RF filters are a key part of RF design as the filters enable the required signals to be selected and unwanted ones removed.
- It is an electronic component that is used to allow or block selected signals or frequencies to eliminate noise or pass-through of unwanted signals.
- The RF filter is defined as passing radio frequencies within the desired band and blocking the undesired or unwanted radio frequencies in a wireless communication chain.
- These filters have various types based on the requirement. Such as in the RF up-conversion chain below, used to convert 70 MHz IF input to 6GHz RF output filters is employed as per need in the design.
- As shown below figure the input is 52-88 MHz low pass filter is used using discrete components.
- The low pass filter frequency is mixed with a local oscillator frequency of 1112.5 MHz and generates a new output signal 1182.5 MHz.
- After the first mixer BPF (band pass filter) new output signal is 1182.5 MHz with a bandwidth of 36MHz employed.
- Then the second stage of mixing, a 5925 to 6425 MHz microstrip-based parallel coupled band pass filter is incorporated.
- There are two types of RF filter.
- Low pass Filter
- High pass Filter
Low Pass Filter:
- It is the type of frequency domain filter that is used for smoothing the image. It attenuates the high-frequency components and preserves the low-frequency components.
High Pass Filter:
- It is the type of frequency domain filter that is used for sharpening the image. It attenuates the low-frequency components and preserves the high-frequency components.
Applications of RF & Microwave Filters
- RF filter is used in broadcast receivers to select desired channel frequency and reject all the other frequency channels.
- It is used in image frequency rejection in radio and TV receivers as well as satellite receivers.
- The RF filters are also used in multi-way loudspeakers.
- This filter is used for noise reduction.
- They are also used to stop LO leakage in RF transceiver designs.