The right path — A look at path loss calculations for modules using the 2.4 GHz band

January 02, 2015 // By Pradeep Shamanna, Microchip
The 2.4 GHz band has become a popular choice for short-range radio applications in homes, offices and factories. Usually, 2.4 GHz channels are part of unlicensed Industrial Scientific Medical (ISM) frequency bands. Many protocols such as ZigBee (IEEE 802.15.4), Bluetooth (IEEE 802.15.1), Wi-Fi (IEEE 802.11 b/g/n), Wireless Universal Serial Bus (WUSB), proprietary protocols (such as MiWi) and few cordless phones occupy this space. However, operation in the 2.4 GHz ISM band induces the radios to interfere with other protocols using the same spectrum.

It is important therefore to evaluate the range and performance of wireless transmission to create models for estimating the path loss for short range modules in indoor and outdoor environments to give designers an initial estimate on a wireless communications system’s performance. The performance parameters include range, path loss, receiver sensitivity, bit error rate (BER) and packet error rate (PER), which are critical in any communications system.

To do this, consider three modules with varied specifications related to power and type of antenna – Microchip’s MRF24J40MA, MRF24J40MB and MRF24J40MC. The MRF24J40MA is a certified 2.4 GHz IEEE 802.15.4 radio transceiver module with integrated PCB antenna and is suitable for wireless sensor networks, home automation, building automation and consumer applications. The MRF24J40MB is similar but better suited to longer range applications such as automatic meter reading. The MRF24J40MC has an external antenna (shown in Figure 1) and also suits longer range applications. All three connect to microcontrollers through a four-wired SPI interface and have various regulatory and modularly certified on board.

Figure 1: MRF24J40MC modules with daughter board and external antenna.

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