AD416 DGPS, GPS and GLONASS L1/L2 antenna with Ceramic Filters

A lower cost general purpose antenna with high build quality and ruggedness

Figure 1. AD416 antenna. The overall diameter of the base is 150 mm
Figure 2. General assembly of the AD416 antenna

Mechanical Specification

The antenna case is a machined from solid aluminium and hard anodised resulting in a rugged 150 mm diameter base which is extremely resistant to salt water corrosion.

The radome is a 4 mm thick GRP pressure molding which can be painted to any colour requested.

The antenna is sealed to a minimum of IP67 with an ‘O’ ring preventing water ingress between the case halves; the limiting factor is the seal between the type N connector on the antenna and the corresponding connector on the coaxial cable.

The mass of the antenna is 2.0kg. Outline dimensions are shown in the drawings. Provision is made for an optional ground-plane extension.

Electrical Specification

The antenna radiation pattern is RH circular (+/- 0.5 dB at zenith) and omni-directional in azimuth, whilst good reception can be achieved down to 5° in elevation, figure 3.

Figure 3. Antenna responses at GPS L1 and L2 frequencies

Ceramic filters are used in the AD416 with pass-bands selected for the frequencies required. The response for combined DGPS/ GPS/ GLONASS reception in the L1 band is shown in figure 4. A similar filter provides a passband for the frequency range 1164MHz – 1254MHz incorporating GLONASS and GPS L2 reception, figure 5.

Figure 4.  L1 filter response for an AD416 antenna, with passband tuned for reception of DGPS (1530 -1558MHz), GPS (1575.42MHz) and GLONASS (1597 -1611 MHz)
Figure 5.  The response of a broad-band interdigital filter for GPS L2/P2 and GLONASS reception

A single LNA is used for both L1 and L2 reception which employs a low noise Gas Fet input stage followed by a silicon bipolar MMIC. The amplifier’s gain is factory preset usually to 30+/-2dB for both L1 and L2, although other gains are available on request. A noise matching input circuit gives a total noise figure for the amplifier and filter that is <2.5 dB across each pass-band.

The supply voltage to the antenna is phantom fed via its coaxial downlead and is in the range of +5V to +20Vdc with a current of typically 45mA usually sourced from the receiver.

Operating temperature range is -45°C to +70°C and storage temperature range is -45°C to +100°C.

The antenna is environmentally tested to EN60945 (clauses 8.2,8.3,8.4,8.7,8.8), and complies with EMC requirements for emissions EN55022 and immunity EN5008-1, and is CE marked accordingly.