Wireless: More Chapter 4

Nov 4th-9th IETF is hosting a meeting in Atlanta GA.  He's pushing for people to go at least for one day and trying to see if the student group will be able to help pay for it.

Not too much digression at the beginning of class today, so notes after the jump.

**Please note, for some reason I cannot add pictures to these anymore.  If you need to see the pictures, please see the slideshows until I can get this fixed.**

Log Periodic Antenna

Wireless: More Ch 4

Jerry's been yakkin quite a bit.  Showed us some different types of antennas in class.

Reviewed pictures/graphs showing filters and what is blocked. 

Wavelength (meters)( λ) = 300/F MHz - remember this, it'll be on the test and used.  

Extra Credit ops-              Ham Fest in Severville 9/29 50points

                                        LOPSA meeting 10/2 30points

Digressions links, unsure where they fit in, but looks important.
Dipole Antennas

Cell Phone Booster

Notes from class (such as it is) after the break.

Wireless: Ch 4 cont.

Short one today, as we had a test and Jerry talked quite a bit on unrelated stuff.  Also, sorry about the format, the keyboard I had was sticky and I could not type well, I had to copy/paste from the powerpoint slides. 

Antenna Characteristics

Types, sizes and shapes

Passive antennas

–The most common type

–Constructed of a piece of metal, wire, or similar conductive material

–Does not amplify the signal in any way

–Directional gain

•Passive antennas radiate the RF energy supplied by the transmitter in one direction

•Exhibits an effective gain that is similar to amplification of the signal

Wireless: Start of Ch 4

Supplemental notes for the review of Ch 3. 

High pass aka low cut

Low pass aka high cut

The spike or raised area on any graph shows the BLOCKED frequencies.

Chapter 4 start

Gain and Loss

Understanding RF signal transmission involves the strength or power with which the transmitter is sending out the signal, the amount of reduction in signal strength caused by cables, connectors, and other components, the transmission medium and the minimum strength of the signal required by the receiver to be able to properl recover the data sent by the transmitter. 

An amplifier boosts the power of a signal, called a gain.  Cables and connectors offer a resistance to the flow of electricity and tend to decrease the power of a signal (loss).  Signal power changes logarithmically and gains and loss are relative concepts.  You need to know the power level of the signal at two different points. 

Wireless Ch 3 cont

Signal Strength cont.

 

Directional Antenna is used to minimize multipath distortion and radiates electromagnetic waves in one direction only.

There are other methods to reduce multipath distortion; using an amplifier in front of receiver to increase SNR and transmitting the same signal on separate frequencies.

Wireless: Chapter 3, Radio Communications

Filters removes unwanted F signals.  RF filter either passes or rejects a signal based on frequency.  There are three basic types of filters; low-pass, high-pass and bandpass filters.  Low pass blocks the high, lets the low through, high blocks low and keeps high.  The bandpass sets a range called a passband, which has a min and max threshold.  

Wireless: End of Chapter 2

Went over audio stuff, sample size and rate.  Not sure what this has to do with chapter 2….

Digital Modulation Cont.

-Binary signals are digital data transmissions are typically sent in bursts of bits.  There are three types of binary signaling techniques that can be used:

Return-to-zero (RZ) calls for the signal to rise to represent 1 bit.  It must return to zero in its allotted time.

Non-return-to-zero (NRZ) the voltage signal remains positive, or high, for the entire length of the bit period.

Polar non-return-to-zero (polar NRZ) raises the signal to represent a 1 bit, but drops to a negative amount to represent a 0 bit.  Works well with light by using different colors.

A variation on a non-return-to-zero-level is a non-return-to-zero, invert-on-ones (NRZ-I).  A change in voltage level represents a 1 bit, whereas no change in voltage level indicates that the next bit is a 0. 

 The rising edge is on the left of the pulse, the falling edge is on the right.  The top is the level edge of the pulse.  

More After the Break

Wireless: Data Transmission

We are using Wireless# Guide to Wireless Communications by Jorge Olenwa and Mark Ciampa.  The pictures on here are screen clippings from either the book or the power points that my instructor is using. 

This first post is two classes combined. 

Chapter 2- Wireless Data Transmission

Notes and stuff after the break