Frequency modulation and antenna size

In summary, to make antenna size small, we use a high frequency carrier to modulate the baseband signal. However, in frequency modulation, the carrier frequency varies, causing the antenna size to also vary. This means that multiple antennas of different sizes may be needed to receive a frequency modulated carrier signal, especially in cases like FSK where there are multiple levels and changes in the carrier frequency. To address this issue, real antennas have a certain bandwidth that allows them to cover the necessary frequencies, and the resonant length of an antenna is typically 1/2 of a wavelength.
  • #1
tensorbundle
15
0
We know to make antenna dimension reasonably small, we modulate baseband signal with a high frequency carrier. Antenna size as far as I know is in the order of one tenth of carrier signal wavelength. For example, for a 3 GHz carrier signal, receiver antanna size is 1 cm.
But, in frequency modulation, carrier frequency varies according to the baseband signal. As the antenna size depends upon carrier wavelenth, antenna size also varies! It implies we have to appoint several antennas of different sizes to receive frequency modulated carrirer signal!

Situation becomes puzzling to me when we use FSK (frequency shift keying). Digital baseband signal may have 32 (or more) levels implying 32 diffrent changes in the frequency of the carrier.Hence we need 32 different size antennas to receive the same FSK carrier signal.
How do we resolve this strange issue? Or is it I'm missing any point?
Thanks in advance.
 
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  • #2
Real antennas have a certain bandwidth, meaning they are usefull of over a range (band) of frequencies. Patch antennas and similar -often used in handheld devices- are designed to have a bandwidth wide enoiugh so that they cover the whole band needed for modulation schemes such as FSK.
 
  • #3
...And resonant antenna length is 1/2 of a wavelength (for a dipole), not 1/10 of a wavelength.
 

1. What is frequency modulation (FM)?

Frequency modulation (FM) is a method of encoding information onto a carrier wave by varying the frequency of the wave. This allows for the transmission of audio signals through radio waves.

2. How does FM differ from amplitude modulation (AM)?

FM and AM are both methods of encoding information onto carrier waves, but they differ in how the information is encoded. While FM varies the frequency of the wave, AM varies the amplitude. This results in different qualities of sound and different transmission ranges.

3. What is the relationship between frequency modulation and antenna size?

The antenna size plays a crucial role in FM transmission as it determines the wavelength of the carrier wave. The wavelength needs to be an appropriate size for the desired frequency in order to achieve efficient transmission. This means that for higher frequencies, smaller antennas can be used, while lower frequencies require larger antennas.

4. How does antenna size affect the range of FM transmission?

The size of the antenna directly affects the range of FM transmission. A larger antenna can transmit signals over longer distances, while a smaller antenna will have a shorter range. This is because the larger antenna has a higher gain, allowing for a stronger and more focused signal.

5. Can antenna size impact the quality of FM transmission?

Yes, antenna size can impact the quality of FM transmission. A larger antenna with a higher gain can provide a stronger and clearer signal, resulting in better quality transmission. In contrast, a smaller antenna may result in a weaker and more distorted signal, leading to poorer transmission quality.

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