Operation in the millimetre-wave (mm-wave) bands offers you capabilities in a compact form that are not possible at lower frequencies. With over 30 years of experience in complex RF and antenna design, Plextek has dominated the mm-wave technology market from addressing challenges in autonomous vehicles, to object detection and security systems. Solutions have included both research projects through to product development, covering radar sensors, communication systems and monitoring capabilities.
New, emerging technologies have opened up the world of millimetre-waves to more cost-sensitive applications.
- Integrated mm-wave antenna and array design: The antenna is an important—but often overlooked—component in most RF systems; for systems operating in the mm-wave bands, this is especially so. Achieving wideband performance for low-profile designs as well as high efficiency is particularly challenging. Our experience has shown that designing a mm-wave system around the antenna solution and integrating with the circuit design directly (removing lossy and expensive interconnects), whilst challenging, is often the most effective way to achieve the best overall system performance.
- mm-Wave module design: Often large systems require separate, high-performance modules to carry out a dedicated task. At Plextek we have experience designing mm-wave modules using both packaged and unpackaged components, such as die-based transceiver designs, to achieve the desired performance.
- mm-Wave frequency synthesiser design: To operate in the mm-wave bands, it is necessary to generate a mm-wave signal. Frequency synthesisers are the basis for most RF systems, so performance is critical. Depending on application, different requirements need to be prioritised. These could be: low phase noise, wide tuning range, low harmonic and spurious products, precise frequency accuracy, fast settling time and frequency synthesis with direct modulation.
- mm-Wave PCB design: We have carried out a number of different PCB designs using a variety of substrates, builds and finishes operating at mm-wave frequencies for cost-effective and high-performance solutions alike. We have pushed the boundaries of PCB technology to extract the best possible performance, reliability and cost reduction for our clients.
- Printed mm-wave components: PCB technology has given us the ability to etch features directly out of copper for a low-cost implementation of passive components, such as printed filters, directional couplers, power splitters, baluns or impedance transformers etc. Whilst circuit simulation provides a reasonably accurate prediction into operation of such components at lower frequencies, 3D electro-magnetic simulation is vital at mm-wave frequencies. At Plextek, we have access to different electro-magnetic simulation tools, which allow us to select the most appropriate tool for the job.
- Cost-sensitive solutions: Often our customers require highly cost-sensitive mm-wave radar devices without compromising on performance. For these applications we often use an inexpensive, highly integrated single chip mm-wave radar sensor with embedded processing from Texas Instruments. Combining this chip with an optimized antenna solution produces devices which are more cost-effective with low power consumption. Further info can be found in our ‘Downloads’ section.
“Working at millimetre wave frequencies is particularly challenging, not only to achieve good performance but to even get the system to function at all. As a result, mm-wave systems can be very unforgiving, so it is even more important to carefully consider each aspect of a design. However, the benefits of working at this frequency make this extra effort all the more worthwhile”
mm-Wave Radar System
Plextek has been working at mm-wave frequencies (above 30 GHz) for some years now. At these extremely high frequencies (EHF), systems often require highly directional antennas that have narrow beamwidths and can be manufactured in a cost-effective manner.
In this project, the antenna forms part of a radar system operating at 60 GHz and the design was taken from initial concept through detailed system performance and design calculations to an integrated, highly manufacturable, single-board radar sensor in just a few months.
The novel antenna for the mm-wave radar incorporates Substrate Integrated Waveguide (SIW) technology within a multi-layer, low-loss, microwave laminate. This method involves using the PCB itself to create an enclosed transmission line that can be implemented on the same microwave laminate as the radar transceiver circuitry, thereby yielding a compact design that makes best use of the PCB area.
A corporate-feed network connects the radar transceiver to a multi-element slot array antenna comprising of 32 x 16 slot elements. The aperture is weighted to reduce sidelobe levels, an essential requirement for radar systems. The resulting antenna pattern exhibits a sharp ‘pencil beam’ with high gain and nominal half-power beamwidths of 4° by 9°.
The complete radar system requires minimal assembly because both transmit and receive antennas are inherently aligned. Trials of the micro-radar system have demonstrated the ability to detect relevant targets at distances up to 100m. Ultimately, a uniquely capable radar sensor having low size, weight and power (SWaP) has been realised.
Micro Radar Development
Our major strength is the ability to bring together specialist expertise across many disciplines to engineer something very special. Plextek’s current micro-radar project is an excellent example of this. The project was funded through Autonomous Systems Underpinning Research (ASUR), with the aim of investigating how radar might be applied to the problem of collision avoidance in small-sized UAVs. In just a few months, our engineers have taken the initial concept through detailed system performance and design calculations, to an integrated, highly manufacturable single-board radar sensor head, suitable for use in airborne trials.
Given the application, it was apparent from the outset that size, weight and power would all need to be ruthlessly minimised. In order to facilitate navigation through closely spaced obstacles, the sensor must achieve high angular resolution – to only a few degrees. To achieve this from an antenna only centimetres across dictated the use of millimetre-wave frequencies. Initial systems engineering calculations concentrated on selecting a waveform that would maximise the detection performance achievable with only milliwatts of transmitted power, aiming for compatibility with an emerging generation of highly integrated commercial millimetre-wave ICs.
Having identified candidate active devices, the next problem to solve was that of the antenna. Although radar antenna gain requirements may be similar to those of demanding communications applications, radar applications typically also mandate that very narrow beamwidths and ultra-low sidelobe levels are achieved across very wide bandwidths. In this particular case, size and weight must also be kept to a minimum. Plextek’s antenna engineers evolved a novel printed design, which was verified and refined using advanced EM simulation software tools.
Through the creative use of state-of-the-art PCB design and manufacturing techniques, it proved possible to integrate the transceiver circuitry and antenna onto the same PCB, not only minimising size and weight, but also eliminating the need for bulky waveguide or lossy coaxial cable interconnects. 3D printing was employed to realise supporting mechanical components. Throughout the design process, input from Plextek’s manufacturing engineers ensured that this advanced design would be readily manufacturable.
Plextek’s signal processing expertise was brought to bear in providing real-time display of the sensor output, along with raw data logging to facilitate refinement of detection algorithms off-line. Code has been designed to be compatible with a variety of platforms, with a view to enabling the efficient use of pre-existing processing resource, if required.
Trials of the complete radar have demonstrated the ability to detect relevant obstacles at up to 100 metres with an update rate of several Hertz, in a lightweight low-SWaP package. The successful outcome of the micro radar development highlights the benefits of bringing together systems design, millimetre-wave engineering, antenna design and EM simulation, mechanical design and digital signal processing skills in the realisation of a uniquely capable low-SWaP sensor. Future work will concentrate on further development of algorithms for UAV collision avoidance as well as for ground vehicle and static applications, and also the analysis of target micro-Doppler.
Demonstrations have strayed beyond the originally intended application, with one particular favourite being a real-time, high update rate display of a game of catch with a golf ball!
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