Transmission Lines, Antenna Systems, and Design PDF

TRANSMISSION LINE, ANTENNA SYSTEM and DESIGN **Transmission Line** is a form of bounded channel that is used to propagate the signal from one point to another. Two major FACTORS THAT DETERMINE THE RESPONSE OF THE TRANSMISSION LINE - **Frequency** of the signal - **Length** of the transmissio...

TRANSMISSION LINE, ANTENNA SYSTEM and DESIGN **Transmission Line** is a form of bounded channel that is used to propagate the signal from one point to another. Two major FACTORS THAT DETERMINE THE RESPONSE OF THE TRANSMISSION LINE - **Frequency** of the signal - **Length** of the transmission NOTE: In general, a [conductor is considered as a transmission line] if its length exceeds one sixteenth (1/16) of the signal wavelength CATEGORIES OF MEDIA 1. **Unbounded Media** - a type of media where signal is propagated and transmitted elsewhere - cost-effective - Example: space, vacuum, sea 2. **Bounded Media** - a type of media where signal is propagated and transmitted within a bounded and enclosed medium - Example: transmission line, fiber optics, waveguides **Transmission Line** is characterized by a metallic conductor system that is used to [transfer electrical energy] [from one point to another]. Some examples of it are UTP, coaxial cable, fiber optic cable, waveguide, etc. **TYPES OF TRANSMISSION LINE** 1. **Balance Line** - Types of transmission line where signals are present on both wires with [equal magnitudes but travel in opposite directions or opposite in line.] - Both conductors carry current - Example: UTP, STP, twin lead, parallel line, parallel open line 2. **Unbalance Line** - Type of transmission line where signals are present only on one line, other line of the [wire is in ground or grounded] - Example: coaxial cable or concentric lines **BETWEEN UTP AND STP, WHICH IS BETTER?** - UTP is cost efficient; easy installation - STP is noise and interference immunity, has shield hard to install **Problem 1: Can a one balance and unbalance line connect w/ each other?** Yes. But inde maganda, so u should use... **Balun -** a special type of transformer used to match the balanced line and unbalanced line; a mediator between the two differences to work. **TYPES OF TRANSMISSION LINE** **BALANCED LINE** 1. **Two-Wire Open Line** - Consists of two wires generally spaced from 2 to 6 inches apart by insulating spacers - Characterized by [high radiation losses] and is susceptible to noise - Normally operated in balanced mode May kinalaman ba spacing like 2 inches and 6 inches? Where? **Ans:** in terms of signal propagation kasi it has something to do w/ impedance -\> losses, and a function of dielectric constant 2. **Twin Lead** - Also called as "two wire ribbon" and "the ribbon cable" - It [differs from a parallel open transmission] line because of the separation made of polyethylene dielectric materials (plastic) - Typical conductor separation is 5/16 inch - Commonly used insulators are Teflon and PE 3. **Twisted Pair** - Formed by two lines or insulated wires twisted together to form a flexible line without the use of spacers - Amount of twisting reduces the [interference] within the line - [It is not used for high frequencies] - Example: UTP and STP are the most common type - Interference is specifically known as [cross talk] 4. **Shielded Pair** - Expensive type of due to its construction (becoz of "additional element") - The two wire is separated by insulation and additional strength member like braided wire and polyethylene jacket - Note: **[Shielding]** protects the transmission line from interferences - Consists of parallel conductors separated and surrounded by a solid dielectric - The copper braid isolates the inner conductor from interference and noise. Note: The conductors are balanced to ground. UNBALANCED LINE 1. **COAXIAL CABLE** - consists of two concentric conductors separated by a dielectric - outer conductor copper or aluminum tube or wire braid - inner conductor wire or small tube - the dielectric may be air, plastic, or ceramic - Coaxial cables are used extensively for high frequency applications - Limited to unbalanced applications TWO TYPES OF COAXIAL CABLE - Rigid or Air-Filled Coaxial Line - Flexible or Solid Coaxial Line NOTE: Both are relatively immune to external radiation and can propagate at higher frequencies than parallel wire line. a. **RIGID COAXIAL LINE (AIR-FILLED)** - uses air as dielectric between the inner conductors and house tubular structure - insulators are usually spacers are made of pyrex or polysterene; located at regular intervals that insulate the inner from the outer conductor  b. **SOLID COAXIAL LINE (FLEXIBLE)** - The inner conductor is separated by dielectric materials usually made from polyethylene. The dielectric material of the coaxial line is suitable to lower the radiation lost at high frequency operation - inner conductor consists of flexible wire insulated from the outer conductor by a solid continuous insulating material - insulator is usually polyethylene or teflon - Flexibility may be gained if the outer conductor is made of braided wire CHARACTERISTICS OF A TRANSMISSION LINE: 1. **ELECTRICAL PROPERTIES** - Conductivity of the conductor - Dielectric constant of the insulator 2. **PHYSICAL PROPERTIES** - Wire diameter - Conductor separation