HAILP combines the benefits of passive and active Load Pull techniques in one setup.
Active Load Pull is the only method that allows reaching the low internal impedance of power transistors, especially on wafer and at very high frequencies. So far, the new Focus Microwaves HAILP system (Hybrid Active Injection Load Pull) is the active system that offers the best combination of performance, accuracy, speed and cost.
The system relies on the basic concept of using prematching electromechanical tuners for taking the impedance seen by the DUT closer to its conjugate output impedance, then complementing with active injection, the system can tune impedances anywhere in the Smith chart and beyond (г ≥ 1).
The measurements themselves are "travelling wave" based, performed using Agilent’s PNA-X or Rohde and Schwarz’s ZVA. With the introduction of prematch tuners, the feedback injection signal power remains close to the DUT output power, whereas in pure active systems, the power amplifier has to produce very high power (up to 20 times the DUT power) to compensate for the strong mismatch between the impedance of the feedback injection amplifier (50Ω) and the DUT internal impedance (0.5 - 1Ω). This multiplies the cost and reduces the frequency range of the system. More about in our November 2012 Newsletter here.
The major advantages of this technique, compared to either traditional load-pull using passive tuners or purely active load pull are:
HAILP advantages versus passive tuners (tuning)
- ΓLoad ≥ 1 (in fixture or on-wafer, at any frequency.
- Fast electronic tuning close to Γopt.
HAILP advantages versus pure active tuning (open or closed loop)
- Reduced feedback amplifier power: Pinj ≤ PDUT .
- Independent harmonic tuning without extra sources, filters and amplifiers, using MPT.
- Open-loop technology (no spurious oscillations, no RF feedback from output to input).
- Available as an upgrade to existing Focus Load Pull Systems.
- Compatible with both time-domain (sampler-based) and frequency-domain (mixer-based) receivers.
Last, not least: A critical advantage of the hybrid system is verifiability: in case of doubt, one can compare data for the same Γ, generated by either pure passive or pure active tuning; at any tuneable ΓLoad (passive tuning range is limited by the insertion loss of the fixture and couplers; active tuning range is limited by the available power of the feedback amplifier): if the results agree the system is accurate.