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RF Circuit & Antenna Design

Westwood Rock was founded by engineers who already had RF and high-speed digital experience from working with Radar, maritime radio, broadcast, and consumer applications and had been published in the IEEE MTT-S International Microwave Symposium. They had also taken their designs through EMC testing and CE marking.

Bluetooth

The first Bluetooth devices were launched shortly after Westwood Rock was incorporated.

Evaluation Board for Early Bluetooth Chips

One of our first contracts was to develop an evaluation board for the first Bluetooth chips produced by one of the best-known global semiconductor and electronic equipment manufacturers.

DAB

Britain’s first National commercial DAB multiplex also started around the time that Westwood Rock was founded. The take up of DAB equipment was slow and one of its target markets – automotive had long product lives of over a decade. Revo now an award-winning DAB and internet radio manufacturer identified a market for retrofit DAB radios for cars. Having worked with Digital Audio and radio in many applications including TV and Radio production and postproduction equipment, radar and communications; our engineers were well placed to develop DAB radios.

DAB Radio

This was the first DAB radio to be launched by REVO. Designed to be retrofitted to cars, the radio itself was removable and was a comfortable pocket size to be carried between cars. Although wiring harnesses were available to connect audio accessories to many cars they were problematic, often with expensive installation costs. At the time, the low power FM transmitters used for this purpose today were still unlicensed so along with an internal DAB aerial, we proposed and designed an active, FM modulator and low noise RF isolator. This allowed the signal from the DAB radio to be received as an extra station along with those received from the existing FM aerial.

Launched in the early years of DAB it won numerous awards and was very well received by both the audio and automotive press.

RFID and NFC

Whether your application is for security, inventory control, access control, tracking individuals, equipment, or containers we can help you select and implement the correct RFID solution.

RFID

RFID uses weak radio or magnetic fields to communicate between a (usually) passive tag and a reader or writer. The tag can harvest power from the field emitted by the interrogating reader, read any interrogating message and/or respond by emitting its own weak radio or magnetic field. The RFID fields are localised which is usually desirable for example security tags detected when leaving a shop or stock control tags that can be “scanned” despite being on a shelf with numerous others.

There are numerous RFID frequency bands from around 100khz up to Gigahertz each having different trade-offs between size, cost, range, spatial discrimination etc. We can help you select the right technology for your application.

NFC

NFC is a more sophisticated form of RFID where typically a mobile device can act as a reader (for reading a Wi-Fi code or internet URL from a tag on a product) or as a tag itself being read (for example passing contact details) to another device. The main advantage of NFC is that like RFID it is more localised than technologies like Bluetooth improving security and giving better discrimination from nearby devices.

RFID in Retail

We were engaged to develop the electronics for a retail display incorporating a responsive tablet to augment the display for a leading designer brand. Their prototype RFID reader and display functioned but did not have enough discrimination for the readers and RFID tagged products to be as close together as the client wanted. There were two challenges, reading one tag in the vicinity of others and ensuring that a reader at an empty position did not read the tag on a product in an adjacent position. Simply making the readers field weaker increased discrimination but reduced the reliability of reading. We developed the electronics and embedded software and devised a method of controlling the magnetic field using ferrite materials which directed the field rather weakening it.

DECT

Equipment conforming to the Digital Enhanced Cordless Telecommunications standard can be used without operator licenses throughout most of the world although the number of channels and their frequencies vary. DECT was intended to take over from the previous analogue cordless phone standard but is more flexible with a more powerful feature set (depending on the chipset and firmware used) and has much wider application.

Drive Thru Intercom

We were engaged to develop the electronics, software, VHDL and RF for a DECT based intercom system to be used in drive through restaurants. The system provided improved audio quality and more robust radio performance than its predecessor. We initially used a mix of our own design of antennae and a commercial PCB mounted part. When the commercial PCB mounted part became obsolete, we devised a replacement that could be retrofitted to the existing PCB.

Global Positioning

We have implemented many radio modules including GPS/ Glonass devices which are radio receiving devices. Combined modules using more than one system e.g., accessing the US, Russian and EU satellites can give increased accuracy compared to a single system, particularly in areas where some of the sky is obscured e.g., in cities.

WIFi

Many products are connected to a local Area Network (LAN) using Wi-Fi. The performance of a Wi-Fi implementation depends on the chipset or module used, the antennae design and efficiency, the use of diversity, the enclosure, power supplies and successful coexistence with other transmitters including those operating in the same band e.g., 2.4Ghz Wi-Fi and Bluetooth. We can help you with Wi-Fi subsystems, Radio Equipment Directive (RED) approvals and EMC approvals, radio system designs or complete product designs.

IoT

We have discussed elsewhere how we have developed award winning IoT systems. IoT does not always need Radio links, but most systems do rely on either Wi-Fi, Bluetooth or sub 1Ghz radio links. These RF links can be simple point to point systems or mesh networks. Selecting the optimum band and technologies such as mesh networks, dynamic transmit powers and low power devices is very important for successful IoT systems.

Radio Heating

Radio frequency heating is often used in industrial applications such as cooking, defrosting drying, sterilising/pasteurisation and other materials processing and plasma generation used in semiconductor processing. Traditionally electrical energy was converted to microwave energy by a vacuum device such as a magnetron – a heavy device made of metal. As solid-state semiconductor RF sources and power amplifiers become more cost effective, other applications and techniques have become practical. These include advanced cooking techniques such as solid state stirring (an alternative to mechanical turntables in microwave ovens), selective localised heating within ovens or lightweight portable devices.

Our RF work has included a working prototype for a solid state, battery powered microwave device.

EMC/EMI/SAR etc

This regulatory subject applies to Radio products, as it does to every other sector. However, susceptibility regulations require equipment to be tested for susceptibility to a wide range of radiated (Radio) frequencies even if it is not itself a radio product and does not rely on radio frequencies for its own functionality. The same applies to emissions regulations which can be broken by unintended emitters. Designing equipment in a way to minimise susceptibility to radio frequencies and resolving any issues found during testing requires at least some rules of thumb but ideally RF expertise.

As well as ensuring that our designs and products meet all the relevant requirements, we have helped a number of clients do the same for their equipment. We have taken clients equipment through testing and completed the documentation on their behalf and we have helped clients who came to us after their equipment failed EMC testing.

Selecting the band

As well as fulfilling a defined requirement specification we are often asked to recommend suitable radio bands for products or systems. Except for one or two notable bands, radio bands are unusual in that they are not standardised across the EU but are the responsibility of individual countries. Similarly, there is little convergence between frequency allocations in the EU and USA. There is a lot of legacy equipment in use and the spectrum released by obsoleting technology (e.g., analogue TV) means they are quickly re-allocated to high value applications such as mobile communications. This makes it unlikely that the frequency allocations in the various counties of the world will become unified in the foreseeable future. This means that we often have to advise on the trade-offs between using a band that is available worldwide, but which may be overcrowded or may not provide the desirable range or bandwidth and other bands that may require multi-band antennae and circuitry or region specific product variants.

Antennae Design and Test

We have designed and tested many antennae either integrated into our radio designs or for use with them. These have included printed antennae on PCBs, wire antennae, whip antennae and windscreen mounted antennae in a wide variety of frequency bands. We have also implemented many designs using numerous commercial antennae which are often very well characterised by their manufacturers but in most applications their performance is influenced heavily by adjacent PCBs, screen cans, enclosures etc.

Our RF development facility includes a range of RF test equipment (Vector Network Analyser, spectrum analyser, high speed RF oscilloscope, calibration references etc) and we hire equipment that we use less often (usually higher frequency versions of the kit that we own).