DIGITALY CONTROLLED RADIO RECEIVER

Hi all

My question is about the structure of a digitally controlled radio like this

formatting link

From the point of view of the micro controller that controls it .

If I understand well that micro does 3 main things

1> controls the frequency of the PLL that functions as a local oscillator used by the rf mixer 2> sends the relevant data to the LCD .

3> respnds ti the buttons .

I want to concentrate on the first two .

How the micro controls the PLL so it will produce the exact frequency that the LCD displays.

And how the micro translates the frequency knob to a chosen frequency .

Thanks Elico

Reply to
RealInfo
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typically the PLL is a VCO which is divided and compared with a fixed clock, the microcontroller will program clock divider - it may even use an internal counter to do this. this divided clock is compared with a reference clock and the difference is fed back to control the VCO

probably some sort of quadrature encoder and a the micro just counts up or down as the knob is turned.

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?? 100% natural
Reply to
Jasen Betts

Many of the current designs are using Direct Digital Synthesis (DDS) instead of a PLL, though also PLL designs are used. The details of frequency set-up depend on the frequency generator chip (or chipset) chosen and the selected frequency generation scheme.

For a primer on DDS, see:

There are also links to chip datasheets and app notes for controlling them.

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Tauno Voipio
Reply to
Tauno Voipio

On a sunny day (Sun, 17 Mar 2013 02:26:27 -0700 (PDT)) it happened RealInfo wrote in :

programmable divider

rotary encoder.

Reply to
Jan Panteltje

Many thanks you all Elico

Reply to
RealInfo

Most such radios have one or more PLL (phase lock loops) that add and multiply to produce the transmit and local oscillator frequency. For the TS-590S, you'll find a block diagram in the owners manual: The "in depth" manual includes a theory of operation section that explains how the PLL synthesizer works. In this radio, there are 3 mixers (triple conversion) that eventually produce the 24KHz IF used by the DSP. There is also a single conversion section for specific bands near the IF frequency. See Section 1.x for details.

For more detail and schematics, the full service manual is at:

The knob runs a shaft encoder that eventually sets multiple divider ratios (depending on frequency band) to produce the three local oscillator frequencies. The relationship is set by a formula that varies with the type of conversion, frequency range, and tx/rx. The divider ratios set the various PLL's to eventually generate the desired output frequency without also producing spurious and extraneous extra frequencies and noise.

There's more to HF radio design than just synthesizing the necessary frequencies. In my never humble opinion, the processor and synthesizer are the easiest parts of the puzzle. This might help:

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

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