Chapter 16, Problem 16.33P

Vs(t) + v(t) + vi(t) ZR ZL Figure 1: Second order RLC circuit Zc + ve(t) You are requested to design the circuit shown in Figure 1. The circuit is assumed to be operating at its resonant frequency when it is fed by a sinusoidal voltage source Vs (t) = 2sin(le6t). To help design your circuit you have been given the value of inductive reactance ZL = j1000. Assume that the amplitude of the current at resonance is Is (t) = 2 mA. Based on this information, answer the following to help design your circuit. Use cartesian notation for your answers, where required.

What is the attenuation at the resonant frequency? You should use the LTSpice cursors for your measurement. Answer to within 1% accuracy, or enter 0, or infinity (as "inf") (a) Attenuation (dB) = dB Check You may have noticed that it was significantly easier to use frequency-domain "AC" simulation to measure the attenuation, compared to the steps we performed in the last few questions. (i.e. via a time-domain "transient" simulation). AC analysis allows us to observe and quantify large scale positive or negative changes in a signal of interest across a wide range of different frequencies. From the response you will notice that only frequencies that are relatively close to 100 kHz have been attenuated. This is the result of the Band-reject filter you have designed, and shows the 'rejection' (aka attenuation) of any frequencies that lie in a given band. The obvious follow-up question is how do we define this band? We use a quantity known as the bandwidth. A commonly used measurement for…

V₁(t) ww ZRI ZLI ZL2 ZTH Zci VTH Zc21 Figure 8. Circuit diagram showing calculation approach for VTH and Z TH we want to create a blackbox for the red region, we want to use the same input signal conditions as previously the design of your interference ector circuit: Sine wave with a 1 Vpp, with a frequency of 100 kHz (interference) Square wave with 2.4Vpp, with a frequency of 10 kHz (signal) member an AC Thevenin equivalent is only valid at one frequency. We have chosen to calculate the Thevenin equivalent circuit (and therefore the ackbox) at the interference frequency (i.e. 100 kHz), and the signal frequency (i.e. 10 kHz) as these are the key frequencies to analyse. Your boss is assured you that the waveform converter module has been pre-optimised to the DAB Receiver if you use the recommended circuit topology.

Vs(t) + v(t) + vi(t) ZR ZL Figure 1: Second order RLC circuit Zc + ve(t) You are requested to design the circuit shown in Figure 1. The circuit is assumed to be operating at its resonant frequency when it is fed by a sinusoidal voltage source Vs (t) = 2sin(le6t). To help design your circuit you have been given the value of inductive reactance ZL = j1000. Assume that the amplitude of the current at resonance is Is (t) = 2 mA. Based on this information, answer the following to help design your circuit. Use cartesian notation for your answers, where required.

For a band-rejection filter, the response drops below this half power point at two locations as visualised in Figure 7, we need to find these frequencies. Let's call the lower frequency-3dB point as fr and the higher frequency -3dB point fH. We can then find out the bandwidth as f=fHfL, as illustrated in Figure 7. 0dB Af -3 dB Figure 7. Band reject filter response diagram Considering your AC simulation frequency response and referring to Figure 7, measure the following from your AC simulation. 1% accuracy: (a) Upper-3db Frequency (fH) = Hz (b) Lower-3db Frequency (fL) = Hz (c) Bandwidth (Aƒ) = Hz (d) Quality Factor (Q) =

V₁(t) ww ZRI ZLI Z12 Zci Zcz Figure 4. Notch filter circuit topology ши Consider the second order resonant circuit shown in Figure 4. Impedances ZLIZ C1. ZL2. Z c2 combine together forming a two-stage "band- reject" filter, so called because it rejects a "band" (aka range) of frequencies. This circuit topology is also commonly referred to as a "band-stop" filter or "notch" filter. The output of the DAB receiver block has been approximated via Thevenin's theorem for you as a voltage source Vs (t) and associated series impedance Z RI To succeed in our goal, we are going to use an iterative design approach. First we will design the interference rejector, and then repeat the process, using the output of the interference rejector to check the provided waveform converter works as intended.

1. What is the settling time for your output signal (BRF_OUT)? For this question, We define the settling time as the period of time it has taken for the output to settle into a steady state - ie when your oscillation first decays (aka reduces) to less than approximately 1/20 (5%) of the initial value.     (a) Settling time

2. What is the total impedance Zt of your designed circuit? Represent your result in cartesian form NOTE: use j to represent sqare root Zt=

An electric resistance space heater is designed such that it resembles a rectangular box 55 cm high, 75 cm long, and 20 cm wide filled with 45 kg of oil. The heater is to be placed against a wall, and thus heat transfer from its back surface is negligible. The surface temperature of the heater is not to exceed 75°C in a room at 25°C for safety considerations. The emissivity of the outer surface of the heater is 0.8 and the average temperature of the ceiling and wall surfaces is the same as the room air temperature. The properties of air at 1 atm and the film temperature are: k = 0.02753 W/m-°C, v=1.798 x 10-5 m²/s, Pr = 0.7228, and ẞ= 0.003096K-1 Wall T₁ =75°C Oil € = 0.8 Electric heater Heating element Disregarding heat transfer from the bottom and top surfaces of the heater in anticipation that the top surface will be used as a shelf, determine the power rating of the heater in W. The power rating of the heater is W.