Photo source: ROFS Microsystem
ROFS Microsystem (Tianjin) Co., Ltd. said on June 12 it has filed a patent infringement lawsuit against Wuhan MEMSonics New Technologies Co., Ltd. with a Shenzhen court, alleging that the rival's BAW filters infringe its invention patent.
The Shenzhen Intermediate People's Court has accepted the case for docketing, ROFS said in a statement carried on its official WeChat account. The company said the litigation is aimed at safeguarding its lawful rights and warned relevant parties of potential risks associated with using infringing products.
Wuhan MEMSonics responded later on Friday, saying it had not received any court documents and that its products were developed through independent research and development. The company said its filters do not incorporate all the technical features recited in the asserted patent claims and therefore do not constitute infringement.
ROFS, established in September 2011, is one of China's earliest BAW filter developers and operates a dedicated 6-inch production line in the northern city of Tianjin under an IDM model. Wuhan MEMSonics, founded in 2019 by Professor Sun Chengliang of Wuhan University, focuses on high-end radio frequency filters. Both companies are leading players in China's domestic BAW filter sector, which has seen intensifying competition.
The patent at the centre of the dispute, ZL201010267632.6, covers a piezoelectric resonator structure. It was filed in August 2010 by ROFS founders Pang Wei and Zhang Hao and granted in October 2012.
The same patent was at the heart of a high-profile legal battle between ROFS and U.S. chipmaker Broadcom Inc. In 2017, ROFS sued Apple Inc. and its supplier Avago Technologies –now Broadcom – before a Tianjin court, alleging that filter chips used in multiple iPhone models infringed its patent. Avago then filed a counterclaim with the same court seeking ownership of the patent, while Apple challenged the patent's validity before the Beijing Intellectual Property Court.
The dispute ended on July 3, 2024, when ROFS announced a global settlement with Broadcom. Both sides withdrew all pending lawsuits and entered into a cross-licensing agreement covering certain Chinese patents.
According to records from the China National Intellectual Property Administration, the patent was partially invalidated in October 2017, with claims 1 and 2 struck down while claims 3 through 15 were upheld. A preservation order was placed on the patent in March 2024 and lifted in March 2025.
In February 2026, ROFS filed another patent suit based on the same patent with the Shenzhen court, this time against Heyuan Aifo Guangtong Technology Co., Ltd.
