Increasing Range Using an External LNA
DW3000/QM33100
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APS304 Rev 1.0; Page 7 of 12 www.qorvo.com
2.2.4 Example Calculation of Highest Supportable Signal Power
Taking the line-up shown in Figure 2, we have a BPF and an LNA followed by the QM33100. If we use the
LNA gain value from the previous example (15 dB) and assume channel 9 operation at 1 m separation between
receiver and transmitter, a transmitter
and antenna gain for both
transmitter and receiver, then we have:
This gives us a margin of:
For very short distances between the receiver and the transmitter, the LNA may saturate. For example, with 7
cm separation the propagation loss for UWB channel 9 is 27.5 dB. The receiver will be operating very close to
its compression point.
Note that the maximum transmitted power used for this calculation is -14.3 dBm/500MHz. This value is
extrapolated from the FCC specification for max-mean power limit per 1 MHz (-41.3 dBm/MHz). In practice,
the maximum output power will be around -16 dBm/500MHz, due to the natural sloping of the transmit spectrum
at the sides.
2.3 Control Signals
The DW3000/QM33100 transceiver provides GPIO signals to control switching of the path between the
transceiver RF pins and the antenna, to include or exclude the LNA, depending on whether the transceiver is
in RX or TX mode.
Table 2: Control signals
General Purpose I/O pin.
On power-up it acts as the SPIPHA (SPI phase selection) pin for
configuring the SPI mode of operation.
It may be configured for use as EXTRXE
(External Receiver Enable).
This pin goes high when the DW3000 is in receive mode.
After power-up, the pin will default to a General Purpose I/O pin
General Purpose I/O pin.
After power-up this pin will default to a General Purpose I/O pin.
Can be configured for use either as:
COEX_OUT
an output that can be configured via software to indicate an
RX, TX, or both.
or
PDoA_SW1
An output that goes high 100ns before the start of RX
2.4 Power Supplies
If an LNA is added to the UWB RF front-end, it is important that adequate decoupling is provided to
keep the supply “quiet” and avoid injecting noise into the receiver. The LNA manufacturer’s recommendations
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