Stacking bistatic microwaves
MPS-4100 product guide • • • a - 9
4. For multiple in-line zones, mount 2 transmitters on one post, and 2 receivers
on another (see Figure a-9). Ensure that the modulation frequencies and
polarizations of the 2 units on each post are different.
5. For multiple zone configurations, carefully plan the layout, ensuring that
there are no possible conflicts or interference in modulation frequency or
polarization.
6. Use a minimum 10 cm (4 in.) post to ensure stability. Each post must be
installed in a concrete base that is at least 61 cm (24 in.) in diameter and
either 91 cm (36 in.) deep, OR, 15 cm (6 in.) below the frost line, whichever
is greater.
Determining the mounting height
The received signal is the vector sum of the direct signal and the reflected signals.
The quiescent (no intruder) received signal is greatly influenced by the mid-point
reflections. The phase relationship between the direct and reflected signals will
slowly change as the sensor antennas are raised from the ground level.
The two signals (direct and reflected) will combine constructively (in phase), or
destructively (out of phase), depending on the sensor mounting height and
separation distance. Constructive phasing is preferable because of the higher net
signal level received. Destructive phasing should be avoided because the low
signal level causes the receiver’s automatic gain control (AGC) to operate closer
to the top of its range. This will result in a higher nuisance alarm rate when the
microwave path loss increases, for example, during rain or snow.
Figure a-9 Stacked multiple in-line microwave detection zones
TX
TX
RX
RX
TX
TX
RX
RX
Zone A
Zone B
offset width
46 - 51 cm
(18 - 20 in.)
offset length
9.1 m (30 ft.)
side view
top view
TX
RX
TX
RX
offset width
46 - 51 cm
(18 - 20 in.)
offset length
9.1 m (30 ft.)
Zone A
Zone B
Содержание MPS-4100
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