Full-duplex (FD) wireless is an emerging wireless communication paradigm where the transmitter and the receiver operate simultaneously at the same frequency. One major challenge in realizing FD wireless is the interference of the TX signal saturating the receiver, commonly referred to self-interference (SI). Traditionally, self-interference cancellation (SIC) is achieved in the antenna, RF/analog, and digital domains. In the antenna domain, SIC can be achieved using a pair of separate TX and RX antennas, or using a single antenna shared by the TX and RX through a magnetic circulator, which is usually bulky, expensive, and not integrable with CMOS. Recent advances, however, have shown the feasibility of realizing high-performance non-reciprocal circulators in CMOS based on spatio-temporal modulation. In this work, we demonstrate a high power handling FD radio using a USRP SDR which employs SIC (i) at the antenna interface using a watt-level power-handling CMOS integrated, magnetic-free circulator, (ii) in the RF domain using a compact RF canceler, and (iii) in the digital domain. Our prototyped FD radio achieves +95 dB overall SIC at +15dBm TX power level. We analyze the effects of the circulator TX-RX non-linearity on the total achievable SIC
Radio frequency transmitter based on a laser frequency comb
Since the days of Hertz, radio transmitters have evolved from rudimentary circuits emitting around 50 MHz to modern ubiquitous Wi-Fi devices operating at gigahertz radio bands. As wireless data traffic continues to increase, there is a need for new communication technologies capable of high-frequency operation for high-speed data transfer. Here, we give a proof of concept of a compact radio frequency transmitter based on a semiconductor laser frequency comb. In this laser, the beating among the coherent modes oscillating inside the cavity generates a radio frequency current, which couples to the electrodes of the device. We show that redesigning the top contact of the laser allows one to exploit the internal oscillatory current to drive a dipole antenna, which radiates into free space. In addition, direct modulation of the laser current permits encoding a signal in the radiated radio frequency carrier. Working in the opposite direction, the antenna can receive an external radio frequency signal, couple it to the active region, and injection lock the laser. These results pave the way for applications and functionality in optical frequency combs, such as wireless radio communication and wireless synchronization to a reference source.
- Publication Date:
- NSF-PAR ID:
- 10101658
- Journal Name:
- Proceedings of the National Academy of Sciences
- Page Range or eLocation-ID:
- Article No. 201903534
- ISSN:
- 0027-8424
- Publisher:
- Proceedings of the National Academy of Sciences
- Sponsoring Org:
- National Science Foundation
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Full-duplex (FD) wireless is an emerging wireless communication paradigm where the transmitter and the receiver operate simultaneously at the same frequency. One major challenge in realizing FD wireless is the interference of the TX signal saturating the receiver, commonly referred to self-interference (SI). Traditionally, self-interference cancellation (SIC) is achieved in the antenna, RF/analog, and digital domains. In the antenna domain, SIC can be achieved using a pair of separate TX and RX antennas, or using a single antenna shared by the TX and RX through a magnetic circulator, which is usually bulky, expensive, and not integrable with CMOS. Recent advances, however, have shown the feasibility of realizing high-performance non-reciprocal circulators in CMOS based on spatio-temporal modulation. In this work, we demonstrate a high power handling FD radio using a USRP SDR which employs SIC (i) at the antenna interface using a watt-level power-handling CMOS integrated, magnetic-free circulator, (ii) in the RF domain using a compact RF canceler, and (iii) in the digital domain. Our prototyped FD radio achieves +95 dB overall SIC at +15dBm TX power level. We analyze the effects of the circulator TX-RX non-linearity on the total achievable SIC.
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