TRANSMITTER____________________________________________________________
Model 310B Transmitter consists of two major subassemblies –RF Assembly and Transmitter Circuit Board. A
block diagram is shown in Figure 6.
MODULATOR
REGULATOR ANTENNA
GUNN
OSCILLATOR
MODULATED
K-BAND ENERGY
POWER
"ON" LED
12
VDC +
TEST
A B C D MODULATION
CHANNEL
Figure 6 –Model 310BT Transmitter
The RF assembly consists of a Gunn oscillator, which generates K-band microwave energy and the parabolic
antenna system. The Transmitter circuit board contains voltage regulator and modulator circuit to drive the
microwave oscillator. Modulation frequency is selected from one of four channels (A, B, C, D) on the
Transmitter Circuit Board.
A “Test” terminal is provided on the Transmitter Circuit Board. Application of 5.0 to 14.0 VDC (from Power
Supply) will cause Transmitter to turn off, generating a test alarm at receiver. A red “ON” LED on Transmitter
Circuit Board indicates that power is on.
RECEIVER________________________________________________________________
Model 310BR Receiver consists of three major subassemblies –RF Assembly, Receiver Circuit Board and
Power Supply Board. A block diagram of Model 310BR Receiver is shown in Figure 7. The RF Assembly
consists of a parabolic antenna (identical to antenna of Transmitter) and a Schottky diode detector. The detector
converts modulated K-band energy from Transmitter into an audio frequency signal for processing by
Demodulator Circuit Board.
The received audio signal is amplified by an automatic gain control (AGC) preamplifier enabling the
preamplifier output to be held to a constant level regardless of Transmitter Receiver distance (distance must be
within maximum distance of Figure 2). Preamplifier output is applied to a phase locked loop (PLL) detector that
operates as a narrow band-pass filter at one of the modulation frequencies. Receiver channel is selected by
means of PCB jumper to match modulation frequency of Transmitter while rejecting spurious signals and other
Transmitters.
PLL detector output is a voltage level that is held constant under normal conditions by the slow-acting AGC
loop. Rapidly changing signal strength caused by a target moving into the microwave beam is not affected by
AGC loop and causes an AC signal to appear at PLL detector output. Signal is amplified, filtered and compared
with upper and lower alarm threshold voltages.
Whenever signal exceeds either threshold voltage, an alarm is generated. Gain of signal amplifier may be
adjusted with “Sensitivity” potentiometer on circuit board to modify protection patterns per Figures 3. Signal
bandwidth, affecting Model 310B’s response to fast moving targets, may be set “Fast” or “Slow” with PCB
Jumper.
