A novel beamformer for circular sonar arrays
A new Beamformer (BF) technique using Linear Deltamodulation (DM) on the spatially sampled circular array sensor signals is presented. In this method, the FIR-type of beam-former implementation for circular arrays results in an extremely simplified hardware which does away with multipliers and retains basically adders. Thus, the immediate problem of large word-size is considerably resolved. The DM-type of BF by virtue of the implementation, provides an additional advantage of beam-space interpolation. Various aspects of array gain, sidelobes and noise performance are dealt with the help of simulation studies. Hardware structures both for fixed and programmable beamformer coefficients are also proposed which bring out the potential of this technique for compact sonar systems.
Broadband beamforming and direction finding using concentric ring array
Sensor arrays have been used widely in applications including radar, sonar, seismology, biomedicine, communications and imaging. A very popular type of sensor array is circular array, which has almost invariant array pattern in azimuthal plane. This dissertation considers beamformer design and direction finding for a broadband source using concentric ring array(CRA) that contains many concentric rings of different radii. The multi-ring structure of a CRA has several advantages including the flexibility in array pattern synthesis and adaptive array design. We first proposed three CRA array pattern synthesis techniques, which can be used to control the sidelobe and/or mainlobe width of the array pattern of a deterministic broadband beamformer. We then proposed a flexible partially adaptive broadband beamformer design based on element-space approach. Finally, we proposed an efficient direction finding technique for broadband source using CRA. The proposed design techniques are corroborated by experiments from simulated as well as measured data.
Binary transversal filters using recirculating shift registers.
The use of recirculating shift registers in the implementation of binary transversal filters with quantized coefficients is discussed. Shift registers are employed in a serial processing mode to reduce circuit complexity at the expense of a lower maximum processing rate. An implementation of a 34-stage filter using standard m.o.s. shift registers is discussed in detail. Some alternative arrangements are considered.