My customer wrote:
We are planning on using Doherty configuration in one of our design and this is going to induce non linearity.
We need pre-distortion or linearizer built into our design so that it can make the output linear. Linearizer gets a feedback from the output signal and adjusts the input signal to make the output linear. Hope this helps.
I came to know that TI makes some of these devices. It would be nice to get a contact person at TI to discuss more about their products and see whether they suit our application
Here are the specifications of the linearizer we are interested in
Frequency range: 2.3GHz- 2.4GHz
PAR: 7dB to 9dB
I looked at TI website and found some for baseband(GC5325) but could not find anything for our frequency range.
Do you have any suggestions or recommendation?
Thank you
Hello,
In DPD applications using the GC5330 or GC5337, the suggestion is to use an Evaluation Module, and your target PA for a test.
You can look at the EVM description under the GC5330 portion of the TI website. The DPD system can accomodate a 3rd to 7th order correction, depending on the signal BW, and the DPD rate. The DPD rate can be 153.6, or 307.2 for the GC5330. The DPD rate can be 184.32 or 368.64 for the GC5337. The support signal bandwidth would be (DPDrate * .9)/ correction_order [example 153.6Mhz DPD rate, 5th order correction, 27.65Mhz signal BW). In practice people have used the 153.6 HPM rate for 40Mhz systems.
The RF system utilizes a high IF approach, the IF is selected based on the feedback ADC topology. Normally the feedback is centered over a Nyquist zone, Fs/4,3FS/4, or 5Fs/4; the most common is 3FsADC/4.
The IF to RF conversion is handled by an IQ Modulator. If you look at the TSWS3085 (IQ Modulator) and TSW1249 (IQ Demodulator for complex feedback) they can operate from 700Mhz to over 2.5Ghz. In final systems, you need to filter out other clock harmonics and provide filtering and bias between the DAC and IQ Modulator. Please contact Ken Chan (kenchan@ti.com), about the Data converter card specifications.
I think the GC5330 EVM should work at the 2.3 to 2.4Ghz range.
Regards,
Radio Joe
Hi Joe,
I did not see and EVM specific to the GC5330. The TSWS3085 does not list the GC5330 as being used on it. Does the user have to get the GC6016EVM and swap IC's?
Hello
The older GC5330, GC5337 EVM had DAC 3283, IQ Modulator 3720 on the EVM board. This worked in the frequency range you have specified. The older EVM had an onboard real receiver architecture, mixer, common LO with Tx, filter, and ADC used for feedback. Some different frequency ranges needed diffferent mixer components for feedback.
The newer experiments used the older GC5337 EVM with a digital output for the DAC 3484, using the TRF3704 IQ modulator. This worked in the frequency range you have specified. A TSW1249 was built as a complex demodulator for feedback, this used an IQ demodulator, common Tx LO, and a dual ADC.
The current GC6016 digital EVM has digital connectors only. The TSW3085, and TSW1249 can be ordered with the digital EVM. Please contact Ken Chan (kenchan@ti.com) to get more information on the components, schematics, layout, and ordering information. The TSW3085 uses the DAC3482, with the TRF 3705 modulator. The TSW1249 uses a Complex demodulator, and dual TI ADC.
Using a 2.4Ghz RF example, with a 153.6Mhz DPD rate, 204.8Mhz feedback rate. You would have a 153.6Mhz IF, The LO is externally provided to the EVM, so within the range of the IQ Modulator, or IQ Demodulator, the digital portion has a specific DPD rate, ADC rate and IF.
The GC6016 EVM is the title. It is in the same family as the GC5330, GC5337. http://www.ti.com/tool/gc6016evm
The TSW3085 is listed here http://www.ti.com/tool/tsw3085evm
The TSW1249 is not listed, you will need to get that information from Ken Chain.