Design Consideration for
Future RF Circuits
Circuits and Systems, 2007. ISCAS 2007.
IEEE International Symposium 27 May 2007
Author : Behzad Razavi
Presenter : Kyungjin Yoo
I.

Introduction
RF circuits - 2 trends



New paradigm



Device level: speed, noise
System level: System-on-chips
Multi-band, multi-mode transceivers
Baseband processors
Issues in this paper


Technology scaling
Design techniques
II.
Impact of Technology Scaling
1.
Lower supply voltages
2.
Higher gate leakage currents
3.
Lower transistor output impedances
Supply Voltage Scaling


Noise, linearity, gain
Trade off



Mixer
Oscillator
VCO
Transistor Output Impedance


Lower the Q of oscillators
deQing effect of ro >> Rp


Negligible in 90-nm technology : ro=2.3 Kohm
Problematic in 65-nm and 45-nm generation
Gate Leakage Current


Gate leakage current in 90-nm tech :
10~100pA/micrometer^2
90-nm : IG/Cp70-700 microV/ns

Tin=50ns causes 3.5-35mVpp ripple
III. Design Techniques
1.
Low-Voltage Active Mixers
2.
Multi-Band Techniques
Low-Voltage Active Mixers

Principle :
bias current to the switching pair and the loads
< bias current to the RF transconductor device
Multi-Band Techniques

Goal



Minimize area
avoid long interconnects at
high freq.
Layout compaction


Stacked inductors: LNA,VCO
Nested inductors: dualband oscillator
Thank you!
Q&A