Correcting Front-End RF Impedance Mismatch for 2.4GHz Wireless Long-Distance Data Transmission

In order to increase the higher competition in low-power wireless network communication market, a high-performance and low-cost product is necessary to distinguish the difference with others. Through integrating the system performance with suitable L-shape impedance-match circuit assisting with some network analyzer, this target with a 2.4 GHz radio-frequency (RF) product in long-distance data transportation seems to be promisingly implemented. In short-distance data transportation, the ideal output-link transportation rate (∼ max. 54 Mb/sec) is slightly influenced by impedance mismatch between power amplifier (PA) and antenna port. However, it is tremendously reduced at long-distance condition and the transportation rate is decreased to ∼ 24 Mb/sec. Using the attenuator to attenuate the real input signal to –70dB to simulate the real signal transportation, the packet error rate (PER) is less than 10% at a physical sublayer service data unit (PSDU) length of 1000 bytes under the communication 802.11g spec. as the real transmission rate is 20 Mb/sec. If the impedance of the transmission line is shifted, the long-distance transportation rate will be reduced to, almost, 20 × 24 / 54 = 8.8 Mb/sec. The transportation performance is greatly deducted. With the delicate design and the feasible component arrangement, the impedance mismatch influencing the long-distance (∼ 100 m) data transportation is overcome and reduced to the acceptable range. In this investigation using 3.3 V power supply, we observe that the selection of electronic components with miniaturization is also an art to reduce the radiation side-effect.