With the rise of high-speed wireless communication devices like 5G mobile phones and sensors for autonomous vehicles, the airwaves are becoming increasingly crowded.
This makes blocking interference to improve device performance both more important and more challenging.
To address this, researchers at MIT have created a new wireless receiver architecture that can handle stronger interference than previous designs, enhancing mobile device performance.
The innovative receiver uses a system called millimeter-wave multiple-input-multiple-output (MIMO).
MIMO systems have multiple antennas, allowing them to send and receive signals from different directions.
This new receiver architecture can sense and block unwanted signals before they are amplified, which significantly improves performance.
Key to this new receiver design is a special circuit called a nonreciprocal phase shifter. This circuit can target and cancel out unwanted signals.
By making a new type of phase shifter that is reconfigurable, low-power, and compact, the researchers showed how it can block interference earlier in the receiver process.
The new receiver can block up to four times more interference than some similar devices. Additionally, the interference-blocking components can be turned on and off as needed to save energy.
In a mobile phone, this receiver could help avoid issues like slow and choppy video calls.
“There is already a lot of usage in the frequency ranges for new 5G and 6G systems, so we need these interference-mitigation systems installed,” says Negar Reiskarimian, the senior author of the paper and an assistant professor at MIT.
“Using a nonreciprocal phase shifter in this new architecture gives us better performance.”
Reiskarimian wrote the paper with graduate students Shahabeddin Mohin, the lead author, Soroush Araei, Mohammad Barzgari, and the team presented it at the IEEE Radio Frequency Circuits Symposium, winning the Best Student Paper Award.
Digital MIMO systems have both analog and digital parts. The analog part uses antennas to receive signals, which are then amplified and converted into digital form before being processed.
If a strong interfering signal hits the receiver along with the desired signal, it can drown out the desired signal. Digital MIMOs can filter out unwanted signals, but this happens later in the process, making it harder to remove interference if it has already been amplified.
“The output of the initial low-noise amplifier is the first place you can do this filtering with minimal penalty, so that is exactly what we are doing with our approach,” Reiskarimian explains.
The researchers installed four nonreciprocal phase shifters at the output of the first amplifier in each receiver chain.
These phase shifters can pass signals in both directions and sense the angle of an incoming interfering signal, adjusting their phase until they cancel out the interference.
Because the phase shifters can be precisely tuned, they can block unwanted signals before they affect other parts of the receiver. They can also adapt if the interference changes location, providing continuous protection.
“If your signal quality goes down, you can turn this on and mitigate interference on the fly,” adds Reiskarimian. “You can turn it on and off with minimal effect on the performance of the receiver itself.”
The researchers also made their phase shifters compact and energy-efficient. They demonstrated a MIMO architecture on a 3.2-square-millimeter chip that could block much stronger signals than other devices.
Their design is simpler and more efficient than typical designs.
Looking ahead, the researchers plan to scale up their device for larger systems and enable it to work in the new frequency ranges used by 6G devices, which are prone to interference from satellites. They also aim to adapt the phase shifters for other applications.
This advanced wireless receiver promises to improve mobile device performance by effectively blocking interference, ensuring smoother communication and better connectivity.
Source: MIT.
