Spectrum sensing technology is most vital to the its sensing capability is vulnerable to noise. Furthermore, it implementation of a CR system using dynamic spectrum is difficult to detect a frequency-hopping signal and wideresource management. This paper suggested a CR system bandwidth digital modulation signals such as spreadarchitecture with a wideband dual-stage spectrum sensing spectrum and multi-carrier modulation.technique -a coarse and a fine spectrum sensing. Specifically, the coarse spectrum sensing technique adopted wavelet Meanwhile, feature detection methods [7, 8] locate transforms in this architecture to provide a Multi-Resolution the repetitive signature of a modulated signal by time-or Spectrum Sensing (MRSS) feature. Analog implementation of frequency-domain signal processing. Its spectrum-sensing the MRSS block offers wideband, low-power, and real-time performance is robust to noise-like signals. However, this operation. From the system simulation results, MRSS achieved method demands excessive Analog-Digital Converter (ADC) 15-, 20-, and 30-dB detection margin for FM, VSB, and OFDM requirement and signal processing capabilities, thus, signals, having the corresponding signal power of -110, -120, accompanying a large amount of power consumption. and -120 dBm, respectively.

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phase difference is attributed to the unbalanced characteristics of the varactor diodes and 3-dB couplers. CONCLUSIONA novel and compact variable power divider based on 3-dB couplers and varactor diodes is proposed in this article. The variable power divider is initially studied using the even-and odd-mode techniques. Then, based, on the obtained equations a variable power divider operating in the frequency range 2.3-2.7 GHz was fabricated and measured. The measured results reveal that the proposed structure offers a dynamic range of minimum 6 dB, whereas the reflection losses are greater than À13 dB, regardless of the dc bias conditions. It is, however, believed that the dynamic range can be extended by using balanced varactor diodes in the circuit of the reflective loads. The proposed structure is, particularly, suitable for the implementation in the circuit of a variable input power for the Doherty amplifier, due to its inherent 90 o and continuous input power distribution.

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