ECE Special Seminar: Active N-path filters and other recent research activities


Booker Conference Room, Jacobs School of Engineering, 9500 Gilman Dr, La Jolla, San Diego, California 92093

Sponsored By:

Milad Darvishi


Nowadays, wireless devices cover numerous wireless communication standards where almost for each one a different frequency band has been allocated. There is a strong motivation towards SoC (System-on-Chip) solutions, where everything is integrated inside a chip to reduce the cost and form-factor of wireless devices. In radio-frequency receivers, due to the existence of large out-of-band blockers and limited dynamic range, band-select filtering of the input signal is essential. Currently, most of the frontend circuitry of transceivers can be integrated on-chip. However, it is not possible to build integrated high-performance band-pass filters even after more than a decade research on this very topic. The inherent losses associated with on-chip inductors lead to filters having relatively high insertion losses, limited dynamic range and low out-of-band rejection. For this reason, nowadays, most wireless systems utilize individual off-chip filters rather than fully integrated band-pass filters. This increases the size and cost. Moreover, most current wireless devices have several standards which leads to the exploitation of numerous off-chip band-pass filters which further exacerbate the size and cost issues. In this talk, we will present several filter designs that partially address this issue. These filters are based on N-path technique and MEMS. N-path filters can provide us with band-pass filters having high Q-factors and wide center-frequency tuning range. The center frequency of the N-path band-pass filter is set by its clock frequency and its bandwidth is determined by the value of its capacitors and source resistance. The principal constituents of N-path filters are switches, capacitors and a digital circuitry for providing clock signals needed for the operation of these filters. CMOS technology can offer very linear switches, high density capacitors and very fast digital gates. Therefore, CMOS technology is the best candidate for the implementation of N-path band-pass filters which are friendly with process scaling.

Furthermore, a new 60 GHz phase shifter and highly linear LNA for WLAN Front-End Module (FEM) application will be discussed briefly. We will demonstrate a new derivation of noise-cancelling receiver. Finally, I will have a short discussion about a technique for reducing the effect of phase noise in N-path filters.

Speaker Bio:
MILAD DARVISHI received the the B.S. degree from University of Tehran, Tehran, Iran in 2006, and the M.S. degree from Sharif University of Technology, Tehran, Iran in 2008 both in electrical engineering. He received his Ph.D. (cum laude) from university of Twente, Enschede, the Netherlands in 2013 on the subject of “Active N-path Filters” under the supervision of Prof. Bram Nauta. He was with Qualcomm, San Diego, USA as a senior RFIC engineer working on high-end cellular transceivers from 2013 to 2016. He specifically worked on improving the linearity and NF of the cellular receivers and developed a new N-path filter currently being utilized in the latest 14 nm Qualcomm’s cellular chipset.

Currently, he is with Broadcom Limited, Irvine, USA under the supervision of Dr. Hooman Darabi as a senior RFIC staff scientist working on several projects such as highly-linear Front-End Module (FEM) LNA for WLAN5G, a small low-power phase-shifter for 60 GHz and also conducting research on high dynamic-range receivers and filters for wireless applications. He has authored or co-authored several technical papers and patents.

Stefanie Battaglia,, Ph: (858) 534-7013