Obtaining Flat Test Port Power with the Agilent 8360’s User Flatness Correction Feature Product Note 8360-2
Introduction The 8360 series synthesized sweepers provide extremely flat power at your test port, for testing power sensitive devices such as amplifiers, mixers, diodes or detectors. The user flatness correction feature of the 8360 synthesized sweepers compensates for attenuation and power variations created by components between the source and the test device. User flatness correction allows the digital correction of up to 801 frequency points (1601 points via GPIB), in any frequency or sweep mode (i.e.
Theory of operation A major contribution of the 8360 series synthesized sweepers is their unparalleled leveled output power accuracy and flatness. This is achieved by using a digital (vs. analog) design to control the internal automatic leveling circuitry (ALC). An internal detector samples the output power to provide a DC feedback voltage. This voltage is compared to a reference voltage that is proportional to the power level chosen by the user.
If the correction frequency span is only a subset of the start/stop frequency span set on the source, no corrections will be applied to the portion of the sweep that is outside the correction frequency span. The following example illustrates how the data is distributed within the user flatness correction array. When utilizing user flatness correction, do not exceed the 8360 ALC operating range.
Configuration examples The following examples demonstrate the user flatness correction feature: 1. Using an Agilent 437B power meter to automatically enter correction data for a swept 2 to 18 GHz measurement. 2. Manually entering correction data for a stepped (list mode) measurement. 3. Automatically entering correction data for an arbitrary list of correction frequencies when making swept mm-wave measurements. 4.
Data entry methods for user flatness correction User flatness correction data is obtained by connecting a power meter sensor at the desired test port and calibrating the measurement system. To make an accurate power meter measurement, the power meter must be calibrated to the power sensor by attaching the sensor to the "POWER REF" output and performing a calibration. (It is assumed that the user is already familiar with calibrating and zeroing the power meter in use.
Example 1: Swept measurement with automatically entered corrections This example illustrates how to set up a 2 to 18 GHz swept measurement with a correction frequency every 100 MHz (see figure 1 for system configuration). The auto fill feature is used to increment the correction frequencies across the entire measurement range. A 437B power meter automatically enters correction data into the array.
Example 2: Frequency list measurement with manually entered corrections the appropriate correction and enter it into the table. If the user already has a table of correction data prepared, it can be entered directly into the correction table from the keypad on the front panel of the 8360. The following example demonstrates how to enter correction data when using a power meter other than the 437B (see figure 8 for the system configuration).
Command Description Setup source parameters [PRESET] Reset source to a known state POWER [POWER LEVEL] 5 dBm Set test port power to +5 dBm (P0 max - Ppath loss) Create frequency list FREQUENCY[MENU] [more] [Fltness Menu] Enter List [Freq] 5 GHz Access the frequency softkey menu Display next softkey menu Access the frequency list softkey menu Enter 5 GHz as the first frequency Entering a frequency automatically sets the offset and dwell to 0 dB and 10 ms, respectively Enter 18, 13, 11, and 20 GHz from
Example 3: Swept mm-wave measurement with arbitrary correction frequencies between non-sequential correction frequencies will vary. This example uses the 437B to automatically enter correction data into the array. The focus of this example is on using user flatness correction to obtain flat power at the output of the Agilent 83550 series mm-wave source modules. In this case we will use non-sequential correction frequencies in a swept 26.5 to 40 GHz measurement with an 83554 source module.
Command Description Turn off source Connect Source Module Interface cable Turn on source Setup source parameters [PRESET] FREQUENCY [START] 26.5 GHz FREQUENCY [STOP] 40 GHz POWER [POWER LEVEL] 7 dBm Set start frequency to 26.
Example 4: Scalar analysis measurement with user flatness corrections When a 437B power meter is used to automatically enter the correction data, the correction calibration routine will automatically turn off any active modulation and then reactivate the modulation upon the completion of the data entry process. Therefore, the scalar pulse modulation that is automatically enabled in a scalar measurement system will be disabled during a 437B correction calibration.
Command Description [PRESET] analyzer Reset analyzer and source to a known state Setup source parameters FREQUENCY [START] 2 GHz Set start frequency to 2 GHz FREQUENCY [STOP] 20 GHz Set stop frequency to 20 GHz POWER [POWER LEVEL] n dBrn Set power to maximum available leveled power Set up the appropriate measurement (i.
Example 5: Computer controlled measurements with user flatness corrections This section focuses on computer controlled measurement systems. The following program interrogates the source and a 437B power meter for frequency and power information respectively. The source (83620B) is programmed to sweep from 2 to 20 GHz, with user flatness corrections every 100 MHz and +5 dBm leveled output power.
Note: The 8360’s rear panel language and address switches must be set to 7 and 31 (all 1s), to allow the user to change the language or address of the source via a computer. The default settings are TMSL and 19 respectively. The following program (see figure 11b) illustrates how to transfer 1601 points from a file called "Corr_data", into the user flatness correction array using the "CORRection:ARRay" TMSL command.
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