Abstract: Focusing on the L-band, this paper discusses and designs a multi-band compatible upconverter, and completes the fabrication and debugging of the actual circuit. The design of each component, including PLL, AGC, IQ modulation, and impedance matching, is analyzed, and specific circuit implementation and test results are presented. Actual testing shows that the circuit can perform precise real-time power control and local oscillator frequency control, meeting the requirements of transmitters at different frequencies. Keywords: phase-locked loop (PLL), automatic gain control (AGC), IQ modulation, impedance matching Abstract: In this paper, taking L-band as the core, a design Compatible Multi-band Up-converter for radio frequency is introduced, and the real circuit is accomplished and tested. The design of PLL, AGC, IQ and impedance matched parts are analyzed. The implementation of the circuit and the test result are provided. The circuit can produce accurate real-time output power and the LO frequency. The practical test shows that the design can meet the requirements of the transmitters with different frequencies. Keywords: phase-locked loop (PLL), automatic gain control (AGC), IQ modulation, impedance matched 1. Introduction Up-converters are an indispensable and important component of radio frequency transmitters. Their performance is affected by electromagnetic compatibility and other factors [1]. Therefore, the design of up-converters is an important prerequisite for ensuring the quality of output signals. There are currently many up-converter chips on the market for specific applications, but they lack flexibility in use. The main upconverter circuit designs are also targeted at specific frequencies or bands, lacking designs for precise output power control and variable frequency control during operation. This paper designs a multi-band compatible upconverter based on L-band, combining practical engineering applications. This includes mixing, phase-locked loop (PLL) circuitry, automatic gain control (AGC) circuitry, attenuation, and electromagnetic shielding. Considering various influencing factors, the designed multi-band compatible upconverter allows for flexible setting of the local oscillator signal frequency and precise control of output power. Actual testing shows that the local oscillator signal is stable, the frequency can be arbitrarily set in the L-band using different components, and it can achieve a low-power signal output of -130dBm, with real-time adjustments in 0.25dB steps between -130dBm and -80dBm. For details, please click: Multi-band Compatible RF Upconverter Design