Microwave Concepts and Applications

Microwave Concepts

• Microwaves do not require special treatment from low-frequency circuits in circuits.
• Antenna gain in microwaves is proportional to antenna size.
• Waveguides have less loss compared to two lines and coaxial lines.
• Waveguides do not allow propagation below a cutoff frequency.
• Microwaves travel in a straight line and are not bent by the ionosphere.
• The dominant mode has the lowest cutoff frequency.
• Electric fields in TE modes are transverse to the direction of propagation.
• Klystrons and Magnetrons are active microwave devices.
• In TE modes, if n or m are zero, all fields are zero (TM mode).
• Higher frequencies result in more bandwidth (information capacity).
• Microwave wavelengths are between 1 mm to 1000 mm.
• Mode order is related to field configuration in a waveguide.
• Microwave communications developed after radar.
• Propagation in rectangular waveguides is not possible below the cutoff frequency.
• Waveguides are not affected by surrounding electromagnetic waves.
• Dominant mode is mode with lowest cutoff frequency.

Additional Microwave Concepts

• Magnetic fields in TM modes are transverse to the direction of propagation.
• Waveguide design depends on frequency and transmitted power.
• Mode order changes with waveguide dimensions.
• Higher frequencies allow for more bandwidth.
• Waveguides have cutoff frequencies below which propagation is not possible.
• Electromagnetic waves between 30 GHz and 300 GHz are millimeter waves (mm waves).
• A mode is only supported above its cutoff frequency.
• Microwaves operate between 3×10¹¹ Hz and 3×10¹²Hz.
• Microwave circuits need different treatment than lower frequency circuits.
• Rectangular waveguides have cutoff frequencies above which propagation is possible.
• Attenuator passes signals in a circular path (circulator).
• Dominant mode is the mode with the lowest cutoff frequency.
• Radar echo is impacted by target shape and size.
• Repeaters extend transmission range.
• Diversity improves system reliability but does not decrease availability.
• Receiver threshold depends on wideband noise power.
• IEEE defines millimeter waves from 30 to 300 GHz.
• Mode order depends on waveguide dimensions and is not independent of waveguide dimensions.
• Radar can be high-power and low-resolution.
• Fields are zero in TM mode if n or m equal to zero.
• Important component design types for microwave systems include circulators, filters, and isolators.
• One function of a circulator is to pass signals in a circular direction.
• A circulator helps protect the receivers from high-power transmitted signals.
• A magnetron is an active microwave device with significant power output.
• A waveguide is a hollow conductor for microwave signals.
• Probe method is a technique to insert or remove power from a waveguide.

Additional Concepts

• Attenuator, isolator, and filter functions.
• Skin effect at microwave frequencies.
• Microwave communication systems.
• Waveguide definition and function, and shapes.
• Difference between waveguide and mode cutoff frequencies.
• Dominant mode in a waveguide.
• Applications of microwave Systems (communications, military, radio detection and ranging (radar), etc.)