HP 8340b Operating Instructions

Response Time
InfrEt°nnf t0 3 Step c i! ange in level is a funct ion of pulse width and rate and is detailed in the
anH o!l at Th f res P° ns ® time ls 3 function of ALC loop bandwidth, which varies with frequency
pvni^Ti 3S P ? e AM sectl0n - The listed response characteristics apply at the minimuni
expected loop bandwidth. An intuitive feeling for response may be gained by the following: At mini¬
mum bandwidth in CW it takes 70 ps to respond to a change and settle to within 10% of the size of the
»wS e ™ « P ± e m0de ; , he samede 9 ree of settling requires 70 ps of closure of the integrate/hold
r0m ,fIIf ° f 7 ? ps pulse ’ t wo 35 ps pulses - e tc - An V Pulse less than 10 ps wide
is treated as a 10 ps pulse. If the pulse period is less than 10 ps.the integrate/hold switch is continu¬
ously closed, so the system responds in 70 ps regardless of width or period.
Simultaneous AM and pulse modulation is provided by the HP 8340B/41B. The AM is dc couDled and
nut.', 1 , a s Wi,h " orma J Cw levelln °-" AM ls used <° ALC below-10dBm the narrow
BWt.^ o V M/Tr a wh. r t : T da9 . r h d eS as expla,ned above ' The bandwidth is given by the equation: 3dB
BW 0.35/Tr, where Tr is the resposne time to a step change described above.
Uneleveled Mode Used With Pulse Modulation
rw n U r P AM °P eratl0 . n may be , used for dynamic range extension or any of the other uses described for
operating mode'atadyXoS.^''" 18 maV be W '' h ,he u " leveled ([SHIFT] 1METER])
Narrow pulse leveling accuracy problems may be treated by simply not attempting to level them The
doLtn e ,d a ° de a "°r ,be user to comrol ,be linear modulator directly. The sSg oHhis modulator
Pnf S Ot Change wl,h P ulse w| dth, so the pulse amplitude remains constant as the pulse is narrowed
fnuke Offi .nd OW , a ,h 25 H nSeC ? ay be produced in ,his mode - T o set ,he amplitude, go to CW operS
(pulse off) and set the desired power via the POWER dBm display. p
%**X*gf ar ® narrov " ed ’. t he P0WER dBm reading drops since it is measuring the output of the
detector S/H system and it is the limitations of this system which cause the narrow pulse levelina
riR°m h^ S | The rea am P lit V de remains essentially constant, however. In unleveled mode, the POWER
dB +SEEES 'iCeXXa^rnSl ALC
ffiooTduTo^e^ ,8n,hS °' 8 dB) dUe ,0 C ° mp °" a "* sa '“ » ha " **
nidPdrift'SlT 0 ' 1 ? doea not involv ® the integrate/hold circuit, there is no leakage induced ampli-
thetona^rm^r^n^ tlfffmnH°? S + eP ^ l0ng periods may be em P lo y ed that are limited onlyby
thP f f th modu ator dr,ve circu| ts- This is not negligible and should be characterized by
er at the frequency of interest. Drifts of a few dB should be expected during warmup Since this
mode is not feedback leveled, the power changes markedly with frequency.
Honolflf''? d m ° d . e the ALC inputs contro1 the linear m °dulator directly, so the response time is not
nnmaUM’ 0n ? U Se P aramet ® rs - The response time is 70 |is maximum in CW, sweeps >5 seconds
4113 maxi !?’ lum for swe ®P s < 5 seconds. AM works in unleveled mode, but the linearity
and sensitivity varies with power level and frequency. See the pertinent preceding section. y
Input Characteristics
iS a ? t ! vatad ' t he HP 8340B/41B RF output is controlled by the voltage at the pulse
+i U i\/ T | t e +h i p ^ t c ' rcuit .'? shown in Figure 3-36. The output is off for inputs below approximately
8340B/41 R^fHpia Ut ° Pen pullS itself up to + 1 - 8 V - which will turn the output on. The HP
8340B/41B s delay and compression specifications assume an input of 0 to +3.0V which requires
no hS? h 6 ir A and so ^ r ®. in 9 3bout 21 mA respectively. The input accepts +12V to -20 V with
no damage, which is compatible with the ±6 V modulator drive of certain network analyzers. Aside
from small effects on delay and compression, the waveform and amplitude of the input is unimportant
as J°" g as ' t transitions from +0.5 to +2.5 V in 2 or less. This transition is suffSnt to genSIhe
fastest rise time. Since the input is not linear, input overshoot will not appear on the output.
3-114
Operating Information
HP 8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English