We introduce the concept of a Rotman-lens spectrum decomposer (RLSD) real-time spectrum-sniffer (RTSS) for cognitive radio. Compared to a previously existing RTSS, the RLSD-RTSS offers the advantages of being 1) based an a simpler and lower-cost purely passive structure, 2) easier to design and easily amenable to tunability, 3) of much broader bandwidth, and 4) of accommodating more channels. The electrical size of the device is electrically larger, but perfectly acceptable in the millimeter-wave frequency range. The proposed RLSD-RTSS is demonstrated theoretically and experimentally, and been shown to support tunability in terms of both bandwidth-resolution and operation band. Given its unique features, this device may find wide applications in 5G UHD and 3D video systems.
We present an enhanced design -in terms of resolution flexibility, input port position arbitrariness and frequencyrange tunability -of the planar Rotman lens spectrum decomposer (RL-SD). This enhancement is achieved by manipulating the output port locations through proper sampling of the frequency-position law of the RL-SD, inserting a calibration array compensating for frequency deviation induced by input modification and introducing port switching, respectively. A complete design procedure is provided and two enhanced RL-SD prototypes, with uniform port distribution and uniform frequency resolution, respectively, are numerically and experimentally demonstrated.
A microwave Hilbert transformer is introduced as a new component for Real-time Analog Processing (RAP). In contrast to its optical counterpart, that resort to optical fiber gratings, this Hilbert transformer is based on the combination of a branch-line coupler and a loop resonator. The transfer function of the transformer is derived using signal flow graphs, and two figures of merits are introduced to effectively characterize the device: the rotated phase and the transition bandwidth. Moreover, a detailed physical explanation of its physical operation is given, using both a steady-state regime perspective and a transient regime perspective. The microwave RAP Hilbert transformer is demonstrated experimentally, and demonstrated in three applications: edge detection, peak suppression and single sideband modulation.
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