Feature: RF design
Isolators do introduce insertion loss which can be counterbalanced by increasing the amplifier’s output power, at the trade-off of elevated operating temperatures
While they operate optimally at lower frequencies, as engineers move into mmWave frequencies, these weaknesses are amplified. Fortunately, technological advances are mitigating these inefficiencies. Companies specialising in millimetre-wave components are pioneering isolator designs optimised for higher frequencies, including those in the terahertz range. For example, Micro Harmonics
Corporation’s (MHC) reengineered isolators use much shorter ferrite rods and stronger magnetic bias fields, a technique initially developed for NASA. Tis approach ensures the necessary 45° signal rotation for isolation while significantly reducing losses in the ferrite rod. Te company’s D-band isolators achieve insertion losses below 0.9dB, allowing over 82% of the signal to pass in the forward direction.
As shown in Figure 3, isolators with
reduced insertion loss offer substantial system-wide benefits. By reducing the need to boost amplifier output, these isolators help maintain lower operating temperatures and decrease DC power consumption, leading to a more compact and efficient overall system.
The temperature-lifespan relationship Even if an amplifier has sufficient power reserves, boosting its output to counteract isolator losses carries risks. Higher operating temperatures can drastically shorten the lifespan of components. Te Arrhenius equation, which predicts failure rates in electronic systems, indicates that a 10°C increase in temperature can halve a component’s operational life. Traditional isolators lack efficient
thermal pathways, as heat is primarily dissipated through convection and radiation. Tis limitation results in elevated internal temperatures, restricting power handling capabilities. To address this, some component
manufacturers, like Micro Harmonics, are now integrating diamond heat spreaders to enhance thermal dissipation. Tis configuration facilitates superior heat conduction to the metal waveguide block, effectively reducing internal temperatures, increasing power ratings and extending component longevity.
Preserving signal integrity Signal integrity refers to an amplifier’s ability to transmit a signal without distortion or degradation. Maintaining high signal fidelity ensures the output accurately reflects the input. However, amplifying signals to compensate for system losses can introduce unwanted distortions. Exceeding an amplifier’s linear operating
range leads to signal compression. Te 1dB compression point (P1dB) defines the input power level at which the output deviates by 1dB from ideal linearity. As temperatures fluctuate, this threshold can shiſt, further impacting performance. Non-linearity in power amplifiers
results in harmonic and intermodulation
Figure 1: Amplifier with different load conditions. In the upper diagram, the amplifier is connected to a power meter, ensuring a well-matched load. The lower diagram depicts an arbitrary customer load, which can vary unpredictably, often causing reflected signals that alter the amplifier’s operating conditions, increasing temperature and reducing output power
www.electronicsworld.co.uk October 2025 31
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