A continuous-spectrum baseband signal has a spectrum extending from near dc to 3 kHz. It is applied as one input to an ideal balanced modulator. The carrier input is a sinusoid having a frequency of 40 kHz. (a) Determine the range of frequencies contained in the DSB output spectrum. (b) Determine the required transmission bandwidth. 6-2

78. To assure the same accuracy at both 100 Hz and 100 MHz, the signal level into a frequency counter must be A higher at 100 MHz B. higher at 100 Hz C. inductively coupled at 100 MHz and capacitively coupled at 100 Hz D. resistively coupled at 100 MHz and direct coupled at 100 Hz

Q6. Figure Q6 shows the line spectrum of a modulated signal (all components are positive and real). 3 1 232 234 236 238 frequency/kHz Figure Q6: Line spectrum of a modulated signal (a) Describe the modulation scheme. (b) What are the values of the carrier frequency, modulation frequency and the modulation index? (c) What is the transmission efficiency (ratio of modulated to total power) in this example? (d) The reception of this signal is undertaken with a superheterodyne detector using an intermediate frequency of 110 kHz. What is the appropriate local oscillator frequency? (e) Demodulation of this type of signal is usually accomplished using an envelope detector. Describe the principles of operation of an envelope detector and sketch an example circuit. (f) What considerations should be made about the component values in the design of an envelope detector in order to demodulate the signal after shifting to the intermediate frequency? Relative unitsS

A discrete-spectrum baseband modulating signal has com- ponents at the following frequencies: 500 Hz, 1.5 kHz, 6-3