Boonton 4530 Peak Power Meter User Manual - Manual (Page 148)

Chapter 5 Boonton Electronics
Making Measurements 4530 Series RF Power Meter
5-6
5.4 SELECTING THE RIGHT MEASUREMENT MODE
Since the 4530 Series RF Power Meter can accept any type of Boonton power or voltage sensor, and each sensor type
can operate in one or more measurement modes.
5.4.1 CW Mode . CW diode sensors, thermal sensors and voltage probes all operate in CW Mode, and CW Mode
is only available for these types of sensors. As its name implies, CW Mode is intended primarily for CW
(unmodulated) signals, but there are other cases in which you may wish to use it. CW Mode may be the best
choice if your measurement meets any of the following conditions:
• Signal level is very low (below about -40dBm).
• Signal is a single, unmodulated RF carrier (CW).
• Need to measure average power only of any signal (modulated or CW) that falls within dynamic range of
thermal sensor (-30 to +20dBm).
• Need to measure average power only of any signal (modulated or CW) that falls within the true-RMS
(square-law) range of a diode sensor (-70 to -20dBm) at all times.
• Need to measure a spread-spectrum signal, or a composite signal that consists of multiple carriers or
channels spanning a wide (20 MHz or higher) frequency range.
If you wish to measure a modulated signal, a peak sensor operating in Modulated Mode or Pulse Mode is
often your best choice, provided the modulation bandwidth of the signal is within the sensor’s bandwidth
specification.
5.4.2 Modulated Mode . Modulated Mode is only available when using a peak power sensor, and is best choice
for most continuously modulated signals as well as for many pulse modulated signals. Since Modulated
Mode is a continuous measurement mode, it does not differentiate between the times that a pulsed or periodic
signal is off, and the times it is on. If you wish to make measurements that are synchronous with a period
waveform, consider Pulse Mode. Modulated Mode is best for the following types of measurements:
• Moderate signal level (above about -40dBm).
• Signal is continuously modulated with a modulation bandwidth that is less than about 20MHz.
• Signal modulation may be periodic, but only non-synchronous measurements are needed (overall average
and peak power).
• “Noise-like” digitally modulated signals such as CDMA or COFDM when only average and peak power
measurements are needed. If peak probability information is required, consider Statistical Mode.
5.4.3 Pulse Mode . Pulse Mode is only available when using a peak power sensor, and is best choice for most
pulse modulated and periodic signals. Pulse mode requires a repeating signal edge that can be used as a
trigger, or an external trigger pulse that is syncronized with the modulation cycle. Pulse mode performs
measurements that are synchronous with the trigger - that is the measurements are timed or “gated” so that the
same portion of the waveform is measured on each successive modulation cycle. Multiple modulation cycles
may be averaged together, and measurement intervals may span both before and after the trigger. Pulse Mode
is best for the following types of measurements:
• Moderate signal level (above about -40dBm except when modulation is “off”).
• Signal is periodic.
• A time snapshot of a single event is needed (minimum single-shot time is 50 microseconds).
• Typical modulation and signal types: NADC, GSM (and extensions), TDMA, RADAR, SatCom, TCAS,
Bluetooth, iDEN, NTSC, Wireless LAN.