Newsletter 2018.3

Antenna Magus Version 2018.3 released!

Version 2018.3 includes 3 new antennas as well as various antenna improvements. This newsletter will discuss the new antennas that have been made available. For more comprehensive information on the update, please visit the full release notes.

New Antennas

The new antennas (taking the total number of devices in Antenna Magus to 338) are:

  • Combline Microstrip Stub Array
  • Pin-fed Non-Radiating Edges Gap-Coupled Microstrip Antenna (NEGCOMA)
  • Printed Folded Dipole with Groundplane

Combline Microstrip Stub Array
Image of the Combline Microstrip Stub Array.

Automotive RADAR systems are classed according to operating range into three main types, namely long-range (LRR), medium-range (MRR) and short-range RADAR (SRR). A LRR system is typically mounted on the front of a vehicle to detect objects up to 250m ahead, and thus requires a low-profile high gain antenna with a narrow beamwidth.

A suitable candidate antenna for LRR is the combline stub array. A typical design (13 elements) produces a high gain fan beam radiation pattern with a narrow 12.5 degree beamwidth. In an attempt to minimise interference from other RADAR systems from oncoming vehicles, the stubs of the array are rotated by 45 degrees from the normal position.

A taper applied to the elements further enhances the performance of the antenna. A Taylor distribution provides the best compromise between beamwidth and sidelobe level, while a Villeneuve taper results in the best reflection response.

Typical radiation pattern at 76.5 GHz (13 elements)
Typical reflection coefficient versus frequency for a 76.5 GHz design (1.2 % bandwidth)
Pin-fed Non-Radiating Edges Gap-Coupled Microstrip Antenna (NEGCOMA)
Image of the Pin-fed Non-Radiating Edges Gap-Coupled Microstrip Antenna (NEGCOMA).

Although microstrip antennas are very popular in the microwave frequency range because of their simplicity and compatibility with circuit board technology, their limited bandwidth often restricts their usefulness.

Various methods may be used to overcome this limitation, one of which uses gap- or direct-coupled parasitic patches. These are either placed along the non-radiating edges, along the radiating edges or along all four edges of the driven patch element.

The introduction of parasitic patches of slightly different lengths to the driven patch allows the staggering of resonant frequencies to yield a broader bandwidth. The impedance bandwidth of the NEGCOMA is approximately 3 times wider than that of a standard microstrip patch antenna.

Typical total gain pattern at 0.975f0, f0 and 1.025f0
Typical reflection coefficient versus frequency of a standard pin-fed patch vs NEGCOMA
Printed Folded Dipole with Groundplane
Image of the Printed Folded Dipole with Groundplane.

The printed folded dipole with groundplane is a simple planar structure, slightly smaller in size when compared to its wire counterpart. It is mainly used in mass-production electronics where the antenna must be etched onto the same substrate as the electronic components.

This antenna is designed to have an input impedance of 100 Ω and achieves an impedance bandwidth of approximately 10 %. It radiates a somewhat modified omnidirectional pattern due to the presence of the substrate and groundplane with a peak gain of approximately 2 dBi.

Typical gain at the center frequency
Typical reflection coefficient versus frequency