Directional power meters are connected between source and load and measure the power flow in both directions. The power applied to the load and the reflection can thus be measured.
Compared to low-cost instruments, power meters like NRT provide a number of benefits: most importantly high measurement accuracy through excellent directivity and a measurement method that determines the average power like a thermal power meter.
The instruments thus provide correct measurement results even in case of modulation or in the presence of several carriers. Power Sensors NRT-Z feature low insertion loss, very good matching and excellent intermodulation characteristics: the signal to be measured is virtually unaffected, the sensor is fully transparent.
- For mobile use, service, development, production and quality management
- Digital sensor interface
- Sensor operation directly on PC
Directional power meters are used to measure power and reflection under operational conditions. Typical applications are in installation, maintenance and monitoring of transmitters, antennas and RF generators in industrial and medical fields.
Power Sensors NRT-Z can be used as self-contained measuring instruments with digital interface even without the basic unit. In addition to a directional coupler and analog section, they comprise a processor kernel for control of the hardware and remote interface and for processing the measured data (temperature compensation, linearisation, zeroing and frequency-response correction). This compact concept allows a ensures of measurement functions without the restrictions of conventional analog solutions.
Average power (rms value)
This measurement function returns for any type of test signal - whether modulated, unmodulated or several carriers - the average value of he power, ie a result as provided by a thermal power meter. It features a measurement range of 35 dB to 40 dB as well as high measurement accuracy.
Peak envelope power (PEP)and crest factor
These two parameters provide information on the peak power of a modulated envelope and thus describe the overdrive characteristics of transmitter output stages.The result of the crest factor measurement is referred to the average power and read out in dB.The measurements are carried out with a video band width adjustable in several steps and allow determination even of short-time, high power peaks generated, for example, by CDMA base stations.
Average burst power
This function can be used for measuring modulated and unmodulated bursts.The measurement is based on the average power and the duty cycle,which may be defined by the user or determined automatically by the power sensor.
Complementary cumulative distribution function (CCDF)
This function measures he probability of the peak envelope power exceeding a preset threshold so that the amplitude distribution of transmitted signals with non-determined envelope can be determined.
Matching
The power sensor calculates the matching of he load from the average values of forward and reverse power.This parameter can be output in all
common representations - as return loss, SWR, reflection coefficient or power ratio in %.Since the reverse power measurement channel is 10 dB more sensitive than the forward channel, matching measurements can already be made at very low powers.
Excellent shielding
The power sensors feature excellent shielding so that emissions from the microprocessor or from the digital data stream on the connecting cable are completely blocked out. Any radiated emissions at he RF connectors are below thelimit of detection. The excellent intermodulation characteristics keep unwanted frequency components resulting from the insertion of the power sensor to a minimum. These are all good reasons to use NRT-Z sensors not only for esting but also in fixed installations.
Direct power monitoring on PC
This is the most economical way of performing high-precision power and reflection measurements with Power Sensors NRT-Z. Via Interface Converters NRT-Z3 and NRT-Z4, the two sensors can be operated on the serial RS-232 or PC Card interface of any PC. In addition to purely remote-controlled applications, eg power monitoring in transmitter stations and EMC test systems, this solution is ideal where the data are to be collected by a computer. This may be in the development laboratory as well as in the maintenance of base stations, where in addition to power and reflection other parameters have to be measured and recorded.
A Windows user interface (V-NRT,supplied with the sensors) is available for all these applications. This program allows setting of all the available measurement functions as well as display and storage both of individual results and of whole measurement series.
Measurement directly on PC
While conventional power sensors can only be used in conjunction with a base unit, the NRT family is a step further ahead: the sensors are self-contained measuring instruments which are able to communicate with the base unit or with a PC via a standard serial data interface.
Apart from the possibility of operating the sensor directly at the RS-232 or PC Card interface of a PC, this concept provides a number of further benefits: practically maintenance-free base unit, high immunity to radiated interference - an important feature for measurements in the near field of antennas - and remote operation over very long distances (up to 500 m).