6.6 Transmitter intermodulation

25.1413GPPBase Station (BS) conformance testing (FDD)Release 17TS

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

6.6.1 Definition and applicability

The transmitter intermodulation requirement 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.

The transmitter intermodulation level is the power of the intermodulation products when a WCDMA interfering signal is injected into an antenna connector at a power level of 30 dB lower than the rated total output power in the operating band.

For BS capable of multi-band operation where multiple bands are mapped on separate antenna connectors, the single-band requirements apply regardless of the interfering signals position relative to the Inter RF Bandwidth gap.

For multi-carrier operation, the interfering signal offset is defined relative to the lower/upper edge of the wanted signal or edge of sub-block inside a gap.

The interfering signal frequency offset shall be as in Table 6.48.

Table 6.48 Interfering signal frequency offset

Parameter	Value
Interfering signal centre frequency offset from the wanted signal centre frequency	-5 MHz -10 MHz -15 MHz +5 MHz +10 MHz +15 MHz
Interfering signal centre frequency offset from the lower/upper edge of the wanted signal or edge of sub-block inside a gap	-2.5 MHz -7.5 MHz -12.5 MHz +2.5 MHz +7.5 MHz +12.5 MHz
NOTE 1: Interfering signal frequencies that are outside of any allocated frequency band for UTRA-FDD downlink specified in clause 3.4.1 are excluded from the requirement, unless the interfering signal positions fall within the frequency range of adjacent downlink operating bands in the same geographical area. NOTE 2: In certain regions, NOTE 1 is not applied in Band I, III, VI, VIII, IX, XI, XIX, XXI, and XXXII operating within 1475.9-1495.9MHz.

6.6.2 Minimum Requirement

The minimum requirement is in TS 25.104 [1] clause 6.7.

6.6.3 Test purpose

The test purpose is to verify the ability of the BS transmitter to restrict the generation of intermodulation products in its non linear elements caused by presence of the wanted signal and an interfering signal reaching the transmitter via the antenna to below specified levels.

6.6.4 Method of test

6.6.4.1 Initial conditions

Test environment: normal; see clause 4.4.1.

RF channels to be tested for single carrier: B, M and T; see clause 4.8

Base Sation RF Bandwidth positions to be tested for multi-carrier: B_RFBW, M_RFBW and T_RFBW in single band operation; see subclause 4.8.1.

1) Test set-up in accordance to annex B.

6.6.4.2 Procedures

1) For a BS declared to be capable of single carrier operation only, set the base station to transmit a signal according to TM1, clause 6.1.1.1 at manufacturer’s declared rated output power, Prated,c.

For a BS declared to be capable of multi-carrier operation, set the base station to transmit according to TM1 on all carriers configured using the applicable test configuration and corresponding power setting specified in sub-clause 4.12.

2) Generate the interfering signal in accordance to TM1, clause 6.1.1.1 with a frequency offset of according to the conditions of Table 6.48 but exclude interfering signal frequencies that are outside of the allocated downlink operating band or interfering signal frequencies that are not completely within the sub-block gap or within the Inter RF Bandwidth gap.

3) Adjust ATT1 so the level of the WCDMA interfering signal is as defined in clause 6.6.5.

4) Perform the out of band emission test as specified in clause 6.5.2, for all third and fifth order intermodulation products which appear in the frequency ranges defined in clause 6.5.2. The width of the intermodulation products shall be taken into account.

5) Perform the spurious emission test as specified in clause 6.5.3, for all third and fifth order intermodulation products which appear in the frequency ranges defined in clause 6.5.3. The width of the intermodulation products shall be taken into account.

6) Verify that the emission level does not exceed the required level with the exception of interfering signal frequencies.

7) Repeat the test for the remaining interfering signal centre frequency offsets according to the conditions of Table 6.48.

In addition, for a multi-band capable BS, the following step shall apply:

8) For multi-band capable BS and single band tests, repeat the steps above per involved band where single band test configurations and test models shall apply with no carrier activated in the other band. For multi-band capable BS with separate antenna connector, the antenna connector not being under test shall be terminated.

NOTE: The third order intermodulation products are (F1±2F2) and (2F1±F2), the fifth order intermodulation products are (2F1±3F2), (3F1±2F2), (4F1±F2), and (F1±4F2), where F1 represents the wanted signal centre frequenyc or centre frequency of each sub-block and F2 represents the interfering signal centre frequency. The widths of intermodulation products are

● (n*BW_F1+ m*5MHz) for the nF1±mF2 products

● (n*5MHz + m* BW_F1) for the nF2±mF1 products

where BW_F1represents the wanted signal RF bandwidth, or channel bandwidth in case of single carrier, or sub-block bandwidth.

6.6.5 Test Requirements

In the frequency range relevant for this test, the transmit intermodulation level shall not exceed the out of band emission or the spurious emission requirements of clauses 6.5.2 and 6.5.3 in the presence of a WCDMA interfering signal with a power level 30 dB below the rated total output power in the operating band.

For a BS operating in non-contiguous spectrum, the requirement is also applicable inside a sub-block gap for interfering signal offsets where the interfering signal falls completely within the sub-block gap. The interfering signal offset is defined relative to the sub-block edges.

For a BS capable of multi-band operation, the requirement is also applicable inside an Inter RF Bandwidth gap for interfering signal offsets where the interfering signal falls completely within the Inter RF Bandwidth gap. The interfering signal offset is defined relative to the Base Station RF Bandwidth edges.

The measurements for out of band emission or spurious emission requirement due to intermodulation can be limited to the frequency ranges of all third and fifth order intermodulation products, considering the width of these products and excluding the bandwidths of the wanted and interfering signals.

NOTE: If the above Test Requirement differs from the Minimum Requirement then the Test Tolerance applied for this test is non-zero. The Test Tolerance for this test is defined in clause 4.2 and the explanation of how the Minimum Requirement has been relaxed by the Test Tolerance is given in Annex F.