Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 1 / 9

Basic filtering using GNU RadioComputer Science Department, University of Crete

Manolis Surligas surligas@csd.uoc.gr

October 13, 2016

Why do we use filters?

• Filters are used to separate mixed signals

• Extract a specific band of interest

• Avoid undesired effects (aliasing, imaging e.t.c)

• Restore distorted signals

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 2 / 9

Filter types

• Analog Filters

- Implemented using electronic components (resistors, capacitors)

- Used in analog front-ends

- Standard performance

- Difficult to change their properties

- Application specific

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 3 / 9

Filter types

• Digital Filters

- Implemented in software

- Variable performance depending the processing resources

- Change their properties relatively easily

- Can adapt to any application

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 4 / 9

Filter types

• Low Pass Filters

- Frequencies above a threshold do not pass the filter

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 5 / 9

Filter types

• High Pass Filters

- Frequencies below a threshold do not pass the filter

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 6 / 9

Filter types

• Band Pass Filters

- Frequencies of a specific band pass the filter

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 7 / 9

Filter parameters

• Cutoff frequency: The frequency above (low pass filter) orbelow (high pass filter) which, the filter starts to attenuate thesignal

• Transition width: Control how steep is the attenuation of thesignal above (low pass filter) or below (high pass filter) the cutofffrequency

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 8 / 9

Filter parameters• Small transition width:

• Large transition width:

Manolis Surligas (CSD, UoC) Basic filtering using GNU Radio October 13, 2016 9 / 9