实验报告Word格式.docx

1、 transmission parameters only）, the method of the measurement and calculation will be shortly and expressly illustrated in the part of Theoretical Backgrounds, within the knowledge of measuring individual parameters, we are aiming to investigate the relationships between these and those of two-port

2、networks in cascade and parallel; part2 is to find out the two-port network transient response containing capacitive and inductive reactances. Theoretical BackgroundsMeasurement of Y-Parameters （Admittance parameters）The equations for the parameters are:I1 = y11V1 + y12V2 I2 = y21V1 + y22V2 i.e. I =

3、 YV where are the Y-parameters of the two-port network.Experimentally, these parameters can be determined by short circuiting one port at a time. This is why these parameters are also termed the short-circuit admittance parameters.The following shows how to calculate the parameters:When output port

4、is shorted （as shown in Figure2）:V2 = 0 Figure2y11 = I1 / V1 and y21 = I2 / V1When input port is shorted:V1 = 0 Figure3y12 = I1 / V2 and y22 = I2 / V2Measurement of Transmission （ABCD-） ParametersV1 = AV2 - BI2I1 = CV2 - DI2or where t is the transmission parameters of the two-port network.Experiment

5、ally, the t-parameters can be obtained by short circuiting and open circuiting the output one at a time.Output port is open-circuited:I2 = 0 Figure4A = V1 / V2 and C = I1 / V2Output port is short-circuited:V2 = 0 Figure5B = - V1 / I2 and D = - I1 / I2Cascade Interconnection of 2 Two-port NetworksCon

6、sider the 2 two-port networks A and B （as shown in FIigure1） connected in cascade, as shown in Figure6. The overall transmission parameters of the combined network N can be obtained as the following （for each single network, the measurement of parameters can be obtained as previous）:Figure6tN = tA t

7、Bso that, the following can be obtained:Parallel Interconnection of 2 Two-Port NetworksConsider the 2 two-port networks A and B （as shown in FIigure1） connected in cascade, as shown in Figure7. The overall admittance （Y-） parameters of the combined network N can be obtained as the following: Figure7

8、It is obvious that I1 = I1A + I1BI2 = I2A + I2BV1 = V1A = V1BV2 = V2A = V2B;and= = + = += It can be seen that the overall Y-parameters can be obtained by summing the corresponding Y-parameters of individual networks A and B, when the A,B networks are not altered by the parallel connection.Transient

9、Responses of Two-port NetworkAccording to the damping ratio, （The ratio of the actual resistance in damped harmonic motion to that necessary to produce critical damping. Also known as relative damping ratio）, we divide the transient responses into three types, which are over damped response （ 1）, un

10、der damped response （ 1, the poles are real and distinct, the solution is simply a decaying exponential with no oscillation and the transient response will be over damped. This response is slow and has no overshoots and undershoots.Under damped: The poles are complex, and the transient response will

11、 be under damped if 1, then the solution is a decaying exponential combined with an oscillatory portion. Overshoots and undershoots will be produced.Critically damped: when = 1, the poles are real and equal, and the transient response will be critically damped. No overshoots or undershoots will be p

12、roduced and the response will be faster than over damped response. This turns out to be a desirable outcome in many cases where engineering design of a damped oscillator is requiredIn this experiment, we are mainly using the second type, which is the under damped response.And the characteristic equa

13、tion is given by:S2 + 2nS + n2where n = undamped natural frequency = 1/（ LC ） n （1 - 2 ） = damped natural frequency = damping ratio = Detailed method of calculation is shown in Appendix B attached with the laboratory manual. Objectives To measure the admittance-parameters and transmission parameters

14、 of two-port network To investigate the relationships between individual network parameters and two-port networks in cascade and parallel connections To study the transient response of a two-port network containing capacitive and inductive reactances. Equipment Digital Storage Oscilloscope Function

15、Generator （50） Digital Multimeter Inductor with 2 inductance steps Capacitors: 22F, 100F Resistors: 33, 100 （2）, 220, 330, 560, 680, 3.9k, 4.7k （2）, 5.6k, 6.8k Bread-board ProceduresMeasurement of Admittance-Parameters and Transmission Parameters Connect the resistive network A as shown in Figure8.

16、With the network connected, apply a 1kHz, 10 volts peak to peak sinusoidal voltage:a） Port 1 with port 2 open-circuitedb） Port 1 with port 2 short-circuitedc） Port 2 with port 1 short-circuited Measure the voltage and current at the input and output terminals in each case. Tabulate the results in Ta

17、ble 1.Figure8 The Resistive Network A Connect the resistive network B as shown in Figure9. Measure the results for the test in the second step, and tabulate the calculated values in Table 1.Figure9 The resistive Network B Connect networks A and B in cascade as shown in Figure10. Repeat the second st

18、ep for the cascaded network.Figure10 Networks in Cascade Reconnect networks A and B in parallel as shown in Figure11. Repeat the second step for the parallel-connected network.Figure11 Networks in ParallelTable 1 （All values in rms）ResultsI1 （mA）V1 （V）V2 （V）I2 （mA）Network A（measured）2.293.542.505.53

19、4.434.425.89Network B0.693.233.893.393.47Cascaded2.592.043.341.32Parallel13.7512.2312.1414.05Questions The voltages V1 and V2 should not be connected to channel 1 and 2 of the scope simultaneously. Why?From the circuit, it can be observed that V1 and V2 have different ground. If they are connected t

20、o channel 1 and channel 2 of the oscilloscope simultaneously, both the different ground will be short-circuited, therefore cause the network under test to be short-circuited at the ground. Meanwhile it has changed the circuits configuration. Thus, there will be a big error between the readings obtai

21、ned and the real values. What should you do to the readings of peak to peak voltage in order to make them compatible with the currents measured by the digital meter?The current measured by the digital meter is in root-mean-square values （rms）. So it is obligatory to convert peak to peak voltage valu

22、es into rms values. The following shows the relationship between peak to peak values and its respective rms values: peak to peak voltage values = 2 x 2 x rms valuesTherefore, the peak to peak voltage values should be divided by 2 x 2 to make them compatible with the currents measured by the digital meter. Verify the theoretical relat