PHASE LOCK LOOP AND ASSOCIATED COMPONENTS FOR
THE RADIO FREQUENCY SYSTEM OF THE PF STORAGE RING PART-II

A.K. Mitra and H. Kobayakawa
National Laboratory for High Energy Physics

In order to achieve phase stable radio frequency power for the RF cavitiesof the PF storage ring! phase lock loops for the individual klystrons as well
as for different RF cavities are to be employed. The basic phase lock loop
consists of three units; a phase detector, a filter and loop amplifier, and avoltage controlled oscillator (VCO). A double balanced mixer is a convenient
way of making a phase detector provided two identical frequency, constant
amplitude signals are applied to the mixer resulting in a DC output voltage
proportional to the phase difference. Figure 1 shows a composite feedback
system where the klystron power is varied by the amplitude modulator and thephase detector is replaced by the mixer. The automatic gain control (AGC)
amplifier is needed to provide constant amplitude to the mixer when theklystron power is varied. The programmable offset voltage (DC) applied to theloop amplifier is intended to compensate the intrinsic phase characteristic ofthe AGC.
A wide-band high performance RF amplifier with AGC has. been constructedusing Watkins-Johnson T0-8 cascadable amplifiers, WJ-Gl attenuator modules anda few external components. The dynamic range of the AGC amplifier is 40 dB
minimum and a gain control feature is provided
to set the output power level to +7 dBm
Electrical Performance at 500 MH::'Iable 1maximum. The scheme of the amplifier is500 MP.;:
shown in Figure 2. The control voltage VFrequency+2
RF Output
for the WJ-Gl attenuator modules is obtaified-37 to +10
Dynamic:. Range
from the RF detector and the associated<1.5:1VSWR In/Out
response
phaseand>25 dB Down
amplitude
Thecircuits.
Harmonics,.
ChangePhaseof the AGC are illustrated in Figures 3 and(for the Dynamic
4. The dynamic range is -37 to +10 dBm.
Fc:n: 10 Mllz Bandwidth:';.O.
The output power variation is within ±0.1 dB
Phase linearity±0.1 dB
Amplitude
and the phase linearity is within ±0.5° for
10 nsecc-::JGroup de)-ay
10 MHz bandwidth. The electrical performance
250 ,-._;.
15 VDC Supply
at 500 MHz is summarized in Table 1.
d5"::~

d3~Ran~e)s~variatio:~.

at* Output can be set between -5 to +7 dB;n by a-::us~i:~;: !<.-The AGC amplifier's dynamic range is
47 dB which means that in the feedback loop
shown in Figure 1, for a klystron power
variation of 4.0 W to 200 kW, the AGC performance is adequate. A double sided
printed circuit board is used to construct the AGC and the 50 ~ line impedanceof the amplifier is obtained by microstrip line:
References
1)
2)

Photon Factory Design Manual (1979).
Reference Data for Radio Engineers, 177, Sixth Edition, Chapter 8,
pp 24-25.

-221-

T

RFINPUT"

2JOUTPUT

1-'~J£2-2835~t~\,,,
lflpH+15V -:---c;-_:c----<~o6'---::tc] +l5V

0.047 :;[:"~;,,/1::];: 0.047-lsv ~iiT'--:J:-IT -15V
0.047~.[:::{:0.047

Figure 2.

Schcmati.c of Aotomil-tic Guin Contml- Amrl fffcr.

·RF OUTPUT
dBrn+2Arnpl itude.:.t~-2
Amplitude-4}:)"PhasePhase

Ii-611<'l 'II-10-50

Figure 3.

-40-30-20-10+lCd2-.
RF !';?!.JT-:
sao fo'.Hz
Figure 4.

Amplitude a~d Phase Variation of the AGC :.,"'lylifier for
500::5 MHz bandwidth.

Input Pc~;er is -20 ;3m il!'ld Out:•..:t.

POwer at .500 MHZ is +2 dS-:1.
Verti~al Scale for Am;:.lit.ud~
Vertical Scale for Phase

Amplitude and Phase Variation of the ,!:;tomatic
Gain Control Amplifier vs Input Power.

-222-0.25 dB/division10"'/division