Table of Contents
- 1 How do you calculate local oscillator frequency?
- 2 Do you know the intermediate frequency in FM receiver is 10.7 MHz?
- 3 Why is the intermediate frequency of 10.7 MHz required for FM?
- 4 What is image frequency formula?
- 5 How is FM signal generated?
- 6 What is the principle of frequency modulation?
- 7 What is image frequency and its rejection?
- 8 Why do we use image frequency?
- 9 Is there an RF amplifier in an FM receiver?
- 10 What is the maximum deviation of a 200 kHz FM transmitter?
- 11 How does the limiter work in FM radio?
How do you calculate local oscillator frequency?
Calculation of the Image-Frequency
- 108,5 MHz = foscillator + fIF foscillator = 108,5 MHz – f. IF
- 87,0 MHz = foscillator – fIF foscillator = 87,0 MHz + f. IF
Do you know the intermediate frequency in FM receiver is 10.7 MHz?
Perhaps the most commonly used intermediate frequencies for broadcast receivers are around 455 kHz for AM receivers and 10.7 MHz for FM receivers. A first intermediate frequency may even be higher than the input signal, so that all undesired responses can be easily filtered out by a fixed-tuned RF stage.
What is the frequency of local oscillator?
The r.f. circuits and the local oscillator are all tuned by varactor diodes. The tuning range is from 470−860 MHz. At these frequencies, the circuit Q s are relatively low, with values of about 30 at 600 MHz.
Why is the intermediate frequency of 10.7 MHz required for FM?
The use of a receiver intermediate frequency of 10.7 MHz effectively eliminates the possibility of image channel interference arising from other emissions within the FM sound broadcasting band (87.5 – 108 MHz).
What is image frequency formula?
Image frequency rejection ratio (α) is given by: α=√(1+Q2ρ2)ρ=fsifs−fsfsi=23101400–14002310=1.043α=√(1+(1502×1.0432))=156.453.
What is image frequency and how it is rejected?
The image rejection ratio, or image frequency rejection ratio, is the ratio of the intermediate-frequency (IF) signal level produced by the desired input frequency to that produced by the image frequency. The image rejection ratio is usually expressed in dB. In a good design, ratios of >60 dB are achieveable.
How is FM signal generated?
FM signals can be generated either by using direct frequency modulation, which is achieved by inputting a message directly into a voltage-controlled oscillator, or by using indirect frequency modulation, which is achieved by integrating a message signal to generate a phase-modulated signal, which is then used to …
What is the principle of frequency modulation?
The basic principle behind FM is that the amplitude of an analog baseband signal can be represented by a slightly different frequency of the carrier.
What is bandwidth of FM signal?
Commercial FM signals use a peak frequency deviation of ∆f = 75 kHz and a maximum baseband message frequency of fm = 15 kHz. Carson’s rule estimates the FM signal bandwidth as BT = 2(75 + 15) = 180 kHz which is six times the 30 kHz bandwidth that would be required for AM modulation.
What is image frequency and its rejection?
The measure of a receiver’s ability to reject signals at its image frequency. It is normally expressed as the ratio, in dB, of the receiver’s sensitivity at the desired frequency versus the sensitivity at the image frequency. See Also. IF. Image Frequency.
Why do we use image frequency?
In heterodyne receivers, an image frequency is an undesired input frequency equal to the station frequency plus (or minus) twice the intermediate frequency. The image frequency results in two stations being received at the same time, thus producing interference.
What causes image frequency?
Is there an RF amplifier in an FM receiver?
In an AM broadcast receiver, there is seldom an RF amplifier in the front end. In an FM broadcast receiver, an RF amplifier provides two important actions, amplificationand local oscillator energy suppression. The signal from the antenna in a VHF receiver (such as an FM broadcast receiver) can be very tiny.
What is the maximum deviation of a 200 kHz FM transmitter?
25. A 200 kHz carrier is modulated by a 2.5 kHz signal. The fourth pair of sidebands are spaced from the carrier by 26. An FM transmitter has a maximum deviation of 12 kHz and a maximum modulating frequency of 12 kHz.
What is the percentage of modulation in an AM transmitter?
The percentage of modulation is 80 percent. The total sideband power is 6. For 100 percent modulation, what percentage of power is in each sideband? 7. An AM transmitter has a percentage of modulation of 88. The carrier power is 440 W. The power in one sideband is
How does the limiter work in FM radio?
Limiter In FM the information is encoded by changing the frequency of the carrier wave. Ideally, the carrier wave amplitude remains constant; in other words, the transmitter does not amplitude-modulate the carrier, and the envelope carries no information.