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Channel Power measurements are used to validate transmitter performance, verify compliance with FCC regulations, and keep overall system interference at a minimum. Out-of-specification power measurements indicate system faults in the power amplifier or in-filter circuits. Channel Power Measurement with the Site Master The Site Master can be used to measure CDMA signals in terms of channel power. It is necessary to use precise and specific settings to accurately measure the CDMA signal because the CDMA is different from CW signals. For accurate IS-95 CDMA measurements, use the following settings: • CDMA Channel Bandwidth: 1.23 MHz • RBW setting: 10 kHz • VBW . 3. RBW or at least 30 kHz • Averaging function turned off Required Equipment • Site Master Model S114C or S332C • 30 dB, 50 Watt, bi-directional, DC –18 GHz, N(m) – N(f), Attenuator • Test Port extension cable, Anritsu 15NNF50 – 1.5C Chapter 5 Spectrum Analyzer Measurements Procedure Using the test port extension cable and 30 dB attenuator, connect the Site Master to the RF_IN test port. The measurement can be accomplished with or without the 30 dB attenuator. The attenuator is recommended for additional protection. Step 1. Press the ON/OFF key on the Site Master. Step 2. Press the MODE key. Step 3. Use the Up/Down arrow key to select the Spectrum Analyzer mode and press ENTER. Step 4. Enter the following control settings: reference level = –15 dBm Scale = 10 dB/division RBW = 10 kHz VBW = 30 kHz or greater Span = 2.5 MHz Step 5. Press the MEAS key. Step 6. Once in the MEAS menu, press the CHANNEL POWER soft key. Step 7. Select the center frequency by pressing the CENTER FREQ soft key and enter 900 MHz as the center frequency of the CDMA signal. Step 8. Select the integration bandwidth by pressing the INT BW soft key and enter 1.23 MHz for the integration bandwidth. Step 9. Select channel span by pressing the CHANNEL SPAN soft key and enter 1.23 MHz as the desired integration bandwidth. Step 10. Make the measurement by pressing the MEASURE soft key. The Site Master will display the measurement results in the display area. Integration bandwidth is defined as the frequency span in which the spectrum analyzer integrates measured power readings. Channel span is the frequency range the analyzer sweeps. Channel span must be set to equal or greater than the integration bandwidth, or the Site Master will by default set the channel span equal to the integration span. The Site Master also keeps the ratio of the integration bandwidth to channel span constant. For example, if the channel span is doubled, the Site Master will double the integration span. When the integration bandwidth and channel span are set to the same value, the Site Master provides the most accurate measurement, as it uses all the sampling points for integration. Chapter 5 Spectrum Analyzer Measurements Adjacent Channel Power Measurement Another common transmitter measurement is that of adjacent channel power ratio. This is defined as the ratio of the amount of leakage power in an adjacent channel to the total transmitted power in the main channel. The current trend is to use this measurement to replace the traditional two-tone intermodulation distortion (IMD) test for system non-linear behavior. The specification for ACPR requires comparing the power in the RF channel to the power at several offset frequencies. The result can be expressed either in power ratio or power density. In order to calculate the upper and lower adjacent channel values, the Site Master requires four parameters: • Main channel center frequency • Main channel bandwidth • Adjacent channel bandwidth • Channel spacing 1.98 MHz 1.98 MHz 885 kHz 885 kHz 1.23 MHz 30 kHz Figure 5-1. Example ACPR Specification Required Equipment • Site Master Model S114C or S332C • 30 dB, 50 Watt, bi-directional, DC –18 GHz, N(m) – N(f), Attenuator • Test Port extension cable, Anritsu 15NNF50 – 1.5C Procedure Step 1. Using the test port extension cable and 30 dB attenuator connect the Site Master to the appropriate transmitter test port. The measurement can be accomplished with our without the 30 dB attenuator. The attenuator is recommended for additional protection. Step 2. Press the ON/OFF key on the Site Master. Chapter 5 Spectrum Analyzer Measurements Step 3. Press the MODE key. Step 4. Use the Up/Down arrow key to select the Spectrum Analyzer mode and press ENTER. Step 5. Select the appropriate reference level, input attenuation level, resolution bandwidth, and video bandwidth. Step 6. Press the MEAS key. Step 7. Once in the MEAS menu, press the ACP soft key. Step 8. Select the center frequency by pressing the CENTER FREQ soft key and enter the desired center frequency. Step 9. Select the main channel bandwidth by pressing the MAIN CHANNEL BW soft key and enter the desired main channel bandwidth. For an IS-95 signal enter 1.23 MHz. Step 10. Select the adjacent channel bandwidth by pressing the ADJ CHANNEL BW soft key and enter the desired ad...

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