前二個章節我們已經學會了Non-Signalling mode(非信令模式)的BR、EDR測試方法,接下來我們就來看看BLE(Bluetooth Low Energy)的測試方法。
測試架設圖如下:
底下舉例讓QCC51XX待測物打出BLE 1Mbps封包而LitePoint儀器解析藍芽封包做BLE TX測試的步驟:
A. 透過USB debug port打開Bluetest3。
B. 選擇Disable application並點擊execute(for AAF earbuds application only)。
C. BLE的TX測試相對於BR/EDR來說簡單的多了,不需要對應表格來看要打什麼樣的packet,也不需要在Bluetest3輸入參數決定BLE power打多大(BLE power在CSkey已經決定)。只需要設定輸出Channel、Length、Bit pattern以及PHY即可。下圖舉例為QCC5124於channel 39(2480MHz)打出最長的packet length(255)的PRBS9(Bit pattern 0) BLE 1Mbps payload,然後點擊Execute就可以讓QCC5124開始發射BLE TX信號。
Note. Bit pattern = 0 to 7. The packet payload bit pattern, where:
(1) 0 = Pseudo-random bit sequence 9 for
TP/TRM-LE/CA/BV-01-C [Output power]
TP/TRM-LE/CA/BV-03-C [In-band emissions, uncoded data at 1 Ms/s]
TP/TRM-LE/CA/BV-08-C [In-band emissions at 2 Ms/s]
(2) 1 = Pattern of alternating bits "11110000" for
TP/TRM-LE/CA/BV-05-C [Modulation Characteristics, uncoded data at 1 Ms/s]
TP/TRM-LE/CA/BV-10-C [Modulation Characteristics at 2 Ms/s]
(3) 2 = Pattern of alternating bits 10101010
TP/TRM-LE/CA/BV-06-C [Carrier frequency offset and drift, uncoded data at 1 Ms/s]
TP/TRM-LE/CA/BV-12-C [Carrier frequency offset and drift at 2 Ms/s]
(4) 3 = Pseudo-random bit sequence 15
(5) 4 = Pattern of all 1 bits
(6) 5 = Pattern of all 0 bits
(7) 6 = Pattern of alternating bits 00001111
(8) 7 = Pattern of alternating bits 01010101
D. 在IQxel web版”Tools”選擇”Port Routing”,並將Port RF1A設定為”VSA”後關閉該對話視窗(如下圖) 。
E.“Technology”選擇”Bluetooth”;Offset設定RF cable loss,我的環境設定為1;Count設定計數10次。Result可將你想量測的項目拖拉至右邊格子內,由於此次是測試BLE因此TXQuality、ACP、20dB Bandwidth、LE Avg. Freq.(fn) vs. Time以及LE DeltaF2Max vs. Time…等都是可列入測試的項目。
F.“VSASettings” Frequency設定為跟Bluetest3 channel 39一樣的2480MHz;Reference Level設為9dBm;Sampling Rate設為80MHz;Capture Length設定為100ms後點擊藍色或綠色三角形方塊即可開始解析RF量測數據(藍色三角形方塊是run一次測試;綠色三角形方塊是連續run測試)。這時候在TX Quality的畫面可以看到解析出來的Packet Data Rate為LE。
G. 因應不同的測試項目需要打出不同的payload,因此Bluetest3需要做Bit pattern和PHY的切換(如上述第2點描述),比如Bit pattern設為1是打出"11110000"的payload for底下2個LE的RF測項。
TP/TRM-LE/CA/BV-05-C [Modulation Characteristics, uncoded data at 1 Ms/s]
TP/TRM-LE/CA/BV-10-C [Modulation Characteristics at 2 Ms/s]
而Bit pattern設為2則是打出"10101010"的payload for底下2個LE的RF測項。
TP/TRM-LE/CA/BV-06-C [Carrier frequency offset and drift, uncoded data at 1 Ms/s]
TP/TRM-LE/CA/BV-12-C [Carrier frequency offset and drift at 2 Ms/s]
PHY設定為1或2則是做LE 1Mbps或LE 2Mbps的切換。
接著舉例讓LitePoint儀器打出BLE 1Mbps封包而QCC5124待測物解析藍芽封包做BLE 1Mbps RX PER(bit error rate)測試的步驟:
H. BLE RX的測試也跟BR/EDR不太一樣,BLE RX的測試要先在Bluetest3選擇”BLE TEST RX”然後設定接收channel 39(2480MHz)以及設定PHY為1(接收BLE 1Mbps封包),其他欄位維持default值即可,然後點擊”Execute”。
I.“Tools”選擇”Port Routing”,並將Port RF1A設定為”VSG”後關閉該對話視窗(如下圖)。
J. VSG1左邊畫面”Waveforms”裡的”Load”點擊一下後右邊會跳出一對話視窗,選擇”bt_le_prbs9_Fs80M.iqvsg”的waveform(如下圖)後點擊Select。
K. 左上畫面”VSG1 Settings” Frequency選擇為欲測試的頻率,本範例測試2480MHz,因此將Frequency設定為2480MHz;Power level設定為-70dBm for BLE receiver sensitivity的測試規範;Sampling Rate設定為80MHz(如下圖)。接著”Count”左邊的框框勾選後再輸入”1500” (follow SIG test spec),最後”Waveforms”裡的”Play”點擊一下,Litepoint儀器即開始發射1500筆BLE 1Mbps PRBS9封包出去。等待約莫不到2秒的時間”Play”下方的”1500”數字即會歸零表示1500筆的BLE封包已經發射完成。
L. Bluetest3選擇”BLE TEST END”並點擊”Execute” ,在Bluetest3下方對話框會自動計算出接收到的封包數,此範例並非在shielding box內測試因此received packet count為1484。
M. 套入底下PER%計算公式:
PER% = 100 * (1 – (Packets Received / Packets Sent ))
PER% = 100* (1-(1484/1500))=1.06%
BLE receiver sensitivity spec是30.8%,所以上面範例的BLE sensitivity測試是pass的。
Note. 不同的BLE RX測項需要在LitePoint儀器變換不同的power level及不同的waveform。
比如TP/RCV-LE/CA/BV-06-C [Maximum input signal level, uncoded data at 1 Ms/s]儀器載入的是BLE 1Mbps的waveform, power level為-10dBm;
而TP/RCV-LE/CA/BV-12-C [Maximum input signal level at 2 Ms/s] 儀器載入的是BLE 2Mbps的waveform, power level同樣為-10dBm。
評論
Charles Yu
2021年7月8日