Accurate measurement of RF and microwave signal power

Linear Technology Korea (CEO Hong Sa-kwak) has launched the LTC5596, an RMS power detector characterized by high frequency, broadband, and wide dynamic range capabilities.

The product can accurately measure the power of RF and microwave signals regardless of modulation and waveform. The LTC5596 responds with a convenient log-linear 29mV/dB to signal levels ranging from –37dBm to –2dBm at precision levels of ±1dB error or less across the entire operating temperature range and RF frequency range (200MHz to 30GHz).

In addition, the response characteristics of this device provide ±1dB flatness across this frequency range. A wider frequency range of 100MHz to 40GHz is also available, though accuracy near 40GHz is somewhat reduced. Since the RF input is internally matched to 50Ω across the 100MHz to 40GHz range, this device can be easily used in any band within the useful frequency range.

Current 4G and 5G broadband communication systems can achieve higher desired data rates by applying high-order multitone OFDM modulation. Traditionally, microwave Schottky diodes were used as detectors. However, these diodes measure only the peak of the waveform and have serious drawbacks when rectifying RF or microwave signals.

Specifically, they grossly misrepresent the actual power of the signal. Conversely, RMS detectors perform an analog root-mean-square (RMS) calculation of the waveform and calculate the average of the results to represent the actual power of the input signal regardless of modulation, number of carriers, and other variable amplitudes. This capability to measure actual power is very important for equipment manufacturers who must set appropriate transmission power to ensure maximum transmission distance, improve Tx range, and comply with power limitation regulations.

Because the LTC5596 has very wide bandwidth, it can operate seamlessly across various frequency bands using conventional designs with minimal calibration. For example, the LTC5596 works well in sub-10GHz backhaul microwave links just as it does in the 28GHz version. A single design without readjustment can provide significant cost-saving opportunities for equipment manufacturers. Furthermore, with its wide frequency range and improved sensitivity, the LTC5596 can be applied in various fields such as radar systems, aviation, wireless infrastructure base stations, satellite communications, and test equipment.

The LTC5596 operates from a single 3.3V supply voltage and typically consumes 30mA of current. It also incorporates enhanced ESD protection. All pins can withstand HBM (human body model) discharge up to 3,500V. Currently two temperature grades are available, with Grade I operating from –40°C to 105°C.

For applications exposed to high-temperature operating environments such as high-power RF power amplifiers, Grade H (high temperature) is provided with an operating temperature range of –40°C to 125°C. Grade H has undergone complete 100% testing across the full temperature range, and very tight tolerances at slope and intercept are guaranteed, reducing part-to-part variation. Both temperature versions are supplied in a 2mm x 2mm plastic 8-pin DFN package.

The LTC5596 Grade I starts at $12.50 per unit at quantities of 1,000.