LBXXXA Series USB Powe
™
Product Manual PMA (Power Meter Application)
Revision: 08/02/11
- 19 -
4. Detailed Operating Instructions
Measurement Overview and Examples
The Power Meter Application
The LB4XXA and LB6XXA series of RF sensors makes Avg and pulse (modulation) measurements in a 10 MHz video
bandwidth. The LB5XXA series of microwave sensors makes CW or true average power measurements up to 26.5
GHz. (The LB480A and LB680A sensors are also capable of making pulse profile measurements
– refer to the
Quick
Start Guide and Product Manual for the Pulse Profiling Application
).
The pulse power mode of operation displays pulse power (average power in the pulse); pulse duty cycle; peak pulse
power; average power; and Crest Factor (CrF) or the peak to average power ratio. This mode applies to the LB4XXA
sensors only. The LB4XXA/LB6XXA sensors are capable of more than 2000 settled readings per second.
There is provision for logging measurements to file and pass/fail limit checking on all models. Various trigger methods
are available to allow the measurement of continuously modulated signals or single events.
Refer to the block diagram in the Measurement Accuracy section of this document for the following discussion: The
incoming broadband RF/microwave energy is first conditioned and converted to digital format. The input power drives
two measurement channels of differing sensitivity. The transition between these paths is typically between -30 and -
20 dBm. Most LadyBug power sensors continually digitize both paths simultaneously and use a weighted average
approach over the transition range. This approach to the measurement means that a seamless measurement
transition between paths is possible. It also means that the full dynamic range of the sensor is available to all
measurements all of the time.
By contrast, sensors produced by other manufacturers measure only one path at a time. This requires that the
transition be managed
after
an errant measurement has been made. This makes the transition between any two
ranges a point of potential discontinuity or hysteresis. As a result, minor differences in the calibration between the two
paths can often result in constant and annoying switching between paths. Constant path switching can produce a
noticeable jump in power level readings. Another and perhaps more detrimental effect is that this approach guarantees
that the full dynamic range of the sensor is not available to any given measurement. Ladybug has resolved these
range transition problems.
The LB4XXA and LB6XXA sensors are capable of making pulse (modulation) measurements. These pulse
measurements are possible because the LB4XXA sensors employ a 10 MHz video or modulation bandwidth.
Discussions about bandwidth are generally accompanied by concerns about making an aliased measurement. Though
uncommon in practice, aliasing can and does occur. LadyBug sensors can randomize the sampling in order to
minimize or eliminate the possibility of making an aliased measurement. However, this sampling randomization is
accompanied by a small performance penalty. Rather than penalize all measurements we allow the user to favor
performance (speed of measurement), or guard against aliasing. This choice is presented on the user interface as an
anti-aliasing option.
The display toolbar has an anti-aliasing control button that is used for CW and continuous pulse measurements only. It
is generally useful for the LB4XXA/LB6XXA sensors where the video content is greater than 200 kHz. This feature
guards against making aliased measurements for modulation bandwidths greater than 200 kHz. It actually determines
the sampling method that is employed for the particular modulation bandwidth - either narrow or wide. The toolbar
functions are explained in greater detail in the GUI Functions section of this manual.
The Pulse Profiling Application
The LB480A/LB680A are specifically designed for those applications requiring a time domain analysis of pulse and
other modulated signal formats.
Refer to the
Quick Start Guide and Product Manual for the Pulse Profiling Application.
