Routine monitoring of agricultural water-sheds-nutrient data analysis

A broad-band lumped element directional coupler for measuring either the forward or reflected power in a coaxial transmission line. A resistive voltage divider is coupled to the center conductor of a transmission line with a capacitor to keep the phase of the voltage sampling circuit equal to the phase of the current sampling circuit. Capacitors shunting the resistors make the voltage ratio of the resistive voltage divider independent of frequency over a large frequency range. Directivity greater than 50 dB is achieved over a large frequency range for coupling ratios of 30, 40 and 50 dB.