Researchers experiment on micro-electro-mechanical systems at Tianjin University. Photo: Bai Yunyi/GT

The family of Zhang Hao, a Chinese professor from Tianjin University arrested in May 2015 by the US and charged with economic espionage, said the US justice system is unfair, after a federal judge convicted Zhang of economic espionage on Friday. 

The court rejected evidence presented by Chinese lawyers, a Zhang's family member told the Global Times on Saturday. 

The family member said the sentencing hearing will be held on August 31, and Zhang faces a jail term of between 40 and 50 months. The family is fighting for a shorter sentence, he said. 

A federal judge convicted Zhang on Friday of economic espionage, stealing trade secrets and engaging in a conspiracy for the benefit of the Chinese government after a four-day trial, US media reported. 

The decision came five years since Zhang, then 36, was arrested when he landed at Los Angeles International Airport to attend an international academic conference. The invitation to the conference was reportedly a trap set by the FBI.

US prosecutors said Zhang stole secrets from two companies, Skyworks Solutions, based in Massachusetts, and Avago Technologies, based in California, media reported. 

A source familiar with the case told the Global Times that Zhang's company, ROFS Microsystem, filed a lawsuit in Tianjin in September 2017 against Apple for intellectual property infringement. The suit came after ROFS found their patent technologies being used in filter chips sold to Apple in 2016 by Avago Technologies, now combined into US chipmaker Broadcom Inc. 

Zhang and his colleague Pang Wei were charged with stealing Avago technology when they worked in the US and brought it to Tianjin University and ROFS. 

But the source said Zhang and Pang obtained patents for seven technologies in the US and 200 others after they returned to China, which were being used in filter chips Avago sold to Apple. 

Zhang was released on $50,000 bail on July 29, 2015, but has not been allowed to leave California. 

His wife previously told the Global Times that he was under great psychological pressure, and his health declined. Zhang is only allowed freedom of activity from 7 am to 9 pm in northern California, and has to wear a monitoring device.