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There is a perception that using a wireless module can help get a product to market quickly and ease the qualification process, but it comes at a price of a larger size.
Modern materials and design can now help the miniaturization of wireless systems, optimizing the antenna designs and matching the radio elements. Even though there can be a penalty on the additional size, using a module can help by isolating the noise sensitive elements of the design, improving the overall performance of the system. In the end this can lead to a smaller design as it eliminates the need for isolation of the radio front end, which can take up space or require more layers on a printed circuit board to provide the isolation. While making the design smaller, this can be significantly more costly.
In some cases using a module may not incur a size penalty. In fact, integrating key components into the substrate of the module itself can reduce the footprint, providing even more benefits in the miniaturization of a wireless system.
For some applications, such as smartcards, modules are essential, but even here there is innovation in miniaturization. For example, Infineon Technologies has developed a “Coil on Module” (CoM) package technology that it believes could revolutionize the design and manufacture of dual-interface wireless smartcards.
The technology simplifies and improves manufacturing of electronic identification cards (eID), electronic drivers’ licenses or health insurance cards with a contactless interface. These Dual-Interface cards build a bridge between contact-based card applications primarily used today and the emerging wireless mobile solutions. According to the latest estimates of market research firm IHS, the number of Dual-Interface cards for government and healthcare will grow between 2013 and 2019 by twenty-two percent per year compared to an increase of fourteen percent for purely contactless cards.
Figure 1: Infineon has used a coil antenna on a RF chip module to link to an antenna on a smartcard.
The key to the design is an RF link rather than the common mechanical-electrical connection between chip module and card antenna, electrically coupling the module to the card (see Figure 1). This allows skipping the elaborate process of interconnecting the chip module to the card antenna during card production. As there is no connection between the chip module and the card antenna, which might be damaged through mechanical stress, the card is more robust and also more secure as the chip module is 20% slimmer than common modules, so that additional security features can be integrated in the card. The CoM technology also means the chip and module with integrated antenna are perfectly adjusted and do not require additional tuning by the card manufacturer.
Miniaturization of Bluetooth modules is driving wireless technology into more and more applications where space is at a premium. For a simple Bluetooth serial link, a wireless module can provide an interface in a tiny sixty-ball package that measures just 6.1 mm x 9.1 mm x 1.2 mm. The LMX9830 Bluetooth Serial Port module from Texas Instruments is a highly integrated Bluetooth 2.0 baseband controller and 2.4 GHz radio with all the hardware and firmware needed to provide a complete solution from antenna through the complete lower and upper layers of the Bluetooth stack, up to the application including the Generic Access Profile (GAP), the Service Discovery Application Profile (SDAP), and the Serial Port Profile (SPP).
Figure 2: The sixty-ball package for the LMX9830 Bluetooth serial link module from Texas Instruments.
Not only is it small, but the additional software also reduces the time to market, as the module is pre-qualified as a Bluetooth Integrated Component and includes a configurable service database to fulfill service requests for additional profiles on the host.
The miniaturization comes from a combination of TI's CompactRISC 16-bit processor architecture and Digital Smart Radio technology. The firmware supplied in the on-chip ROM memory provides a complete Bluetooth (v2.0) stack including profiles and command interface, as well as point-to-point and point-to-multipoint link management supporting data rates up to the theoretical maximum over RFComm of 704 kbps with up to seven active Bluetooth data links.
For a more complex module for wireless sensors, industrial, medical and automotive applications, Panasonic’s next-generation, smartphone compatible, place-and- play PAN1322 Bluetooth module integrates a 32-bit microcontroller with Bluetooth 2.1 + EDR stack, serial port profile (SPP), AT command set API and ceramic antenna.
Figure 3: The PAN1322 module from Panasonic includes a ceramic antenna.
This cost-engineered offering is based on a single-chip solution that integrates an ARM7TDMI processor with a Bluetooth controller for secure, reliable, high-speed data connections using Secure Simple Paring (SSP), eliminating manual password creation. Embedded serial port profile (SPP) frees application resources while the AT command set API creates a simple firmware interface using modem commands. The onboard antenna eliminates the 2.4 GHz RF circuit complexity for the designer, all in a 15.6 mm x 8.7 mm x 2.8 mm module that is fully shielded to improve immunity.
There are no external components needed as the module also includes an onboard voltage regulator supporting voltages from 2.7 to 3.6 V, and it supports the industrial temperature range from -40 to +85°C.
Figure 4: Including the antenna and voltage regulator in the PAN1322 eliminates external components.
Perhaps surprisingly, the choice of software architecture can also help with the miniaturization of a wireless module.
For the more complex Bluetooth Low Energy (BLE) and Smart protocol, Laird's BL600 module integrates the Nordic Semiconductor nRF51822 chipset with RF to provide low power consumption with long wireless range, all within a compact footprint of 19 mm x 12.5 mm. While the module incorporates all the hardware and firmware required to support development of BLE applications, it is the programming environment that helps reduce the overall size of the wireless node even further.
Laird's event-driven smartBASIC programming language significantly simplifies the BLE integration and allows standalone operation of the module whereby sensors can be attached via any of the interfaces without the need for an external processor, reducing the size of the node. A simple smartBASIC application encapsulates the complete end-to-end process of reading, writing, and processing of sensor data and then using BLE to transfer it to any Bluetooth v4.0 device – smartphone, tablet, gateway, or computer. Ultimately smartBASIC accelerates initial development, creation of prototypes, and mass production by providing BLE expertise within the module.
Figure 5: The Laird BL600 Bluetooth Smart module is smaller than its battery.
There are other ways to drive miniaturization in wireless modules. Using a ceramic substrate may seem to be an expensive approach, but this can allow components such as capacitors, resistors and even inductors into the different layers of the substrate. This allows filters to be included easily in the module, reducing the overall size, as external discrete components are not needed.
Ceramic technology can also help miniaturization of wireless systems in other ways. For cellular systems using MIMO (multiple in, multiple out) topologies to improve performance, the size of the SAW filter is a key consideration. As a result, Kyocera has developed a miniature SAW filter module for diversity, which is suitable for communication terminals that require miniaturization and low profile.
Figure 6: Integrating discrete components into the substrate of the module reduces the size of the SAW filter from Kyocera.
The module measures 2.5 mm x 2.0 mm x 1.1 mm by using a small SAW filter integrated with the matching circuit and diplexer into a ceramic substrate, supported by a proprietary resin molding structure. The filter characteristics with low insertion loss and high attenuation come from the design of matching circuit and diplexer, and the smaller size comes from integrating the external components into a ceramic multilayer substrate. The module is also made more rugged and reliable by coating resin on the substrate where the SAW filters, capacitors or inductors are mounted.
Modules can be used to reduce the time-to-market and qualification time of wireless systems, but with innovative design techniques they are also being used as a key driver of miniaturization. Reducing the size and complexity of a wireless link is pushing the technology into more and more applications. With a simple Bluetooth module in a few square millimeters, designers can easily implement a wireless connection, boosting that to more complex designs with different modules. By integrating the antenna and matching circuitry into the module with optimized silicon controllers and power management, the overall size of the interface can be reduced. Integrating external components into the substrate of the module extends this miniaturization to reduce the size of the design even further.