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General >> Tech Talk >> What is the advanteges of Direct Sampling Mixer ?
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Message started by pancho_hideboo on Apr 3^rd, 2008, 5:19am

Title: What is the advanteges of Direct Sampling Mixer ?
Post by pancho_hideboo on Apr 3^rd, 2008, 5:19am

Hi.

http://honyaku.yahoofs.jp/url_result?ctw_=sT,eCR-JE,bF,hT,uaHR0cDovL3BhbmFzb25pYy5jby5qcC9jb3JwL25ld3Mvb2ZmaWNpYWwuZGF0YS9kYXRhLmRpci9qbjA4MDMyNi0xL2puMDgwMzI2LTEuaHRtbA==,qlang=ja|for=0|sp=-5|fs=100%|fb=0|fi=0|fc=FF0000|db=T|eid=CR-EJ,kdd0848bc1272acca74404cd6b3290b24,t20080404120247,

http://translate.google.com/translate?u=http%3A%2F%2Fpanasonic.co.jp%2Fcorp%2Fnews%2Fofficial.data%2Fdata.dir%2Fjn080326-1%2Fjn080326-1.html&langpair=ja%7Cen&hl=en&ie=UTF-8

Original News
http://panasonic.co.jp/corp/news/official.data/data.dir/jn080326-1/jn080326-1.html

Recently Panasonic announced a development of one-segment DTV tuner IC using DSM(Direct Sampling Mixer) technology.
This IC uses 65nm CMOS process and its operation voltage of analog(RF) bolck is 1.25Volt.

Although a first stage decimation filter is Sinc filter(moving average filter) in a DSM of Texas Instruments BRF6150 Bluetooth IC(130nm CMOS),
DSM of panasonic uses more generic filter as decimation filter.
Panasonic's first stage decimation filter is a serial-parallel decomposition structure of high order transfer function to realize more sharp attenuation than Sinc filter, I think.

http://techon.nikkeibp.co.jp/article/HONSHI/20061113/123466/

Requirements for NF and distortion are very severe in DTV tuner IC.
I can understand DSM is suitable in low supply voltage operation.
But I don't think DSM is very advantageous in regarding a tradeoff between NF and distortion characteristics.

Here I want to raise some discussions about merit and demerit of DSM technology.

(1) DSM is advantageous in NF ?
(2) DSM is advantageous in distortion ?
(3) Bandlimiting by multistage decimation filtering of DSM is best fit in DTV application ?
(4) DSM is advantageous in current consumption ?
(5) DSM is advantageous in low supply voltage ?
(6) DSM is fit for standard CMOS process ?

Any logical, interesting or amusing opinion is welcome ::)

Title: Re: What is the advanteges of Direct Sampling Mixe
Post by RFICDUDE on Apr 4^th, 2008, 6:25pm

The high level benefits from a digital subsampling architecture include
1. It is closer to a "digital" circuit architecture. This enables easier design flows in digital processes.

2. Flexibiltiy to reconfigure the "digital" architecture as needed for different standards. Traditional analog/RF designs sometimes run into difficulty at baseband because of the different analog channel filtering requirements. This flexibility has been noted by a few as an enabling technology for software defined receivers.

3. In the past it was believed that sampling receivers would always have unacceptable NF due to noise folding, but the problem has been partially solved by incorporating FIR and IIR filter functions into the subsampling functions of the receiver.

4. Linearity is still an issue. You have to have an LNA and front-end amp before the subsampler just like in a LNA downconverter design. I have not seen a detailed discussion of linearity within the subsampler itself.

Here are a couple of good technical references on the technology.

A. A. Abidi, "The Path to the Software-Defined Radio Receiver," IEEE J. Solid-State Circuits, vol. 42, no. 5, 2007, pp. 954-966.

R. Bagheri, A. Mirzaei, S. Chehrazi, M. E. Heidari, M. Lee, M. Mikhemar, W. Tang, and A. A. Abidi, "An 800-MHz - 6-GHz Software-Defined Wireless Receiver in 90-nm CMOS," IEEE J. Solid-State Circuits, vol. 41, no. 12, 2006, pp. 2860-2876.

K. Muhammad, Y.-C. Ho, T. L. Mayhugh, Jr., C.-M. Hung, T. Jung, I. Elahi, C. Lin, I. Deng, C. Fernando, J. L. Wallberg, S. K. Vemulapalli, S. Larson, T. Murphy, D. Leipold, P. Cruise, J. Jaehnig, M.-C. Lee, R. B. Staszewski, R. Staszewski, and K. Maggio, "The First Fully Integrated Quad-Band GSM/GPRS Receiver in a 90-nm Digital CMOS Process," IEEE J. Solid-State Circuits, vol. 41, no. 8, 2006, pp. 1772-1783.

S. Karvonen, T. A. D. Riley, S. Kurtti, and J. Kostamovaara, "A quadrature charge-domain sampler with embedded FIR and IIR filtering functions," IEEE J. Solid-State Circuits, vol. 41, no. 2, 2006, pp. 507-515.

D. Jakonis, K. Folkesson, J. Dbrowski, P. Eriksson, and C. Svensson, "A 2.4-GHz RF sampling receiver front-end in 0.18-/spl mu/m CMOS," IEEE J. Solid-State Circuits, vol. 40, no. 6, 2005, pp. 1265-1277.

J.-F. Luy, T. Mueller, T. Mack, and A. Terzis, "Configurable RF receiver architectures," IEEE Microwave Magazine, vol. 5, no. 1, 2004, pp. 75-82.

R. B. Staszewski, J. L. Wallberg, S. Rezeq, C.-M. Hung, O. E. Eliezer, S. K. Vemulapalli, C. Fernando, K. Maggio, R. Staszewski, N. Barton, M.-C. Lee, P. Cruise, M. Entezari, K. Muhammad, and D. Leipold, "All-digital PLL and transmitter for mobile phones," IEEE J. Solid-State Circuits, vol. 40, no. 12, 2005, pp. 2469-2482.

K. Muhammad, R. B. Staszewski, and D. Leipold, "Digital RF processing: toward low-cost reconfigurable radios," IEEE Communications Magazine, vol. 43, no. 8, 2005, pp. 105-113.

Title: Re: What is the advanteges of Direct Sampling Mixe
Post by rf-design on Apr 10^th, 2008, 3:24am

A sampling mixer transfers less signal energy to IF than a symmetric square wave mixer. If you have an ideal mixer the conversion efficiency is 2/Pi which is a loss of -3.92dB.

Because of that there exist a LNA. Please do not forget the physics.

High designer :D, do you feel you beginning to live an digital, less physical world. ;D

Title: Re: What is the advanteges of Direct Sampling Mixe
Post by pancho_hideboo on Apr 10^th, 2008, 4:36am

rf-design wrote on Apr 10^th, 2008, 3:24am:

A sampling mixer transfers less signal energy to IF than a symmetric square wave mixer. If you have an ideal mixer the conversion efficiency is 2/Pi which is a loss of -3.92dB.

Do you assume balanced or single-ended sampling mixer ?

Or you mean issue about duty ratio of local signal(sampling pulse) ?
For normal mixer(continuous mixer), 0.5 is preferable as duty ratio of local signal.

But for sampling mixer, it is not true. sampling pulse width has to be narrow, but still finite width to charge capacitor.