Radar Foundations, Terminology and Architectures

Introduction and Context

Radar—an acronym for radio detection and ranging—is an electromagnetic sensing technology used to detect objects, estimate their location and motion, and, in advanced systems, characterize their physical properties. Unlike optical and infrared sensors, radar can operate in darkness, fog, rain, dust, and smoke, although atmospheric effects become important at some frequencies and propagation conditions.

A radar system transmits electromagnetic energy, receives echoes scattered from objects, and processes those echoes to estimate target parameters. The most basic measurements are range, angle, and radial velocity. Modern radars may additionally estimate target size, shape, composition, micro-Doppler signature, and classification.

Radar engineering is inherently multidisciplinary. It combines electromagnetic propagation, antennas, microwave circuits, signal processing, probability, control, digital hardware, software, and systems engineering. A sound understanding of radar foundations is therefore essential before studying waveform design, detection theory, tracking, synthetic aperture radar, phased arrays, or multifunction systems.

Learning Objectives

After completing this chapter, the reader should be able to:

1. Describe the historical development and operating principle of radar.

2. Explain radar range, angular coordinates, Doppler frequency, and major terminology.

3. Distinguish monostatic, bistatic, and multistatic radar architectures.

4. Relate radar frequency bands to propagation, resolution, antenna size, and applications.

5. Interpret important radar performance measures.

6. Classify radar systems according to waveform, platform, function, and geometry.

7. Identify the major functional blocks in a radar system.

8. Analyze practical design trade-offs and governance issues in radar deployment.

1. Historical Development of Radar

The physical basis of radar is the reflection of electromagnetic waves. Heinrich Hertz demonstrated electromagnetic-wave reflection in the late nineteenth century, confirming predictions from Maxwell’s equations. Early twentieth-century experiments showed that radio signals could reveal the presence of ships and other large objects.

During the 1930s, several countries developed practical radio-location systems. The urgent requirements of air defence accelerated progress in pulsed transmitters, high-gain antennas, receivers, displays, and tracking methods. Magnetrons and klystrons enabled high-power operation at microwave frequencies, while improved receivers made weak echoes detectable.

After the Second World War, radar technology expanded into civil aviation, meteorology, maritime navigation, space surveillance, remote sensing, automotive safety, and industrial measurement. Solid-state power amplifiers, coherent oscillators, digital signal processors, electronically scanned arrays, active electronically scanned arrays, and software-defined architectures have progressively increased flexibility and reliability.

The historical lesson is that radar performance does not depend on one component alone. Improvements in antennas, transmitters, receivers, computation, signal processing, and operational doctrine must be integrated at the system level.

2. Fundamental Operating Principle

A basic pulsed radar performs four operations:

1. It generates and transmits a known electromagnetic waveform.

2. The waveform propagates through space and interacts with a target.

3. A portion of the energy is scattered back toward the radar.

4. The receiver and processor estimate target parameters from the returned signal.

For a target at distance R, the transmitted signal requires approximately R/c seconds to reach the target, where c is the propagation speed. The echo then requires another R/c seconds to return. Thus, the round-trip delay is

t = 2R/c

and the estimated range is

R = ct/2.

The factor of two applies to a monostatic radar, in which the transmitter and receiver are co-located and the outgoing and incoming paths have approximately equal length. The equation assumes propagation at approximately the speed of light and a target whose relevant scattering point is sufficiently well defined.

For a bistatic radar, the transmitter-to-target distance is R_T and the target-to-receiver distance is R_R. The measured delay gives the total path length:

R_T + R_R = ct.

A constant bistatic delay therefore corresponds to an ellipse in a two-dimensional plane, or an ellipsoid in three dimensions, with transmitter and receiver at the foci. It does not directly specify a single circular range from one site.

2.1 Radar Echoes and Scattering

A target intercepts only a small portion of the transmitted wave. The scattered energy depends on target size, shape, material, aspect angle, polarization, frequency, and the relationship between target dimensions and wavelength. The parameter used to represent equivalent scattering strength is radar cross section (RCS), denoted by σ and measured in square metres. RCS is not necessarily equal to the target’s physical projected area.

The received echo is usually much weaker than the transmitted signal. A simplified monostatic radar equation expresses the received power as

P_r = (P_t G^2 λ² σ) / [(4π)³ R⁴ L].

Here, P_t is transmitted power, G is antenna gain, λ is wavelength, σ is target RCS, R is target range, and L represents aggregate system losses. This form assumes a monostatic radar, far-field operation, a target adequately represented by an average RCS, matched polarization, and free-space propagation without severe multipath or clutter effects. The R⁴ dependence arises because the wave spreads on the outward path and the scattered wave spreads again on the return path.

For a bistatic radar, the range-dependent term is generally proportional to 1/(R_T²R_R²), while the transmitter and receiver antenna gains are evaluated in their respective target directions. Consequently, bistatic performance cannot be assessed by simply inserting a single radar-to-target range into the monostatic equation.

3. Radar Coordinates and Terminology

3.1 Range

Range is the distance between a radar reference point and a target, normally measured along the line joining them. In a pulsed radar, range is derived from delay. In a frequency-modulated continuous-wave radar, range may be derived from the frequency difference between transmitted and received signals.

The maximum unambiguous range of a conventional pulsed radar is related to the pulse repetition frequency (PRF):

R_u = c/(2 PRF).

This assumes one transmitted pulse per pulse-repetition interval and no additional waveform ambiguity resolution. If an echo from a previous pulse arrives after a later pulse has been transmitted, the radar may associate it with the wrong pulse and report an ambiguous range.

The approximate range resolution of a rectangular pulse is

ΔR ≈ cτ/2,

where τ is pulse duration. This describes the separation required for two isolated targets to produce distinguishable range responses under idealized conditions. Pulse compression permits a long transmitted pulse for energy efficiency while achieving a resolution related to the compressed bandwidth B:

ΔR ≈ c/(2B).

The bandwidth expression is an approximation whose precise resolution depends on waveform shape, processing criterion, signal-to-noise ratio, and sidelobe behavior.

3.2 Angular Coordinates

Radar direction is commonly expressed using azimuth and elevation. Azimuth is the horizontal angle relative to a reference direction, while elevation is the vertical angle relative to the horizontal plane. In a spherical coordinate description, a target may be represented as (R, azimuth, elevation).

The antenna beamwidth determines angular discrimination. A narrow beam improves angular resolution but normally requires a larger aperture, higher frequency, electronic beam steering, or some combination of these. Approximate beamwidth relationships depend on aperture shape. For a uniformly illuminated linear aperture of length D, the half-power beamwidth is of the order of λ/D radians, with the numerical coefficient determined by the exact definition and aperture illumination. This relationship should be used as a design scaling law rather than a universal exact formula.

A radar may determine angle using:

• mechanical rotation;
• sequential lobing or conical scan;
• monopulse amplitude comparison;
• monopulse phase comparison;
• multiple receive beams;
• interferometry; or
• digital beamforming.

3.3 Radial Velocity and Doppler Frequency

When a target has a velocity component along the radar line of sight, the received frequency is shifted. For a monostatic radar, the Doppler frequency is approximately

f_d = 2v_r/λ,

where v_r is radial velocity, positive or negative according to the adopted sign convention. The factor of two results from the outbound and inbound propagation effects.

For a bistatic radar, the Doppler shift depends on the bistatic geometry and the target velocity projected onto the transmitter-target and target-receiver directions. It is not generally equal to 2v_r/λ relative to either site alone.

Only the radial component is directly measured by a conventional Doppler observation. Tangential motion may produce little or no instantaneous Doppler shift, even though the target is moving rapidly.

3.4 Important Operational Terms

A pulse is a finite-duration burst of transmitted energy. Pulse repetition interval (PRI) is the time from the start of one pulse to the start of the next; PRF is its reciprocal. Duty cycle is the ratio of pulse duration to PRI for a simple pulsed waveform.

Clutter denotes unwanted echoes from terrain, buildings, sea surfaces, precipitation, vegetation, or other environmental features. Interference is unwanted electromagnetic energy, whether intentional or unintentional, that affects radar operation. Noise is random unwanted signal energy, often dominated by receiver thermal noise and external noise sources.

Detection is the decision that a target-like signal is present. Tracking is the recursive estimation of a target’s state, such as position and velocity, over time. Plot extraction converts detections into target reports. Data association determines which detections belong to which tracks.

A coherent radar preserves a stable phase relationship between transmitted and received signals, enabling Doppler processing and coherent integration. A non-coherent radar does not retain this phase information, although it can still measure range and signal amplitude.

4. Monostatic, Bistatic and Multistatic Architectures

4.1 Monostatic Radar

In a monostatic radar, the transmitter and receiver are located at the same site, or their separation is negligible relative to target distance. A shared antenna may be connected to the transmitter and receiver through a duplexer or circulator. Monostatic systems simplify synchronization, calibration, geometry, and deployment.

Their principal limitations include transmitter-receiver leakage, the need to protect sensitive receiver components from high transmit power, and the fact that the target is observed from one principal aspect. A monostatic system may also have difficulty detecting targets whose scattering is weak in the backscatter direction.

4.2 Bistatic Radar

A bistatic radar uses separated transmitter and receiver sites. Separation may be modest or comparable to the target range. The transmitter and receiver may be operated by one organization or may use an illuminator of opportunity, such as a broadcast or communications transmitter.

Bistatic geometry can provide different target observability, reduce direct transmitter-to-receiver coupling, and complicate an adversary’s assumptions about the sensing location. However, it requires accurate time and frequency synchronization, geometric calibration, communication links, and more complex processing. Bistatic range contours are ellipses or ellipsoids, and bistatic Doppler contours depend on geometry and velocity.

4.3 Multistatic Radar

A multistatic radar consists of multiple transmitting and/or receiving nodes whose measurements are combined. It can improve spatial coverage, provide diverse target aspects, support localization through measurement intersection, and increase resilience to single-site failure. The costs are networking, synchronization, data fusion, calibration, bandwidth management, and more demanding track association.

Architecture selection is therefore a systems decision. A multistatic design is not automatically superior: the benefits of geometric diversity must justify the added infrastructure and processing complexity.

5. Radar Frequency Bands

Radar frequency selection affects wavelength, antenna dimensions, atmospheric attenuation, target scattering, available bandwidth, component technology, and regulatory constraints. Common conventional designations include:

| Band | Approximate frequency range | Representative uses |

|---|---:|---|

| HF | 3–30 MHz | Over-the-horizon and ionospheric applications |

| VHF | 30–300 MHz | Long-range surveillance and large-array systems |

| UHF | 300 MHz–1 GHz | Surveillance and space-related applications |

| L | 1–2 GHz | Long-range surveillance, air traffic control |

| S | 2–4 GHz | Weather radar, surveillance, maritime systems |

| C | 4–8 GHz | Weather, tracking, remote sensing |

| X | 8–12 GHz | Fire control, imaging, marine and automotive radar |

| Ku | 12–18 GHz | Tracking, altimetry, imaging |

| K | 18–27 GHz | Short-range sensing and specialized systems |

| Ka | 27–40 GHz | High-resolution sensing and automotive radar |

| W | 75–110 GHz | Very high-resolution short-range applications |

These boundaries are conventional and may vary slightly among standards and industries. Higher frequencies generally permit greater bandwidth and smaller antennas for a given beamwidth, but atmospheric absorption and precipitation attenuation may increase. Lower frequencies can support longer propagation in some environments and may interact strongly with large targets, but require larger apertures for narrow beams.

Frequency does not by itself determine performance. Antenna aperture, transmitted energy, waveform bandwidth, receiver noise figure, processing gain, clutter, propagation, and deployment geometry are equally important.

6. Radar Performance Measures

Radar performance must be specified statistically because noise, clutter, target fluctuation, and environmental conditions vary. Important measures include the following.

6.1 Detection Range and Probability of Detection

Probability of detection, P_D, is the probability that the radar declares a target when the target is present under specified conditions. Probability of false alarm, P_FA, is the probability that the radar declares a target when no target is present. A useful radar must achieve an acceptable P_D while controlling P_FA.

Detection range depends on transmit power, antenna gain, wavelength, RCS, losses, receiver noise, bandwidth, integration, clutter, waveform, and detection threshold. A quoted maximum range is meaningful only when the assumed target, P_D, P_FA, environment, and operating mode are stated.

6.2 Resolution and Accuracy

Resolution is the ability to distinguish two closely spaced targets. Range resolution is primarily related to signal bandwidth; angular resolution is related to aperture and wavelength; Doppler resolution is related to coherent observation time and processing.

Accuracy is the closeness of an estimate to the true value. Resolution and accuracy are distinct. A radar may resolve two targets poorly but estimate a single isolated target accurately, or resolve targets well while suffering from systematic calibration bias.

6.3 Coverage and Availability

Coverage includes spatial region, altitude, range, angular sector, and temporal revisit. Availability is the proportion of time the system can perform its intended function. Mechanical failure, weather, electromagnetic interference, maintenance, power limitations, and software faults reduce availability.

6.4 Update Rate, Track Quality and Capacity

Update rate is the frequency with which measurements or track estimates are produced. Track quality includes position uncertainty, velocity uncertainty, continuity, and latency. Track capacity is the number of targets that can be detected, tracked, classified, and reported while meeting specified performance levels.

A radar with excellent single-target sensitivity may nevertheless be unsuitable for a dense environment if its scan time, processor capacity, data links, or track management cannot support the required target load.

7. Radar Classifications

Radar systems may be classified along several independent dimensions.

7.1 By Waveform

Pulsed radar transmits discrete pulses and measures delay. Continuous-wave radar transmits continuously and is especially useful for velocity measurement, but a simple continuous-wave system cannot determine range without modulation or additional spatial information. Frequency-modulated continuous-wave radar estimates range from frequency differences generated by known modulation.

Pulse-Doppler radar uses pulsed waveforms and coherent processing to distinguish moving targets from clutter. Pulse-compression radar transmits a waveform of relatively long duration and large bandwidth, then compresses it in the receiver to obtain high range resolution with substantial energy.

7.2 By Function

Surveillance radar searches a volume or area and provides detection and tracking over broad coverage. Acquisition radar initiates target information for another system. Tracking radar concentrates resources on one or more known targets. Fire-control radar supports precise engagement or guidance functions. Weather radar measures precipitation and atmospheric motion. Imaging radar forms spatially detailed representations, while altimeters measure height above a surface.

7.3 By Platform

Ground-based, shipborne, airborne, spaceborne, automotive, handheld, and distributed radars have different constraints. Platform motion, available power, vibration, antenna size, cooling, electromagnetic compatibility, and maintenance access strongly influence design.

7.4 By Beam Steering

Mechanically scanned radars rotate or move an antenna. Electronically scanned arrays change the beam direction by controlling the phase or time delay of many radiating elements. Active electronically scanned arrays use distributed transmit-receive modules, enabling rapid steering, multiple beams, graceful degradation, and waveform agility, but at greater cost and thermal-management complexity.

8. Major Functional Blocks of a Radar

A generalized radar architecture contains the following blocks:

1. Timing and synchronization: establishes pulse timing, coherent references, and coordination among subsystems.

2. Waveform generator and exciter: creates the desired frequency, phase, modulation, coding, and pulse timing.

3. Power amplifier or transmitter: raises the waveform to the required power while maintaining spectral and phase requirements.

4. Duplexer, circulator or transmit-receive switch: connects a shared antenna while protecting the receiver during transmission.

5. Antenna and beam-forming network: radiates energy and collects echoes, with mechanical or electronic steering.

6. Low-noise receiver front end: filters, amplifies, and downconverts weak signals while minimizing added noise.

7. Reference oscillator and local oscillator: provide frequency conversion and, in coherent systems, phase stability.

8. Analog-to-digital converter: samples the conditioned signal at a rate and resolution appropriate to its bandwidth and dynamic range.

9. Digital signal processor: performs pulse compression, filtering, Doppler processing, clutter suppression, beamforming, and calibration.

10. Detection processor: compares processed measurements with adaptive or fixed thresholds and produces detections.

11. Tracking and data-processing subsystem: associates detections, estimates target states, classifies objects, and manages tracks.

12. Display, interface and recorder: presents information to operators or external command-and-control systems.

13. Power, cooling, protection and built-in test: support safe, reliable operation and fault diagnosis.

The architecture is not strictly linear. Calibration data, environmental measurements, track feedback, adaptive waveform control, and resource management create closed-loop interactions. In a multifunction radar, scheduling algorithms allocate time, energy, beams, and processing resources among search, track, identification, communications, and imaging tasks.

9. Applied Case: Coastal Multistatic Surveillance

Background

The following is an illustrative engineering case. A coastal authority must monitor small vessels over a 40 km region containing islands, steep terrain, and heavy maritime traffic. A conventional shore-based monostatic radar experiences sea clutter and intermittent shadowing behind terrain.

Problem

The authority requires reliable detection of small vessels, a useful track update within operational limits, and continuity when one sensor is unavailable. It also wishes to reduce dependence on a single high-power transmitter.

Analysis

A single monostatic radar offers relatively simple calibration and processing but has a fixed viewpoint and blind regions caused by terrain. Small vessels may have low and fluctuating RCS, while sea clutter can be strong. A distributed architecture can provide spatial diversity: a target hidden from one site may be visible to another. However, the system must synchronize nodes, exchange measurements, and resolve track association.

Approach and Solution

The authority deploys one primary coastal radar and two receiving nodes at separated sites. The primary radar supplies a coherent reference and transmits a waveform selected for maritime detection. The remote receivers record direct and target-scattered signals, estimate bistatic measurements, and send time-stamped data to a fusion centre. The fusion processor uses a common geospatial coordinate system and combines monostatic and bistatic detections.

Calibration surveys establish node locations, antenna patterns, timing offsets, and frequency references. Adaptive clutter maps are maintained because sea clutter changes with wind, wave state, and antenna look direction. Track management assigns uncertainty regions to detections and uses motion consistency to associate measurements.

Outcome

The distributed system improves coverage in terrain-shadowed sectors and provides additional target aspects. It also introduces synchronization and communications as critical failure points. Performance is therefore evaluated not only by detection probability but also by end-to-end latency, node availability, false-track rate, calibration stability, and graceful degradation when a node is lost.

Learning Points

1. Geometry can be as important as transmitter power.

2. Bistatic measurements require specialized coordinate and Doppler models.

3. Distributed sensing shifts complexity from the RF front end to synchronization, networking, and data fusion.

4. System-level performance measures must include availability and maintainability.

10. Challenges, Governance and Contemporary Developments

Radar operation is affected by propagation anomalies, multipath, clutter, interference, target fluctuation, calibration drift, hardware aging, and cyber threats. Strong performance in a laboratory does not guarantee field performance. Test plans should include representative environmental conditions, controlled interference, edge-of-coverage operation, and failure modes.

Radar systems must comply with national and international spectrum regulations. Transmit frequencies, bandwidth, power, out-of-band emissions, and coexistence requirements are regulated to protect other users. Safety assessments are necessary where high-power electromagnetic fields may expose personnel or interfere with medical devices, aircraft systems, or explosive ordnance.

Surveillance radars also raise governance and privacy questions. Civil aviation, maritime, weather, and automotive applications may generate data about people, vehicles, or movements. Data retention, access control, auditability, proportionality, and lawful use should be addressed in system requirements rather than treated as afterthoughts.

Artificial intelligence and machine learning are increasingly applied to clutter classification, target recognition, anomaly detection, resource management, and track association. Their use must be bounded by validated datasets, robustness testing, uncertainty reporting, explainable decision support where appropriate, and human oversight for safety-critical decisions. Machine learning should complement—not conceal—limitations in sensing physics and data quality.

Contemporary radar development emphasizes digital arrays, gallium-nitride power amplifiers, cognitive and adaptive waveforms, passive and opportunistic sensing, networked multistatic operation, automotive millimetre-wave radar, joint radar-communications systems, and cloud or edge processing. These developments increase flexibility but also enlarge the attack surface, calibration burden, and verification challenge.

Best practice is to begin with a measurable operational need, define target and environment assumptions, select geometry and frequency jointly, quantify uncertainty, design for calibration and maintainability, and verify performance using independent test data. A radar should be evaluated as a complete sensing and decision system, not merely as a transmitter-receiver pair.

Chapter Summary

Radar detects and characterizes objects by transmitting electromagnetic energy and processing scattered returns. In monostatic pulsed radar, range follows from round-trip delay, R = ct/2; in bistatic systems, the measured path is the sum of transmitter-to-target and target-to-receiver distances. Range, angle, and radial velocity are fundamental observables, while RCS, clutter, noise, detection probability, false-alarm probability, resolution, accuracy, coverage, availability, and track capacity describe system performance.

Frequency selection creates trade-offs involving wavelength, antenna aperture, bandwidth, propagation, atmospheric loss, target scattering, and component technology. Monostatic architectures are comparatively simple, whereas bistatic and multistatic architectures offer geometric diversity at the cost of synchronization, calibration, communication, and fusion complexity. Radar systems may also be classified by waveform, function, platform, and beam steering.

The major functional chain includes timing, waveform generation, transmission, antenna and beamforming, receiver conversion, digitization, signal processing, detection, tracking, display, and support systems. Practical radar engineering requires attention to clutter, interference, environmental uncertainty, regulation, safety, privacy, cybersecurity, and responsible use of artificial intelligence. The central professional principle is systems thinking: radar capability emerges from the interaction of electromagnetic hardware, algorithms, geometry, operations, and governance.

Key Terms

Radar: A system that detects and characterizes objects using electromagnetic waves.

Range: Distance between a radar reference point and a target.

Azimuth: Horizontal angular direction of a target.

Elevation: Vertical angular direction of a target.

Monostatic radar: Radar with co-located or effectively co-located transmitter and receiver.

Bistatic radar: Radar with separated transmitter and receiver.

Multistatic radar: Radar using multiple spatially distributed transmitters and/or receivers.

Radar cross section: Equivalent measure of a target’s electromagnetic scattering strength.

Pulse repetition frequency: Number of transmitted pulses per second.

Pulse repetition interval: Time between corresponding points of successive pulses.

Range resolution: Ability to distinguish targets separated in range.

Doppler frequency: Frequency shift associated with target radial motion.

Clutter: Unwanted environmental or stationary echoes.

Probability of detection: Probability of declaring a target when it is present.

Probability of false alarm: Probability of declaring a target when it is absent.

Coherent radar: Radar that preserves usable phase relationships for processing.

Beamwidth: Angular width of an antenna radiation beam under a specified criterion.

Pulse compression: Processing that produces a narrow response from a longer, bandwidth-rich waveform.

Track: Time-sequenced estimate of a target’s state.

Digital beamforming: Formation and steering of antenna beams through digital signal processing.

Review Questions

Short Answer Questions

1. Why is the factor of two present in the monostatic pulsed-radar range equation?

2. Define radar cross section and explain why it is not simply physical target area.

3. Distinguish range resolution from range accuracy.

4. What is the function of a duplexer or circulator?

5. State two advantages and two challenges of multistatic radar.

Long Answer Questions

1. Explain the operating principle of a pulsed monostatic radar, from waveform generation to target tracking.

2. Discuss how radar frequency selection affects antenna design, propagation, resolution, and applications.

3. Compare monostatic and bistatic radar architectures, including their geometry, performance, and implementation requirements.

4. Describe the major functional blocks of a modern coherent radar and explain their interactions.

5. Explain radar performance measures including detection probability, false-alarm probability, resolution, accuracy, coverage, availability, and track capacity.

Analytical / Application Questions

1. A pulsed monostatic radar receives an echo 200 μs after transmission. Assuming propagation at 3 × 10^8 m/s and negligible processing delay, calculate the target range.

2. A radar operates at 10 GHz and observes a target with radial velocity 150 m/s. Using c = 3 × 10^8 m/s, calculate the approximate monostatic Doppler frequency and state the sign convention required to interpret it.

3. An organization must monitor a cluttered coastal region with terrain shadowing and wants resilience to a single-site failure. Recommend either a monostatic, bistatic, or multistatic architecture and justify the choice, including at least three implementation risks.

Multiple Choice Questions with Answers

Question 1

For a monostatic pulsed radar, an echo delay of 100 μs corresponds approximately to what range?

A. 1.5 km

B. 15 km

C. 30 km

D. 150 km

Correct Answer: B. 15 km

Question 2

Which parameter primarily determines idealized pulse-compression range resolution?

A. Carrier phase only

B. Antenna rotation rate

C. Waveform bandwidth

D. Target tangential velocity

Correct Answer: C. Waveform bandwidth

Question 3

In a bistatic radar, a constant measured delay generally defines a

A. circle centered on the receiver

B. sphere centered on the transmitter

C. line parallel to the baseline

D. ellipse or ellipsoid with transmitter and receiver at the foci

Correct Answer: D. ellipse or ellipsoid with transmitter and receiver at the foci

Question 4

For a monostatic radar, the approximate Doppler frequency is

A. v_r/λ

B. 2v_r/λ

C. λ/(2v_r)

D. 2λv_r

Correct Answer: B. 2v_r/λ

Question 5

Which quantity is a probability of declaring a target when no target is present?

A. Probability of detection

B. Track continuity

C. Probability of false alarm

D. Availability

Correct Answer: C. Probability of false alarm

Question 6

Which radar architecture generally requires the greatest emphasis on synchronization and data fusion?

A. Single-site monostatic radar

B. Multistatic radar

C. Simple non-coherent CW radar

D. Standalone mechanically scanned radar

Correct Answer: B. Multistatic radar

Question 7

A radar operating at 10 GHz has an approximate wavelength of

A. 3 cm

B. 30 cm

C. 3 m

D. 0.3 mm

Correct Answer: A. 3 cm

Question 8

Which block protects a receiver from high transmitter power when a shared antenna is used?

A. Tracker

B. Duplexer or circulator

C. Analog-to-digital converter

D. Clutter map

Correct Answer: B. Duplexer or circulator

Question 9

Which statement correctly distinguishes resolution from accuracy?

A. They are always identical quantities.

B. Resolution concerns separating targets, whereas accuracy concerns closeness to truth.

C. Accuracy concerns bandwidth, whereas resolution concerns legal compliance.

D. Resolution can be defined only for bistatic radars.

Correct Answer: B. Resolution concerns separating targets, whereas accuracy concerns closeness to truth.

Question 10

For a conventional pulsed radar with PRF = 1 kHz, the idealized maximum unambiguous range is approximately

A. 15 km

B. 150 km

C. 300 km

D. 3,000 km

Correct Answer: B. 150 km