Ultra Wideband Metal Composite Inductor 1800nH Broadband RF Choke 10MHz - 20GHz

Product Specification

Product Overview

The HALT60008 is a broadband conical inductor designed for RF decoupling and bias tee applications spanning 10 MHz to 20 GHz. It delivers 1800 nH (1.8 µH) of nominal inductance through a continuously tapered conical winding wound with 0.08 mm fine copper wire. The component is rated for 500 mA continuous DC current and operates over an industrial temperature range of -55°C to +125°C.

Complete Technical Specifications

Why 1800 nH with a Conical Winding

In standard bias networks, achieving broadband isolation requires cascading a large-value inductor for low frequencies with a small-value inductor for high frequencies. The junction between these components forms a parasitic LC tank circuit that resonates within the operating band, producing a sharp transmission dip. The HALT60008 eliminates this problem by delivering 1800 nH of blocking inductance in a single component with a tapered conical architecture.

The conical winding distributes parasitic turn-to-turn capacitance along a mechanical gradient rather than concentrating it at one electrical node:

• Apex (Narrow End): Connected to the 50-Ω microstrip line. The small turn diameter minimizes shunt capacitance at the signal junction, preserving high-frequency transmission.
• Base (Wide End): Accumulates the 1800 nH inductance needed to block signals down to 10 MHz.
• Tapered Transition: The continuous change in diameter spreads parasitic capacitance spectrally. There is no discrete self-resonant peak—only a smooth, predictable impedance roll-off.

Multi-Frequency Operational Performance

Each HALT60008 is verified on a calibrated vector network analyzer using microstrip calibration fixtures with TRL de-embedding to move the reference plane to the component leads:

0.08 mm Wire: The Balance Between Current and Bandwidth

The 0.08 mm (80 µm) wire diameter is chosen to balance two competing requirements. The larger cross-section compared to 0.05 mm ultra-fine wire reduces DC resistance, enabling a 500 mA continuous current rating—2.5 times the capacity of micro-wire designs. The trade-off is moderately higher inter-turn parasitic capacitance, which sets the upper frequency at 20 GHz. For applications operating below 20 GHz that require higher current handling, this configuration provides optimal performance.

The air-core topology eliminates magnetic core saturation, ensuring the full 1800 nH inductance is maintained regardless of DC bias current level. Unlike ferrite chokes that lose effective inductance as current increases, the HALT60008’s inductance is determined solely by winding geometry.

Assembly Quick Reference

1. Orientation: Cone tip (small end) perpendicular (≈90°) to the RF transmission microstrip line.
2. Lead Trim: Keep the apex flying lead between solder fillet and first turn as short as possible, ideally ≤0.3 mm. Excess lead length adds series parasitic inductance.
3. Base Connection: Solder the wide end to the DC bias pad. Place bypass capacitors within 1 mm to minimize inductive loop area.
4. Epoxy Fixation (mandatory): Apply a micro-dot of non-conductive, low-outgassing epoxy (Epotek H70E or H65) on the winding side to prevent microphonic modulation.
5. Soldering: Controlled micro-soldering tip temperature 280–320°C, dwell time ≤3 seconds. Compatible with SAC305, AuSn eutectic, and PbSn solder alloys.

Primary Applications

• High-current broadband bias tees for GaN power amplifier drain bias
• DC feed networks in high-power 100G/400G optical transceivers
• RF decoupling in X-band and Ku-band radar transmitter modules
• PIN diode switch and step attenuator DC return paths
• Phased-array antenna element bias distribution
• Microwave test and measurement bias networks

Frequently Asked Questions

Q: Why does a single 1800 nH conical inductor work where cascading multiple inductors fails?
A: Cascading a large-value inductor with a small-value inductor creates a parasitic LC tank at their junction, producing a sharp resonant transmission dip in the microwave band. The HALT60008 combines high inductance with a tapered conical architecture, achieving continuous, resonance-free isolation from 10 MHz to 20 GHz in a single component with no junction parasitics.

Q: How does the 0.08 mm wire affect performance compared to 0.05 mm variants?
A: The 0.08 mm wire has a larger cross-section, reducing DC resistance and enabling 500 mA of continuous current. The trade-off is increased inter-turn surface area, which raises parasitic capacitance and sets the upper frequency at 20 GHz. For applications operating below 20 GHz that need higher current, this is the preferred configuration.

Q: Is S-parameter simulation data available?
A: Yes. A .s2p Touchstone file (10 MHz–20 GHz, fixture-de-embedded to the component lead reference plane) is available on request. Hoan also provides 3D STEP mechanical models and parameterized EM simulation models for PCB co-design.