PhDConcealed weapon detection (CWD) has been a hot topic as the concern about pub-
lic safety increases. A variety of approaches for the detection of concealed objects
on the human body based on earth magnetic ¯eld distortion, inductive magnetic
¯eld, acoustic and ultrasonic, electromagnetic resonance, MMW (millimetre wave),
THz, Infrared, x-ray technologies have been suggested and developed. Among all
of them, MMW holographic imaging is considered as a promising approach due
to the relatively high penetration and high resolution that it can o®er. Typical
concealed target detection methods are classi¯ed into 2 categories, the ¯rst one is a
resonance based target identi¯cation technique, and the second one is an imaging
based system. For the former, the complex natural resonance (CNR) frequencies
associated with a certain target are extracted and used for identi¯cation, but this
technique has an issue of high false alarm rate. The microwave/millimetre wave
imaging systems can be categorized into two types: passive systems and active sys-
tems. For the active microwave/millimetre wave imaging systems, the microwave
holographic imaging approach was adopted in this thesis. Such a system can oper-
ate at either a single frequency or multiple frequencies (wide band). An active,
coherent, single frequency operation millimetre wave imaging system based on the
theory of microwave holography was developed. Based on literature surveys and
¯rst hand experimental results, this thesis aims to provide system level parame-
ter determination to aid the development of a target detection imager. The goal
is approached step by step in 7 chapters, with topics and issues addressed rang-
ing from reviewing the past work, ¯nding out the best candidate technology, i.e.
the MMW holographic imaging combined with the resonance based target recog-
i
nition technique, the construction of the 94 GHz MMW holographic prototype
imager, experimental trade-o® investigation of system parameters, imager per-
formance evaluation, low pro¯le components and image enhancement techniques,
feasibility investigation of resonance based technique, to system implementation
based on the parameters and results achieved. The task set forth in the beginning
is completed by coming up with an entire system design in the end.
