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Design Notes

LTE TDD Uplink User Equipment TX Test Bench

This example demonstrates:

            LTE TDD Uplink TX, compliant with 3GPP specifications.

            Specification document: TS 36.104, TS 36.211, TS 36.212

Configurable options include:

• NFramesSweep: number of 10ms frames used in each sweep

• FrameType: frame type and cycling preffix:

            - 0: Frame structure type 1 / Normal CP: FDD

            - 1: Frame structure type 2 / Normal CP: TDD

            - 2: Frame structure type 1 / Extended CP: FDD

            - 3: Frame structure type 2 / Extended CP: TDD

• Carrier Frequency (MHz)

• TxOutLvlStart, TxOutLvlSpan, TxOutLvlStep (dBm): Define swept power of transmitted signal

• N_RB_UL: number or resource blocks used for transmission

• State of each uplink PUSCH channel (up to four users currently supported, more users may be easily added)

• N_RB_Channel: number or resource blocks used by each user

• ModType_Channel: modulation type used by each user (QPSK, 16QAM, 64QAM)

• UL_DL_Config: Uplink/Downlink Configuration for TDD (0, 1, 2, 3, 4, 5 or 6)

• PTS_Format: Pilot Time Slot Format for TDD (0, 1, 2, 3, 4, 5, 6, 7 or 8)

The test bench can be used to monitor:

• The CCDF at the input and output of DUT.

• The TX signal spectrum at the input and output of DUT

• EVM %rms vs. output power

• The impact of phase noise on EVM

• The impact of phase/amplitude and DC offset on EVM

• ACPR

N_RB_UL defines the channel bandwith as defined in the specifications (See Global Definitions for relationship between N_RB_UL and channel BW).

4 PUSCH channels (users) can be activated individually. Each PUSCH can be assigned an arbitrary number of resource blocks. The sum of assigned resource blocks should be less or equal to N_RB. More PUSCH channels may be added to the system.

Note that the amplifier model is based on a text data file. It can be replaced with an MWO circuit or a VSS behavioral amplifier model that accounts for frequency dependency. This test bench is used to illustrate several capabilities of VSS.

This example can be used to test a PA's error vector magnitude (EVM) performance vs. output power.

A reference IQ plot versus the measured IQ plot is shown. EVM measurements are calculated for each power level and plotted in the "EVM vs. Output Power" graph.

Please read the online help for information on any of the blocks that are used in the system diagrams. In addition, please read the online help for ACPR and EVM measurements.

System Diagram - LTE UL

Graph - ACPR

Graph - EVM

DB(EVM(VSA.EVM,1,1,1,12,1,0,1,0,1,1,10,0,0,0,0,0)) (us) LTE UL Time DB(EVM(VSA.EVM,1,1,1,12,1,0,1,0,1,1,10,0,0,0,0,0)) LTE UL
4110.48 -35.653

Graph - Power Levels

x Data (Unitless) DB(PWR_MTR(TP.DUT_in,1,0,1,0,0,1,0,1,0,0,1000,0,10,0,-1,0,-1,0,0.5,0,0,0))[x] (dBm) LTE UL DB(PWR_MTR(TP.DUT_out,1,0,1,0,0,1,0,1,0,0,1000,0,10,0,-1,0,-1,0,0.5,0,0,0))[x] (dBm) LTE UL DB(PWR_MTR(S1\S1\TP.ModOut1,1,0,1,0,0,1,0,1,0,0,1000,0,10,0,-1,0,-1,0,0.5,0,0,0))[x] (dBm) LTE UL DB(PWR_MTR(S1\S1\TP.ModOut2,1,0,1,0,0,1,0,1,0,0,1000,0,10,0,-1,0,-1,0,0.5,0,0,0))[x] (dBm) LTE UL
0 -8.80876 2.99405
1 -7.80876 3.99401
2 -6.80876 4.99338
3 -5.80876 5.98986
4 -5.37367 6.43036
5
6
7
8
9
10

Graph - EVM vs Output Power

Graph - CCDF

Graph - IQ Constellation

Graph - AM to AM

Graph - Spectrum