For this question it's probably easier to just memorize the answer rather than gain a full understanding of semiconductor physics, but here are some things that may help you remember.

Higher electron mobility enables faster switching speeds. Higher frequencies are going to need faster switching speeds. Gallium arsenide (GaAs) is a semiconductor material known for high electron mobility.

Some of the answers are pretty easy to rule out. Higher noise figures would actually be worse, not useful. Lower voltage junction drop is nice, but is not the primary concern with higher frequencies (switching speed is). Lower transconductance is essentially just higher resistance (technically, higher transresistance) which, like higher noise, is also not that useful here and is unrelated to frequencies being higher.

Lastly, this material from Wikipedia might be helpful in helping you to remember that electron mobility is particularly important in semiconductors:

Conductivity is proportional to the product of mobility and carrier concentration. For example, the same conductivity could come from a small number of electrons with high mobility for each, or a large number of electrons with a small mobility for each. For metals, it would not typically matter which of these is the case, since most metal electrical behavior depends on conductivity alone. Therefore mobility is relatively unimportant in metal physics. On the other hand, for semiconductors, the behavior of transistors and other devices can be very different depending on whether there are many electrons with low mobility or few electrons with high mobility. Therefore mobility is a very important parameter for semiconductor materials. Almost always, higher mobility leads to better device performance, with other things equal.

Memory tip: step on the GaAs (gas) and you have mobility.

Another memory tip: Gallium arsenide has UPWARD (UHF and higher) mobility

Last edited by thegrotto. Register to edit

Tags: none

DIP stands for Dual In-line Package, referring to the two rows of pins. It is a common type of through-hole integrated circuit and is frequently used in prototyping because it fits neatly into a solderless breadboard.

Tip: You take a DIP in a swimming HOLE.

"D" for device, "D" for DIP

The stereotypical cartoon image of a "computer chip" is actually a DIP.

Last edited by wv8edu. Register to edit

Tags: arrl chapter 4 arrl module 4e

MMIC = Monolithic microwave integrated circuit

From Wikipedia:

Gallium nitride (GaN) is a binary III/V direct bandgap semiconductor commonly used in bright light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronic[4][5], high-power and high-frequency devices. For example, GaN is the substrate which makes violet (405 nm) laser diodes possible, without use of nonlinear optical frequency-doubling.

Its sensitivity to ionizing radiation is low (like other group III nitrides), making it a suitable material for solar cell arrays for satellites. Military and space applications could also benefit as devices have shown stability in radiation environments.[6] Because GaN transistors can operate at much hotter temperatures and work at much higher voltages than gallium arsenide (GaAs) transistors, they make ideal power amplifiers at microwave frequencies. (Emphasis added)

An easy way to remember this one is it is the only non-Silicon answer.

Last edited by melds. Register to edit

Tags: arrl chapter 5 arrl module 5b

MMICs (or "mimics") are Monolithic Microwave Integrated Circuits designed for use in the 300 MHz to 300 GHz frequency range. They are typically designed to have a characteristic impedance of 50 ohms at both the input and output. This allows them to be cascaded in a circuit without the need for additional impedance matching components. This impedance also matches most up with most microwave test equipment allowing for easier connections.

Hint: MMIC's "mimic" the common impedance of your transmission line

Last edited by nimbius. Register to edit

Tags: arrl chapter 5 arrl module 5b

Noise figure (NF) is the ratio between the noise the receiver produces and the theoretical minimum noise for a perfect receiver:

\[\text{noise figure}=\frac{\text{receiver noise}}{\text{theoretical minimum noise}}\]

Since it is a ratio, and each value is measured in dB, dB will cancel. We can thus eliminate both values given in dBm.

Real-world receivers can never be as good as a perfect receiver, so the noise figure ratio will always be greater than unity. If this ratio is strictly positive, we cannot have negative values.

The only remaining answer is 2 dB.

Last edited by gschreiner. Register to edit

Tags: arrl chapter 7 arrl module 7c

Monolithic Microwave Integrated Circuit (MMIC) is a type of "black box" amplifier that makes design simpler because its characteristics are well-known and it has input and output ports with a 50 ohm impedance. It is essentially a "LEGO brick" that can be plugged into a circuit to get a fixed quantity of gain without any additional design work (in theory, anyway).

"Nearly infinite gain" is a characteristic of op-amps, which require supporting circuitry to control that infinite gain and do something meaningful with it. MMICs do not necessarily have a high Q factor. The remaining answer is non-technical and doesn't make much sense.

Quick Hint: MMICs "C" controlled "s" specified

Last edited by kd7bbc. Register to edit

Tags: arrl chapter 5 arrl module 5b

Monolithic microwave integrated circuits are typically packaged for use on PCBs. Thus, microstrip is the best type of transmission line for connecting to MMICs. Microstrip transmission lines consist of a ground plane, a dielectric (the PCB material), and a strip of conductor for the signal.

Memory trick: MMICrostrip

Hint: MMIC stands for "Monolithic Microwave Integrated Circut." Microstrip is in the correct answer.

Last edited by ironcal67. Register to edit

Tags: none

An RF choke allows the DC current to pass from the supply into the amplifier while blocking the RF from escaping the other direction. This is a common configuration due to the types of circuitry inside the MMIC (Monolithic microwave integrated circuit), while a separate "VCC IN" is very uncommon.

All amplifiers require bias -- you can't make more power from less power without that power coming from somewhere. And you can't supply DC power through a capacitor because capacitors block DC.

Hint: A POWER SUPPLy has OUTPUT ( the only answer with output )

Last edited by jerryfaughn. Register to edit

Tags: arrl chapter 5 arrl module 5b

Each lead or pin of an electronic device adds a parallel capacitance and a series inductance to that connection.

Surface Mount Devices (SMD) generally have shorter pins or no leads at all, which helps reduce both the capacitance and inductance associated with connections to the device. At VHF and above, these capacitive and inductive reactances may become significant, so it helps to minimize them.

Hint: stove 'range' as a surface

Last edited by comdijital. Register to edit

Tags: arrl chapter 4 arrl module 4e

This one is pretty easy. It's pretty obvious that surface-mount technology (known as SMT or SMD) is smaller than through-hole, and that by itself is an advantage. Though it's not really limited to RF, it's also an advantage for RF electronics.

Shorter circuit board traces are useful for RF because beyond a certain fraction of a wavelength, circuit board traces must be treated as transmission lines which complicates circuit board design.

Parasitic inductance and capacitance become more of a problem at RF frequencies because they can introduce impedance matching problems such as unwanted reflected power, further complicating circuit and circuit board design.

Therefore All these choices are correct when it comes to SMT advantages for RF.

Last edited by rjstone. Register to edit

Tags: none

The abbreviation "DIP" stands for Dual In-line Package. DIP is a common package type for a variety of electronic components. The package is rectangular in shape with two parallel rows of pins along opposite sides of the package. The pins extend downwards from the edge of the package so they can be soldered into a through-hole PC board or inserted into a socket. The package material for DIP components is usually plastic, but ceramic packaging is sometimes used for high-power components. Surface mount technology (SMT) is rapidly replacing DIP and other through-hole technologies due to its smaller footprint and higher pin densities.

The easiest way to remember what a DIP is is to recall the usual stereotypical "computer chip" depiction of a little black box with two rows of pins.

Last edited by kv0a. Register to edit

Tags: arrl chapter 4 arrl module 4e

Starting around UHF frequencies (300 MHz and higher), the inductance added by the DIP package leads becomes too large to ignore.

HINT: "Ultra," (UHF), & "excessive," (lead length), are terms going in the same direction.

Last edited by yr7 - extra. Register to edit

Tags: none