Mixer good or bad identification method - Database & Sql Blog Articles

What do we rely on when choosing a mixer? How do you know if a mixer is in good or not? Today, we will introduce the technical indicators of the mixer, so that you can identify the quality of the mixer yourself.

Mixer operating frequency

The mixer is a multi-frequency working device. In addition to indicating the operating frequency of the RF signal, attention should also be paid to the application range of the local oscillator and the intermediate frequency.

Mixer noise figure

The noise of the mixer is defined as: NF = Pno / Pso Pno is the total noise power transmitted to the output port when the input port noise temperature is the standard temperature at all frequencies, ie T0 = 290K. Pno mainly includes signal source thermal noise, internal loss resistance thermal noise, mixing device current shot noise and local oscillator phase noise. Pso is the noise power generated at the output for only the useful signal input.

Mixer conversion loss

The frequency conversion loss of the mixer is defined as the ratio of the microwave signal power of the mixer RF input port to the signal power of the intermediate frequency output. Mainly caused by circuit mismatch loss, diode's inherent junction loss and nonlinear conductance net conversion loss.

1dB compression point

Under normal working conditions, the RF input level is much lower than the local oscillator level. At this time, the IF output will vary linearly with the RF input. When the RF level increases to a certain level, the IF output increases with the RF input. The mixer is saturated. The RF input power when the IF output deviates from linear 1dB is the 1dB compression point of the mixer. For mixers of the same structure, the 1dB compression point depends on the local oscillator power and diode characteristics and is typically 6dB lower than the local oscillator power.

Mixer dynamic range

The dynamic range is the range of microwave input power when the mixer is operating normally. The lower limit varies depending on the application environment of the mixer. The upper limit is limited by the saturation of the RF input power, and usually corresponds to the 1dB compression point of the mixer.

to sum up

From the aspects of operating frequency, noise figure, conversion loss, 1dB compression point and dynamic range, the problems that should be paid attention to when selecting the mixer are described. You can try to determine the quality of a mixer yourself later.