中華民國業餘無線電促進會北部分會

標題: 網路分析儀 - 高頻儀器之王 [打印本頁]

作者: BX2ADJ 時間: 2012-8-21 22:35 標題: 網路分析儀 - 高頻儀器之王

Dear OM,

這是我的看法: 網路分析儀 -- 乃 -- 高頻儀器之王
DIY 如果有這種儀器, 會比較容易調整, 比較容易成功 !
http://en.wikipedia.org/wiki/Network_analyzer_(electrical)

HP 牌子 " 向量網路分析儀 " 一般在台幣百萬元以上! (OL 有一台? )
二手的大半在十萬至三十萬元較多,

我最近得到幾千元一組的 " 純量網路分析儀 " 十分興奮!
DIY 使用 " 純量網路分析儀 " 應該夠了
這組是 NWT500 掃頻儀 + 駐波電橋 + USB 連線 + WinNWT4 電腦軟體
http://item.taobao.com/item.htm?id=14073761462

不過若要理解, 會需要一些理論知識...

73 BM2CAJ

作者: BX2ADJ 時間: 2012-8-21 22:42

QUOTE:

原帖由 BM2CAJ 於 2012-8-21 10:35 PM 發表
Dear OM,
這是我的看法: 網路分析儀 -- 乃 -- 高頻儀器之王
DIY 如果有這種儀器, 會比較容易調整, 比較容易成 � !
http://en.wikipedia.org/wiki/Network_analyzer_(electrical)
HP 牌子 " 向量網 ...

用 NWT500 掃頻儀測量 Diamond X200 GP天線 在 VHF 與 UHF 的 SWR 駐波比:

135 ~ 150MHz

420 ~ 440MHz

73 BM2CAJ

作者: BX2ADJ 時間: 2012-8-21 22:49

QUOTE:

原帖由 BM2CAJ 於 2012-8-21 10:42 PM 發表
用 NWT500 掃頻儀測量 Diamond X200 GP天線在 VHF 與 UHF 的 SWR 駐波比:
135 ~ 150MHz
420 ~ 440MHz
73 BM2CAJ

用 NWT500 掃頻儀測量 Diamond D130 GP 雨傘形寬頻接收天線 在 VHF 與 UHF 的 SWR 駐波比:
發現頻寬相當寬!

45KHz ~ 505MHz

73 BM2CAJ

作者: BX2ADJ 時間: 2012-8-21 23:00

QUOTE:

原帖由 BM2CAJ 於 2012-8-21 10:49 PM 發表
用 NWT500 掃頻儀測量 Diamond D130 GP 雨傘形寬頻接收天線在 VHF 與 UHF 的 SWR 駐波比:
發現頻寬相當寬!
45KHz ~ 505MHz
73 BM2CAJ

用 NWT500 掃頻儀測量 DIY 20米 Dipole天線 (約10米長, 縮短率約 0.95) 的 SWR 駐波比:
發現諧振頻率在 13MHz 左右! 有空時要裁短, 希望調到 14MHz 左右...

10 ~ 15MHz

花幾千元, 得到原本要百萬元才可能得到的結果,

啊! 真是太高興了! ! !

73 BM2CAJ

p.s. 下次要測 pre-amp 的頻率響應... 待續...

作者: BM1CDP 時間: 2012-8-22 06:21

蕭醫生可以分享更多有關相關資訊,如軟體及電橋那裡可購得?
3Q
73
BM1CDP

作者: BX2AL 時間: 2012-8-22 09:38

QUOTE:

原帖由 BM2CAJ 於 2012-8-21 22:35 發表
Dear OM,

這是我的看法: 網路分析儀 -- 乃 -- 高頻儀器之王
DIY 如果有這種儀器, 會比較容易調整, 比較容易成 � !
http://en.wikipedia.org/wiki/Network_analyzer_(electrical)

HP 牌子 " 向量網 ...

Dear BM2CAJ OM:
前一陣子也找了一下網路分析儀,就如您說的,還真貴,
看您的成果感覺還真夠用,好想ORDER一組.

73 de BX2AL

作者: BM4AIK 時間: 2012-8-22 11:42 標題: 《◎》

看來比天線分析儀還方便查SWR的變化.
有沒有整組團購呀？

作者: BX4ABD 時間: 2012-8-22 15:35

N2PK VNA 是窮人的向量網路分析儀, 適合HF. http://n2pk.com/http://www.makarov.ca/vna.htm
有賣PCB, 但零件要自己買. 很費工.
de BX4ABD. ex BM4JKB

作者: BX2ADJ 時間: 2012-8-22 22:24

QUOTE:

原帖由 BM1CDP 於 2012-8-22 06:21 AM 發表
蕭醫生可以分享更多有關相關資訊,如軟體及電橋那裡可購得?
3Q
73
BM1CDP

BM1CDP
BX2AL
BX4ABD ex BM4JKB
DR OM,

在下沒料到這裏會有這麼熱烈的反應,
很高興很多朋友對這個話題感到興趣, 可見很多朋友都已經研究到很專業了,
真的很高興!
那麼大家應該可以理解我不是打廣告, 是便宜好物分享!

以下稍微整理連結:

-----掃頻儀--------
NWT500掃頻儀,USB接口 (0.1MHz-550MHz)
http://item.taobao.com/item.htm?spm=0.0.0.57&id=14073761462

NWT150掃頻儀,USB接口 (0.05-300MHz)
http://item.taobao.com/item.htm?spm=0.0.0.100&id=10893423510

NWT7掃頻儀,USB供電 (0.05-85MHz)
http://item.taobao.com/item.htm?spm=0.0.0.66&id=10254795980

鋁外殼
http://item.taobao.com/item.htm?spm=0.0.0.96&id=10848263334
--------------------
.
.
-----SWR 駐波電橋----
1MHz-500MHz
http://item.taobao.com/item.htm?spm=0.0.0.57&id=15022844565

10MHz-1GHz
http://item.taobao.com/item.htm?spm=2013.1.0.182&id=10071926704
---------------------
.
.
----- WinNWT v4 下載 ------
http://www.dl4jal.eu/hfm9.htm
.
.
----- 衰減器 ----------------
(因為沒有內建, 要買 -6dB 與 -40dB 才可校正儀器)
http://item.taobao.com/item.htm?spm=a1z10.3.17.23&id=10822658485&_u=m8qeulfc529
.
.
還需要買一些 SMA 轉 BNC, 或 SMA 轉 M 的轉接頭,
似乎台灣比較便宜方便, 電子廣場B1 源達旁邊有賣,
.
組合用法請參考第一張照片,

祝大家實驗愉快!

73 de BM2CAJ

[ 本帖最後由 BM2CAJ 於 2012-8-22 22:26 編輯 ]

作者: BX2ADJ 時間: 2012-8-23 01:26

QUOTE:

原帖由 BM4AIK 於 2012-8-22 11:42 AM 發表
看來比天線分析儀還方便查SWR的變化.
有沒有整組團購呀？

BM4AIK,

可以掃頻畫出曲線的 " 天線分析儀 " 有一款可攜式的

KVE-60A 圖示短波天線分析儀
http://item.taobao.com/item.htm?spm=a1z0k.1000775.3.281&id=14966218052

對岸論壇的風評不錯, 我有考慮要買, ( 疑? 會不會有團購? )
http://www.hellocq.net/forum/read.php?tid=297055&fpage=2

*************************

網路分析儀還可測濾波器, 前置放大器, etc 的頻率響應,
測震盪器, 混頻器, etc 的輸出頻譜,
做頻譜分析儀, (但靈敏度應該沒有 SDR 接收機的頻譜好),
還可測阻抗, 做匹配 (這部分我比較不熟)
當天線分析儀只是其中一種功能 ...

73 de BM2CAJ

[ 本帖最後由 BM2CAJ 於 2012-8-23 01:30 編輯 ]

作者: bx3aaq 時間: 2012-8-23 17:36

Try to google "DG8SAQ VNWA" or go following link"http://www.sdr-kits.net/VNWA/VNWA_Description.html" It is a VNA to cover frequency range from 1K to 1.3GHz(the spec is reduced for frequency above 500MHz with harmonics mixing). It can also work as signal generator and spectrum analyzer.

The designer(DG8SAQ) is a Germany professor, and he is active to update the control software regularly over "VNWA" yahoo group. I much appreciate the software's capability.

To compare with Agilent's HP8753E, the measurement difference is negligible

ps. it cost about $15000 NTD

73,
BX3AAQ

作者: BX2ADJ 時間: 2012-8-23 22:19

QUOTE:

原帖由 bx3aaq 於 2012-8-23 05:36 PM 發表
Try to google "DG8SAQ VNWA" or go following link"http://www.sdr-kits.net/VNWA/VNWA_Description.html" It is a VNA to cover frequency range from 1K to 1.3GHz(the spec is reduced ...

BX3AAQ

感謝您的分享!

以功能與規格來看, 這個 VNWA 是更好,
它是 " 向量網路分析儀 " 而且同時檢測輸入波 S11 與反射波 S21
網頁宣稱效果與 HP 儀器無異!
不知您是否用過? 可以分享一下嗎?

p.s. 網頁牌價是 Price: £474.00 (plus shipping) = 474 英鎊

73 BM2CAJ

作者: bv2ck 時間: 2012-8-24 11:55

蕭醫師這只能算是頻譜分析儀吧？

作者: BX2ADJ 時間: 2012-8-24 21:13

QUOTE:

原帖由 bv2ck 於 2012-8-24 11:55 AM 發表
蕭醫師這只能算是頻譜分析儀吧？

或許可以問 BV2OL 或其他前輩,
依我的認知是接近 " 純量網路分析儀 "

頻譜分析儀只有一個信號輸入口,
如果只用 " 頻譜分析儀 " 是不能得到天線 SWR 曲線,
除非頻譜分析儀, 加上追蹤信標掃描, 再加上駐波電橋,
才可得到天線 SWR 曲線,
但這樣的架構就與這套 " 掃頻儀 " 差不多了,

頻譜分析儀也沒有上一帖說的那些功能..
如果只要 " 頻譜分析儀 ", 用 " 電視棒 SDR 接收機 " 加軟體就是了!

[ 本帖最後由 BM2CAJ 於 2012-8-24 21:15 編輯 ]

作者: BX2ADJ 時間: 2012-8-24 22:16

QUOTE:

原帖由 bv2ck 於 2012-8-24 11:55 AM 發表
蕭醫師這只能算是頻譜分析儀吧？

問題真的是解答的驅力,
為了回答問題, 趕快測一下:

455KHz 陶瓷濾波器的頻率響應 ~ ~

臨時找來舊饋線與鱷魚夾, 已經生銹了, 還好堪用,
沒有做 50歐阻抗匹配, 所以頻峰與頻寬不大準,
但曲線還算漂亮...

73 de BM2CAJ

作者: BX2ADJ 時間: 2012-8-24 22:24

QUOTE:

原帖由 BM2CAJ 於 2012-8-24 10:16 PM 發表
問題真的是解答的驅力,
為了回答問題, 趕快測一下:
但曲線還算漂 ...

4.5MHz 濾波器的頻率響應 ~ ~

臨時找來舊饋線與鱷魚夾, 已經生銹了, 還好堪用,
沒有做 50歐阻抗匹配, 所以頻峰與頻寬不大準,
曲線應該算很漂亮! 測得濾波器 -6dB 頻寬 152KHz ...

73 de BM2CAJ

作者: BX2ADJ 時間: 2012-8-24 23:22

QUOTE:

原帖由 BM2CAJ 於 2012-8-24 10:24 PM 發表
4.5MHz 濾波器的頻率響應 ~ ~

測出興趣來了, 再來測:

455KHz 中周變壓器 (黃色) 的諧振頻率 ~ ~

臨時找來舊饋線與鱷魚夾, 已經生銹了, 還好堪用,
沒有做 50歐阻抗匹配, 所以頻峰與頻寬可能不大準,

曲線應該算很漂亮! 調整前測得諧振頻率約 530KHz ! ! !
轉大約一圈, 調整後測得諧振頻率約 455KHz
-6dB 頻寬約 37.6KHz ...

看來如果中周沒調好, 接收機是會完全沒有信號的!

73 de BM2CAJ

作者: BX2ADJ 時間: 2012-8-25 14:52

QUOTE:

原帖由 bv2ck 於 2012-8-24 11:55 AM 發表
蕭醫師這只能算是頻譜分析儀吧？

不好意思, 我想一想,

可能我興奮過頭了, 所以稱網路分析儀是: 高頻儀器之王, 或許不是很恰當,
如果說是: DIY高頻儀器之王, 也許好一些?

論價錢, 這個儀器是非常貴沒錯, 但確實也非全能的,
在維修與調整的情況, 也不一定要用,
像調整機子裏的中周, 可能用示波器還比較好?
調整頻率, 精度應該比不上計頻儀...

以上想法僅供參考...

73

作者: bx3aaq 時間: 2012-8-25 17:19

Yes, DG8SAQ's VNWA is a VNA(Vector Network Analyzer).
You can measure the 4 S-parameter - S11/S21/S12/S22.

We have the VNWA and HP8753E in the lab. For measuring the filter/attenuator/amplifier, VNWA and HP8753E get close result. Of course, you need to do a good calibration(SOLT - short, open, load, through) for getting an accurate result.

We are also trying to model crystal resonator's parameter and work as LCR meter with measured S-parameter.

There are similar portable VNA, from N2PK or Array Solutions VNA2180. The VNWA has the widest frequency range.

As I mention, I most appreciate the control software for VNWA. DG8SAQ will get feedback from user and update it frequently. In the past time, I had some questions and found bug about the software, DG8SAQ respond to me quickly.

You can install and operate the software to feel its power even though you don't have the VNWA hardware.

About its price, ￡474 bp is kit form, VNWA only is ￡400 bp, but I miscount it as Euro!

73,
BX3AAQ

作者: BX2ADJ 時間: 2012-8-26 16:10

QUOTE:

原帖由 bx3aaq 於 2012-8-25 05:19 PM 發表
Yes, DG8SAQ's VNWA is a VNA(Vector Network Analyzer).
You can measure the 4 S-parameter - S11/S21/S12/S22.
We have the VNWA and HP8753E in the lab. For measuring the filter/attenuator/amplifi ...

BX3AAQ,

Thank you very much for your comment and feedback.
I appreciate your reply very much. Finally someone can understand what I was talking about.
I feel more comfortable now.

But actually I am amateru, not professional about vector network analyzer.
Scalar NA is easier for me. I know that vector NA is far more powerful.
DG8SAQ's VNWA is really very attractive to me. I will try it.
Thank you very much again!

Best 73 de BM2CAJ

作者: BM1CDP 時間: 2012-8-29 13:32

QUOTE:

原帖由 BM2CAJ 於 2012-8-22 22:24 發表

BM1CDP
BX2AL
BX4ABD ex BM4JKB
DR OM,

在下沒料到這裏會有這麼熱烈的反應,
很高興很多朋友對這個話題感到興趣, 可見很多朋友都已經研究到很專業了,
真的很高興!
那麼大家應該可以理解我不是打廣告 ...

BM2CAJ您好:
請教一下,看過原商家網站出示如下:
特点：支持对数、线性检测，带0-50DB衰减器，
能进行阻抗、驻波等测量
仍需要另購買-6及-40固定衰減器嗎?
感謝分享.

作者: BX2ADJ 時間: 2012-8-29 18:29

QUOTE:

原帖由 BM1CDP 於 2012-8-29 01:32 PM 發表
BM2CAJ您好:
請教一下,看過原商家網站出示如下:
特点：支持对数、线性检测，带0-50DB衰减器，
能进行阻抗、驻波等测量
仍需要另購 ...

BM1CDP 您好:

商品是寫 " 带0-50DB衰减器 " 沒錯,
可是用 WinNWT4 軟體勾選衰减-50dB之後, 可聽見繼電器跳二聲, 軟體又跳回衰减 0dB,
沒辦法使用內建 -50dB衰减器，據賣家說這樣是正常 (?)

照說明書: 另購 -6dB 與 -40dB衰减器，是校正用的, 沒太貴, 還是買吧!

另要注意: 輸入端要小於 < 10dBm 否則會燒壞!
所以測放大器之前, 也是要加衰减器 (我買 -6dB一個, -20dB二個, -40dB三個, 好用)
衰减器要買 SMA 頭的 (50歐)
露天有賣 F 頭的 (應該是 75歐) 應該不能用, 我差一點買錯!

上面淘X連結, 是我找很久, 找到比較好, 又相對便宜的, 您可比較一下...

祝實驗愉快!

73 BM2CAJ

作者: BX2ADJ 時間: 2012-9-10 22:51

QUOTE:

Hi, BX3AAQ,

I am about to buy VNWA 3E with calibration kits.
May I ask you a question that why the spectrum analyzer is only up to 100MHz?

** (VNWA 3) Coverage from 1 kHz to 500 MHz with dynamic range of up to 90dB Useful performance up to 1.3 GHz with reduced dynamic range and accuracy

** Basic Spectrum Analyzer useful up to 100 MHz

Why? And What will you use for spectral analysis?

( The spectral analyzer of my 掃頻儀 showed a flat line! )

Thank you!

73 de BM2CAJ

作者: bx3aaq 時間: 2012-9-13 17:43

Hi, BM2CAJ
VNWA 3E is the latest model, you don't have to change measurement direction for getting the 4 S-parameter.

Why the VNWA3 work as spectrum analyzer with frequency limitation to 100MHz ? My long explanation as follow(maybe wrong

1. There are some technical articles and discussion over QEX
a. "A Low Budget Vector Network Analyzer for AF to UHF", QEX 2007 Mar/Apr
b. QEX Letter about "A Low Budget Vector Network Analyzer for AF to UHF", QEX 2007 Jul/Aug
c. "A Small, Simple, USB-Powered Vector Network Analyzer Covering 1 kHz to 1.3 GHz", QEX 2009/Jan-Feb
The VNWA has two ADI's AD9859 DDS. They are phase aligned together to downconvert the through/reflect signal to audio band at 1KHz. These signal are sampled with audio codec and transferred to computer via USB interface for further processing.
2. For DDS-based frequency generator, the most issue is spur frequency components(including the aliases and harmonics) and the output frequency will limit to about 1/3 of the operation clock. The claimed AD9859 operation clock is 400MHz(DG8SAQ measured to exceed 500MHz), so the fundamental DDS output frequency is limited to 133MHz.
The output alias frequency of DDS are calculated as N*F_clk +/- F_fund, N=1 to 3(shapped by Sinc function).
For example, Fclk=400MHz and F_fund=100MHz, then the aliases will locate at 300M(1st alias), 500M(2nd alias), 700M(3rd alias), 900M(4th alias), 1100M(5th), 1300M(6th)
The tricky part of VNWA is using the alias signal to extend the measurable frequency range to 1.3GHz.

3. VNWA to works as a network analyzer, the signal over port1 and port2 is fed by VNWA itself, and its frequency components are more predicable, and the unexpected signal can be further processed by computer program.
VNWA to works as a spectrum analyzer, port1 signal is fed outside. If we don't install anti-alias filter over port1, all the harmonics will mix with the aliases and foldback to the interested band to confuse us. I think that is the reason, VNWA only select the F_fund(above calculation as 133MHz) and limit its usable frequency range to 100MHz.

To talk in short, VNWA may operate over 100MHz as a spectrum analyzer, but you had better to understand the measured frequency components in advance.

In the field try, we use the VNWA as spectrum analyzer to collect the spectrum signal over the power line with frequency range to 1MHz. It works fine for that application, but we will treat the measured spectrum as a relative value instead a absolute value.

For portable spectrum analyzer, you may check the Aaronia HF series.

ps.
1. If you are interested about the QEX articles, I can pass them to you.
2. If you has question about VNWA, you can also ask Tom DG8SAQ directly over the Yahoo group. I think he will be glad to response you.

73, BX3AAQ

作者: BX2ADJ 時間: 2012-9-17 21:33

QUOTE:

原帖由 bx3aaq 於 2012-9-13 05:43 PM 發表
Hi, BM2CAJ
VNWA 3E is the latest model, you don't have to change measurement direction for getting the 4 S-parameter.
Why the VNWA3 work as spectrum analyzer with frequency limitation to 100M ...

謝謝您的回答, 原來儀器本身也是很多學問的!
我後來發現 100MHz 以下, 用儲存示波器的頻譜功能也可以看,
只是沒有很方便就是了!

73 BM2CAJ

[ 本帖最後由 BM2CAJ 於 2012-9-17 21:36 編輯 ]

作者: BX2ADJ 時間: 2012-9-27 16:19

QUOTE:

原帖由 BM2CAJ 於 2012-9-17 09:33 PM 發表
謝謝您的回答, 原來儀器本身也是很多學問的!
我後來發現 100MHz 以下, 用儲存示波器的頻譜弁鄐]可以看,
只是沒有很方便就是了!
73 BM2CAJ

儀器本身真的是有很多學問,

前幾天我發現我買的這個 NWT500 掃頻儀,
很出乎意料之外的 -- 它不能做 " 頻譜分析儀 " 使用! ! !
原因還不是很懂, 總之, 接上信號源一掃, 得到一條平的直線!

要 " 頻譜分析儀 " 的話, 要買 NWT3000...
嗯, 不簡單...

73

作者: TW777 時間: 2012-10-1 01:08

請問WinNWT4 軟體有沒有中文版...英文看不懂.

作者: BX2ADJ 時間: 2012-10-2 22:39

QUOTE:

原帖由 TW777 於 2012-10-1 01:08 AM 發表
請問WinNWT4 軟體有沒有中文版...英文看不懂.

似乎沒有, 可能需要自己漢化...

作者: BX2ADJ 時間: 2012-11-11 20:57

QUOTE:

BX3AAQ OM 您好,

終於還是敗了 VNWA3E
說明書將近 300頁, 才看了一, 二十頁
請問 S11 如何調成 SWR 顯示?
找 help index 找沒有...
附圖是掃 D130 天線 100-500MHz
謝謝!

73 BM2CAJ

作者: BX2ADJ 時間: 2012-11-11 21:06

QUOTE:

BX3AAQ OM 您好,

找到調 SWR 顯示的秘密按鈕了
附圖是掃 D130 天線 100-500MHz 的 SWR
謝謝!

73 BM2CAJ

[ 本帖最後由 BM2CAJ 於 2012-11-11 22:00 編輯 ]

作者: bx3aaq 時間: 2012-11-27 02:06

Hi, BM2CAJ

Sorry to reply you with late. You seems find your answer. Please be noted, most of the characters in the measurement screen is controllable, you just double click them, scroll middle mouse wheel or click right mouse key to work on them.

In addition, you can just pull the measured S-parameter file(S1P, S2P in Touchstone format) to the screen and it will be processed. By changing the unit, you can get the transferred parameter immediately between S/Y/Z....

With its powerful software feature, I collect the S-parameter to file with HP8753E and do the post processing over it sometimes.

ps. You can use the RFSim99(freeware) to generate the S-parameter for filter, attnuator..., then pull them to VNWA for manipulation.

73,
BX3AAQ

[ 本帖最後由 bx3aaq 於 2012-11-27 18:21 編輯 ]

作者: BX2ADJ 時間: 2012-12-2 00:25

QUOTE:

原帖由 bx3aaq 於 2012-11-27 02:06 AM 發表
Hi, BM2CAJ
Sorry to reply you with late. You seems find your answer. Please be noted, most of the characters in the measurement screen is controllable, you just double click them, scroll middl ...

BX3AAQ, OM,

謝謝回覆!

請問 Y軸的刻度如何讓它顯示出來? 謝謝!

73 de BM2CAJ

作者: BX2ADJ 時間: 2012-12-3 02:20

QUOTE:

原帖由 BM2CAJ 於 2012-12-2 12:25 AM 發表
BX3AAQ, OM,
謝謝回覆!
請問 Y軸的刻度如何讓它顯示出來? 謝謝!
73 de BM2CAJ

已經找到了, 謝謝!

作者: bx3aaq 時間: 2012-12-12 18:51

Hi BM2CAJ,The VNWA program can have only two Y-axis label. Maybe you can request to DG8SAQ to have 4 Y-axis label - left inner/outer line and right inner/outer line.
73,
de bx3aaq

作者: BX2ADJ 時間: 2012-12-19 00:21

QUOTE:

原帖由 bx3aaq 於 2012-12-12 06:51 PM 發表
Hi BM2CAJ,The VNWA program can have only two Y-axis label. Maybe you can request to DG8SAQ to have 4 Y-axis label - left inner/outer line and right inner/outer line.
73, de bx3aaq

Hi BX3AAQ

謝謝您的回答!

11月中測量 KVE-60B, KC901H, NWT500, 與 VNWA 3E 的輸出信號,
想看看如果做為信號產生器的效果, 發現 VNWA 3E 輸出超低, 在 -13 至 -20dBm 左右,
其他三個儀器都比較強, 在 1 到 10dBm 左右,
而且 VNWA 3E 諧波似乎超多, 超不規則, 我很納悶!
如果 VNWA 3E 沒有中頻 (看說明書, 似乎沒有) 那為什麼會準?
不知你有沒有測過?

VNWA 3E 輸出 10MHz 約 -13dBm 頻率與示波器差 100Hz

有 30MHz -30dBm 的三次諧波, -60dBm 8.363636MHz 的怪諧波

VNWA 3E 輸出 50MHz 約 -20dBm 波形不漂亮, 示波器 Auto 抓不太到...

有 30幾MHz -60dBm 的怪諧波

VNWA 3E 輸出 100MHz 以上, 示波器已經抓不到了,
用 KC901H 看頻譜, 感覺很亂, 很多非整數倍諧波... (照片還沒整理)

不知為什麼會這樣?

謝謝!

73 de BM2CAJ

[ 本帖最後由 BM2CAJ 於 2012-12-19 00:51 編輯 ]

作者: BX2ADJ 時間: 2012-12-19 01:02

QUOTE:

繼續

VNWA 3E 輸出 100MHz 時, 有幾乎等幅 10MHz 的低頻雜波

VNWA 3E 輸出 120MHz 時, 有幾乎等幅 -30dBm 30MHz 的低頻雜波

VNWA 3E 輸出 140MHz 時, 有幾乎等幅 -30dBm 50MHz 的低頻雜波

VNWA 3E 輸出 200MHz 時, 有幾乎等幅 110MHz 的低頻雜波

感覺奇怪? ? ?

現在再看, 都差 90MHz 耶! 不知是如何移頻的結果?

73 BM2CAJ

[ 本帖最後由 BM2CAJ 於 2012-12-19 01:05 編輯 ]

作者: bx3aaq 時間: 2012-12-21 02:35

Dear BM2CAJ,
Some pictures included and explained

1. VNWA3 Specsheet

I highlight the information about signal generator. Its level is -17dBm(maximum) and adjustable to lower value. The other key information - No harmonic filtering, and I will explain below.

2. VNWA3 architecture

It use two DDS which refer to same crystal oscillator, ie the two DDS's output frequency is phase align together and that is the key point for keep the phase information in VNA. Two of the DDS can be named as RF DDS(Reference) and LO DDS. The RF DDS signal will deliver to DUT(Device Under Test), some signal will be reflected(Reference) and some signal will pass through the DUT(Thru). Now, there are three signal - Reference, Reflect and Thru. All of them will mixing with the LO DDS signal(the mixer is SA612, most used by the ham hobby) to audio band, then the audio band signals will transfer to TLV2462 OPAMP for amplifying and filtering(Sallen-Key BPF). In the last, an audio codec(PCM2900B) do the A-D conversion, and deliver them to the computer through USB interface(TUSB2036). The PCM2900 have only two analog input(L/R channel), so it need to mux the Reflect/Thru signal with a selective switch. If you buy the latest model, a second codec is installed, VNWA3 can get the Reflect/Thru signal same time, ie. the S11/S21 measurement is done same time.

3. DDS output spectrum

The DDS output stage is a DAC to transfer the digital data to analog waveform. The pulsed data will get a sinc frequency response over DAC output.
If we want to get a clean and flat spectrum over DDS output, the reconstruction filter should be installed for correcting the sinc distortion and removing the aliases.
Does these aliases useless ? not necessary. VNWA3 borrow them to extend its operation frequency range.

4. VNWA3 output spectrum

That is the most trick part of VNWA3, it use the idea of "Aliases mixing" to extend the VNWA3's operation range to 1.3GHz. How can you expect the DDS ICs to work over GHz band several years ago! In above picture, the reference clock is 300MHz(F_ref). In an un-filtered DDS output, you can see the fundamental signal in red color(F_fund=80MHz) and the aliases signal over N*F_ref +/- F_fund in blue color(300 +/- 80=220/380MHz, 600 +/- 80=520/680MHz...). That is why you see many strange signal over VNWA3's TX OUT as a signal generator. Does it impact to VNWA3's measurement accuracy ? No. After mixer downconversion, the TLV2462 BPF and additional digital filter over computer will select the target alias signal to process.

Now, we know these aliases signal is normal in VNWA3, but I can't calculate exactly how these frequency components you got. Maybe you can paste your instrument setting as follow, and I have more clue to count for them.

ps.
About the DDS(Direct Digital Synthesizer), it is much used in the modern transceiver. If you check the service manual of FT-897D, the AD9850 and AD9835 is used as the local oscillator and side-band selection. In the ICOM IC-7000, you can also find the AD9951 and AD9833 work as 1st and 3rd local oscillator.

The DDS's output frequency will limit to 1/2 reference clock in theory(1/3 in practical). For example, a reference clock 400MHz to DDS, its maximum output frequency is 200MHz. The primary clock is generated with crystal oscillator most of the time. The crystal oscillator seldom to operate higher than 100MHz. So the DDS will have xosc multiplier(AD9859 used in VNWA3 with multiplier ratio from 4x to 20x). A 37MHz xosc will generate 37*20=740MHz reference clock.

73,
de bx3aaq

[ 本帖最後由 bx3aaq 於 2012-12-21 02:42 編輯 ]

作者: BX2ADJ 時間: 2012-12-22 23:35

QUOTE:

原帖由 bx3aaq 於 2012-12-21 02:35 AM 發表
Dear BM2CAJ,
Some pictures included and explained
1. VNWA3 Specsheet
I highlight the information about signal generator. Its level is -17dBm(maximum) and adju ...

DR BX3AAQ,

感謝精彩詳細的回覆,

我想, 如果輸入接的 SA612 乘法器線性度佳, 混調變不多的話, 不用中頻應該可以, 這種狀況反而輸出位準不太高才比較好.
我的 setup 條件沒改, 是 auto

今天用 VNWA 3E 輸出 200MHz , 用 KC901H 再量頻譜

1MHz ~ 3GHz 頻譜, 看到 110MHz 與 200MHz 的 3, 5, 7, 9, 11, 等奇數倍頻
與原理推算一致

但 110MHz 與 200MHz 各自還有 106MHz 與 196MHz 的頻峰
懶得再去追根究底了...

TU 73 de BM2CAJ

[ 本帖最後由 BM2CAJ 於 2012-12-22 23:43 編輯 ]

作者: BX2ADJ 時間: 2013-1-24 23:36

QUOTE:

原帖由 BM2CAJ 於 2012-12-22 11:35 PM 發表
DR BX3AAQ,
感謝精彩詳細的回覆,

我想, 如果輸入接的 SA612 乘法器線性度佳, 混調變不多的話, 不用中頻應該可以, 這種狀況反而輸出位準不太高才比較好.
我的 setup 條件沒改, 是 auto
http://i.img ...

S21 動態區間 (Dynamic Range) KC901H  VNWA 3E  NWT500 大評比

之前測雙工器, 三個儀器測出的曲線不大一樣,
這次用 " 固定衰減器 " 組合成 -20dB ~ -106dB 測三個儀器來個 PK 評比一下:

衰減器是 MACOM DC - 4GHz 1-2W  -40dB 二個, -20dB, 與 -6dB (剛好沒有 -10dB)
組合成 -20dB, -40dB, -46dB, -60dB, -66dB, -80dB, -100dB, 與 -106dB 測三個儀器的 S21曲線

測量頻率:
NWT500 50KHz - 505MHz
VNWA 3E  1KHz - 505MHz
KC901H 100KHz - 505MHz

NWT500

NWT500 50KHz - 505MHz

看來 NWT500 在 -60dB 以下就不大準了!
不過以它的價格而言, 我認為已算是性價比相當好的儀器了!

73

[ 本帖最後由 BM2CAJ 於 2013-1-25 00:29 編輯 ]

作者: BX2ADJ 時間: 2013-1-25 00:07

QUOTE:

原帖由 BM2CAJ 於 2013-1-24 11:36 PM 發表
S21 動態區間 (Dynamic Range) KC901H VNWA 3E NWT500 大評比

之前測雙工器, 三個儀器測出的曲線不大一樣,
這次用 " 固定衰減器 " 組合成 -20dB ~ -106dB 測三個儀器來個 PK 評比一下:
...

VNWA 3E

已做好校正 (Full Calibration, Master Calibration Activated)

VNWA 3E 1KHz - 505MHz

另我訝異的是 VNWA 3E 在 -60dB 以下也是不大準的!
而且在 300MHz 有一個不連續切換
大致上, 在 UHF 約有 -3dB 左右偏低
到了 -80dB 以下原則上是不行的! ! !
上圖是圖片軟體剪接, 所以 -60dB -66dB 顏色較淡, 另看下圖:

-60dB -66dB 不怎麼好

-80db -100dB 很差

很訝異...

73

[ 本帖最後由 BM2CAJ 於 2013-1-25 00:16 編輯 ]

作者: BX2ADJ 時間: 2013-1-25 00:27

QUOTE:

KC901H 100KHz - 505MHz

0dB

-20dB

-40dB

-60dB

待續

作者: BX2ADJ 時間: 2013-1-25 01:08

QUOTE:

-80dB

-100dB

-106dB

三個儀器測出的曲線與數據看來,

KC901H 大獲全勝!

無論是 0dB 至 -106dB 動態區間的線性度,
或是 100KHz 至 505MHz 頻率區間的波動, 都是最好的!

以上是測試結果

73 de BM2CAJ

[ 本帖最後由 BM2CAJ 於 2013-1-25 01:11 編輯 ]

作者: bx3aaq 時間: 2013-1-25 01:33

Dear BM2CAJ,
OK, I will take time to check the VNWA3 in my side. It using the alias mixing for working to 1.3GHz with some performance degrade in higher band. In your testing frequency range, I am also wonder why it not work so good.
If I can't find good explanation to the result after doing the experiment, I will pass my doubt to DG8SAQ and see his feedback.
ps. For the attenuation test, I will do the same experiment with HP8753E in my side.

73,
de bx3aaq

作者: BX2ADJ 時間: 2013-1-25 03:22

QUOTE:

原帖由 bx3aaq 於 2013-1-25 01:33 AM 發表
Dear BM2CAJ,
OK, I will take time to check the VNWA3 in my side. It using the alias mixing for working to 1.3GHz with some performance degrade in higher band. In your testing frequency range, I ...

Dear BX3AAQ

Thank you very much for the comment.
But don't worry. I will not regret to buy VNWA 3E. It is still a very good instrument for me.
It has lower power output level -27dBm. I guess this will be much better for pre-amp measurement,
which will be the next step for me. I played these instruments a lot. For the next step,
I hope to find time to make and test pre-amps.

Thank you very much!

73 de BM2CAJ

作者: BX2ADJ 時間: 2013-1-26 19:39

QUOTE:

左岸 BG8AAS 給了一些評論, 有興趣的 OM 可以看看:

http://www.hellocq.net/forum/read.php?tid=309797

8樓 ...

73

作者: bx3aaq 時間: 2013-1-27 18:55

Dear BM2CAJ,
The HP8753E measurement for attenuator are shown(import and display with VNWA software)
1. Attenuator in 0/-20/-40/-60/-80/-110 dB

2. Attenuator in 0/-20/-40/-60/-80/-110 dB with data smooth average(same dataset as above)

It reflects some some information here
1. In the lower attenuation test, the measurement difference is below about 1dB
2. In the higher attenuation test(attenuator set to 110db), the measurement difference is quite large and the signal is fluctuated
3. With smooth average the measured data, the measurement difference is narrow down, but it also lost the detail of the result.
I am quite impressed the KC901H to get the -120dB attenuator measurement. The isolation for cable, connector and PCB board will not reach that level easily. Maybe it can also do good as a SDR frontend!!
73,
de bx3aaq

[ 本帖最後由 bx3aaq 於 2013-1-27 19:02 編輯 ]

作者: BX2ADJ 時間: 2013-1-28 22:56

QUOTE:

原帖由 bx3aaq 於 2013-1-27 06:55 PM 發表
Dear BM2CAJ,
The HP8753E measurement for attenuator are shown(import and display with VNWA software)
1. Attenuator in 0/-20/-40/-60/-80/-110 dB
2. Attenuat ...

Dear BX3AAQ,

感謝您的分享, 能見到專業儀器的測試, 真是高興! 漂亮極了!
比較之後, 看來 KC901H 的 S21 滿不錯的!

但我發現用 50 歐姆假負載測 S11
KC901H 與 VNWA 3E 的曲線都沒有很完美, 或許電橋不容易做完美?
一直猶豫要不要 po 出來...

如果你的時間許可, 再請你也測一下, 謝謝!

73,
de BM2CAJ

[ 本帖最後由 BM2CAJ 於 2013-1-29 01:21 編輯 ]

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