An Ultra-Wide-Band GHz LNA in 0.18µm CMOS technology RF Communication Systems-on-chip Spring 2007

Index of Contents  A brief introduction to UWB  Potential applications  Design of the LNA  Performance criteria  First stage: a common-gate  Second stage: a common-source  System simulation  Comparison with the original paper  Conclusions 2

A brief introduction to UWB 3

 A technology for transmitting information spread over a large bandwidth that should be able to share spectrum with other users.  The Federal Communications Commission (FCC) authorized the unlicensed use of the 3.1 to 10.6GHz band under strict power restrictions. 4 OFDM vs. Pulse-transmission

Potential applications  Wireless Communications Systems  Local and Personal Area Networks (LAN/PAN)  Roadside info-station  Short range radios  Military Communications  Radar and Sensing  Vehicular radar  Ground penetrating radar  Through wall imaging  Medical imaging  Surveillance 5

Design of the LNA 6

 As any Low-Noise Amplifier, an UWB LNA should have:  Low noise figure (i.e., below 6dB)  High gain (i.e., above 10dB)  Input matching to 50Ω (i.e., S11 below -10dB)  Output matching to 50Ω (i.e., S22 below -10dB)  But also, with a flat response in the whole GHz band. Performance criteria 7

 Two-stage amplifier  The first stage fixes the input impedance of the system and defines a low frequency resonance.  The second stage drives the LNA total gain by fixing a second resonance in the high frequency part of the band. Circuit description (I) 8

 The common-gate stage  Input impedance There is a resonance near DC. At high frequencies, g m1 becomes the dominant term. Circuit description (II) 9 With R L1 =320Ω, W M1 =55µm and V G1 =0.7V, g m1 is in the order of 20mS

 The common-source stage  Defines a second resonance in the high part of the band.  Provides the gain to the system.  The output buffer was already given: W M4 =55µm and I bias =5.7mA. Circuit description (III) 10 With R L2 =60Ω, W M2 =W M3 =120µm and V G2 =1V, both transistors are still in the saturation region

Circuit simulation 11

Circuit simulation (I) 12  Effect of changing L D2 from 1nH to 3nH Taking into account the UWB FCC mask already shown, trying to move the first resonance far below the 3GHz is not necessary.  Effect of changing L S1 from 2nH to 10nH Gain (dB)

Circuit simulation (II) 13  Effect of changing V G2 from 0.6V to 1.6V A good compromise between total gain and power consumption is achieved, for example, with 120µm and a V G2 equal to 1.2V.  Effect of changing W M2 and W M3 from 40µm to 200µm. Gain (dB)

Final results 14 L 0.18 μ m W M1 60 μ m W M2 120 μ m W M3 120 μ m W M4 55 μ m L S1 3.6nH L D2 1.84nH R L1 320 Ω R L2 60 Ω V G1 700mV V G2 1.2V

Design comparison 15 FigureCurrent circuitOriginal circuit Maximum Gain13dB12.4dB BW -3dB GHz0.4-10GHz Noise Factor dB dB IIP3 6GHz )-2.74dBm-6dBm P -1dB 6GHz )-16.27dBm-15dBm Power consumption15.6mW12mW Very similar results have been obtained.

Conclusions  A two-stage LNA amplifier from 1.0 and up to 11.6GHz has been designed.  A common-gate stage fixes the input impedance of the system and creates a first resonance at low frequencies.  A common-source stage drives the system gain and introduces a resonance in the high part of the band.  A nearly flat gain of 13dB and a noise figure of 4dB are achieved within this topology. 16

Thank you for your attention RFCS. Spring Josep Miquel Jornet Montaña 17