AN4003 MA-COM | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 6
Technical content
Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. range to create a compact amplifier suitable for digital, AM and FM applications. tained in a compact aluminum housing. transformer-based matching. It is in a copper housing for maximum heat transfer.
- The RF output power at a fixed 4.0 V ALC voltage ranges from 10 W to 94 W – a variation of 9.7 dB. The
saturated RF output power ranges from 73 W to over 100 W.
400 MHz
350 MHz
300 MHz
250 MHz
175 MHz
125 MHz
90 MHz
60 MHz
30 MHz
175 MHz225 MHz
90 MHz60 MHz
Figure 1. Varying ALC voltages results in gain variation. Closed-loop control can improve gain flatness over frequency and temperature.
Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. are connected together with an optional pad between them. Both are connected directly to the 27 V DC supply. “Out” port of this coupler. The FWD coupled port is connected through a 6 dB pad to the input of the detector. put of the buffer is connected to the control amp AMP2. used to clamp the ALC voltage at 10 V and -0.7 V, to ensure safe limits for the ALC input of the Pre Amp. Figure 2. A practical control loop for the MAPM-modules using readily-available op-amps.
Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. tor or distortion in the detected output will directly affect the RF output signal level. coupler, and the reflected power port can be used for VSWR protection as discussed in Section VII. 6dB pad inserted at the input avoids overdriving the detector. drive the detector into linear operation. ated. The results are shown in Figures 4 and 5. Figure 4 shows most of the frequencies overlay each other. worst case flatness is 0.65 dB at a Power set voltage of 2.0 V. Figure 3. The completed unit using the 10W and 60W modules on their heat spreader test fixtures. The ALC loop control circuit, constructed on prototype board, is on the left.
Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. V. Closed Loop Power Control — Cont. Figure 4. Initial
Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. ALC loop tried to increase power, but the amplifier is saturated. Table I. While there was some improvement, clipping still occurred during the RF peaks at 350 MHz and 60 MHz. tended past 100 kHz at 90% modulation. reached 4%, the efficiency improved across the board at every frequency and the average was improved to 34 %. tortion due to the compression. By operating the modules in saturation, efficiency is improved. age can be lowered again, repeating the cycle indefinitely. Figure 6. Good AM performance
Closed Loop Control Maximizes MAPM-030400-010C00 and MAPM-030400-060C00 Module Performance Application Note AN4003 Rev. 1 Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Carrier Frequency Carrier Power Power Set Setting Audio Setting AM Distortion 27 V Current 27 V Efficiency 4% Dist Voltage 4% Dist Current (MHz) (W) (V) (Vpk-pk) (%) (A avg) (%) (V) (A avg) (%) 4% Dist Efficiency TABLE I CLOSED LOOP AM PERFORMANCE Notes: Input Power fixed at 13 dBm. Idq for Power Amp set to 300 mA At 90% modulation, the distortion at 350 MHz improved to 3.9%; At 90% modulation, the distortion at 60 MHz improved to 2.7% Another improvement is VSWR protection. While the circuit can be set to shutdown at the presence of signifi- cant power coming from the Reverse Power port of the directional coupler, a more sophisticated approach would detect the forward and reverse power with a log-responding detector. The difference between these signals is a direct indication of the return loss, and therefore the VSWR, of the load. A protection circuit can activate at some predetermined difference in the detected voltages. By lowering the power to a safe level, the VSWR of the out- put load can be continually monitored and full power restored when the VSWR fault is removed. VIII. Conclusion An effective and practical control circuit for the MAPM-030400-010C00 driving the MAPM-030400-060C00 has been demonstrated. The circuit works well as a power leveling circuit exhibiting gain flatness of better than 0.64 dB over the 30 to 400 MHz band. It also functions as an AM modulator with distortion better than 6% at 95% down modulation. This circuit can be the basis of a basic radio transmitter over the communication bands in the 30 MHz to 400 MHz VHF and UHF frequency spectrum. References [1] H.Krauss, C. Bostian, F. Raab, Solid State Radio Engineering, John Wiley and Sons, 1980 [2] N. Dye, H. Granberg, Radio Frequency Transistors: Principles and Practical Applications, Butterworth- Heinemann, 1993 [3] J. Millman, Microelectronics: Digital and Analog Circuits and Systems, McGraw-Hill, 1979 [4] National Semiconductor, AN-20: “An Applicat ions Guide for Op Amps,” 1969 (Re-released 2009) http://www.national.com/an/AN/AN-20.pdf [5] Analog Devices, AD8361 Datasheet [6] Analog Devices, AD8362 Datasheet Efficiency Improvement, Continued