The linearity of an RF or microwave receiver is typically measured at its intermediate frequency. Nonlinearities at high signal levels due to mixer compression, and at low levels due to noise, are then specified as maximum error figures. This application note shows how linearity can be measured over a frequency range of 100kHz to 40GHz using a precision power meter and RF power standards.
AN208: Microwave Receiver Linearity Verification
Conventional calibrations typically take place in the 1mW to 10mW range. This range can be extended downwards for highly sensitive diode sensors by means of a calibrated attenuator. Raising the calibration level above 10mW is more of a challenge. This application note describes a basic technique for generating an accurate 100 mW power source.
AN212: Constructing a 100mW RF Power Reference
Both VSWR and Return Loss are a measure of the divergence of a microwave device from a perfect impedance match. They are mathematically interchangeable and result from scalar measurements. This app note describes the use of a TEGAM System IIA Power Sensor Calibration System for VSWR and Return Loss measurements.
AN213: Return Loss and VSWR Measurement Methods
There are many different types of temperature compensated thermistor mounts such as the Agilent 478A and 8478A. Type IV power meters such as Tegamâ€™ s 1806A, 1804, and 1806 can be used to monitor these thermistor mounts.
Characterizing RF power sensors is commonly done using a direct comparison system which employs a resistive RF power splitter with a power standard connected to a power meter. The microwave source is often maintained at a stable level with an external AM input. This application note discusses the limitations to this technique and some alternatives.
AN216: Limitations of AM Leveling Loops
This document explains the theory behind measuring power with a dual bridge Power Meter such as the Agilent 432A and shows the reader how to simplify the measurement with the TEGAM 1830A RF Power Meter.
Technicians and engineers use calibration factors when making measurements; but where do these calibration factors really come from?
AN218: Calculating a Calibration Factor
The TEGAM Model 1830A RF Power Meter coupled with a thermistor power sensor (also known as a thermistor mount) can accurately measure the SWR of a 50 MHz reference. By utilizing a unique function that most modern power meters do not offer; the 1830A allows the user to change the value of the thermistor mounts terminating resistance.
RF power sensor linearity is a commonly misunderstood topic. To obtain the most accurate power measurements, though, you need to understand what linearity is, the sources of nonlinearity, and how to measure the linearity of your RF power sensors.
AN220: Measuring RF Power Sensor Nonlinearity
How Accurate Are Your RF Measurements? Accurate power measurements on RF signals require a thorough knowledge of the varying nature of the signals under test. We have obtained very good results with this system, improving the uncertainty of a 100W, 1GHz flow calorimeter to 0.43% of full scale. Using this system, through-line wattmeters can be calibrated automatically with an uncertainty of 0.55%.
AN221: Coaxial Flow Calorimeter