6.10 Intra Base Station System intermodulation attenuation,
PCS 1900, GSM 850 and GSM 700

3GPP51.021Base Station System (BSS) equipment specificationRadio aspectsRelease 17TS

6.10.1 Test purpose

To verify that the level of intermodulation products produced inside the RX and TX bands (due to the leakage of RF power between transmitters that are operating in close vicinity of each other inside the BSS, or are combined to feed a single antenna) do not exceed the specified limit.

6.10.2 Test case

If SFH is supported by the BSS, it shall be disabled during this measurement.

The BSS shall be configured with a full compliment of transceivers. Each RF transmit equipment shall be operated at the maximum power specified (Highest Static Power Control Level subclause 6.3) and with modulation of a pseudo random sequence applied.

For multicarrier BTS the tests shall be performed per antenna connector for the lowest supported number of carriers (≥ 2) and the declared maximum number of carriers transmitting on equal maximum power according to the power declaration for each configuration.

In the relevant transmit band, the intermodulation components shall be measured at frequency offsets above the uppermost and below the lowermost carrier frequencies.

All intermodulation product frequencies in the relevant TX band and operating RX band shall be identified and measured according to the process below.

For measurements in the relevant TX band excluding multicarrier BTS

The equipment shall be operated at equal and minimum carrier frequency spacing specified for the BSS configuration under test.

For frequency offsets 0.6 to 1.8 MHz the intermodulation product power shall be measured selectively using video averaging over 50 to 90 % of the useful part of the time slot excluding the mid‑amble. The averaging shall be over at least 200 time slots and only active bursts shall be included in the averaging process. The RF and video filter bandwidth of the measuring instrument shall be 30 kHz.

For frequency offsets above the uppermost and below the lowermost carrier frequencies of more than 1.8 MHz the average power of any intermodulation components shall be measured with a bandwidth of 300 kHz, zero frequency span, over a time slot period. . The reference power for relative measurements is the power measured in a bandwidth of at least 300 kHz for the TRX under test In the operating RX band the power of any intermodulation components shall be measured with a filter and video bandwidth of 100 kHz, frequency scan mode, minimum sweep time of 75 ms and averaged over 200 sweeps.

For measurements in the relevant TX band for multicarrier BTS

The tests are performed according to subclause 6.12.

For the measurement in the operating RX band

The equipment shall be operated with ARFCNs such that the lowest order intermodulation product falls into the operating receive band. The measurement shall be carried out at the antenna connector of the BSS, using a frequency selective instrument.

A possible measurement set‑up for this test is shown in annex B.2.

For measurements in the RX band the following is the test set up:

A filter and video bandwidth of 100 kHz.

Frequency scan mode.

Minimum sweep time of 75 ms and averaged over 200 sweeps.

6.10.3 Void

6.10.4 Conformance requirement

Test Environment

Normal.

Minimum requirement

For measurements in the operating RX band

In the operating receive band the measured intermodulation components shall never exceed the values given in table 6.8-1 under normal test conditions.

For measurements in the relevant TX band

i) For BTSs not belonging to a multicarrier BTS class

In the relevant transmit band, at offsets greater than 0.6 MHz and up to 1.8 MHz, the requirements are those specified in subclause 6.5.1, Continuous Modulation Spectrum except that for offset 1.2 MHz to 1.8 MHz the measured power shall not exceed the requirements specified in subclause 6.5.1 or –70 dBc whichever higher. The exceptions given there shall also apply.

In the relevant transmit band for offsets greater than 1.8 MHz the measured power shall not exceed –70 dBc relative to the per carrier power or –46 dBm whichever is the higher.

ii) For BTS belonging to a multicarrier BTS class

In the relevant transmit band, the requirements in subclause 6.12.4 apply.

6.10.5 Requirement reference

3GPP TS 45.005 subclause 4.7.2.