RU2477910C1 - Powerful attenuator - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: powerful attenuator contains N series-connected matched segments on similar substrates mounted with equal pitch on heat-conducting base, each next segment has larger attenuation than the previous one, note that transmitting coefficient of each segment power is set by the expression K_pM=N-M/N-M+1, where M - segment sequence number; N - segments quantity.

EFFECT: creation of powerful attenuator with increased reliability.

1 dwg

Description

The invention relates to the field of electronics and can be used as an equivalent load for testing powerful radio transmitting devices.

A powerful attenuator is known [1], which is a T-shaped link assembled from resistive absorbers made using the thin-film technology. Formulas are given for calculating the resistance values of series and parallel resistors. A powerful attenuator made up of such links, with acceptable electrical parameters and dimensions, would have insufficient reliability due to the lack of effective heat removal from them, i.e. equal to zero temperature gradient between any links (substrates) of the attenuator. In this case, overheating of individual substrates may occur, which will lead not only to a deterioration of the device parameters (including SWR), but also to its failure. This is due to the fact that in the literature there is no methodology for calculating the optimal transmission coefficient of units from the point of view of the same heat generation in them.

The closest in technical essence and the achieved result to the proposed device is a powerful attenuator [2], used as a load containing three matched links connected in series one after another on identical substrates installed on a heat-conducting base with the same pitch. The known device from the point of view of heat transfer is close to optimal due to the fact that the electrical and geometric characteristics of all substrates, as well as the step of their installation are selected the same. However, the selection of link transfer coefficients in order to ensure equal heat dissipation in them was not optimal. Thus, the lack of a method for calculating the optimal link transfer coefficient does not make it possible to fully ensure the maximum reliability of the attenuator, as well as the stability of its parameters (including SWR).

An object of the present invention is to provide a powerful attenuator with increased reliability.

The problem is achieved in that in a powerful attenuator containing N matched matched links sequentially on the same substrates, installed with the same pitch on a heat-conducting base, each subsequent link has a greater attenuation than the previous one, and the power transfer coefficient of each link is given by

K _PM = NM / N-M + 1,

where M is the serial number of the link;

N is the number of links.

In this case, heat fluxes from all substrates will be directed to the heat sink, and the temperature gradients between the substrates will be zero, due to which reliability is increased.

The drawing shows a structural diagram of the claimed device, where

1 - attenuator links;

2 - coordinated load;

K _P1 , K _P2 , K _P3 , ..., K _PN - transmission factors for power links;

P ₁ , P ₂ , P ₃ , ... P _N - power at the outputs of the links;

P _BX - input power.

Given that under the condition of equal heat dissipation, the power losses ΔР in all links should be the same, i.e. ΔP = P _BX / N, determined

K _P1 = P ₁ / P _BX = P _BX -ΔP / P _BX = N-1 / N;

K _P2 = P ₂ / P ₁ = P _BX -2ΔP / P _BX -ΔP = N-2 / N-1;

K _P3 = P ₃ / P ₂ = P _BX- 3ΔP / P _BX -2ΔP = N-3 / N-2;

-----------------------------------

K _PN = P _N / P _N-1 = P _BX -N · ΔP / P _BX - (N-1) · ΔP = 0/1 = 0

Then in general terms the formula will be presented as

K _PM = P _M / P _M-1 = P _BX -M · ΔP / P _BX - (M-1) ΔP = NM / N-M + 1

As can be seen from the derivation of the formulas, the transmission coefficient of the last link is equal to zero. It is impossible to realize such a transfer, therefore, with a tolerance acceptable for practical purposes, one can take a transmission coefficient equal, for example, K _PN = 0.001 (-30 dB).

Thus, the above formula makes it possible to accurately determine the transmission coefficients from the power of all links of the attenuator and with equal electrical and geometric characteristics of all substrates, as well as the same installation step, allows for equal heat dissipation in the substrates. It should be noted that the proposed device can only be used as a powerful load, since the transmission coefficients are not selected, but calculated.

As an example of practical execution of the calculation represented by the transmission power ratio of the attenuator units with power dissipation P _BX = 1 kW and lossy links in? P = 250 W (the substrate surface can be determined from the condition _gravies ≥ΔR S / P _UD, where _UD P [ W / cm ² ] is the nominal specific power dissipation of the substrate of the selected material).

Given that the number of links is N = P _BX / ΔP = 4, we obtain K _PM = 4-M / 5-M. Then K _P1 = _3/4 , K _P2 = _2/3 , K _P3 = 1/2, K _P4 = 0 or in dB:

K _P1 = -1.25 dB, K _P2 = -1.76 dB, K _P3 = -3.01 dB, K _P4 - take minus 30 dB.

It is these link transfer coefficients that the attenuator must have, so that, with equal electrical and geometric characteristics of all substrates, as well as the same step of their installation on a heat-conducting base, the heat release in the substrates is equal. The idea of equal heat dissipation in individual substrates of a powerful attenuator mounted on a common radiator is known, but so far no tool has been found to achieve this equality.

The application of this invention will improve reliability, expand the range of operating temperatures of the attenuator, and also increase the stability of its parameters (in particular, SWR) while maintaining all the positive qualities of similar known devices, such as low labor input, good noise immunity, and maintainability.

In addition, the design process for powerful attenuators is greatly simplified.

INFORMATION SOURCES

1. Blinov VV, Negrobov A.V. Powerful attenuator. // Antennas. - 2007. - Iss. 8 (123).

2. Korzh I.A., Winter V.N., Evdokimov M.A. Powerful film resistors on AlN and Al ₂ O ₃ substrates for high power RF attenuators. Proceedings of the international scientific and technical conference. REiS-2011.

Claims (1)

Powerful attenuator containing N matched matched links sequentially on the same substrates installed with the same pitch on a heat-conducting base, characterized in that each subsequent link has a greater attenuation than the previous one, and the power transfer coefficient of each link is given by
K _pm = NM / N-M + 1,
where M is the serial number of the link;
N is the number of links.