12 Output Intermodulation

25.1533GPPRelease 17TSUTRA repeater conformance testing (LCR TDD)

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

The transmit intermodulation performance is a measure of the capability of the transmitter to inhibit the generation of signals in its non linear elements caused by presence of the wanted signal and an interfering signal reaching the transmitter via the antenna.

12.1 Definition and applicability

The transmit intermodulation level is the power of the intermodulation products when a LCR TDD modulated interference signal is injected into the antenna connector at a mean power level of 30 dB lower than that of the mean power of the subject signal.

The requirement is applicable for downlink signals.

12.2 Minimum requirements

The frequency of the interference signal shall be 1.6 MHz, 3.2 MHz and 4.8 MHz offset from the subject signal. The Transmit intermodulation level shall not exceed the out of band or the spurious emission requirements of section 9.1 and 9.2.

12.3 Test purpose

The test purpose is to verify the ability of the repeater to restrict the generation of intermodulation products in the presence of a subject signal on the repeater input and output ports, and an interfering signal applied at the repeater output port.

12.4 Method of test

12.4.1 Initial conditions

1) A measurement system set-up is shown in annex A.

2) Connect a signal generator to the input port of the Repeater (wanted signal). Connect a signal generator to the circulator on the output port (interfering signal) and make sure the signal generator power is directed to the repeater output port.

3) Detection mode: True RMS.

12.4.2 Procedures

1) Set the Repeater to maximum gain.

2) Set the signal generator at the repeater input port (subject signal) to generate a signal in accordance to table 12.1, at the level which produce the manufacturer specified maximum output power at maximum gain.

Table 12.1: Parameters of the transmitted signal for transmit intermodulation testing

Parameter	Value/description
TDD Duty Cycle	TS i; I = 0, 1, 2, 3, 4, 5, 6: transmit, if i is 0,4,5,6; receive, if i is 1,2,3.
Time slots under test	TS4, TS5 and TS6
BS output power setting	PRAT
Number of DPCH in each time slot under test	8
Power of each DPCH	1/8 of Base Station output power
Data content of DPCH	real life (sufficient irregular)

3) Set the signal generator at the repeater output port (interference signal) to generate a signal in accordance to table 12.1, at the level producing signal power corresponding to 30 dB below the manufacturer specified maximum output power at the repeater output port with the specified frequency offset from the wanted signal.

4) Measure the emission at the specified frequencies with specified measurement bandwidth and note that the measured value does not exceed the specified value. Measurements in the band of the interfering signal shall be excluded. The measurements can be limited to the power of all third and fifth order intermodulation products.

5) Repeat from clause 3 until interference signals 1,6MHz, 3,2MHz and 4,8MHz frequency offset from the wanted signal has been tested. Note that interfering signals outside the UTRA-FDD allocated frequency band , as specifies in section 4.1. need not be tested.

12.5 Test requirements

The mean power level of the interference signal shall be 30 dB below the mean power level of the wanted signal.

At the frequencies of all third and fifth order intermodulation products, the Test Requirements for out of band and spurious emissions as specified in subclauses 9.1.5 (Spectrum emission mask),and 9.2.5 (Spurious emissions) shall be met.