Operation Detector Products Frequency Matthew Pilotte INTROD

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AN-691 APPLICATION NOTE
Operation Detector Products Frequency
Matthew Pilotte
INTRODUCTION Analog Devices many detector products portfolio designed operate over various frequency ranges GHz. Most these parts also perform very well frequencies down into audio band, although data sheets these parts list performance specify guaranteed operation much higher frequencies.The input frequency performance these parts summarized this application note. Plots performance included. frequency performance following parts discussed this application note: AD8302, AD8306, AD8307, AD8309, AD8310, AD8361, AD8362. (The AD8314 included because contains series capacitor input, which precludes frequency.) Using appropriate precautions, some these devices dc-coupled their inputs. external circuitry substantially determines lowest frequency which operation acceptable. These devices grouped into four general categories: demodulating logarithmic amplifiers, exponential logarithmic amplifiers, special purpose circuits employing demodulating logarithmic amplifiers, rms-to-dc converters. Table shows category into which each part falls. Table Part Number AD8302 AD8306 AD8307 AD8309 AD8310 AD8361 AD8362 Category Special Purpose Demodulating Logarithmic Amplifier Demodulating Logarithmic Amplifier Demodulating Logarithmic Amplifier Demodulating Logarithmic Amplifier rms-to-dc Converter Exponential Logarithmic Amplifier
produced straight line when plotted against input signal magnitude, expressed decibels.This straight line described data sheets slope intercept. Because these amps very sensitive, response tiny amount noise that inevitably generated input sections amps indistinguishable detector output from response very small input signals. Consequently, detected output voltage typically does when amplitude input signal goes reaches lower limit that typically sub-300 range input signal amplitude nears intercept discussed here extrapolated point which transfer function would intersect horizontal axis, were capable doing Figure slope transfer function simply change detected output voltage over change input signal amplitude, expressed amps, slope expressed terms millivolts Both these values determined performing linear regression over straightest central portion actual detected output voltage versus input signal level curve. Then, actual measured voltage each input level compared that predicted linear regression determine conformance part. conformance ideal versus input signal level practice, dynamic range amps typically defined range over which conformance maximum.
important understand each fundamental performance parameters these categories parts. data sheet each device includes comprehensive theory operation section that goes into detail beyond what presented here. Demodulating Logarithmic Amplifiers ADI's demodulating logarithmic amplifiers (log amps) produce output that proportional common logarithm input signal amplitude; this response described being linear-in-dB. transfer function
Figure Basic Transfer Function
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AD8306 AD8309 also have differential output available that limited version input signal. RMS-to-DC Converters AD8361 TruPwrDetector performs analog rootmean-square computation input signal voltage, thereby producing output voltage that proportional voltage input. transfer function this part linear volts, slope tightly controlled.The AD8361 operated three modes: ground reference (GRM), internal reference (IRM), supply reference (SRM).These modes produce same slope differ y-intercept they produce. nominal y-intercept GRM, IRM, SRM, supply voltage conformance AD8361 determined same demodulating logarithmic amplifiers. Exponential Logarithmic Amplifier AD8362TruPwr Detector exponential logarithmic amplifier that much common with both demodulating amps AD8361 rms-to-dc converter. transfer function AD8362 linear-in-dB demodulating amps. detected output voltage determined squaring averaging input signal voltage, thereby producing output voltage that proportional value input signal, case AD8361. slope, intercept, conformance AD8362 determined same demodulating amps. Special Purpose AD8302 gain phase detector specialized device that determines relative magnitude phase input signals. contains matched demodulating amps, each which outputs: detected output limiter output. detected output Channel subtracted from that Channel resulting signal processed buffered produce output voltage that proportional ratio input signal amplitudes (that gain) with linear-in-dB transfer function. limiter outputs each internally connected digital phase detector, whose output also processed buffered produce voltage that linear-in-degrees representation relative phase input signals. AD8306 AD8306 complete limiting amplifier, providing both accurate logarithmic measure input signal (the RSSI function) over dynamic range programmable limiter output useful from MHz. Figure shows basic connections AD8306. detector transfer function conformance error frequencies down shown Figure Figure Table Figure Figure show AD8306 performs lower frequencies.
Figure AD8306 Basic Connections Operation
Figure AD8306 Slope
Figure AD8306 Conformance Table AD8306 Frequency Performance Data Slope (V/dB) 0.021 0.020 0.021 0.020
Intercept (dBm) -80.361924 -92.2991
-92.0141 -94.8569
Limitations Stanford DS345 function generator used very frequency testing prohibited applying input power levels <-35 below kHz. Rohde Schwarz SMT03 signal generator used above kHz.
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Figure AD8306 Detector Transfer Function Frequencies Despite limitations with test equipment, still possible obtain detailed data about AD8306's ability handle frequency signals. accomplish this, some modifications external circuitry device were necessary. minimum frequency that AD8306 capable detecting determined high-pass corner frequency matching network input pins INHI INLO. equation that describes this relationship
Figure AD8306 Conformance Frequencies AD8307 AD8307 complete monolithic demodulating logarithmic amplifier based progressive compression technique, providing dynamic range conformance tight error bound frequencies MHz. extremely stable easy use, requiring significant external components. single-supply voltage needed, corresponding power consumption only 22.5 fast acting, CMOS-compatible control disable AD8307 standby current less than Figure Figure Figure show basic connections using well typical slope conformance various frequencies within dynamic range specified data sheet.
where:
(see Figure standard configuration evaluation board 52.3 0.01 setting high-pass corner kHz. Increasing lowers corner frequency Figure shows slope AD8306 frequencies. specified slope intercept mV/dB dBm, respectively. data Table Figure show, AD8306 perform very close these data sheet specifications down Below part begins experience significant change intercept; however, slope remains consistent. conformance (see Figure also remains within specification, over limited dynamic ranges.
Figure AD8307 Basic Connections
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case AD8306, input coupling capacitors, determine high-pass corner frequency INHI INLO. Increasing these capacitor values consequently affects performance AD8307 frequencies. However, these only modifications necessary. Analog Devices progressive compression amps include internal offset compensation loop that used null offsets between each fixed gain stages. offset feedback limited range AD8307. Signals larger than this override offset control loop, which impacts performance very small inputs. external capacitor from ground reduces high-pass corner this offset loop arbitrarily frequencies; using sets this corner below capacitor also used VOUT smooth output voltage. This capacitor necessary frequency operation (see Figure 10). Figures through show effects detector transfer function conformance when changed.
Figure AD8307 Transfer Function
Figure AD8307 Conformance Error Table III. AD8307 Frequency Performance (dBm) Slope (V/dB) 0.025 0.025337 0.025 0.025
Figure AD8307 Modifications Frequency Operation Figures through show that AD8307 exhibits very good performance input frequencies. Using input coupling capacitors possible achieve dynamic range with error down kilohertz frequencies. Capacitors >100 lower high-pass corner further, allowing operation 100s hertz, with dynamic range approaching input signals above input coupling capacitors AD8307 meets data sheet specifications slope intercept well achieves measurement accuracy well within important note that limitations signal generator allow measurements below very frequencies. Using schematics shown earlier those found data sheet, AD8307 will respond input signals down
Intercept (dBm) -38.94674 -52.01522 -71.88571 -88.34169 Table AD8307 Frequency Performance (dBm) Slope (V/dB) 0.025 0.025 0.0246 0.025 0.025
Intercept (dBm) -65.42 -79.293 -88.937 -89.673 -89.2263 Table AD8307 Frequency Performance (dBm) Slope (V/dB) 0.025 0.025 0.0247 0.025 0.025
Intercept (dBm) -84.55 -89.9
-90.18 -90.034 -89.7626
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Figure AD8307 Transfer Function
Figure AD8307 Conformance Error
Figure AD8307 Transfer Function
Figure AD8307 Conformance Error
Figure AD8307 Transfer Function
Figure AD8307 Conformance Error
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AD8309 AD8309 logarithmic amplifier based progressive compression (successive detection) technique. This useful received signal strength indication (RSSI) phase detection cellular base stations, radar, other radio transceiver applications. provides dynamic range with accuracy over central operates MHz. logarithmic output proportional logarithm input signal, providing signal over input range. limiter output that amplifies input signal provides stable, limited output with maximum phase skew. This limiter output useful demodulating FSK- PSK-modulated signals. AD8309 operates from single power supply, typically drawing
Figure AD8309 Conformance Performance AD8309 frequencies very similar that AD8306, only difference being that AD8306 laser-trimmed have less variation slope intercept. AD8309 meets data sheet specifications slope intercept down part also exhibits conformance approximately using input coupling capacitors Increasing value these capacitors should increase effective measurement range another This performance indicated Table Figure Figure More details found section about AD8306. Table AD8309 Frequency Performance (dBm) Slope (V/dB) 0.021 0.020 0.021 0.020
Figure AD8309 Basic Connections
Intercept (dBm) -79.5967773 -91.25803 -91.09921 -93.77405
Figure AD8309 Slope
Figure AD8309 Transfer Function Frequencies
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RSSI OUTPUT 10MHz 50MHz 100MHz
-120
-100 (-87dBm)
INPUT LEVEL (dBV)
(+13dBm)
Figure AD8309 Conformance Frequencies AD8310 AD8310 ultrafast response, highly versatile logarithmic amplifier 8-lead MSOP package. complete monolithic demodulating logarithmic amplifier based progressive compression technique, providing dynamic range conformance error bound frequencies MHz. extremely stable easy use, requiring significant external components. single-supply voltage required, resulting power dissipation only AD8310 ideal choice demanding signal measurement applications. AD8310 very rapid response time, enabling detection modulated waveforms more than MHz. Other applications include RSSI, transmit power control, burst detection.
Figure AD8310 Slope
Figure AD8310 Conformance Table VII. AD8310 Frequency Performance Data (dBm) Slope (V/dB) 0.0249 0.02474 0.025 0.02481 0.02494
Intercept (dBm) -86.376 -92.0169 -91.517 -92.277 -91.769 AD8310 performs extremely well frequencies. with other progressive compression amps, necessary increase input coupling capacitors lower high-pass corner INHI INLO. frequency applications, this value should Like AD8307, AD8310's offset compensation loop must adjusted. With external compensation, corner frequency loop MHz. Connecting capacitor OFLT reduces low-pass corner that frequency also necessary some filtering reduce measurement noise. Implementing capacitor BFIN reduces bandwidth output stage increases accuracy output voltage. Figure shows these modifications. Figure Figure show slope accuracy AD8310 when operating frequencies. Slope
Figure AD8310 Basic Connections
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intercept remain within data sheet specifications down intercept begins drift input signal drops below slope remains constant.
level signal. highly linear, temperature stable, useful detecting CDMA, QAM, other complex modulation schemes.The dynamic range Measurement accuracy 0.25 over dynamic range over range. AD8361 offered small 8-lead MSOP package requires only from power supply.
Figure AD8310 Slope Frequencies
Figure AD8361 Basic Connections
Figure AD8310 Conformance Frequencies
Figure AD8361 Slope Various Frequencies, Reference Mode, Supply
Figure AD8310 Modifications Frequency Operation AD8361 AD8361 TruPwr Detection RFIC, offering first time responding power detection integrated form. This device convert complex modulated signal into voltage representing
Figure AD8361 Error MHz, Reference Mode, Supply
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Figure AD8361 Transfer Function
Figure AD8361 Conformance
Figure AD8361 Transfer Function
Figure AD8361 Conformance
Figure AD8361 Transfer Function
Figure AD8361 Conformance
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Table VIII. AD8361 Frequency Performance Frequency (dBm) Slope (V/V) 2.076429 3.684286 4.990714 -0.01261 6.898857 -0.00858 7.766286 -0.01139 8.233714 -0.016 10.032 -0.00242 9.974 -0.00262 10.242 -0.00153 10.242 -0.00153
Intercept (dBm) -0.002328 -0.01208
Table AD8361 Frequency Performance Frequency (dBm) Slope (V/) 8.64 9.67 -0.00309 9.86 -0.00371 9.98 -0.00356 10.01 -0.00357 10.03 -0.00356 10.01 -0.00363 10.04 -0.00252 10.07 -0.00341 10.13 -0.0032
Intercept (dBm) -0.00601
Table AD8361 Frequency Performance Frequency (dBm) Slope (V/V) 10.06 10.10 -0.00259 10.07 -0.00322 10.06 -0.0034 10.06 -0.00344 10.05 -0.00362 10.01 -0.00373 9.95 -0.00366 10.06 -0.0036 10.13 -0.0032
Intercept (dBm) -0.00206
AD8361 three different reference modes operation.The device used collect data this application note ground reference mode (GRM). this mode, output AD8361 ideally input signal. Each part exhibits some small offset voltage, typically millivolts. Much like demodulating amps, AD8361's input sits bias potential above ground. this reason, ac-coupling capacitor necessary. combination input impedance series capacitor, form high-pass filter that determines lowest frequency that device measure. This only part circuit that modified allow AD8361 measure frequency signals. advisable external capacitor FLTR reduce noise output signal, this required. data Tables VIII, previous plots reflect dependency input capacitor, cutoff this filter given
indistinguishable frequencies above with input signals less than rms. response affected only higher input signal levels. Error this device extremely good despite reduced slope response smaller values CC.The previous plots show that this error never exceeds AD8362 AD8362, next generation TruPwr Detector, designed provide wide dynamic range signal level measurement within wireless infrastructure equipment. product provides accurately scaled linear-in-dB output response that equivalent rootmean-square (rms) input waveform, making this detector ideally suited measurement complex modulated waveforms with large crest factors. Effectively modulation-independent, AD8362 ideal high data rate wireless networks that WCDMA, QAM/QPSK, OFDM modulation.
Using filter capacitor sets high-pass corner allowing AD8361 perform consistently data sheet specifications down kHz. interesting note that part respond signals Although slope much lower, intercept remained very close zero linear response observed. Increasing lowers high-pass corner AD8361 begins match expected slope intercept specifications Using response part nearly
Figure AD8362 Typical Connections Measurement Mode
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Table AD8362 Slope Error Data (dBm) Slope (V/dB) Intercept (dBm) 0.013 -49.9337406 0.013 -49.90699 AD8362 comprised loop. input loop drives VGA, which composed variable attenuator driving fixed-gain amplifier. amplifier's output squared; squared signal then integrated internal shunt capacitor, which most applications augmented external shunt capacitor. This squared, averaged signal then compared nominally static reference signal. result this comparison drives attenuation control input VGA. This voltage, available VOUT, proportional common logarithm input signal voltage. bandwidth AD8362 independent gain. Because this amplifier internally dc-coupled, system used accurate voltmeter, retaining temperature-stable decibel-scaled output, down arbitrarily frequencies, example, seismic, audio, sonar instrumentation.This contrast some rms-to-dc converter architectures, most which have full bandwidth only full-scale input, reduced bandwidth input level decreases. input coupling capacitors AD8362 should large enough that lowest frequency components signal, which included measurement, minimally attenuated. example, reduction kHz, capacitances needed because input resistance each input pin, (200 differentially) 1/(2 1500 100) Also, lower high-pass corner frequency VGA, F-Hz capacitor should used between CHPF ground; provide similar high-pass corner, capacitor should used. external low-pass averaging capacitance, CLPF added output squaring cell, should chosen provide adequate filtering detected signal, well maintain stability loop. optimum value depends application, guideline value order F-Hz should used. example, capacitance provides adequate filtering down
Table XII. AD8362 Slope Error Data (dBm) Slope (V/dB) 0.025 0.025 0.0246 0.025 0.025
Intercept (dBm) -65.42 -79.293 -88.937 -89.673 -89.2263 Table XIII. AD8362 Slope Error Data (dBm) Slope (V/dB) 0.025 0.025 0.0247 -90.18 0.025 0.025
Intercept (dBm) -84.55 -89.9
-90.034 -89.7626
Figure AD8362 Slope Various Frequencies
Figure AD8362 Conformance Various Frequencies
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Figure AD8362 Transfer Function
Figure AD8362 Conformance
Figure AD8362 Transfer Function
Figure AD8362 Conformance
Figure AD8362 Transfer Function
Figure AD8362 Conformance
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AD8302 AD8302 fully integrated that measures relative amplitude phase independent input signals. device characterized AD8302 data sheet over common cellular bands (900 MHz, GHz, GHz) used from frequencies GHz. AD8302 integrates closely matched wideband demodulating logarithmic amplifiers, wideband digital phase detector, precision 1.8V reference, analog output scaling circuits.The applied input signals range from (re: corresponding dynamic range.The output provides accurate amplitude measurement over range scaled mV/dB phase measurement over range scaled mV/degree.
Figure AD8302 Slope Error
1.80 ERROR (Degrees) 1.62
PHASE
1.44 1.26 1.08 0.90 0.72 0.54 0.36
0.18 0.00 -180 -150 -120 PHASE DIFFERENCE (Degrees)
Figure AD8302 Basic Connections
Figure AD8302 Phase Output Nonlinearity modification input circuitry AD8302 operate frequencies similar that required single-channel amps. Figure shows modification necessary frequency operation. input coupling capacitors, determine high-pass corner frequency INPA OFSA, their counterparts second channel, INPB OFSB. Increasing these capacitor values enables improved performance AD8302 frequencies. Table XIV. AD8302 Gain CFLT VMAG (dBm) Slope (v/dB) 0.03072 0.029585714 0.02964 -31.50641271 0.029603333 -31.5572116
Intercept (dBm) -30.82379955 -31.51145534
Table AD8302 Phase CFLT VPHS (dBm) P_Slope N_Slope PS_Intercept NS_Intercept 0.011031515 -0.010994545 -171.4731041 177.664949 0.011037576 -0.011036813 -174.7615324 173.4617513 0.011032121 -0.011024545 -169.96435 178.4263471 0.011036813 -0.01104 -174.3398531 173.9210955
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capacitor also used MFLT PFLT pins reduce ripple output voltage from Pins VMAG VPHS. This necessary only degree that ripple unacceptable. Figures through show effects measurements gain relative phase various values Larger capacitor values required measure input signals range. Using input coupling capacitors applying input signals each channel, accuracy achieved over range when measuring gain. Phase accuracy range.
Figure AD8302 Connections Frequency Operation
2.00 1.75 1.50 1.25 VGAIN 1.00 0.75 0.50 0.25 ERROR (Degrees) -0.5 -1.0 -1.5 -2.0 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 -180 -0.5 -1.0 -1.5 -2.0 ERROR (Degrees)
VPHASE
INPA (dBm)
-120
PHASE (Degrees)
Figure AD8302 Gain Output Conformance
Figure AD8302 Phase Output Conformance
Figure AD8302 Gain Output Conformance
Figure AD8302 Phase Output Conformance
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Figure AD8302 Gain Output
Figure AD8302 Gain Conformance
Figure AD8302 Phase Output
Figure AD8302 Phase Conformance CONCLUSION ADI's high frequency demodulating logarithmic amplifiers (AD8306, AD8307, AD8309, AD8310), rms-to-dc TruPwr Detector (AD8361), exponential TruPwr Detector (AD8362), gain phase detector (AD8302) provide excellent performance high input signal frequencies shown operate accurately sub-RF input signal frequencies well, some cases audio spectrum.
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2005 Analog Devices, Inc. rights reserved. Trademarks registered trademarks property their respective owners.
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Operation Detector Products Frequency Matthew Pilotte INTROD

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