electrics

Question 1

Types of wire antennas

Answer 1

Dipoles, loops and monopoles

Question 2

Types of aperture antennas

Answer 2

parabolic dish

Question 3

Types of array antennas

Answer 3

two or more antennas operating together

Question 4

wire antenna features

Answer 4

lower frequencies (<1Ghz), easy to build, low gain

Question 5

aperture antenna features

Answer 5

higher frequencies, high performance, high gain, point to point communication

Question 6

array antenna features

Answer 6

better performance and flexibility than single antennas

Question 7

isotropic radiation pattern

Answer 7

radiates equally in all directions (only theoretically possible)

Question 8

directional radiation pattern

Answer 8

radiates/receives more power in some directions

Question 9

omnidirectional radiation pattern

Answer 9

non-directional pattern in one plan and directional pattern at 90 degrees

Question 10

radiation density equation

Answer 10

Si = P / 4pi*r^2

Question 11

radiation intensity equation

Answer 11

U = P / 4pi

Question 12

directivity equation

Answer 12

D = 4pi*U / P

Question 13

gain equation

Answer 13

G = S4pir^2 / P(in) = DP(rad) / P(in) = 4pi / (delta)theta(delta)omega = 4pi*A / lambda^2

Question 14

effective isotropic radiated power equation

Answer 14

P(iso) = P(in)*G

Question 15

radiated power radius equation

Answer 15

R = 2D^2 / lambda

Question 16

gain to dBi equation

Answer 16

dBi = 10log10(D(max))

Question 17

maximum radiation density equation

Answer 17

Si(max) = PG(max) / 4pir^2

Question 18

antenna effective area equation

Answer 18

Ae = P / Si = G*lambda^2 / 4pi

Question 19

aperture efficiency equation

Answer 19

E(ap) = Ae / A

Question 20

radar power density equation

Answer 20

P(D) = P(t) / 4pi*r^2

Question 21

radar power rereadiated equation

Answer 21

P(D)sigma = P(t)G(t)sigma / 4pi*r^2

Question 22

radar power density back at radar equation

Answer 22

P(RD) = P(t)G(t)sigma / (4pir^2)^2

Question 23

radar received power equation

Answer 23

P(R) = P(t)G(t)G(r)*lambda^2 *sigma / (4pi)^3 * r^4

Question 24

radar signal-noise ratio equation

Answer 24

P(R) / N = P(t)G(t)G(r)sigmalambda^2*Ls / (4pi)^3 *r^4 * N

Question 25

pulsed radar features

Answer 25

transmits in pulsed radio frequency signals and receiver times how long it takes for the pulse to hit the target and return

Question 26

pulsed radar range equation

Answer 26

R = c*tau(D) / 2 (tau = 2RC)

Question 27

pulsed radar pulse width equation

Answer 27

tau <= 2*(delta)R / c

Question 28

pulsed radar range resolution equation

Answer 28

(delta)R = c*tau / 2 = c / 2B (B = bandwidth)

Question 29

pulse repetition frequency use

Answer 29

used when returning echo pulse time is greater than transmit pulse time to return from echo so ambiguity as to which is which (when t=2R / c > t = 1 / PRF)

Question 30

doppler frequency equation

Answer 30

f(D) = 2Vcos(theta) / lambda

Question 31

doppler rader Tx and Rx equation

Answer 31

Tx = cos(wot), Rx = Bcos(wdt)

Question 32

doppler resolution equation

Answer 32

1 / integration time

Question 33

surface clutter equation

Answer 33

sigma(0) = sigma(c) / A(c)

Question 34

doppler ground area equation

Answer 34

A(G) = R*(delta)phi*(delta)R

Question 35

wire antenna wavelength from length equation

Answer 35

L = wavelength / 2

Question 36

wire antenna current equation

Answer 36

I = Vs / Zg+Za

Question 37

radiation efficiency of antenna equation

Answer 37

eff = R(r) / R(r) + R(l)

Question 38

radiated power from normalised intensities

Answer 38

P(rad) = integral(2pi->0) integral(pi->0) of s(0) * sin^2(theta) * R^2 d(theta).d(omega)

Question 39

a larger beamwidth will

Answer 39

give faster scan coverage, fewer beam positions, poor angular resolution

Question 40

number of beam positions equation

Answer 40

N(B) = 2pi / (delta)ohms = 2pi / (delta)theta*(delta)omega

Question 41

dwell time equation

Answer 41

t / N(B)

Question 42

effective area of antenna equation

Answer 42

A = (D/2)^2 * pi*efficiency

Question 43

radar equation

Answer 43

R(max) = ( ( P(t)G^2 lambda^2 sigma) / ( (4pi)^3 P(min) ) )^1/4

Question 44

radar power density incident on target, radar power density collected by target

Answer 44

P(inc) = P(t)G(t) / 4pi*R^2, P(col) = P(t)G(t)*sigma / 4pi*r^2

Question 45

signal to jam ratio, when does burn through occur?

Answer 45

SJR = P(r) / P(r jam), burn through when SJR=1

Question 46

pulse repetition time equation

Answer 46

PRT = pulse-width / duty cycle

Question 47

pulse repetition frequency equation

Answer 47

PRF = 1 / PRT = c / 2R(max)

Question 48

average power equation

Answer 48

peak power * duty cycle

Question 49

number of hits equation

Answer 49

n = (delta)theta*PRF / 6*RPM

Question 50

max range equation

Answer 50

c / 2*PRF

Question 51

range resolution equation

Answer 51

c*tau / 2 (tau = pulse width/s)

Question 52

duty cycle equation

Answer 52

pulse duration / pulse repetition interval

Question 53

mean power

Answer 53

peak power * duty cycle

Question 54

(delta)theta

Answer 54

lambda / width*efficiency

Question 55

(delta)omega

Answer 55

lambda / height*efficiency

Question 56

axial ratio equation

Answer 56

AR = a / b

Question 57

doppler shift frequency equation

Answer 57

f(d) = 2Vcos(theta) / lambda