Waveguides are the backbone of many RF interconnects, especially when high power and high efficiency are required. Unlike coaxial interconnect, waveguides have both a minimum and maximum cutoff frequency. The single mode waveguide bandwidth is typically claimed as the bandwidth for a waveguide and the frequency difference between the lower TE10 mode cutoff and upper TE10 mode cutoff. One method of extending the frequency range of waveguide structures is to add ridges along the waveguide propagation direction. Adding a double ridge has been known to extend the lower cutoff frequency of a waveguide substantially and allow for multi-octave bandwidths. An extension of this, the quad ridge waveguide, makes use of two sets of ridges that not only extends the bandwidth of a waveguide structure compared to a hollow waveguide, but also enables the injection of dual linear polarizations. Hence, a Quad Ridge Dual Polarized Broad Band Gain Horn Antenna, is simply a horn antenna constructed of quad ridges that is capable of dual polarized operation.
Common Electrical Specifications & Features For Quad Ridge Horn Antennas
- Frequency range [Hz]
- Gain [dBi]
- VSWR [ratio]
- Interconnect impedance [Ohms]
- Antenna pattern [directional]
- Polarization [dual linear]
- RF connector [quad ridge waveguide or coax]
Dual polarization is particularly useful in linear polarized systems, as it effectively doubles the density of the communication channel as separate communication streams can be sent along each polarization. Though a quad ridge waveguide may not be able to achieve the same theoretical maximum bandwidth that a dual ridge achieves, the benefit of allowing for dual polarity outweighs the marginally smaller bandwidth difference.
A major advantage of gain horn antennas is that they are extremely directional. This means that the antenna pattern for gain horn antennas is concentrated in a central main lobe. Hence, these antennas offer both high gain/directivity, high bandwidth, and dual polarization. Modern design techniques and electromagnetic simulation have advanced the design and optimization of quad ridge waveguide structures compared to past approaches, which were more experimental than analytical. The new quad ridge waveguides geometric features include gradually sloping curves on the ridged, perforations, and skeletal frames that both minimize weight and are important electrical design features.
Many of these types of antennas use coaxial to waveguide transitions as a core structure of the antenna. For dual polarized antennas, there are multiple coaxial ports, one for each polarization. To make use of the maximum bandwidth of a quad ridge horn antenna that doesn’t have coaxial ports, it is necessary to use quad ridge waveguide transitions or other components. There are also quad ridge to dual ridge adaptors that can allow for the use of dual ridge transitions and other waveguide components.