RF Power Measurement
ADI's huge portfolio of logarithmic and RMS-DC-based RF detectors enable low-cost measurement of sine-waves and complex waveforms from low frequency to microwaves and everywhere in between. Coupled with ADI’s portfolio of ADCs and embedded processors, these solutions allow solutions from bench to handheld.. In addition, ADI offers a family of ARM Cortex-M3-based single-chip solutions incorporating high resolution ADCs suitable for a variety of handheld and portable applications.
The ADL6010 is a versatile, broadband envelope detector covering the microwave spectrum. It provides state-of-the-art accuracy with very low power consumption (8 mW) in a simple, easy to use 6-lead format. The output is a baseband voltage proportional to the instantaneous amplitude of the radio frequency (RF) input signal. It exhibits minimal slope variation of the RF input to envelope output transfer function from 0.5 GHz to 43.5 GHz.
The detector cell uses a proprietary eight Schottky diode array followed by a novel linearizer circuit that creates a linear voltmeter with an overall scaling factor (or transfer gain) of nominally ×2.2 relative to the voltage amplitude of the input.
Although the ADL6010 is not inherently a power responding device, it remains convenient to specify the input in this way. Thus, the permissible input power, relative to a 50 Ω source input impedance, ranges from −30 dBm to +15 dBm. The corresponding input voltage amplitudes of 11.2 mV to 1.8 V generate quasi-dc outputs from about 25 mV to 4 V above common (COMM).
A subtle aspect of the balanced detector topology is that no even-order distortion, caused by nonlinear source loading, occurs at the input. This is an important benefit in applications where a low ratio coupler is used to extract a signal sample and is a significant improvement over traditional diode detectors.
The power equivalent of a fluctuating RF input amplitude can be extracted by the addition of an rms-to-dc converter IC. Alternatively, the baseband output can be applied to a suitably fast analog-to-digital converter (ADC) and the rms value (and other signal metrics, such as peak to average ratio) calculated in the digital domain.
The output response accuracy is insensitive to variation in the supply voltage, which can range from 4.75 V to 5.25 V. The ultralow power dissipation contributes to its long- term stability.
The ADL6010A is specified for operation from −40°C to +85°C, and the ADL6010S is specified for operation from −55°C to +125°C. Both are available in a 6-lead, 2 mm × 2 mm LFCSP package.Applications
- Microwave point to point links
- Microwave instrumentation
- Radar-based measurement systems
The ADL5513 can be configured to provide a control voltage to a power amplifier or a measurement output from the VOUT pin. Because the output can be used for controller applications, special attention has been paid to minimize wideband noise. In this mode, the setpoint control voltage is applied to the VSET pin. The feedback loop through an RF amplifier is closed via VOUT, the output of which regulates the amplifier output to a magnitude corresponding to VSET. The ADL5513 provides 0 V to (VPOS − 0.1 V) output capability at the VOUT pin, suitable for controller applications. As a measurement device, VOUT is externally connected to VSET to produce an output voltage, VOUT, that increases linear-in-dB with RF input signal amplitude.
The logarithmic slope is 21 mV/dB, determined by the VSET interface. The intercept is -88 dBm (referred to 50 Ω, continuous wave input, 900 MHz) using the INHI input. These parameters are very stable against supply and temperature variations.
The ADL5513 is fabricated on a SiGe bipolar IC process and is available in a 3 mm × 3 mm, 16-lead LFCSP package for the −40°C to +125°C operating temperature range. A fully populated evaluation board is available.
The ADL5902 is a true rms responding power detector that has a 65 dB measurement range when driven with a single-ended 50 Ω source. This feature makes the ADL5902 frequency versatile by eliminating the need for a balun or any other form of external input tuning for operation up to 9 GHz.
The ADL5902 provides a solution in a variety of high frequency systems requiring an accurate measurement of signal power. Requiring only a single supply of 5 V and a few capacitors, it is easy to use and capable of being driven single-ended or with a balun for differential input drive. The ADL5902 can operate from 50 MHz to 9 GHz and can accept inputs from −62 dBm to at least +3 dBm with large crest factors, such as GSM, CDMA, W-CDMA, TD-SCDMA, WiMAX, and LTE modulated signals.
The ADL5902 can determine the true power of a high frequency signal having a complex low frequency modulation envelope or can be used as a simple low frequency rms voltmeter. Used as a power measurement device, VOUT is connected to VSET. The output is then proportional to thelogarithm of the rms value of the input. In other words, the reading is presented directly in decibels and is scaled 1.06 V per decade, or 53 mV/dB; other slopes are easily arranged. In controller mode, the voltage applied to VSET determines the power level required at the input to null the deviation from the set point. The output buffer can provide high load currents.
The ADL5902 has 1.5 mW power consumption when powered down by a logic high applied to the PWDN pin. It powers up within approximately 5 μs to its nominal operating current of 73 mA at 25°C. The ADL5902 is supplied in a 4 mm × 4 mm, 16-lead LFCSP for operation over the wide temperature range of −40°C to +125°C.
The ADL5902 is also pin-compatible with the AD8363, 50 dB dynamic range TruPwr™ detector. This feature allows the designer to create one circuit layout for projects requiring different dynamic ranges. A fully populated RoHS-compliant evaluation board is available.
- Power amplifier linearization/control loops
- Transmitter power controls
- Transmitter signal strength indication (TSSI)
- RF instrumentation