| In recent years, the developments of wireless mobile communication technology have changed with each new day. With the popularity of the smart mobile, iPad, and other smart terminals, the demand of mobile internet increased greatly. The net charge for3G/LTE mobile network is quite expensive at present. WIFI is the supplement for3G/LTE mobile network. Compared with3G/LTE, it has incomparable advantage in price and network speed. IEEE802.11protocol requires that the transmitted power of WIFI products can not more than100mw, and this requirement makes the coverage of WIFI network small. A bi-directional amplifier is developed in this paper and it is implemented for the frequency range of2.4GHz to2.5GHz which observed the IEEE802.11protocol. The coverage area of the WIFI network and other applications of2.4GHZ frequency band can be extend by increasing the transmitted signal power and improving the sensitivity of the received signal.This bi-directional amplifier consists of low noise amplifier, power amplifier, power synthesis/distribution network, logarithmic detector, detecting circuit, receiving and transmitting switching circuit. Low noise amplifier circuit consists of two stage amplifier. The first stage LNA designed by the ATF-58143transistor and its matching circuit, and the second stage designed by MGA53543which is a MMIC LNA. By adding a surface mount filter between two stage amplifier, it can be able to filter out Out-of-band interference and harmonic interference. Power amplifier circuit is designed with a balanced structure amplifier, and it is designed with two identical power amplifiers designed by ATF-50189transistor. Then, a improved Wilkinson power divider is designed as power synthesis/distribution network. Detection circuit consists of directional coupler and MAX4001detection chip. A small fraction of the energy coupling from the main channel of coupler to provide detection chip, and it converts RF power signal into a voltage signal to switch control by switching circuit.Low noise amplifier, power amplifier, Wilkinson power divider and directional coupler all designed by using microwave circuit simulation software ADS2008. The design method of Printed circuit board by software of Altium Designer was adopted. Then, according to the design results, PCB of the bi-directional was fabricated and measured. The final measurement results that in the receiving mode,14dB gain and 4.0dB noise figure are achieved. In the transmitting mode, the startup level is5dBm, and5dB gain is achieved. All input reflection coefficient and output reflection coefficient are smaller than-10dB. |
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