User manual

Mailing: PO Box 3526, Bellevue, WA. 98009
Shipping: 13737 SE 26
th
St. Bellevue, WA. 98005
Toll Free: 800-259-7331 * Phone: [phone] * Fax: [phone]
www.sgcworld.com * Email: [e-mail]
51
A directional coupler is a current transformer T2 and a voltage
transformer T1, with termination resistors R33, R34, R35, and
R36. The coupler is inserted in the 50-ohm transmission line
between the input connector, ST2 RF - ST3 GND, and the tuning
network. Forward power is measured across R33, R34 and
reflected power is measured across R35, R36. Diode D1 generates
a positive DC voltage proportional to forward power and D3
generates a positive DC voltage proportional to reflected power.
The forward DC output is fed to a voltage divider consisting of
R19 and R14. These voltages are input to the RF power detector
and to an A to D converter port of the processor. The reflected DC
output passes through a voltage divider consisting of R29 and R16,
and then goes to an A to D converter port of the processor.
5.1.4 Phase Detector
Mailing: PO Box 3526, Bellevue, WA. 98009
Shipping: 13737 SE 26
th
St. Bellevue, WA. 98005
Toll Free: 800-259-7331 * Phone: [phone] * Fax: [phone]
www.sgcworld.com * Email: [e-mail]
52
A phase detector consists of T3, A1, and their associated
components. This detector indicates the state of any reactance
associated with the antenna coupler as noted from the generator. A
line current sample is compared in phase with a voltage sample in
a double balanced mixer. Output polarity varies negative or
positive depending on the reactance of the antenna. The output of
the phase detector A1 is shifted to a 0 to 5v range, then fed to the
processor’s A to D converter port and used within the micro
controller.