⚡ electrical engineering

Multistatic J-Band Radar TX/RX Chipset in SiGe BiCMOS with Integrated x16 Frequency Multiplier Chain and High EIRP

This paper presents a 292 GHz multistatic J-band radar chipset fabricated in 130 nm SiGe BiCMOS technology, featuring integrated x16 frequency multipliers, a 41 dBm EIRP transmitter, and a high-gain receiver that enables long-range measurements up to 150 meters.

Original authors: Stephan Hauptmeier, Kennet Braasch, Till Ziegler-Bellenberg, Diana P. Cortes N., Tobias T. Braun, Michael Höft, Nils Pohl

Published 2026-06-19

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CC BY 4.0

Original authors: Stephan Hauptmeier, Kennet Braasch, Till Ziegler-Bellenberg, Diana P. Cortes N., Tobias T. Braun, Michael Höft, Nils Pohl

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are trying to have a conversation with a friend across a very long, foggy hallway. The problem is that your voice (the signal) gets lost in the fog (the air) very quickly, and your friend's ears (the receiver) aren't sensitive enough to hear you unless you shout extremely loud.

This paper describes a new "super-ear and super-mouth" system built on a tiny silicon chip that solves this problem for a specific type of invisible light called J-band radar (which operates at frequencies around 292 GHz). This technology is used for things like seeing through fog or scanning objects without touching them.

Here is how the authors built this system, explained simply:

1. The "Whisper-to-Shout" Machine (The Transmitter)

The biggest challenge in this frequency range is that it's hard to generate a strong signal directly. It's like trying to shout a specific high note that your vocal cords can't naturally reach.

The Solution: Instead of shouting the high note directly, the chip starts with a low, easy-to-make "hum" (a low-frequency signal).
The Magic Trick: The chip has a built-in machine that acts like a gearbox. It takes that low hum and multiplies it by 16 times, 16 times, 16 times, and so on, until it becomes the high-pitched shout needed for the radar.
Cleaning the Noise: When you multiply a sound that many times, you usually create a lot of "garbage noise" (harmonics) that sounds like static. The authors built special filters (like a sieve) into the machine to throw away the garbage noise, keeping only the clean, pure signal.
The Amplifier: Once the signal is high-pitched, it's still too quiet to travel far. The chip uses a "power combiner" (like four people shouting in perfect unison) to make the signal loud enough to travel a long distance.
The Result: They achieved a "loudness" (EIRP) of 41 dBm when using a special lens, which is significantly louder than previous attempts. Without the lens, it's still a solid 8.8 dBm.

2. The "Super-Ear" (The Receiver)

On the other side of the hallway, you need a receiver that can hear that faint echo.

The Setup: This chip also has the same "gearbox" machine to create a reference signal.
The Amplifier: It uses a "Low-Noise Amplifier" (LNA). Think of this as a very sensitive microphone that turns up the volume of the faint echo without adding its own static hiss.
The Mix: It compares the echo it hears with the reference signal to figure out exactly how far away the object is.
The Result: It is incredibly sensitive, able to detect signals that have traveled far and lost most of their energy.

3. The "Antenna Glasses"

The chips have tiny antennas built right onto them.

Without Glasses: These antennas are like wide-angle eyes. They can see everything in a wide area, but they aren't very good at seeing things far away.
With Glasses: The authors added a special plastic lens (made of PTFE) that acts like a magnifying glass. This focuses the beam into a tight, powerful laser-like spot. This allows the radar to see objects much further away.

4. The "Two-Person Team" (Multistatic Design)

Usually, radar transmitters and receivers are packed tightly together. But at these high frequencies, the loud transmitter can deafen the sensitive receiver.

The Innovation: This system is "multistatic," meaning the transmitter and receiver are on separate chips that can be placed apart from each other.
The Benefit: It's like having the person shouting stand on one side of the room and the person listening stand on the other. This prevents the shout from drowning out the whisper, allowing both to work at their maximum potential.

5. The Real-World Test

To prove it works, the team set up their chips in a hallway.

They used a moving metal triangle (a corner reflector) as a target.
They successfully detected this target from 150 meters away (about 1.5 football fields).
Even though the hallway had doors and walls that created confusing echoes (ghost targets), the system was smart enough to distinguish the real target from the background noise.

Summary

In short, the authors built a tiny, highly efficient radar system on a silicon chip. They solved the problem of generating high-frequency signals by using a clever "multiplier chain" (gearbox), cleaned up the noise with filters, and used a "multistatic" setup to keep the loud transmitter from interfering with the sensitive receiver. The result is a radar that can see objects clearly at long distances, even at very high frequencies where this is usually very difficult.

Technical Summary: Multistatic J-Band Radar TX/RX Chipset in SiGe BiCMOS

Problem Statement
Sub-terahertz (Sub-THz) frequencies, particularly the J-band (220–330 GHz), offer significant potential for advanced radar applications such as medical screening, imaging, and non-destructive testing due to their large available bandwidth and high range resolution. However, practical deployment of these systems is currently hindered by high path loss, limited transmission power, and high receiver noise figures, which result in low signal-to-noise ratios (SNR). Existing demonstrators often rely on bulky, expensive vector network analyzers (VNA) with frequency extenders, which are unsuitable for scalable, cost-effective applications. Furthermore, achieving high Equivalent Isotropically Radiated Power (EIRP) and high receiver sensitivity simultaneously in a compact, integrated form factor remains a challenge, particularly when managing harmonic spurs generated by high-frequency multiplication chains.

Methodology
This work presents the design and measurement of a multistatic radar chipset comprising a Transmitter (TX) and Receiver (RX) Monolithic Microwave Integrated Circuit (MMIC), both realized in IHP's 130 nm SiGe BiCMOS technology (featuring HBTs with $f_T$ of 500 GHz and $f_{max}$ of 610 GHz).

Architecture: The system utilizes a multistatic architecture where the TX and RX are spatially separated but share a correlated low-frequency Local Oscillator (LO) signal. Both MMICs integrate an on-chip $\times$ 16 frequency multiplier chain, allowing the LO to be distributed below 21 GHz, thereby minimizing distribution losses and costs.
Transmitter Design: The TX MMIC incorporates the $\times$ 16 multiplier chain followed by a four-stage, four-way power-combining amplifier chain. The multiplier chain consists of an active balun, preamplifiers, and four doubler stages (utilizing push-push and bootstrapped Gilbert cell topologies) interspersed with bandpass filters to suppress harmonics. The final stage drives a differential rectangular on-chip patch antenna.
Receiver Design: The RX MMIC integrates the same $\times$ 16 multiplier chain to generate the LO for a fundamental down-conversion mixer. The RF signal is captured by an on-chip patch antenna and amplified by a three-stage Low-Noise Amplifier (LNA) before mixing. The LNA employs a series transmission line input matching network to simultaneously optimize noise figure and input return loss.
System Integration: The MMICs are mounted on separate PCBs with integrated collimating PTFE lenses to enhance gain and directivity for long-range measurements.

Key Contributions and Results

High EIRP Transmitter: The integrated four-way power-combining amplifier delivers an output power of 11.2 dBm. With a collimating PTFE lens, the system achieves a measured EIRP of 41 dBm at 292 GHz. Without the lens, the EIRP is 8.8 dBm, providing a wide field of view.
Harmonic Rejection: Despite the high multiplication factor of 16, the design achieves robust harmonic suppression. On-chip harmonic rejection is better than 24 dBc, while the radiated in-band harmonic rejection reaches approximately 50 dBc through the combination of multiple filter stages in the multiplier chain and the filtering response of the patch antenna.
Receiver Sensitivity: The RX MMIC achieves an overall conversion gain of 43.3 dB at 292 GHz. The noise figure was measured to be approximately 20 dB at 285 GHz (inclusive of the antenna), which aligns with state-of-the-art performance.
Bandwidth: The system demonstrates a 3 dB bandwidth of 31.7 GHz and a 10 dB bandwidth of 88 GHz, covering a significant portion of the J-band.
Long-Range Demonstration: FMCW radar measurements were conducted in a hallway environment. The system successfully detected a moving corner reflector at distances up to 150 meters, validating the long-range capability of the chipset despite the high center frequency.

Significance
The paper claims that this work advances the state of the art by successfully integrating a high-power transmitter and a sensitive receiver into a scalable, multistatic SiGe BiCMOS chipset. By leveraging the multistatic architecture, the system minimizes TX-RX coupling, enabling the use of high-power amplifiers without receiver saturation. The integration of the $\times$ 16 multiplier chain allows for low-frequency LO distribution, facilitating scalable radar configurations with multiple modules. The achieved EIRP of 41 dBm exceeds previously reported values for J-band radar transmitters (e.g., 27 dBm and 31 dBm in prior works), demonstrating that high-performance Sub-THz radar systems can be realized in silicon-based technologies without relying on bulky external instrumentation. The successful 150 m range measurement confirms the practical viability of this chipset for long-range radar applications.