Among Mini-Circuits products, what difference between phase detector d

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Among Mini-Circuits products, what difference between phase detector d

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Frequently asked questions about phase detectors (AN-41-001)
Among Mini-Circuits products, what difference between phase detector double-balanced mixer (DBM)? They physically similar, each type product specified data sheets accordance with principal application. range DBMs offered greater frequency range choice power levels. Therefore, system designers might find advantageous utilize phase detector, long frequency range goes down generality questions answers that follow, term "DBM" refers both Mini-Circuits product described double-balanced mixer, that described phase detector. respectively denoted "RF2 RF1" phase detector applications. couple diodes hooked phase detector. expense using same function? type device ideal phase detection since offers high isolation between three ports: reference (LO), input signal (RF) output (IF). Furthermore, provides very offset residual voltage output. explain, briefly, works phase detector? When used phase detector, this merely special case mixing action where signals same frequency. Now, let's look mixer equation: output [(LO RF)t [(LO RF)t [higher-order frequency terms] phase detector application, therefore, first part each term, output only function (2t) plus higher frequency terms. With proper filtering, (2t) terms higher eliminated output equal When difference between phase angles ±90°, output voltage zero. When difference output maximum positive value. When difference 180° output maximum negative value. some models including those specifically designated phase detectors, polarity reversed. polarity important your application specified want use, please consult factory.
AN-41-001 Rev.: (10/21/08) M119925 File: AN41001.doc This document contents property Mini-Circuits.
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What important specifications phase detector? Important electrical specifications phase detector, including used phase detector application, are: offset maximum output output occurring with in-phase signals) isolation between ports polarity output voltage frequency response (variation maximum output with input frequency) temperature variation offset there difference frequency range spec when used phase detector compared with mixer? Yes. frequency specs apply operating unsaturated mode. When used phase detector, operating saturated mode, which tends shrink bandwidth. Thus, conservative when using phase detector, select mixer with bandwidth times wider than unsaturated specs. example, your phase detector application covers 1-500 MHz, select mixer whose port specification least 0.66-750 MHz. intend following phase detector. What problems might face? There three potential problems. Although should ideally have zero volts input, actually have some small voltage. Thus, when connected output phase detector, this voltage improperly bias diodes phase detector cause unbalance diode circuit. Uncertain amount output voltage, uncontrolled load resistance. obtain specified output from phase detector necessary provide 500-ohm load impedance. Overload subsequent circuits lack proper filtering highfrequency spectral components from phase detector, especially component which input frequencies. solution remedy these problems involves simple filter shown. Since very high input impedance, k-ohm series resistor does attenuate output from phase detector. Also, small voltage attenuated 11:1 k-ohm 500-ohm resistor combination) phase detector output. Finally, combination acts pass-filter attenuate frequencies; additional filtering required, multiple-section filter used.
AN-41-001 Rev.: (10/21/08) M119925 File: AN41001.doc This document contents property Mini-Circuits.
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necessary provide filter output phase detector? many cases, yes. RF1-plus-RF2 term when frequencies equal) must removed since cause system degradation. Without filter high frequency terms (IF) output leak into system cause amplifier saturation other undesired results. Does phase detector such SYPD ZRPD series require 500-ohm load? output port approximately current source. lower load resistance used, such ohms, voltage will less. load resistance higher, somewhat more voltage obtained. obtain Output voltage shown data sheet, ohms used. 500-ohm load, returned directly ground, tends keep small voltage from subsequent from improperly biasing diodes phase detector. must operated saturated mode when used phase detector? When sufficiently high input level signals applied ports, operates saturated mode limiter) thus output becomes nearly independent input signal level variations. Thus, output would have voltage proportional only phase difference between inputs. Data sheets phase detectors indicate that both input signals, RF2) should equal amplitude. What happens they not? signal inputs ports sufficient magnitude, phase detector will operate saturated mode provide output proportional phase difference between signals. However, signal sufficient amplitude signal amplitude, output phase detector will proportional amplitude well phase input. operate required saturated mode, signal level should least: Standard Level mixers High Level (+17 mixers Very High Level (+23 mixers. offset important phase detector? many phase detector applications, signals phase with other. Theoretically, phase detector output would zero volts. However, there will slight output offset voltage. This would then interpreted phase difference that other than 90°. Thus, lower offset voltage, more accurately phase detector performs function.
AN-41-001 Rev.: (10/21/08) M119925 File: AN41001.doc This document contents property Mini-Circuits.
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offset voltage phase detector measured? measured statically dynamically. static measurement, terminate port with ohms apply signal only input. Measure port through low-pass filter; this offset voltage. disadvantage static approach that offset contributed input signal included. dynamic test, input signal signal equal amplitude applied their respective ports, with signal slightly offset kHz) from Then pass filter connected port eliminate frequency components including difference frequency. Now, offset voltage reading low-pass filter output more accurate because measured under operating conditions that typical phase detector applications. graph below compares results using methods.
Offset Voltage: Static Dynamic Method Model ADEX-10L: typical samples, Power
0.25 0.15
static static #-8-dynamic static dynamic
Output Voltage,
dynamic
0.05 -0.05 -0.1 -0.15
Frequency,
offset affected temperature? only input present, there should zero output. However, slight mismatch diodes imperfect balance transformer windings, small voltage will appear output. This called offset voltage.
AN-41-001 Rev.: (10/21/08) M119925 File: AN41001.doc This document contents property Mini-Circuits.
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value offset varies with temperature. Over wide temperature range unbalance mixer diodes cause offset, with slight contribution from transformer. effective technique minimize offset variation with temperature diodes whose characteristics track with temperature. This accomplished Mini-Circuits integrating diodes same semiconductor die. Also, MiniCircuits employs specially designed winding machines that assembled transformers have well-matched windings. result: Mini-Circuits offers ultra-low offset characteristics over wide temperature range. graph below, offset measured three temperatures static method (see previous definition) samples having different amounts offset, indicate typical range that might occur.
Offset Voltage: Temperature Effect Model ADEX-10L: Samples, Power
Output Voltage,
25°C 70°C
-0.1 Frequency,
Suppose output insufficient phase detector application. What suggest? higher level mixer than selected. specify Mini-Circuits series high "figure-of-merit" phase detectors. amp. want compare phase square waves. have convert them sine waves before applying them phase detector? Since phase detector operates saturated mode tends square sine wave, necessary alter square wave inputs.
AN-41-001 Rev.: (10/21/08) M119925 File: AN41001.doc This document contents property Mini-Circuits.
Sheet
Isolation specs generally included mixer specs, isolation often listed. What typical values? mixer application, signal level generally very thus RF-IF isolation parameter unimportant. However, phase detector application, level high thus RF-IF isolation becomes important. rule thumb, LO-IF isolation generally less than LO-RF isolation less frequency, 15-20 less mid- high-frequency. What basic steps select proper phase detector? First, decide maximum output needed. Next, select phase detector with adequate bandwidth. Then decide required isolation make sure detector select meets requirement. Finally, phase accuracy critical, specify maximum offset tolerable intended frequency range. What performance characteristic phase detector? output voltage phase detector varies according phase difference between inputs Reference ports. maximum values, positive negative, when inputs in-phase out-of-phase. voltage passes through zero phase difference. When inputs have equal power, specified data sheets MPD, RPD, SYPD ZRPD models, characteristic nearly linear between 180° points. Such characteristic described triangular waveform. signals inputted phase detector much lower power than other, manner used mixer, phase detector characteristic sinusoidal. that case, phase-detector scale factor (also known sensitivity) much less, decreases further phase difference departs from 90°. determine scale factor phase detector, especially different power levels mixer phase detector? does affect loop gain phase-lock loop (PLL)? data sheet RPD-1, example, specifies degree typical scale factor. This conditions applied each input ports, 500-ohm shunt load port. equivalent (0.001 V/mV) (360/2 degrees radian) 0.458 volts radian, which units generally used loop gain calculation. want measure scale factor, applying phase detector signal sources having small frequency difference, each signal being actual power level planning your application. Observe output oscilloscope. should look sinusoidal signal several less than other, nearly triangular both high (such each). Measure slope oscilloscope where trace passes through zero volts. That slope scale factor. Caution: frequencies close together that signal sources pull
AN-41-001 Rev.: (10/21/08) M119925 File: AN41001.doc This document contents property Mini-Circuits. Sheet
toward injection-locking another, because that will distort waveform make measurement inaccurate. Mathematically, peaks sinusoidal waveform slope volts radian. peaks triangular waveform slope volts radian. find that shape waveform in-between sinusoidal triangular take average these results, which 2V/) 0.82 volts radian. polarity output phase detector fixed manufacturer polarity reversed user's discretion? Mini-Circuits phase detectors manufactured provide negative output when in-phase signals applied. user requires positive output, some phase detector models allow user reverse connections reference port. Examples MPD-1 RPD-1, which external connections Pins would reversed. mixer having positive output (when used phase detector) chosen. polarity specified, please consult factory.
AN-41-001 Rev.: (10/21/08) M119925 File: AN41001.doc This document contents property Mini-Circuits.
Sheet

Among Mini-Circuits products, what difference between phase detector d

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