Receiver Control

Receiver Control

Last updated: February 1, 2007

The test set's receiver includes two frequency downconverters:

The Demodulation downconverter is used to establish and maintain the call (RF link) between the mobile station and test set, while the Measurement downconverter is optimized for measurements.

Refer to the Block Diagram for a description of the Signal Downconversion paths.

Automatic Receiver Control

By default, the test set automatically tunes to the correct frequencies for making measurements and maintaining a call. Also, the test set adjusts attenuation settings according to the power level that should be present at the RF IN/OUT port given the current settings. This power level is referred to as the Expected Power ( Expected Power ), and the current value for Expected Power is displayed on many of the transmitter power measurement screens (for example, the measurement screen for digital average power, channel power, and access probe power).

When operating in Active Cell Operating Mode, with IS-2000 or IS-95 selected as the System Type, Expected Power is derived essentially from the Cell Power setting according to open loop power control behavior, but Expected Power is also offset by other settings such as:

Tune frequencies are derived from the Channel field setting.

In some instances you may want to control the test set's receiver settings manually rather than allowing the test set to automatically control them. This ability is referred to as manual receiver control.

Manual Receiver Control in Active Cell Operating Mode

For front panel operation, see How Do I Change Test Set's Receiver Control Parameters? .

Manual receiver power

When manual receiver power control is selected, an additional field is displayed below Rcvr Power Ctrl. That field is labeled Receiver Power, and when it is displayed automatic power control is disabled. The test set will adjust its attenuation to receive a signal at the level indicated by the Receiver Power field.

When the selected System Type is IS-2000 or IS-95 (cdma systems), the Receiver Power field is set programmatically using the RFANalyzer:MANual:POWer[:SELected] command.

When reverse power control (Rvs Power Ctrl) is set to Active bits, closed loop power control will drive the mobile station's transmitted power to the power level set in the Receiver Power field. To effectively disable closed loop power control and inhibit the test set's ability to drive the mobile station power level to the manually set Receiver Power, select alternating bits in the Rvs Power Ctrl field. With alternating bits selected in the Rvs Power Ctrl field, cell power level changes will control the mobile station's power level according to open loop power control behavior.

When the selected System Type is AMPS, the Receiver Power field is set programmatically using the RFANalyzer:MANual:ANALog:POWer[:SELected] commands. The mobile station power level will continue to be controlled by the Anl MS TX Level field setting.

Measurement downconverter frequency

When a frequency is entered in the Meas Frequency field, the selection labeled Auto is replaced by a manual receiver control tune frequency. The receiver will no longer be tuned according to the channel number entered in the Channel field (for IS-2000 or IS-95) or the ACC Channel (for AMPS).

The measurement receiver frequency commands used to manually tune the test set's measurement downconverter input signal path (see Block Diagram ) are:

Demodulation downconverter frequency

In Active Cell operating mode, there is no access to manual control of the demodulation receiver frequency. (Refer to the Block Diagram for a description of the Signal Downconversion paths.)

Manual Receiver Control in IS-2000 Test Operating Mode

For front panel operation, see How Do I Change Test Set's Receiver Control Parameters? .

Manual receiver power

When manual receiver power control is selected, automatic power control is disabled and an additional field is displayed. That field is labeled Receiver Power. The test set will adjust its attenuation to receive a signal at the level indicated by the Receiver Power field.

The Receiver Power field is set programmatically using the RFANalyzer:MANual:POWer[:SELected] command.

In test mode the mobile station can be programmed to respond to closed loop power control bits. If the mobile station is responding to power control bits, and with alternating bits selected in the Rvs Power Ctrl field, cell power level changes will control the mobile station's power level according to open loop power control behavior.

Measurement downconverter frequency

When a frequency is entered in the Meas Frequency field, the selection labeled Auto is replaced by a manual receiver control tune frequency. The receiver will no longer be tuned according to the channel number entered in the Channel field.

The measurement receiver frequency commands used to manually tune the test set's measurement downconverter input signal path are:

Demodulation downconverter frequency

When a frequency is entered in the Rvs Link Freq field, the selection labeled Auto is replaced by a manual receiver control tune frequency. In manual mode, the receiver's demodulation downconverter will no longer be tuned according to the channel number entered in the Channel field.

The commands used to manually tune the test set's demodulation downconverter input signal path are:

   
NOTE
Manual control of the demodulation receiver frequency is rarely needed. Use the measurement receiver when manual receiver frequency control is required.
   

Manual Receiver Control in AVC Test Operating Mode

For front panel operation, see How Do I Change Test Set's Receiver Control Parameters? .

Manual receiver power

When manual receiver power control is selected, automatic power control is disabled and an additional field is displayed. That field is labeled Receiver Power. The test set will adjust its attenuation to receive a signal at the level indicated by the Receiver Power field.

The Receiver Power field is set programmatically using the RFANalyzer:MANual:ANALog:POWer[:SELected] command.

In test mode the mobile station can be programmed to respond to closed loop power control bits. If the mobile station is responding to power control bits, and with alternating bits selected in the Rcvr Power Ctrl field, cell power level changes will control the mobile station's power level according to open loop power control behavior.

Measurement downconverter frequency

When a frequency is entered in the Meas Frequency field, the selection labeled Auto is replaced by a manual receiver control tune frequency. The receiver will no longer be tuned according to the channel number entered in the AVC Channel field.

The commands used to manually tune the test set's measurement downconverter input signal path are:

Demodulation downconverter frequency

When a frequency is entered in the Rvs Link Freq field, the selection labeled Auto is replaced by a manual receiver control tune frequency. In manual mode, the receiver's demodulation downconverter will no longer be tuned according to the channel number entered in the AVC Channel field.

The commands used to manually tune the test set's demodulation downconverter input signal path are:

   
NOTE
Manual control of the demodulation receiver frequency is rarely needed. Use the measurement receiver when manual receiver frequency control is required.
   

Manual Receiver Control in CW Operating Mode

For front panel operation, see How Do I Change Test Set's Receiver Control Parameters? .

Manual receiver power

When the Receiver Control softkey is selected, a menu drops down that includes a setting for Expected CW Power. The test set will adjust its attenuation to receive a signal at the level indicated by the Expected CW Power.

For CW operating mode, the Expected CW Power from the mobile station is set manually using the RFANalyzer:CW:EXPected:POWer commands.

Measurement downconverter frequency

When the Receiver Control softkey is selected, a menu drops down that includes a setting for Measurement Frequency.

The commands used to manually tune the test set's measurement downconverter input signal path are:

Demodulation downconverter frequency

When the Receiver Control softkey is selected, a menu drops down that includes a setting for Uplink Frequency.

The commands used to manually tune the test set's demodulation downconverter input signal path are:

   
NOTE
Manual control of the demodulation receiver frequency is rarely needed. Use the measurement receiver when manual receiver frequency control is required.
   

Under Range/Over Range Errors

The test set uses the expected power level to establish a range of acceptable input levels into its receivers. If the received signal is above or below the acceptable range, an Over Range or an Under Range message is displayed and the integrity value for the measurement is set to 5 or 6 (respectively). Refer to Integrity Indicator for details about the integrity values.

You can set the expected power level beyond the capability of the test set's hardware because expected power is intended to reflect the potential range of RF power at the mobile station . This range of RF power is meant to accommodate the use of a gain or loss network between the mobile station and the test set. See Amplitude Offset for details about amplitude offset.

The upper and lower limits of expected power provide boundaries for the combination of amplitude offset and expected power. For example: in Active Cell Operation Mode if you set expected power to +52 dBm and the amplitude offset to -3 dB, the calculated receiver power will be +49 dBm, but the test set shall be set to +30 dBm, the upper limit of the hardware. If the calculated value of receiver power goes below -79 dB, the lower limit of the hardware, the test set shall be set to -79 dB.

Effects on Receiver Control When Changing Operating Mode

After selecting the operating mode and setting one or more receiver controls to manual, the receiver control settings remain as you set them until you change operating mode. Changing operating mode (except for CW which defaults to manual) causes some or all receiver parameters to return to automatic control.