A Dynamic GHz-Band Switching Technique for RF CMOS VCO

K, Shibata. ; H, Sato. ; N, Ishihara. ;Silicon Monolithic Integrated Circuits in RF Systems, 2007 Topical Meeting on

Jan.10-12 2007 Page(s):273 - 276

積體電路設計研究所積體電路設計研究所

指導教授 指導教授 : : 林志明 教授林志明 教授

學生 學生 : : 郭峻瑋郭峻瑋

OutlineOutline

• Abstract

• Introduction

• Conventional VCO

• VCO circuit using simultaneous LC switching

• Experimental results and discussions

• Conclusion

Abstract• To get wide band switching, it has been clarified a

nalytically that keeping Q constant is important to configure the circuit.

• a dual band VCO circuit has been designed by using a 0.13-μm standard CMOS process technology and succeeded in switching the band dynamically from 2 to 4 GHz .

Introduction

• A circuit which can switch capacitors and inductors simultaneously has been suggested.

• The chip fabricated was operated with a power supply voltage of 1.7 V.

Conventional VCOConventional VCO

Fig. 1. Conventional LC-VCO circuit.

Where L: inductance for resonation, Cc: constant capacitance setting the operation band, Cvo: varactor capacitance, C0: total capacitance.

Value of Q is decreased by increasing value of Co.

VCO circuit using simultaneous VCO circuit using simultaneous LC switching LC switching

Fig. 2. Simultaneously LC switching VCO circuit.

Quality factors Q of those operating conditions areexpressed following equations respectively.

If loss resistance values of r1ow and rhigh are the same, acondition of keeping Q constant is

• Loss resistances are expressed by following equations respectively.

• If L1 is equals to L2 to simplify the discussion, a condition that r1ow becomes equal to rhigh to keep value of Q constant is

Low frequency (SW1: ON, and SW2: OFF).

High frequency (SW1: OFF, and SW2: ON).

Fig. 3. Equivalent circuit considered loss resistances.

Fig. 4. Resonant frequency switching characteristics simulated.

Experimental results and Experimental results and discussionsdiscussions

• Signal output buffers which can drive 50 Ω are added to the core LC-VCO circuit.

• The sizeis 1.8 mm x 1.7 mm.

• The chip packaged was measured by using a spectrum analyzer.

Fig. 5. VCO circuit fabricated.

Fig. 6. Microphotograph of the VCO chip.

Fig. 7. Oscillation frequency versus control voltage.

Fig. 8. Characteristics of Phase Noise.

• FOM and FOMT, were calculated using following equations.

• L{Δf } is measured phase noise at the frequency offset Δf from the carrier at fo, and PDC is the measured dc power dissipation in mW. And, FTR is frequency tuning range.

ConclusionConclusion