HP 34970A RF Signal Multiplexing, RF Signal Multiplexing

Chapter 8 Tutorial

RF Signal MultiplexingRF Signal Multiplexing

A special type of multiplexer is the RF multiplexer. This type of multiplexer uses special components to maintain a 50Ω or 75Ω impedance in the signal line being switched. In a test system, these switches are often used to route a test signal from a signal source to the device-under-test. The switches are bi-directional. The diagram below shows two examples of a 4-to-1 channel RF multiplexer in a test system.

		Test 1			Source 1
Signal		Test 2	External		Source 2
Generator		Test 3	Power Meter		Source 3
		Test 4			Source 4
	4 x 1 Multiplexer			4 x 1 Multiplexer

By using patch cables, you can expand RF multiplexers to provide additional test inputs or outputs. For example, you can combine two 4-to-1 multiplexers to create a 7-to-1 multiplexer as shown below.

		Test 1
Oscilloscope		Test 2
		Test 3
		Patch Cable
	4 x 1 Multiplexer

Test 4

Test 5

Test 6

Test 7

4 x 1 Multiplexer

On the HP 34905A (50Ω) and HP 34906A (75Ω) RF multiplexers, you can close only one channel per bank at a time; closing one channel in a bank will open the previously closed channel. These modules respond only to the CLOSE command (OPEN does not apply). To open a channel, send the CLOSE command to another channel in the same bank.

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