Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
2
Receiver Noise and Linearity
• Small signal linearity:
IIP2, IIP3
Y
XABAD
Operates here
GGD
fB1 fB22fB1-fB2• Large signal linearity:
Gain compression
• Reciprocal mixing
• Harmonic mixing
• Receiver NF sets the sensitivity, range:
Set by the standard10Log(KT), dBm/Hz
Sensitivity = -174 + NF + 10Log(BW) +SNRRS=50ΩΩΩΩ
RX
Blo
cke
rs: I
n/O
ut-
Ban
d
3
Reciprocal Mixing
• PB + PN(∆∆∆∆B) + 10×LOG(BW) = PD – SNR
• BNF = 174 + PB + PN
fLO
PD
PBSNR
BWfLO
Noisy LO
∆∆∆∆fB
4
Harmonic Rejection & Aliasing in Mixers
Weldon, JSSC 2001
• Square-wave LO harmonically rich
• More phases alleviates the issue
• More energy in main, less in higher harmonics
-6
-4
-2
0
2
2 4 8 16
32
# of Phases
Gai
n, d
B
)(M
SinM π
π
1.0
1.5
2.0
Alia
sin
g
=
1
1/31/5
Aliasing = 1+1/32+1/52+…= ππππ2/2
5
RF IC
Large Blocker
Duplexer
RX Desired
TX Leakage
3/4G Full-Duplex Problem
• Duplexer is a dual-band filter• Similar issue due to co-existence
TX RX
RX-Band NoiseIIP2IIP3
6
Ideal Receiver
fIF = fIN - fLO
ADCADC
IFfLO
RF
• Filter only rejects out-of-band blockers
• In-band blockers require a high-resolution ADC
• Power hungry
• Invented by Armstrong in 1918
• Down-conversion relaxes IF signal processing
• Lower power
-99dBm
0dBm-26dBm
Mitola 1995
7
Ideal Receiver Challenges
• Scalable
• Broad-band: Low-noise, Blocker tolerant
• Low-power
Murmann
97
03 09
15
Year (ADC)
FoM
Current RX
FoM = p/fs/2^ENOB
06
09
Year (3G RX)
I DD, m
A
30
50
70
12
BCM2093
Mikhemar
8
Narrow-Band Filtering Concerns
• Large blockers compress the receiver
• External filtering is narrow-band and costly
-99dBm
0dBm
Mu
lti-
Ban
d R
ece
ive
r
Swit
ch
15-20dB
6.6V p-p
9
N-Path Filtering Concept
• Very high-Q passives needed
• N-path filtering extends Nyquist rate1
SC LPF
fc 2fcfc/2
SC LPF
SC LPF
SC LPF
…… ………… ……
ININOUT
OUT
fc 2fc
NY=N×(fc/2)
L. Franks, Bell Syst. Tech. J., 1960
10
Passive Mixers as High-Q Filters
)()(2
)(2 LOBBLOBBSWin jsZjsZRsZ ωω
π++−+≈
LO1
LO2
LO3
LO4
0
IRF
VRF
0
High-Q BPF from low-Q LPF
fLO
fLO
LO1
LO4
0
LO2
LO3
VRF
IRF
ZBB
Mirzaei, TCAS 2010
Blo
cke
r
11
Current-Mode Receivers
• Passive mixers to achieve high-Q filtering
• Current mode LNA: LNTA
• Enhance the blocker tolerance
GM
0fRF
fRF
0
BUF
BUF
12
Front-End Matching Concerns
• Wide-band matching
• Good linearity
• NF suffers
RS=50ΩΩΩΩ
RS
• Narrow-band matching
• Good NF
• Modest linearity
NF > 3dB
Matching
RS
13
Mixer-First Receivers
• N = 1 / (sinc (ππππ/M))2 > 1
• NF > 3dB in practice at GHz frequencies Andrews, JSSC 2010
LO1
LO2
LO3
LO4TI
A_I
I
TIA
_Q Q
RS
VS
SW Resistance, ΩΩΩΩ
NF,
dB
0
1
2
3
4
5
0 10
20
30
40
50
gAlia
S
bb
S
DS NKTRM
v
R
ONrF
sin
2
)4(
)(1 ×
++=• For M phases:
14
Noise Cancelling Concept
• Used in broad-band LNA’s
• Poor linearity
RS
RIN=RS
VIN+- ααααVIN
+- -rmIIN
IIN
+VOUT
-
rm = αααα × RS
Relative GainN
F0
Bruccoleri, ISSCC 2002
15
Noise Cancelling RX Architecture
• Low noise and linear
• No Balun required
RS
RS = RSW + 2RBB/ππππ2
-+
BW << ∆∆∆∆fB
-+
GM αααα = -GM×RLA+
VOUT
-
Low resistance
Noise and linearity bottleneck
RLA
RLM
rm = RLM
Murphy, ISSCC 2012
16
Noise & Linearity Performance of NC RX
• GM noise dominant, no need to provide matching
F ≅≅≅≅ (1+vGM2/4KTRS)×N
• Similarly main path distortion cancelled:
IIP3 ≅≅≅≅ (1+RS/RIN)3/2 × IIP3_AUX
RS
GM+
VOUT
-
TIA_A
TIA_M
Suppressed by GM
Upconverts, Cancelled
Dominant
17
Over-Sampling Mixer Architecture
• Synthesizes arbitrary 8-phase LO:
TIA K0
TIA K1
TIA K7
ΣΣΣΣVOUT
…
IRF
8-P
has
e
√2
Harmonic Combination
∑=
−=7
0
)8
()(x
xRFOUTT
xtswKtiV
1
1/7
18
Complete NC Receiver Architecture
GM
10ΩΩΩΩ
50ΩΩΩΩ
I
Q
We
igh
tin
g &
Re
com
bin
atio
n
…LO0LO1
LO7
4fLO ÷4
NF ≈ 1 + 1/GMRS
19
RF GM Cell
• Class AB transconductance
• Scalable
• Linear due to class AB and low-impedance loading
0.0
0.1
0.2
0.3
-0.7
-0.5
-0.4
-0.2
0.0
0.2
0.3
0.5
0.7
GM
≈ 10ΩΩΩΩ
N P
Overall
VDD
GM
, S
2.7×
Input, V
1×
20
Baseband TIA
• Most power efficient
• Noise: vbb2 ≈ 4KTγγγγ/Gm ≈ 4KT/40ID
• Input resistance: Rin ≈ RF / AOPEN ≈ RF / (Gm(RFllRL))
0
5
10
15
20
25
1 4 13
44
143
464
151
2
492
4
Width, µµµµm
g m/I
D, V
-1
NMOSPMOS
Gm
RF
RL
Gm = gmn+gmp ≈ 40××××ID
Rin
vbb2
21
Receiver Scalability
VD
D
4tr
S××××T = 8VDD
• Inherently relies on high-speed logic, switches
• In 40nm, tr ≈ 10pS:
– 12.5GHz for 2-phase (overlapping)
– 3.12GHz for 8-phase
• Scales w/ technology
8-Phase
T = 32tr
VD
D
tr
3tr
tf
S××××T = 8VDD
2-Phase
T = 8tr
22
Noise Figure
• 1/f corner reduces from 100kHz to less than 10kHz
• Corresponds to <-113dBm GSM sensitivity
NC ON
NC OFF
NF,
dB
RF Input, MHz
23
Blocker Noise Figure
• 4.1dB 0dBm BNF, mostly limited by reciprocal mixing
BN
F, d
B
Blocker Power, dBm
3GPP Requirement
24
Linearity
• Close to 0dBm 1dB compression at maximum gain
NC ON
NC OFFP
1-d
B, d
Bm
Blocker Distance, MHz
25
NF vs. Relative Phase Correction
• Robust at optimum point
NF,
dB
Relative Phase, ⁰
Uncompensated
26
Summary of Performance
Architecture Mixer first NC LNA NB SAW-Less NC RX
RF Range 0.1-2.4GHz 0.4-6GHz 900/1800 0.1-2.7GHz
Input SE Differential Differential SE
NF at 2GHz 7dB 4.4dB 4.1dB 1.8dB
0dBm BNF NA 13dB 7dB 4.1dB
3rd/5th HR 35/43dB None None 42/45dB
OB IIP3 25dBm 10dBm NA 14dBm
RX Current 12mA 12mA 37mA 12mA
Area 2mm2 2mm2 1.4mm2 1.2mm2
Technology 65nm 40nm 65nm 40nm
28
Reciprocal Mixing Issue System Approach
• Start w/ a low-power/cost VCO
• Deal with its consequences in system level
• Proper phase noise estimation is key
Receiver Chain
Noisy VCONoise
Estimation
-Desired + RM
RM Replica
Desired
Reciprocal mixing NF = 174 – PB -PN
34
Measured Blocker Noise Figure
• Blocker offset as low as 10MHz
• SS NF of about 2.4dB
Blo
cker
NF,
dB
5
15
25
35
-25 -20 -15 -10Blocker Power, dBm
19dB
Effective LO FoM=188dB
After
Before
Before, Ideal LO
36
Receiver Architecture for Coexistence
• Second path to divert blocker away
• Relaxes noise and linearity of main receiver
LC-
matchGm
RXLO VCO/PLL
TIA/LPF
TIA/LPF
fRXfb
fRXfb
ZIN :
fRXfb
Short at fb
Open at fRX
Aux Path
Reciprocal mixing NF = 174 – PB -PN
37
N-Path Impedance Implementation
• Clocker by the aggressor TX LO
LO1
LO3
ZBB(s)
LO2
LO4
0
ZBB(f)
Zin(f)
fRXfb
Zin(f)
f
LO1
LO3
LO2
LO4
25% duty-cycle clocks @ fb
f-3dB,h (f-3dB,h << fb)
0f
TX Signal
38
Coexistence Receiver Architecture
LC-match
Gm
RXLO VCO/PLL
TIA/LPF
TIA/LPF
fRXfb
PRX
Pb
PRX
Pbfb fRX
H1(f)
Main path TF
LO @ fb
+
-TIA
TIA+
-fb fRX
Zin
fb fRX
H2(f)
Aux path TF
LO @ fRX
39
Measured Blocker Noise Figure
• NF > 25dB if Aux path de-activated
Blo
cker
NF,
dB
Blocker Power, dBm
Desired at 2GHz,Blocker at 1.9GHz
40
RX Performance Summary
[1] T. Sowlati, et al., "Single-chip multiband WCDMA/HSDPA/HSUPA/EGPRS transceiver with diversity receiver and 3G DigRF interface without SAW filters in transmitter / 3G receiver paths," ISSCC, 2010, pp. 116-117.[2] M. Nilsson, et al., "A 9-band WCDMA/EDGE transceiver supporting HSPA evolution," ISSCC, 2011, pp. 366-368.[3] Y. H. Chung, et al., "A 4-in-1 (WiFi/BT/FM/GPS) connectivity SoC with enhanced co-existence performance in 65nm CMOS,“ ISSCC, 2012.
Parameter [1] [2] [3] This work
NF, dB 2.5 2.5 4 1.7
OB IIP3, dBm -2.5 -4 -14 -2.5
OB IIP2, dBm > 50 58 N/A > 50
0dBm Blocker NF, dB N/A 13.5
Battery Current, mA 65 44 46 10
Total RX Area, mm2 6.7 3.4 2.2 0.93
Technology 130nm 90nm 65nm 40nm
Application Cellular Cellular WiFi Generic