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# TitleAnswers to RF Cafe Quiz #46

All RF Cafe Quizzes make great fodder for employment interviews for technicians or engineers - particularly those who are fresh out of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons who are going to be interviewed for a job. Bonne chance, Viel Glück, がんばろう, buena suerte, удачи, in bocca al lupo, 행운을 빕니다, ádh mór, בהצלחה, lykke til, 祝你好運. Well, you know what I mean: Good luck!

Note: Some material based on books have quoted passages.

This quiz is based on the information presented in Handbook of RF, Microwave, and Millimeter-Wave Components, by Sergey M. Smolskiy, Leonid A. Belov, and Victor N. Kochemasov.

1.  What type of switch is shown to the right?

c)  Transfer switch

A transfer switch in this case is a 2-position switch that allows simultaneous signal re-routing between four ports. In this case either ports 1-4 and 2-3 are connected, or ports 1-2 and 3-4 are connected. Transfer switches are often used in redundancy schemes.    (see page 214)

a)  Combination connector between-series adaptor and an attenuator

Adapto-attenuators are simultaneously the adapters; i.e., improve the section matching and the coupling the connectors of different types, and provide the given attenuation value.    (see page 87)

3.  What do we call the difference in decibels of the power output at a coupled port, when power is transmitted in the desired direction, to the power output at the same coupled port when power is transmitted in the opposite direction?

a)  Directivity

The difference in decibels of the power output at a coupled port, when power is transmitted in the desired direction, to the power output at the same coupled port when power is transmitted in the opposite direction.    (see page 116)

4.  What is the main use of a circulator?

d)  To unidirectionally direct signals from one port specifically to another

A circulator is a passive nonreciprocal three- or four-port device, in which microwave or radio frequency power entering any port is transmitted to the next port.    (see page 124)

5.  What is a lumped element element filter?

b)  A filter constructed of standard wire-wound inductors and parallel plate capacitors

A distributed element is constructed from a circuit board trace having a specific width and length that exhibits an impedance equal to a lumped element's impedance at the same frequency.    (see page 137)

6.  What is a very desirable feature of a YIG (yttrium-iron garnet) filter?

d)  All the above

Frequency filters based on microwave YIG filters have the noticeable advantages: high values of the Q-factor. opportunity of the electrical control by several octaves, and high linearity of the medium frequency control. Bandpass filters can be made to tune ranges as broad as 20:1 with few compromises in performance and even larger ratios with trade-offs depending on actual frequency.    (see page 150)

7.  What does the image to the right represent?

b)  16-QAM constellation

Quadrature modulation uses in-phase and quadrature data streams to generate a predictable combination of voltage-phase points that represent unique values. In that case of 16-QAM, it allows 4 data bits to exchanged in a single clock cycle, effectively multiplying the Baud rate so it is greater than the data clock rate.    (see page 16)

8.  In which operational region of an amplifier is its1 dB compression point?

d)  Nonlinear region

The 1 dB compression point is the output power level where an input signal is amplified by an amount that is 1 dB below its linear (normal) gain value. For instance, if an amplifier had a linear gain of 20 dB when the input signal is 0 dBm, then its output power would be +20 dB. If the amplifier with a linear gain of 20 dB only produced an output of +19 dBm with a 0 dBm input signal, then its 1 dB compression point would be +19 dBm since the gain is reduced by 1 dB at that power level, hence, it is nonlinear. Greater input power levels will experience an even lower gain.    (see illustration on page 249)

9.  What is an image rejection mixer?

a)  A mixer that prevents the image frequency from appearing at the output

For any LO (local oscillator) frequency, there are two frequencies (RF input) that will mix with it to produce the same output frequency (IF). One is the sum, and one is the difference. The undesired of the two frequencies is the image frequency.    (see page 288)

10.  What are the main electrical characteristics of a reference oscillator?

d)  Center frequency, stability, phase noise, harmonics, output power

As with most components, various circuit and mechanical configurations and frequency determining elements (crystal, YIG puck, cavity, etc.) are traded off to get the optimal performance for the requirement.    (see page 357)

Posted September 9, 2020