Introduction of Frequency range of waves and Frequency Band Designation

  Introduction:

The microwave refers to an alternating current signals with frequencies between 300 MHz and 300 GHz with corresponding electrical wavelength between λ = c/f = 1m and λ = 1mm respectively. It is quite impossible to solve microwave network problem using standard circuit theory directly but standard circuit theory is an approximation of the broader theory of electromagnetism as described by Maxwell’s equations.
The lumped circuit element approximations of circuit theory are not valid at microwave frequencies significantly over the physical extent of the device, because the device dimensions are on the o. Microwave components are often distributed elements, where the phase of a voltage or current changes significantly over the physical extend of the device.

Microwaves are desirable for communications and radar applications because of their high frequency and short wavelength. The high frequency provides wide bandwidth capacity. The term microwave refers to alternating current signals with frequencies between 300 MHz and 300 GHz, with a corresponding wavelength between and =1 mm, respectively

Microwaves are electromagnetic waves whose wavelengths are ranging from one meter to one

millimeter. Equivalently we can say that the frequencies of microwaves are ranging from 300 MHz (0.3 GHz) to 300 GHz are known as microwaves. Very Low Frequency (VLF), Low Frequency (LF), Medium Frequency (MF), High Frequency (HF), Very High Frequency (VHF), Ultra High Frequency (UHF), Super High Frequency (SHF) & Extreme High Frequency (EHF) all are treated as microwaves as their frequency range is in between the frequency range of microwave frequency range. The frequency band with their designation & typical service are given below as a form of table.

Table 1.1:       Frequency Band Designation.

Frequency Band	Designation	Typical Service
3 – 30 kHz	Very Low Frequency (VLF)	Navigation, Sonar
30 – 300 kHz	Low Frequency          (LF)	Radio beacons, Navigational aids
300 – 3000 kHz	Medium Frequency   (MF)	AM Broadcasting, Maritime radio, Coast Guard Communication, Direction finding
3 – 30 MHz	High Frequency         (HF)	Telephone, Telegraph, Facsimile, Shortwave international broadcasting, amateur radio, Citizen’s band, Ship-to-coast and ship-to-aircraft communication
30 – 300 MHz	Very High Frequency (VHF)	Television, FM broadcasting, Air-traffic control, Police, Taxicab mobile radio, Navigational aids
300 – 3000 MHz	Ultra High Frequency (UHF)	Television, Satellite communication, Radiosonde, Surveillance radar, Navigational aids,
3 – 30 GHz	Super High Frequency (SHF)	Air borne radar, Microwave links, Common- carrier land, Mobile communication, Satellite communication
30 – 300 GHz	Extreme High Frequency (EHF)	Radar

 

Figure 1.1: Frequency range of waves.

In the UHF band, up to around a frequency of 1 GHz, most communication circuits are constructed using lumped-parameter circuit components. But in the frequency range from 1 up to 100 GHz or higher, lumped circuit elements are usually replaced by transmission line and waveguide components, generally known as distributed components because at high frequency typical inductor becomes short circuit and capacitor becomes open circuited; therefore, some new suitable realizations and technologies are badly needed for wireless system in case higher frequency operation.