Transmitter Circuit Downsizing

Technical description

The direct modulation method used in the transmission system is a way of applying frequency modulation to the PLL using inputs from a modulation circuit. With frequency modulation method, the configuration can be simplified by modulating the carrier wave directly without a Mixer.

About AK1574/AK1590/AK2400/AK2401A

These PLL Synthesizers are designed to allow for frequency modulation. The AK1590 is a PLL Synthesizer IC, the AK1574 is a VCO built-in IC, and the AK2400/AK2401A is an integrated device. These ICs can perform frequency modulation using the offset frequency adjustment function of the built-in ΔΣ Fractional-N PLL Synthesizer.

Transmitter circuit downsizing using direct modulation method

Circuit configuration example

Conventional transmitter circuit configuration

As shown in Figure 1, a digital signal is placed on a carrier wave using a Mixer.

Figure 1. Conventional transmitter circuit block diagram

Direct modulation circuit configuration

As shown in Figure 2, a transmitter circuit can be configured by modulating directly to a VCO without the Mixer.

Figure 2. Direct modulation circuit block diagram

A direct modulation circuit can be configured as shown in Figure 3 by using the AK1574 that is a IC with built-in VCO.

Figure 3. Example of direct modulation circuit configuration using AK1574

A direct modulation circuit can be configured as shown in Figure 4 by using VCO and the AK2401A that is direct conversion IC.

Figure 4. Example of direct modulation circuit configuration using AK2401A

Evaluation data

The AK1574 achieves the following performance with FSK error of 1 % or less.

Evaluation board

Evaluation boards and application notes are available for easy evaluation.

Contact us if you wish to have a sample or evaluation board.