The 100MHz that provides 35dB dynamic range comes LTC5596 of radiodetector of power of RMS of 40GHz logarithm linear is a power type is answered to the Rms between 40 GHz in 100 MHz integrated circuit, cost is lower, size is smaller, detect limits is in 35 DB or above, can use at making hand-held broadband powermeter, perhaps serve as embedded powermeter loads circuit in.

 

LTC5596 uses the linear DB that can accuse transfer function, have outstanding frequency evenness to spend, easily calibration – be like individual intermediate frequency calibration is general at 2 o’clock fundamental calibration, come in 150 MHz inside limits of 30 GHz frequency, measure precision to be ±1 DB. LTC5596 has low power comsumption (only 100 MW) with compositive character, because this can be used in circuit and solution of monitoring of hand-held power source.

 

Graph 1 in the give typical examples of power source power supply can explain plan of this a complete set of is quite simple, among them, broadband RF powermeter can be used already some LTC5596 demonstrate circuit (monitor of DC2158A) , I2C LCD, and board compose builds the DC2026C Linduino that runs small firmware program.

 

 

Graph 1. Complete broadband RF powermeter.

  

Circuit is assembled

 

Graph 2 showed outfit recipe case. Linduino board many ADC input is included in imitate IN batteries, here uses A0 to regard introduction of give typical examples as the output of LTC5596 radiodetector. This monitor uses interface of I 2 C, simplified with Linduino board the join between. Whole circuit passes Linduino board auxiliary port power supply, include LTC5596 board with connector.

 

Graph 2. Join graph.

 

Firmware

 

All needs firmware are in Linduino board on move. The main function of firmware is the imitate input that will measure (V) changeover is RF power (DBm) , show on LCD monitor. To accomplish this, we suggest to use at 2 o’clock calibration law, slope and check point —— find on the linear transfer function of LTC5596 with linear form denotive VOUT mixes RF power:

 

 

Among them, x expresses power input (DBm) , the output tension that Y shows LTC5596 (VOUT) , with ADC number the code becomes direct ratio, m expresses slope, b states X cut is nodded (VOUT is achieved 0) . Firmware is calculated according to the Y that measures income X, the value of B and M comes from at calibration. Take average to be able to help the effect that the smallest vocal cords that change a confusion of voices comes to to many reading.

 

Of Linduino board carry ADC to be 10 resolution, with the LSB dimension correspondence that makes an appointment with 4.9 MV. The typical slope of LTC5596 is 28.5 MV/dB, because this measures resolution,be 0.2 DB about. The firmware code give a demonstration that the appendix shows is used below 5.8 GHz, use at showing power input (DBm) .

  

Calibration

 

Although LTC5596 used linear DB transfer function. But the difference between parts of an apparatus can be brought about appear slope of many transfer function and axial check point. Because transfer function is linear, calibration is very so simple, need to use only at 2 o’clock calibration (if need, use many bits of calibration) can ensure accuracy.

 

Graph 3 showed those who be aimed at a model to deliver a curve at 2 o’clock calibration, this curve is the curve of the LTC5596 when 5.8 GHz. Was used at begging to take slope and X cut place this at 2 o’clock.

 

Graph 3. LTC5596 VOUT and power input. Two calibration of the choice are nodded should the working range that can represent application.

 

In this exemple,

 

 

In these slope and the digital yard that cut chooses a value to be used at appendix place to show.

  

Linear error

 

In data manual, logarithm check point is the X check point in pointing to a graph. Linear error is the difference between the power that points to ideal to be measured actually with radiodetector point-blank. Practicable detects limits is the limits that shows linear error is less than 1 DB commonly. Accordingly, can use the X cut drop that the graph shows 4 times and slope to calculate error, what this shows is to use school is punctual at 2 o’clock, the linear error of the typical facility that the system can obtain.
 

Graph 4. After calibration, the error of LTC5596 and power input. Linear and dynamic limits comes for –40 DBm about + 3 DBm.

 

Conclusion

 

LTC5596 bulk is very small, simple, and needs power comsumption is low, come in 100 MHz inside 40 GHz limits, the RF power that can achieve essence of life to allow is measured. It lets complete solution have cabinet, efficient the characteristic that allows with essence of life, enough satisfies the requirement that holds portable RF powermeter, can put circuit even in, as embedded RF powermeter.

 

Because LTC5596 has transfer function of outstanding linear DB broadband, firmware expense reachs minimum. Calibration can take frequency in individual intermediate frequency at 2 o’clock next undertaking, have pretty good accuracy; Also can fall in much frequency undertake, in order to raise accuracy.

 

More important is, why to no matter use,plant modulation means, LTC5596 Rms radiodetector can accurate measure power. Even if simple at 2 o’clock calibration, as a result quite accurate also —— takes no account of the circumstance of modulation weaveform to fall, the error is less than 0.3 DB. To it contrary, the commercial equipment with other high price needs concentrated calibration and character to determine.