RF Range
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AN014 RF range of IQRF transceivers Typical RF range accessible between a couple of IQRF transceivers with small antennas (e.g. the PCB ones optionally built in the transceivers themselves) in common applications without special optimizing is tens of meters in buildings and hundreds of meters in free space. Special arrangements enable ranges in kilometers. RF range can be extended by two main approaches:   There are several possibilities how to prolong the physical range accessible between a couple of IQRF transceivers. Much higher effective range can be reached in Mesh network. In this...

AN014 Noise test It is possible to create a simple noise detector from any TR transceiver. • Upload the application below into a TR (typically TR-72DA) and plug it into the DK-EVAL-04A kit. #define RX_FILTER 0 void APPLICATION() { while(1) { if (checkRF(RX_FILTER)) pulseLEDR(); } } • Set desired RF band and RF channel in TR configuration. • Place the detector to the location where the noise should be checked, e.g. close to an electronic equipment or a power source. • The noise is indicated by red LED flashing. • Change parameter rx_filter to evaluate the noise level. You should also...

AN014 Hardware Besides of basic RF parameters (such as output power, input sensitivity and bit rate) of the transceiver itself, RF range strongly depends on several design and application aspects. Construction The construction of the device is important in every design, but especially when a TR with built-in PCB meander line antenna (e.g. TR-76DA or TR-72DA) is used. Conductive parts Everyone including beginners knows RF shielding and the fact that the antenna must not be housed in a metallic case. However, there are even other important impacts. All conductive objects (ground planes on...

X – antenna spacing to a conductive plane parallel to TR antenna, in λ units Diagram 2: Parallel arrangement. Transmitting TR-72DA antenna in parallel with the plane 120 mm x 120 mm, receiving TR placed in direction of the blue arrow. Non-conductive parts Even non-conductive parts close to the built-in meander antenna can impact the range due to losses of RF power as well as RF sensitivity. Even a mainboard PCB under the antenna can significantly degrade the range. This impact depends on parameters of given PCB and is significant up to approx. 5 mm around, inversely related to the distance....

AN014 Counterpoise By contrast, utilizing an artificial ground is the right way to increase RF range. A conductive object connected to the ground placed in proper location towards the antenna creates a counterpoise effect improving RF output power as well as RF input sensitivity. This can significantly prolong the range with no side effects and almost no expenses except possible enlarging dimensions. RF signal stays omnidirectional. The counterpoise effect can be tested using the TR-7xDA transceivers plugged in DK-EVAL-04A development kits, either directly or via the RNG-EXT-01 range...

AN014 Antennas Crucial effect on RF range has the antenna type (style, dimensions, directionality, …) at the transmitter as well as the receiver. Mutual orientation of antennas should respect polarization and radiation patterns. All antennas mentioned below have linear polarization. Directional antennas provide ranges up to about 10 km. PCB antennas built in TR transceivers Radiation patterns RF output power specified in TR datasheet relates to isotropic radiation (equal in all three dimensions). However, the PCB antenna built in TR-7xDA transceiver is designed as a shortened ¼ wave whip...

AN014 Arrangement Examples of correct and incorrect arrangement of TR-72DA pairs: Incorrect Wrong radiation angle Incorrect Mismatched polarization Incorrect Wrong radiation angle Mismatched polarization Tip: In a hand-held remote controller, locate your PCB antenna in transverse but not in longitudinal position. External shortened ¼ wave whip antennas Similar characteristics and radiation patterns as for the PCB meander line antennas built in TR-7xDA transceivers are also valid for external IQRF (shortened) ¼ wave whip antennas. Directional antennas Directional antennas in low power...

AN014 Diagram 5 shows radiation patterns of planar directional antenna AN-09 in comparison with small IQRF omnidirectional antennas. E.g., there are only two < 40 º areas where RF range is lower for AN-09 than for the antenna built in TR-7xDA. Units: dBm Diagram 5: Radiation patterns of antenna AN-09, AN-011 and antenna built in TR-7xDA (either with or without range extender RNG-EXT-01 at DK-EVAL-04A). Shaded areas illustrate the only spaces where the range of AN-09 is shorter than at TR-7xDA.

AN014 Environment First Fresnel zone Obstacles may attenuate or destroy RF signal, firstly due to absorptions and reflections. Their influence may be important even if they are out of the signal path line-of-sight. To achieve the longest RF range, the 1st Fresnel zone should be free. It is an ellipsoidal space between and around two transceivers defined according to Diagram 6. TR D P D1 D2 R λ Diagram 6: 1st Fresnel zone Transceiver Distance between TRs Any point between TRs Distance between P and one TR Distance between P and the other TR Radius of the 1st Fresnel zone corresponding to...

AN014 Ground influence One of the important phenomena impacting RF range is ground influence. The antennas should be placed as high as possible above the ground surface. The dependency is important especially up to 1.8 m. The ranges specified in IQRF TR datasheets assume the height 1.6 m for both TRs. Diagram 8: TR-72DA relative RF range vs. antenna height above the ground, 868 MHz and 916 MHz band. Absorption In addition to essential attenuation in free space, significant losses appear when penetrating possible obstacles. Estimated attenuation for various materials [in dBm] can be found at...

AN014 Application software RF range can significantly be influenced also in application SW. RF parameters (not only the basic ones such as output power and input sensitivity) are under SW control. Additionally, more or less advanced SW options and methods like LBT (Listen Before Talk) or channel switching are available to achieve the best possible wireless communication. However, they are beyond the purpose of this Application note. RF output power RF output power is selectable from 8 levels by IQRF OS function setRFpower(level). Diagram 9: Effective radiation power vs. level in the...