APN-16-8-001/A/CA Page 1 of 4

Implementation of Antenna Diagnostic Compatibility for Taoglas Antennas

AntD© (pronounced ant-dee)

AntD© consists of measuring the voltage drop across a resistor embedded in the antenna to

detect if an antenna is present or not, as well as several types of cable damage, including being

severed or crushed. How this circuitry is implemented on the product is up to the designer, but

it always requires the antenna to provide a consistent and known DC resistance for any circuitry

to work. There are also certified off-the–shelf cellular AntD modules that have the function

inbuilt and Taoglas has off the shelf antennas that are compatible for each model.

Historically, different antenna architectures may be naturally a DC short or a DC open. These 2

extremes however are symptoms of a cut or crushed cable respectively, so there needs to be a

middle ground. AntD© ensures that regardless of the antenna architecture, a 10k DC resistance

is shown at the antennas connection point. The exact implementation circuit inside the antenna

changes with the antenna architecture but always results in the following equivalent circuit:

Figure 1 - Equivalent schematic for AntD© compatible passive antennas

APN-16-8-001/A/CA Page 2 of 4

An example circuit is shown below for implementing measurement with a simple microcontroller.

This functionality can be implemented using any A/D converter and digital logic output. This

includes the A/D converters in some radio modules. The module suppliers for instance have

references on how to use the A/D’s in their cellular modules to accomplish the same

measurement. While their circuits differ a little they accomplish the same result. The most

stable measurement results will happen when the radio is not transmitting.

Figure 2 - Example Host Micro AntD© Cellular Implementation including 2.1GHz

Note that the circuit stays the same regardless of the frequencies used, but some of the values

would change. The inductor needs to have a self-resonant frequency higher than any of the

frequencies used, while having impedance at the lowest frequency used of 300-500 ohms

minimum. This typically requires a proper RF inductor, such as the Murata LQW15 series. The

33pF caps would change in value for optimum performance at a particular frequency as well.

Consult the vendor’s design tools for selection.

To use the circuit, apply a voltage by setting the digital output high. A simple resistive divider is

then formed between the series 10k resistor and the 10k resistor in the antenna. Measure the

voltage in the middle of the divider with the A/D converter. The 10k resistor and 10nF cap form

a filter, which should provide for consistent DC values. The sensing voltage can be left on all the

time, or set high only as needed, to minimize power consumption.