Basic theory and concept for reciprocal mixing and MRS
for HF receivers and transceivers
My friend of Ham radio operator said receiving desired weak signal readability ranking are
DS_SDR > TS-590 > FTdx5000 at 20m band,
however FTdx5000 can't detect and read to the same desired readable weak signal (DS_SDR is direct
sampling SDR). Those are DS_SDR heard 100% desired readable weak signal,
TS-590 detects but heard not complete reading about the same desired readable
weak signal and FTdx5000 heard nothing about the same desired readable weak
Then I checked ARRL RMDR (Reciprocal Mixing Dynamic Range) and result are
-65dBc >- 94dBc >-104dBc (under -100dBc is better), thus almost reverse results and contradict the fact of above readability ranking.
On the other hand, ARRL wrote "In many cases, reciprocal mixing dynamic range (RMDR) is the primary limiting factor of a receiver's performance", am I hearing
this right? (References 1)
Unfortunately I can't understand what RMDR, thus can't related to clock oscillator
(CO) phase noise and local oscillator (LO) phase noise, and also actual reciprocal
mixing test. (References 2)
Reciprocal Mixing is absolutely related to CO and LO phase noise, unfortunately
RMDR can't have those phase noise and can't discus about those phase noise, thus
RMDR can't related to reciprocal mixing and it effects.
As above problems then I am thinking about reciprocal mixing and effects under the condition of typical DX pileup situation and typical low band situation.
1. Primary key receiver performance under the condition of typical DX pileup
situation and typical low band situation
Primary key receiver performance under the condition of typical DX pileup
situation and typical low band situation concerning Local Oscillator (LO) phase noise or Clock Oscillator (CO) phase noise and reciprocal mixing effects.
1-1. Reciprocal mixing effects under the condition of typical DX pileup situation
LO phase noise or CO phase noise and reciprocal mixing effects under the
condition of typical DX pileup situation refer to Fig.1 and this condition exclude
nearby signals excessive phase noise.
1) Nowadays, typical DX pileup situation is much more crowded under 2kHz
narrow separation and station to station, thus increases the noise floor for phase
noise in LO or CO according to reciprocal mixing effects. Therefore desired weak
signal buried in increased noise floor.
2) Phase noise level for LO and CO requires under -125dBc/Hz 1kHz offset from
carrier and under -135dBc/Hz 10kHz offset from carrier, thus the S1 signal level
is -121dBm and refer to chapter 1-5 item 3)．
3) Above conditions precedent is more than 95dB of 2kHz spacing two tone third
order IMD dynamic range (TT_TO_IMD_DR).
4) Synchronize to frequency standard
Prohibited matter as follows:
① Some SDR includes option GPSDO in spite of degrading CO phase noise,
therefore don't use option GPSDO.
② Don't use general kind of GPSDO due to degrading phase noise.
Following items for selection and GPSDO conditions
① Improved GPSDO includes VC_OCXO and PLL have more than 100 seconds
loop time constant, thus don't occur degrading phase noise.
② General kind of GPSDO and connect through Microsemi (Symmetricom)
ultra clean phased lock oscillator 4145B or 4145C, therefore 10MHz and 5MHz
output have low phase noise, however input frequency 5MHz only and
requires frequency divider for GPSDO output 10MHz.
Following equipment for typical laboratory use frequency standard and
appropriate phase noise for DS_SDR and related equipment, thus distributing
fine 10MHz frequency standard.
① 5071A (HP, Agilent, Symmetricom now Microsemi)
② Microsemi CsIII Model 4310B
If requires ultra low phase noise then refer to above 4145B or 4145C.
1-2. Reciprocal mixing effects under the typical low band situation and ambient
LO phase noise or CO phase noise, reciprocal mixing effects and ambient noise
under the typical low band situation refer to Fig.2.
1)Typical low band situation is much more ambient noise, thus increases the noise
floor for phase noise in LO or CO according to reciprocal mixing effects.
Therefore desired weak signal buried in increased noise floor.
2) Fig.2 shows desired weak signal 1 and 2 buried in assumed receiver noise floor
for degraded phase noise local oscillator and ambient noise.
3) I assumed ambient noise level nearly equal to 1kHz offset reciprocal mixing
then noise floor adding about +6dB from ambient noise level.
4) Those assumed Noise floor depends on 1kHz offset phase noise in LO or CO,
however under investigation for ambient noise relation of 0.1kHz offset and 1kHz
offset phase noise in LO or CO.
1-3. Reciprocal mixing
1) Condition of typical DX pileup situation's equivalently strong clean interferer
signal increases noise level in IF bandwidth for phase noise in LO or CO
according to reciprocal mixing effects, thus desired weak signal buried in this
2) Reciprocal mixing process refer to Fig.3.
3) Requires important matters for reciprocal mixing that details of desired weak
signal level under the condition of typical DX pileup situation and equivalently
strong clean (Ultra Low Phase Noise Level) interferer signal and signal level and
also LO phase noise level on receiving frequency or CO phase noise level on clock
1-4. Reciprocal mixing and equivalently interferer signal, desired weak signal
Reciprocal mixing under the condition of equivalently strong clean (Ultra Low
Phase Noise Level) interferer signal and desired weak signal as follows:
1) Equivalently strong clean interferer signal's level of phase noise requires under
-140dBc/Hz 0.1kHz offset from carrier, under -150dBc/Hz 1kHz offset from
carrier and -160dBc/Hz 10kHz offset from carrier at 14MHz, thus existing rigs
(refer to table 1) example phase noise level is -140dBc/Hz 1kHz offset from
carrier and -150dBc/Hz 10kHz offset from carrier at 14MHz.
2) Recommend equivalently strong clean interferer signal level is 0dBm
(S9+73dB). If saturation or clip occurs then this level goes down to -5dBm
(S9+68dB) or -10dBm (S9+63dB). And this signal requires 1kHz offset from
desired weak signal.
3) Equivalently strong clean interferer signal ingenerate Ultra Low Phase Noise
analogue type SG. This kind of SG supplier are Keysight and R&S, those
example phase noise specification etc as follows:
① Keysight E8663D option HY2 and 1E1
② R&S SMA100B SMAB-B711N option
③ Phase noise level for 0.1kHz offset from carrier at 10MHz
Specification value: -140dBc/Hz
Typical value: -152dBc/Hz
④ Phase noise level for 1kHz offset from carrier at 10MHz:
Specification value: -155dBc/Hz
Typical value: -162dBc/Hz
⑤ Phase noise level for 10kHz offset from carrier at 10MHz
Specification value: -155dBc/Hz
Typical value: -163dBc/Hz
4) Desired weak signal and signal level ingenerate general purpose SG or
additional above ultra low phase noise analogue type SG.
This SG requires phase lock to above ultra low phase noise analogue type SG's
external reference output 10MHz.
5) Synchronize to distributed external 10MHz frequency standard requirement
refer to chapter 1-1 item 4).
1-5. MRS (minimum readable signal level) and receiver configuration
1) Receiver's sensitivity degraded by reciprocal mixing (MRS) with local oscillator
(LO) or clock oscillator (CO) phase noise and receiver configuration as follows:
① Direct Sampling SDR
② Direct Conversion
③ Single Conversion (One mixer)
④ Double Conversion (Two mixers)
⑤ Triple Conversion (Three mixers)
Assumed factor is RF mixing stage and degraded 3dB each mixer.
1-6. Assumed approximation equation for MRS
1) Reciprocal mixing effects for the required LO phase noise and equation
Emmanuel Ngompe described reciprocal mixing effects (reference 8) for the
required LO phase noise and may be estimated using the following equation:
L(fc) [dBc/Hz] = Sdes －Sbl(fc) －C/Ireq －10log(BW)
L(fc) = phase noise in dBc/Hz at fc away from the carrier
Sbl(fc) = magnitude of the blocker (interferer signal) in dBm (or dBV)
C/Ireq = minimum magnitude of the required carrier-to-interference ratio at the baseband
processor input in dB
Sdes = desired signal level in dBm (or dBV)
BW = receiver noise bandwidth
2) Required LO phase noise equation transformed to estimated and desired weak
signal level as follows:
Sdes [dBm] = L(fc) + Sbl(fc) + C/Ireq + 10log(BW)
3) Reciprocal mixing effects for the desired weak signal level (MRS) equation
Reciprocal mixing effects for the desired weak signal level (MRS) in dBm may be
estimated using the following assumed and approximately modified for HF
receivers and transceivers equation.
MRS [dBm]≒(1kHz offset phase noise in LO or CO) + 0 + 6 + 10log BW +α
① Interferer signal level: 0dBm
② SNR: 6dB
③ BW: kHz (Basic condition: 0.5kHz)
④ Mode: CW
⑤ α: depends on receiver configuration [dB]
Direct Sampling SDR : 0
Direct conversion ：0
Single conversion : 3
Double conversion ：6
Triple conversion : 9
1-7. Graph 1 for compare CO phase noise and MRS
1) Graph 1 for compare CO phase noise data CVHD-950 VCXO and calculated
MRS values according to above equation thus refer to Table 1.
2) MRS values according to Table 1 and ranking as followings:
ANAN > FLEX > DS_SDR > DBC > P_LO_ DBC > TPC
ANAN: Apache Labs Direct Sampling SDR
FLEX: FlexRadio Systems Direct Sampling SDR
DS_SDR: Expart MB1 Direct Sampling SDR
DBC: Typical Double Conversion
P_LO_DBC: Double Conversion with poor phase noise LO
TPC: Typical Triple Conversion
Assumed MRS values depends on above equation and each phase noise data
comes from DDS application notes, catalogs and makers answer.
1-8. Comparison Table for HF receivers and transceivers
Comparison Table for HF receivers and transceivers includes calculated MRS
values according to above equation and other data comes from QST review etc,
refer to Table 1.
Primary key receiver performance under the condition of typical DX pileup
situation and the typical low band situation concerning local oscillator (LO) phase
noise or clock oscillator (CO) phase noise and reciprocal mixing effects, those
results are MRS (minimum readable signal level).
We requires reciprocal mixing test for MRS and useless any RMDR.
1. Bob Allison, WB1GCM described "Reciprocal Mixing Testing: What is" to
published in QST April 2013 page 55.
2. ARRL described item 5.7A reciprocal mixing in chapter V. receiver test to
published in ARRL Laboratory's "Test Procedures Manual " Revision N. Dec. 31
2014 pages between 50 page and 52 page.
3. Tadeusz Raczek SP7HT described LO phase noise and reciprocal mixing under
the condition of typical DX pileup situation to published in QEX Sep/Oct 2002
4. John Eisenberg K6YP described Reciprocal Mixing to published in PPT "What
makes a receiver grate? " pages between 18 page and 20 page.
5. James R. Fisk W1DTY described MUS (minimum usable sensitivity) to published
in a Ham Radio Magazine Oct 1975.
6. Nigel Clement Davies described reciprocal mixing to published in Digital Radio
and Its Application in the HF (2-30 MHz) Band, May 2004, page 87 for 5.3 HF
Receiver Performance Requirements and page 93 for reciprocal mixing.
7. Tired, Tobias described reciprocal mixing to published in High Performance LNAs
and Mixers for Direct Conversion Receivers in BiCMOS and CMOS Technologies.
2012-03-04 page 24.
8. Emmanuel Ngompe described reciprocal mixing effects to published in APPLIED
MICROWAVE & WIRELESS Jan.1999 pages between 54 page and 58 page
"Computing the LO Phase Noise Requirements in a GSM Receiver".
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