Aerospace and Electronic Systems Magazine March 2018 - 11

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BISTATIC SHIPBORNE TRANSMITTER AND RECEIVER
Lastly, we consider the most complicated bistatic configuration, in
which the transmitter and receiver are installed on different ships that
may have different motions. Compared to the bistatic system with a
stationary transmitter, the advantage of this configuration is that the
coverage area of shipborne radar can be greatly extended beyond the
horizon in the open sea. However, the complexities of bistatic configuration and different motions experienced by the transmitter and
receiver bring even more technical difficulties to the target detection.
We still start from the SIMO configuration, in which the transmitter has a single antenna and the receiver has an eight-element
antenna array, as shown in Figure 9a. It is assumed that the transmitter platform moves along the x-axis and the receiver platform still
moves toward 45° w.r.t. the x-axis. From the clutter spectrum shown
in Figure 9b, we can see that because of the different moving directions of the transmitter and receiver, even the SIMO configuration
produces complicated clutter distribution, which is different from
the SIMO case when the transmitter is stationary. The SINR loss for
the assumed target (at 39° w.r.t. the x-axis) is depicted in Figure 9c,
in which the adjacent notches are quite close to each other so that
visually, there are only two wide notches. However, for the general
case in which the target is in other directions, there will be four separate notches. Figures 10a-10c present the geometrical configuration
and simulation results for the MISO configuration, in which the
transmitter has an eight-element array and the receiver has a single
antenna. Similar to the SIMO results shown in Figure 9, the clutter
distribution for the MISO configuration is complicated. From the
SINR loss plot, we can see that the UDSF is also limited because of
the four deep notches, which will greatly affect target detection performance. Based on more extensive simulations, we found that these
results always hold, unless in a special case in which the moving
directions and array axes of the transmitter and the receiver overlap
exactly. A solution to solve this problem is to add one more antenna
to the receiving system to form a MIMO configuration, as illustrated
in Figure 11a. Similar to the MIMO system shown in Figure 8a, a 2D
virtual array can be formed for this MIMO system and the backlobe
clutters can be effectively suppressed. Figures 11b and 11c show the
corresponding results of clutter spectrum and target SINR loss for
this MIMO system, and the performance improvements are obvious.
The superior performance of this bistatic MIMO configuration is applicable for any motion of the transmitter and receiver, which gives
great flexibility to the practical operation of ship platforms.

Figure 9.

Bistatic HFSWR shipborne transmitter and receiver as SIMO. (a) System configuration. (b) Clutter spectrum. (c) SINR loss.

greatly improved compared to that in the MISO configuration. The
additional cost we paid for this performance improvement is just
adding one more HF receiving antenna, which is trivial. This twoelement receiving array can still be easily installed on a small ship
platform. More importantly, based on more extensive simulations,
the superior performance shown in Figures 8b and 8c can always be
achieved, no matter which direction the receiver is moving toward.
MARCH 2018

SUMMARY
In this article, the advantages and disadvantages of different shipborne HFSWR configurations are analyzed and compared, particularly on STAP-based sea clutter suppression and target detection
performance. In all three shipborne HFSWR configurations (i.e.,
monostatic, bistatic with coastal transmitter and shipborne receiver, and bistatic with shipborne transmitter and receiver), the MIMO
working mode demonstrates more advantages and flexibilities
than the SIMO and MISO modes. For the monostatic shipborne
HFSWR, by installing two transmitting antennas at the fore and
aft of the ship and placing the receiving antennas between them,

IEEE A&E SYSTEMS MAGAZINE

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine March 2018