当然公共部分就不用看了,只看不同之处.不要问俺,俺也是从乡下来的.
the basic full electric scheme is resulted above. advantage of the given scheme above other designs consists in that that, as the phase detector the element of type 74act74 http: //
www.alldatasheet.co.kr/datasheet-pdf/view/fairchild/74act74.html is applied
from the offered sources of the manufacturer, at work with a pressure of 5 volt the range of working frequencies on inputs clk is possible up to 160 megahertz, that completely relieves of need of application of dividers of frequency with application of counters and by that a constant problem of phase noise in schemes of synthesis of frequencies completely and entirely depends on the active filter in a circuit of updating of a pressure of adjustment. the filter or as it still can be named loop filter, is included for the decision 3 задачь simultaneously:
to extinguish all frequency components of dividers n/m/p, p+1/a and r in pll.
to choose a parameter of phase noise from two sources of compared signal ref or vco, and by that "to pull out" outside best of two sources.
the third problem - it represents the greatest complexity and is the compromise 2 above costing. it is engaged in time of "calm" of the reconstructed signal or settling time. proceeding from that line vt is the most sensitive point in the scheme синтесайзера frequencies, from a choice of the order of the active or passive filter its ability "to clear" all спуриусы dividers and by that will depend at reorganization on other frequency, the installation time of the chosen frequency depends on complexity of the filter.
in other words the filter will not create a delay of time of reorganization easier but also will create danger to impose collateral handicapes on a line of adjustment vco.
in all clauses i mentioned a theme of phase noise which in my opinion is if not the most important that very important theme at проэктирование and construction синтесайзеров frequencies.
i in кратце shall try to explain that this such and why it is important. measurement of a parameter of phase noise or ssb phase noise make on a logarithmic scale from a constant отсечкой frequencies from half of peak of a measured signal. half of peak it because of ssb. because of that that the generator constantly "moves" the target signal to the right-to the left from the adjusted frequency, is created jitter. the density of components jitter also is phase noise.
columns explaining concept about settling time
columns explaining concept of phase noise.
the above there will be " a pure dynamic range ", the to receive the best sensitivity of the reception device easier, i.e. itself гетеродин does not bring collateral noise close to an accepted signal. from here the deviation from peak of the basic frequency of the generator as small as possible should be clear that and it will provide desirable result.
tак it is desirable to not apply in schemes active loop filtera such elements as lm-358 or mc-1741. the operational amplifier with parameter input voltage noise no more than 4 nv / (hz) strictly is recommended to use 0,5. these are microcircuits of type op-27 or clc430. http: //
www.national.com/pf/cl/clc430.html http: // web.mit.edu/6.301/www/op27c.pdf
the bright example of that as looks a signal гетеродина very high quality.
now we shall return to the scheme. as it has already been told the given phase detector is capable to accept of two inputs signals of frequencies up to 160 megahertz that allows to apply the new kind dds ad9951, capable to receive clk with frequency in 500 megahertz and a target signal within the limits of 160 megahertz. the given scheme allows to be successfully applied in both вышеупомянутых clauses. if to apply this scheme in the first case (synthesizer eu1cc) changes will be such: we divide generator pice from dds, we change frequency of the generator for dds, raising frequencies of the crystal generator up to 33,3333 megahertz. that multiplication on х6 - internal function dds will allow to receive on output dds half of frequency of the generator = 33,333 megahertz x 6 = 199,999999 : 2 = 99,99999 megahertz. there is a need for change of the program of the processor. i shall notice, that the phase detector of the scheme with are active, the filter and dividers of frequency отподают.
for more "careful" cleaning there are additional variants of the passive filter of 3-rd order. see the scheme below.
i shall allow to specify, that for a step of reorganization already than 1 килогерц it is necessary to calculate the filter so, that it would support stable work of the scheme and would not allow to prevent "защёлкивание" vco on the chosen frequency.
in the second case - clause " still time about dds ", take place applications of the scheme of the phase detector and two examples of generators controllable by a pressure. first of them of industrial type from firm minicircuits pos-50 http: //
www.minicircuits.com/cgi-bin/spec? cat=vco*model=pos-50*pix=a06.gif*bv=4
startfrf stopfrf fif flo convertion type
1,8 mhz 1,9 mhz 21,4 mhz 23,2 23,4 mhz up convertion
3,5 mhz 3,8 mhz 21,4 mhz 24,9 25,2 mhz up convertion
5,3 mhz 5,5 mhz 21,4 mhz 26,7 26,9 mhz up convertion
7,0 mhz 7,3 mhz 21,4 mhz 28,4 28,7 mhz up convertion
10,0 mhz 10,2 mhz 21,4 mhz 31,4 31,6 mhz up convertion
14,0 mhz 14,35 mhz 21,4 mhz 35,4 35,75 mhz up convertion
18,06 mhz 18,2 mhz 21,4 mhz 39,46 39,6 mhz up convertion
21,0 mhz 21,45 mhz 21,4 mhz 42,4 42,85 mhz up convertion
24,8 mhz 25,0 mhz 21,4 mhz 46,2 46,4 mhz up convertion
28,0 mhz 30,0 mhz 21,4 mhz 49,4 51,4 mhz up convertion
one of examples of calculation of frequencies with use of the standard crystal filter on 21,4 мегагерца. accordingly frequency ПЧ=21,4 мегагерца. the given calculation is intended for for the scheme with transformation "upwards". the given variant corresponds to application vco pos-50 which can quite satisfy requirements to the radioamateur equipment and not only house manufacturing. from help data about pos-50 it is visible that the range of frequencies of reorganization lays as-time within the limits of specified in the table above. vt=1~16v; fvco=23~51,7; it is necessary to remind, that at use of the given variant the correct pressure on a feed of active filter clc430/op-27 is necessary to submit. i have provided use of connection of type rail-to-rail +12-0 on the printed-circuit-board of scheme ФАПЧ so when there will be a need to apply the double power supply on + /-12в, it is necessary to clean the resistor - the crosspiece with face value in 1 ohm from the ground and to connect to contact-12 volt. instead of the resistor it is necessary to solder the condenser with capacity in 100 nf. dds so should be adjusted on 23~52 mhz.
vco for overlapping frequencies of 74~105 megahertz.
in the second variant apply following scheme vco to overlapping frequencies of 74~105 megahertz. 12 варикапов are applied with the purpose of improvement of a parameter of phase noise. application of 2 generators demands to take from the scheme under clause " still time about dds " the low-frequency filter existing on a payment and mmic amp. (era-3sm). in a place them the strip filter on the set frequency is necessary.
application of second loop ФАПЧ in two above described designs demands careful adjustment of low-frequency filters and so takes place applications of strip filters of 5-th or 7-th order тубулярной structures with calculation 50-ти омной loadings/signals
