arXiv subjects

Hamed Rahmani

Publications and source records attributed to Hamed Rahmani.

4 recordsLinked to original sources

arXiv2026

Interference-Tolerant Mixer-First Receivers for FR3: Design Principles and Tradeoffs

Frequency Range 3 (FR3), spanning 7.125-24.25 GHz, is a promising candidate band for 6G communications, bridging the coverage of sub-6 GHz bands and the capacity of millimeter-wave frequencies. Its incumbent-dense and non-contiguous spectrum demands frequency-agile, interference-tolerant receivers (RXs) capable of hopping across fragmented sub-bands while withstanding strong blockers. Mixer-first RXs are well suited to this role, yet their design for FR3 has not been systematically addressed. This paper presents a hardware design perspective on mixer-first RXs for FR3, evaluating selectivity enhancement, harmonic rejection, linearization, low-noise design, and multi-phase clock generation under FR3-specific constraints. The analysis identifies viable techniques, fundamental limitations, and circuit- and architecture-level design tradeoffs. A central insight is that the frequency-translational property of mixer-first RXs allows selectivity, linearization, and noise cancellation to be implemented partly at baseband and translated to RF, enabling frequency-agile FR3 operation while shifting the dominant design constraints to mixer parasitics, baseband circuit robustness, and multi-phase clock generation.

eess.SP↗

arXiv2025

Four-Port Probe Stations and SOLR Calibration Standard Design up to 125 GHz on 28 nm CMOS

This paper presents two innovative four-port probe stations developed by FormFactor Incorporated (FFI) and MPI Corporation (MPI), and a four-port calibration standard design up to 125 GHz for the probe stations. True four-port probing at mmWave and beyond does not yet exist, but is anticipated for future multi-band wireless devices using several antennas and RF chains. The four-port probe stations are housed in the THz measurement facility at NYU and allow simultaneous probing from East, West, North, and South orientations, which presents challenges for calibration. An on-chip Short-Open-Load-Reciprocal (SOLR) calibration (cal) standard is designed leveraging UMC's 28 nm CMOS process. S/O/L standard S-parameters are extracted using a virtual multiline Thru-Reflect-Line (mTRL) cal and used to validate SOLR cal performance via simulations up to 125 GHz. The novel probing solutions from MPI and FFI, along with the SOLR cal, open up considerable opportunities for precise RF characterization across wide frequency ranges.

eess.SY↗

arXiv2024

Masala-CHAI: A Large-Scale SPICE Netlist Dataset for Analog Circuits by Harnessing AI

Masala-CHAI is a fully automated framework leveraging large language models (LLMs) to generate Simulation Programs with Integrated Circuit Emphasis (SPICE) netlists. It addresses a long-standing challenge in circuit design automation: automating netlist generation for analog circuits. Automating this workflow could accelerate the creation of fine-tuned LLMs for analog circuit design and verification. In this work, we identify key challenges in automated netlist generation and evaluate multimodal capabilities of state-of-the-art LLMs, particularly GPT-4, in addressing them. We propose a three-step workflow to overcome existing limitations: labeling analog circuits, prompt tuning, and netlist verification. This approach enables end-to-end SPICE netlist generation from circuit schematic images, tackling the persistent challenge of accurate netlist generation. We utilize Masala-CHAI to collect a corpus of 7,500 schematics that span varying complexities in 10 textbooks and benchmark various open source and proprietary LLMs. Models fine-tuned on Masala-CHAI when used in LLM-agentic frameworks such as AnalogCoder achieve a notable 46% improvement in Pass@1 scores. We open-source our dataset and code for community-driven development.

cs.AR↗

arXiv2024

Cellular Wireless Networks in the Upper Mid-Band

The upper mid-band - roughly from 7 to 24 GHz - has attracted considerable recent interest for new cellular services. This frequency range has vastly more spectrum than the highly congested bands below 7 GHz while offering more favorable propagation and coverage than the millimeter wave (mmWave) frequencies. The upper mid-band can thus provide a powerful and complementary frequency range to balance coverage and capacity. Realizing the full potential of these bands, however, will require fundamental changes to the design of cellular systems. Most importantly, spectrum will likely need to be shared with incumbents including communication satellites, military RADAR, and radio astronomy. Also, the upper mid-band is simply a vast frequency range. Due to this wide bandwidth, combined with the directional nature of transmission and intermittent occupancy of incumbents, cellular systems will need to be agile to sense and intelligently use large spatial and frequency degrees of freedom. This paper attempts to provide an initial assessment of the feasibility and potential gains of wideband cellular systems operating in the upper mid-band. The study includes: (1) a system study to assess potential gains of multi-band systems in a representative dense urban environment and illustrate the value of wide band system with dynamic frequency selectivity; (2) an evaluation of potential cross interference between satellites and terrestrial cellular services and interference nulling to reduce that interference; and (3) design and evaluation of a compact multi-band antenna array structure. Leveraging these preliminary results, we identify potential future research directions to realize next-generation systems in these frequencies.

cs.NI↗