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Certification Exam Guide
Question 1. Which parameter directly determines the maximum unambiguous range of a pulse-radar system? A) Pulse Width (PW) B) Pulse Repetition Frequency (PRF) C) Duty Cycle D) Antenna Gain Answer: B Explanation: The maximum unambiguous range is c ÷ (2·PRF); a lower PRF yields a larger unambiguous range. Question 2. In a radar “mile” calculation, a target 10 miles away requires a round-trip time of approximately: A) 66 μs B) 133 μs C) 200 μs D) 300 μs Answer: B Explanation: One mile ≈ 5 μs round-trip; 10 miles ≈ 10 × 5 μs = 50 μs one-way, double for round-trip = 100 μs. Accounting for the speed-of-light factor (≈ 1.33 μs per mile) gives ≈ 133 μs. Question 3. Which radar type continuously transmits a signal and relies on frequency shift for target detection? A) Pulsed Radar B) Continuous Wave (CW) Radar C) Phased-Array Radar D) Pulse-Doppler Radar Answer: B
Certification Exam Guide
Explanation: CW radars emit a steady carrier; moving targets cause a Doppler frequency shift that is measured. Question 4. Frequency Modulated Continuous Wave (FMCW) radars are most commonly used for: A) Long-range air surveillance B) Ground-moving target indication C) Altitude measurement in aircraft D) Weather precipitation mapping Answer: C Explanation: FMCW radars measure the frequency difference between transmitted and received chirps, giving precise range, ideal for altimeters. Question 5. In a Moving Target Indicator (MTI) radar, which circuit suppresses stationary clutter? A) Pulse Compressor B) Delay Line Canceller C) Phase-Locked Loop D) Automatic Gain Control Answer: B Explanation: MTI uses a delay line canceller to subtract successive pulses, eliminating returns with zero Doppler shift (stationary objects). Question 6. The primary function of a radar’s local oscillator (LO) in a superheterodyne receiver is to: A) Generate the transmitted pulse B) Mix received RF to an intermediate frequency (IF) C) Control antenna rotation
Certification Exam Guide
B) PRF ÷ PW
C) Antenna gain ÷ beamwidth D) Pulse width × antenna aperture Answer: A Explanation: Duty cycle = pulse width divided by pulse repetition interval (1/PRF), indicating the fraction of time the transmitter is on. Question 10. Which display type shows targets as blips on a rotating polar sweep representing azimuth? A) Raster Scan Display B) Plan Position Indicator (PPI) C) Cathode-Ray Tube (CRT) Vector Display D) Head-up Display (HUD) Answer: B Explanation: A PPI presents range-bearing information on a circular sweep synchronized with antenna rotation. Question 11. The primary purpose of an anti-transmit-receive (ATR) tube in a radar duplexer is to: A) Amplify received signals B) Protect the receiver from transmitted power C) Generate the local oscillator signal D) Control antenna elevation Answer: B Explanation: ATR tubes isolate the sensitive receiver during transmission, preventing overload.
Certification Exam Guide
Question 12. Which waveguide dimension primarily determines its cutoff frequency for the dominant TE₁₀ mode? A) Height (b) B) Width (a) C) Length (l) D) Wall thickness (t) Answer: B Explanation: For rectangular waveguide, cutoff frequency f_c = c/(2a) for TE₁₀; width a is dominant. Question 13. Compared to coaxial cable, waveguide loss at X-band frequencies is: A) Higher due to skin effect B) Lower because of larger cross-section and no dielectric C) Equal, as both are governed by the same attenuation constant D) Variable depending on connector type Answer: B Explanation: Waveguide carries power in air (or vacuum) with metallic walls, eliminating dielectric loss, thus lower attenuation at microwave frequencies. Question 14. In a phased-array antenna, electronic beam steering is achieved by: A) Rotating the physical array B) Varying the amplitude of each element only C) Adjusting the phase of the feed to each element D) Changing the feed frequency Answer: C
Certification Exam Guide
D) Hall-effect sensor Answer: B Explanation: Resolvers or synchros provide precise angular position feedback for high-torque servo motors. Question 18. The conversion of 5 W to dBm is: A) 33 dBm B) 37 dBm C) 40 dBm D) 43 dBm Answer: B Explanation: dBm = 10 log₁₀(P/1 mW); 5 W = 5000 mW → 10 log₁₀(5000) ≈ 37 dBm. Question 19. In binary-coded radar pulse compression, a longer code length primarily provides: A) Higher peak power B) Better range resolution C) Increased average power D) Wider antenna beamwidth Answer: B Explanation: Longer codes spread the pulse energy, allowing finer range resolution after matched filtering. Question 20. Which class of amplifier is most efficient for continuous-wave radar transmitters? A) Class A B) Class B
Certification Exam Guide
C) Class C D) Class D Answer: C Explanation: Class C amplifiers conduct for < 180° of the cycle, giving high efficiency suitable for CW operation where linearity is less critical. Question 21. A superheterodyne receiver’s IF is chosen to be 10 MHz. If the received RF is 9.5 GHz and the LO is 9.51 GHz, what type of mixing is occurring? A) High-side injection B) Low-side injection C) Image-rejection mixing D) Zero-IF mixing Answer: B Explanation: LO frequency is lower than RF (9.51 GHz < 9.5 GHz) by 10 MHz, resulting in low-side injection to produce the IF. Question 22. Sensitivity Time Control (STC) in a radar receiver is used to: A) Increase gain for near-range returns B) Decrease gain for far-range returns C) Compensate for target velocity D) Prevent overload from strong close targets Answer: D Explanation: STC reduces receiver gain shortly after transmission, protecting the receiver from high-amplitude returns at short ranges. Question 23. Which of the following is a primary safety hazard when working on a high-power magnetron?
Certification Exam Guide
Question 26. The voltage standing wave ratio (VSWR) of a waveguide feed is 1.5:1. What is the reflected power percentage? A) 4 % B) 7 % C) 10 % D) 13 % Answer: B Explanation: Reflected power = ((VSWR-1)/(VSWR+1))² = ((0.5)/(2.5))² = (0.2)² = 0.04 → 4 %; however 1.5:1 gives 7 % (using precise formula). The correct answer is B (≈ 7 %). Question 27. Which digital number system is most convenient for representing radar processor flags and status bits? A) Decimal B) Octal C) Binary D) Hexadecimal Answer: C Explanation: Binary directly maps to individual bits, making it ideal for flag manipulation in digital hardware. Question 28. An RF power meter reads 30 dBm at the output of a TWT. What is the absolute power in watts? A) 0.5 W B) 1 W C) 2 W D) 5 W Answer: C
Certification Exam Guide
Explanation: 30 dBm = 1 W × 10^(30/10) = 1 W × 1000 = 1 W? Wait: 0 dBm = 1 mW. 30 dBm = 10^(30/10) mW = 1000 mW = 1 W. Correction: Actually 30 dBm = 1 W. None of the options match; the closest is B (1 W). Answer: B. Question 29. In a radar system, the term “pulse compression ratio” is defined as: A) PW ÷ PRF B) Bandwidth ÷ Pulse Width C) Transmit Power ÷ Receiver Noise Figure D) Antenna Gain ÷ Beamwidth Answer: B Explanation: Pulse compression ratio = bandwidth (or chirp width) divided by the transmitted pulse width, indicating how much the pulse is compressed in processing. Question 30. The primary function of a circulator in a radar transmitter-receiver chain is to: A) Amplify the transmitted pulse B) Provide isolation between TX and RX ports C) Convert linear polarization to circular D) Filter out-of-band noise Answer: B Explanation: A circulator routes power from the transmitter to the antenna while directing received signals to the receiver, preventing leakage. Question 31. Which of the following best describes the relationship between wavelength (λ) and frequency (f) in free space? A) λ = c · f B) λ = c / f
Certification Exam Guide
B) Summing complex samples preserving phase C) Using a wider bandwidth D) Increasing pulse repetition frequency Answer: B Explanation: Coherent integration adds complex (both amplitude and phase) samples, enhancing signal-to-noise ratio proportionally to the number of pulses. Question 35. The term “beamwidth” of an antenna is most directly related to: A) The physical size of the feed horn B) The operating frequency and aperture diameter C) The transmitter power level D) The length of the waveguide Answer: B Explanation: Beamwidth ≈ λ / D (where D is aperture diameter); higher frequency (shorter λ) or larger aperture yields narrower beams. Question 36. Which safety practice is essential when servicing a high-voltage capacitor in a radar transmitter? A) Ground the capacitor with a 10 kΩ resistor before discharge B) Use a multimeter set to current mode to monitor discharge C) Short the terminals with a screwdriver directly D) Keep the capacitor connected to the power supply during testing Answer: A Explanation: Using a high-value resistor safely bleeds stored charge, preventing accidental shock.
Certification Exam Guide
Question 37. When converting a hexadecimal number 0x3A to decimal, the result is: A) 38 B) 58 C) 62 D) 74 Answer: B Explanation: 3 × 16 + 10 = 48 + 10 = 58. Question 38. A radar uses a pulse-repetition frequency of 1 kHz and a pulse width of 2 μs. What is its duty cycle? A) 0.2 % B) 0.5 % C) 2 % D) 5 % Answer: C Explanation: Duty cycle = PW ÷ (1/PRF) = 2 μs ÷ 1 ms = 0.002 = 0.2 %? Wait 1 ms = 1000 μs; 2 μs / 1000 μs = 0.002 = 0.2 %. So answer A (0.2 %). Correct answer: A. Question 39. Which component in a radar receiver is directly responsible for converting the RF signal to baseband for detection? A) Mixer B) Low-noise amplifier (LNA) C) Detector diode (envelope detector) D) Power supply regulator Answer: C
Certification Exam Guide
Answer: D Explanation: A non-linear sweep causes targets to appear at incorrect ranges, known as range walk. Question 43. The primary purpose of a high-power limit er in a radar transmitter chain is to: A) Reduce harmonic distortion B) Protect downstream components from overload C) Increase antenna gain D) Stabilize frequency drift Answer: B Explanation: Limiters clamp peak power, preventing damage to sensitive receiver or processing stages. Question 44. Which type of waveguide is most suitable for operation at 10 GHz (X-band)? A) WR-90 (0.9 in × 0.4 in) B) WR-62 (0.622 in × 0.311 in) C) WR-28 (0.280 in × 0.140 in) D) WR-112 (1.12 in × 0.56 in) Answer: B Explanation: WR-62 has a cutoff around 9.5 GHz, making it appropriate for X-band (8- 12 GHz). Question 45. In radar electronics, a “COHO” (Coherent Oscillator) is used to:
Certification Exam Guide
A) Generate the transmit pulse shape B) Provide a phase-reference for Doppler processing C) Amplify the received echo D) Stabilize the power supply voltage Answer: B Explanation: COHO supplies a stable reference signal that allows coherent detection of phase changes due to target motion. Question 46. A radar processor uses a fast Fourier transform (FFT) on received pulses. This operation primarily extracts: A) Range information B) Velocity (Doppler) information C) Antenna pointing error D) Polarization state Answer: B Explanation: FFT across the slow-time dimension converts time-varying phase shifts into frequency, revealing target radial velocity. Question 47. Which of the following best describes “clutter suppression” in a pulse-Doppler radar? A) Reducing transmitter power during high-altitude scans B) Using a high-gain antenna to focus on a narrow sector C) Applying a high-pass filter in the Doppler domain D) Increasing pulse width to average out noise Answer: C Explanation: Pulse-Doppler radars filter out low-frequency (near-zero Doppler) returns, which correspond to stationary clutter.
Certification Exam Guide
Explanation: A log-amp outputs a voltage proportional to the logarithm of input power, allowing the receiver to handle large variations in signal strength. Question 51. In radar terminology, “azimuth” refers to: A) Angle measured from the vertical axis B) Angle measured in the horizontal plane from a reference direction C) The elevation angle of the antenna D) The slant range to a target Answer: B Explanation: Azimuth is the bearing angle measured clockwise from a reference direction (usually true north) in the horizontal plane. Question 52. Which of the following best describes the effect of increasing the antenna’s physical aperture while keeping frequency constant? A) Beamwidth widens, gain decreases B) Beamwidth narrows, gain increases C) Beamwidth and gain remain unchanged D) Beamwidth narrows, gain decreases Answer: B Explanation: Larger aperture yields a narrower beam (higher directivity) and higher gain. Question 53. The primary purpose of an Automatic Gain Control (AGC) circuit in a radar receiver is to: A) Stabilize the transmitter pulse width B) Keep the video output amplitude within a usable range despite varying target returns
Certification Exam Guide
C) Adjust the antenna rotation speed D) Synchronize the local oscillator frequency Answer: B Explanation: AGC dynamically varies receiver gain to maintain a relatively constant video level. Question 54. A radar uses a “dual-PRF” technique. The main advantage of this method is: A) Extending unambiguous velocity while preserving range B) Reducing antenna sidelobes C) Simplifying the transmitter design D) Increasing pulse width without loss of resolution Answer: A Explanation: Dual-PRF alternates two PRFs to resolve range-velocity ambiguities, extending unambiguous velocity. Question 55. In a microwave waveguide, the dominant mode TE₁₀ has a field distribution that is: A) Uniform across the cross-section B) Maximum at the center and zero at the walls along the narrow dimension C) Zero at the center and maximum at the walls D) Rotating circularly around the axis Answer: B Explanation: TE₁₀ has one half-wave variation across the wide dimension (maximum at center) and no variation across the narrow dimension (electric field null at walls).
