RF6G Sub-THz Measurements and Test Setup by Keysight
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This page delves into 6G Sub-THz measurements and the Sub-THz test setup offered by Keysight Technologies.
Introduction
The term “terahertz” or “THz” refers to frequencies in the range of Hz. Specifically, the frequencies from 300 GHz to 3 THz (i.e., 3000 GHz) constitute the THz spectrum range. The frequencies between 100 GHz and 300 GHz are referred to as sub-THz.
Terahertz frequencies offer higher bandwidths and shorter wavelengths. However, they also exhibit higher propagation and atmospheric losses compared to millimeter-wave frequencies.
6G measurements at sub-THz frequencies demand sophisticated and high-performance test equipment. Several test and measurement companies manufacture this equipment. Popular manufacturers of 6G wireless test equipment include Keysight, R&S, Anritsu, and NI.
6G technology follows in the footsteps of 4G LTE and 5G wireless technologies.
6G Sub-THz Measurements
The 6G wireless technology aims to achieve individual data rates of approximately 100 Gbps, potentially reaching up to 1 Tbps. This makes 6G wireless devices potentially 100 times faster than 5G technology.
The 6G testbed is primarily developed for testing sub-THz devices in the D-band (110 to 170 GHz) and G-band (140 to 220 GHz).
The following Sub-THz measurements are particularly useful during 6G device testing:
- Constellation Diagram
- Eye Diagram
- Power Spectrum with OBW (Occupied Bandwidth)
- Decoding of the 6G packet or frame
(Refer to articles on Baseband Measurements, Constellation diagram versus eye diagram and Error Vector Magnitude for further information.)
Sub-THz Test Setup for 6G Device Testing by Keysight
Figure 1 illustrates a common measurement setup used for 6G device testing.
The following Keysight equipment and RF components are used in this 6G Sub-THz test setup:
- AWG (Arbitrary Waveform Generator) Model M8195A: Used to generate a wideband IF centered at 6 GHz.
- VDI RF Up Converter: Operates at G-band frequencies, ranging from 140 to 220 GHz.
- PSG Vector Signal Generator Model E8267D: Used to generate the LO (Local Oscillator) frequency at 23 GHz.
- RF Filter (BPF) and VDI Amplifier
- Rectangular Horn Antennas: For OTA (Over The Air) Testing.
- VDI RF Down Converter
- Digitizer Model M8131A
- Keysight 89600 VSA Software
Figure-1 : Test Setup for 6G measurements at sub-THz frequencies
As shown in the figure, the AWG generates a wideband IF around a center frequency of 6 GHz with a 10 GHz bandwidth. The PSG generates a 23 GHz frequency, which is then multiplied by a factor of 6 to obtain a frequency of 138 GHz. This 138 GHz signal serves as the LO within the VDI up-converter.
The modulated IF at 6 GHz is mixed with the 138 GHz LO using the VDI up-converter. The up-converter produces a 144 GHz frequency, which is then filtered/amplified and fed to a horn antenna.
Another horn antenna is used at the receiver, placed approximately 35 cm apart for OTA (Over-The-Air) testing.
The received RF signal is down-converted and digitized. The digitized signal is then demodulated and analyzed using the Keysight VSA (Vector Signal Analyzer) software application running on a computer system. This allows observation of the constellation diagram and power spectrum. One can experiment with blocking the transmitted signal and observe the resulting changes in the constellation diagram and the received power level in the power spectrum.
The above setup demonstrates a SISO (Single Input Single Output) configuration, using one antenna for transmission and one for reception. Both the M8195A (AWG) and M8131A (Digitizer) support multiple channels, enabling MIMO testing.
Figure-2 : Testing receiver part of DUT using VSG
Figure-3 : Testing transmitter part of DUT using VSA
Figures 2 and 3 depict the use of a VSG and VSA for RF and baseband testing of a DUT (Device Under Test).
The setup includes a VSG (Vector Signal Generator) for testing the 6G DUT receiver and a VSA (Vector Signal Analyzer) for testing the 6G DUT transmitter.
As shown, both Keysight’s VSG and VSA are used for preparing the 6G testbed without any DUT in between. Once this calibration is performed, either the VSG or VSA can be used for DUT testing, to test the receiver or transmitter functionalities respectively.
(Refer to the article on the basics of Vector Signal Generation and Analysis for more information.)
About Keysight Technologies
Keysight Technologies, a US-based company headquartered in California, manufactures electronic test and measurement equipment, along with related T&M software. Keysight offers test and validation products for 4G LTE, 5G, 6G, IoT (Internet of Things), 800G, quantum solutions, automotive manufacturers, and more. Visit Keysight.com for additional information.
