Model XMC2560A-20 Rev B Wideband 20 dB Directional Coupler Military Grade Description The XMC2560A-20 is a low profile, high performance 20dB directional coupler in an easy to use, manufacturing friendly surface mount package. It is designed primarily for defense applications. The XMC2560A-20 is designed particularly for power and frequency detection, as well as for VSWR monitoring, where tightly controlled coupling and low insertion loss is required. It can be used in high power applications up to 100 Watts. Parts have been subjected to rigorous qualification testing and they are manufactured using materials with coefficients of thermal expansion (CTE) compatible with common substrates such as FR4, G-10, RF-35, RO4350, and polyimide. Features: • 2500 – 6000 MHz • Defense Applications • High Power • Very Low Loss • Tight Coupling • High Directivity • Production Friendly • Tape and Reel • Available in Lead-Free (as illustrated) or Tin-Lead • Reliable, FIT=0.41 Electrical Specifications ** Mean Frequency Coupling Insertion Loss VSWR Directivity MHz dB dB Max Max : 1 dB Min 2500-6000 20.0 ± 0.80 0.20 1.25 18 Frequency Sensitivity Power dB Max Avg. CW Watts ºC/Watt ºC ±1.25 TBD 21.5 -55 to +95 ΘJC Operating Temp. **Specification based on performance of unit properly installed on Anaren Test Board 54606-0003 with small signal applied. Specifications subject to change without notice. Refer to parameter definitions for details. Top View .560±.010 [14.22±0.25] PIN 1 ORIENTATION MARKER DENOTES PIN 1 Bottom View Side View .065±.014 PIN 2 .350±.010 [8.89±0.25] PIN 2 4X .025±.004 [.64±0.10] GND .254±.004 [6.45±0.10] 4X .042±.004 SQ [1.07±0.10] GND PIN 4 DENOTES ARRAY NUMBER PIN 3 PIN 3 Available on Tape and Reel for Pick and Place Manufacturing. 29 Sep 09 PIN 1 .464±.004 [11.79±0.10] USA/Canada: Toll Free: Europe: PIN 4 (315) 432-8909 (800) 411-6596 +44 2392-232392 Model XMC2560A-20 Rev B Directional Coupler Pin Configuration The XMC2560A-20 has an orientation marker to denote Pin 1. Once port one has been identified the other ports are known automatically. Please see the chart below for clarification: 20dB Coupler Pin Configuration Pin 1 Input Direct Pin 2 Direct Input Pin 3 Isolated Coupled Pin 4 Coupled Isolated Note: The direct port has a DC connection to the input port and the coupled port has a DC connection to the isolated port. For optimum performance use Pin 1 or Pin 2 as inputs. XMC2560A-20 Typical Performance Coupling Return Loss 0 -5 -10 -15 S22 -17.0 S33 -18.0 S44 Coupling [dB] Return Loss [dB] -16.0 S11 -20 -25 -30 -35 S32 Mean -19.0 -20.0 -21.0 -22.0 -40 -23.0 -45 -50 2500 S41 -24.0 3000 3500 4000 4500 5000 5500 6000 Frequency [MHz] USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 2500 3000 3500 4000 4500 5000 Frequency [MHz] Available on Tape and Reel for Pick and Place Manufacturing. 5500 6000 Model XMC2560A-20 Rev B Insertion Loss Directivity 0 0 -5 S31-S41 -10 Directivity [dB] -0.2 S21+S41 -0.3 S43+S23 -0.4 S42-S32 -15 -20 -25 -30 -0.5 -35 -40 -0.6 2500 3000 3500 4000 4500 5000 5500 2500 6000 3000 3500 4000 4500 5000 5500 6000 Frequency [MHz] Frequency [MHz] Frequency Sensitivity 1.5 S41 S32 Frequency Sensitivity [dB] Insertion Loss [dB] -0.1 1.0 0.5 0.0 -0.5 -1.0 -1.5 2500 3000 3500 4000 4500 5000 5500 6000 Frequency [MHz] Available on Tape and Reel for Pick and Place Manufacturing. 29 Sep 09 USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Model XMC2560A-20 Rev B Definition of Measured Specifications Parameter Definition VSWR (Voltage Standing Wave Ratio) The impedance match of the coupler to a 50Ω system. A VSWR of 1:1 is optimal. Return Loss The impedance match of the coupler to a 50Ω system. Return Loss is an alternate means to express VSWR. Mean Coupling Mean coupling is the average coupling value in dB of the maximum and minimum power levels from the coupled arm.. Mathematical Representation VSWR = Vmax Vmin Vmax = voltage maxima of a standing wave Vmin = voltage minima of a standing wave Return Loss (dB)= 20log Mean Coupling (dB) = 0.5 * [CouplingMax (dB) + CouplingMin (dB)] where CouplingMax (dB) =10log (PowerMax*) CouplingMin (dB) =10log (PowerMin*) * Insertion Loss Transmission Loss Directivity Frequency Sensitivity USA/Canada: Toll Free: Europe: The input power divided by the sum of the power at the two output ports. The input power divided by the power at the direct port. The power at the coupled port divided by the power at the isolated port. The decibel difference between the maximum in band coupling value and the mean coupling, and the decibel difference between the minimum in band coupling value and the mean coupling. (315) 432-8909 (800) 411-6596 +44 2392-232392 Available on Tape and Reel for Pick and Place Manufacturing. VSWR + 1 VSWR - 1 10log from the coupled arm Pin Pcpl + Pdirect 10log 10log Pin Pdirect Pcpl Piso Max Coupling (dB) – Mean Coupling (dB) and Min Coupling (dB) – Mean Coupling (dB) Model XMC2560A-20 Rev B Notes on RF Testing and Circuit Layout The XMC2560A-20 Surface Mount Couplers require the use of a test fixture for verification of RF performance. This test fixture is designed to evaluate the coupler in the same environment that is recommended for installation. Enclosed inside the test fixture, is a circuit board that is fabricated using the recommended footprint. The part being tested is placed into the test fixture and pressure is applied to the top of the device using a pneumatic piston. A four port Vector Network Analyzer is connected to the fixture and is used to measure the S-parameters of the part. Worst case values for each parameter are found and compared to the specification. These worst case values are reported to the test equipment operator along with a Pass or Fail flag. See the illustrations below. 3 & 5 dB Test Board 10 & 20 dB Test Board Test Board In Fixture Test Station Available on Tape and Reel for Pick and Place Manufacturing. 29 Sep 09 USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Model XMC2560A-20 Rev B The effects of the test fixture on the measured data must be minimized in order to accurately determine the performance of the device under test. If the line impedance is anything other than 50Ω and/or there is a discontinuity at the microstrip to SMA interface, there will be errors in the data for the device under test. The test environment can never be “perfect”, but the procedure used to build and evaluate the test boards (outlined below) demonstrates an attempt to minimize the errors associated with testing these devices. The lower the signal level that is being measured, the more impact the fixture errors will have on the data. Parameters such as Return Loss and Isolation/Directivity, which are specified as low as 27dB and typically measure at much lower levels, will present the greatest measurement challenge. The test fixture errors introduce an uncertainty to the measured data. Fixture errors can make the performance of the device under test look better or worse than it actually is. For example, if a device has a known return loss of 30dB and a discontinuity with a magnitude of –35dB is introduced into the measurement path, the new measured Return Loss data could read anywhere between –26dB and –37dB. This same discontinuity could introduce an insertion phase error of up to 1°. There are different techniques used throughout the industry to minimize the affects of the test fixture on the measurement data. Anaren uses the following design and de-embedding criteria: • Test boards have been designed and parameters specified to provide trace impedances of 50 ±1Ω. Furthermore, discontinuities at the SMA to microstrip interface are required to be less than –35dB and insertion phase errors (due to differences in the connector interface discontinuities and the electrical line length) should be less than ±0.25° from the median value of the four paths. • A “Thru” circuit board is built. This is a two port, microstrip board that uses the same SMA to microstrip interface and has the same total length (insertion phase) as the actual test board. The “Thru” board must meet the same stringent requirements as the test board. The insertion loss and insertion phase of the “Thru” board are measured and stored. This data is used to completely de-embed the device under test from the test fixture. The de-embedded data is available in S-parameter form on the Anaren website (www.anaren.com). Note: The S-parameter files that are available on the anaren.com website include data for frequencies that are outside of the specified band. It is important to note that the test fixture is designed for optimum performance through 6GHz. Some degradation in the test fixture performance will occur above this frequency and connector interface discontinuities of –25dB or more can be expected. This larger discontinuity may affect the data at frequencies above 6GHz. Circuit Board Layout The dimensions for the Anaren test board are shown below. The test board is printed on Rogers RO4003 material that is 0.020” thick. Consider the case when a different material is used. First, the pad size must remain the same to accommodate the part. But, if the material thickness or dielectric constant (or both) changes, the reactance at the interface to the coupler will also change. Second, the line width required for 50Ω will be different and this will introduce a step in the line at the pad where the coupler interfaces with the printed microstrip trace. Both of these conditions will affect the performance of the part. To achieve the specified performance, serious attention must be given to the design and layout of the circuit environment in which this component will be used. If a different circuit board material is used, an attempt should be made to achieve the same interface pad reactance that is present on the Anaren RO4003 test board. When thinner circuit board material is used, the ground plane will be closer to the pad yielding more capacitance for the same size interface pad. The same is true if the dielectric constant of the circuit board material is higher than is used on the Anaren test board. In both of these cases, narrowing the line before the interface pad will introduce a series inductance, which, when properly tuned, will compensate for the extra capacitive reactance. If a thicker circuit board or one with a lower dielectric constant is used, USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Available on Tape and Reel for Pick and Place Manufacturing. Model XMC2560A-20 Rev B the interface pad will have less capacitive reactance than the Anaren test board. In this case, a wider section of line before the interface pad (or a larger interface pad) will introduce a shunt capacitance and when properly tuned will match the performance of the Anaren test board. The entry angle of the traces has a significant impact on the RF performance and these parts have been optimized for the layout used on the test boards shown below. Testing Sample Parts Supplied on Anaren Test Boards If you have received a coupler installed on an Anaren produced microstrip test board, please remember to remove the loss of the test board from the measured data. The loss is small enough that it is not of concern for Return Loss and Isolation/Directivity, but it should certainly be considered when measuring coupling and calculating the insertion loss of the coupler. An S-parameter file for a “Thru” board (see description of “Thru” board above) will be supplied upon request. As a first order approximation, one should consider the following loss estimates: Frequency Band 2500 MHz 4000 MHz 6000 MHz Avg. Ins. Loss of Test Board @ 25°C ~ 0.29dB ~ 0.41dB ~ 0.57dB For example, a 4300MHz, 20dB coupler on a test board may measure –20.60dB from input to the coupled port at frequency F1=4000 MHz. When the loss of the test board is removed, the coupling at F1 becomes -20.19dB (20.60dB + 0.41dB). This compensation must be made to both the coupled and direct path measurements when calculating insertion loss. The loss estimates in the table above come from room temperature measurements. It is important to note that the loss of the test board will change with temperature. This fact must be considered if the coupler is to be evaluated at other temperatures. Orientation Marker A printed circular feature appears on the top surface of the coupler to designate Pin 1. This orientation marker is not intended to limit the use of the symmetry that these couplers exhibit but rather to facilitate consistent placement of these parts into the tape and reel package. This ensures that the components are always delivered with the same orientation. Refer to the table on page 2 of the data sheet for allowable pin configurations. Available on Tape and Reel for Pick and Place Manufacturing. 29 Sep 09 USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Model XMC2560A-20 Rev B Mounting Coupler Mounting Process In order for Xinger surface mount couplers to work optimally, there must be 50Ω transmission lines leading to and from all of the RF ports. Also, there must be a very good ground plane underneath the part to ensure proper electrical performance. If either of these two conditions is not satisfied, insertion loss, coupling, VSWR and isolation may not meet published specifications. Overall ground is improved if a dense population of plated through holes connect the top and bottom ground layers of the PCB. This minimizes ground inductance and improves ground continuity. All of the Xinger hybrid and directional couplers are constructed from ceramic filled PTFE composites which possess excellent electrical and mechanical stability having X and Y thermal coefficient of expansion (CTE) of 17-25 ppm/oC. When a surface mount hybrid coupler is mounted to a printed circuit board, the primary concerns are; ensuring the RF pads of the device are in contact with the circuit trace of the PCB and insuring the ground plane of neither the component nor the PCB is in contact with the RF signal. Mounting Footprint To ensure proper electrical and thermal performance there must be a ground plane with 100% solder connection underneath the part The process for assembling this component is a conventional surface mount process as shown in Figure 1. This process is conducive to both low and high volume usage. Figure 1: Surface Mounting Process Steps Storage of Components: The Xinger products are available in either an immersion tin or tin-lead finish. Commonly used storage procedures used to control oxidation should be followed for these surface mount components. The storage temperatures should be held between 15OC and 60OC. Substrate: Depending upon the particular component, the circuit material has an x and y coefficient of thermal expansion of between 17 and 25 ppm/°C. This coefficient minimizes solder joint stresses due to similar expansion rates of most commonly used board substrates such as RF35, RO4350, FR4, polyimide and G-10 materials. Mounting to “hard” substrates (alumina etc.) is possible depending upon operational temperature requirements. The solder surfaces of the coupler are all copper plated with either an immersion tin or tin-lead exterior finish. Solder Paste: All conventional solder paste formulations will work well with Anaren’s Xinger II surface mount components. Solder paste can be applied with stencils or syringe dispensers. An example of a stenciled solder paste deposit is shown in Figure 2. As shown in the figure solder paste is applied to the four RF pads and the entire ground plane underneath the body of the part. Dimensions are in Inches [Millimeters] USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Available on Tape and Reel for Pick and Place Manufacturing. Model XMC2560A-20 Rev B Reflow: The surface mount coupler is conducive to most of today’s conventional reflow methods. A low and high temperature thermal reflow profile are shown in Figures 5 and 6, respectively. Manual soldering of these components can be done with conventional surface mount non-contact hot air soldering tools. Board pre-heating is highly recommended for these selective hot air soldering methods. Manual soldering with conventional irons should be avoided. Figure 2: Solder Paste Application Coupler Positioning: The surface mount coupler can be placed manually or with automatic pick and place mechanisms. Couplers should be placed (see Figure 3 and 4) onto wet paste with common surface mount techniques and parameters. Pick and place systems must supply adequate vacuum to hold a 0.50-0.55 gram coupler. Figure 3: Component Placement Figure 4: Mounting Features Example Available on Tape and Reel for Pick and Place Manufacturing. 29 Sep 09 USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Model XMC2560A-20 Rev B Figure 5 – Low Temperature Solder Reflow Thermal Profile Figure 6 – High Temperature Solder Reflow Thermal Profile USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Available on Tape and Reel for Pick and Place Manufacturing. Model XMC2560A-20 Rev B Application Information Directional Couplers and Sampling Directional couplers are often used in circuits that require the sampling of an arbitrary signal. Because they are passive, non-linear devices, Anaren directional couplers do not perturb the characteristics of the signal to be sampled, and can be used for frequency monitoring and/or measurement of RF power. An example of a sampling circuit is the reflectometer. The purpose of the reflectometer is to isolate and sample the incident and reflected signals from a mismatched load. A basic reflectometer circuit is shown in Figure ap.n.1-1. Vinput 1 2 LOAD Reflected Wave 4 3 VI VR Figure ap.n.1-1. A Reflectometer Circuit Schematic If the directional coupler has perfect directivity, then it is clear that VI is strictly a sample of the incident voltage Vinput, and VR is strictly a sample of the wave that is reflected from the load. Since directivity is never perfect in practice, both VI and VR will contain samples of the input signal as well as the reflected signal. In that case, VI = C + CDTΓe jθ Eq. ap.n.1-1 and VR = CD + CTΓe jφ Eq. ap.n.1-2 where C is the coupling, D is the directivity, Γ is the complex reflection coefficient of the load, T is the transmission coefficient, and φ and θ are unknown phase delay differences caused by the interconnect lines on the test board. If we know VI and VR, we can easily calculate the reflection coefficient of the load. One should notice that in order to make forward and reverse measurements using only one coupler, the directivity must be really low. In specific customer applications, the preferred method for forward and reverse sampling is shown in Figure ap.n.1-2. Available on Tape and Reel for Pick and Place Manufacturing. 29 Sep 09 USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Model XMC2560A-20 Rev B ISOLATOR INPUT 1 2 LOAD Reflected Wave 4 3 FORWARD MEASUREMENT **TERMINATION REVERSE MEASUREMENT ** RECOMMENDED TERMINATIONS Power (Watts) MODEL 8 RFP-060120A15Z50 15 RFP-250375A4Z50 50 RFP-375375A6Z50 150 RFP-500500A6Z50 Figure ap.n.1-2. Forward and Reverse Sampling The isolator in Figure ap.n.1-2 prevents the reflected wave from exciting the directional coupler. A list of recommended terminations is shown in the figure. Directional Couplers in Feed-Forward Amplifier Applications Feed-forward amplifiers are widely used to reduce distortion due to nonlinearities in power amplifiers. Although the level and complexity of feed-forward amplifiers varies from one manufacturer to another, the basic building block for this linearization scheme remains the same. A basic feed-forward schematic is shown in Figure ap.n.2-1. The input signal is split in two using a hybrid coupler or power divider. The output of the main amplifier is sampled with a 20dB-30dB directional coupler. The XMC2560A-20 is an excellent candidate for this sampling since it provides great return loss and directivity. The sampled signal, which consists of a sample of the original input signal plus some distortion, is inverted and then combined with the output of the first delay line. This procedure subtracts (through destructive interference) the sample of the original input signal, leaving only the distortion or error component. The error component is then amplified and combined with the output of the second delay line using another directional coupler. In many cases, a 10dB coupler is used to combine the two signals (please contact Anaren for corresponding parts). USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Available on Tape and Reel for Pick and Place Manufacturing. Model XMC2560A-20 Rev B 20dB -- 30dB DIRECTIONAL COUPLER OUTPUT DELAY MAIN AMPLIFIER INPUT 10dB DIRECTIONAL COUPLER 3dB HYBRID COUPLER TERMINATIONS ** (see table below) 50 Ohm DELAY ERROR AMPLIFIER ** RECOMMENDED TERMINATIONS Power (Watts) MODEL 8 RFP-060120A15Z50 15 RFP-250375A4Z50 50 RFP-375375A6Z50 100 RFP-500500A6Z50 CARRIER CANCELLATION Figure ap.n.2-1. Generic Feed Forward Circuit Schematic Both directional couplers in the Figure ap.n.2-1 have one port terminated with a 50Ω resistor. In order to achieve optimum performance, the termination must be chosen carefully. It is important to remember that a good termination will not only produce a good match at the input of the coupler, but will also maximize the isolation between the input port and isolated port. Furthermore, since the termination can potentially absorb high levels of power, its maximum power rating should be chosen accordingly. A list of recommended terminations is shown in Figure ap.n.2-1. For an ideal lossless directional coupler, the power at the coupled and direct ports can be written as: Pinput Pcoupled = Coupling ( dB ) Watts Eq. ap.n.2-1 10 10 Pinput Pdirect = Pinput − Coupling ( dB ) 10 Watts Eq. ap.n.2-2 10 where Pinput is the input power in Watts, and Coupling(dB) is the coupling value in dB. Available on Tape and Reel for Pick and Place Manufacturing. 29 Sep 09 USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Model XMC2560A-20 Rev B Packaging and Ordering Information Parts are available in both reel and tube. Packaging follows EIA 481-2. Parts are oriented in tape and reel as shown below. Minimum order quantities are 2000 per reel and 30 per tube. See Model Numbers below for further ordering information. XXX XXXX X - XX X USA/Canada: Toll Free: Europe: (315) 432-8909 (800) 411-6596 +44 2392-232392 Available on Tape and Reel for Pick and Place Manufacturing. Xinger Coupler Frequency (MHz) Size (Inches) XMC 0405 = 400-500 0825 = 800-2500 0525 = 500-2500 1720 = 1700-2000 2325 = 2300-2500 3338 = 3300-3800 2560 = 2500-6000 A = 0.56 x 0.35 B = 1.00 x 0.50 E = 0.56 x 0.20 L = 0.65 x 0.48 M= 0.40 x 0.20 P = 0.25 x 0.20 Coupling Value 03 = 3dB 05 = 5dB 10 = 10dB 20 = 20dB 30 = 30dB Plating Finish P = Tin Lead S = Immersion Tin