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Receiver Control
Last updated: July 24, 2008
The test set's receiver includes two frequency downconverters:
-
Measurement downconverter
-
Demodulation downconverter
The Demodulation downconverter is used to establish and maintain the connection (RF link) between the access terminal 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
Automatic receiver control is the default for all operating modes except CW (see
CW Operating Mode
). With automatic receiver control, the test set automatically tunes to the correct frequencies for making measurements and maintaining a connection. Also, the test set automatically 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, and the current value for expected power is displayed on many of the transmitter power measurement screens.
When operating in active cell operating mode with automatic receiver power control, 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 (see
Expected Power
). Tune frequencies are derived from the channel field setting (see
Channel
).
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.
In CW operating mode, you must always specify what frequencies and power the receiver should tune to, there is no automatic receiver control.
Manual Receiver Control in Active Cell Operating Mode
For front panel operation, see
Manual Receiver Control in Active Cell or Cell Off Operating Mode
.
Manual receiver power
When the Rcvr Power Ctrl field is set to manual (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 receiver power control is disabled. The test set will adjust its attenuation to receive a signal at the level indicated by the Receiver Power field.
Use the following commands for manual receiver power control:
When reverse power control (Rvs Power Ctrl) is set to Active bits, closed loop power control will drive the access terminal'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 access terminal's power level to the manually set Receiver Power, select alternating bits in the Rvs Power Ctrl field. With alternating bits is selected in the Rvs Power Ctrl field, cell power level changes will control the access terminal'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. If you set Meas Frequency field to manual control by pressing the
OFF/MANUAL
key, this sets
Meas Frequency field
to the last frequency value that this parameter was set to.
The commands used to manually tune the test set's measurement downconverter input signal path are:
Demodulation downconverter frequency
In Active Cell operating mode, there is no access to manual control of the receiver demodulation frequency. (Refer to the
Block Diagram
for a description of the Signal Downconversion paths.)
Manual Receiver Control in IS-856 Test Operating Mode
For front panel operation, see
Manual Receiver Control in IS-856 Test Operating Mode
.
Manual receiver power
When the Rcvr Power Ctrl field is set to manual (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 receiver power control is disabled. The test set will adjust its attenuation to receive a signal at the level indicated by the Receiver Power field.
Use the following commands for manual receiver power control:
In IS-856 test mode the access terminal can be programmed to respond to closed loop power control bits. If the access terminal is responding to power control bits, and with alternating bits selected in the Rvs Power Ctrl field, cell power level changes will control the access terminal'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:
Manual control of the demodulation receiver frequency is rarely needed. If you require control of the receiver's measurement frequency, see
Measurement downconverter frequency
.
Manual Receiver Control in CW Operating Mode
For front panel operation, see
Manual Receiver Control in CW Operating Mode
.
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 access terminal is set manually using the
RFANalyzer:CW:EXPected:POWer
command.
Measurement downconverter frequency
When the Receiver Control softkey is selected, a menu drops down that includes a setting for Measurement Frequency.
The command used to manually tune the test set's measurement downconverter input signal path is:
Demodulation downconverter frequency
When the Receiver Control softkey is selected, a menu drops down that includes a setting for Uplink Frequency.
The command used to manually tune the test set's demodulation downconverter input signal path is:
Manual control of the receiver demodulation frequency is rarely needed. If you require control of the receiver's measurement frequency, see
Measurement downconverter frequency
.
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 access terminal
. This range of RF power is meant to accommodate the use of a gain or loss network between the access terminal 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.
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