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Design Notes

LTE FDD Downlink Base Station TX Test Bench

This example demonstrates:

LTE FDD Downlink 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

� MCS: modulation and coding scheme (change in LTE_DL_TSIG block parameters). Entries with two options relate to the setting of parameter MTBST � the first entry corresponds to Table and the second one to Table

� N_RB_DL: number or resource blocks used for transmission

� Carrier Frequency (MHz)

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

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


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

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.