1. The PEP transmitted by an ACSSB system is 100 W. It takes an NE571N compandor LIC. Find the power transmitted under the no-modulation condition. The audio signal ranges from -20 dBm to +25 dBm before compression. Evaluate the compressor's output range.
2. Due to its power and bandwidth efficiencies, SSBSC is normally used in Frequency Division Multiplexing (FDM) systems. FDM systems are used to merge a number of separate information channels into a single transmission. Each channel uses a separate carrier frequency and the carriers are spaced evenly in the accessible bandwidth. Prepare a FDM system to suit the subsequent specifications.
- Available bandwidth range 100 to 120 kHz
- Number of separate information channels 4
- Information bandwidth 100 Hz to 4.5 kHz.
- Sideband suppression needed in each channel is 40 dB.
In the design you need to consider the subsequent:
- Show what is the frequency of local oscillator needed at each channel?
- Explain what are the parameters (Q, fc) for band pass filter needed at each channel?
- Provide a diagram of the FDM transmitter. As a minimum, this require to include blocks for the LO, modulator (what type should you use), amplifiers and band pass filter.
- Provide a diagram of the transmission channel. Find the information content in each channel.
3. In a broadcast FM system, the input SNR is six. Find the worst case SNR at the output if the receiver's internal noise effect is negligible.
4. Suppose the subsequent FM broadcast system.
- Deviation sensitivity 5 kHz/V.
- Information signal consists of 2 frequency components; 12sin(2?10000t), 10sin(2?15000t).
- Transmitter antenna impedance is 50?
Answer the subsequent questions related to the above FM system.
a) Show what are the modulating indexes for the two components?
b) Plot the power distribution of the transmitted signal.
c) Show what percentage of transmitted power spills into the guard band and what percentage of power spills to the adjacent channel?
d) Explain methods that will be used to avoid transmitted power spilling outside the allowed 150 kHz band.
(Use the Bessel functions to evaluate bandwidth, not the Carson's rule.)
5. A PLL's VCO free-runs at 10 MHz. The VCO does not change frequency until the input is within 20 kHz of 8 MHz. After that condition, the VCO follows the input to ±200 kHz of 8MHz before the VCO starts to free-run again. Evaluate the PLL's lock and capture range.
6. An FM receiver gives 100 dB of voltage gain prior to the limiter. Evaluate the receiver's compassion if the limiter's quieting voltage is 300 mV.
7. An AM broadcast receiver's preselect or has a total effective Q of 200 to a received signal at 1220 kHz and uses an IF of 455 kHz. Evaluate the image frequency and its dB of suppression.
8. A receiver with a 20 kHz bandwidth has an S/N of 8 dB and a sensitivity of -120 dBm. Determine the required NF.