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HackRF: updated documentation

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f4exb
2019-04-02 22:29:17 +02:00
parent 4e24dd954e
commit 624a3e8ef5
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plugins/samplesource/hackrfinput/readme.md
+15 -9
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@@ -4,12 +4,6 @@
This input sample source plugin gets its samples from a [HackRF device](https://greatscottgadgets.com/hackrf/).
<h2>Build</h2>
The plugin will be built only if the [HackRF host library](https://github.com/mossmann/hackrf) is installed in your system. If you build it from source and install it in a custom location say: `/opt/install/libhackrf` you will have to add `-DHACKRF_DIR=/opt/install/libhackrf` to the cmake command line.
The HackRF Host library is also provided by many Linux distributions and is built in the SDRangel binary releases.
<h2>Interface</h2>
![HackRF input plugin GUI](../../../doc/img/HackRFInput_plugin.png)
@@ -84,10 +78,14 @@ The device stream from the HackRF is decimated to obtain the baseband stream. Po
- **Inf**: the decimation operation takes place around Fs - Fc.
- **Sup**: the decimation operation takes place around Fs + Fc.
With SR as the sample rate before decimation Fc is calculated as:
With SR as the sample rate before decimation Fc is calculated depending on the decimaton factor:
- if decimation n is 4 or lower: Fc = SR/2^(log2(n)-1). The device center frequency is on the side of the baseband. You need a RF filter bandwidth at least twice the baseband.
- if decimation n is 8 or higher: Fc = SR/n. The device center frequency is half the baseband away from the side of the baseband. You need a RF filter bandwidth at least 3 times the baseband.
- **2**: Fc = SR/4
- **4**: Fc = 3*SR/8
- **8**: Fc = 5*SR/16
- **16**: Fc = 11*SR/32
- **32**: Fc = 21*SR/64
- **64**: Fc = 21*SR/128
<h3>9: Rx filter bandwidth</h3>
@@ -100,3 +98,11 @@ The LNA gain can be adjusted from 0 dB to 40 dB in 8 dB steps.
<h3>11: Rx variable gain amplifier gain</h3>
The Rx VGA gain can be adjusted from 0 dB to 62 dB in 2 dB steps.
<h2>Frequency synchronization with Tx</h2>
When a device set for the same physical device is present the device center frequencies are synchronized because there is only one LO for the physical device.
When the center frequency position Fc (control 8) is set to center (Cen) in both Rx and Tx the actual frequency of reception and transmission are the same.
In other cases for both frequencies to match you have to set the same sample rate and Fc position (either Inf or Sup) in the Rx and Tx.