TM 11-5820-801-30
b. Paramp Circulator. A typical paramp circulator
0.25 GHz) is about 0.2 dB. From 7.9 to 8.4 GHz the filter
provides low loss for RF power flowing in one direction
provides more than 20-dB attenuation. The filter is
between two ports and a high loss for power flowing in
symmetrical so that at frequencies less than 7.1 GHz the
the opposite direction; the power flow is either aided or
attenuation is also 20 dB or more.
impeded by a strong magnetic field. The input signal
2-5. Second Stage Paramp Module 2A2 (Second
from Waveguide Switch 3A2 (at 7.5 0.25 GHz) entering
Stage Amplifier)
the input port of the paramp circulator (P/O AR1) (fig. 2-
The two stages of amplification (2A3 and 2A2) are
1) flows to the paramp varactor port with a loss of about
functionally similar, except that in Second Stage Paramp
0.6 dB. Power flow in the same frequency band in the
Module 2A2 (second stage) an isolator (AT1) and a four-
opposite direction (toward the paramp circulator input
port circulator (P/O AR1) are used in tandem to provide a
port from the paramp varactor port) experiences high
circuit that is equivalent to the first-stage (2A3) five-port
loss. The signal is amplified in the paramp varactor (P/O
circulator (fig. 2-1). Because gain of a parametric
AR1) and the amplified signal appears at the same
amplifier is temperature sensitive it is necessary to
paramp varactor port. The amplified signal flows to the
protect against ambient temperature changes. The
paramp circulator output port with a loss of about 0.3 dB.
operating temperature of the second stage (2A2) is
Power flow in the opposite direction (toward the paramp
maintained at 135F (330K) by controlled heaters within
varactor port from the paramp circulator output port)
2A2. The gain of the second stage is approximately 15
experiences high loss The paramp circulator separates
dB. The overall gain of the two-stage amplifier is 30 dB
the input and output signals, isolates the paramp
[15.2 dB (2A3) -0.2 dB (2A4) + 15 dB (2A2)1].
varactor from the input and output circuits, and provides
2-6. Pump Source Module 2A1
low VSWR and good impedance matches at the input,
output, and paramp varactor ports.
c. Paramp Varactor. Interaction of low input
a. Klystron Oscillator V1.
The parametric
signal power (at 7.5 0.25 GHz), and high pump signal
amplifier pump located in Pump Source Module 2A1 is
basically a klystron oscillator (V1).
Its operating
power (at 42 GHz), in a varactor diode results in an
frequency is 42.00 0.025 GHz and is tunable over the
output signal (at input signal frequency) at a much higher
50-MHz range. To match the paramp varactor; however,
power level than that of the input signal. The varactor
the frequency must be set at 42 GHz. The output power
diode mounted in a suitable structure is called the
of a typical klystron oscillator (V1) is approximately 500
paramp varactor (P/O AR1) (fig. 2-1). The physical
mW, although some klystron oscillators may produce
dimensions and arrangement of the paramp varactor
only 350 mW, the minimum specified value for V1. The
provide, in general, for tuned circuits at three
minimum power level at which the operation of V1 is
frequencies: the signal frequency (7.5 0.25 GHz), the
adequate depends upon the particular paramp varactors
pump frequency (42.00 GHz), and the idler frequency
with which it is used, although never less than 300 mW.
(34.5 0.25 GHz). Careful parts arrangement (and a
The operating temperature of VI is 195F and is
pump filter FL1) prevents the idler frequency from
maintained by controlled heaters on the front and back
propagating through the paramp circulator (signal) or
flanges of V1 (para 2-11).
pump (Pump Source Module 2A1) circuits. The paramp
b. Crossguide Coupler DC1. The pump power
varactor (fig. 2-1) is called a one-port parametric
amplifier stage because both the input and output signals
from klystron oscillator V1 is sampled by an 18-dB
(at 7.5 0.25 GHz) appear at the same paramp varactor
crossguide coupler DC1. The insertion loss of the
port simultaneously.
They are separated by the
coupler is 0.2 dB. The main power flow is from klystron
circulator (b above).
oscillator V1 to power divider PD1.
Amplifier gain is controlled
(1) Crystal Detector CR1. The sampled
principally by controlling the amount of pump power
(generated in Pump Source Module 2A1) at the paramp
pump power (18 dB below the main power level) from
varactor whereas the center operating frequency and
DC1 is rectified in a crystal detector CR1 that uses a
instantaneous bandwidth are controlled principally by the
crystal diode suitable for this frequency range and power
amplitude of the bias voltage (3 3 V) (adjusted in Unit
level.
(2) DC Amplifier A1. The output of crystal
1) applied to the paramp varactor diode.
d. Pump Filter FL1. To prevent sum (49.5 GHz)
detector CR1 is supplied to a dc amplifier (Power Monitor
A1) mounted on a printed circuit card. This amplifier
and difference (34.5 GHz) frequencies (42 7.5 GHz)
uses an integrated circuit (IC) operational amplifier that
from entering the pump circuits (Pump Source Module
requires + 12 V and - 12 V for operation. The detected
2A1), passband pump filter FL1 (fig. 2-1) is used at the
signal input to A1 is usually about 0.5 V but may vary
2A3 pump input port. The filter, with an insertion loss of
from about 0.2 V to about 4 V. The output of A1 drives
0.2 dB at 42-GlIz center frequency, provides at least 15-
the 1-mA PUMP meter (1M5) on the Unit 1 front panel.
dB attenuation at the sum and difference frequencies.
The meter circuit is adjusted so that 1M5 indicates 4 to 6
2-4. Waveguide Filter Module 2A4
(green part of the scale) when the pump power is within
Waveguide Filter Module 2A4 (a bandpass filter) is used
its specified tolerance limits.
to interconnect the two (2A3 and 2A2) amplifier stages
2-3
