EUROQUARTZ 1 MADE-TO-ORDER CRYSTAL FILTERS FILTERS Tel: +44(0)1460 230000 Fax: +44(0)1460 230001 Email: [email protected] Web: www.euroquartz.co.uk TECHNICAL TERMS NOMINAL FREQUENCY GUARANTEED ATTENUATION The Nominal Frequency of a filter is the centre frequency (F ) or carrier frequency (F ) in SSB filters. Attenuation guaranteed (dB) at the specified frequency range. 0 c SPURIOUS PASS BANDWIDTH Spurious refers to the attenuation (dB) caused by extraordinary response in the stopband. Stated in kHz, the Pass Bandwidth refers to the frequency bands where attenuation is equal to or lower than the specified attenuation (in dB) GROUP DELAY DISTORTION The difference between maximum and minimum group delay with the passband is referred to as Group Delay Distortion. STOP BANDWIDTH In kHz, the Stop Bandwidth is where attenuations are equal to or larger than the specified figures (dB) TERMINATING IMPEDANCE Refers to either of the impedances presented to the filter by the source or by the load and describes the resistive portion (R ) and the parallel capacitive portion (C ) including stray capacitance. INSERTION LOSS t Insertion Loss is the loss (dB) defined by the logarithmic ratio of power transmitted to load before and after insertion of the filter. t RIPPLE Attenuation (dB) Attenuation Curve Ripple is the difference (dB) between maximum and minimum attenuation in the passband. Stop Band Stop Band Crystal Filter Parameters ' Attenuation Attenuation Group Delay µs Group Delay Distortion Group Delay Curve Pass Band Ripple Specified Attenuation fo Nominal Frequency Information Required for Ordering Custom Filters Type of Filter Holder Type Nominal Frequency MHz Number of Poles Passband Characteristics Stopband Characteristics Ripple Insertion Loss Guaranteed Attenuation Terminating Impedance dB dB dB max. dB max. dB Ohms// ±kHz ±kHz ±kHz (fo) pF °C, to °C Test Fixture (Test Circuit) Operating Temp. Range Relative Attenuation 0dB Insertion Loss EUROQUARTZ 2 MADE-TO-ORDER CRYSTAL FILTERS FILTERS Tel: +44(0)1460 230000 Fax: +44(0)1460 230001 Email: [email protected] Web: www.euroquartz.co.uk FILTER DESIGN CONSIDERATIONS BAND PASS FILTERS BAND PASS CRYSTAL FILTERS NARROW BAND PASS CRYSTAL FILTERS Design considerations Narrow band pass crystal filters are designed to pass a narrow frequency band and reject all other frequencies. The maximum band width using fundamental mode crystals is 0.3% of the centre frequency and is 0.03% when using third overtones. Specifying the Passband 1.0MHz to 100.0MHz Operating Temperatures: 0°C to 50°C, -10° to 60°C, -20°C to 70°C, -40°C to 90°C, INTERMEDIATE BAND PASS CRYSTAL FILTERS 1.0MHz to 100.0MHz The maximum bandwidth of this range of crystal filters is 2.0% of the centre frequency. To obtain an optimum design many factors require consideration. All specification variations are interdependent and computer simulation is the only satisfactory means of realizing a design. Euroquartz Filters possess this facility and can design a filter to your requirement if the general specification is known. It is necessary to specify the filter centre frequency in MHz and the band width in kHz. The bandwidth is normally specified at some level of attenuation say -0.5dB or -3dB etc. Variation within the Passband is specified in dB and is termed Ripple. This is defined as the maximum variation of output within the Passband at the specified bandwidth. Insertion loss is the relative loss in dB at the normal bandwidth, and is a function of the complexity of a filter. Specifying the Stopband BAND PASS FILTERS LINEAR PHASE CRYSTAL FILTERS 1.0MHz to 180.0MHz To avoid distortion and ringing due to group delay it is necessary to have a flat time-delay characteristic. The group delay of a highly selective filter varies considerably within the pass band. This introduces distortion into digital and low noise transmission signals. These problems can be overcome by specifying a Linear Phase Crystal Filter. SPECIALIST CRYSTAL FILTERS COMB FILTER BANKS 1.0MHz to 100.0MHz A comb filter bank is made up of a number of crystal filter elements which are used to divide a particular frequency spectrum into discrete elements. BAND-REJECT FILTERS 1.0MHz to 100.0MHz A band reject filter is a narrow band device which will reject a single frequency from a spectrum of frequencies It is necessary to specify the attenuation at a defined level of bandwidth (e.g ± 20kHz at -40dB) along with the maximum attenuation. It is also necessary to know input and output impedances. These are normally specified in terms of resistance and capacitance. e.g 1500W//2.0pF Phase response A filters phase response is the phase difference between the output sine voltage and the input sine voltage. Group delay Group delay is determined from the slope of the filter phase characteristic and is an indication of the time delay that occurs when a modulated signal passes through the filter. Packaging The filter assembly is available packaged in a wide range of different styles which can be chosen to suit customers requirements. Our design engineers will be pleased to advise on the most suitable package for any particular application. EUROQUARTZ 3 MADE-TO-ORDER CRYSTAL FILTERS FILTERS SPECIMEN FILTER DESIGN - 1 Crystal Filter 19.9750MHz This filter was designed and manufactured for a data transmission application where excellent Group Delay parameters were an essential part of the specification. General Specification Centre Frequency: Insertion Loss: Ripple: 0.5dB 1.0db Differential Delay: 12dB 25dB 30dB 45dB 45dB 70dB Ultimate Attenuation: Temperature Range: Terminations: Spurious: 19.9750MHz 2dB max. 0.5dB max. ±8.5kHz ±12kHz 5ms max. ±25kHz ±34kHz ±41.5kHz ±50kHz ±58.5kHz ±70kHz 55dB 0° to +55°C 50W 40dB min. Outline and Dimensions 35.8 14.8 6.0 Two 1.0 Seal Pins Two M3 Studs 22.86 15.24 7.62 26.5 Tel: +44(0)1460 230000 Fax: +44(0)1460 230001 Email: [email protected] Web: www.euroquartz.co.uk EUROQUARTZ 4 MADE-TO-ORDER CRYSTAL FILTERS FILTERS Tel: +44(0)1460 230000 Fax: +44(0)1460 230001 Email: [email protected] Web: www.euroquartz.co.uk SPECIMEN FILTER DESIGN - 2 Crystal Filter 19.850MHz This miniature discrete filter has been produced in a very small package. General Specification Centre Frequency: Insertion Loss: Ripple: 0.5dB 1.0db 25dB 45dB Ultimate Attenuation: Group Delay ±7.7kHz Impedance: Temperature Range: Shock: 19.850MHz 2dB max. 0.5dB max. ±7.7kHz ±12kHz ±22.3kHz ±30kHz max. 45dB 13ms p-p max. 50W 0° to +70°C 30g 11ms half sine Outline and Dimensions 27.5 to include Seal Pip 8.0 max. 20.0 Two off Pins 0.8 5.25 15.0 10.5 Two off Seal Pins 0.8mm 18.0 27.0 EUROQUARTZ 5 MADE-TO-ORDER CRYSTAL FILTERS FILTERS Tel: +44(0)1460 230000 Fax: +44(0)1460 230001 Email: [email protected] Web: www.euroquartz.co.uk SPECIMEN FILTER DESIGN - 3 8 Pole Wide Band Crystal Filter This wide band filter has been designed for satellite data monitoring. General Specification Centre Frequency: Insertion Loss: Ripple: Bandwidth 6dB: Bandwidth 60dB: Termination: Ultimate Attenuation: 21.40MHz 6dB max. 2dB max. ±60kHz ±160kHz 1.6kW//2.2pF 70dB Outline and Dimensions 26.5 max. Two Off Seal Pins 5.5 ±0.5 long 49.2 max. 14.3 Two Off M3 Studs 6.5 ±0.5 long EUROQUARTZ 6 MADE-TO-ORDER CRYSTAL FILTERS FILTERS SPECIMEN FILTER DESIGN - 4 174.0MHz Crystal Filter A high frequency filter in a small, low-profile package. General Specification Centre Frequency: Insertion Loss: Ripple: Bandwidth 3dB: 173.9375MHz 173.875MHz 174.00MHz 6dB max. 1dB max. ±40kHz nominal 30dB min. 45dB min. Outline and Dimensions 35.8 13.0 6.0 Two 1.0 Seal Pins Two M3 Studs 22.86 15.24 7.62 26.5 Tel: +44(0)1460 230000 Fax: +44(0)1460 230001 Email: [email protected] Web: www.euroquartz.co.uk