TACS-RF: Tool-driven Agentic Circuit Synthesis of RF and mmWave Modules

Tristan Liang; Aravind Nagulu

cs.AIOct 22, 2026

TACS-RF: Tool-driven Agentic Circuit Synthesis of RF and mmWave Modules

Authors: Tristan Liang, Aravind Nagulu

Organizations: Department of Electrical and Computer Engineering, Northeastern University, Oakland Campus, CA 94613

Abstract

We present the framework of TACS-RF - a Tool-driven Agentic Circuit Synthesis of RF and mmWave modules. In this framework, a large-language-model (LLM) coding agent (Claude Opus 4.8) directly drives industry-standard electronic-design-automation (EDA) tools such as Cadence Virtuoso/Spectre, Calibre, Cadence EMX, and Ansys HFSS to design RF and mmWave modules. We validate the framework through the agentic design of a 240-251 GHz sub-THz transmitter in a 90 nm SiGe BiCMOS process. The agent semi-autonomously designed the sub-blocks including a 60 GHz push-push Colpitts VCO with second-harmonic extraction, multistage differential cascode power drivers, a push-push frequency doubler, a differential bowtie antenna, and all the interstage matching networks. The transmitter chain with parasitic-extracted devices and EM-verified passives delivers +5.1 to +6.3 dBm across an 11 GHz varactor-only tuning range, phase noise of -80 to -88 dBc/Hz at 1 MHz offset while consuming a DC power of 361 mW. We describe the agent-driven design flow and the resulting division of labor between human and agent, taking a step toward a "text-to-ASIC" future for designing RF/mmWave hardware.

Figures & tables

Fig. 1: An LLM-driven EDA workflow for RF and mmWave circuit design that integrates Cadence Virtuoso, EMX, HFSS/PyAEDT, and Calibre.

Fig. 2: Design flow of the sub-THz transmitter, demonstrating complete automation by the LLM agent from initial setup to the final AI-generated layout.

Fig. 3: A representative design guideline provided to the LLM-agent.

Fig. 4: Agent-designed 240–251 GHz transmitter. (a) Complete transmitter schematic in a 90 nm SiGe BiCMOS process. (b) Automated design results for the small signal inter-stage matching and achieved performance benchmarks. (c) Simulated performance of the 60 GHz VCO with second harmonic extraction. (d) Schematic and lumped model based performance optimization of the sub-THz transmitter across varying number of driver stages. (e) Simulations of the transmitter with 2 driver stages with EM extracted passives and RCC-extracted devices: output power ( $P_{out}$ ) and phase noise (PN) at a 1 MHz offset across the varactor $V_{tune}$ sweep. The operating frequency is limited by the varactor tuning range.

Fig. 5: TACS-RF framework performing EM simulations using Ansys HFSS and Cadence EMX. A representative transformer balun design in EMX: (a) layout and (b) extracted parameters. A 240 GHz antenna design in HFSS: (c) antenna layout, and (d) simulated input matching, gain, and directivity.

Reference	Process	$f_{T}/f_{max}$	Frequency	$P_{out}$	$P_{dc}$	Phase Noise
		(GHz)
[ 5 ] a	0.13 $\mu$ m SiGe	300/500	229–251 GHz	1–2 dBm	0.29 W	$-$ 85 dBc/Hz @ 1 MHz
[ 6 ] b	55 nm SiGe	330/350	234–261 GHz	5.4–7.2 dBm	0.38 W	$-$ 105 dBc/Hz @ 10 MHz
This work c	90 nm SiGe	300/350	240–251 GHz	5.1–6.3 dBm	0.36 W	$-$ 88 d @ 1 MHz; $-$ 108 d @ 10 MHz
a Push-push VCO + PA + doubler. b 120 GHz VCO + LO tree + doubler. c Push-push VCO + 2 PAs + doubler. d operating at 248 GHz.

TABLE I: Comparison With Prior Sub-THz SiGe Sources

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