Although some 5G chips have appeared one after another, it is still unclear what kind of process technology to use to produce power amplifiers (PAs) and phased array antennas. For PAs, participate in the millimeter wave wireless of smart phones: Members of the next 2, 5, 10...' (mmWave Radios in Smartphones: What they will look like in 2, 5, 10 years) panel discussed the so-called 'IV family' processes such as silicon CMOS and Helium, and 'III-V' processes, including indium phosphide (InP), gallium arsenide (GaAs), etc. Group IV refers to the element in row 14 of the Periodic Table, and III- The V family is the element of lines 13 and 15.
Dylan Williams, Electronic Engineer, National Institute of Standards and Technology (NIST), and Amarpal Khanna, National Instruments (NI) Research and Development Engineer, are the moderators of this panel discussion. Williams points out that indium phosphides are at high frequencies. The performance in the mmWave band here exceeds the CMOS PA, while the CMOS wins below 6 GHz. However, Harish Krishnaswamy, associate professor of electrical engineering at Columbia University in the United States, said that compared to the CMOS process, the III-V group was used. The circuit created by the process is more efficient. In addition, Deveraux Palmer, chief technology officer at Lockheed Martin, added that 'the current III-V process cannot be switched at high speeds,' resulting in limited use.
However, Williams asked: 'Is efficiency so important?' The crux lies in the fact that the endurance of a mobile phone must be able to sustain at least one and a half days after each full charge, allowing users to forget to charge their mobile phones even before going to bed at night. Can be used normally or until the morning before charging.
'The frequency above 6GHz needs some technical breakthroughs.' Anthony Fischetti, vice president and chief architect of MACOM, said in a briefing later: 'The III-V process is different from CMOS, and GaAs has too much power below 6GHz.' Fischetti explained How MACOM, his company, responds to these different processes. For example, MACOM is currently working with STMicroelectronics (ST) to use a gallium nitride (GaN) process to manufacture RF components. The process is feasible, but the amount of production required is still not realistic. The equipment needed is not unattainable or extremely expensive. He pointed out that with MACOM's current fabs operating around the clock, about 50,000 CMOS wafers can be manufactured per week. And if you make GaN (III-V) wafers with the equipment available today, the company will probably spend a month to produce the same amount. 'Fabrics that use the III-V process must change in order to Achieve the scale of today's CMOS process. '
Fischetti also pointed out that the III-V process is economically viable and cannot have reworked wafers. Quality must be part of the process. In addition, optical lithography must be used to capture all layers of the image. On the circle. The e-beam lithography technology is too slow. Another problem with the III-V process is that no gold elements can appear in the non-layered rooms. Employees cannot wear gold watches and gold jewelry, etc. .
In addition to the process problems that 5G will bring, there are also test challenges. In this panel discussion, Loy Laskar, chief technology officer of Maja Systems, said that about 80-90% of bill of materials (BOM) costs may come from IC assembly and testing.
Although test ICs and systems for military applications use special processes, mmWave spectrum and phased array antennas, but their number is not large, such tests are quite challenging for consumer devices with a large number of requirements. NI RF Charles Schroeder, vice president of marketing, and Roger Nichols, global 5G project manager at Keysight Technologies, highlighted several 5G testing challenges, the most obvious of which is the need to use over the air (OTA) for testing. Highly integrated components (PA and phased array antenna) mmWave system. But OTA testing does have an impact on production test time, and test equipment must have the ability to handle these workloads.
Schroeder pointed out that dealing with the larger bandwidth signal brought by the mmWave frequency requires huge computing power and a lot of time. At present, test engineers do not know whether they need a PC-class processor, FPGA or GPU to process the signal. Need to rethink some of the ways in which wireless signals are currently handled.
Other problems come from the high-frequency bandwidth. Because the bandwidth is quite wide – it may be 100MHz, the impedance of the transmission path may be different. The test system must know this and compensate accordingly.
Nichols further discussed the testing issues and pointed out the problems of near-field and far-field measurements. 'The far-field OTA test may be considered more difficult than the near-field. However, there is actually a compromise between the two. In the far field, the electromagnetic field performs better. For example, it is closer to the classically defined vertical E-field, H-field, and Poynting vector. It is more difficult to cause far-field testing because of signal loss and the size of the anechoic chamber. In the near-field, the challenge is Get accurate detection of antenna behavior and relationship between signal phase and amplitude. Furthermore, mmWave has a short wavelength. Since the near field to far field (NF/FF) is proportional to the reciprocal of the wavelength, the smaller the wavelength, NF The longer the distance between /FF conversions.'
Nichols pointed out: 'What people do is very random, such as mobile phones. 'This random movement is not a problem, because the antenna design is omnidirectional. However, in order to reduce the power consumption of 5G, phased The beam control of the array antenna will become normal. This will force the test to be performed in different directions. The test system must verify the phone because the phone will constantly track its direction and adjust the beam accordingly. Most importantly, the test must be reduced Certainty. Nichols said: 'You can't be sure how effective it is before you can get a verification number.'
Compilation: Susan Hong