What digital modulation formats does the 4480A support?

The 4480A supports a broad range of modulation types, ensuring precise measurements for both Continuous Wave (CW) and digitally modulated signals. This includes CW/FM, AM, QAM, QPSK, FSK, P25 (Phases 1 & 2), CDMA, TDMA, FDMA, and DMR. While it’s not feasible to list every possible modulation and protocol, the following sections provide guidelines on the device’s capabilities and limitations.

Simple Modulation
Simple modulations—such as AM, FM, and PM—encode information by varying a single characteristic of the carrier wave. Because the 4480A is not adversely affected by changes in amplitude, frequency, or phase, it can accurately measure signals in these formats within its specified frequency and power ratings.

Complex Modulation
Complex modulations incorporate multiple changes in amplitude, frequency, or phase, resulting in higher peak-to-average power ratios. The 4480A is designed to handle peak-to-average ratios up to 10 dB. When using these modulations, ensure that the dynamic range requirements remain within the 4480A’s specifications to maintain measurement accuracy.

Channel Spacing
Different modulation schemes can use varying channel-spacing strategies to separate multiple data streams:

CDMA (Code Division Multiple Access)
Uses unique coding for each stream, which does not affect the 4480A’s power-measurement capabilities.

FDMA (Frequency Division Multiple Access)
Separates streams by different frequencies, which similarly has no negative impact on power measurements.

TDMA (Time Division Multiple Access)
Splits transmission time among multiple slots. If only one time slot is active, the transmitted power will effectively be lower than if multiple time slots are active. Consequently, the 4480A will show the true average power as it changes with the number of active time slots.

Long empty time slots (on the order of 0.1 seconds) can cause the 4480A’s readings to vary significantly, because the device may sample during periods of no transmission.

Protocols
Protocols such as P-25, DMR, and LTE define specific rules for how signals are generated and decoded (often involving both modulation techniques and channel spacing strategies). While the 4480A has been tested with a variety of protocols, it’s impossible to validate every possible variation. Nonetheless, the guidelines above—regarding modulation types, power levels, and channel spacing—should help users determine if the 4480A is suitable for their particular application.