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In many applications, what you need is just extracting one frequency from a signal (that is, to know its amplitude). I was dreaming about an IC that allows selecting a frequency of interest, perhaps also, some passing band, and to output the amplitude of the frequency component, exactly like an LM317 allows selecting a regulation voltage. Of course, such IC would be limited in their range of frequencies. Applications include: audio, radio frequency selection, television, frequency response analyser, and even simply eliminating noise from a signal, without having to design a cumbersome sharp filter. Taking this question one step away, I ask about technologies/IC that allows frequency selection in some range of frequencies. The answer may focus on:

  • bandpass filter technologies/IC that allows frequency selection
  • possible "heterodyning" IC
  • other

To avoid too broad questioning, let me restrict the frequency range to 0-100MHz. Also, I need only general guidelines and keywords.

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  • \$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$
    – Voltage Spike
    Jul 11 '20 at 21:55
  • \$\begingroup\$ The edits both make the question substantially broader than before, they also drastically change the goal at far too late a date. Before the goal was audio frequency, now it's VHF. This is simply not a proper usage of this website - we deal in specifics here, not flip-flop "well maybe I want this, or uh, no, maybe I want that". Until you have a clear requirement it is impossible to meaningfully select from the breadth of technlogies, and stack exchange sites are restricted to specific question ONLY. Questions which seek an assortment of disjoint answers do not belong here. \$\endgroup\$ Jul 12 '20 at 2:40
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  • The NE602A from Philips has differential RF inputs and differential IF outputs, with a single-ended (use a series DC_block capacitor) Local Oscillator pin. 8 pin package.

  • The NE602A onchip function is a double-balanced mixer (which nulls out the LO injection and the RF injection, as much as silicon_layout_symmetry can achieve) with response down to DC. Oh, and has a single transistor you can use, or bypass, as your oscillator.

  • Motorola/ONNN SEMI have the MC1595 and 1596, which have functionality similar to the NE602, yet dramatically different as well. Read the datasheets to explore your options.

  • Annnnnd perhaps the best is the last --- the National Semiconductor (now TI) Tone Decoder, the LM567. I used this in prototype direction_finding for robotics, using trisection with 3 beacons for robot positioning. We got 30 foot range with a logarithmic_compression PRE_amplifier after the PhotoTransistor, feeding the LM567.

I've used all 4 of these at various times.

There also are various PhaseLockLoop ICs from Signetics, now Philips or NXP.

TO EXTRACT AMPLITUDE, you need a PLL with Inphase and with Quadrature_detection (requires TWO mixers, or about 10 more transistors; and 0/90 degree Phase Oscillators).

FOR DC OPERATIONS these bipolar circuits are inherently DC_coupled, so will function very well at DC. Part of the analog silicon design experience is to AVOID ANY CAPACITORS, because that requires huge silicon area, or requires TWO MORE PINS on the package. And yes the NE602A will work down to DC (there are no capacitors).

Some of the NE56X PLLs might extract amplitude for you. Or you can search other IC providers.

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  • \$\begingroup\$ Thank you analogsytemsrf. I think such IC may allow me to build "poor man" frequency response analyser in the not so far future. Regarding the answer, I have personally nothing against datasheets (in fact I like this), but since some persons are pedant regarding "shopping questions and answers", it is perhaps better to provide keywords like "double balanced mixer and oscillator". This question will probably be erased anyway. Too few upvotes if any. \$\endgroup\$
    – MikeTeX
    Jul 11 '20 at 18:50
  • \$\begingroup\$ Despite the thread is closed, I have few questions: the LM567, it is quite impressive, but it doesn't allow knowing the amplitude of the selected frequency (is my understanding correct ?). Regarding the NE602A, it is simply amazing, and the circuits look quite simple. It is clear it operates well at 45MHz, and up to 200MHz. But do you know what is the lowest allowed possible frequency? The MC1595 obviously allows superheterodyning, but I'll have to dig more deeply inside the theory to understand why you say it has the same functionality as the NE602. \$\endgroup\$
    – MikeTeX
    Jul 12 '20 at 10:29
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Look into the MT8870 DTMF (Dual tone multi frequency) decoder IC. DTMF is sometimes called Touch-Tone, and every digital phone uses these frequencies. In each case 2 frequencies are mixed together. They have no mathmatical relationship to avoid harmonic resonance. Example: The dial-tone is a mix of 350 and 440 Hz sinewaves.

Link to PDF The MT8870 outputs a 4 bit code that corresponds to 16 possible tone combinations all in the hundreds of Hz range.

NOTE: Recovered frequencies are limited to the 16 dual tones that make up the DTMF protocol. Not ideal in every case as you cannot select arbitrary frequencies.

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This self answer is based on the comment of Chriss Stratton, who have opened to me the exciting world of switched capacitor filters (the part of the question about possible heterodyning IC has been answered by analogsystemsrf). I think his answer is interesting for many reader, hence this edit. Basically, a switched capacitor acts like an RC circuit, whose resistance R depends upon the switching frequency. Here is an example of switched capacitor based integrator:

swcapInt

So, RC filters, or more complex filters can be built with this technology, allowing to control the frequency center. Here is, for example, a quote from the datasheet of the LTC1064 "universal filter building block" IC:

The LTC1064 consists of four high speed, low noise switched-capacitor filter building blocks. Each filter building block, together with an external clock and three to five resistors can provide various 2nd order functions like lowpass, highpass, bandpass and notch. The center frequency of each 2nd order function can be tuned with an external clock, or a clock and resistor ratio. For Q ≤ 5, the center frequency range is from 0.1Hz to 100kHz. For Q ≤3, the center frequency range can be extended to 140kHz.Up to 8th order filters can be realized by cascading all four2nd order sections. Any classical filter realization (such as Butterworth, Cauer, Bessel and Chebyshev) can be formed.

Here is also an application note to help designing switched capacitor based circuits: an40f

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  • \$\begingroup\$ -1 This is not an answer to your question. Your question is orders of magnitude too vague to be answerable. And after your inappropriate moving of the goalposts, this technology is not remotely applicable. You simply cannot select a technology without a clear idea of what you are trying to accomplish... and you have not provided one. You seem to be fixated on trying to use this site for a purpose fundamentally incompatible with the one it is designed to serve; we do specifics here, not catalogs. \$\endgroup\$ Jul 12 '20 at 2:59
  • \$\begingroup\$ Well, maybe I don't understand the datasheet of the LTC1064 cited above (analog.com/media/en/technical-documentation/data-sheets/…). Apparently, it allows to build a 8th order bandpass filter at any frequency between 0.1 to 100kHz (a huge range), and even up to 150KHz, setting the center frequency by few resistors. For me, that's a good answer to the question. And it is only one example of what exist on the market using the switched capacitor technology. I'm really sorry if you are irritated I've used your answer in comment to post this answer (not my intention). \$\endgroup\$
    – MikeTeX
    Jul 12 '20 at 11:22
  • \$\begingroup\$ So, feel free to delete this answer if you wish. \$\endgroup\$
    – MikeTeX
    Jul 12 '20 at 11:47

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