## 3 Measurements
```
1:Initialization: Connect the instruments and load basic settings;
2:\(f_{FG\_NEXT}\leftarrow\) 942.5 kHz;
3: Set output frequency of 33220A \(f_{FG}\gets f_{FG\_NEXT}\); \(V_{FG\_NEXT}\gets 170\) mV\({}_{\text{PP}}\);
4: REG_Flag \(\leftarrow\)\(False\); \(V_{FG\_REG\_MIN}\gets 0\); \(V_{FG\_unREG\_MAX}\gets 0\);
5: Set output amplitude of 33220A \(V_{FG}\gets V_{FG\_NEXT}\);
6: Enable output of 33220A; Trigger N3301A and wait for 20 seconds;
7:if N3301A is in an unregulated state then
8: Disable output of 33220A;
9:if\(V_{FG}=170\) mV\({}_{\text{PP}}\) or REG_Flag \(=False\) and \(V_{FG\_REG\_MIN}=0\)then
10:\(V_{FG\_unREG\_MAX}\gets V_{FG}\); \(V_{FG\_NEXT}\gets V_{FG}+5\ mV_{PP}\);
11:else if REG_Flag \(=False\) and \(V_{FG\_REG\_MIN}\
eq 0\)then
12:if\(V_{FG}>V_{FG\_unREG\_MAX}\)then\(V_{FG\_unREG\_MAX}\gets V_{FG}\);
13:\(V_{FG\_NEXT}\leftarrow\)ceil {\((V_{FG\_unREG\_MAX}+V_{FG\_REG\_MIN})\div 2\)};
14:else if REG_Flag \(=\)\(True\) and \(V_{FG\_unREG\_MAX}=0\)then
15:\(V_{FG\_unREG\_MAX}\gets V_{FG}\); \(V_{FG\_NEXT}\leftarrow\)ceil {\((V_{FG}+V_{FG\_REG\_MIN})\div 2\)};
16:else if REG_Flag \(=\)\(True\) and \(V_{FG\_unREG\_MAX}\
eq 0\)then
17:if\(V_{FG}<V_{FG\_REG\_MIN}\)then\(V_{FG\_REG\_MIN}\gets V_{FG}\);
18:\(V_{FG\_NEXT}\leftarrow\)ceil {\((V_{FG\_unREG\_MAX}+V_{FG\_REG\_MIN})\div 2\)};
19: REG_Flag \(\leftarrow\)\(False\);
20:else
21: Wait until MSO9254A and N3301A finish acquisition and measurements;
22: Disable output of 33220A and save acquired waveform data and measurement results;
23:if\(V_{FG}=170\) mV\({}_{\text{PP}}\) or REG_Flag \(=\)\(True\) and \(V_{FG\_unREG\_MAX}=0\)then
24:\(V_{FG\_REG\_MIN}\gets V_{FG}\); \(V_{FG\_NEXT}\gets V_{FG}-5\ mV_{PP}\);
25:else if REG_Flag \(=\)\(True\) and \(V_{FG\_unREG\_MAX}\
eq 0\)then
26:if\(V_{FG}<V_{FG\_REG\_MIN}\) then\(V_{FG\_REG\_MIN}\gets V_{FG}\);
27:\(V_{FG\_NEXT}\leftarrow\)ceil {\((V_{FG\_unREG\_MAX}+V_{FG\_REG\_MIN})\div 2\)};
28:else if REG_Flag \(=\)\(False\) and \(V_{FG\_REG\_MIN}=0\)then
29:\(V_{FG\_REG\_MIN}\gets V_{FG}\); \(V_{FG\_NEXT}\leftarrow\)ceil {\((V_{FG\_unREG\_MAX}+V_{FG})\div 2\)};
30:else if REG_Flag \(=\)\(False\) and \(V_{FG\_REG\_MIN}\
eq 0\)then
31:if\(V_{FG}<V_{FG\_REG\_MIN}\) then\(V_{FG\_REG\_MIN}\gets V_{FG}\);
32:\(V_{FG\_NEXT}\leftarrow\)ceil {\((V_{FG\_unREG\_MAX}+V_{FG\_REG\_MIN})\div 2\)};
33: REG_Flag \(\leftarrow\)\(True\);
34:if\(V_{FG\_NEXT}\leq 210\) mV\({}_{\text{PP}}\) and \(V_{FG\_NEXT}\
eq V_{FG}\)then goto \(5\);
35:if\(f_{FG}<944.9\) kHz then\(f_{FG\_NEXT}\gets f_{FG}+0.1\) kHz; goto \(3\);
36:Finish: Disconnect the instruments;
```  
**Algorithm 1** Automated measurement algorithm of the system. Figure 14a,b show that the highest DC output power (15.7 W) and the maximum power transfer efficiency of the system (27.7%) both occur at 944.4 kHz. The power transfer efficiency of the system is defined as  
\[\eta_{sys}=\frac{P_{\text{DC, }sys}}{S_{in,\ mch}}\times 100\% \tag{40}\]  
where \(S_{in,\ mch}\) is the input apparent power of the matched channel. The apparent power was calculated from the product of the root-mean-square values of the voltage and current [29]. The power transfer efficiency of the matched acoustic-electric channel was calculated by \[\eta_{mch}=\frac{P_{out,\;mch}}{S_{in,\;mch}}\times 100\% \tag{41}\]  
where \(P_{out,\;mch}\) is the output active power of the matched channel. \(P_{out,\;mch}\) was calculated by  
\[P_{out,\;mch}=\frac{1}{T_{meas}}\int_{0}^{T_{meas}}v_{out,\;mch}\left(t\right)i_ {out,\;mch}\left(t\right)dt \tag{42}\]  
where \(v_{out,\;mch}\left(t\right)\) and \(i_{out,\;mch}\left(t\right)\) are the transient output voltage and current of the matched channel, respectively, \(T_{meas}\) is the measurement time [29]. Figure 14c shows the input resistance and reactance of the matched channel while Figure 14d shows those of the AC-DC converter.