05 radio system design 3

Bhaskar Banerjee, EERF 6330, Sp2013, UTD

Radio System Design III

Link Budget Analysis: Derivation of Specifications

Prof. Bhaskar Banerjee

EERF 6330- RF IC Design


System Analysis/Specification Derivation

ETSI/3GPP Specifications (www.3gpp.org) Link budget analysis for the Receiver Target Standard: W-CDMA

PCS band (Band II) RX band: 1930 MHz - 1990 MHz TX band: 1850 MHz - 1910 MHz TX channel is always 80 MHz lower in frequency compared to

the corresponding RX channel

2

Ref: N. Yanduru, PhD Dissertation Thesis, University of Texas at Dallas, 2007.

NF = FO 10 log10(B)G 10 log10(kT )

IIP3 =3

2Pin 1

2PIM3,in = Pin +

1

2IMD3

Pin =23P1 +

13P2


Important System Formulae

What if blockers are un-equal in power? P1 closer to fin_band and P2 away from fin_band

3

IIP2:

Dynamic Range:


Phase Noise and Reciprocal Mixing

Major cause of receiver performance degradation in the presence of close-in blockers

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Reference Sensitivity Test

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[1] 3GPP TS 25.101 (www.3gpp.org)[2] A. Springer, et. al, "RF system concepts for highly integrated RFICs for W-CDMA mobile radio terminals," Microwave Theory and Techniques, IEEE Transactions on, vol. 50, pp. 254-267, 2002.

[2]

[1]


PN+I

Thermal noise at the receiver circuit (Pnoise_floor) TX Leakage:

Reciprocal Mixing with LO Phase Noise TX is AM modulated with 3.84 MHz BW

2nd order distortion product at DC w/ overall BW of 7.68 MHz TX o/p noise at RX

Needs to be allocated in the budget

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NF of the RX Chain

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Calculate the required NF!


Phase Noise Requirement

Based on the budget for reciprocal mixing:

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Based on the allocation for the 2nd order (IM2):where,

is and adjustment factor as the TX leakage is amplitude modulated along with other considerations such as accounting only for the distortion power that falls inside the received signal bandwidth.

For the 3GPP standard for WCDMA, Adj(N) = -10.8 dB (N=1)


In-Band Blocker Test

Can be present anywhere beyond 15 MHz offset from the center of the RX channel

Within the specified RF band (e.g. 1930-1990 MHz) Distortions in addition to the ones in the Reference Sensitivity Test

i/p signal as 3 dB higher than the ref sensitivity test (-103.7 dBm) i/p referred noise is also higher (-96 dBm)

Target SNR: -7.7 dB TX output power less by 3 dB (-33 dBm)

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In-band Blocker Test

Two scenarios: Blocker located halfway b/w RX and TX: FBLK = (FRX+FTX)/2 Reciprocal mixing from the blocker

In this case, PBLK:IBB = -44 dBm (much smaller to TX leakage of -33 dBm) -- negligible

PIM3 can be allocated the entire 3 dB extra signal

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In-band Blocker Test

The above formula is derived based on the AM characteristics of the blocker and the amount of distortion that falls inside the signal bandwidth of interest

11

= -11.4 dBm


Out-of-Band Blocker Test

the blockers farthest away from the channel are highest in power while the blockers closest to the RF band are lowest in power.

the duplexer or pre-select filter rejects most of these blockers except the ones closest to the band which do not get much rejection from the duplexer.

a 3 dB extra input signal is provided as compared to the Reference Sensitivity Test case

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a third order intermodulation scenario: 2FBLK - FTX = FRX will also be present RX channel is at the lower edge of the RX frequency band, an out-of-band

blocker at FBLK = (FTX +FRX)/2 and TX leakage will cause third order intermodulation

The blocker power as defined in the test is -44 dBm at the antenna; assuming a 10 dB filtering from the duplexer filter for this blocker, we use PBLK:OBB = - 54 dBm

This blocker contributes very little from reciprocal mixing (in comparison to the reciprocal mixing from TX leakage, PTX:OBB of -33 dBm)

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14

= -10.7 dBm


Adjacent Channel Selectivity Test

defines the power of the adjacent channel which is located at +/-5 MHz offset from the center of RX channel

adjacent channel can cause receiver impairments such as reciprocal mixing and second order intermodulation in the RF section of the receiver

close to the channel of interest and hence is difficult to filter The Adjacent Channel Selectivity Test defines two test cases:

ACS-Cases 1 and 2 difference between the two cases is the power of the adjacent

channel and the input signal power at the receiver input

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ACS - Case 1

PBLK:ACS1 = -52 dBm at the antenna the required signal power at the antenna is 14 dB higher than

in the case of Reference Sensitivity Test (Ior,ACS1 = Ior,RS + 14 = -92.7 dBm)

considerable increase in noise/distortion power can be tolerated compared to Reference Sensitivity Test case for the same output SNR performance

SNR req = -7.7 dB the total allowed distortion power (PN+I:ACS1):

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ACS - Case 1

Noise and Distortion Component: Cross modulation distortion between TX leakage and adj channel Reciprocal mixing Spectral re-growth of adj channel into the RX channel Increase in thermal noise due to reduced RX gain

the allowed cross modulation distortion noise (PIM3:ACS1):

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ACS - Case 1

N is the number of channels in the W-CDMA TX leakage u is a parameter that depends on the amount of overlap in the RX channel

bandwidth and cross modulation distortion component

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Substituting this value of u and using N =1 , results in adjustment factor of -8.3 dB using PTX:ACS1 of -33 dBm, PBLK:ACS1 of -52 dBm and PIM3 of -85.5 dBm results in

IIP3 requirement of -20.4 dBm


ACS - Case 2

both the input required signal and the adjacent channel power are higher than in the case for ACS-case1

blocker power at the antenna for this test case is -25 dBm required signal is a whopping 41 dB higher than in the case for Reference

Sensitivity Test case Since the input signal power is significantly higher in this case, the receiver

gain is significantly lower than in the test cases discussed so far this test results in setting specification for the receiver performance under

low gain conditions (about 40 dB below the maximum receiver gain) these specifications are normally not as challenging as compared to the

specifications in the high gain mode of the receiver. this test case will be used to illustrate the significance of PAR of the

modulated blocker in determining the distortion Higher number of channels in the AM blocker results in higher PAR which

in turn increases the magnitude of Adjustment Factor

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ACS - Case 2 difference in the spectral re-growth at the output of RF receiver for the

cases where the adjacent channel had only one channel (low PAR) and 16 channels (high PAR)

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Spectrum after down-conversion, in the presence of adjacent channel with low PAR

Spectrum after down-conversion, in the presence of adjacent channel with high PAR


Broadband Intermodulation Test

the blockers (FBLK1, FBLK2) are 10 MHz and 20 MHz offset from the center of the RX channel

the input signal provided is again 3 dB higher than the Reference Sensitivity Test case

this test also sets an IIP3 requirement for the RF receiver the allowed noise power, PN+I:BBI = -99 + 3 = -96 dBm

PBLK:10MHz and PBLK:20MHz are the blocker powers at antenna, each of -46 dBm and PIM3:BBI is -99 dBm as mentioned earlier

IIP3 can be calculated to be -19.5 dBm

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Consolidated Specifications

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ADC Specifications

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