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General rule of thumb:
*The higher the frequency the smaller the antenna.
*For the special case of patch antennas: The more antenna patches placed, the narrower the beam widthbeamwidth.*Connections from IC to antennas such as bond wires etc. causes cause impedance mismatch, decreasing efficiency , and bandwidth. This has to be matched again during antenna design. The smaller and less tolerant the structures, the easier the matching (for example an antenna on -chip is easier to match compared to an antenna on PCB).
= External Antenna =
Disadvantages:
*Hard to find for higher frequencies
*Transmission to the antenna has high loss for higher frequencies, especially over the connectors
*Not suitable for high bandwidths
= Antenna on PCB =
Antennas can also be designed directly on a high -frequency PCB. RF-PCB materials are normally verified up to 110 GHz; however successful designs are also possible at 120 GHz ISM band.
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Advantages:
*Flexible antenna designs are possible since the area is not limited as in the case of antenna on chip or on package
*Cheaper for prototyping compared to antennas on chip or on package
*Antennas can be placed very close to the IC on PCB, so transmission from IC to antenna can be efficient
Disadvantages:
*Long bond wires may limit the performance (depends also if bare IC is directly wire bonded to PCB or already in a package)
*Standard PCB technology is limited, also limiting the matching structures of antenna designs resulting in less efficiency at higher frequencies
*Standard PCB tolerances are high, increasing the center frequency shifts of final designs
*Not suitable for extremely high bandwidths
= Antenna in Package =
Antennas can also be placed directly in high -frequency package. This increases the choice of materials and technologies (for example thin film) to design antennas. But in this case, the area may be limited, if compared to antennas on PCB. Successful designs are possible up to 160 GHz and above.
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= Antenna on Chip =
Antennas can be placed directly on Silicon IC. This allows very fine structures down to a few microns size, however , the total antenna area is limited. High performance integrated antenna structures are possible up to THz-range.
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Disadvantages:
*Antenna area is limited, therefore narrow antenna beams are not possible
*May be Maybe more expensive for prototyping
*Not suitable for low frequencies such as 24 GHz
