What is the selection criteria for intermediate frequency?
Intermediate frequency (IF) should be carefully chosen as – High IF results in poor selectivity and therefore poor rejection of adjacent channels. – High IF results in problems in tracking of signals in the receivers. – Image frequency rejection becomes poor at low IF or if very high.
What is an IF filter?
In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. When several stages of filters are used, they can all be set to a fixed frequency, which makes them easier to build and to tune.
What is an IF signal?
(Abbreviation for intermediate frequency signal.) The signal at an intermediate stage of radar and lidar receivers, chosen at a standard frequency (often 30 or 60 MHz) where amplifiers and filters are commonly available.
What does if mean in RF?
radio frequency
The basic concept of operation is as follows. For the receiver, the signal from the antenna is amplified in the radio frequency (RF) stage. The output of the RF stage is one input of a mixer. A Local Oscillator (LO) is the other input. The output of the mixer is at the Intermediate Frequency (IF).
Whats the difference between RF and IF?
In order to clarify the difference between RF and IF amplifiers, we need to know that in most radio receiver topologies the incoming high-frequency signal is not shifted down to the baseband in a single step. RF amplifiers used at those lower frequencies are referred to as intermediate frequency (IF) amplifiers.
How are two signals separated in a superhet?
In the superhet, the preselector only needs to select one of two signals that are separated by 910 kHz — a relatively simple task — while the tuned circuits in the TRF are required to separate signals as close as 10 kHz across the entire frequency range of the receiver.
How does the preselector work on a superhet?
This is done with a parallel-tuned tank circuit, also known as a preselector, that follows the antenna. It is important to realize that in the superhet receiver, the requirements on the preselector are greatly diminished compared to the tuned circuits in the TRF receiver.
What happens when you add more stages to a superhet?
Either increasing the gain of the individual stages or adding more stages to get more gain increases the inter-stage feedback, as well as the potential for oscillation. Avoiding this problem requires great care to shield and decouple each stage from all of the others.
What are the IF stages of a superhet radio?
In this way the IF stages of a superhet radio are some of the most exacting stages in terms of design. Gain, overload performance, filtering and a host of other requirements are key to the performance of the whole radio.