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QMR1 Datasheet(PDF) 5 Page - rfsolutions.ltd |
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QMR1 Datasheet(HTML) 5 Page - rfsolutions.ltd |
5 / 8 page Ds302_3 AUG 01 © ©2001 REG No 277 4001 England Page 5 QM Receiver Module QMR1 / QMR2 Application Information Antenna Design The design and positioning of the antenna is as crucial as the module performance itself in achieving a good wireless system range. The following will assist the designer in maximising system performance. The antenna should be kept as far away from sources of electrical interference as physically possible. If necessary, additional power line decoupling capacitors should be placed close to the module. The antenna ‘hot end’ should be kept clear of any objects, especially any metal as this can severely restrict the efficiency of the antenna to receive power. Any earth planes restricting the radiation path to the antenna will also have the same effect. Best range is achieved with either a straight piece of wire, rod or PCB track @ ¼ wavelength (15.5cm @ 433.92MHz). Further range may be achieved if the ¼ wave antenna is placed perpendicular in the middle of a solid earth plane measuring at least 16cm radius. In this case, the antenna should be connected to the module via some 50 ohm characteristic impedance coax RF RF Helical Antenna Whip Antenna 34mm @ 433MHz 17 turns equally spaced ∅ = 5mm (inside) 15.5cm @ 433MHz Figure 5: Antenna Configurations To Be Used With The Modules Receiver Data Output Buffer The QMR1 receiver has a push-pull data output drive limited to 20uA. If drive problems are experienced, and sometimes they exhibit themselves in a poor system range, the following simple buffer stage should be incorporated between the module data output and the subsequent stage. This buffer is already present on the QMR2 receiver. U1 1K5 Data Out Data From Receiver +5V +5V U1 = SOT23 Package part number BU4581 (ROHM) Figure 6: Receiver Data Output Buffer |
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