**A Comprehensive Analysis of the ADL5920ACPZ TruPwr™ RMS Detector for High-Frequency Applications**

**Introduction**

The accurate measurement of signal power is a cornerstone of modern high-frequency system design, impacting performance in everything from cellular infrastructure to test and measurement equipment. Traditional peak detectors often fall short as they fail to account for complex modulated signals with high peak-to-average power ratios (PAPR). True root mean square (RMS) detection is essential for obtaining a precise measure of a signal's actual power content. The **ADL5920ACPZ from Analog Devices** represents a significant advancement in this field, integrating a high-performance, broadband TruPwr™ RMS detector and a precision differential amplifier into a single, compact solution. This article provides a comprehensive analysis of its architecture, key features, and its critical role in high-frequency applications.

**Architecture and Operating Principle**

The ADL5920ACPZ is engineered to deliver true RMS response, meaning its output voltage is directly proportional to the RMS value of the input signal, regardless of the waveform's shape. This is a fundamental improvement over logarithmic amplifiers or peak detectors, which require correction factors for non-sinusoidal signals.

The IC operates over an impressive frequency range from **9 kHz to 6 GHz**, making it exceptionally versatile. Its core consists of a proprietary RMS detection cell. This cell computes the true power of the input signal by performing an implicit squaring, averaging, and square-root function. The device features a single-ended 50 Ω input, simplifying integration into standard RF lines. A key architectural advantage is its integrated differential amplifier, which buffers and scales the RMS core's output, providing a flexible, ground-referenced voltage.

**Key Performance Characteristics and Advantages**

The ADL5920ACPZ boasts several performance metrics that make it stand out for demanding applications:

* **True RMS Accuracy:** It maintains excellent accuracy even when measuring complex modulated signals like 5G NR, Wi-Fi 6/6E (OFDM), and wideband CDMA, where **high peak-to-average power ratios (PAPR)** are common. This ensures power measurements reflect true power, not just peak amplitude.

* **Broad Dynamic Range:** The detector offers a wide **dynamic range of up to 40 dB** (typically from -34 dBm to +6 dBm at 2.5 GHz), allowing it to handle both weak and strong signals without external attenuation or amplification in many cases.

* **Temperature Stability:** A critical feature for robust field performance is its insensitivity to temperature fluctuations. The device exhibits minimal variation in output across its operating temperature range, ensuring reliable and consistent measurements.

* **Integrated Functionality:** The inclusion of the output amplifier within the same package simplifies design, reduces component count, and saves valuable board space. The amplifier's gain can be configured externally, offering design flexibility.

**Applications in High-Frequency Systems**

The combination of bandwidth, accuracy, and integration makes the ADL5920ACPZ ideal for a multitude of high-frequency scenarios:

1. **Transmit Power Control and Monitoring:** It is perfectly suited for closed-loop power control in base stations, small cells, and radio transceivers, ensuring transmitted power remains within strict regulatory limits.

2. **Return Loss Measurement (VSWR):** When used in conjunction with a directional coupler, it can accurately measure forward and reflected power, enabling real-time system health monitoring and antenna VSWR calculation.

3. **Automatic Gain Control (AGC) Loops:** Its fast response time and true RMS output make it an excellent sensing element for AGC circuits in communication systems, maintaining consistent signal levels.

4. **Test and Measurement Equipment:** The detector serves as a critical component in spectrum analyzers, power meters, and other instrumentation requiring accurate, broadband power measurement.

**Design Considerations**

While highly integrated, successful implementation requires attention to several factors. **Proper PCB layout is paramount;** the input RF trace must be a controlled 50 Ω impedance line with minimal discontinuities. Adequate decoupling on the supply pins is essential to prevent noise and ensure stable operation. Furthermore, the selection of external gain-setting resistors for the output amplifier must be precise to achieve the desired output scaling and accuracy.

**ICGOODFIND**

**ICGOODFIND**: The ADL5920ACPZ TruPwr™ RMS Detector is a superior integrated solution for engineers demanding **true power measurement accuracy** in high-frequency designs. Its ability to handle complex modulated signals, combined with its broad bandwidth, wide dynamic range, and high level of integration, establishes it as a critical component for advancing performance in telecommunications, aerospace, and test and measurement systems. It effectively eliminates the guesswork and calibration burdens associated with less sophisticated detection methods.

**Keywords**: RMS Power Detection, High-Frequency Applications, Broadband Detector, Power Measurement, ADL5920