Cross guide coupler

Today I’m going to write a few things about cross guide couplers. It’s an important piece of metal because every time I test an amplifier I attached a cross guide coupler to the output flange of the amplifier?to get accurate measurements of its output. It is exactly like the above picture one side of the coupler attaches to the amplifier and the other end is connected to the antenna feed. The power meter should be connected to the monitoring port.

Important point selecting correct side.

It is important to know which side is connected to the amplifier and which to connect to the antenna?and it does matter. All cross guide couplers have a symbol next to the monitoring port, two arrows one is pointed to the monitor port, and the next arrow point to the amplifier output flange. If we reversed the total measurement is useless.

Measuring power > It can be done in two ways,

1. Using a spectrum analyzer

2. Using a power meter

In either case, we cannot feed the spectrum and power meter the raw power from the satellite amplifier. The amplifier output must be reduced to a measurable level of the spectrum or power meter. So this is why we use cross guide couplers and it will attenuate the signal by an amount that most power meters or spectrum can read easily.

Let’s look at the label on the single monitor port Ku band coupler. This is tuned for the Ku band frequency range of 11.7 GHz to 12.2 GHz, but as frequency changes the attenuation also getting changed. So if you connected to the power meter to monitor the port and amplifier transmit frequency at 11.8 GHz the attenuation on the power meter should be set to 49.8 GHz. With these small adjustments, you can increase the output of the amplifier and see it correctly measured on the spectrum analyzer or power meter.

Some couplers have three ports, two ports oriented in the same direction and one of them has higher attention to accommodate a more sensitive signal. Other one is connected in reversed directions as we discussed earlier. It’s so interesting because it is monitoring radio frequencies coming back from the antenna feed. What is the reason behind this?

This is the point we need to think about reflected power. Turns and bends in the waveguide can cause a small obstruction that causes reflected power to feedback towards the amplifier. In high power outputs scenario, this could be a big problem, and therefore it is a good idea to monitor the reflected power in the circuits in advance, and correct them before it affects the circuit or the equipment.