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Enhance M2M devices through antenna optimization

Posted: 06 Jun 2012 ?? ?Print Version ?Bookmark and Share

Keywords:radio frequency? machine-to-machine? over the air?

Choosing the right cellular antennas for a device, testing, and integrating them properly can mean the difference between passing and failing network certification tests such as PCS-1900 Type Certification Review Board (PTCRB). Good radio frequency (RF) optimization and over the air (OTA) performance in wireless devices is critical for these certifications, and incorrect antenna selection and integration can often be blamed when M2M devices fail certification testing. Often, it is a system issue, such as the overall design of the system or how that device is interacting. As with many things, system optimization is the key to success.

This article discusses the important process of antenna selection, how to incorporate antennas in machine-to-machine (M2M) devices and the recipe for connectivity success. First, let's take a look at selecting the proper antenna.

Antenna selection
Better antennas mean better devices. It's as simple as that. Understanding the requirements for achieving specific network certification processes are the most important factors when first selecting a cellular antenna. Once the module provider and the carrier have been selected, the next part of the process should be selecting the right antenna for your application.

The first step is for the device maker and antenna company to partner from the start to incorporate their ideas for compliance and RF performance.

The second phase involves the device maker and antenna company cooperating on product design files to work out the advantages and disadvantages of each antenna configuration.

Once the antenna is selected, the customer can start to make prototypes of the device incorporating the required configuration for the recommended antenna. Depending on whether it is a custom design or not, the antenna partner either provides the device maker with a current production sample (off the shelf) or a handmade antenna for the prototype device that enables the device maker to finish their product design. When the product is finished and can connect to a network, the device maker sends the final device to the antenna partner.

Next is the stage where active device optimization happens C this means the ability to increase the device send and receive sensitivity to improve transmissions. When devices are optimized it results in superior M2M devices. The process is what cellphone companies do in their own laboratories before sending devices to final certification. M2M companies in most cases do not have the resources to do that on their own, and they are required to choose antenna partners who can do it for them.

Selecting the right antenna can streamline the whole product design process and result in M2M devices passing certification testing the first time. In general, M2M systems are getting smaller to satisfy scenarios such as body-worn medical devices. Yet, the same device has to get excellent performance and will be compared to a cellphone. When devices are smaller, performance can be compromised, but using an antenna optimized for greater send and receive sensitivity can help compensate for size.

Antenna selection and integration will affect over-the-air (OTA) measurements and can affect radiated spurious emission (RSE) figures. Without high antenna efficiency, certain network OTA requirements, particularly total radiated power (TRP) will not be met. RSE is a common point of failure for M2M devices seeking PTCRB certification. This can be misinterpreted as an antenna issue. Here's what can happen:

1. RSE failure can be caused by an antenna impedance mismatch with the module when the device is on and transmitting. The solution is to design the antenna for an active device, not just a passive device. There must be a good impedance match when the device is on and transmitting and when connected to the network / base station simulator.

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