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Calculation of antenna azimuths and elevations within a link

1. Introduction

Deriving both dRSS and iRSS signals (as well as internal calculation of signal strength between ILT-ILR for the purpose of power control operation) requires the calculation of the relative antenna azimuths and elevations between transceivers of the same link.

For all angle calculations:

• the azimuth reference is either the transmitter - receiver path or the EAST direction
• the elevation reference is the horizontal plane or the transmitter - receiver path

The calculations of the azimuth and elevation of the receiver antenna in the direction of the peer-transmitter within a given link is performed as follows:

• Trial of the receiver antenna azimuth
• Trial of the receiver antenna tilt
• Calculation of receiver antenna azimuth
• Calculation of receiver antenna elevation derived from both tilt and the azimuth angles

The transmitter antenna azimuth and elevation in the direction of the peer-receiver are calculated using the same above-described algorithm, by swapping tx and rx variables.

2. How to set antenna height, pointing azimuth and elevation?

The Antenna pointing panels allows you to set:

	antenna height, antenna pointing azimuth reference antenna azimuth antenna pointing elevation reference antenna elevation

The 'height of the antenna should correspond to its definition in the selected propagation model for that link (e.g. it might be the height above ground, effective height or height above local clutter).

The antenna pointing azimuth reference: In SEAMCAT you have two options to set the reference of the antenna pointing (). The antennas can either be pointing, i.e. the direction of the main beam is towards the Rx or the Tx, or be de-pointing, i.e. the direction of main beam is by default towards EAST. The control of the pointing and de-pointing of the antenna is only between the pair (VLT, VLR), and (ILT, ILR). The principle is illustrated in the two graphics below (for the victim link).

The antenna azimuth: It allows you to steer the antenna to a certain angle with respect to the antenna pointing azimuth reference. It is .

Pointing	Depointing
In this example, the VLR antenna is pointing towards the VLT by default (red arrow). You can then set a specific aziumuth angle in order to steer the antenna away from the default reference. It is set to 0 in the illustration. This parameter may be used either to add certain variable parameter to the final link budget due to random de-pointing of antennas (e.g. in mobile environment), or to show deliberate de-pointing of antenna (e.g. choosing a particular gain point on the antenna directivity pattern).	In this configuration, the "antenna azimuth" is set to 10 deg, which results in the main beam to be sligtly shifted from the EAST direction.
Calculation azimuth reference is the transmitter - receiver path	Calculation azimuth reference is EAST
In this case the antenna are pointing at each other.	In this case the antenna are not pointing at each other and they are looking EAST.

The antenna pointing elevation reference follows the same concept as for "antenna pointing azimuth". When selected, the antennas are pointing toward the opposite transceiver of the same link. If it is not selected, it means that the antenna reference is fixed to the horizontal plane.

The antenna elevation: It allows you to steer the antenna to a certain angle with respect to the antenna pointing elevation reference. Adding the antenna elevation component allows you to simulate a real life antenna down-tilt or up-tilt. It is .

Pointing	Depointing
Calculation elevation reference is the transmitter - receiver path	Calculation elevation reference is horizontal
In this case the antenna are tilted at each other.	In this case the antenna are not tilted at each other. Where is the angle of the receiver antenna as seen from the transmitter antenna. It is defined as The corrected tilt function is defined as the tilt of the receiver antenna as seen from the transmitter antenna. This angle is derived from the tilt of the receiver antenna as follows which can be approximated to .

Note 1: De-pointing feature, is very useful to simulate beamforming for instance.

Note 2: Unless some intentional meaning of antenna de-pointing is foreseen in simulation scenario, it is recommended to always set the antenna pointing and elevation angle parameters to const=0, meaning that the main beam of the antenna is directed towards the corresponding pair transceiver in a link.

3. Conventions for angle definitions

• Azimuth angle: positive = counter-clockwise to the 0 deg reference

• elevation angle: positive = up-tilt to the 0 deg reference and negative = down-tilt to the 0 deg reference