On the revolution in radars, deadlines and entering the fourth dimension

In the articles of my colleagues about unmanned trams and diesel locomotivesradars were mentioned. They are widely used in the automotive industry to implement standard active and passive safety features. Solutions for highly automated control systems (including unmanned vehicles) require more flexible and advanced technologies. At Cognitive Pilot, a special unit is engaged in radars, which until the end of 2019 worked as Design House, producing solutions for automakers and component suppliers under the contract model. Now we are moving to a new business model and are preparing a mass production line of radars for a wide range of customers - from DIY projects to start-ups and pilot parks. On the basis of the solutions used in Cognitive Pilot projects, finished products for users will be created, which can be divided into 3 categories: “MiniRadar”, “Industrial” and “Imaging 4D”.Such devices are actively used in a variety of industries, so it’s worth telling more about them.

Exit to the fourth dimension

Usually car radars cannot determine the height of an object, although in industry they use the 3D designation, which the uninitiated may seem like a marketing ploy. Due to the physical properties of the signal (Doppler effect), they measure 3 parameters [R, Az, V]: distance and angle (azimuth) to the object, as well as speed and its sign (the object moves away or approaches the emitter). A typical set of sensors for a self-driving car includes video cameras, as well as radars operating in a long range in any weather in active safety systems and capable of making accurate measurements of a three-dimensional lidar scene. The latter is not cheap (say, Uber installs devices for the price of ~ $ 120,000), but is needed only to obtain a three-dimensional cloud of points and does not allow you to abandon other sensors. 

We thought about releasing a radar capable of replacing an expensive lidar: skipping the intermediate stages of analysis, calculation and evaluation, I’ll say right away that it was completely possible to make it. In the summer of 2017, the first working proof-of-concept layout was created with an external antenna system on waveguide paths. It was necessary to produce it for our frequencies (up to 77 GHz) on precision equipment - for serial models this design was not suitable because of the bulkiness and high cost, but the purpose of the first samples is usually to verify the concept. In addition, the radar was built on not the most perfect element base with the active use of analog solutions. At the same time, it did not contain moving parts and was based on the architecture of a digital lattice and digital chart formation - this is how radars work in fighters. The main thing,that the layout made it possible to prove the fundamental possibility of product sales.


 

Then, by CES 2018, we decided to make the world's first industrial version of the 4D radar with a planar antenna system (we will talk about it below), capable of measuring range, azimuth, elevation and speed [R, Az, Ev, V]. To be in time for the start of the event, it was necessary to completely redesign the microwave part in a short time. The partners became the problem: it took a month and a half to produce a board from special microwave material for our project, and it took several iterations to get a working version. We had to refuse the services of foreign contractors, and in Russia factories do not work with such material. For an industrial design (but also of a proof-of-concept level in terms of printed circuit board material), we decided to choose a close and understandable partner - the Tomsk company NIIPP JSC.All iterations for the manufacture of the antenna on the LTCC low-temperature ceramic production line took about a month, for which I would like to say a special thank you personally to Evgeny Alexandrovich Monastyrev. 

As a result, we got the thinnest ceramic plate of a large area, on which a planar antenna was bred. It was required to be glued into the radar case, fixed on a titanium (because of KTR titanium and ceramics, so that the board would not break during temperature changes) base: since the deadlines were burning, I had to carry it by plane from Moscow in my luggage. Then we needed to collect the radar, have time to test it and make a demo by January 4. 


Crunch ... as they say, broke the "plate" for happiness. a piece of the same ceramic board

A photograph under the microscope of the pairing of a ceramic antenna and a board with microchips of a transceiver made using gold wires with a thickness of hair

The bearing capacity of the ceramic board is low, so it must be glued to a rigid base. A special press was used for this operation - the NIIPP specialists also dealt with this. The most dramatic moment came on December 27 - 28, when a product made in a single copy burst during the assembly process. Colleagues from Tomsk entered our position: shouting “we don’t give up our friends” and “ours in Las Vegas”, the guys launched the production line and worked on December 30 and 31, so that by January 1 we would get the assembled system. For 2 days, we completely installed, configured and debugged the hardware, and by January 4 we made a demo showing its work. Of course, later on we used the same imported material with the necessary radio frequency properties,but at the end of 2017, only a domestic company was able to produce a suitable prototype on time. 


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« CES»

We needed to create relatively inexpensive compact devices without moving parts, so that small startups and even home-made people could afford them. Since the laws of physics cannot be deceived, the development of the microwave part has become a serious problem: to obtain a high angular resolution, a full-fledged phased antenna array was required. In all radars we install planar (microstrip) antenna systems implemented in the form of tracks of a special shape on the boards. Due to the high radio frequencies (up to 81 GHz), the textolite used in conventional electronics is not suitable for their manufacture - special material is needed to ensure a low level of signal attenuation per linear centimeter. 

Another problem is related to the electronic filling of the device, which should be compact, but quite functional. Radars process information on board, and not just give out some kind of analog signal - at the output the user needs to get the coordinates of objects, as well as the direction and speed of their movement. In recent decades, microelectronics has made great strides, and now highly integrated systems are available on the market that allow you to implement many of the necessary functions. The latest generation models allow you to make a radar on a single chip, though it will be a relatively simple device. The chip has an analog part, including blocks of receivers and transmitters, ADCs, as well as hardware accelerators, which make, in particular, fast Fourier transform. The digital unit has a DSP (Digital Signal Processing) processor and an ARM processor.The level of information processing is consistent with the capabilities of the sensor itself: in radars with a small number of channels and the lowest resolution in the angle, chips corresponding to their needs are installed. 



All Cognitive Pilot radar sensors operate according to the MIMO principle (Multiple Input Multiple Output; multiple inputs, multiple outputs - a method of spatial signal coding, which allows to increase the channel bandwidth). The blocks of receivers and transmitters are geometrically separated, while the transmitters can emit a signal in turn (time division of channels) or in the form of different code sequences (code division of channels), as well as combining these approaches. In this way, you can improve the characteristics of the radar without complicating and increasing the cost of the structure. The main plus here is the reduction in the required number of receiving channels. In our smallest radars, for example, 3 transmitters and 4 receivers. The transmitters simultaneously emit different code sequences, something similar is done in the 3G and CDMA standards.Four physical receivers separately receive them and collect the signal from each transmitter - as a result, 12 virtual receive channels are obtained, as a result of which the resolution is tripled without modification of the physical design. Otherwise, to achieve a similar result, 8 more receiving paths, lines and additional ADCs would be required, which would complicate the design and increase the cost of the radar by multiple.

We do the entire development stack ourselves: we design part of the microwave, electronic stuffing and other hardware components, as well as create the design of the device. Iron is a very important, but only an integral part of the radar. How it works and what data can be pulled out of it depends on the algorithms: object detection, secondary processing filters, code sequences - all of this we also design ourselves. The whole algorithm of the mathematical model, starting from the formation of signals. To do this, in the single-chip solution, on which the Cognitive Pilot Mini series radars are based, quite sophisticated firmware is embedded. It can distinguish various subsystems, for example, to control analog peripherals or hardware accelerators. The solution is flexibly configured, allowing you to optimize data flows and their movement between different blocks. 

The lineup

Mini series radars are ready-made single-board solutions that can be connected via the CAN or SPI connector (depending on version), say, to the on-board computer of the car and even to the Arduino microcontroller, which is popular with home-made manufacturers. Other series are similar to them in terms of antenna systems (the horizontal viewing angle for all models ranges from 120 ° to 150 °), but these are already more complex solutions from several modules (microwave, digital processing, power and interfaces). They have significantly more channels, and therefore much higher angular resolution: in Industrial models, for example, there are already 32 receivers, which requires serious computing power.In addition to the main analog-digital board with a set of transceivers and an antenna system, you have to install additional digital processing units (boards) with a rather powerful DSP processor and Ethernet adapter with power supply via a network cable. 



Imaging 4D radar with a horizontal viewing angle of 120 ° - 150 ° still pumps the beam in a vertical plane. Knowing at what moment the reflected signal appears and disappears, you can take the bearing, understand the vertical angle of the beam directed at the object and determine the third coordinate of the point. The production version of the first generation 4D radar was licensed with several of our customers. Since then, we have moved forward and are now preparing a new solution with more advanced technologies than used in 2017. Which, by the way, will not have contractual restrictions, and therefore will become available to a wide range of users.


Photo of the current Imaging 4D model

Devices of various series are distinguished by functionality, as well as the quality of the results. Mini series is designed for the implementation of emergency braking systems, adaptive cruise control or blind spot monitoring in cars. Industrial sensors can be used in automated industrial complexes, in monitoring systems or, say, in diesel locomotives, and advanced Imaging 4D solutions are designed for self-driving vehicles.

Future plans

Since the beginning of 2020, we have been trying to make Cognitive Pilot radar technologies available to the mass customer. There is quite a lot of progress: a synthesized aperture for ultra-high resolution images, estimation of object signatures based on micro-Doppler perturbations, super-resolution, localization based on radar data.


High resolution - this is how the radar sees parked cars in aperture synthesis mode.

We create solutions in different technical and price segments so that users can choose the best for their projects. In general, there are many plans, there are even more cool tasks (we don’t miss R&D), so in the following articles we will tell readers in more detail about the technologies we use.