Frequency Modulation

Phase Shifter

A phase shifter performs a controlled phase shift of an RF signal. Phase shifters are used in electronically controlled antennas, so-called phased arrays. Other applications are phase modulators, test operations and frequency converters. Phase shifters are available in active form where the signals are amplified, or in passive form where some damping or loss occurs during phase shifts. Analog phase shifters provide a continuously variable phase shift or time delay. Digital phase shifters provide a certain number of shifts based on the design and accuracy of the component. Phase shifters can be manual, motor controlled or electrically controllable. They are built with ferrite material, PIN diodes or MMIC, depending on application and power rating. The adjustment range of the phase shifting varies with type and design.

Mixers

A mixer is a component used for frequency conversion by processing of two signals. Mixers are used when the RF signal must be converted down before further signal processing. In its simplest form, a mixer uses a diode, but they can also be significantly more complicated for increased performance. Two categories of mixers that are often used in microwave applications are switching mixers and non-linear mixers. The first category includes "single-balanced" and "double-balanced" mixers and has more predictability properties than the nonlinear. However, non-linear mixers can be used high up in frequency (mm range). A non-linear part is also needed in the switching mixer. The non-linear part of a mixer is often a Schottky diode but can also be a FET or other type of transistor.
 
There are three ports on a mixer; RF (radio frequency), LO (local oscillator) and IF (intermediate frequency). On the RF port is where the signal to be converted is, or,
where the high frequency signal is output if the mixer is used for up conversion. On the LO port, RF is injected to control the mixer, and is used to switch the diodes in on/off position in a switching mixer. The RF signal that is modified is available on the IF port. Although some LO power is needed to power the mixer, it is considered to be a passive component, as long as it does not contain parts that actively amplify the signal.
 
The insulation is important in a mixer, and should be considered especially between the following ports: RF to IF, LO to IF, LO to RF
 
LO especially, can be a problem, since it is usually a stronger signal than the other two.
The problem with LO (RF signal) on the IF port is that these signals can cause spurious later in the signal path and possibly saturate the IF amplifier if they are strong enough.

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