577453

Hellas-Sat 2 Satellite Manual

8
Zoom out
Zoom in
Previous page
1/15
Next page
User’s Manual
8
1.7 TWTA TRANSFER CHARACTERISTICS
All TWTA which are employed on Hellas- Sat 2 transponders provide a maximum output power
of 105W.
The OBO denotes the power level available at the output of the TWTA relative to that when the
transponder is saturated. The OBO is therefore very important for link budget calculations as it
provides the available power per carrier for one or more carriers in the down link.
Operation of the TWTA at saturation means that the maximum output power is obtained in the
down link which in turn directly affects the design of the terrestrial receive equipment.
When a number of carriers are simultaneously amplified at different frequencies by the power
amplifier of a satellite transponder or of a transmit E/S, non-linearities of the amplifiers cause
intermodulation, i.e produce unwanted signals, called intermodulation products.
The number of intermodulation products increases very quickly with the number of input
carriers (for example, for 3 carriers, there are 9 products and for 5 carriers there are 50).
However, in most cases only the third-order intermodulation products falling within the
frequency band of the wanted carriers are considered.
To reduce intermodulation products in multicarrier operation (FDMA mode) the TWTA needs to
be driven with a sufficient back-off: i.e an input back-off of about 9 dB corresponding to an
output back-off of about 4.1 dB. In the case of earth station HPAs, an output back-off is usually
required (3 to 8 dB). However the situation can be improved by the utilization of linearizers.
Above limitations do not apply in the case of a single carrier occupying the whole transponder
bandwidth and therefore the TWTA can be driven almost to saturation.
For a Hellas-Sat 2 TWTA, in different operational modes, the following total IBO/OBO values
may be employed:
No of Carriers
1 2 3 4 MultiCarrier
IBO 0 -5 -7.5 -7 -9
OBO 0 -2 -3.1 -3.9 -4.1
Trp 1-12,
Beams F2, S2
C/IM - 27.7 18.5 18 18
No of Carriers
1 2 3 4 MultiCarrier
IBO 0 -5 -8.5 -8 -10.5
OBO 0 -2 -3.5 -3.4 -4.9
Trp 13-24 & 25-48
Beams F1, S1, S2/F1
C/IM - 26.5 18 18 18
Table 2: IBO vs. OBO for multi-carrier operation
… 8 …


Need help? Post your question in this forum.

Forumrules


Report abuse

Libble takes abuse of its services very seriously. We're committed to dealing with such abuse according to the laws in your country of residence. When you submit a report, we'll investigate it and take the appropriate action. We'll get back to you only if we require additional details or have more information to share.

Product:

For example, Anti-Semitic content, racist content, or material that could result in a violent physical act.

For example, a credit card number, a personal identification number, or an unlisted home address. Note that email addresses and full names are not considered private information.

Forumrules

To achieve meaningful questions, we apply the following rules:

Register

Register getting emails for Hellas-Sat 2 Satellite at:


You will receive an email to register for one or both of the options.


Get your user manual by e-mail

Enter your email address to receive the manual of Hellas-Sat 2 Satellite in the language / languages: English as an attachment in your email.

The manual is 0,96 mb in size.

 

You will receive the manual in your email within minutes. If you have not received an email, then probably have entered the wrong email address or your mailbox is too full. In addition, it may be that your ISP may have a maximum size for emails to receive.

The manual is sent by email. Check your email

If you have not received an email with the manual within fifteen minutes, it may be that you have a entered a wrong email address or that your ISP has set a maximum size to receive email that is smaller than the size of the manual.

The email address you have provided is not correct.

Please check the email address and correct it.

Your question is posted on this page

Would you like to receive an email when new answers and questions are posted? Please enter your email address.



Info