## Archive for the ‘Radio Frequency’ Category

### WiFi Connected Serial Communication

Monday, September 26th, 2016

### Electromagnetic Induction: Faraday’s Law Lenz Law and Nonconservative Fields

Tuesday, August 30th, 2016

The lecturer goes into why Faraday's law always holds but Kirchoff's current law only holds with constant flux.

It appears that depending on how you rope your voltage measurement circuit into the same two circuit nodes you get quite different measurement results.

### Raspberry Pi Mobile Phone

Wednesday, February 4th, 2015

### Agilent ADS: Circuit Envelope Simulation

Wednesday, September 17th, 2014

Agilent ADS has several features that set it apart from other design packages.  It has nonlinear and "cross frequency" capability.  Envelope simulation is where you want to see the envelope of an RF signal.

I suspect ADS will become much easier to use once I understand how various data are held in arrays.

### EM Drive – Massless Propulsion Concept

Monday, August 4th, 2014

I have seen something about this before but wrote it off as nuts.  Looks like now I need to go through the theory as an exercise.

OverView

The technique described in this paper uses radiation pressure, at microwave frequencies, in an engine which provides direct conversion from microwave energy to thrust, without the need for propellant. The concept of the microwave engine is illustrated in fig 1. Microwave energy is fed from a magnetron, via a tuned feed to a closed, tapered waveguide, whose overall electrical length gives resonance at the operating frequency of the magnetron. The group velocity of the electromagnetic wave at the end plate of the larger section is higher than the group velocity at the end plate of the smaller section. Thus the radiation pressure at the larger end plate is higher that that at the smaller end plate. The resulting force difference (Fg1 -Fg2) is multiplied by the Q of the resonant assembly.

Harold G. "Sonny" White Video – later in the video he talks about his EM drive tests.

### Two Slit Experiment with Quantum Eraser Realized with RF Components

Sunday, August 3rd, 2014

For the optical version see: Home Made Quantum Eraser Experiment Using Laser 2 Slits Polarizer Material

I wanted to think about this experiment in terms of RF components to see if there was anything new I could extract.  In RF speak here is what happens.

Description I.T.O. Standard Radio Frequency Speak

With NO Eraser

• Generator / oscillator on a microstrip board generates a vertically polarized wave
• The wave travels down the microstrip to 2 vertically polarized antennas at the edge of the board spaced strategically to give conveniently spaced interference pattern
• Each antenna output next encounters a polarizer oriented at 45 degrees to vertical.
• In RF speak we say that the RF wave is re-radiated from the polarizers. 1/2 of the wave is transmitted and 1/2 is reflected at each polarizer
• The 2 separate streams are now in orthogonal polarizations.  Thus I assume they will not be able to interfer with one another at the screen.
• The non-interfering pattern is seen on the screen
• A total power loss of 1/2 is seen,

With Eraser

• Generator / oscillator on a microstrip board generates a vertically polarized wave
• The wave travels down the microstrip to 2 vertically polarized antennas at the edge of the board spaced strategically to give conveniently spaced interference pattern
• Each antenna output next encounters a polarizer oriented at 45 degrees to vertical.
• In RF speak we say that the RF wave is re-radiated from the polarizers. 1/2 of the wave is transmitted and 1/2 is reflected at each polarizer
• The 2 separate streams are now in orthogonal polarizations.  Thus I assume they will not be able to interfer with one another at the screen if left as is.
• ERASURE:  The 2 separate streams encounter the vertical polarizer.  The RF wave is re-radiated from the polarizer with 1/2 going back toward the generator and 1/2 going to the screen.  The polarization of stream 1 and 2 are now aligned and thus complete constructive and destructive interference is possible.
• The interfering pattern is seen on the screen.
• A total power loss of 1/4 is seen due to each passing through 2 polarizer stages each oriented at 45 degrees to the stream.

Observation

It is easy to see why there is no interference in the first case.  We have arranged for each path to be in orthogonal polarization states. They can not interfere when orthogonal.

### RF over Fiber

Sunday, February 2nd, 2014

RF over fiber is where you modulate an RF signal onto the light beam and thus transmit it at a lower loss over a long distance.  It is an analog usage as opposed to a digital one as used in data transmission such as an ethernet extender. I have found some equipment for doing this but have not yet found anything that appears it will do the full Internet + Cable TV solution to extend the pole to internet modem solution that is cheap enough to use.

Conclusions

For now this is not a viable solution to the house in the forest long internet cable extension problem.  It will probably get there soon though.

### Smith Chart Q FootBalls

Sunday, October 20th, 2013

If you plot a curve of constant ratio of Impedance / Resistance you will see that they plot out football shaped areas on the Smith Chart. See below:

If you are attempting to design the widest band match possible then do not violate the initial footbal in which your load impedance falls.

### The HP Half Wave 50 ohm transmission line trick

Sunday, October 20th, 2013

If your 50 ohm microstrip transmission line varies somewhat in impedance when you are connecting 2 50 Ohm elements together you can use a 1/2 wave length of line in between the blocks if space is available and the design is narrow band. What will happen in a full spin around the Smith chart bringing the load end of the transmission line back to where is started at feed end.

### Using WinSmith Program to Design Matching Circuit of 900MHz ISM Band Power Amplifier

Sunday, October 20th, 2013

WinSmith is a Smith chart match calculating program.  The starting point is 8 – j16 ohms @ 915MHz.  Both the blue and the green curves start at this point at the lower left of the curves.  Click on the image to see a bigger version

What is interesting about the above plot is that the elements work orthogonally.  That is to say for any point selected by component of move #2 or move #3 work independently.

The matching circuit is shown below:

Nominal values

• TL1:  45 degrees of 50 Ohm transmission line @ 900MHz
• C2:   25pF
• C1:   7pF

The left side is 50 Ohms match and the right side is what presents a conjugate match to the FET IC drain circuit.  Move #1 on the Smith chart is the 45 degrees of 50 Ohm characteristic impedance transmission line.

Tuning Procedure- theoretical

• The output load of the FET MMIC amplifier will vary somewhat.  In spite of this the 45 degrees will transform the load to a region in the charge where the two caps can move the load to the close to the center of the chart.
• C2 has one job only:  move the load to a 0.02 conductance circle on the Smith chart.  This is the conductance circle that corresponds to 50 Ohms in shunt.  Once you know the value of this capacitor you solder in place and leave it.
• C1 is used in shunt to bring the whole thing to the center of the chart.  A calculated value can be used for a first try.  You may need to cut and try to get absolute optimum on your lab model.

Input Match

The input match is the same topology.  It starts much closer to 50 Ohms.  The nominal values are

• TL1: 60 degrees of 50 Ohm line at 900MHz
• C2: 22pF
• C1: 0.5pF – This is placeholder in case of surprises.  The match looks accomplished without it.