Combilog Hybrid Antennas

What is a CombiLog Antenna?

CombiLog antennas represent an advanced hybrid antenna design that combines the best characteristics of two fundamental antenna types: biconical antennas and log-periodic antennas. This innovative fusion creates a single, broadband antenna solution capable of covering an exceptionally wide frequency range that would otherwise require multiple separate antennas.

Technical Design Principles

The CombiLog hybrid design integrates:

• Biconical Elements (Low-Frequency Coverage): The bow-tie or biconical elements handle lower frequencies, typically from 20-30 MHz up to several hundred MHz. These elements provide omnidirectional radiation patterns in the horizontal plane and excellent bandwidth characteristics at lower frequencies.
• Log-Periodic Array (High-Frequency Coverage): The log-periodic dipole array extends coverage into the higher frequency ranges (hundreds of MHz to several GHz). This design offers consistent gain and impedance characteristics across its operating bandwidth through geometric scaling of dipole elements.
• Common-Mode Chokes: Strategically installed ferrite cores or balun structures suppress unwanted common-mode currents on the outer conductor of the coaxial feed line. This critical feature ensures accurate measurements by minimizing cable radiation and maintaining antenna pattern integrity.
• Modified Feed Network: The feed lines are engineered to seamlessly transition between the biconical and log-periodic sections, maintaining consistent 50Ω impedance and minimizing VSWR across the entire frequency range.

Advantages in EMC Testing

CombiLog antennas offer significant advantages for electromagnetic compatibility (EMC) testing:

• Wide Frequency Coverage: A single antenna covers frequency ranges that would typically require 3-4 separate antennas (biconical, log-periodic, horn antennas), reducing equipment costs and test setup time.
• Compliance with Standards: Meets stringent antenna balance/symmetry requirements (±1 dB) specified in ANSI C63.5 and CISPR 16-1-4 standards, ensuring accurate and repeatable measurements.
• Dual Functionality: Serves as both a receiving antenna for emissions testing and a transmitting antenna for immunity testing, providing versatility in test laboratory applications.
• Excellent Cross-Polarization Rejection: Minimizes interference from unwanted polarizations, improving measurement accuracy in complex electromagnetic environments.
• Linear Polarization: Can be quickly rotated between horizontal and vertical polarizations to measure both polarization components of radiated emissions.

Product Comparison: AC-220 vs ACL-6000

Application-Based Selection Guide

Key Differences Summary

Choose the AC-220 if you:

• Primarily test products operating below 2 GHz
• Conduct automotive, industrial, or consumer electronics compliance testing
• Need a cost-effective solution for standard EMC requirements
• Work with traditional wireless technologies (WiFi 2.4 GHz, Bluetooth, older cellular)

Choose the ACL-6000 if you:

• Test modern wireless devices operating in 5 GHz WiFi bands
• Work with 5G sub-6 GHz technology or UWB devices
• Need extended frequency coverage for comprehensive compliance testing
• Want to future-proof your test capabilities for emerging wireless standards
• Require emissions testing capability above 2 GHz

Product Descriptions

ACL-6000 CombiLog Hybrid Antenna

The ACL-6000 CombiLog is a hybrid antenna with linearly polarized bandwidth. Simply stated, hybrid antennas are log periodic antennas with modified feed lines that include a set of low frequency antenna elements. Moreover, common-mode chokes are commonly installed to reduce common-mode currents flowing on the outer conductor of the coaxial feed line/receiver cable. A hybrid antenna can typically encompass, at a minimum, the frequency range of the combined antenna types by essentially combining a log periodic and biconical antenna.

As a receiving antenna, the ACL-6000 operates from 30 MHz to 6 GHz, and as a transmitting antenna, it operates from 80 MHz to 6 GHz.

The ACL-6000 is a qualification-level EMI test antenna for measuring regulatory conformance in accordance with the vast majority of regulatory requirements.

The ACL-6000 is similarly suitable for use as a transmitting antenna for product immunity tests within the frequency range of 80 MHz to 6 GHz. The ACL-6000 can also be used for test site comparisons, shielding effectiveness evaluations of large enclosures, field monitoring, site surveys, and other similar applications.

AC-220 CombiLog Antenna

The AC-220 CombiLog is a broadband, linearly polarized hybrid antenna. Hybrid antennas are, put simply, log periodic antennas with the feed lines modified to include a set of low frequency antenna elements, commonly referred to as "bow-tie" elements. Additionally, common-mode chokes are typically installed to reduce common-mode currents flowing on the outer conductor of the coaxial feed line/receive cable. By essentially combining a log periodic and biconical antenna, a hybrid antenna can typically cover, at a minimum, the frequency range of the combined antenna types.

The AC-220 operates from 20 MHz to 2 GHz as a receiving antenna. Using typical conventional antennas, four separate antennas would be needed to cover the same frequency range.

The AC-220 CombiLog Antenna is suitable for use as an EMI test antenna for qualification-level regulatory compliance measurements as per most regulatory requirements.

The AC-220 is equally suitable for use as a transmitting antenna over the frequency range of 80 MHz to 2 GHz. The antenna is driven by an RF power amplifier for the purpose of establishing radiated RF fields for product immunity tests. It is capable of handling power levels up to 500 Watts.

Notwithstanding the above applications, the AC-220 can also be used for test site comparisons, shielding effectiveness tests of large enclosures, field monitoring, site surveys, etc.