Focused Practice

I. Answer the following questions:

1. When did NBS realize that noncombatant adults needed to protect their sensitive, but unclassified, information?

2. What did NBS issue a public solicitation for?

3. When is a conventional cryptosystem considered secure?

4. Could products incorporating DES be exported?

5. When did changes occur?

6. What did NIST announce in 1997?

7. Did NIST allow foreign submissions and foreign viewing of the candidates?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: DES replacement.

Unit 67 Grammar: Word Combination; that, this, the...The Construction Word List:

1. photo-etching	фототравление
2. substrate	материал, подложка, нижний слой
3. hybrid microstrip	гибридная микрополосковая схема
4. stripline circuit	схема, выполненная на микрополосках (вместо проводов)
5. low loss tangent	низкое значение тангенса угла потерь
6. dielectric constant	диэлектрическая постоянная (параметр)
7. permittivity	диэлектрическая проницаемость (параметр)
8. z-cut	срез, перпендикулярный к оси Z
9. chip	многофункциональная микросхема
10. single crystal	монокристалл

Mm–Wave Hybrid Microstrip

This paper reviews the current hybrid microstrip integrated circuit technology applicable to receiver operating in the 30 to 110 GHz frequency range to meet the requirements of both the low and high volume categories.

The form of mm-wave integrated circuit (mm-wave IC) discussed is that based on hybrid thin-film stripline circuits, with chip devices mounted on a metalized quartz substrate.

An important aspect of mm-wave ICs, as for microwave integrated circuits (MICs), is the transmission line for connection between circuit elements. Open microstrip has found wide practical acceptance for MICs; this structure consists essentially of a strip conductor deposited onto a flat dielectric substrate.

As at lower frequencies, the microstrip transmission line circuit is normally realized by thin-film technology, with the conductor shape or circuit pattern determined by photo-etching.

The quality of the substrate also is important. Microstrip circuit applications require a well controlled dielectric constant, low loss tangent and good surface finish. Conventionally, high purity alumina is used up to about 20 GHz, but above this frequency there is an advantage in reducing the relative permittivity of the substrate material, together with reducing the substrate thickness. Also, the lower the permittivity, the larger the circuit; this is of benefit for circuit design realization and application of hybrid techniques.

Quartz meets all of these criteria. Single crystal Z-cut is preferred, however, as it provides the advantage of a higher expansion coefficient. Circuits may be arrayed during the thin-film fabrication process for production purposes.

The preferred microstrip structure dimensions for acceptable transmission propagation with Z-cut quartz are 500 μm wide lines on 250 μm thick substrate and 250 μm wide lines on 125 μm thick substrate at 26 to 40 GHz and 75 to 110 GHz, respectively, for 50 ohm characteristics. The measured line losses are negligible.