초록
This thesis investigates the RF signal processing system to be utilized in the spectrum analyzer with 0 to 1.5 CHz frequency measurement range and -110 dBm to -30 dBm amplitude range.
The RF signal processing unit in spectrum analyzer generally consists of the 3 frequency converters, a variable bandwidth filter, a step gain amplifier, and a log amplifier. The first frequency converter employing a doubly balanced diode mixer converts the 1.5 GHz input signals to 2.05 GHz. The thirteenth order microstrip Chebyshev filters are followed to eliminate the image signals. The second frequency converter converts the frequency 2.05 GHz to 321.3 MHz. It includes a bandpass filter, a LO resonator using the coaxial cavity, and a diode mixer. The last frequency conversion from 321.3 MHz to 21.4 MHz is made using the LO resonator with a SAWR and a ring-diode mixer.
The resolution of the frequrncy separation of the down-converted signal is controlled by a variable bandwidth filter, which is designed to have the bandwidthes of 3 MHz, 1 MHz, 300 KHz, 100 KHz, 30 KHz, 10 KHz, 3 KHz, and 1 KHz.
The step gain amplifier implemented consists of a 10 dB amplifier and two 20 dB amplifiers. The amplifier has 50 dB gain in total when all the amplifiers are on, while it has unit gain with all off.
The log amplifier is realized with 7 amplifiers, each of which has 10 dB gain and can be selected to operate in either linear or log amplification mode. Following the amplification section, a detector captures 21.4 MHz IF signal and provides the vertical deflection signal for display.
Design and implementation of a RF signal processing system is proposed in this thesis, which can guarantee an efficient performance at the moderate product cost so that it may be utilized directly in the practical spectrum analysis system
닫기