlanta June 15-17, 2008 4 Pros & Cons • Good points – Single LC-VCO is used – Loop bandwidth variation is within ±10% – Phase noise is nearly constant – Integrated rms phase error is sub-1° • Problems – Process limits the minimum values of capacitors and varactors – Add a little complexity in layout design
Diagram of Third-Order PLL CP Multi-band VCO CP Kvco LPF PFD R +N RFIC-Atlanta June 15-17.2008 5
RFIC – Atlanta June 15-17, 2008 5 Diagram of Third-Order PLL 1 1 2 ref out div CP CP VCO
Definition of loop Bandwidth Open-loop cut-off frequency is selected as loop bandwidth,but not intuitively Loop gain is a good substitute For typical third-order PLL with second-order passive filter,loop gain can be expressed as BW=lrKvcoR1.bKvcoR1 b>10) 2TTN b+1 2TTN Kyco and N are variables RFIC-Atlanta June 15-17,2008 6
RFIC – Atlanta June 15-17, 2008 6 Definition of loop Bandwidth • Open-loop cut-off frequency is selected as loop bandwidth, but not intuitively • Loop gain is a good substitute • For typical third-order PLL with second-order passive filter, loop gain can be expressed as • KVCO and N are variables ⋅ ≈ CP VCO 1 CP VCO 1 IK R IK R b BW= (b>10) 2πN b+1 2πN
Conventional Capacitor Array Binary weighted capacitor array %。2北 tune RFIC-Atlanta June 15-17,2008
RFIC – Atlanta June 15-17, 2008 7 Conventional Capacitor Array f f f f f f f f tune 0 1 2 3 osc+ oscv v
F-V Curves of Conventional Topology 2.2 大10 Kvco max=320MHz/V F-V curve 2 fres_max- 174MH2 1.8 1.6 Kvco_max=8 1.4 Kyco_min 1.2 Ires_min= Kvco_min=40MHz/V 26MHz 0.4 0.6 0.8 1 1.2 1.4 Tuning Voltage(V) RFIC-Atlanta June 15-17.2008 8
RFIC – Atlanta June 15-17, 2008 8 F-V Curves of Conventional Topology Frequency(Hz)
Proposed Capacitor Array Size changeable capacitor array eno a15C1 tune 米 B en1 VB-O enig Vtune Size changeable varactor array RFIC-Atlanta June 15-17.2008 9
RFIC – Atlanta June 15-17, 2008 9 Proposed Capacitor Array
F-V Curves of Proposed Topology 2.2 109 F-V curve fres=67MHz Kvco=100MHz/V 2 1.8 1.6 1.4 1.2 0.4 0.6 0.8 1 1.21.4 Tuning Voltage(V) RFIC-Atlanta June 15-17.2008 10
RFIC – Atlanta June 15-17, 2008 10 F-V Curves of Proposed Topology Frequency(Hz)
