Microwave multiplexer having resonant circuits connected in series with comb-line bandpass filters

• US 4,091,344 A
• Filed: 01/19/1977
• Issued: 05/23/1978
• Est. Priority Date: 01/19/1977
• Status: Expired due to Term

• Current Assignee: Wavecom Industries
• Original Assignee: Wavecom Industries
• Inventors: LaTourrette, Peter Myers
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Barlow, Harry E.
• Application Number:
  US05/760,697
• Time in Patent Office: 489 Days
• Field of Search: 333/6, 333/8, 333/9, 333/73 C, 333/73 S
• US Class Current: 333/134
• CPC Class Codes: H01P 1/2136 using comb or interdigital filters; using cascaded coaxial cavities H01P1/2131, H01P1/2135 take precedence

Abstract

A microwave multiplexer having a plurality of comb-line filters tuned to pass distinct but adjacent frequency bands connected in parallel to a common input through individual resonant circuits having a minimum impedance at a frequency in the pass band of the associated comb-line filter.

Claims

1. In a microwave multiplexer having three or more comb-line filters with one end of each connected to a common junction, each filter passing distinct but adjacent portions of a microwave frequency spectrum, an improved coupling of said one end of each comb-line filter to said common junction wherein a resonant circuit is provided in series therebetween for at least one comb-line filter or filters having pass bands with frequency portions intermediate of the highest and lowest of said adjacent portions, each of said resonant circuits having a resonance frequency within a pass band of its associated comb-line filter.

2. The improved multiplexer according to claim 1 wherein the comb-line filter having a pass band corresponding to the lowest of said adjacent portions of the microwave frequency spectrum omits any series capacitance from its coupling between its said one end and said common junction, thereby omitting any series resonant circuit therefrom.

3. The improved multiplexer according to claim 1 wherein each comb-line filter with a frequency pass band portion greater than the lowest portion includes a series resonant circuit connected between the common junction and said one end of the filter and having resonance at a frequency within its pass band.

4. The improved multiplexer according to claim 1 wherein the comb-line filter having the highest pass band frequency portion has its said one end connected through a series capacitance to the common junction without providing resonance within that filter'"'"'s pass band.

5. The improved multiplexer according to claim 1 wherein the comb-line filters are characterized by passing said distinct adjacent portions of a microwave frequency spectrum at frequencies in excess of 100 MHz and with a ratio of the highest to lowest frequency passed by all of said three or more comb-line bandpass filters being greater than two.

6. The improved multiplexer according to claim 1 wherein said multiplexer omits any shunting elements external of the comb-line filter between the common junction and a common potential.

7. The improved multiplexer according to claim 1 wherein another end of each comb-line filter is connected directly to a separate terminal without any series capacitance therebetween.

8. In a microwave multiplexer having a plurality of comb-line bandpass filters connected with their inputs to receive a broad band signal at frequencies greater than 100 MHz from a common input, each filter passing substantially different but adjacent portions of a microwave spectrum presented at said common input, an improvement coupling the input of each comb-line filter to said common input wherein a series resonant circuit is provided between the common input and at least each of the comb-line filters having pass bands above the lowest of said pass band frequency portions, each of the resonant circuits having a minimum impedance at a frequency within the pass band of its associated comb-line filter and a high impedance within the pass bands of the other filters.

9. The improved multiplexer according to claim 8 wherein the comb-line filter having the lowest frequency portion pass band is connected to the common input without any series capacitance therebetween, thereby omitting any series resonant circuit therefrom.

10. A microwave frequency multiplexer, comprising:

a plurality of comb-line bandpass filters having adjacent microwave frequency pass bands extending over a composite spectrum that all lies at frequencies greater than, 100 MHz,

a common junction contact block,

a wire connected between a resonator at one end of each of the comb-line filters and said contact block, thereby introducing an inductive coupling between one end of each of said comb-line filters and the contact block, and

each of the wires leading to the comb-lines having pass bands exceeding the lowest pass band being connected to said block by insertion of an end thereof into a hold of said block in an electrically non-contacting relationship therewith, thereby forming a capacitive connection to the common junction block, said capacitive connections being made to the block for at least each of the comb-line filters having a pass band intermediate of the lowest and highest bands of said spectrum such that each capacitance forms with its associated inductance of the wire connection a resonant circuit having a minimum impedance at a frequency within the pass band of its associated comb-line filter and a high impedance within the pass bands of the other filters.

11. The multiplexer according to claim 10 wherein the connecting wire to the comb-line having the lowest pass band is solidly and electrically connected with said contact block in a non-capacitive manner.

12. A method of separating a microwave frequency spectrum over 100 MHz in frequency from a common signal source, comprising the steps of:

providing a plurality of comb-line filters each having adjacent microwave frequency pass bands that extend over portions of said microwave spectrum, and

passing said common signal from the common input through individual impedances to the inputs of each of the comb-line filters, including the step of passing the signal to each of the comb-line filters having pass bands in excess of the minimum bandpass frequencies through a series impedance that includes a resonant circuit having a resonant frequency within the pass band of the associated comb-line filter.

13. A microwave diplexer, comprising:

a common terminal,

a first comb-line microwave filter having a first defined microwave frequency pass band that lies entirely above 100 MHz,

a second comb-line microwave filter having a second defined microwave frequency pass band that is immediately adjacent to and higher in frequency than said first pass band,

a non-capacitive inductive coupling from said common terminal to a first resonant element of said first filter, and

a series capacitive coupling from said common terminal to a first resonant element of said second filter.