APPLICATION NOTE 1945

Performance of Maxim's Cable Upstream Amplifier Meets DOCSIS 2.0 Requirements


Abstract: This application note presents the measured performance of the MAX3514/MAX3516 cable upstream amplifier. The measured data include 2nd Harmonics, 3rd Harmonics, output power vs. frequency, and ACPR. Tests are conducted using DOCSIS 2.0 as the standard, and the amplifiers are found to meet all requirements.

Summary

The upstream CATV amplifiers MAX3514/MAX3516 were tested for compliance to DOCSIS 2.0 PHY Requirements. The test results show that these ICs meet the DOCSIS 2.0 standards.

DOCSIS 2.0

DOCSIS (Data-Over-Cable Service Interface Specification) are RF interface specifications for high-speed data-over-cable systems.

DOCSIS 2.0 is the third generation of the DOCSIS specification. The terms DOCSIS 2.0, DOCSIS 1.1, and DOCSIS 1.0 refer to three different specifications.

The DOCSIS 2.0 specification primarily aims at enhancing the limited upstream physical layer performance of a DOCSIS 1.0- or 1.1-based cable access system. Two new MAC (medium access controller) Management Message Types have been defined, and several new parameter encodings have been defined in the existing MAC messages. A DOCSIS 2.0 CMTS (cable modem termination system) is capable of supporting a higher upstream throughput for a given channel bandwidth as well as increased tolerance to noise experienced in the upstream. DOCSIS 2.0 CMTS is backward compatible with DOCSIS 1.0 and DOCSIS 1.1.

The MAX3514/MAX3516 are a family of programmable-gain upstream amplifiers designed for use in CATV upstream applications. They operate over a frequency range of 5MHz to 65MHz and drives up to +64dBmV QPSK (MAX3516). Since both input and output ports are differential, an external balun at the output port is required. The variable gain feature provides greater than 56dB of dynamic range (MAX3514/MAX3516) and is controlled bya SPI 3-wire interface. Gain control is available in 0.5dB steps (MAX3514/MAX3516) or 1dB step (MAX3510).

Measurements

  • All tests at room temperature.
  • VCC = 5.0V
  • PIN = -13dBm (+34dBmV in 50Ω system, channel power)
  • Input signal:
    • QPSK modulation with 20b PRBS, root cosine filter, α= 0.25
    • 16 QAM modulation with 20b PRBS, root cosine filter, α= 0.25
    • 64 QAM modulation with 20b PRBS, root cosine filter, α= 0.25
  • High Power Mode
  • Input ACPR -66dBc
  • 160kHz measurement bandwidth (200kHz channel spacing)
  • 320kHz measurement bandwidth (400kHz channel spacing)
  • 640kHz measurement bandwidth (800kHz channel spacing)
  • 1280kHz measurement bandwidth (1600kHz channel spacing)
  • 2560kHz measurement bandwidth (3200kHz channel spacing)
  • 5120kHz measurement bandwidth (6400kHz channel spacing)

Corrections and Unit Conversion

  • In 50Ω system, PIN/OUT (dBmV) = PIN/OUT (dBm) + 47dB
  • In 75Ωsystem, PIN/OUT(dBmV) = PIN/OUT (dBm) + 49dB
  • MAX3514/MAX3516EVKit boards have 7.5dB minimum loss pad at the output,so POUT (dBmV) = POUT (dBm) + 47dB + 7.5dB + cable loss

Test Equipment List

(See Figure 1 for typical test setup)
  • Signal Generator capable of generating 64 QAM signals (RODHE & SCHWARZ SMIQ 06B)
  • Spectrum Analyzer (RODHE & SCHWARZ FSEB)
  • Power Meter (HP437B)
  • Power Sensor (HP8482A)
  • Power Supply (Agilent E3632A)
  • DMM (HPE3631A)
Figure 1. Test equipment set up.
Figure 1. Test equipment set up.

Results

Test Signal:

Modulation = 64
QAM Alpha = 0.25
Modulation Signal Center
Frequency = 22MHz Symbol Rates: 160ksps, 320ksps, 640ksps, 1280ksps, 2560ksps, 5120ksps

Table 1. The MAX3514 2nd and 3rd Harmonic vs. Output Power and Frequency : (+54dBmV to +58dBmV)
22MHz (160ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 6.8 53.8 -61.7 -60.0
-13 110 7.8 54.8 -61.8 -60.0
-13 112 8.8 55.8 -61.9 -59.8
-13 114 9.8 56.8 -62.1 -59.4
-13 116 10.8 57.8 -62.3 -59.0
22MHz (320ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 6.9 53.9 -61.0 -59.8
-13 110 7.9 54.9 -61.3 -59.7
-13 112 8.9 55.9 -61.4 -59.5
-13 114 9.9 56.9 -61.6 -59.2
-13 116 10.9 57.9 -61.7 -58.8
22MHz (640ksps) Input (dBm) GCW Output(dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 6.8 53.8 -59.8 -58.6
-13 110 7.8 54.8 -60.0 -58.6
-13 112 8.8 55.8 -60.2 -58.7
-13 114 9.8 56.8 -60.4 -58.6
-13 116 10.8 57.8 -60.6 -58.8
22MHz (1280ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 109 7.1 54.1 -58.4 -58.0
-13 111 8.1 55.1 -58.8 -58.1
-13 113 9.1 56.1 -59.1 -58.1
-13 115 10.1 57.1 -59.2 -57.7
-13 117 11.0 58.0 -59.4 -57.4
22MHz (2560ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 109 7.0 54.0 -56.1 -56.5
-13 111 8.0 55.0 -56.3 -56.9
-13 113 9.0 56.0 -56.6 -57.2
-13 115 10.0 57.0 -57.0 -57.3
-13 117 11.0 58.0 -57.2 -56.7
22MHz (5120ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 109 7.1 54.1 -53.5 -54.6
-13 111 8.1 55.1 -54.1 -55.0
-13 113 9.1 56.1 -54.6 -55.1
-13 115 10.1 57.1 -54.9 -55.1
-13 117 11.1 58.1 -55.4 -55.3


Table 2. DOCSIS 2.0 Specifications on 2nd and 3rd Order Harmonics (57dBmV output)
Modulation Rate (ksps) 160 320 640 1280 2560 5120
2nd order harmonics DOCSIS 2.0 Spec. (dBc) -47 -50 -50 -50 -50 -50
3rd order harmonics DOCSIS 2.0 Spec. (dBc) -47 -50 -50 -50 -50 -50

Figure 2.
Figure 2.

Figure 3.
Figure 3.

Table 3. The MAX3516 2nd Harmonic vs. Output Power and Frequency (+57dBmV to +61dBmV)
22MHz (160ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 10.0 57.0 -66.0 -60.7
-13 110 11.0 58.8 -66.5 -60.7
-13 112 12.0 59.0 -67.0 -59.7
-13 114 13.0 60.0 -67.7 -58.4
-13 116 14.0 61.0 -68.5 -56.5
22MHz (320ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 10.0 57.0 -64.8 -60.3
-13 110 11.0 58.0 -65.1 -60.0
-13 112 12.0 59.0 -65.6 -59.1
-13 114 13.0 60.0 -66.3 -58.0
-13 116 14.0 61.0 -67.0 -56.4
22MHz (640ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 10.0 57.0 -63.1 -59.8
-13 108 11.0 58.0 -63.4 -59.8
-13 110 12.0 59.0 -63.7 -59.1
-13 112 13.0 60.0 -64.4 -58.4
-13 114 14.0 61.0 -65.0 -56.6
22MHz (1280ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 10.0 57.0 -61.2 -59.1
-13 110 11.0 58.0 -61.3 -59.0
-13 112 12.0 59.0 -61.8 -58.5
-13 114 13.0 60.0 -62.2 -57.5
-13 116 14.0 61.0 -62.7 -56.0
22MHz (2560ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 9.8 56.8 -58.0 -57.7
-13 110 10.8 57.8 -58.5 -57.7
-13 112 11.8 58.8 -59.0 -57.4
-13 114 12.8 59.8 -59.5 -56.7
-13 116 13.8 60.8 -59.8 -55.6
22MHz (5120ksps) Input (dBm) GCW Output (dBm) Output (dBmv) 2nd Harm (dBc) 3rd Harm (dBc)
-13 108 9.8 56.8 -55.3 -55.7
-13 110 10.8 57.8 -55.7 -55.8
-13 112 11.8 58.8 -56.0 -55.8
-13 114 12.8 59.8 -56.3 -55.4
-13 116 13.8 60.8 -56.7 -54.6


Table 4. DOCSIS 2.0 Specifications on 2nd and 3rd Order Harmonics (60dBmV output)
Modulation Rate (ksps)
160
320
640
1280
2560
5120
2nd order harmonics DOCSIS 2.0 Spec. (dBc)
-47
-50
-50
-50
-50
-50
3rd order harmonics DOCSIS 2.0 Spec. (dBc)
-47
-50
-50
-50
-50
-50

Figure 4.
Figure 4.

Figure 5.
Figure 5.

Table 5. The MAX3514 ACPR vs. Output Power and Frequency
39MHz (160ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
7.0
54.0
-55.5
-13
111
8.0
55.0
-54.4
-13
113
9.0
56.0
-53.2
-13
115
10.0
57.0
-52.0
-13
117
11.0
58.0
-50.9
39MHz (320ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
7.0
54.0
-54.8
-13
111
8.0
55.0
-54.2
-13
113
9.0
56.0
-53.3
-13
115
10.0
57.0
-52.2
-13
117
11.0
58.0
-51.0
39MHz (640ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
7.0
54.0
-53.9
-13
111
8.0
55.0
-53.3
-13
113
9.0
56.0
-52.1
-13
115
10.0
57.0
-51.4
-13
117
11.0
58.0
-50.2
39MHz (1280ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
6.8
53.8
-52.2
-13
111
7.8
54.8
-51.6
-13
113
8.8
55.8
-50.8
-13
115
9.8
56.8
-50.0
-13
117
10.8
57.8
-48.6
39MHz (2560ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
7.0
54.0
-49.3
-13
111
8.0
55.0
-48.4
-13
113
9.0
56.0
-48.0
-13
115
10.0
57.0
-47.1
-13
117
11.0
58.0
-46.3
39MHz (5120ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
6.8
53.8
-46.2
-13
111
7.8
54.8
-45.6
-13
113
8.8
55.8
-45.1
-13
115
9.8
56.8
-44.3
-13
117
10.8
57.8
-43.5


Table 6. Adjacent Channel Power Ratio DOCSIS 2.0 Specifications
Modulation Rate (ksps) 160 320 640 1280 2560 5120
ACPR DOCSIS 2.0 SPec. (dBc)
-47
-47
-46
-45
-44
-42

Table 7. The MAX3516 ACPR vs. Output Power and Frequency
39MHz (160ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
10.2
57.2
-52.0
-13
111
11.2
58.2
-50.9
-13
113
12.2
59.2
-49.4
-13
115
13.2
60.2
-47.8
-13
117
14.2
61.2
-46.0
39MHz (320ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
108
9.9
56.9
-52.2
-13
110
10.8
57.8
-50.9
-13
112
11.8
58.8
-49.8
-13
114
12.8
59.8
-48.4
-13
116
13.8
60.8
-46.9
39MHz (640ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13
109
10.3
57.3
-50.7
-13
111
11.2
58.2
-49.8
-13
113
12.2
59.2
-48.7
-13 115 13.2 60.2 -47.3
-13 117 14.2 61.2 -45.7
39MHz (1280ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13 109 10.1 57.1 -49.6
-13 111 11.0 58.0 -48.7
-13 113 12.1 59.1 -47.6
-13 115 13.0 60.0 -46.5
-13 117 14.0 61.0 -44.9
39MHz (2560ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13 109 10.2 57.2 -46.7
-13 111 11.1 58.1 -46.0
-13 113 12.1 59.1 -45.0
-13 115 13.1 60.1 -43.8
-13 117 14.1 61.1 -42.6
39MHz (5120ksps) Input (dBm) GCW Output (dBm) Output (dBmv) ACPR (dBc)
-13 109 10.2 57.2 -43.8
-13 111 11.2 58.2 -43.1
-13 113 12.2 59.2 -42.2
-13 115 13.2 60.2 -41.4
-13 117 14.2 61.2 -40.3


Table 8. Adjacent Channel Power Ratio DOCSIS 2.0 Specifications
Modulation Rate (ksps) 160 320 640 1280 2560 5120
ACPR DOCSIS 2.0 SPec. (dBc) -47 -47 -46 -45 -44 -42

Figure 6.
Figure 6.

Figure 7.
Figure 7.

Conclusion

The test results in Table 1, 3, 5, 7 show that MAX3514/MAX3516 meet the DOCSIS 2.0 standards.