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Vertical Navigation Radar

Matjaz Vidmar, S53MV

3. Modules

The vertical navigation radar as proposed in the previous section "Design" includes many practical electronic circuits. These are grouped into six different modules built on printed-circuit boards. The detailed electrical circuit diagrams of all six modules are presented in this section.

The sweep module includes a triangular-sweep generator and +8V power supply circuits for the whole transmitter. The triangular-sweep generator includes a triangular oscillator with the TL082 double operational amplifier, two analog switches CD4051 and CD4052 to respectively select one out of eight resistors and one out of four capacitors, TTL-to-CMOS level shifters with three FMG1 dual digital transistors and a dither generator with a CD4024 binary counter.

The triangular-sweep generator may generate 32 different sweep frequencies, selected with 5 TTL inputs. There are three trimmers to adjust the symmetry, amplitude and offset of the generated triangular sweep. The module is built on a single-sided PCB with the dimensions of 30mmX80mm, as shown on the following images:

The transmitter module includes a 4.3GHz VCO (BBY51-03W and BFP420), a buffer stage (another BFP420), a power-amplifier stage (MGF4918D)generating about 40mW (+16dBm) and a coupler for the receiver LO. The 20mmX80mm module is built in microstrip technology on a double-sided teflon laminate with a dielectric constant of 2.43 and 19mils (0.5mm) thickness, as shown on the following images:

The receiver module includes a 4.3GHz LNA (MGF4918D), a mixer stage (IAM81008), a 25kHz high-pass filter and an IF amplifier (FMMT493). The 20mmX80mm module is built in microstrip technology on a double-sided teflon laminate with a dielectric constant of 2.43 and 19mils (0.5mm) thickness, as shown on the following images:

The IF module includes two bandpass filters for 30kHz and 33kHz, two logarithmic detectors (two pieces SA604AD), two output buffer stages (LM358) and power-supply circuits for the whole receiver chain. Each bandpass filter includes four LC-tuned circuits. Each logarithmic detector has a trimmer on its output to precisely adjust the logarithmic scale. The module is built on a single-sided PCB with the dimensions of 45mmX60mm, as shown on the following images:

The main processor module includes a PIC 16F876A microprocessor and associated circuits: power supply, clock, reset and protection of the analog A/D inputs. The graphical LCD module WG12864B is connected directly to the main processor. A pushbutton on the rear panel is used to set the threshold level for valid reflections. The module is built on a single-sided PCB with the dimensions of 45mmX60mm, as shown on the following images:

The voice synthesizer module includes its own processor PIC 16F84A with associated circuits: clock, reset, data-level shift, an analog voice-recorder chip ISD2560, an audio power amplifier LM386 and associated power-supply circuits. A trimmer is provided for the volume setting. The module is built on a single-sided PCB with the dimensions of 45mmX60mm, as shown on the following images:

The installation and interconnection of the six modules is presented in the following section "Assembly".

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