section - Bitsavers

More documents

Recommendations

Info

PHASE LOCKED LOOP APPLICATIONSPHASE LOCKED AM RECEIVER (561 B)The Signetics 561 B can be used as an AM detector/receiver.AM detection is accomplished as illustrated in the blockdiagram of Figure 8-48a. The phase locked loop is lockedto the signal carrier frequency and its VCO output is usedto provide the local oscillator signal for the productdetector or synchronous demodulator. The Pll locks to itsinput signal with a constant 90 0 phase error. The amplitudeof the signal at the output of the product detector is afunction of the phase relationship of the carrier of theincoming signal and the local oscillator; it will be amaximum when the carrier and local oscillator are in phaseor 180 0 out of phase and a minimum when they are inquadrature. It is, therefore, necessary to add a 90 0 phaseshift network in the system to compensate for the normalPll phase shift. The 561 is designed for this to beincorporated between the signal input and the input to thephase comparator input, pin 12 or pin 13.+VNE561B(TOP VIEW)ICyAMINPUTFROMRF AMP ~ ......... a-----!~f--t--'PHASE LOCKED AM RECEIVERCcRyDEMODULATEDOUTPUTCB = BYPASS CAPACITORCc = COUPLING CAPACITORFigure 8-48b11.2K+VTUNING(OPTIONAl.)PHASE LOCKED AM RECEIVERAM-RF o----+----~INPUTf = c1.3 x 10- 4C = ----Y .94 x 10-61.6 x 0.55 = .94MHz then:135pFThe low pass filter for the loop, Cl, is not critical for noinformation is being derived directly from the loop errorsignal and one need only be assured of stable loopoperation. A .01 mfd capacitor was found to be adequate.Figure 8-48aConnection as an AM detector/receiver is given in Figure8-48b. The bypass and coupling capacitors should beselected for low impedance at the operating frequency.Co is selected to make the VCO oscillate at the frequencyto be received and C x is selected, in conjunction with theoutput resistance (8000n) and the load resistance, to rolloff the audio output for the desired bandwidth. The phaseshift network may be determined from the followingequations:C = y1.3 x 10- 4fcpFwhere fc is the carrier frequency of the signal to be receivedand Ry = 3000n. A receiver for standard AM receptionis easily constructed using the circuit of Figure 8-48b. Itsoperating range will be from 550kHz to 1.6MHz. All bypassand coupling capacitors are 0.1 mfd. C y is selectedusing a frequency which is the geometric mean of thelimits of the frequencies which are to be received.Tuning may be accomplished in several ways. The simplestmethod uses a variable capacitor as Co. It should betrimmed so that when set for minimum capacitance, theVCO frequency is approximately 1.6MHz. The capacitanceused may be obtained from the following formula: Co ~300pF where fo is in MHz.foApplication of this formula shows that the minimumcapacitance should be about 180pF and the maximumcapacitance should be 550pF. A second tuning methodutilizes the fine tuning input, pin 6. When current isinserted or removed from this pin, the VCO frequency willchange, thereby tuning the receiver. Select Co' when thecurrent at pin 6 is zero, to make the VCO operate at themean frequency used in the phase shift network calculation(940kHz). The complete standard AM broadcast band maynow be tuned with one potentiometer. The resistor inseries with the arm of the potentiometer is selected to givethe desired tuning range and will be about 1200n when an18V power supply is used.For operation, this receiver requires an antenna and a goodgrounding system. Operation may be improved by includinga broadband untuned RF amplifier, but care should be usedto ensure that the phase locked loop is not overdriven, e.g.input signals should be kept less than 0.5V rms.53
PHASE LOCKED LOOP APPLICATIONSIF STAGE WITH AGC AND AM/FM DETECTION (5618)The circuit shown in Figure 8-49 is basically an I F strip at10.7MHz employing a buffer amplifier, two stages of gain,two ganged stages of AGe and an AGe summing amplifier.A single 561 B PLL serves as both the AM and FM detector.Input sensitivity to insure lockup for either AM or FMdemodulation is approximately 101lV. The input level tothe 561 B is held level at 305mV p-p during input amplitudeexcursion from 10llV to 120mV p-p. Potentiometer RAGeis adjusted at no input for a quiescent dc voltage (pin 6of ampl ifier 5741) of -90m V. Th is presets the 5596multipliers at a maximum gain condition. The gain isslowly reduced as the R F input level rises and full AGeaction begins.The bandwidth of linear demodulation of AM is 1 Hz to4.5kHz and of FM is 1 Hz to 36kHz.I F gain adjustment can be provided with the installation ofa potentiometer between pins 4 and 9 of either (or both)of the 5733, a zero ohm setting insuring maximum gain.The addition of a conventional converter front-end andaudio driver stages completes the circuitry for a receiver.IF GAIN STAGE WITH AGC AND AM/FM DETECTION+6V+6V+6V0.1~~~~HZ IF o-..-il-..--£FRONTEND75 13K10.7MHzSIGNAL510IN9141ST STAGEAGe VOLTAGE-6V-6VFINETUNE100MUDIOOUTPUTNOTE, SET AGC ADJUSTCONTROL FOR 0.09 VDC0.2 AT PIN 6 OF 5741 WHENINPUT SIGNAL IS1ST STAGEAGCVOLTAGE100I INOAGeADJUSTFigure 8-4954
Page 2 and 3:
TABLE OF CONTENTSSECTION TITLE PAGE
Page 4: SECTIONINTRODUCTIONPHASE LOCKED LOO
Page 7 and 8: USER'S QUICK-LOOK GUIDE TO SIGNETIC
Page 10: SECTIONTHE PHASE LOCKED LOOP PRINCI
Page 13 and 14: PHASE LOCKED LOOP APPLICATIONSIt is
Page 15 and 16: PHASE LOCKED LOOP APPLICATIONSROOT
Page 17 and 18: PHASE LOCKED LOOP APPLICATIONSINTEG
Page 19 and 20: ~PHASE LOCKED LOOP APPLICATIONSFUNC
Page 21 and 22: PHASE LOCKED LOOP APPLICATIONSFREQU
Page 24 and 25: PHASE LOCKED LOOP APPLICATIONSGENER
Page 26 and 27: PHASE LOCKED LOOP APPLICATIONSPROBA
Page 28 and 29: ~PHASE LOCKED LOOP APPLICATIONSCapt
Page 30 and 31: PHASE LOCKED LOOP APPLICATIONSTRANS
Page 32 and 33: PHASE LOCKED LOOP APPLICATIONSThe V
Page 34 and 35: PHASE LOCKED LOOP APPLICATIONSINTER
Page 36 and 37: PHASE LOCKED LOOP APPLICATIONSIt is
Page 38 and 39: PHASE LOCKED LOOP APPLICATIONSWhen
Page 40 and 41: PHASE LOCKED LOOP APPLICATIONSSIMPL
Page 42 and 43: PHASE LOCKED LOOP APPLICATIONSSCHEM
Page 44 and 45: PHASE LOCKED LOOP APPLICATIONSNARRO
Page 46 and 47: PHASE LOCKED LOOP APPLICATIONSTwo e
Page 48: PHASE LOCKED LOOP APPLICATIONSd.)e.
Page 52 and 53: PHASE LOCKED LOOP APPLICATIONSFM IF
Page 56 and 57: PHASE LOCKED LOOP APPLICATIONSTRANS
Page 58 and 59: PHASE LOCKED LOOP APPLICATIONSbaud
Page 60 and 61: PHASE LOCKED LOOP APPLICATIONSFigur
Page 62 and 63: PHASE LOCKED LOOP APPLICATIONSinput
Page 64 and 65: PHASE LOCKED LOOP APPLICATIONfTRIAN
Page 66 and 67: PHASE LOCKED LOOP APPLICATIONSRF-FM
Page 68 and 69: PHASE LOCKED LOOP APPLICATIONSVHF O
Page 70 and 71: PHASE LOCKED LOOP APPLICATIONSPRECI
Page 72 and 73: PHASE LOCKED LOOP APPLICATIONSFSK D
Page 74 and 75: PHASE LOCKED LOOP APPLICATIONSThe c
Page 76 and 77: PHASE LOCKED LOOP APPLICATIONSFLUTT
Page 78 and 79: PHASE LOCKED LOOP APPLICATIONSSALES
Page 80 and 81: PHASE LOCKED LOOP APPLICATIONSINTER
show all

section - Bitsavers

Create successful ePaper yourself

Delete template?

Save as template?