Wireless FundamentalsLesson 1

Bellevue Community College

Bob Young, Instructor

What is a radio wave?

• Voltage

• Current

• Sine Wave

• Phase Relationships

Radio Wave / RF Energy (a)

• FCC Frequency Allocations

• Radiation

• Propagation

• Path Loss (distance factors)

• Path Loss (environmental factors)

Radio Wave / RF Energy (b)

• Fading (multipath)

• Fading (Rayleigh)

• Fresnel Zone

• Wavelength

• Diversity Receivers

Fresnel Zone

Fresnel Zone

The formula for calculating the 1st Fresnel Zone is: _____________

F1 = 72.1 d2 / (f * D)

F1, = 1st Fresnel Zone radius in feet d = midway distance in miles f = frequency in GHz. D = total distance in miles between antennasThen the 0.6F = F1 x O.6

How big is the Fresnel zone?

For a 5 mile link using 915 MHz 60% of the first Fresnel zone at its widest point (middle of the path) is: 50.5627835662477 feet.

For a 5 mile link using 2.4 GHz 60% of the first Fresnel zone at its widest point (middle of the path) is: 31.220215806429 feet.

Properties of the Fresnel Zone

The higher the frequency –

The narrower the Fresnel zone.

Properties of the Fresnel Zone

The longer the path –

The wider the Fresnel zone.

4. Decibels• Power

• Voltage

• RF Applications

• Audio Applications

The Gain/Loss Formula

dB = 10Log10(Pout/Pin)

 

Converting dBto Gain Factor

GF =10(dB/10)

(Uses the 10x function on calculator) 

5a. Modulation

• Carrier (definition)

• Information (definition)

• Analog Modulation

• Amplitude Modulation (AM)

• Frequency Modulation (FM)

• Pulse Modulation (PM) (ICW)

5b. Amplitude Modulation

5c. Modulation

• Digital Modulation• Frequency Shift Keying (FSK)

• Phase Shift Keying (PSK)• Amplitude Shift Keying (ASK)

6. Transmitter

• Audio Processor

• Modulator

• RF Amplifier

7a. Receiver

• RF Amplifier (terminology note: misuse of term, “pre-amplifier”)

• Demodulator (Detector, Discriminator)

• Audio Processor

• Pre-emphasis and De-emphasis

7b. AM Receiver

8a. Interference

• Types of Interference

• Co-channel

• Adjacent Channel

• Intermodulation

8b. Interference

• Receiver Solutions to Interference

• Superheterodyne Receivers

• Image Frequency

• Dual Conversion Superheterodyne Receivers

8c. Interference

• Cavity and Filter Solutions to Interference• Bandpass Cavities• High Pass Filters• Low Pass Filters• Block Filters• Notch Reject Filters• LC Filters• Crystal Filters

9. Antennas

• Types

• Polarization

• Bandwidth

• Gain

10. Transmission Line

• Types

• Loss Characteristics

• Bending Radius

• Pressurized Transmission Line

10a. Other Devices

• Transmitter Combiner

• Receiver Multicoupler

• Splitter

• Duplexer

• Leaky Coax

• Bi-directional Amplifier (BDA)

• Isolator

11a. Applications & Principles

• Broadcast Radio

• Television

• Microwave Networks

• Satellite Communications

11b. Applications & Principles

• RADAR

• Wireless LAN, 802.11

• Trunked Radio Systems

• Wireless Data and Internet

• Telemetry