| The location and tracing wireless system positions target at a short distance, it is mostly designed to improve the luggage security and prevent the loss. The wireless signals are received by receiver RF destination antenna and are conversed frequencies by mixer. The conversion frequencies are amplified by IF amplifier, which are completed signals processing, located and tracked by digit circuits. High sensitivity receiver can receive RF signals at the most distance or remote point, and is beneficial to reducing the power loss of the transmitter. The receiver with wide dynamic range and high linearity can reject in-band interference, which will improve the reliability of the coherence crest value of the digit circuits, and will improve the location precision of the receiver.In chapter two, structural designs of the receiver RF destination include superheterodyne receiver, zero IF receiver, low IF receiver are introduced, whose advantages and disadvantages are compared, and the main parameters of the receiver RF destination are introduced. The receiver RF destination structural used in The location and tracing system is superheterodyne, whose technical parameters are distributed to each component of the system, and chips of the components are chosen. Meanwhile, budget gain, selectivity, phase noise and conversion frequency of the receiver RF destination are simulated and analyzed by software ADS in behavioral scale, which can be used to test the feasibility of the receiver designation.In chapter three, the designation and application of the low noise amplifiers (LNA) are optimized, and two different LNAs circuits and their cascade connection are both studied. For the requirement of high gain and low noise figure (NF) of the receiver RF destination, two LNAs most be cascaded, which is determined by each noise calculation of the two different LNAs. LNA MGA-645T6 circuit is optimized, which improves the impedance matching of the output port, and whose gain increases 1 dB. High Gain and High Linearity of the two LNA MAX2644 circuits are designed and implemented respectively, whose characters are analyzed and compared and High Gain design is selected. After implementing the design circuit of two LNAs respectively, their cascaded circuits are tested and the cascaded NF is calculated whose value equal to NF of the receiver RF destination approximately.In chapter four, the application circuit of the down-converter mixer MAX2681 is designed, whose converse gain and linearity are optimized. The output port impedance of MAX2681 is matched to 50 ?, which improves both the converse gain of the down-converter mixer and the linearity range of the input power. When the down-converter mixer and first stage circuits are connected, the gain of their cascade system will be so high that input power will be easily outside the linearity range of the MAX2681. For narrowing the gap between the linearity of the applied circuit and the design parameters of the whole system, the improving methods are presented.In chapter five, two IF amplifier AD8367 need to be used in a cascade way, due to consider the receiver sensitivity, and a gain control circuit also needs to be designed between the IF amplifiers to leave off the output signal. But the NF and the linearity interact with each other in the cascaded amplifiers, for this reason the gain control circuit must be optimized. There a gain control designation has been improved in the massage, whose sensitivity and linearity both satisfy the system designation requirements, and this designation is successfully used in the receiver RF destination of the location and tracing system.In chapter six, schematic design, PCB design and application circuits of receiver RF destination are all implemented and the important system parameters are tested by using the spectrum analyzer. After analyzing and studying the circuits test parameters and design parameters, the improving methods and the next works are presented at last. |
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