Common Mode Filter＜Common Mode Eliminator＞
CDKF-Type R-Suffix
CDKF type-R is based on our current CDKF-type delay line. We have added the functionality to eliminate common mode noise in differential signal transmissions and created the Common Mode Eliminator. It corresponds to the transmission speed of 10Gbps.
It has become necessary to have a plan to deal with common mode noise which is generated from interval skew in differential signals in ultra-high-speed serial differential signal transmissions. Developed to deal specifically with this necessity, this product automatically eliminates interval skew common mode noise internally.
The input common mode noise is offset within the delay line structure from the partially-reflected common mode noise, the noise is not superimposed.
Also, because it is non-magnetic, there is no magnetic loss. It is well-suited for dealing with common mode noise from high-speed differential signal transmissions over 5Gbps.
Also, because this product is based on our CDKF-type delay line, to which we have added functionality to eliminate common mode noise, we can also add our guarantee the accuracy of our delay lines.
This product is a layered ceramic chip type LTCC part and is RoHS-compliant.
S-parameter files (Touchstone format) and SPICE models for each component can be provided.
Care and Handling of LTCC Products
There is a smaller CDLD type of 0805 size and 10Gbps correspondence.
 Moves to the page of the CDLD type
Common Specifications （provisional）
| Input/Output Impedance: |
Differential 100Ω±10%* |
| Interval Skew Auto-Adjust Time: |
1/4Pw (Pw Spec: 1Unit Interval pulse width <200ps) |
| Waveform Distortion: |
Overshoot/Preshoot under ±20% |
| Output Rise Time: |
45ps Typ. (20%-80%) |
| DC Resistance: |
1Ω Max. |
| Delay Time Temp. Coefficient: |
0-150ppm/°C |
| Insulation Resistance: |
DC50V, over 100MΩ |
| Durable Voltage: |
DC50V, 1 minute |
| Rated Current: |
100mA |
| Rated Voltage: |
5V |
| Operating Temperature Range: |
－40°C to +85°C |
| Storage Temperature Range: |
－40°C to +120°C |
| * Single-ended operation will not produce usable waveforms. |
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| Part Number |
Transmission Speed (1)* |
-3dB Passband (2)* |
Delay Time |
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CDKF10R
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6G～10Gbps |
DC～15GHz Typ. |
100ps±25ps |
| CDKF15R |
5.5G～7.3Gbps |
DC～11GHz Typ. |
150ps±25ps |
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CDKF20R
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5G～7Gbps |
DC～10.5GHz Typ. |
200ps±25ps |
(1)* When using the recommended Land Pattern.
(2)* Using the recommended Land Pattern, when there is no skew in the differential input signal.
Maximum value at the transmission speed: when passing waveform at 1Unit Interval became like the sine wave (Please See Technical Note 2)
| Part Number |
Transmission Speed
(Maximum values) (3)* |
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CDKF10R
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16Gbps |
| CDKF15R |
12.5Gbps |
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CDKF20R
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10Gbps |
(3)* When using the recommended Land Pattern.
Unit:mm(inch)
Tolerance:±0.15(±0.006) |
Tape and Reel specifications
In order to accommodate automatic mounting, we provide Tape & Reel packaging. The package is embossed with cover tape and contains 500pcs per reel, as shown below. The reel is marked with supplier name, part number, quantities, and lot number.
Unit:mm (inch)
Tolerance:±0.1(±0.004)
T: 5(0.197)Max
Direction of Feed
No 1 pin
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DIMENSIONS OF REEL
Unit:mm (inch)
Tolerance:±0.1(±0.004)
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Characteristics Examples
(1)Frequency Characteristics
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Top: Elimination of Common Mode Noise, Pass-thru and Reflection Ratio
Middle: Sdd21 Differential Signal Pass-thru Amplitude Characteristics
Bottom: Scc21Common Mode Pass-thru Amplitude Characteristics
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CDKF10R
(Electro-magnetic Simulation)
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CDKF15R
(Electro-magnetic Simulation)
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Frequency[GHz]
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Frequency[GHz]
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CDKF20R
(Actual Part)
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Frequency[GHz]
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(2)Response waveform of Pseudo-Random Bit Sequence
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Technical Note 1: Frequency Characteristics of Common-Mode Impedance
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| For the CDKF type-R and the ideal common-mode choke coil (hereafter, ideal CMC), the frequency characteristics of common-mode impedance are calculated with a circuit simulator and the difference is verified. The equivalent circuit and the main characteristics of the ideal CMC are shown in Fig. 1. As much as possible, the －3dB passband was made wideband. |
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－3dB passband: 16.6GHz
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Fig.1 Equivalent circuit and main characteristics of the ideal CMC
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The method utilized for calculating common-mode impedance is shown below.
In general, common-mode impedance (Zcom) Fig. 2, is generated by a common-mode choke coil from common-mode noise. That value can be calculated from this circuit. Conversely, because the structure of the CDKF type-R absorbs and removes the common-mode noise within the Signal Line-GND circuit, common-mode impedance (Zcom) can be calculated from the circuit arranged and shown in Fig. 3.
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Fig.2 Generation chart and calculation common-mode choke coil Zcom
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Fig.3 Generation chart and calculation circuit of CDKF type-R Zcom
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| Fig. 4 shows the frequency characteristics of the
ideal CMC and CDKF type-R Common-mode
impedance from the calculation circuits in
Figs. 2 and 3. Here, the ideal CMC uses a circuit
simulation S-parameter while the CDKF type-R
uses S-parameter derived by the electro-magnetic
simulation.
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Fig.4 Frequency characteristics of Common-mode impedance
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The ideal CMC intercepts the common-mode noise by generating high impedance within the signal line. As shown in Fig. 4, it appears to be effective in the vicinity of 2GHz. However, the inclination of the frequency characteristics is quite steep. Common-mode impedance is reduced as it diverges from 2GHz, and the intercept function decreases.
On the other hand, the CDKF type-R is set to the value from the signal-GND circuit corresponding to the common-mode impedance which is constant and small and has a fairly smooth frequency response. There appears to be an advantage to being able to lower the dependency on the frequency and to do a wideband absorptive removal of the common-mode noise.
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Technical Note 2: Transmission Speed
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| The differential frequency characteristics (Sdd21) of a differential transmission line with a 30ps skew are shown in Fig. 1. In Fig. 1, a differential signal is intercepted to become a complete common mode signal at 16.7GHz because the 30ps skew makes a 180° phase shift at that frequency. Transmission of the differential signal forms an attenuation pole at 16.7GHz and the －3dB passband becomes DC to 8.3GHz. |
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－3dB Passband: DC～8.3GHz |
Fig. 1 Differential frequency characteristics (Sdd21) of differential transmission line with 30ps Skew
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0s Skew (－3dB Passband: DC～11.2GHz) |
| 30ps Skew (－3dB Passband: DC～6.5GHz) |
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Fig.2 Differential frequency characteristics (Sdd21) with CDKF15R connected in the differential transmission line shown in above.
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Next, the CDKF15R frequency characteristics of the differential input signal skew of 0s, 30ps are shown in Fig. 2.
In Fig. 2, compared to the －3dB passband of 0s skew, the －3dB passband of 30ps skew is greatly reduced. However, as clearly indicated in Fig. 1, the cause is not due to the effects of the CDKF15R; rather, it is determined by skew generated by the transmission line. That is, the quality of the differential output waveform probably does not depend on the CDKF type-R －3dB passband. Rather, it depends on the value of the skew when the CDKF type-R is connected for skew cancellation. It can be assumed to become like the sine wave to which the high-order harmonic is missed in 1Unit Interval corrugating according to the transmission speed.
Therefore, the corresponding transmission speed of CDKF type-R is not only calculated simply from its －3dB passband, when the skew was generated, the maximum value at the correspondence transmission speed to which output waveform fineness was able to be maintained was examined on the assumption that passing waveform at 1Unit Interval became like the sine wave according to the characteristic of Fig. 1.
As a result, we judged that it was possible to correspond enough up to the transmission speed described in the appendix.
In addition, our CSKF-type not only cancels the skew but also restores the differential transmission signal. If the rough skew is canceled by the CSKF-type and the residual skew is canceled by the CDKF type-R, it is possible to balance the differential signal completely.
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RoHS Compliance Status
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RoHS-compliant
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Notes
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Always connect the GND terminals. Using this product without connecting the GND could cause deterioration of the common mode noise elimination and delay line functions.
Also, use of only one line will not yield a normal wave form and cannot be used.
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