Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id v9SCloGl001879 for ; Sat, 28 Oct 2017 14:47:52 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1e8QRC-000584-HW for rs_out_1@blacksheep.org; Sat, 28 Oct 2017 13:42:06 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1e8QRB-00057v-Kd for rsgb_lf_group@blacksheep.org; Sat, 28 Oct 2017 13:42:05 +0100 Received: from omr-a015e.mx.aol.com ([204.29.186.63]) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.89) (envelope-from ) id 1e8QR8-0002V6-Eo for rsgb_lf_group@blacksheep.org; Sat, 28 Oct 2017 13:42:04 +0100 Received: from mtaomg-mce01.mx.aol.com (mtaomg-mce01.mx.aol.com [172.29.27.207]) by omr-a015e.mx.aol.com (Outbound Mail Relay) with ESMTP id CBAC63800082; Sat, 28 Oct 2017 08:41:59 -0400 (EDT) Received: from core-acx14b.mail.aol.com (core-acx14.mail.aol.com [10.74.43.1]) by mtaomg-mce01.mx.aol.com (OMAG/Core Interface) with ESMTP id 8539938000081; Sat, 28 Oct 2017 08:41:59 -0400 (EDT) Received: from 188.192.44.165 by webjas-vae080.srv.aolmail.net (10.96.23.83) with HTTP (WebMailUI); Sat, 28 Oct 2017 08:41:57 -0400 Date: Sat, 28 Oct 2017 08:41:59 -0400 From: Markus Vester To: rsgb_lf_group@blacksheep.org Cc: gm4ism@blueyonder.co.uk Message-Id: <15f6300cb7d-c08-12bee@webjas-vae080.srv.aolmail.net> In-Reply-To: <95A84F71B3724F5D9012CDB023772BBE@MPC> References: <95A84F71B3724F5D9012CDB023772BBE@MPC> MIME-Version: 1.0 X-MB-Message-Source: WebUI X-MB-Message-Type: User X-Mailer: JAS STD X-Originating-IP: [188.192.44.165] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20150623; t=1509194519; bh=Rl8oz7eS/UTmZFuXN1wbcoppHRpS8LKf8cVvChg2fIc=; h=From:To:Subject:Message-Id:Date:MIME-Version:Content-Type; b=UVcIQ4cDYFs5AhJG458mqBImq4P8jFg1HOmLnKM0T790F+r3K0XxyvrYHvXQffxNj v2E3p70Kgya53G8H64KbYrfcJkKOY24f/3WnuSOOTqBo8M86vl3/z7jcH9Raz+ZsVe ZbgHNs2hmfL0TbgBRfJerNT2T6HDep7+tPTxf7X8= x-aol-sid: 3039ac1d1bcf59f47b175d44 X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Mark, the reason while it works is that the carriers are equispaced, so f2-f1 = f3-f2 = 40 Hz. So the whole pattern is repeating every 25 ms. Every time when f1 and f3 are in phase, f2 is now in quadrature. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 131286aabc28dd54c072e5e89638c651 Subject: LF: Re: 3 carrier peak volts Content-Type: multipart/alternative; boundary="----=_Part_95255_661160117.1509194517373" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false ------=_Part_95255_661160117.1509194517373 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Mark, the reason while it works is that the carriers are equispaced, so f2-f1 =3D= f3-f2 =3D 40 Hz. So the whole pattern is repeating every 25 ms. Every time= when f1 and f3 are in phase, f2 is now in quadrature.=20 This three carrier scheme is the simplest form of a quadratic phase, formin= g a rudimantary chirp. For a large number of equispaced carriers, the wavef= orm will asymptotically approach a perfect sweep, like in chirp radar. I ha= ve also employed it to reduce PEP in my "chirped hell" multitone picture tr= ansmission mode. =20 Unfortunately it usually won't work for OFDM because each subcarrier is ind= ependently modulated, typically in both amplitude and phase. This will dest= roy the beneficial phasing and lead to the usual quasi-Gaussian amplitude s= tatistics. Best 73, Markus -----Urspr=C3=BCngliche Mitteilung-----=20 Von: gm4ism An: markusvester Verschickt: Sa, 28. Okt 2017 13:40 Betreff: 3 carrier peak volts Marcus. I don=E2=80=99t seem to be able to post, so my comment below direct to you The peak voltage is a vector addition of the magnitude and phase angle of = each carrier but there is one thing I think overlooked. Each carrier has a different frequency and therefor the vectors rotate a di= fferent rates. It doesn=E2=80=99t matter if that all start with a fixed relative phase, th= ey cant maintain that phase relationship and therefor there will still be= times when the peak voltage is the sum of the individual voltages, as the= y will appear in phase at some time. How often and for how long is a function of the difference in frequency and= number of carriers. This principal is what lies behind the Peak to Mean ratio of multi-carrier = systems such as DAB and other OFDM modulation schemes The hundreds of carriers can in theory all line up giving peak voltages = that are ridiculous. Actually these peaks are statistically so rare and s= hort lived that the accepted peak to mean power of a large number of carri= ers is usually take as 10dB for the purpose of determining component ratin= gs. =20 Mark GM4ISM ------=_Part_95255_661160117.1509194517373 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Hi Mark,

the reason while it works i= s that the carriers are equispaced, so f2-f1 =3D f3-f2 =3D 40 Hz. So the wh= ole pattern is repeating every 25 ms. Every time when f1 and= f3 are in phase, f2 is now in quadrature. 

This three carrier = scheme is the simplest form of a quadratic phase, forming a rudimantary chi= rp. For a large number of equispaced carriers, the waveform will = asymptotically approach a perfect sweep, like in chirp radar. I h= ave also employed it to reduce PEP in my "chirped hell" multitone pict= ure transmission mode.   

Unfortunately = it usually won't work for OFDM because each subcarrier is independently mod= ulated, typically in both amplitude and phase. This will des= troy the beneficial phasing and lead to the usual quasi-Gaussian = amplitude statistics.

Best 73,
Markus

-----Urspr=C3=BCngliche Mitteilung-----
Von: gm4ism = <gm4ism@blueyonder.co.uk>
An: markusvester <markus= vester@aol.com>
Verschickt: Sa, 28. Okt 2017 13:40
Betreff: 3 carrier peak volts

<= /div>
Marcus.
I don=E2=80=99t seem to be able to post, so my comment be= low direct to you
The peak voltage is a vector addition  of the magnit= ude and phase=20 angle of each carrier but there is one thing I think overlooked.
Each carrier has a different frequency and therefor the v= ectors rotate a=20 different rates.
It doesn=E2=80=99t matter if that all start with a fixed = relative phase, they cant=20 maintain  that phase relationship and therefor  there will still = be=20 times when the peak voltage is the sum of the  individual voltages, as= they=20 will appear in phase  at some time.
How often and for how long is a function of the differenc= e in frequency and=20 number of carriers.
This principal is what lies behind the Peak to Mean ratio= of multi-carrier=20 systems such as DAB and other OFDM modulation schemes
The  hundreds of carriers can in theory all line up = giving peak=20 voltages  that are ridiculous.  Actually these  peaks are=20 statistically so rare and short lived that the accepted  peak to mean = power=20 of a large number of carriers is usually take as 10dB for the purpose of=20 determining  component ratings.
 
Mark GM4ISM
 
=
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