carlosemdlm-blog

[carlosemdlm-blog]

How to choose a High Power Amplifier (HPA) properly

Here you have two interesting images from the magazine Microwave Journal (https://www.microwavejournal.com/) where you will find a comparison between TWTs and SSPAs.

Average Power (W) vs Frequency (GHz):

TWTs vs SSPAs (Pros and Cons):

Which of the two will you specifically choose for your application?

Enjoy thinking!   

[carlosemdlm-blog]

Tip: Anatomy of a mil-spec coaxial cable assembly

Here you have an interesting image about the anatomy of a mil-spec coaxial cable assembly and the standards that it follows.

Enjoy it!

Source: Microwave Journal (Aerospace and Defense, June 2019)

[carlosemdlm-blog]

AWGN vs Transfer Function

Is it possible to use an AWGN source to measure the transfer function of a Device Under Test (DUT)? Yes, it is. 

Please, look at the reasoning in the image below.

This is a simple, quick and CHEAP method to get the frequency response of a system.

Is it useful? Yes, it is again.

Take a look at this article of the Signal Integrity Journal and learn how to use this technique, for example, to compare different types of probes:

https://www.signalintegrityjournal.com/articles/1092-quick-simple-way-to-measure-the-system-bandwidth-of-a-scope-probe-system

Are you interested in AWGN? 

Just Noisecom (https://www.noisecom.com/).

Enjoy it!

[carlosemdlm-blog]

Couplers and Dividers - The Ideal Directional Coupler

In the image below, you can see the scattering parameters for an ideal directional coupler.

According to them, what will the behavior of the ideal directional coupler be?

The port 1 will be the input one since it does not have any reflected power (S11=0).

The port 2 will be the thru one since it is considered the direct path from the port 1 and due to the small value of c (the coupling factor), the power here will almost be the input power from port 1.

The port 3 will be the coupled one. It means that it will be the port where the signal samples will be taken (it is the main directional coupler use).

The port 4 will be the isolated one since the power here will be zero.

The theory is very simple, isn’t it? Nothing is easy in engineering.

Some additional questions to answer:

- Is it possible to achieve this ideal behavior?

- What happens if the input power goes through another port?

- What does the coupling factor mean?

- What about the port 4? Why is it not loaded?

Enjoy thinking!

[carlosemdlm-blog]

Tip: The Ingress Protection Ratings (IP Ratings)

The IP ratings define the protection of electrical enclosures against foreign bodies and moistures.

They are specified as follows:

IPxy where the x and the y are numbers that mean the protection degree against foreign bodies and moistures respectively.

For instance:

- Your microwave component packaging is specified as IP67.

- What does it mean according to the tables below? 

- It means that the enclosure is protected against dust and immersion up to 1 meter.

This kind of specification is used for military components and rugged ones.

Can you follow this reasoning?

[carlosemdlm-blog]

Tip: A Very Interesting RADAR Website

Here you have a link to very interesting web about radar basics:

- http://www.radartutorial.eu/index.en.html

This web is sponsored by some of the most important manufacturers in the industry and if you are connected to this application field I hope this information is very useful for you.

Enjoy it!

Image source: http://www.radartutorial.eu/01.basics/Radar%20Principle.en.html

[carlosemdlm-blog]

Tip: Phase Noise vs Jitter

An oscillator can be mainly defined by its operation frequency and its phase noise, but sometimes, the customers can define an oscillator by its operation frequency and its jitter.

Both parameters, phase noise and jitter, talk about the variations in the signal period, since this signal and, therefore, its operation frequency in the real world are not pure and this period uncertainty can cause issues in many customers’ applications. 

According to this reasoning, both parameter show the same reality and there is a connection between them. 

The jitter can be calculated from the noise phase as you can see in the following link from EE|Times:

- https://www.eetimes.com/document.asp?doc_id=1277196&utm_source=eetimes&utm_medium=networksearch

Other interesting links to go into detail about this concept are the following:

- https://www.analog.com/media/en/training-seminars/tutorials/mt-008.pdf 

- https://www.jitterlabs.com/

In summary, do not be scared if you get a phase noise requirement or a jitter one. Both are the same, both are connected and from now on you know how.

Enjoy thinking!

Image source: https://www.analog.com/media/en/training-seminars/tutorials/mt-008.pdf

[carlosemdlm-blog]

A picture is worth a thousand words - RF and Microwave Filters

Information and image source: 

- https://en.wikipedia.org/wiki/Filter_(signal_processing)

[carlosemdlm-blog]

Tip: Crest Factor and Non-linearities

The Crest Factor (CF) is the ratio between the peak value and the RMS value of a signal.

In the image below, you can see how to calculate the CF of a sinusoidal signal. 

The point here is, if we introduce this sinusoidal signal into an amplifier and the signal becomes saturated (the amplifier clips the signal), can be the comparison between the input crest factor and the ouput one used to measure the non-linearities of the system? What happens with the crest factor when the signal is clipped?

In fact, the crest factor is used to measure this kind of effects and it is even more interesting when the signal is modulated and some noise is also included in the analysis. 

This one is a very interesting and complex topic to research in depth.

Enjoy thinking!

[carlosemdlm-blog]

Tip: Signal to Noise ratio vs Carrier to Noise one

A signal that carries information is known as a “carrier”. Therefore, a modulated signal is a carrier as it carries information.

If we measure the ratio between the modulated signal power and the noise power, we will get the Carrier to Noise ratio of the system (C/N).

If the signal does not carry information (baseband signal or demodulated one) and we measure the ratio between this signal power and the noise power, we will get the Signal to Noise ratio of the system (S/N).

Either way, we are measuring the ratio between the signal power and the noise power of the system, but we use some different names to call the ratios in order to understand the type of signal that we are using.

Can you follow this reasoning?

[carlosemdlm-blog]

TIP: Infrared Electrical Inspections: Hot Point

Along a coax cable or a waveguide can appear what is known as a hot point.

This hot point is an area inside a cable or a waveguide with an extremely and abnormal high temperature which can cause failures under certain conditions.

For instance, imagine that the environmental working temperature is about 8ºC and one of the system cables has a hot point at 30ºC. It means that when the environmental working temperature is 30ºC (summer), the hot point temperature will be at least 60ºC what can cause an inappropriate electrical behavior and reduce the cable life time.

The hot points can be detected by thermography (infrared electrical inspection).

Is this information interesting for you?

Enjoy thinking!

Image source: http://www.infraredimagingservices.com/electrical-infrared

[carlosemdlm-blog]

Tip: How to use a Spectrum Analyzer

Are you interested in using a spectrum analyzer? Are you interested in measuring the phase noise, the spurious, etc. of a system?

Here you have the best video tutorial that we have been able to find on Internet by Electronic Notes (https://www.electronics-notes.com/articles/test-methods/spectrum-analyzer/how-to-use-spectrum-analyzer-operation.php).

Enjoy it!

[carlosemdlm-blog]

Tip: How to calibrate and use a Vector Network Analyzer (VNA) easily explained

Here you have an interesting video from MegiQ (https://www.megiq.com/rf-measurements/vna-video-tutorial) where a Vector Network Analyzer (VNA) is calibrated and used to measure some components.

Related concepts: 

https://carlosemdlm.tumblr.com/post/169220534164/the-scattering-matrix-how-to-measure-the-s

Has this video been interesting for you?

[carlosemdlm-blog]

Tip: How to match a WiFi antenna in the real life (Lumped impedance matching network example)

Here you have an interesting video from MegiQ (https://www.megiq.com/rf-measurements/vna-video-tutorial) where a WiFi antenna is measured and matched by a Vector Network Analyzer (VNA).

Do you remember the theoretical concepts shown here?

https://carlosemdlm.tumblr.com/post/163787273269/impedance-matching-networks-lumped-network

Enjoy it! 

[carlosemdlm-blog]

Tip: What is a microwave “baseball” switch?

A microwave “baseball” switch is a device that allows you to choose the output paths that the input signals will take. They are often used in redundant systems.

Why are they called “baseball” switches?

They are called “baseball” switches because the connections between the inputs and the outputs follow a diagram that looks like a baseball ball. Then, looking at this diagram you can see how the inputs and outputs are connected at a certain time.

Can you follow this reasoning?

Image source: New Era Systems, Inc.

[carlosemdlm-blog]

Tip: What is a FFF component?

A FFF component is a device that because of its Form (mechanical specification) and its Function (electrical specification) perfectly Fits within a system.

It would be very interesting, if there were at least two FFF components, for each part of the system that you are designing, since in this way you will have more options if one of the providers stops manufacturing the component or if the price of one of them rises a lot.

Can you follow this reasoning?

[carlosemdlm-blog]

Tip: A Non Reciprocal 3 Port Device - The circulator

Here you have an example of a non reciprocal 3 port device, the circulator.

The circulator is matched, lossless, but non reciprocal.

The S parameter matrix is not symmetrical (see the image below).

What is its function? It connects the ports 1 to 2, 2 to 3 and 3 to 1, but it isolates the rest of connections.

We will see an application later.

Question: All the passive devices built with simple materials are reciprocal, aren’t they? 

https://carlosemdlm.tumblr.com/post/169261196209/the-scattering-matrix-the-reciprocal-case

Yes, they are, but the circulator is not a passive device and it is not built with simple materials either. 

They are usually made of anisotropic ferrite materials which are often fed by a permanent magnet.

Can you follow this reasoning?

Information and image source: 

HXI Renaissance: 

- http://www.spantech.es/cat/HXI/CATHXI.html

- http://www.hxi.com/products/Isolators.asp

For more information: http://www.spantech.es/contacto.html