Carrier Feedthrough measures the amount of unmodulated signal that is leaking through the transmitter and is displayed in the Code Domain Power display. The WCDMA 3GPP specification does not specify carrier feedthrough measurement.
Code Domain Power displays how much of the channel power is in each Orthogonal Variable Spreading Factor (OVSF code). Power is normalized to the channel power, so if a code reads -10 dB, it means that the code is 1/10th of the channel power. Colors are applied according to
Table: “Channel Power Colors”.
Channel power is the total power transmitted in the 5 MHz WCDMA channel specified. Channel Power measures the node B/base station transmitting power across the entire 5 MHz WCDMA (BTS) channel. Channel power is displayed in dBm and Watts.
In the WCDMA specification the scrambling code can be from 0 to 511. If the scrambling code is known, its value can be entered and the test set can decode and display the code domain power of the signal. If the scrambling code is unknown, the instrument can be set to auto scrambling so that the test set can lock onto the strongest code to decode and display the code domain power of the signal.
Frequency error is the difference between the received center frequency and the specified center frequency. This is tied to the external frequency reference accuracy and is typically useful only with a good external frequency reference.
The Active Channel Threshold Level can be set to indicate which code channels are considered active. Any code channels exceeding this power level are considered active traffic channels and any code channels below this power level are considered inactive (or noise). A horizontal red line on the screen represents the threshold level. This level can be set automatically based on the received signal, or the user can manually enter a value in the Threshold setup menu.
The Error Vector Magnitude is the ratio in percent of the difference between the measured waveform and the reference waveform. EVM metrics are used to measure the modulation quality of a transmitter. The 3GPP standard requires that the EVM not exceed 17.5%.
PCDE takes the noise and projects the maximum impact it will have on all OVSF codes. PCDE is the maximum value for the code domain error for all codes (both active and inactive).
In the 3GPP standard, in order to address the possibility of uneven error power distribution in WCDMA, the EVM measurement has been supplemented with PCDE. The 3GPP standard requires that the PCDE not exceed -33 dB at a spreading factor of 256.
