Researchers at the Massachusetts Institute of Technology (MIT) have unveiled a groundbreaking low-power, compact receiver designed to enhance the performance of 5G-compatible smart devices. This innovative receiver boasts an impressive resistance to a specific type of interference, outperforming traditional wireless receivers by approximately 30 times.
This cost-effective receiver is particularly well-suited for battery-operated Internet of Things (IoT) devices, including environmental monitoring sensors, smart thermostats, health trackers, smart cameras, and industrial sensors that require longevity and continuous operation. The newly developed chip utilizes a passive filtering strategy, consuming less than one milliwatt of static power while effectively shielding both the input and output of the receiver’s amplifier from disruptive wireless signals that could compromise functionality.
The key to this technological advancement lies in a unique configuration of precharged, stacked capacitors interconnected by a network of minuscule switches. These switches demand considerably less power for activation compared to those commonly used in IoT receivers. By thoughtfully organizing the capacitor network alongside the amplifier, researchers are able to exploit amplification phenomena, allowing the use of much smaller capacitors than would typically be required.
Lead author Soroush Araei, an electrical engineering and computer science graduate student at MIT, emphasized the potential impact of this receiver on the IoT landscape. “This receiver could help expand the capabilities of IoT gadgets. Smart devices such as health monitors or industrial sensors could become smaller and have longer battery lives, while also being more reliable in crowded radio environments like factory floors or smart city networks,” Araei stated.
Joining Araei in the research are co-authors Mohammad Barzgari, a postdoctoral researcher at the MIT Research Laboratory of Electronics; Haibo Yang, another EECS graduate student; and senior author Negar Reiskarimian, an assistant professor in EECS at MIT and a member of the Microsystems Technology Laboratories. Their findings were recently showcased at the IEEE Radio Frequency Integrated Circuits Symposium.
A receiver serves as a crucial link between IoT devices and their surrounding environment, capable of detecting and amplifying wireless signals, filtering out interference, and converting the data into a digital format. Traditional IoT receivers typically rely on fixed frequencies, using a single narrow-band filter for simplicity and cost-effectiveness. However, the rollout of the new 5G mobile network presents opportunities for creating affordable and energy-efficient IoT devices equipped with receivers that can operate across a wide frequency spectrum.
As Araei pointed out, “This is extremely challenging because we now need to consider not only power and cost but also flexibility to address numerous interferences in the environment.” Engineers must move away from bulky, off-chip filters that are usually employed in wide-frequency devices.
In prior research, the MIT team introduced a switch-capacitor network designed to target harmful harmonic signals early in the receiving process, thereby filtering out unwanted interference before amplification and digital conversion take place. They have further refined this strategy by utilizing the switch-capacitor network as a feedback pathway in amplifiers with negative gain, capitalizing on the Miller effect to enable small capacitors to emulate larger ones.
This innovative approach significantly minimizes the size of the circuit, with the receiver measuring less than 0.05 square millimeters in active area. One challenge faced during development was ensuring sufficient voltage for the switches while maintaining the overall chip power supply at a mere 0.6 volts. To overcome this, researchers implemented bootstrap clocking, a technique that elevates control voltage sufficiently to ensure reliable switch operation while conserving power and components.
Collectively, these advancements allow the new receiver to block approximately 30 times more harmonic interference than its traditional counterparts while consuming under a milliwatt of power. Araei highlighted the low interference of their chip, noting that its compact switches generate minimal signal leakage. Due to its size and reliance on simpler components, the receiver can potentially offer cost-efficient fabrication.
Looking ahead, researchers aim to make the receiver operable without a dedicated power supply, possibly through the harvesting of ambient Wi-Fi or Bluetooth signals. This research has received support in part from the National Science Foundation.
