Summary:
UCLA researchers in the Department of Electrical and Computer Engineering have developed a low-noise, DiCAD-based fractional frequency synthesis system that enables fine frequency resolution and enhanced signal stability for millimeter-wave applications.
Background:
Millimeter-wave (mmW) communication and radar systems demand carrier frequency synthesizers with low phase noise and fine frequency resolution. Conventional solutions often rely on integer-N phase-locked loops (PLLs) combined with delta-sigma modulators driving multi-modulus dividers to achieve fractional frequency tuning. However, at mmW frequencies, the large frequency multiplication factors inherent in these architectures significantly amplify reference noise, in-band spurious tones, and quantization noise by 20logN. Thus, there is an unmet need for a fractional frequency synthesis technique that avoids this noise and spurs scaling, enabling high-performance mmW operation.
Innovation:
Professor Mau-Chung Chang and his research team have developed a novel fractional frequency synthesis architecture that minimizes noise amplification and improves signal stability at millimeter-wave frequencies. The system employs a DiCAD-based digital-to-phase modulator (DPM) to achieve arbitrarily fine frequency resolution while eliminating traditional 20logN scaling of quantization noise and spurious tones. By distributing distortion power across the modulator’s switching frequency, the quantization noise power spectral density (PSD) approaches a near-uniform distribution. This allows effective noise shaping, enabling a low-pass filter to significantly suppress the noise profile. Furthermore, the phase-locked loop (PLL) bandwidth can be reduced to approximately 10% of the reference frequency, improving out-of-band noise rejection and overall spectral purity. This innovation offers a scalable, low-noise solution for next-generation mmW communication, radar, and sensing systems.
Potential Applications:
● 5G/6G networks
● Automotive radar
● Imaging and sensing
● Satellite communications and defense applications
● Quantum computing systems
Advantages:
● Eliminated noise and spur scaling
● Flatter quantization noise spectrum
● Narrower PLL bandwidth for better noise suppression
● High frequency resolution with low phase nose
● Scalable for mmW systems
State of Development:
First description of the complete invention June 2025.
Related Publications:
1. M.-C. F. Chang, D. Huang, and W. Hant, "Tunable Artificial Dielectrics," US Patent 8164401 B2, Apr 24, 2012
2. M.-C. F. Chang, D. Huang, and W. Hant, "Tunable Artificial Dielectrics," US Patent 7852176 B2, Dec 14, 2010
3. T. LaRocca et al., "Millimeter-wave CMOS digital controlled artificial dielectric differential mode transmission lines for reconfigurable ICs," 2008 IEEE MTT-S International Microwave Symposium Digest, Atlanta, GA, USA, 2008, pp. 181-184.
4. J. Zhou et al., “A 71-86GHz 1024QAM Direct-Carrier Phase-Modulating Transmitter with Digital-to-Phase Converters and Constant-Envelope Phasors”, 2025 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), San Francisco, CA, USA, 2025. (Accepted)
Reference:
UCLA Case No. 2025-9AA
Lead Inventor:
M.C. Frank Chang, Distinguished Professor and Wintek Chair, Electrical and Computer Engineering