Getting Started 1
Keysight 2050/60 X-Series User’s Guide 17
Theory of Operation
Figure 1-3 2050/60 X-Series sensor block diagram
The 2050/60 X-Series sensors utilize 4 planer doped barrier diode in a 4-path microwave
circuit that enables fast average power measurements over a wide dynamic range. The 4-
path network splits the input signal into a different power range for each of the 4 diodes
such that all of them can operate in their square-law region. Ensuring diode power sensors
operate within the square-law region means that they can convert RF power to voltage in a
linear manner, regardless of the signal being measured. A single diode sensor square-law
behavior may only provide perhaps 40dB of fast dynamic range. Each of the diodes has
their own signal conditioning and analog to digital convertor which allow subsequent
digital processing to select the best diode for further processing. This in turn presents a
user experience indistinguishable from a single high dynamic range square-law power
sensor.
As a truly universal power sensor, it has features that allow different kinds of power
measurements to be made. Primarily it operates as an average power sensor and
traditionally this type of measurement means that an instrument will output a numeric
result at some rate determined by the instrument. In AVERAGE mode the sensor enables a
chopper amplifier circuit that allows low level signals to be measured in the presence of
low frequency noise. This chopper circuit operates by modulating the signal prior to
amplification; the modulation takes the form of passing or negating the signal for half-
periods of the chopper signal. Recovering the original signal within the digital processing is
achieved by averaging the ‘passing’ half-period samples together with the negated
‘negating’ half-period samples, to provide a new answer once for each period of the
chopper. The corresponding “de-chopping” is carried out in digital section to allow proper
correction and measurement of input signal. The chopper stabilization circuit essentially
remove the offset and low frequency noise contribution of the signal condition stages from
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