Hirotaka Sugawara, Yoshiaki Yoshihara, Kenichi Okada, and Kazuya MasuPrecision and Intelligence Laboratory, Tokyo Institute of Technology, Japan

Reconfigurable CMOS LNA for Software Defined Radio Using Variable Inductor

Background Reconfigurable RF Circuit

Multi-band RF front-end Architectures

Conclusion

Tunable LNA

L150Ω

50Ω

Vgs=0.65 V

Vdd=1.8 V

L2

L=0.2 µmW=5 µmm=60

L=0.2 µmW=5 µmm=60Pin

Pout

Wireless Standardsn Mobile phone 900MHz, 1.5GHz, 2GHz

(+ 800MHz, 1.7GHz, 1.9GHz for the new system)

(+ 800MHz, 900MHz, 1.8GHz, 1.9GHz for GSM)

n WLAN 802.11b/g, Bluetooth 2.4GHz

n WLAN 802.11a/n 5GHz

n GPS 1.2GHz/1.5GHzn DTV 470 MHz～770 MHz

Purpose

PA

LNA

LO

LPF DAC

ADC

SW

RF Front-End

I Q

MIX

MIX LPF

Bas

eban

d LS

I

Proposed Concept

To provide multiple functions to circuitsMulti-function

Reconfigurable RF Circuit Design K. Okada, et al., in ASP- DAC, Jan. 2005, pp.683-686.

A multi-band/mode circuit for wireless communication chips

Self-compensation

Si CMOS Technology provide

Wireless Communication Circuits

Realization of Si CMOS RF circuits

Reconfigurable RF Circuit

RF circuit is controlled by digital circuit

Architecture

Proposed Architecture

Variable InductorVariable Inductor

The inductance continuously varies depending on the position of the metal plate.

The metal plate shields the magnetic flux whichpenetrate the inductor.

h

Spiral Inductor

Metal Plate

consists of a planar-type spiral inductor and a metal plate.

MEMS Parallel Plate actuator

V. M. Lubecke, and J. -C. Chiao: The IEEE 4th Int. Conf. on Telecommunications in Modern Satellite, Cable and Broadcasting Services, 1999 p. 1stationary electrode

movable electrode

Moving system is realized to use MEMS actuator

Measurement

Turns : 3Line width : 10 µmLine space : 1.2 µmOuter diameter : 300 µm

0.9 pF

0.6 pF

0.18 µm M5 CMOS Process1.28 mm

0.97

mm

1.28 mm

0.97

mm

Variable Characteristic

0 5 10 15 20Frequency [GHz]

PG

[dB

]

-20

-10

20

10@ 1.9 GHzPG=14.2 dBPin=-27 dBm

0

0 5 10 15 20Frequency [GHz]

-100

-60

-20

-40

S12

[dB

]

@ 1.9 GHzPG=-31.0 dBPin=-27 dBm

-80

-30 -20 -10 0 5Pin [dBm]

-5

5

Pou

t[dB

m] 0

-10

-15

0 5 10 15 20Frequency [GHz]

S22

[dB

]S

11[d

B]

-20

-10

5

0

-5

S11

S22

S22 S11

1 2 3 4 5Frequency [GHz]

NF

[dB

]

10

4

8

6

@ 1.9 GHzNF=5.2 dB

-15

-5-15-25

@ 1.9 GHzS11=-11.0 dBS22=-12.7 dBPin=-27 dBm

Freq.=1.9 GHzInput P1dB=-15.8 dBm

1.898 1.899 1.901 1.903Frequency [GHz]

Am

plitu

de [d

B]

-1401.900 1.902

-120

-80

-40

0

-60

-20

-100

-52.5 dBm @ 1.899 GHz-13.1 dBm @ 1.900 GHz-13.1 dBm @ 1.901 GHz-53.2 dBm @ 1.902 GHz

Power= -27 dBmIIP3 =-7.2 dBm

high density integrationhigh frequency performanceLow fabrication cost

Wireless communication standards use severalfrequency bands.

Multi standard Baseband

Software Defined Radio (SDR)

It is necessary for global roaming using SDRto realize Multi-band RF front-end

400 MHz-6 GHz

To realize Multi-band RF front-end

To provide a compensating mechanismProcess variations, Modeling error, Temperature etc.

Control Digital Circuit

Proposed Tunable LNA

Multi-band Down convertor

Wide-band Antenna

f

Gai

n ...

TuningLNA Down convertor

・・

・

LNA Down convertor

f...G

ain

Using some signal paths for each frequency band

It needs large chip area to extend the number of communication standards.

Wide-band LNA

Gai

n

Multi-band Down convertor

Wide-band Antenna

f

Distributed amplifier needs large chip area and power consumption.

Using Distribute amplifier

multi-band LNA using resonator

Multi-band Down convertor

Wide-band Antenna

f

Gai

n ...

The approach require large chip area due to many resonators.

Using some input resonatorsWide-tunable CMOS LNA is realized by the variable inductor.

The proposed LNA achieves wide-tuning range with narrow-band gain and can be used for reconfigurable RF front-end.

Turns : 3Line width : 20 µmLine space : 1.2 µmOuter diameter : 400 µm

L1 L2

L1 L2

Q

4.5

3.5

3.0

4.0

@1.9 GHzLmax/Lmin=1.5

Height of plate h [µm]

3

L [n

H]

0 100 400

6

5

300200 500

4

Q

4

3

2

Height of plate h [µm]

3

L [n

H]

0 100 400

7

5

300200 500

4

6

@1.9 GHzLmax/Lmin=2.0

1Frequency [GHz]

0.1

Q

4

3

2

1

100

Decrease in Metal Plate Height

1Frequency [GHz]

0.1

L [n

H]

4

2

100

10

8

6

Decrease in Metal Plate Height

h=10 µmh=15 µmh=20 µmh=30 µm

h=50 µmh=100 µmw/o Metal plate

1Frequency [GHz]

0.1

Q

4

3

2

1

100

Decrease in Metal Plate Height

1Frequency [GHz]

0.1

L [n

H]

4

2

100

10

8

6

Decrease in Metal Plate Height

L1

L2h=10 µmh=15 µmh=20 µmh=30 µm

h=50 µmh=100 µmw/o Metal plate

Basic Characteristic

Freq. [GHz]Vdd [V]

Idd [mA]PG [dB]

S22 [dB]S11 [dB]

NF [dB]

IIP3 [dBm]Input P1dB [dBm]

1.91.8

7.414.2-11.0-12.75.2

-15.8-7.2

Vgs [V] 0.65

Summary of Performance

1 2 4 5Frequency [GHz]

PG

[dB

]

15

5

03

10

1 2 3 4 5Frequency [GHz]

NF

[dB

]

10

4

8

6

h=10 µmh=15 µmh=20 µmh=30 µmh=50 µmh=100 µmw/o Metal Plate

Noise Figure (NF) : Shift to higher frequency 　　　　　　　　 as metal plate inserts

Si CMOS Tunable LNA using the on-chip variable inductors for the SDRThe variable ratios of the variable inductors are over 1.5. The proposed LNA achieves PG of over 10 dB from 1.6 GHz to 3.2 GHz. The minimum NF is shifted to higher frequency as inductances vary.

This tunable LNA is quite useful for multi-band RF communication system with the reconfigurable RF circuit design.

h

Spiral Inductor

Metal Plate

Power Gain (PG) : 15 dB and over 10 dB 　　　　　　　　from 1.6 GHz to 3.2 GHz.

Decrease in Metal Plate Height

Decrease in Metal Plate Height