Following are the microwave bands : (a) X (b) ku (c) V (d) Q Arrange these in the order of increasing frequency :
(a), (b), (d), (c)
Place each band on the frequency scale and the order follows.
| Band | Frequency | Typical use |
|---|---|---|
| X | 8 – 12 GHz | Radar, military satellite links |
| Ku | 12 – 18 GHz | Direct-to-home television, VSAT |
| K | 18 – 27 GHz | — |
| Ka | 27 – 40 GHz | High-throughput satellite |
| Q | 33 – 50 GHz | Radio astronomy, millimetre links |
| V | 40 – 75 GHz | Short-range gigabit radio, 60 GHz WiGig |
Increasing frequency: X → Ku → Q → V, that is (a), (b), (d), (c) — option 4.
The two traps are the letters themselves. First, the sequence is not alphabetical — the letters are wartime code names, and the microwave order runs L, S, C, X, Ku, K, Ka, Q, U, V, W. Second, Q and V look interchangeable to anyone who has not learned the millimetre-band letters, and they overlap between 40 and 50 GHz; Q starts lower, at 33 GHz, so it precedes V.
"Ku" means K-under — the band immediately below K — while Ka means K-above. Getting that pair the wrong way round is the commonest error in questions of this type, and it is what option 1 is built on.
Why the millimetre bands are used at all, given that loss climbs steeply with frequency. Two reasons: the enormous bandwidth available — a 2 GHz-wide channel is unremarkable at 60 GHz and impossible at 2 GHz — and, for V band specifically, the oxygen absorption peak near 60 GHz. Absorption of about 15 dB per kilometre confines the signal to a short range, which is a defect for a long link but a virtue for dense short-range reuse: the same channel can be used again a few hundred metres away without interference.
Antenna size scales the other way, which is the other attraction: for a given gain, \(A_{e}=\dfrac{G\lambda^{2}}{4\pi}\), so a V-band antenna is tiny compared with an X-band one of the same gain — the reason 60 GHz radios fit inside a laptop.
Hence, the increasing order is (a), (b), (d), (c).
Similar Questions
There are three general purpose microwave tubes. The first is ordinary gridded tube, having electrodes like vacuum tube diode and triodes. The second type are those in which interaction between the electron beam and RF field takes place. The klystron is the example of the second type of microwave tubes. The third category of the device is one in which interaction between an RF field and electron beam is continuous. TWT (Travelling Wave Tube) is the example of this category.
Read the paragraph and answer the questions :
Microwave tubes are used as microwave amplifiers and oscillators. Three general type of microwave tubes in which third type tubes are important because in these tubes there is an interaction between an electron and an RF field is continuous. The Travelling Wave Tube (TWT) is the prime example of this interaction. It is an amplifier, whose oscillator counter part is called Backward Wave Oscillator (BWO). The second sub-group consists of tubes in which a magnetic field ensures a constant electron beam – RF field interaction, and this is complemented by the Cross-Field Amplifier (CFA). Multicavity Klystron is used as high and very high power amplifiers in the UHF and microwave ranges. The frequency range covered is from about 250 MHz to over 95 GHz. The reflex-Klystron is a low power microwave oscillator. It is assumed that oscillations are started by switching transients. For oscillations to be maintained the transient time in the repeller space cycle is given as \(T=\left(n+\dfrac{3}{4}\right)\) where n is an integer, each value of n is said to correspond to different reflex klystron mode. Reflex Klystrons with integral cavities are available in the frequency range 4 to 200 GHz.
The correct sequence of sub-systems of Klystron amplifiers as they appear in the direction of flow of electron beam is
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