Phase Locked Loop (PLL) Oscillator Circuit 860 MHz

This 860 MHz Phase Locked Loop (PLL) oscillator circuit is designed for a 1200 MHz transverter's local oscillator with 435 MHz rigs. The oscillator utilizes Toshiba PLL synthesizer integrated circuits (ICs). The TC9122P serves as a preset counter for determining the requested frequency value through patching. The TC5081AP functions as a phase comparator, while the TC5082P operates as a binary counter for 2048 divisions. The TC5082P is also integrated with a crystal oscillator circuit. A 12.8 MHz signal is divided by 2048 to yield a frequency of 6.25 kHz. The MB501 acts as a prescaler with a division factor of 64. The input of the TC9122P must be patched for 2150, resulting in a frequency of 6.25 kHz multiplied by 2150 and then by 64, which produces the target frequency of 860 MHz. The Voltage Controlled Oscillator (VCO) is manufactured by MURATA as MQC-302-856. The loop filter is a simple lag-lead filter. The output RF signal is amplified using a Monolithic Microwave Integrated Circuit (MMIC). The uPC1675G is not suitable for this application due to its output characteristics; instead, the MAR-3 is recommended. The uPC1675G has a PiMAX of 0 dBm and a power output (Po) of 4 dBm, whereas the MQC-302-856 outputs 1 dBm, which is excessive for this application. By using the MAR-3, an RF output of 11 dBm can be achieved. This local oscillator is intended for use in a 1200 MHz to 435 MHz converter, combined with a TUF-5 double-balanced mixer (DBM). The TUF-5 requires a +7.5 dBm LO input for maximum conversion gain. Additionally, a pad should be placed at the input of the DBM to reduce distortion. An output level of 11 dBm is considered adequate for this application.

This circuit is structured around a PLL oscillator that effectively generates an 860 MHz signal suitable for RF applications. The TC9122P IC functions as the core frequency synthesizer, allowing for precise frequency setting through its patching capability. The phase comparator, TC5081AP, ensures that the output frequency remains locked to the desired frequency by comparing the phase of the output signal with that of the reference signal. The TC5082P not only counts the frequency divisions but also incorporates a crystal oscillator, which serves as a stable frequency reference.

The frequency division process begins with the 12.8 MHz signal, which is divided down to 6.25 kHz using the TC5082P. This lower frequency is then multiplied by 2150 and subsequently divided by 64 using the MB501 prescaler to achieve the final output frequency of 860 MHz. The choice of the MURATA MQC-302-856 VCO is critical, as it is designed to operate efficiently within the desired frequency range.

The loop filter, implemented as a simple lag-lead filter, plays a vital role in stabilizing the output frequency and minimizing phase noise. The output RF signal, initially at 1 dBm, requires amplification to reach suitable levels for mixing. The MAR-3 MMIC is selected for this purpose, providing a higher output power of 11 dBm, which is necessary for optimal operation with the TUF-5 DBM.

In summary, the design integrates various components to form a robust PLL oscillator circuit capable of generating an 860 MHz signal, suitable for use in transverter applications. The careful selection of components and configuration ensures that the circuit meets the necessary performance criteria for effective RF signal processing.This 860 MHz Phase Locked Loop (PLL) oscillator circuit is for 1200 MHz transverter`s local oscillator with 435MHz rigs. The oscillator circuit uses PLL synthesizer IC`s of Toshiba for PLL circuit. TC9122P is easy to use preset counter for determining request frequency value by patching. TC5081AP is phase comparator and TC5082P is binary counter f or 2048 dividing. TC5082P has also been consited of Xtal oscillator circuit. 12. 8MHz is divided by 2048 into 6. 25Khz. MB501 is a 64 dividing prescaler You must patch the input of TC9122P for 2150, and 6. 25kHz*2150*64 comes to 860MHz. Parts VCO made by MURATA as MQC-302-856. The loop filter is simple lag-lead filter The output RF signal is boosted by MMIC. The uPC1675G is not suitable for this level, you may use MAR-3 instead. Because the uPC1675G`s PiMAX is 0dBm and then Po:4dBm, MQC-302-856`s output of 1dBm. is over power. If you use MAR-3 instead you will get 11dBm of RF output. I would like to use this LO for 1200 MHz to 435 MHz converter and combining with TUF-5 DBM. TUF-5 asks +7. 5dBm LO input for MAX conversion gain. And on the input of DBM there should be placed PAD for decreasing distortion. 11dBm output level is adequate, so I think. 🔗 External reference