Patent Application
20080143319
One of the output ports is connected through an Agilent 8481A Power Sensor 105 and to an Agilent E4418B Power Meter 107. Agilent is a trademark of Agilent Technologies, Inc. of Santa Clara, Calif., USA.
The Agilent 8481A is a thermocouple-based sensor. Thermocouple power sensors are thermal-based power sensors. Thermal-based power sensors are true “averaging detectors” and in addition to thermocouple power sensors also include bolometer (thermistor or barretter) power sensors. They convert an unknown RF power to heat and detect that heat transfer. In other words they measure heat generated by the RF energy.
The other output port is connected to another device such as a spectrum analyzer or frequency detector 109.
One problem with this prior-art method is that the separate components need to be specified and calibrated separately. Also, the power measuring sensitivity of the power sensor 105 and power meter 107 is not optimized.
It would be desirable to combine a power sensor with a power distributor, such as a power splitter or power divider, so as to provide more accurate measurements with less calibration, as well as greater sensitivity of power measurement.
The present invention provides a single device which incorporates a power sensor within an arm of a power distributor.
A power-sensor module comprises a housing enclosing the power-sensor module. An input port of the housing brings an input signal into the housing. A power distributor, for example a power divider or power splitter, is within the housing. The power distributor has a first arm transmitting a first portion of the input signal and a second arm transmitting a second portion of the input signal. A first resistor is in the first arm and a second resistor in the second arm of the power distributor. An output port of the housing outputs from the housing the first portion of the input signal. A first thermal-based power detector detects heat generated by the second resistor caused by the second portion of the input signal and outputs a first power measurement signal based on the heat detected. An analog-to-digital converter within the housing converts the first power measurement signal to a digital signal. The digital signal is output from a digital output port of the housing for outputting the digital signal or transmitted by a transmitter. The input signal, the first portion of the input signal and the second portion of the input signal can be RF signals.
Further preferred features of the invention will now be described for the sake of example only with reference to the following figures, in which:
A portion of the power of the input signal 206 received by the input port 205 passes through the power-sensor module 201 and is output at an output port 209 of the power-sensor module 201 as a signal 210. The signal 210 is generally the same as the input signal 206 (for example it has the same frequency characteristics) but has attenuated power. The output port 209 sends the signal 210, via a transmission media 211, to a measurement device 213, such as a spectrum analyzer, frequency meter or other RF or optical frequency device for measuring a parameter of the signal. The power measurement device 213 can be an Agilent PSA Series E4448A Spectrum Analyzer, for example. The transmission media 211 can be cable, waveguide, or other media.
A power measurement signal 217 is output from an output port 215 and is transmitted to the measurement device 213 via a transmission media 219. The power measurement signal 217 contains information indicative of the power of the input signal 206 received by the input port 205. The power measurement signal 217 can be formatted and output from the power sensor module 201 using protocols such as USB, Ethernet, LAN, RS232, IEEE 1394, GPIB, HPIB, VXI, PCI Express, PCI, PXI, LXI, PCMCIA or others as known in the art.
Alternatively, the output port 215 can be a transmitter and the signal 217 can be transmitted through the air to a receiver at the measurement device 213. In this case the wireless format can be WiFi, WUSB or IrDA.
In the case where the measurement device 213 is a Spectrum Analyzer, the power measurement signal 217 can serve as an absolute reference for power measurement.
The first arm 305 outputs the first signal portion 210 from the output port 209 of the housing 202.
The power distributor 301 shown in
Another resistor, 319 can also be in the second arm 307. Typically, in a two-resistor power splitter 301, the output port 209 is terminated in 50 ohms. For example, the output port 209 might be terminated with a transmission media 211 consisting of a 50 ohm coaxial cable and a measurement device 213 having a 50 ohm characteristic impedance. The resistors 313, 315 can also be 50 ohms. If the resistor 319 is 50 ohms as well, then an equal amount of power will pass through each of the arms 305, 307.
In another embodiment the power distributor 301 can be a three-resistor power divider having an additional resistor in the input arm 303. The three-resistor power dividers are useful for power monitoring applications, or other applications where it is necessary to divide power equally on a uniform transmission line.
A first power sensor 309 is in the second arm 307 of the power distributor 301. The first power sensor 309 receives the second signal portion 311 and produces the power measurement signal 217 which is output from the output port 215 of the housing 202.
The first power sensor 309 can be a thermal-based power detector serving as a true “averaging detector” and can be, for example, a thermocouple detector, a thermistor detector or a barretter detector. The thermal-based power detectors convert an unknown RF power to heat and detect the heat transfer. In other words they measure heat generated by the RF energy. Other types of average power measurement detectors can also be used.
The first power sensor 309 can use an RF thermocouple detector including one or more thermocouple units, forming a “thermopile” 317, and coupled on a unitary substrate. Each thermocouple unit consists of a pair of thermocouples in series, one nominally “hot” and the other nominally “cold”. In
The thermopile 317 can just as well be associated with the resistor 319 rather than the resistor 315 to detect the heat generated by the resistor 319.
By utilizing a resistor of the power distributor 301 as part of the first power sensor 309, the calibration of the power sensor module 201 is greatly simplified and the accuracy is increased.
The first power sensor 309 can be calibrated similarly to a traditional power sensor, such as the power sensor 105 of
The power distributor 401 of
The power distributor 501 of
The resistor configurations of the power distributors 401, 501 of
In prior-art power-distributors, the resistors within the output arms are not used for power sensors such as the first power sensor 309. Thus, the power sensor measurement is made based on at most only one-quarter of the input power and potential sensitivity is lost.
In the embodiment of
In the embodiment of
Thus, the embodiments of
In other embodiments combinations of different types of power sensors can be used within the power sensor module 201. For example, the second power sensor 403 can be any type of thermal-based or diode-based sensor. Also, in
Including the power meter section 321 within the power-sensor module 201 avoids the extra size, weight and cost of using external power meter such as the power meter 105 of
In other embodiments the power meter section 321 is external to the power-sensor module 201 and outside of the housing 202. In general the signal 217 can be of a format typically output by RF power sensors or of a format typically output by RF power meters, as known in the art. When the signal 217 has a format typically output by RF power sensors, then the signal 217 can be output from the output port 215 and then travels through transmission media 219 to an external power meter which can be a typical power meter such as the power meter 105 of
In yet another embodiment, the first arm 305 of the power distributor 301 of
Including power sensors in both the first arm 305 and second arm 307 of the power distributor 301 can help to determine the match of the load on the output port 209. The proportion of power delivered to the arm 305 compared to that delivered to the arm 307 is dependant upon the load presented at the output port 209. Under the ideal conditions of a perfect 50 ohm load on the port 209, the sensors on the first and second resistor 313, 315 would measure the same power. Or alternatively, for the embodiments of
In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
