What is a Frequency Multiplier aka Doubler?
A frequency multiplier or frequency doubler is a common IC function found in many areas from telecom, to wireless, to test and measurement. In general, the electronic circuit takes the input clock frequency and multiplies the frequency by a factor of more than 1. In most cases, it’s by a factor of 2 and that’s why frequency doubler is a common name used for the circuit element. With the ability to increase the rate of the input signal, it’s no wonder that the circuit block is so widely utilized in numerous markets.
What does a Frequency Multiplier aka Doubler do?
In the RF realm, frequency multipliers are usually used after the baseband has been mixed with the local oscillator (LO). This moves the high frequency operation away from the LO allowing that element to be optimized for frequency selection, phase noise, etc. instead. This approach also leads to lower overall system power consumption and the need for only lower performing mixers.
What are some Frequency Multiplier aka Doubler applications?
Frequency doublers are critical components for test labs and test and measurement equipment. The ability to increase the frequency of the local clock source allows one to purchase a much cheaper clock source for testing. The ability to multiply clock also comes in handy for system designers. It is rare when a system only requires one frequency. In almost all cases, the main system clock signal needs to be multiplied and divided for different sections of the system.
The general architecture of a broadband frequency doubler involves an adjustable delay element and an XOR logic gate. The input clock is split into two where one copy is sent directly to one of the XOR’s inputs while the other is sent first through the adjustable delay line before being routed to the other XOR input. The delay element is set so the second copy of the input signal is delayed one quarter of the input clock period. With this phase relationship set between the two input signals of the XOR gate, the output of the XOR gate produces a clock with a frequency twice that of the input clock signal. The adjustable delay element is needed so the frequency multiplier is broadband plus adjustments can be made to compensate for temperature and process variations. The high frequency limit of the doubler is set by how fine the delay element can be set while the low frequency is determined by the total maximum amount of delay introduced by the delay element.
A few examples of ADSANTEC’s Frequency Multiplier aka Doubler:
ADSANTEC offers one frequency multiplier solution; the ASNT5141-KMC. It is a broadband product that operates from as low as 4.0GHz to as high as 30GHz. Tuning of the delay section is accomplished a differential analog tuning port.
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