Resolutions and Analysis:
Coaxial connector manufacturers Huber+Suhner and Radiall were the first to begin research & development on the Quick-lock connectors. In the past few years, they have successively released QMA (Quick-Lock SMA) and QN (Quick-Lock N)connectors, and together with AmphenolRF and Rosenberger established the QLF(Quick Lock Formula) alliance so as to share technologies, unify quick lock connector interface standards, and profit from joint marketing. Presently, QLF’s versions of QMA and QN are the most widely used on the market.
In the following analysis and comparison of these QLF connector designs, it is shown how new design ideas were reached.
Below is the design for QLF’s version of QMA (Figure 2).
Testing shows this design to be fundamentally sound, as it can approach SMA’s relatively high electrical performance. However, small problems still exist.
The spring-lock in the QMA connector’s design requires the use of beryllium copper. This mineral is in itself expensive, add to which the difficulty there is in machine processing and its need for thermal processing as well as environmental protection treatment and the overall cost becomes very high.
When the QMA male and female are mated, the effective contact length of the inner conductor is short, being only 1.60 mm, whereas the effective contact length of the original SMA is 2.30 mm (See figure 1). After several uses, this may result in the reduced contact reliability of the inner conductor.
These there areas are the main respects in which QLF’s version of QMA can be improved upon, and in fact have been in a new version of QMA (hereafter referred to as Anoison QMA, See figure 3), which has been on the market for almost two years, and successfully resolves all these problems.
Anoison QMA’s waterproof seal is cleverly designed so that when under pressure from the outer bevel of the female, an O-ring rests in the groove of the male outer conductor creating an excellent seal and anti-shock effect.
In the Anoison QMA design, the S/S spring-lock in the plug, costs only 1/10 of the spring-lock made from beryllium copper in QLF's QMA, and consists of a ring-like locking sheet with inner and outer teeth. A trapezoid cross section which has an upslope, flat top and down slope is located on the surface of the socket connector’s outer conductor. Thus, when connecting,the inner teeth reach their maximum flexural deformation while rising along the upslope to the flat top, then while moving along the flat top the deformed inner teeth are gradually restored to their original state in the tangential direction of the down slope before finally stopping at the down slope, or at the juncture of the down slope and a flat valley. The external faces of the inner teeth thrust the down slope in its original direction,creating close contact between the contact surfaces with zero clearance and a relatively strong axial force (The axial force greatly influences the performance of passive inter-modulation).In addition, the adjacent inner teeth of the ring-like locking sheet have different lengths,which enable them to stop on different circumferences of the down slope when locking. The angle between the longer teeth and the down slope is ≥90, while that between the shorter teeth and the down slope is ≤90 (See Figure 5). This design creates very good retention force and has excellent anti-shock performance, fully meeting all requirements for military use. In addition, the effective mating cycles of Anoison QMA is over 200 times.
In the interest of improved reliability, the effective contact length of the original SMA inner conductor, 2.30 mm, ought to be maintained, and is matched in the Anoison QMA design.
Two further notes:
The Anoison QMA plug is completely backward compatible with the QLF's QMA jack. In addition, for the purpose of saving space and material, a mini version of QMA (hereafter referred to as Mini-QMA, see figure 6) has been designed; which combines comparable performance with reduced volume.
The following are three versions of QN that were released successively by QLF founder Huber+Suhner beginning in 2002. 1) 2002 version (See Figure 8).
QLF’s 2002 version QN was the first to successfully convert the N type connector’s original threaded connection to a snap-fastening, self-locking one Advantages:
- Improved mating and de-mating efficiency as a result of a snap lock mechanism that requires no tools The dimensions of the conductor were decreased, reducing its weight between 20-40%, in addition to requiring 20-50% less copper to manufacture. The increased installation density of the connector saves installation space. In the mated position the connector allows for 360 degree rotation. Requires little or no training to mate and de-mate the connector.
- Extra parts require a high degree of processing accuracy because the clearance between electrical contact surfaces is completely controlled by the processing accuracy. If there is clearance between the contact surfaces there will be no contact force which will affect the VSWR and passive inter-modulation. By not adopting the basic parameters of the N type connector, QN had to be completely re-designed, re-inspected and verified resulting in a great deal of work.
2) 2003 version (See Figure 9)
The 2003 version of QN made improvements based on the 2002 design. Advantages:
- A wave spring washer was added to the contact interface of the connector in order to increase the axial pressure and eliminate the clearance between contact surfaces with its elasticity. Reduced contact resistance, which helped to improve the passive inter-modulation.
- By placing a wave spring washer on the contact surface of the connector the problem of clearance was solved, but there is contact at only a few points on the circle’s surface and the impedances around them are not well matched. This in turn can cause reflection of the electromagnetic wave at these points. As a result, this connector works well in DC-1.5 GHz and can also work in 1.5-3.0 GHz.However,if it is used in 3-6 GHz, the VSWR will be high, and will be still higher in 6-11 GHz.
3) 2004 version (see Figure 10).
In the 2004 version, further improvements were made based on the 2003 design.
- The wave spring washer on the contact surface of the connector was replaced by a radial disk spring, which increases axial pressure while reducing contact resistance and improving contact stability. By using a radial disk spring, the contact between the spring and the contact surface is not just at a few points but a whole circle.
- This further improves the PIM while reducing the VSWR and insertion loss
- Since the contact surface of the outer conductor is tapered to a point, a relatively high axial pressure is generated under the influence of the radial disk spring, improving contact resistance. However, as the space formed by the sharp end of the outer conductor and the spring is an irregular shape, by using the transmission theory (see figure 11) it is shown that the characteristic impedance in this part is not continuous and may cause a rather large reflection, especially when transmitting high-frequency electromagnetic waves. The VSWR is quite good in DC-1.5GHz and acceptable in the 1.5-3GHz range. However, it may cause trouble when used at 3-6GHz, and still more at 6-11GHz.
- In this newest version of the QN conductor, further improvements can still be made in the following areas: The three classic RF coaxial connectors, SMA, N, and APC-7, are all able to achieve high bandwidth and low VSWR primarily as a result of the zero clearance in contact interface, which allows for continuous impedance and almost no reflection between their contact surfaces.
However, the QLF’s QN design’s use of a spring contact will in all likelihood result in discontinuous impedance. The Quick-Lock-N type connector should base its structure on the rigid contact design of the original N type connector, which guarantees continuous impedance between contact surfaces and enables it to maintain the N type’s electrical performance: DC-11GHz VSWR<1.25, with the precision type Quick-Lock-N able to reach DC-18GHz VSWR<1.08. The newly designed Anoison HPQN(High Performance Quick-lock N)connector adheres to these principles by adopting a spring-lock made of stainless steel similar to that used in the QMA, which allows for rigid contact between the contact surfaces and ensures continuous impedance. That is to say HPQN maintains the performance indexes of the original N type connector, while requiring only 80% of the material necessary to manufacture the QLF’s QN design.(see figure 12)
More details please view ANOISON ELECTRONICS.