Plextek Powers mmWave beam steering for 5G radio

CEO Liam Devlin

Plextek RFI has developed a compact 4-channel power amplifier design with beam steering control that it believes will address a key element of developing viable wireless access services at higher transmission frequencies.

The UK design house presented details of the ‘4-Channel 26GHz Power Amplifier with 4-Bit Digital Phase Control for 5G RF Front Ends’ at the ‘5G Radio Technology Seminar’ on March 17. It offers a means of providing beam steering to enable the move to higher transmission frequencies – proposed by some for 5G – where wider bandwidths are readily available.

“This IC facilitates that by splitting a modulated RF carrier signal into 4 identical copies, which are each amplified by separate Power Amplifiers (PAs) to boost the transmitted output power level”

‘In order to allow the effective implementation of cellular communications devices at mm-wave frequencies, one of the techniques currently being researched for 5G systems is to implement electronic beam steering  to change the direction in which the peak power of the transmitted signal is radiated’, said Liam Devlin, CEO of Plextek.

‘This IC facilitates that by splitting a modulated RF carrier signal into 4 identical copies, which are each amplified by separate Power Amplifiers (PAs) to boost the transmitted output power level. The insertion phase through each of the 4 channels can also be independently adjusted using an integral 4-bit phase shifter, thus steering the beam.’

“we need a beam that is less directional and a solution that is less expensive”

Beam steering is not a new concept. It has been around for many years with its most renowned application being in electronically steerable phased array antennas for radar and satellite communication applications. But these are usually large, expensive arrays of 100s or 1000s of individually controllable elements.

‘For cellular communications we need a beam that is less directional and a solution that is less expensive,’ said Devlin. ‘This IC can be used in both the handset (consumer device) and at the base station. It can be used as a simple 4-element array or multiple devices can be included to implement a larger array – for example, 4 parts could be used in parallel to realise a 16-element array.’

Taking its first step in 5G development, Plextek has included 4 parallel PAs at 28GHz on a single die, something which hasn’t been seen before . The integral phase shifter within the PA, together with its suitability for TTL control, is not something being offered in current commercially available mm-wave ICs.

“We expect that there will be a gradual ramp-up of demonstrator 5G radios and systems over the coming years”

‘This is our way of demonstrating what we can offer to developers of 5G components and systems,’ added Devlin. ‘We expect that there will be a gradual ramp-up of demonstrator 5G radios and systems over the coming years, but that the volume deployment will not start to commence until 2020.’

Plextek is hoping to attract the interest of suppliers of microwave components for commercial applications and for companies developing trial 5G systems.

One of the key hurdles to using mmWaves for 5G wireless access will be dealing with the mobility of users connected to base stations. Current mmWave links (for backhaul, for instance) tend to be formed of line of sight links between two aligned nodes. That will, of course, not be the case with cellular users, who will a) be sited at many locations within a cell and b) move around within that cell. One proposed method to deal with this has been the development of devices with phased antenna arrays (smart antennas). Doing this will require the integration of a large number of small radiating elements onto devices as well as base stations – something researchers are actively addressing.

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