PLO and BUC in Satcom

Noise is always present in communications. Electronic systems generate some form of unwanted energy as spurious in the radio frequency. This unwanted energy termed as spurious signals (which can be harmonically related to the wanted signal, or not) and seen as spikes in a spectrum analyser can cause performance degradation withall data streams,including digital signal processing of video signals, for example. To overcome this noise, a product known as phase lock oscillator (PLO) is used, as the local oscillator in the BUC (Block upconverter). If the PLL (phased lock loop) is missing then television receivers will receive distorted, noisy images.

Types of PLO

Raditek is a San Jose based RF and wireless telecom manufacturer of systems, components and modules. They provide PLO (phase lock oscillator) from

Simple crystal oscillators (referred as XO) that is nearly 1000 ppm (parts per million) accurate followed by TCXO (temperature compensated crystal oscillator) with accuracies between 1 to 10 ppm.

The oven compensated crystal oscillator (OCXO) is accurate between 0.1 to 1 .0 ppm while expensive Caesium based (in atomic clocks) and Rubidium based oscillators are used as a reference with the highest stability.

Broadband connectivity is pervading almost every aspect of day-to-day living and with IoT (internet of things) increased visibility to high end performance in the C, Ku and Kasatcombands has become common place. The importance of Block upconverter (BUC) is critical , typically located close to the transmit antenna (which can be mobile as well as fixed).Satcom modems typically feed anL-band signalto an outdoor BUC after amplification and upconversion to the output frequency.  BUCs comprise of:

• SSPA – solid state power amplifiers

• Upconverter with a mixer, phase locked local oscillator and bandbass filters • IF (intermediate frequency) amplifier

• Power supply from a DC source.

Typical BUCs range in power levels depending on the frequency such as

• Ka band can deliver power from 1 to 15 watts to 100-200Watts

• X and Ku band can deliver power between 2 to over 1200 watts

• While C band can deliver power from 2 to 2000 watts.