Feature: RF design
remote robotic surgery. Yet, without resolving the issue of working at mmWave and THz frequencies (0.1-3THz), 6G could greatly be delayed. Currently there is a shortage of
components, testbeds and even concepts to operate communications systems at higher frequencies (in excess of 100GHz), and there are even fewer devices that work in the THz range, where 6G is expected to work best. Thus, the industry must come up with better components now, to be able to handle 6G requirements by 2030. Creating components at frequencies
above 100GHz is down to physics: Moving up the spectrum means wavelengths are getting shorter; at 300GHz the wavelength is just 1mm. At such high frequencies, the constituent parts are miniscule, which means that even a small alignment error can significantly degrade performance. Then there are the power-handling
problems at such a small scale. The components at these frequencies must operate with exceptionally low insertion loss and extremely high performance, to allow the development of effective signal chains. In addition, high isolation between active components becomes of critical importance to minimise signal degradation and potential device destruction from signal reflections between components. For example, Faraday rotation isolators – more commonly referred to as just “isolators” – are two-port components that allow signals to pass in one direction but absorb them in the opposite direction; see Figures 1 and 2. Since they do a good job of
suppressing standing waves, isolators are often used in communication systems. They have low insertion loss within the microwave bands, but at mmWave frequencies the loss becomes increasingly problematic.
A boost for mmWave components Recently, NASA awarded a project to Micro Harmonics to develop mmWave isolators, handling frequencies to
Figure 1: MHC isolator core
300GHz. Micro Harmonics successfully developed an advanced line of commercial isolators, off-the-shelf and hybrid circulators, many of which operate well into the THz bands. We at the University of Lille selected
one of their isolators that operates with WR-3.4 (220-325GHz) and features a large usable bandwidth of dozens of GHz either side of its centre frequency. T is allowed us to derive the fi rst-ever device characterisation of a low-noise amplifi er operating at 300GHz; see Figure 3 for the experimental setup. Our team successfully characterised
the amplifi er’s noise fl oor, along with its IP3 and IP5 – the measurements of nonlinear frequency performance.
However, in addition to isolators, there’s
also a need for circulators at these very high frequencies. T ese devices are part of the core system for communication applications and radar, and having them readily available will be a big boost for the implementation of early prototypes. For example, a recently-developed hybrid circulator operates in the 100GHz+ range, which will be crucial to solving many of the 6G bottlenecks within network backhaul. T e hybrid circulator has a much larger working bandwidth, from 150-190GHz. T e current state-of-the-art Y-junction circulator has a bandwidth of only a few GHz at these frequencies. Bandwidths required for 6G are not remotely possible using a Y-junction
Figure 2: Isolator sample set
www.electronicsworld.co.uk November 2022 25
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
