Giga-tronics 8650A Series, Руководство по эксплуатации

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Front Panel Operation
Manual 31470, Rev. E, April 2001 2-31
2.3.9 Mode Restrictions
In certain modes the 8650A has highly specific restrictions on its operation:
• In the fast measurement collection modes (swift and fast buffered), it is not possible to make
measurements which compare the two channels. In other words, it is possible to make
measurements using sensor A, or B, or both, but measurements such as A/B and A-B are not
permitted.
• In GPIB remote operation, only one reading can be sent over the bus (it can be A, or B, or a
comparative measurement such as A/B, but it is not possible for separate measurements of A
and
B to be sent over the bus). The exception is that in the swift and fast buffered measurement
collection modes, it is possible for both A and B to be sent over the bus.
2.3.10 When to use CW, MAP and BAP
For measuring signals with any kind of modulation, MAP mode should be used. In this mode, the 8650A
makes use of its digital signal processing algorithms to ensure that the reading is the correct average
power level regardless of modulation type (see Section B.2.2 for limits on modulation rate, etc.).
Of course, CW signals may also be accurately measured in MAP mode. This raises the question, why use
CW mode? CW mode offers a few more dB of dynamic range at low power levels when using a CW
power sensor, such as the 80301A. In addition, in CW mode the 8650A is form, fit, and function
compatible with its predecessor, Model 8540.
BAP mode should be used only for the measurement of signals which are pulse modulated. In this mode
the meter will accurately measure the average power of the signal during the on-time of the pulse. This
mode works equally well regardless of whether the signal is modulated during the pulse on time.
2.3.11 Multi-Tone Tests
Multi-tone testing refers to more than one RF carrier combined into one signal to be measured. Two-
tone intermodulation testing, for example, is a common test performed on a wide variety of RF
components and subsystems. MAP mode should be selected for these applications. The 8650A test
procedure is as follows:
1. Calibrate the sensor according to the procedure outlined earlier in Section 2.3.3.
2. From the Main Menu press [ Sensor Setup ]. From the Sensor Setup menu, press [ Modulated Sensor ]
and then select the MAP mode by pressing [ MAP ].
3. Press [ FREQ ] and enter the operating carrier frequency.
4. Connect the sensor to the multi-tone source and record the power level.
For two-tone testing, small errors in the measurement will result when the carriers are separated by more
than the specified bandwidth of the sensor. The amount of error is also a function of average power
level. For average power less than about -20 dBm, there is no modulation-induced measurement error at
any tone separation. Consult the error charts found in Section B.2.2.
Multi-carrier testing usually refers to more than two carriers combined into one signal. Common multi-
carrier tests combine multiple carriers. In determining expected measurement error for these types of
signals, the maximum difference in frequency between any two carriers should be used as the tone
separation when applying the error charts in the manual.
Another important feature of multi-carrier signals is that they can have a high peak-to-average power
ratio. This ratio can be as high as 10 dB for multiple carriers. The significance of this in terms of making