Channel Power Measurement

Channel power measurement is one of most common measurements for a radio transmitter. This test measures the output power, or channel power, of a transmitter over the frequency range. Out-of-specification power measurements indicate system faults, which can be in the power amplifiers or in filter circuits. Channel Power measurements can be used to validate transmitter performance, comply with government regulations, or to keep overall system interference at a minimum.

Frequency and span settings for many signal standards can be set.

1.	Press the Freq main menu key.

2.	Press the Signal Standard submenu key. Choose the desired standard and press Enter.

3.	Press the Channel # submenu key to enter the channel number at which the measurement is to take place and press Enter.

4.	Under the Measure menu, press the Channel Power submenu key.

5.	Press the On/Off submenu key to start and stop channel power measurements.

 

Channel Power Measurement for GSM

Global Systems for Mobile (GSM) communication is a globally accepted standard for digital cellular communication. There are a number of frequency bands allocated to GSM mobile phones that use a combination of Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA). Within each band are approximately one hundred available carrier frequencies on 200 kHz spacing (FDMA), and each carrier is broken up into time-slots so as to support eight separate conversations (TDMA). GSM uses the Gaussian Minimum Shift Keying (GMSK) modulation method.

Required Equipment

•	Test Port extension cable, Anritsu 15NNF50-1.5C

Procedure

1.	Using the test port extension cable, connect the signal source to the RF In test port.

2.	Press the Amplitude main menu key and press the Reference Level submenu key to set the reference level to –20 dBm. Adjust the values given in this procedure to match your measurement conditions.

3.	Press the Scale submenu key and set the scale to 10 dB/div.

4.	Press the BW main menu key and verify that Auto RBW and Auto VBW are On.

5.	Press the Freq main menu key followed by the Signal Standard submenu key. Scroll through the dialog box using the rotary knob or Up/Down arrow keys to highlight the GSM 900 - Downlink standard for the measurement and press Enter.

6.	Press the Channel# submenu key and enter the channel number using the keypad, the arrow keys, or the rotary knob. For this example, select Channel 60.

7.	Press the Shift key then the Measure (4) key and press the Channel Power submenu key.

8.	Press the Center Freq submenu key and verify that the center frequency is set to that of the GSM signal, in this case 947.0 MHz.

9.	Press the Ch Pwr Width submenu key and enter 200 kHz for the integration bandwidth, or set the integration bandwidth appropriate for the particular application.

10.	Press the Span submenu key and enter 600 kHz as the channel span, or set the channel span to a value appropriate for the particular application.

11.	Make the measurement by pressing the Measure (4) key, press the Channel Power submenu key, then press On. The measurement results are displayed in the message area.

Note	Channel Power is a constant measurement. After it is turned on, it will remain on until it is turned off by pressing the On/Off submenu key again.

 

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