Ultra-high frequency voltage-controlled oscillator constructed with UPC1651

The voltage-controlled oscillator is a key circuit in the frequency synthesizer. When making amateur radio communication equipment, in order to make the local oscillator have a smaller phase noise and a smaller step frequency, an oscillation circuit with a higher oscillation frequency and a larger frequency step is generally used, and then a high-speed frequency divider is used for frequency division. However, the oscillation frequency is high and the production is difficult. The voltage-controlled oscillator made by the author using the broadband integrated amplifier μPCI651 (or μPCI676) is very simple, small in size and easy to start. It can work almost without debugging.

The circuit is shown in the figure. When the oscillation loop inductor uses a 30mm long resonant line, a frequency of 500MHz to 1000MHz can be obtained. The oscillation frequency range is greatly affected by the varactor diode, and the U-segment varactor diode in the waste E-tuning high-frequency head can be selected. The feedback capacitor and output coupling capacitor in the circuit should not be too large. If there is no suitable capacitor on hand, a double-strand enameled wire can be used instead.