The Use of Radio Spectrum. Welcome to. Where is radio used? Compare: Basic Wireless Communication Technique ETIF05. Göran Jönsson

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1 Welcome to Basic Wireless Communication Technique The Use of adio Spectrum ETIF05 EIT Göran Jönsson Electrical and Information Technology EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 3 Where is radio used? Compare: Low frequency electronics adio frequency electronics EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 2 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 4

2 Overview bandwidth information bandwidth channel bandwidth modulation multiplexing frequency time code dynamic noise interference compression distortion intermodulation selectivity frequency stability 8 10 Schedule Monday Tuesday Wednesday Thursday Friday lunch Exercise 13 hour 15 Lecture Exercise hour Lect/ Exerc Exerc oratory exercises at three occasions in Sept/Oct Booking of time is possible from Tuesday September 6 at the course home page EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 5 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 7 Basic Wireless Communication Technique ETIF05 Contents Electrical and Information Technology 1. Introduction, bandwidth, decibel, noise 2. eceiver principles, F amplifiers, intercept- and compression point, mixers, oscillators 3. Mixers, oscillators, PLL, frequency synthesizers 4. Analogue modulation, amplitude-, frequency- and phase modulation, modulation gain 5. F measurements, spectrum analyser, transmission lines 6. Transmission lines, Smith chart, vector network analyser 7. Digital modulation 8. Antennas, wave propagation, link budget 9. Cellular and broadcast radio systems EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 6 The course home page: EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 8

3 Literature esonant Circuits Parallel circuits are handled by summing the admittances Y 1 tot L C Parallel resonance Y tot ( ω) jωl + jωc 1 + j ωc 1 % ( $ ωl ' SEK 340 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 9 esonant frequency: C 1 L 0 f 0 1 2π 1 LC EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 11 esonant Circuits Series circuits are handled by summing the impedances C L tot Series resonance Bandwidth The 3dB-bandwidth is defined as the frequency range where the circuit impedance or admittance has changed 3 db. Z Series circuit Z Parallel circuit 3 db Z tot ( ω) + jωl + 1 jωc + j ωl 1 % ( $ ωc ' The frequency that leaves a purely resistive impedance is called the resonant frequency: L 1 C 0 f 1 0 2π 1 LC f 1 f 0 f 2 B 3dB 3 db f f 1 f 0 f 2 B 3dB f EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 10 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 12

4 db is a relative measure in logarithmic scale Decibel x [ db] 10 log( ratio) 10 log dbm, dbw are power units related to fixed references: 0 dbm 1 mw in 50Ω P [ dbm] 10 log$ P [ mw] 1[ mw] P [ dbw] 10 log$ P[ W ] % 0 dbw 1 W in 50Ω ' 1[ W ] dbv is a voltage unit but: Since the relation between power-voltage-current is the corresponding db-quantity for voltage or current will be P V 2 V dbv EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 13 % ' [ ] I 2 W [ ] 10 logv 2 20 logv [ V]! y linear y reference $ % Decibel Conversion between db and linear values: linear è db db è linear db is easy to calculate multiplication in linear become add in log division in linear become subtraction in log [ ] 10 log x db y linear y reference a b [ linear] a + b [ db] a b linear [ ] a b db [ ] EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 15! y linear y reference 10 x[ db] 10 $ % Linear scale provides poor dynamic: 1 : 85 Logarithmic scale provides excellent dynamic: 80 db : Linear or logarithmic scale? Q 2π Circuit Q - quality factor maximum energy stored in the circuit energy dissipated per cycle is a measure of the maximum instantaneous stored energy related to the total energy dissipated in the circuit is non-dimensional is called Q-värde or godhetstal in Swedish is also used for none-electric systems is also applicable to non-resonant circuits such as C-circuit or individual components such as a coil is equal to the ratio between the resonance frequency and the 3 db bandwidth: EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 14 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 16

5 Circuit Q Thermal Noise Series circuit Q Q X s L s s Parallel circuit Q 1 s C s s C s L s All resistors produces noise at: constant power at all frequencies white noise power that only depends on the temperature Q p X p C p p p L p C p L p EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 17 EIT Basic Wireless Communication Technique - ETIF05 - Lecture Quality factor - some comparisons Q Balls F inductors Piano string Cathedral bells Good quality capacitors Air vacuum capacitors Ordinary quartz vibrators Pendulum (grandfather clock) Pendulum (vacuum) Earth Spectral lines EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 18 Maximum available noise power: white noise constant spectral density at room temperature Thermal Noise if the equivalent noise bandwidth in the system is B eq the noise power is: N 0th kt! W Hz $ k Bolzmann's constant 1, T absolute temperature [K] N 0th W % $ Hz 174 dbm/hz N th ktb eq [ W] B eq noise bandwidth EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 20

6 Noise Bandwidth Noise model for semi-conductor power actual filter ideal rectangular filter N th ktb eq [ W] equal areas Noisy diode IDC Ii n noisefree r d the noise from a P-N-junction is called shot noise (hagelbrus in swedish) white noise the noise current depends on the DC bias current: i n 2qI DC B eq q charge of the electron 1, C B eq equivalent noise bandwidth B eq Equivalent noise bandwidth frequency r d is the diode dynamic resistance: kt q r d I DC T T 0 290K I DC! V$ A% EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 21 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 23 Noise model for the resistor Addition of Noise Sources Noisy resistor Ee n noisefree Maximum noise power is developed in a matched load: Ee n e n 2 Independent noise sources are added up as square sum: 2 e ntot e 2 n1 + e 2 n2 + e 2 n3 +! N th E $ n 1 2 % ktb 2 E n 4kTB EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 22 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 24

7 Addition of Noise Sources Noise Temperature If all the resistors in a network are at equal noise temperature Pierce rule is applicable: eq A device* with the noise ratio N N 1+ T eq T 0 T eq ( N 1) T 0 [ K] * amplifier, attenuator, filter, cable etc 2 e ntot 4kTB eq 4kTB (( ) / / 3 ) An antenna with the noise ratio N ant T ant N ant T 0 [ K] EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 25 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 27 Noise atio Noise atio (S/N) in T o Noi T eq G B (S/N) out For a passive attenuator at room temperature T 0 the noise ratio is equal to the attenuation L :! S $ N % N! S $ N % in out S in kt 0 B S in G ( kt 0 + kt eq ) BG 1+ T eq T 0 N 1+ T a $ T 0 % ( L 1) ' L Ta T0 NF [ db] 10log N The English notation is» N (Noise atio) in linear scale (times)» NF (Noise Figure) in logarithmic scale (db) In Swedish the letter F is used for both quantities hence NF [ db] L [ db] EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 26 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 28

8 Friis formula Stage 1 Stage 2 Stage 3 SINAD measurement an alternative method for measuring signal quality G 3 N 1 N 2 N 3 SINAD signal + noise+ distortion noise + distortion! signal + noise+ distortion $ 20log db noise + distortion % [ ] N N N 1 + N N Friis formula shows that the first stage should be designed for: lowest possible noise ratio maximum possible gain Note: only linear quantities may be used SME F OUT modulated signal DUT f m Log Log + Σ SINAD EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 29 EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 31 An exemple: Installation of an antenna amplifier Case 1 Case 2 Case 3 Noise Figure Measurement Cable 30m L 1 17dB N 1 L 1 NF 2 3dB Cable 30m L 1 17dB N 1 L 1 Amplifier G 20dB NF 2 2dB NF 3 3dB Amplifier G 20dB NF 1 2dB Cable 30m L 2 17dB N 2 L 2 NF 3 3dB ( S N N ) in S N 1+ T eq ( ) T 0 ut What s the size of the total noise figure? Convert into linear quantities and use Friis formula: N tot N 1 + N N N 1 50 N 2 2 N 1 50 N 2 1,6 N 3 2 N 1 1,6 N 2 50 N 3 2 N tot NF tot 20dB 1,6 1 N tot ,5 80,5 NF tot 19dB Which is the best solution? 50 1 N tot 1, ,6 + 0, ,5 2,59 NF tot 4,1dB EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 30 T s NOISE SC DUT T eq,g EIT Basic Wireless Communication Technique - ETIF05 - Lecture 1 32 F IN N 0 k ( T eq +T s )G