A Novel Simultaneous Frequency and Spatial Filtering Methodology for Beam-forming and Null-steering in Integrated Phased-Array Systems Using N-path technique

Karami, Poorya | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53520 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Atarodi, Mojtaba
  7. Abstract:
  8. In the communication systems, there are two types of blockers: in-band and out-of-band. High frequency pre-filters and band-pass filters can be used to suppress the out-of band blockers. However, using these methods does not affect the in-band interferers. Spatial filtering by means of phased array antennas and using frequency filtering can suppress both types of interferers. In a typical phased array receiver, all of the received signals pass through active blocks (such as LNAs, active phase shifters, driver amplifiers, etc.) that amplify the interferers before canceling them. Therefore, because of the high strength of the interferers, the dynamic range of the front-end blocks preceding combining node should be high enough which necessitates more power consumption. On the other hand, digital phased array systems require RF front-end blocks and analog-to-digital converters with a high dynamic range, so the RF front-end used in them must have an acceptable dynamic range to prevent receiver saturation. In this project, an architecture using N-path technique for spatio– spectral interference mitigation in the analog and RF domain for phased array systems has been proposed, that uses proprietary architecture in mixer-first phased array receivers for beamforming and null-steering purposes. Application of this technique in the front-end, causes the translation of frequency and spatial response to the antenna terminals. Therefore, spatial and frequency blockers will be suppressed at the antennas input. The proposed structure also has the ability to create multiple beam and null points simultaneously, which is another unique feature of the proposed phased array structure in this project. In the circuit implementation of the proposed structure, high-linearity transconductances are one of the key blocks in determining the overall performance of the proposed phased array. Therefore, a new transconductor with a novel linearization technique has been introduced. Also, with the help of the proposed transconductance, an adjustable filter at high frequencies using N-path circuits has been designed and implemented. In the following, a new systematic method for designing N-path filters is presented. Using this method, a special purpose filter can be synthesized and designed based on the user's requirements. The whole system is implemented in 180 nm CMOS technology and all the presented results in the dissertation are based on the post-layout simulation
  9. Keywords:
  10. Phased Array ; Beamforming ; Multi-Path Filters ; Transconductor ; Phase Shifter Circuit ; N-Path Filter

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