Mao, an associate professor at Xiamen University in China who also became a visiting professor at a Texas university last autumn, first gained attention as part of a Texas civil case between Huawei and Silicon Valley startup CNEX Labs Inc.
Huang, a former engineering manager at a US Huawei subsidiary, helped start CNEX in 2013, three days after leaving the company.
As part of its counterclaims, CNEX said Mao had asked for one of its circuit boards for a research project and that, after it sent the board to the professor, he used it for a study tied to Huawei.
Now, US prosecutors who have a case against Huawei in Brooklyn for alleged bank fraud and Iran sanctions violations, have revived the CNEX case.
Although the company has not been charged, Huawei said it views the case against Mao as the US government's latest instance of "selective prosecution".
"US federal prosecutors are charging forward with CNEX's allegations" despite the outcome of the civil case, a Huawei spokesman said in a statement, adding that US prosecutors had shown no interest in Huawei's claims against CNEX.
In January, US prosecutors announced an indictment against Huawei for trade secret theft involving T-Mobile, following a civil case between those companies.