Department of Radiation Oncology, Erasmus MC-Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Int J Hyperthermia. 2010;26(2):158-70. doi: 10.3109/02656730903341191.
For our head-and-neck hyperthermia (HT) applicator, an amplifier system with full amplitude and phase-control to deliver the radio-frequency signals, was not available. We therefore designed and tested a 433.92 MHz multi-channel amplifier system.
The design consists of a direct digital synthesizer (DDS) system that generates 12 phase-controlled coherent 433.92 MHz signals, which are amplified to maximum 200 W output per channel. Directional couplers are placed at the amplifiers to couple a small portion of both forward and reflected signals to gain-and-phase detectors. The power setting is applied with a resolution of 2 W and for the phase it is 0.1 degrees . The channels are sequentially sampled at 100 Hz per channel.
We tested the performance of the designed amplifier system by measuring the RF spectrum, power and phase accuracy, and by characterising the feedback control by using highly accurate power and phase meters.
The spurious emission is less than 60 dBc and the first two harmonic frequencies are suppressed more than 45 dB. The measurement accuracy for the power (+/-5%) is valid for at least 20 days after calibration and for the phase (+/-5 degrees ) it is valid for at least 2 months.
The amplifier system operates according to our design criteria to support targeted HT. It can be used for both our in-house developed superficial and head-and-neck HT applicators or any other HT applicator that works on the same frequency of 433.92 MHz.
我们的头颈部高温治疗（HT）应用器没有具有全幅度和相位控制功能的放大器系统，因此我们设计并测试了一个 433.92 MHz 多通道放大器系统。
该设计包括一个直接数字合成器（DDS）系统，可产生 12 个相位受控的相干 433.92 MHz 信号，这些信号被放大到每个通道最大 200 W 的输出。在放大器中放置定向耦合器，以将一小部分正向和反射信号耦合到增益和相位探测器。功率设置的分辨率为 2 W，相位分辨率为 0.1 度。通道以 100 Hz/通道的速率顺序采样。
我们通过测量射频频谱、功率和相位精度以及通过使用高精度功率和相位计来表征反馈控制，来测试设计的放大器系统的性能。
杂散发射小于 60 dBc，前两个谐波频率的抑制超过 45 dB。功率（+/-5%）的测量精度在校准后至少 20 天内有效，相位（+/-5 度）的测量精度在至少 2 个月内有效。
放大器系统按照我们的设计标准运行，以支持靶向 HT。它可用于我们内部开发的表面和头颈部 HT 应用器，或任何其他在 433.92 MHz 频率下工作的 HT 应用器。
