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RF Synthesizer Settling Time Measurement basics

This page covers RF Synthesizer settling time basics. It describes synthesizer settling time measurement test setup. It mentions different methods to measure RF sythesizer settling time. We will understand this with respect to bluetooth transceiver chip.

RF synthesizer settling time

Bluetooth system usually do not specify synthesizer settling time, but it is one of the crucial specification. It should be about 180 µS in order to have switching from one bluetooth channel to the other channel.

As we know there are total 79 channels typically available in bluetooth chip used across the world. To test the settling time from one channel to the other is a challenge. In order to cut down cost of running the test on all the channels worst case scenario is tested. This is done by verifying the synthesizer settline time from channel-0 (2.402 GHz) to channel-79 (2.480 GHz).

The figure-1 depicts synthesizer settling time curve which is power versus time curve.

RF Synthesizer Settling Time Measurement Test Setup

synthesizer settling time measurement test setup

The figure-1 depicts typical setup used for RF Synthesizer Settling Time Measurement.

There are two measurement methods of RF synthesizer settling time viz. power versus time and Differential Phase Versus Time (i.e. frequency vs time). Modulation domain analyzer mentioned in teh figure-2 uses power vs time method of measurement.

This method utilizes power ramp increase from 10% to 90% in order to determine settling time between channel-0 and channel-79 or between any two channels of test.

In frequency versus time method, frequency counter is used which measures settling of one frequency when channel-0 is selected and later measures settling of other frequency when channel-79 is selected. The time in between the two is referred as settling time between the channels.

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