Answers to RF Cafe Quiz #46
All RF Cafe quizzes would make perfect 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.
Click here for the complete list of RF Cafe
Note: Many answers contain passages quoted in whole or in part from the text.
Return to RF Cafe Quiz #46
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)
2. What is an adapto-attenuator?
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)
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?
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
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)
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
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
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
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)