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<HTML> <HEAD> <TITLE>Programmed Test Sources, Inc. - PTS Frequency Synthesizer Technical FAQs</title> <META name="keywords" content="fast,switching,low,noise,rf,lo,source,frequency,synthesizer,programmed,test,sources,pts"> <MEAT http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> </HEAD> <body bgcolor="#FFFFFF"> <table width="530" cellspacing="2" cellpadding="2"> <tr> <td valign=top> <br> <a name="top"><img src="images/support/techfaq.gif"> </td> </tr> </table> <br> <table width="530" cellspacing="0" cellpadding="0"> <tr> <td width=310 valign=top> <font face="arial" size ="2"> PTS offers one of the most complete lines of frequency synthesizers available in the industry. Our models all use our own direct synthesis systems. Their advantages over competitive designs include excellent specifications with low phase noise, fast switching speed and low spurious outputs along with low complexity. <br><br> Each model is a direct frequency synthesizer capable of providing signals for many uses requiring stable and accurate sine-wave signals with low spurious outputs, low phase noise and fast switching between selected frequencies. Typical applications include wireless communications, precision clock sources, radar and surveillance systems and automatic test systems (ATE) with both narrow and wide-band coverage. Options based on a modular design concept permit a high degree of adaptation to a customer�s specific needs. <br><br> To learn more about our product specifications and pricing, <a href="email.html" target="bigframe">request a catalog</a> today. If you have questions about applicability or performance detail, <a href="contact.html" target="bigframe">contact PTS</a>; demonstrator models are available for evaluations. </td> <td width=220 valign=top background="images/support/faqbkgd.gif"> <font face="arial" size ="2" color="#081073"> <center><b>CLICK ON THE TOPIC <br>OF YOUR CHOICE</b> </center> </font> <br> <font face="arial" size="2"> <ul> <li><font face="arial" size ="2"><a href="#intro">INTRODUCTION TO PTS SYNTHESIZERS</a> </li> </ul> <ul> <li><font face="arial" size ="2"><a href="#REMOTE">REMOTE CONTROL INTERFACES</a> </li> <ul> <li><font face="arial" size ="2"><a href="#para">Parallel BCD Interface</a> </li> <li><font face="arial" size ="2"><a href="#gpib">GPIB Interface</a> </li> </ul> </ul> <ul> <li><font face="arial" size="2"><a href="#FREQUENCYSWITCHING">FREQUENCY SWITCHING BEHAVIOR</a> </li> </ul> <ul> <li><font face="arial" size="2"><a href="#FREQUENCYSTANDARDS">FREQUENCY STANDARDS</a> </li> </ul> </td> </font> </tr> </table> <table width="530" cellspacing="2" cellpadding="2"> <tr> <td valign=top> <br> <img src="images/support/divider.gif"> </td> </tr> </table> <br><br> <table width="530" cellspacing="0" cellpadding="0"> <tr> <td> <font face="arial" size ="2"> <a name="intro"><b>INTRODUCTION TO PTS SYNTHESIZERS</b></a></font> <br><br> <font face="arial" size ="2">PTS frequency synthesizers are precision frequency generators. They transfer the accuracy and stability of a frequency standard operating at 5.0 or 10.0 MHz, either built-in or external, to a selectable output frequency. <br><br> Each model is a direct frequency synthesizer capable of providing signals for many uses requiring stable and accurate sine-wave signals with low spurious outputs, low phase noise and fast switching between selected frequencies. Typical applications include wireless communications, precision clock sources, radar and surveillance systems and automatic test systems (ATE) with both narrow and wide-band coverage. Options based on a modular design concept permit a high degree of adaptation to a customer’s specific needs. <br><br> Up to ten significant figures and resolution to 0.1 Hz are available. All output frequencies are coherent with the standard frequency and reflect its stability and accuracy. Any frequency within the instrument’s range may be selected by manual dial or by remote control. The output from the levelled system is +3 to +13 dBm (+10 dBm on the PTS 120) into 50 ohms and may be adjusted manually by the front panel control and meter or remotely by analog voltage. <br><br> PTS synthesizers offer a <i>choice</i> of the two most widely-used remote interfaces. Instruments may be equipped with <i>either</i> the BCD-parallel (buffered) or the GPIB (IEEE 488.1 - 1987) interface. <br><br> The PTS systems of synthesis drastically cut complexity and parts count. The attendant reduction of primary power input and dissipation (less than 50% of that of competitive designs) is a major factor in reliability, which is further enhanced by the use of ceramic ICs, metal-can transistors and a packaging system maximizing mechanical integrity and stability while keeping weight low. For ease of service, most modules are identical, of plug-in design and used in all models. <br><br> <a href="#top">Back to Top</a> </font> <br><br> <font face="arial" size ="2"> <a name="REMOTE"><b>REMOTE CONTROL INTERFACES</b></a></font> <br><br> <font face="arial" size ="2"> For remote-control or computer-controlled applications, all PTS synthesizers are equipped with either a standard parallel BCD interface, or an optional GPIB-compatible interface. (Lower cost remote-only units are available which include no manual control capability.) With both interfaces, output signal frequency, output signal level, and remote/local mode control are programmable. </font> <br><br> <a name="para"><font face="arial" size ="2"><b>Parallel BCD Interface</b></font></a> <br><br> <font face="arial" size ="2">The parallel BCD interface employs a 50-pin Amphenol 57-40500-compatible connector on the equipment, and requires an Amphenol 57-30500-compatible connector for control. <br><br> In the standard parallel BCD interface, output signal frequency programming and remote/local mode control programming use digital TTL-level negative true logic. Output signal level programming uses an analog DC control voltage.<br><br> The digital programming format for frequency control is parallel, 4 bit BCD coding for each digit (decade). All frequency programming connects to, and can be driven by, industry standard 74HCT-type ICs. By default, all frequency control lines are internally pulled to a high (false) state; to program a specific frequency the appropriate pins must be brought to the low (true) state. <br><br> Data latches are included which provide storage when a "latched" or "buffered" mode of operation is required. By default, all Latch Enable (LE) pins are internally pulled to a high (false) state, disabling the latches. To store remote frequency programming input, the LE pins are brought to the low state. To operate in a "transparent" (i.e., non-latched) mode, the LE pins may be left unconnected. A separate LE line is provided for each digit pair (8 bits) so that operation with serial frequency programming data bytes is possible. <br><br> The output signal level is programmed via an analog DC control voltage. The RMS RF output voltage is one-half (0.5) the DC analog voltage present on the output-level control pin (0.63 to 2.0 VDC, corresponding to 0.315 to 1.0 Vrms output into 50 ohms). <br><br> <a href="#top">Back to Top</a> </font> <br><br> <a name="gpib"> <font face="arial" size ="2"><b>GPIB Interface</b></font></a> <br><br> <font face="arial" size ="2"> The GPIB interface employs an IEEE-488 24-pin female connector on the equipment, and requires an IEEE-488 24-pin male connector for control. <br><br> The GPIB interface allows remote programming of the synthesizer via the GPIB (IEEE Standard 488.1 - 1987). The interface allows the synthesizer to act as a basic listener device in either a "LISTEN ONLY" (accepts all valid commands) or an "ADDRESSED" mode (accepts only commands preceded by the appropriate selectable address). <br><br> In addition to remote/local mode control, two PTS synthesizer device-dependent functions can be controlled: output signal frequency, and output signal level. These functions are controlled via GPIB device-dependent commands (i.e., commands issued over the data bus in conjunction with the ATN management bus line in the false state). Output signal frequency can be programmed to the instrument’s full resolution; output signal level is programmed from + 4 dBm to +13 dBm in 1 dB steps. <br><br> The PTS GPIB can be controlled via special-purpose GPIB controllers. Alternatively, a number of manufacturers provide low-cost board-level products for microcomputers which implement the GPIB-488 interface. The PTS GPIB remote-control interface is compatible with such products. <br><br> <a href="#top">Back to Top</a> </font> <br><br> <a name="FREQUENCYSWITCHING"><font face="arial" size ="2"><b>FREQUENCY SWITCHING BEHAVIOR</b></font></a> <br> <br> <font face="arial" size ="2">In all PTS synthesizers, the most significant digits down to 1 MHz (all produced by direct analog technology) have phase-coherent frequency switching. <br><br> For applications requiring high-speed, phase-continuous frequency switching, PTS offers the Direct Digital Synthesis Table Look Up (DDS-TLU or DDS) option. With this option, the standard direct analog low-resolution subsection of an instrument is replaced with a direct digital subsection capable of generating the required low-resolution frequency increments. The DDS can provide phase-continuous frequency switching, and less than 1µs switching time (with 2µs delay). The following versions are available: <ul><li><font face="arial" size ="2">Version H – DDS option replaces the 100 KHz through 0.1 Hz subsection. Phase continuity can be maintained during frequency switches involving the 100 KHz through 0.1 Hz digits. Spurious outputs are -60 to -70 dBc. </li> </ul> <ul> <li><font face="arial" size ="2">Version J – DDS option replaces the 100 KHz through 1 Hz subsection. Phase continuity can be maintained during frequency switches involving the 100 KHz through 1 Hz digits. Spurious outputs are -50 to -55 dBc. </li> </ul> <ul> <li><font face="arial" size ="2">Version K – DDS option replaces the 10 KHz through 0.1 Hz subsection. Phase continuity can be maintained during frequency switches involving the 10 KHz through 0.1 Hz digits. Spurious outputs are -65 to -75 dBc. </li> </ul> <font face="arial" size ="2">The DDS option is available for PTS models 040, 120, 160, 250, 500, 620 and 1000. (DDS high speed, phase-continuous switching is standard in the PTS model 310, 3200, x10, D310 and D620.) Note that the spurious specifications for the versions differ, reflecting the tradeoff between bandwidth coverage and spurious output; consult instrument specifications for details. <br><br> In instruments using the analog mix-and-divide technology for steps from 100 KHz down to 0.1 Hz, frequency switches have limited, though arbitrary, phase discontinuities. In principle, a frequency switch using the 100 KHz digit may have at most a 180� phase jump, a frequency switch using the 10 KHz digit at most an 18� phase jump, 1 KHz at most 1.8�, 100 Hz at most 0.18�, 10 Hz at most .018�, 1 Hz at most .0018�, 0.1 Hz at most .00018�. For all practical purposes, frequency switches of 100 Hz or less may be considered phase-continuous in these instruments. <br><br> <a href="#top">Back to Top</a> </font> <br><br> <a name="FREQUENCYSTANDARDS"> <font face="arial" size ="2"> <b>FREQUENCY STANDARDS</b></font></a> <br><br> <font face="arial" size ="2">The output frequency of a PTS synthesizer reflects directly the accuracy of the controlling frequency standard, either internal or external. PTS offers a choice of two internal standards: a high-stability oven-controlled crystal oscillator (OCXO), or a moderate-stability temperature-compensated crystal oscillator (TCXO). <br><br> All quartz crystal oscillators are secondary standards which require a primary reference for calibration. PTS oscillators are set to within 1x10-7 of nominal at the time of delivery from the factory. Thereafter, these oscillators are subject to the time-drift and temperature-drift given in the specifications. Both PTS oscillators include field-adjustment capability for up to five years of aging. </font> <br><br> <a href="#top">Back to Top</a> </font> <br><br> </td> </tr> </table> <br><br> <table width="530"> <tr> <td align="center"><h5> <a href="index.html" target="_top">Home</a>| <a href="profile.html" target="bigframe">Company Profile</a>| <a href="tech.html" target="bigframe">Technology in Brief</a>| <a href="faqs.html" target="bigframe">Technical FAQs</a><br> <a href="email.html" target="bigframe">Request a Catalog</a>| <a href="download.html" target="bigframe">Download a Catalog</a>| <a href="contact.html" target="bigframe">Contact Us</a> </h5> </td> </tr> </table> </BODY> </HTML>