IEEE802.15.4 (ZigBee) 2 4 GH 사양분석2.4 GHz 사양분석

2015년 2월 6일부산대학교부산대학교

남일구

IEEE802.15.4 (ZigBee) 2.4 GHz Sensitivity

IEEE Std 802.15.4 2.4 GHz Sensitivity spec. : < -85 dBm

Noise floor [dBm] - 173.8 + 10log(B.W.) - 173 8 + 10log(3 106) = -109 dBm - 173.8 + 10log(3 10 ) = -109 dBm

where B.W. = 3 MHz (99% B.W.)

SNR t t [dB] (when PER=10-2) SNRoutput [dB] (when PER=10 )= Eb / No [dB] – Rc / Rb (processing gain) [dB]

= 14 – 9.03 = 4.97 dB ( from modem simulation )( )

Sensitivity of receiver [dBm] = Noise floor + NFReceiver + SNRoutput < -85 dBm

NFReceiver < -85 +109 - 4.97 = 19.03 dBm

1

Sensitivity – Theoretical Limit

2 2

bb bi

EP Q Q SNR

Performance of an ideal coherent O-QPSK detector

N = 20 octets 8 bits/octet 2 2

b bito

P Q Q SNRN

[ / ]1 (1 ) 2 N bits packetb b bitPER P N P N Q SNR

N 20 octets 8 bits/octet= 160 [bits/packet]PER = 1% = 0.01

E

PG = 10log108= 9.03 dBQ(3.8) = 0.000072348 = 1/13822.0738

2

min

0.01 3.92 , 8.8dB 2

b

bit bito

EQ SNR SNRN N

10min

0.20 31 log

cchip bit

o

ESNR SNR PGN

dB

Sensitivity lower bound

Q(3.9) = 0.000048096 = 1/20791.6011

174 10log(3 ) 109NoiseP dBm MHz dBm

109 23P P S BN d mR

Sensitivity lower bound

109.23S Noise chipP P S BN d mR

802.15.4 reference sensitivity : -85 dBm

802.15.4 standard allows a max. implementation loss of “24 dB”

2

Sensitivity - Budget Implementation loss budget

RFPartLoss

RF/AnalogLoss

DigitalLoss

2dB 7dB 6dB+ + = 15dBLow-bit ADC (4-bit)

Carrier freq./timing errorLow-complexity detector

Low-power RF/Analog

Circuits

AntennaRF BPF

T/R switch ? o co p e y de ec oC cu s/ s c

Our target sensitivity : - 93 dBm

Radio NF = 2 + 7 = 9 dB

Detector min. Eb/No = 9 + 6 = 15 dB for 1 % PERSNR = Ec/No ~ 6 dB

3

Blocking Profile and Intermodulation of ZigBee- 55dBm- 55dBm

30dB

Single interference signal (relatively low traffic envisioned for the WPAN service)

- 85 dBm- 85 dBm

30dB

- 85 dBm Loose filter attenuation specification Loose image rejection specification Therefore, low-IF receiver may be

fo(Wanted channel)

fo + 5fo 5 fo + 10 fo + 15fo - 10fo - 15 [ MHz ]

Therefore, low IF receiver may be suitable for ZigBee receiver

N i t d l ti ifi ti i No intermodulation specification in IEEE802.15.4 Std 2.4 GHz band

dBmdBmdBm 38)93(55

dBmdBmdBmIIP 36)2/(553

4

Selectivity – Intermodulation (IM3) Not specified in IEEE 802.15.4 From interferer profile

SIG IM3 min marginP P SNR INTP

SIGPIM3 INT 33 2P P IIP

INT SIG /P P C I marginSNR

/ 30C I dB

+2CH +4CH

IM3Pmin marginSNR

+2 CH +4 CH

min3 SIG

3 margin/ orSNRIIP P C I 3 SIG / or

2 2IIP P C I

min3 INT

1 margin/ 362 2

SNRIIP P C I dBm2 2

5

Selectivity – Channel Select Filter (CSF) Interferer (blocker) profile

BW(SSB)

CSF requirement

-10dBc@5MHz-40 dBc@10MHzSNR > 5dB

( )1.5MHz

A low-power 3rd?/4th? order SNR 5dB+ margin

pcomplex BPF is sufficient for this application

6

Selectivity – LO Phase Noise Requirement-30 dB

C/I

0 dBc

5 MHz 10 MHz

LO phase noise mask

min

65dB 10dB5dB

10log BW margin [dBc/Hz]

f

PN C I SNR

p

-80dBc/Hz PN of a sub-mA CMOS LC VCO

-100 dBc/Hz

-112 dBc/Hz-6 dB/oct-110dBc/Hz

7.5MHz

2 4 1 3 [MHz] 10

7.5MHz

8

ZigBee ADC Requirementge ADC headroom ( ~ 3 dB )

Maximum level of desired signal

ic ra

ng

Max. power difference between desired signal and interferer without filter = 30 dB

( )

dyna

m

g

( for example, 0 dB when 30 dB of filter rejection )

AD

C d

Noise margin (~ 9 dB)Noise from A/D

Noise from receiver + KTB

# of bit /o filter DR [dB] / 6 02 42 / 6 02 7 bit

A

# of bit w/o filter = DR [dB] / 6.02 = 42 / 6.02 = 7 bit

# of bit with 30 dB rejection of filter = DR [dB] / 6.02 = 2 bit

I dditi # f bit d d d f

9

In addition, # of bit depends on modem performance

→ 4-bit ADC is enough

Error Vector Magnitude (1)

),( jj QI )~,~( jj QI

),( jj QI

2 2

2 2

( )I QEVM

I Q

For applications (like WCDMA) requiring a wide gain control range a severe For applications (like WCDMA) requiring a wide gain control range, a severe drawback of direct up-conversion transmitter is carrier leakage

Carrier leakage can violate EVM and power accuracy requirement and limitCarrier leakage can violate EVM and power accuracy requirement and limit channel control

ZigBee does not require a wide gain control range

10

ZigBee EVM < 35%Ref) G. Brenna et al, ‘A 2-GHz carrier leakage calibrated direct-conversion WCDMA transmitter in 0.13-m CMOS,’ JSSC, 2004

Error Vector Magnitude (2)EVM [%]

120EVM [%]

140

0.75

1

1.25

1.5

100

120

0 75

1

1.25

1.5

120

140

0

0.25

0.5

0.75

erro

r [ra

d]

60

80

0

0.25

0.5

0.75

erro

r [ra

d]

80

100

-0.75

-0.5

-0.25

Phas

e

40

-0.75

-0.5

-0.25

Phas

e e

40

60

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5-1.5

-1.25

-1 20

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5-1.5

-1.25

-1

N li d lit d [ 100%]

20

Normalized amplitude error [x100%] Normalized amplitude error [x100%]

22

2 CC AA

I-path : amplitude error and phase error I-path : amplitude error, Q-path : phase error

[%]1001)sin(cos)1(2

1

C

C

AAEVM [%]1002

)1sin(cos2

2

C

CC

A

AA

EVM

11

Amplitude error < 20%, Phase error <20°, Carrier leakage < -20 dBc for EVM <30% Therefore, direct up-conversion transmitter is suitable for ZigBee transmitter

Transmission PSD Mask

Transmit PSD limits

Frequency Relative limit Absolute limit

| f f | 3 5 MH 20 dB 30 dB| f – fc | > 3.5 MHz - 20 dB - 30 dBm

For both relative and absolute limit average spectral power shall be For both relative and absolute limit, average spectral power shall be measured using a 100 kHz resolution bandwidth.

For relative limit reference level shall be the highest average spectral For relative limit, reference level shall be the highest average spectral power measured within +/- 1 MHz of fc.

From this specification # bit of DAC and harmonic distortion in a transmitter From this specification, # bit of DAC and harmonic distortion in a transmitter can be estimated

4-bit DAC and 1st LPF are proper.

12

4 bit DAC and 1st LPF are proper.

Harmonic distortion < -30 dBc

Transmission PSD Mask (Cont.)101

Spectrum mask 101

Spectrum mask

10-2

10-1

100

Spect u as

10-2

10-1

100

Spectrum mask

10-4

10-3

10

10-4

10-3

10

Ideal ZigBee spectrum-8 -6 -4 -2 0 2 4 6 8

x 106

10-6

10-5

-8 -6 -4 -2 0 2 4 6 8

x 106

10-6

10-5

ZigBee spectrum after 4 bit DACIdeal ZigBee spectrum ZigBee spectrum after 4-bit DAC

10-1

100

101

10-3

10-2

10

4-bit DAC and 1st LPF are proper

Harmonic distortion < -30 dBc10-6

10-5

10-4

13

Harmonic distortion 30 dBc-8 -6 -4 -2 0 2 4 6 8

x 106

10

ZigBee spectrum after 4-bit DAC and 1st LPF (2 MHz B.W.)

BER Performances

0 01

0.10.1

1E-3

0.01

BER

-20 dBc of carrier leakage

0.01

BER

1E 5

1E-4

20 dBc of carrier leakage -25 dBc of carrier leakage -30 dBc of carrier leakage No carrier leakage

1E-3 Ideal ZigBee signal ZigBee signal through 4-bit DAC

and LPF with 3dB B.W. of 2 MHz

BER according to carrier leakage

0 2 4 6 81E-5

Eb/No [dB]0 1 2 3 4 5 6 7

1E-4

Eb/No [dB]

BER when 4 bit DAC and LPF BER according to carrier leakage BER when 4-bit DAC and LPF with 3 dB B.W. of 2 MHz is used

14

Summary

Rx

Low-IF receiver architecture

Target sensitivity : -93 dBm (variable)

NF < 7 dB, IIP3 > -30 dBm, Max handling power : -20 dBm, , g p

3th/4th variable gain complex bandpass filter

4-bit ADC4 bit ADC

Tx

Direct-up conversion architecture Direct up conversion architecture

Harmonic distortion < -30 dBc

1th/2nd LPF 1th/2nd LPF

4 bit DAC

Linear drive amplifier (class A class AB)

14

Linear drive amplifier (class A, class AB)