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Question 1Information, Electronics and Communications Technology (IECT)

In a digital communication system, which term describes the process of representing an analog information signal by a finite set of discrete levels before transmission?

  1. Equalisation
  2. Modulation
  3. Quantisation Correct answer.
  4. Multiplexing

Explanation

Quantisation maps a continuous range of sample amplitudes onto a finite set of discrete levels, which is the essential step that converts sampled analog values into digital symbols. Modulation instead shifts a signal onto a carrier, multiplexing shares a channel, and equalisation compensates channel distortion.

Question 2Information, Electronics and Communications Technology (IECT)

Which logic gate produces a HIGH output only when all of its inputs are HIGH?

  1. OR gate
  2. AND gate Correct answer.
  3. NAND gate
  4. XOR gate

Explanation

The AND gate outputs logic 1 only for the single input combination in which every input is 1, and outputs 0 otherwise. This is the defining truth-table behaviour that distinguishes it from OR, NAND and XOR gates.

Question 3Information, Electronics and Communications Technology (IECT)

In the context of the Internet protocol suite, which protocol provides connectionless, best-effort delivery of datagrams without guaranteeing order or arrival?

  1. TCP
  2. ARP
  3. UDP Correct answer.
  4. FTP

Explanation

UDP sends datagrams without establishing a connection and provides no acknowledgement, retransmission or sequencing, so delivery is best-effort. TCP adds connection setup, acknowledgements and ordered delivery, while FTP and ARP serve other purposes.

Question 4Information, Electronics and Communications Technology (IECT)

Which number system uses the digits 0 through 9 and the letters A through F, with each position representing a power of sixteen?

  1. Decimal
  2. Binary
  3. Octal
  4. Hexadecimal Correct answer.

Explanation

Hexadecimal is base 16 and therefore needs sixteen symbols, supplied by 0-9 plus A-F, where A stands for ten and F for fifteen. It is widely used as a compact notation for binary values in computing.

Question 5Information, Electronics and Communications Technology (IECT)

Which type of semiconductor material is produced by adding a pentavalent impurity such as phosphorus to intrinsic silicon?

  1. P-type
  2. Insulating
  3. Intrinsic
  4. N-type Correct answer.

Explanation

A pentavalent donor atom contributes an extra electron, so the majority carriers become electrons and the material is called N-type. Trivalent acceptor impurities create holes and give P-type material instead.

Question 6Information, Electronics and Communications Technology (IECT)

Which property of an ideal operational amplifier implies that no current flows into either input terminal?

  1. Infinite input impedance Correct answer.
  2. Infinite bandwidth
  3. Zero output impedance
  4. Infinite open-loop gain

Explanation

Infinite input impedance means the input terminals draw no current, which supports the ideal virtual-open assumption in op-amp analysis. Infinite gain supports the virtual-short assumption, and zero output impedance concerns the output side.

Question 7Information, Electronics and Communications Technology (IECT)

In a microprocessor, which unit performs arithmetic operations and logical comparisons on data held in registers?

  1. Control unit
  2. Instruction decoder
  3. Arithmetic Logic Unit Correct answer.
  4. Memory management unit

Explanation

The Arithmetic Logic Unit contains the combinational circuitry that adds, subtracts and performs logical operations on operands supplied from registers. The control unit sequences operations, while the decoder interprets instruction opcodes.

Question 8Information, Electronics and Communications Technology (IECT)

Which electromagnetic spectrum band is conventionally used for satellite communication because it passes through the ionosphere and suffers low atmospheric attenuation?

  1. Microwave Correct answer.
  2. Extremely Low Frequency
  3. Very Low Frequency
  4. High Frequency

Explanation

Microwave frequencies, roughly from 1 GHz upward, pass through the ionosphere with little absorption and support the wide bandwidths and directional antennas needed for satellite links. Lower bands either reflect from or are absorbed in the ionosphere and offer far less bandwidth.

Question 9Information, Electronics and Communications Technology (IECT)

A resistor of 2.2 kilo-ohm is connected across a 12 V supply. What current flows through it, to two significant figures?

  1. 26 mA
  2. 2.6 mA
  3. 0.55 mA
  4. 5.5 mA Correct answer.

Explanation

Ohm's law gives I = V/R = 12 / 2200 = 5.45 milliamperes, which rounds to 5.5 mA to two significant figures. The calculation simply requires converting kilo-ohms to ohms before dividing.

Question 10Information, Electronics and Communications Technology (IECT)

A logic circuit implements the function F = A'B + AB'. Which single gate performs this operation on inputs A and B?

  1. XNOR gate
  2. XOR gate Correct answer.
  3. NOR gate
  4. AND gate

Explanation

The expression is true only when exactly one input is high, which is the exclusive-OR function. XNOR is its complement, true when both inputs are equal.

Question 11Information, Electronics and Communications Technology (IECT)

A 4-bit binary counter is clocked continuously and starts from 0000. After exactly 13 clock pulses, what is its binary state?

  1. 1011
  2. 1100
  3. 1101 Correct answer.
  4. 1110

Explanation

Counting thirteen pulses from zero gives the decimal value thirteen, which in 4-bit binary is 1101 (8 + 4 + 1). The nibble simply represents the accumulated count modulo sixteen.

Question 12Information, Electronics and Communications Technology (IECT)

In a Class B push-pull amplifier, what is the approximate theoretical maximum collector efficiency for a sinusoidal output?

  1. 78.5 percent Correct answer.
  2. 25 percent
  3. 50 percent
  4. 100 percent

Explanation

A Class B stage conducts on alternate half-cycles, and the maximum theoretical efficiency is pi/4, about 78.5 percent. Class A is limited to 25 percent with resistive load and 50 percent with transformer coupling.

Question 13Information, Electronics and Communications Technology (IECT)

A signal of bandwidth 4 kHz is sampled at the Nyquist minimum rate and each sample is encoded with 8 bits. What is the resulting bit rate?

  1. 16 kbit/s
  2. 64 kbit/s Correct answer.
  3. 32 kbit/s
  4. 8 kbit/s

Explanation

The Nyquist rate is twice the highest frequency, so 2 x 4 kHz gives 8000 samples per second, and multiplying by 8 bits per sample yields 64 kbit/s. Both factors must be applied before multiplying by the bit depth.

Question 14Information, Electronics and Communications Technology (IECT)

Which IPv4 address range is reserved for private networks under RFC 1918?

  1. 224.0.0.0 to 239.255.255.255
  2. 172.16.0.0 to 172.31.255.255 Correct answer.
  3. 192.0.2.0 to 192.0.2.255
  4. 169.254.0.0 to 169.254.255.255

Explanation

RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 for private addressing, and the 172.16-172.31 block belongs to the second of these. The other listed ranges serve documentation, multicast and link-local purposes.

Question 15Information, Electronics and Communications Technology (IECT)

A 4-bit successive approximation ADC has a full-scale reference of 8 V. What is the minimum voltage change it can resolve?

  1. 0.5 V Correct answer.
  2. 1.0 V
  3. 2.0 V
  4. 0.25 V

Explanation

A 4-bit converter resolves the reference into 2^4 = 16 steps, so the resolution is 8 V divided by 16, which equals 0.5 V. Resolution improves as the bit count increases.

Question 16Information, Electronics and Communications Technology (IECT)

In a 16-QAM constellation, how many distinct symbol states exist and how many bits does each symbol carry?

  1. 16 states carrying 4 bits each Correct answer.
  2. 16 states carrying 8 bits each
  3. 8 states carrying 3 bits each
  4. 32 states carrying 5 bits each

Explanation

The number in the name gives the constellation size, so 16-QAM has 16 symbol points, and log2(16) = 4 bits are mapped to each symbol. Higher-order QAM carries more bits per symbol but requires a better signal-to-noise ratio.

Question 17Information, Electronics and Communications Technology (IECT)

Which memory technology stores data as charge on a floating gate and therefore retains its contents when power is removed?

  1. Flash memory Correct answer.
  2. Register file
  3. Dynamic RAM
  4. Static RAM

Explanation

Flash memory uses floating-gate transistors that trap charge, giving non-volatile storage that survives power loss. SRAM and DRAM both lose their contents when power is removed and need refresh or continuous supply.

Question 18Information, Electronics and Communications Technology (IECT)

An antenna has a gain of 20 dBi. By what factor does it increase power density in its main direction compared with an isotropic radiator?

  1. 100 Correct answer.
  2. 20
  3. 200
  4. 10

Explanation

Decibel gain is converted by G = 10^(dBi/10), so 20 dBi corresponds to 10^2 = 100 times the isotropic power density. Each 10 dB step represents a tenfold increase.

Question 19Information, Electronics and Communications Technology (IECT)

In a GSM cellular network, which network element holds the permanent subscriber identity and authentication keys and is queried during authentication?

  1. Base transceiver station
  2. Mobile switching centre
  3. Authentication Centre Correct answer.
  4. Gateway GPRS support node

Explanation

The Authentication Centre stores the subscriber authentication key and generates the authentication vectors used to challenge the mobile station. The BTS handles radio transmission, the MSC switches calls, and the GGSN provides packet-data gateway functions.

Question 20Information, Electronics and Communications Technology (IECT)

Which memory addressing mode allows an instruction to specify an operand by giving the address of the address of the operand?

  1. Register addressing
  2. Indirect addressing Correct answer.
  3. Immediate addressing
  4. Direct addressing

Explanation

In indirect addressing the instruction supplies a location whose contents are the effective address, so one extra memory access is needed to fetch the operand. Immediate addressing embeds the operand itself in the instruction.

Question 21Information, Electronics and Communications Technology (IECT)

A 50 Hz sinusoidal waveform has a peak value of 325 V. What is its RMS value, to the nearest volt?

  1. 325 V
  2. 460 V
  3. 230 V Correct answer.
  4. 163 V

Explanation

For a sinusoid the RMS value equals the peak divided by the square root of two, so 325 / 1.414 gives approximately 230 V. This is the standard relationship behind nominal 230 V mains supplies.

Question 22Information, Electronics and Communications Technology (IECT)

A 2-kilobyte block of data is transferred over a link in 8 milliseconds. What is the effective throughput in kilobits per second?

  1. 512 kbit/s
  2. 2048 kbit/s Correct answer.
  3. 256 kbit/s
  4. 2000 kbit/s

Explanation

Two kilobytes is 2048 bytes, which is 16384 bits. Dividing by 0.008 seconds gives 2,048,000 bits per second, that is 2048 kbit/s, where the binary kilobyte convention is applied.

Question 23Information, Electronics and Communications Technology (IECT)

An amplifier with an open-loop gain of 1000 and negative feedback of 0.1 is configured as a closed-loop stage. What is the approximate closed-loop gain?

  1. 0.1
  2. 100
  3. 9.99 Correct answer.
  4. 1000

Explanation

The closed-loop gain is A/(1 + AB), giving 1000/(1 + 100) = 1000/101, approximately 9.9. The large loop gain drives the result close to the reciprocal of the feedback factor, 1/0.1 = 10.

Question 24Information, Electronics and Communications Technology (IECT)

A binary symmetric channel has a bit error probability of 0.01. What is the probability that a transmitted bit is received correctly?

  1. 0.99 Correct answer.
  2. 0.5
  3. 0.01
  4. 0.98

Explanation

In a binary symmetric channel the error probability is the same for both symbols, so the correct-reception probability is simply 1 minus the error probability, giving 0.99. The two probabilities must sum to one because the output is always either correct or in error.

Question 25Information, Electronics and Communications Technology (IECT)

In a PCM system the quantisation noise is reduced by one bit. What is the approximate improvement in signal-to-quantisation-noise ratio?

  1. About 1 dB
  2. About 6 dB Correct answer.
  3. About 3 dB
  4. About 12 dB

Explanation

Each additional bit halves the quantisation step, which quarters the noise power and therefore improves the signal-to-noise ratio by about 6 dB. The rule of thumb is often written as SNR in dB being approximately 6n plus 1.8 for a full-scale sinusoid.

Question 26Information, Electronics and Communications Technology (IECT)

In the context of the IECT syllabus, which statement best describes the difference between a microprocessor and a microcontroller?

  1. A microcontroller cannot execute stored programs and is limited to hardwired logic control
  2. A microprocessor is always faster in clock speed than a microcontroller and therefore replaces it in embedded designs
  3. A microcontroller integrates CPU, memory and I/O peripherals on a single chip, while a microprocessor is typically a CPU-only device requiring external memory and peripherals Correct answer.
  4. A microprocessor integrates CPU, memory and peripherals on one chip, while a microcontroller contains only the ALU

Explanation

The defining distinction is integration: a microcontroller is a complete computer on a chip with on-board program/data memory and peripherals, whereas a microprocessor exposes mainly the CPU core and relies on external support chips. Clock speed is not the defining criterion, and microcontrollers certainly execute stored programs.

Question 27Information, Electronics and Communications Technology (IECT)

Which logic family characteristic makes CMOS preferred over TTL for battery-operated portable IECT equipment?

  1. CMOS logic levels are incompatible with any supply above 5 V
  2. CMOS has negligible static power dissipation because one transistor of each complementary pair is always off Correct answer.
  3. CMOS operates only with bipolar junction transistors and therefore switches faster
  4. CMOS devices have lower input impedance, which reduces drive current requirements

Explanation

In a static CMOS gate the pull-up and pull-down networks are complementary, so essentially no direct path exists from supply to ground except during switching. This gives very low quiescent current draw, which extends battery life. Speed and input impedance arguments in the other options are incorrect for CMOS.

Question 28Information, Electronics and Communications Technology (IECT)

A 3-input AND gate has inputs A = 1, B = 1 and C = 0. What is the output?

  1. Indeterminate
  2. Equal to C inverted
  3. 0 Correct answer.
  4. 1

Explanation

An AND gate produces a logic 1 only when every input is 1. Since C is 0, the output is forced to 0 regardless of the other inputs. This is the standard behaviour of the AND function.

Question 29Information, Electronics and Communications Technology (IECT)

Which type of optical fibre supports multiple propagation paths and is typically used for short-distance, low-cost IECT links?

  1. Dispersion-shifted single-mode fibre
  2. Single-mode step-index fibre
  3. Multimode fibre Correct answer.
  4. Polarisation-maintaining fibre

Explanation

Multimode fibre has a core large enough to support many propagating modes, which simplifies connector alignment and lowers cost but limits bandwidth-distance product due to modal dispersion. Single-mode variants carry one mode and are used for long-haul links.

Question 30Information, Electronics and Communications Technology (IECT)

Which protocol operates at the transport layer of the TCP/IP model and provides reliable, connection-oriented delivery with acknowledgements?

  1. TCP Correct answer.
  2. UDP
  3. ICMP
  4. ARP

Explanation

TCP is the connection-oriented transport protocol that establishes a session, numbers segments, acknowledges receipt and retransmits lost data. UDP is connectionless, while ICMP and ARP operate at other layers for diagnostics and address resolution.

Question 31Information, Electronics and Communications Technology (IECT)

Which statement correctly describes the function of a diode in a half-wave rectifier circuit?

  1. It stores charge to smooth the ripple completely without any capacitor
  2. It allows current in both directions equally
  3. It converts the AC frequency to a higher value
  4. It conducts on one half-cycle and blocks the other, producing a pulsating DC output Correct answer.

Explanation

A rectifier diode is forward-biased on one half-cycle and reverse-biased on the other, so the load sees only one polarity of the input. The result is a pulsating unidirectional output that a filter capacitor then smooths.

Question 32Information, Electronics and Communications Technology (IECT)

In a communication system, what is the primary function of the modulation process?

  1. To remove noise from the message signal before transmission
  2. To compress the message so that less bandwidth is used
  3. To shift the information signal onto a carrier frequency suitable for transmission through the medium Correct answer.
  4. To increase the physical length of the antenna required for radiation

Explanation

Modulation superimposes the baseband message onto a higher-frequency carrier so that the signal matches the transmission medium and allows efficient radiation from practical antennas. It does not by itself remove noise or compress data.

Question 33Information, Electronics and Communications Technology (IECT)

Which binary number is the 2's complement representation of the decimal value -5 in an 8-bit register?

  1. 00000101
  2. 10000101
  3. 11111011 Correct answer.
  4. 11111010

Explanation

The 8-bit representation of +5 is 00000101. Inverting the bits gives 11111010, and adding one gives 11111011, which is the 2's complement of -5. The sign bit is 1, as expected for a negative value.

Question 34Information, Electronics and Communications Technology (IECT)

A 10 kΩ resistor and a 20 kΩ resistor are connected in parallel. What is the equivalent resistance?

  1. 2 kΩ
  2. 30 kΩ
  3. 15 kΩ
  4. 6.67 kΩ Correct answer.

Explanation

For two resistors in parallel, R = (R1 × R2)/(R1 + R2) = (10 × 20)/(10 + 20) kΩ = 200/30 kΩ ≈ 6.67 kΩ. The equivalent value must be smaller than the smallest branch resistance, which confirms the result.

Question 35Information, Electronics and Communications Technology (IECT)

A JFET is described as a voltage-controlled device. Which quantity controls the drain current in the saturation region?

  1. The drain-source capacitance
  2. The gate-source voltage Correct answer.
  3. The ambient temperature alone
  4. The gate current

Explanation

A JFET is a voltage-controlled device because the reverse-biased gate-source voltage modulates the depletion region width and therefore the channel conductance, controlling drain current. Gate current is negligible in normal operation because the gate junction is reverse-biased.

Question 36Information, Electronics and Communications Technology (IECT)

A signal x(t) = 5 sin(200πt) is applied to an ideal differentiator circuit. What is the amplitude of the output?

  1. 1000π V Correct answer.
  2. 200π V
  3. 5 V
  4. 25 V

Explanation

Differentiating A sin(ωt) gives Aω cos(ωt), so the output amplitude is Aω. Here A = 5 and ω = 200π rad/s, so the amplitude is 5 × 200π = 1000π V. The phase also shifts by 90°.

Question 37Information, Electronics and Communications Technology (IECT)

In a 4-bit digital-to-analogue converter with a full-scale output of 15 V and a binary input of 1010, what is the output voltage (assuming ideal operation)?

  1. 10 V Correct answer.
  2. 7.5 V
  3. 5 V
  4. 12 V

Explanation

The binary input 1010 equals decimal 10. With a 4-bit converter of full-scale 15 V, the step size is 15/15 = 1 V, so the output is 10 × 1 V = 10 V. This assumes a straight binary weighted ladder.

Question 38Information, Electronics and Communications Technology (IECT)

Which addressing mode is used when an instruction operand is held in a register specified by the instruction itself?

  1. Immediate addressing
  2. Direct addressing
  3. Register addressing Correct answer.
  4. Indexed addressing

Explanation

In register addressing the operand resides in a CPU register named in the instruction, so no memory access is required to fetch the operand. Immediate addressing embeds the value in the instruction, while direct and indexed modes reference memory.

Question 39Information, Electronics and Communications Technology (IECT)

A 1 MHz carrier is amplitude-modulated by a 5 kHz sinusoidal tone. What is the bandwidth of the resulting AM signal?

  1. 1.005 MHz
  2. 5 kHz
  3. 1 MHz
  4. 10 kHz Correct answer.

Explanation

DSB full-carrier AM produces an upper sideband at fc + fm and a lower sideband at fc − fm. The bandwidth is therefore 2fm = 2 × 5 kHz = 10 kHz, independent of the carrier frequency.

Question 40Information, Electronics and Communications Technology (IECT)

In an FM system, increasing the modulation index while keeping the modulating frequency constant generally causes which change?

  1. A decrease in the number of significant sidebands and narrower bandwidth
  2. Complete suppression of the carrier and elimination of all sidebands
  3. An increase in the number of significant sidebands and wider bandwidth Correct answer.
  4. No change in bandwidth because FM bandwidth depends only on carrier frequency

Explanation

Carson's rule gives bandwidth ≈ 2(Δf + fm), and the modulation index is Δf/fm. Raising the index increases the number of significant Bessel sidebands, so the occupied bandwidth grows. FM bandwidth is therefore not fixed by the carrier alone.

Question 41Information, Electronics and Communications Technology (IECT)

Which multiple-access technique assigns each user a distinct time slot within a shared frequency channel?

  1. CSMA/CD
  2. TDMA Correct answer.
  3. CDMA
  4. FDMA

Explanation

Time-division multiple access shares one frequency channel by allocating non-overlapping time slots to different users. FDMA separates users by frequency, and CDMA separates them by orthogonal spreading codes.

Question 42Information, Electronics and Communications Technology (IECT)

A network uses the IPv4 address block 192.168.10.0/26. How many usable host addresses does each subnet provide?

  1. 32
  2. 62 Correct answer.
  3. 64
  4. 30

Explanation

A /26 prefix leaves 32 − 26 = 6 host bits, giving 2^6 = 64 total addresses. Subtracting the network and broadcast addresses leaves 62 usable host addresses.

Question 43Information, Electronics and Communications Technology (IECT)

In a CSMA/CD Ethernet LAN, what is the purpose of the jam signal transmitted after a collision is detected?

  1. To inform all stations that a collision has occurred so they abort transmission and back off Correct answer.
  2. To synchronise the clocks of the transmitting stations
  3. To increase the data rate of the colliding frames
  4. To reset the MAC address tables of all switches

Explanation

After detecting a collision, a station sends a brief jam signal to ensure every other station on the segment also recognises the collision. All stations then stop transmitting and enter the binary exponential backoff procedure.

Question 44Information, Electronics and Communications Technology (IECT)

A 100 W transmitter feeds an antenna through a cable with 3 dB loss. What is the power delivered to the antenna?

  1. 50 W Correct answer.
  2. 33 W
  3. 25 W
  4. 97 W

Explanation

A 3 dB loss halves the power, since 10 log10(0.5) ≈ −3 dB. Therefore 100 W becomes 50 W at the antenna terminals. Loss in dB is subtracted directly from the power level.

Question 45Information, Electronics and Communications Technology (IECT)

In a superheterodyne receiver, what is the purpose of the intermediate frequency (IF) stage?

  1. To down-convert the received signal to a fixed frequency where selective filtering and amplification are easier Correct answer.
  2. To radiate the received signal back to the transmitter
  3. To generate the RF carrier for the transmitter
  4. To eliminate the need for an antenna

Explanation

Mixing the incoming RF with a local oscillator produces a fixed IF, allowing sharp, stable filters and high-gain amplifiers to be built at one frequency regardless of the tuned channel. This improves selectivity and simplifies receiver design.

Question 46Information, Electronics and Communications Technology (IECT)

A 3-bit flash ADC uses how many comparators, and what is its main advantage over a successive-approximation ADC?

  1. 8 comparators; higher resolution
  2. 3 comparators; lower power consumption
  3. 1 comparator; simpler circuitry
  4. 7 comparators; very high conversion speed Correct answer.

Explanation

A flash ADC with n bits requires 2^n − 1 comparators, so a 3-bit converter needs seven. All comparators evaluate simultaneously, giving the fastest conversion speed of any ADC architecture, at the cost of high comparator count and power.

Question 47Information, Electronics and Communications Technology (IECT)

In a 7-bit Hamming code used for single-error correction, how many parity bits are required and what is the total codeword length?

  1. 2 parity bits, 9-bit codeword
  2. 3 parity bits, 10-bit codeword
  3. 5 parity bits, 12-bit codeword
  4. 4 parity bits, 11-bit codeword Correct answer.

Explanation

For m data bits, r parity bits must satisfy 2^r ≥ m + r + 1. With m = 7, r = 4 gives 16 ≥ 12, which is satisfied, while r = 3 gives 8 ≥ 11, which fails. The codeword is therefore 7 + 4 = 11 bits.

Question 48Information, Electronics and Communications Technology (IECT)

A feedback amplifier has an open-loop gain A = 500 and a feedback factor β = 0.02. If the open-loop gain changes by 10%, by approximately what percentage does the closed-loop gain change?

  1. About 1% Correct answer.
  2. About 10%
  3. About 0.1%
  4. About 5%

Explanation

The desensitivity factor is 1 + Aβ = 1 + 500 × 0.02 = 11. Fractional changes in closed-loop gain are reduced by this factor, so a 10% open-loop change becomes roughly 10%/11 ≈ 0.9%, i.e. about 1%. This illustrates how negative feedback stabilises gain.

Question 49Information, Electronics and Communications Technology (IECT)

A satellite downlink operates at 12 GHz with a receiving antenna of 2 m diameter. If the antenna aperture efficiency is 0.6, what is the approximate gain in dBi? (Use G = η(πD/λ)².)

  1. About 46 dBi Correct answer.
  2. About 52 dBi
  3. About 40 dBi
  4. About 32 dBi

Explanation

The wavelength is λ = c/f = 3×10^8 / 12×10^9 = 0.025 m. Then πD/λ = π × 2 / 0.025 ≈ 251.3, and squaring gives about 63,170. Multiplying by η = 0.6 yields about 37,900, which in decibels is 10 log10(37,900) ≈ 45.8 dBi, i.e. about 46 dBi.

Question 50Information, Electronics and Communications Technology (IECT)

In a PCM system using 8-bit uniform quantisation, what is the approximate signal-to-quantisation-noise ratio for a full-scale sinusoidal input?

  1. About 62 dB
  2. About 98 dB
  3. About 74 dB
  4. About 50 dB Correct answer.

Explanation

For uniform quantisation of a full-scale sinusoid, SQNR ≈ 6.02n + 1.76 dB. With n = 8 this gives about 48.2 + 1.76 ≈ 50 dB. Each additional bit improves SQNR by roughly 6 dB.