What is local oscillator circuit?
A local oscillator is an electronic oscillator used to generate a signal normally for the purpose of converting a signal of interest to a different frequency using a mixer. Local oscillators are used in the superheterodyne receiver, the most common type of radio receiver circuit.
What is the frequency of local oscillator?
1090 MHz
The local oscillator will be operating at a frequency of 1090 MHz. The received and local oscillator signals are mixed, or heterodyned, in the converter stage and one of the frequencies resulting from this mixing action is the difference between the two signals, or 60 MHz, the IF frequency.
How do you choose a local oscillator frequency?
Assuming an intermediate frequency of 60 MHz, the local oscillator will track at a frequency of 60 MHz higher than the incoming signal. For example, suppose the receiver is tuned to pick up a signal on a frequency of 1030 MHz. The local oscillator will be operating at a frequency of 1090 MHz.
Why local oscillator frequency is higher?
The local oscillator frequency (f0) is made greater than signal frequency (Fs) in radio receiver: Hence, the 2.2:1 ratio required for the local oscillator operating above signal frequency is well within range whereas the other system has a frequency ratio of 14:1 whose capacitance are not practically available.
Why do we need local oscillator?
In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequency of the local oscillator and frequency of the input signal.
What does a local oscillator do?
Local oscillators are used to convert an incoming frequency to another frequency and sometimes are used to convert from one internal frequency to another.
Which oscillator is used as a local oscillator in radio receiver?
Explanation: Oscillator which is used as a local oscillator in radio receiver is generally a tuned circuit. This tuned circuit consists of inductors and capacitors to determine the resonant frequency, therefore it is an LC tuned circuit.
What type of local oscillator is used in most modern receivers?
What type of local oscillator is used in most modern receivers? Frequency synthesizers. Name three primary sources of external noise.
What is the purpose of local oscillator?
Where is local oscillator used?
They are also used in many other communications circuits such as modems, cable television set top boxes, frequency division multiplexing systems used in telephone trunklines, microwave relay systems, telemetry systems, atomic clocks, radio telescopes, and military electronic countermeasure (antijamming) systems.
How to improve phase noise in a local oscillator?
The ADF4106, in conjunction with a wide-bandwidth divider, can improve the phase noise and lock time of a standard local oscillator circuit at frequencies below 2.0 GHz. A typical wireless system might be generating frequencies in 200-kHz increments from 1450 MHz to 1500 MHz.
What is the intermediate frequency of a local oscillator?
Its tuning is ganged to that of an LC sine wave oscillator called the local oscillator, but with the two tuned circuits having a frequency difference called the intermediate frequency (IF). (Oscillators are described in detail in Chapter 11 .) In most cases the local oscillator frequency is made higher than that of the required carrier so that
What are the requirements for an oscillator circuit?
To maintain oscillation, the circuit must meet the requirements. Otherwise, the loop resonance condition cannot be met. The criteria for the three-terminal oscillator circuit to meet the phase equilibrium condition is as follows: (1) The reactance properties of Xce and Xeb are the same, but the reactance properties of Xcb are opposite.
Is the local oscillator higher than the carrier frequency?
In most cases the local oscillator frequency is made higher than that of the required carrier so that Fig. 9.26. A superhet receiver. where fLO is the local oscillator frequency, fS is the r.f. signal carrier frequency and fIF is the intermediate frequency.