Return-Path: Received: (qmail 21284 invoked from network); 14 May 2002 08:22:18 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO murphys-inbound.services.quay.plus.net) (212.159.14.225) by excalibur-qfe1-smtp-plusnet.harl.plus.net with SMTP; 14 May 2002 08:22:18 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 25835 invoked from network); 14 May 2002 08:22:04 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from unknown (HELO post.thorcom.com) (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 14 May 2002 08:22:04 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 177XX4-0007kF-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 14 May 2002 09:19:42 +0100 Received: from relay.dera.gov.uk ([192.5.29.49]) by post.thorcom.com with smtp (Exim 3.33 #2) id 177XX3-0007k8-00 for rsgb_lf_group@blacksheep.org; Tue, 14 May 2002 09:19:41 +0100 Received: (qmail 7513 invoked from network); 14 May 2002 09:19:38 +0100 Received: from butterfly.mod.uk (HELO warlock.dstl.gov.uk) (192.5.29.10) by relay.dera.gov.uk with SMTP; 14 May 2002 09:19:38 +0100 Message-ID: <7D653C9C42F5D411A27C00508BF8803DCB9AA4@mail.dstl.gov.uk> From: "Talbot Andrew" To: "LF Group \(E-mail\)" Subject: LF: AD9850/51 DDS - Increased power output Date: Tue, 14 May 2002 09:19:10 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: It is possible to get 9dB more power out of the AD9850 and AD9851 DDS chips by using a 2+2:1 centre tapped transformer from both Iout pins with the centre tap to ground to complete a DC path. The output from the transformer is then at 50 ohms making filter design rather easier. This way 7dBm in the HF to VHF range is available - enough to drive a diode ring mixer without any extra gain stage. The push-pull drive also reduces some spurious levels - particularly clock frequency leakage, which makes bandpass filtering the image products more feasible. The circuit details are given in the AD9851 data sheet available at www.analog.com Andy G4JNT "The Information contained in this E-Mail and any subsequent correspondence" "is private and is intended solely for the intended recipient(s)." "For those other than the recipient any disclosure, copying, distribution, " "or any action taken or omitted to be taken in reliance on such information is" "prohibited and may be unlawful."