Understanding the BB60C Hardware |
Dynamic Range
12
DYNAMIC RANGE
3.5
Dynamic range has many definitions, but one common definition in spectrum analysis is 2/3(TOI –
DANL). A typical number for 1 GHz would be: TOI=-19 dBm, DANL = -151 dBm (10 Hz RBW). Dynamic
range, 2/3 (TOI – DANL) = 88 dB, and would be a function of RBW, frequency, gain and attenuation
settings, etc.
PROTECTING THE BB60C RF INPUT
3.6
The BB60C’s input attenuator and front end switches are sensitive to ESD and have a damage level just
above +20 dBm peak (not RMS). Some common events which may lead to front end damage include:
1)
Applying more than +20 dBm peak power, such as an antenna exposed to a radar pulse.
2)
ESD from a passive antenna, either from discharge to an antenna element, or from connecting a
large antenna or cable which has built up a static charge.
3)
Connecting to an active antenna which is already powered on (sudden discharge through the DC
blocking cap typically e20 dBm)
For any application which may expose the BB60C to front end damage, including connecting to active or
passive antennas, a coaxial limiter is recommended to protect the input.
A limiter will protect against overpowering the input, typically raising the damage level above 2 watts, as
well as offering significant protection against ESD. It will also offer some protection against the energy
spike you get when connecting to equipment with a DC or static voltage present. The energy may
significantly 20 dBm for several microseconds.
Generally, the performance at low input signal levels is just the insertion loss of the limiter, but at high
signal levels there will be some nonlinearity and the resulting intermodulation products. A typical limiter
will have an IP3 30 dBm, so for input signals below -10 dBm there should be little to no effect on
BB60C linearity.
For active antennas, with a built in amplifier, there are some additional concerns, as the amplifier’s
operating voltage probably only has a small inductor between the power supply and the output pin. To
avoid damage in this case, power on the BB60C, connect, and then power on the antenna. If this cannot
be done, consider a DC block, followed by a 1 dB pad, followed by a limiter, followed by the BB60C. The 1
dB pad can help when a DC voltage at very low impedance is present, by raising the effective impedance
by several ohms.
If it is a passive antenna mounted using a long coaxial cable, it may be building up a significant static
charge until it is connected. For this reason, it might make the most sense to keep the limiter connected
to the antenna rather than the BB60C. A DC block is probably not necessary for passive antennas in
most cases.
Содержание BB60C
Страница 1: ...BB60C Spectrum Analyzer User Manual...
