TD-SCDMA UE RF Conformance Testing and Measurements

This tutorial covers TD-SCDMA baseband and RF measurements useful for UE conformance testing. The following basic TD-SCDMA UE transmitter and Receiver tests are performed during TD-SCDMA UE testing. Transmitter and receiver specifications vary for 3.68Mcps, 1.28Mcps, and 7.68Mcps TDD versions of TD-SCDMA.

Note that they all have different channel spacings: 3.68Mcps has 5 MHz channel spacing, 1.28Mcps has 1.6MHz, and 7.68Mcps has 10MHz channel spacing.

TD-SCDMA UE Transmitter

The following TD-SCDMA measurements are carried out on the UE transmitter part during TD-SCDMA testing.

Maximum Output Power

This test ascertains that the UE fulfills the requirements for Maximum Output Power as per its power class. For the 1.28Mcps TDD option, UE maximum power output limits are specified below with tolerance, including power class:

Minimum TX Output Power

The goal of this test is to verify whether the UE works efficiently at the specified lower power levels. The requirement for Minimum Transmit Output Power is -49dBm (at mid, low, and high channels). This limit is for the 1.28Mcps TDD version. For 3.84Mcps, it’s specified as -44dBm, and for 7.68Mcps, it’s -41dBm.

Open Loop Power Control

The requirements for Open Loop Power Control for a TD-SCDMA compliant UE are with a tolerance of +/-9dB under normal conditions and +/-12dB under extreme conditions.

Output Power Dynamics

This test helps check whether the UE fulfills the requirements on power control step tolerance. For a 1dB step, it should be between -0.5 and +0.5 dB. Different step sizes have different upper and lower limits.

UE Frequency Stability

The UE modulated carrier frequency shall be accurate to within +/-0.1 PPM observed over a period of one timeslot compared to the carrier frequency received from the BS.

Spectrum Emission Mask (SEM)

This test helps in verifying that the UE fulfills requirements on Spectrum Emission Mask. The Spectrum emission mask is measured at maximum output power under low, mid, and high channel conditions.

Spurious Limit

Spurious emissions and harmonics should be under control for the UE to perform well in the system. For the frequency band of 921MHz to 925MHz and with a 100KHz measurement bandwidth, the minimum requirement for spurious emissions is -60dBm. Other bands have different limits. This specification applies to the 1.28Mcps TDD version.

Adjacent Channel Leakage Power Ratio (ACLR)

This test helps in verifying that the UE fulfills requirements for Adjacent Channel Leakage Ratio (ACLR). ACLR and channel power are measured at the maximum power level under low, mid, and high channel conditions.

Modulation Accuracy

This test helps verify that the UE fulfills requirements on EVM (14%rms at -20 dBm Pout with Mid channel only and for 16QAM modulation), phase discontinuity and frequency error, PCDE(-21dB at High channel only) and IQ imbalance level.

TD-SCDMA UE Receiver

The following TD-SCDMA measurements are carried out on the UE receiver part during TD-SCDMA testing.

Receiver Sensitivity Level (RX EVM)

The EVM test with the lower power level is to verify that the UE fulfills requirements on receiver sensitivity.

EVM is measured in dB as shown in the equation:

$EVM = 10 \log_{10} \left( \frac{P_{\text{error}}}{P_{\text{ref}}} \right)$

Where $P_{\text{error}}$ is the RMS power of the error vector and $P_{\text{ref}}$ is the reference constellation average power. EVM of 14%rms with Mid channel at -20dBm P_out

RX RSSI Verification

The purpose is to test the RSSI from the UE with TD-SCDMA mode of operation. The power sweep will test that all analogue gain settings are functional, and the frequency sweep will test that the frequency response is sufficiently flat.

Power Sweep

Frequency Sweep