L-Band ONETs

Status date

The Objective of the project was to develop, manufacture and qualify two L-Band ONETs for EADS Astrium satellites and the US market.

ONET are high power devices used for multi-point telephony applications. In this case, two 8x8 matrices were developed. In one of them the mass and the PIM were the critical points, whereas the second one was developed with the high power requirements of the US market in mind.

click for larger image


The Design implementation plan devised for the L-Band ONETs pursues as main objective to qualify two EQMs (one of them completely, another one only for high power applications) which fulfils the goal requirements established in previous section, within the schedule and cost constraints.

The background experience has streamlined the overall development programme in two phases: Design (this phase covered the requirements confirmation, concept selection and detailed design for the L-Band ONETs) and Qualification (after the CDR successfully surpassed, the EQMs were manufactured and tested).

Key issues considered during the development of the project  and to be achieved were:

  • A mass optimisation to be able to develop a competitive product within the mass requirements of the potential customers,
  • Low PIM levels,
  • Comfortable layout for an easy connectivity High power handling capabilities.

The required functional block diagram of this arrangement is shown below.

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This ONET development was requested to satisfy the needs of introducing in the market a product with low mass and low PIM. The optimisation of both parameters was achieved, although some improvements have to be done to have full compliance of the specifications.

Currently RYMSA is working on a second development which includes some filters and test couplers, which is the device requested by EADS Astrium to be integrated in their platforms like Inmarsat or Alphasat. All experience gained in the ONETs development is being applied in this second activity.

Additionally, the development of the second matrix (the high power one) leads us to a good position in the American market, which is very demanding in terms of power. Actually, some companies like Orbital Sciences or SS/LORAL have shown interest in this product.


The equipment finally consisted of the following main elements:

  • Upper and lower inner conductors,
  • Upper and lower covers,
  • Intermediate layer,
  • Connectors (SMA and/or TNC, depending on the case) .

The matrices are silver plated and black painted with AEROGLAZE Z-306.

The function of the matrices is to combine with low loss, 8 coherent input signals into one of 8 output ports depending on the input signals phase sequence. Thus, there are 8 modes of operation, a mode being defined as unique set of phase weights applied to each of the 8 input signals, so as to select any of the 8 outputs.

The selected layout allows to use only two housings with a thin lamina between them. For this design, we have implemented three cascade stages reducing bar-line section dimensions. In every step we provide a margin with multipactor above 11 dB for High Power Onet, for Alodine surface finish, depending on the maximum power. This allows a compact design with controlled mass.

The following tables summarize the requirements of the matrices.

Requirement Alternative 1
Low Mass
In-Band Frequency range 1525-1559 MHz
Nominal Impedance 50 Ohm
Return loss >21 dB
Isolation >20 dB
Input Power: Maximum norminal power 14.31 dBW
Output Power: Maximum continuous power 216 W
Insertion loss at the band centre < 0.5 dB
Multipaction margin 11.5 dB
PIMP (two 100W carriers) -120dBc (3th Order)
Connector Type SMA for inputs, TNC for outputs
Requirement Alternative 2
High Power
In-Band Frequency range 1525-1559 MHz
Nominal Impedance 50 Ohm
Return loss >23 dB
Isolation >20 dB
Input Power: Maximum norminal power 17.2 dBW
Output Power: Maximum continuous power 420 W
Insertion loss at the band centre < 0.35 dB
Multipaction margin 11 dB
PIMP (two 100W carriers) -140dBc (3th Order)
Connector Type TNC


Current status

The design of L-Band ONETs was developed and the CDR meeting held in June 2006. Two EQMs were manufactured and successfully submitted to their specific qualification test campaigns.