NLTL-6273SM

Detailed Description

NLTL-6273SM belongs to Marki Microwave’s NLTL family of multipliers and non-linear transmission lines. The NLTL product line consists of passive GaAs MMIC non-linear transmission lines designed and fabricated with GaAs Schottky diode based varactors. NLTLs take an input signal and create an impulse train of harmonics. Harmonic outputs up to and beyond 24 GHz are generated by the NLTL. The NLTL-6273SM is the packaged 5 mm QFN version of the NLTL-6273CH.

Port 1 supports L and S band input signals. Port 2 will output integer multiples of the input signal (i.e., x2, x3, x4, …, x24) up to the 24^th output harmonic or a maximum of 24 GHz. Higher harmonics can be generated but will be at a lower efficiency.

The operating conditions of the NLTL are extremely important to optimize performance. High power inputs will increase the output power observed; however, the conversion efficiency will decrease. This is increasingly true for higher input frequencies and at input powers above the recommended limit. Optimal conversion efficiency of the NLTL is achieved using a square wave input with a fast rise time. Doing so causes a degradation in the 2^nd output harmonic but otherwise improves the conversion efficiency at all other harmonics.

NLTL-6273SM requires no external DC bias. The self-bias of the diodes caused by the rectified RF input signal is sufficient for operation. For the best performance, optimization of the DC return path is recommended for each specific application to optimize the harmonic output power distribution.

The phase noise of a non-linear transmission line is outstanding. If verification of performance is necessary, the application circuit used and input conditions are extremely important. NLTLs are AM sensitive. If there is excessive AM noise on the input of the NLTL, observing the output of the NLTL will show excessive PM/phase noise because of the high AM to PM conversion property of NLTLs.

DC Path to Ground — An RF choke followed by a 15 Ω resistor should be used to provide a DC path to ground on the input port of the NLTL. A shunt 1 μF capacitor is used to filter noise generated by the resistor. This forms the circuit which self-biases the NLTL. The DC return to ground removes DC rectified current created by high power RF signal injection. The DC path to ground is provided within the S package. A conical coil inductor is recommended to push the self-resonance frequency of the inductor past the operating bandwidth of the NLTL. The recommended inductance value of the conical coil inductor is 50nH or higher.

Blocking Capacitor — A DC blocking capacitor on the output of the NLTL-6273SM’s integrated circuit is necessary to prevent unwanted DC current flow from or to the output. If there is a DC signal on the input, place a DC block on the input to avoid disrupting the self-biasing of the diodes.