Changes in the geopolitical landscape of the international community and the growing threat of global terrorism have created a surge in the need for personal security, as can be seen from a set of data. According to a report published by Global Industry Analyst, Inc., the full-body scanner market is expected to grow to $1.7 billion by 2021 at a CAGR of 41.5%. According to another report by MarketsandMarkets, the airport body scanning market alone is expected to be worth $118 million by 2021, growing at a CAGR of 8.4%. This does not take into account the huge growth opportunities in non-airport and commercial markets.
From Magnet Gate to Millimeter Wave, the Development of Body Scanners
In fact, security has attracted people’s attention as early as 2,000 years ago. During the Qin Shihuang period, there was a “magnet gate” for the passage of “four barbarians”. The characteristics of magnets and metals were used to prevent foreigners from secretly carrying weapons when paying tribute. This method is still used today, so the metal detector came out. Later, over time, it was discovered that just detecting metal does not guarantee safety. In 2002, a passenger plane crashed in the waters of Dalian, and no one was spared. The reason was that someone was carrying a flammable liquid! Since then, X-ray technology has appeared in people’s field of vision. X-ray scanners are fast and can penetrate living bodies to provide ultra-high-resolution images of the human body and hidden objects, with organic-inorganic mixtures displayed in different colors. However, its drawbacks are also obvious. Due to its inherent penetrating characteristics, the scanned personnel will be exposed to high-intensity radiation and will invade their privacy, which has caused public outrage. Then the X-ray backscattering solution came on stage, which was much better from a health point of view, it didn’t penetrate the target, it just reflected off the target surface. But the shadows brought by X-rays are too thick, causing people to still worry about them. But there is no better choice, and backscattering technology is widely used around the world.
Today, with the advancement of radio frequency, microwave and millimeter wave technology, scanning equipment companies have successfully used this technology to develop a new generation of body scanners that are fast, high-resolution, non-intrusive and do not carry any radiation—— The operating frequency of millimeter wave body scanner is generally between 10GHz and 40GHz, and sometimes as high as 60GHz to 80GHz. Compared to previous scanners, its price is getting lower and lower, the volume is getting smaller and smaller, and the scanning time is fast enough without causing congestion. Gradually, mmWave scanning is the technology of choice for body scanners today and in the future. In this regard, ADI, the industry-leading solution provider, planned the layout in advance and provided a complete signal chain solution from bits to antennas and from antennas to bits for millimeter wave body scanners.
Overcome the traditional “disadvantages” and simplify the plan better
Most scanners on the market today operate over a wide frequency range, and in order for them to have higher image resolution and faster performance, while improving functionality, they require a filter that can filter across the entire frequency range device. But a single wideband filter is difficult to construct, or expensive to implement. Therefore, manufacturers consider using a filter bank, combining multiple narrowband filters through switches, which form a switch matrix to receive the transmit signal and distribute it among multiple transmit antenna elements.
Traditionally, such switch matrices have been achieved by using PIN diodes and GaAs switches in SPDT configurations, especially at high frequencies up to 40GHz. For PIN diodes, each switch requires a large number of external components to control high bias voltages and currents. Likewise, designs using GaAs counterparts require multiple switches to build switch trees for high channel counts. These circuits become more complex as the number of channels increases.
In response, ADI has simplified this design with the ADRF5046, a 40 GHz SP4T SOI (silicon-on-insulator) switch, a silicon-fabricated reflective single-pole, four-throw (SP4T) switch that operates from 100 MHz to 44 GHz with less than 3.0 dB insertion loss and greater than 31 dB isolation. Whether it’s a pass-through or hot-switching, and features 27 dBm of radio frequency (RF) input power handling. With the SP4T, designers can use up to four switch positions instead of two switch positions per switch.
For example, for a simple 12-channel system, 3 SP4T switches can replace up to 7 SPDT switches. For systems with higher channel counts, the benefits of SP4T SOI switches become more pronounced as system complexity increases exponentially. In addition to reducing the number of switching ICs, reducing the number of external components and reducing bias power are equally important. Because the ADRF5046 is designed in an SOI process, it can operate with negligible bias currents at low supply voltages and can access standard CMOS control signals without any external components.
Differences between switching implementations of older PIN diodes and newer SOI switches.
Not only the switch matrix on the transmitter side, but also on the receiver side ADI has introduced a new solution, in which the ADRF5730 using SOI process is used to implement gain adjustment, which is a 6-bit digital attenuator that provides 31.5 dB in 0.5 dB steps. Attenuation control range. To meet fast switching settling requirements, the received signal is then subjected to down-conversion and further amplification stages. As well as the passive wideband I/Q MMIC mixer HMC8192, integrators can downconvert frequencies up to 42GHz to low IF or baseband in one step. This mixer uses the same frequency source block for the LO driver and transmitter stage. The IF of the wideband I/Q mixer is then fed to a single-ended-to-differential amplifier, which is then connected to a high-speed ADC. This high-speed ADC digitizes the signal and provides digital input to a computer that runs a variety of software algorithms to detect the image. Traditionally, however, system integrators mostly use superheterodyne structures to down-convert high-frequency signals to intermediate frequencies in multiple stages.
This article concludes:
It’s not hard to see that providing a complete bit-to-antenna and antenna-to-bit signal chain solution for mmWave body scanners requires the necessary product family, experience, and technical support, and ADI provides solutions that eliminate the need for a separate Selecting, evaluating, and negotiating prices for each device can save a lot of time, money, and effort. With ADI’s broad portfolio of RF, microwave and millimeter wave devices, integrators are sure to find the right device to meet their performance and price expectations. Not only that, semiconductor companies represented by ADI are going all out to realize the next generation of millimeter wave whole body scanners, and sincerely cooperate with system integrators to jointly develop more accurate, fast and more commercially viable whole body scanning systems. , to build a new ecosystem.